Marine gas engines, their construction and management

Jltl;aca. S^ew $otk

BOUGHT WITH THE INCOME OF THE

SAGE ENDOWMENT FUND

THE GIFT OF

HENRY W. SAGE

1891

CORNELL UNIVERStTY LIBRARY

3 1924 104 019 835

Cornell University
Library

The original of tliis book is in
tine Cornell University Library.

There are no known copyright restrictions in
the United States on the use of the text.

http://www.archive.org/details/cu31 9241 0401 9835

MARINE GAS ENGINES

MARINE GAS ENGINES

THEIR CONSTRUCTION
AND MANAGEMENT

BY

CARL H. CLARK, S.B.

102 ILLUSTRATIONS

SECOND EDITION

KEVISED AND ENLAB6EO

NEW YORK

D. VAN NOSTRAND COMPANY

25 Park Place

1919

s

Copyright 1911, 1919, by
D. Van Nostrand Company

The Plimplon Press Norwood Mass. U.S.A.

PREFACE TO FIRST EDITION

In presenting the following material the author has not attempted
to deal with the matter from a theoretical standpoint. The idea
is rather to describe the construction and principles of operation
of the standard types in a plain and simple and well-illustrated
form. It is hoped that it will be found to be adapted to those
desiring a systematic presentation of the principles of operation
and construction of modem marine gas engines.

Boston, November, 1910.

PREFACE TO SECOND EDITION

In making the modifications for this edition no alteration in the
governing principles would naturally be possible. Such changes
have been made in the application of the principles as were neces-
sary to bring the matter up to current practice. The material on
oil and Diesel engines has been added in accordance with recent
developments on these Unes.

Boston, Jidy, 1918.

CONTENTS

CHAPTER PAGE

I. Types of Engines i

Principles of operation of each type — advantages of each t3:pe.

II. Two-CvcLE Engines g

General construction — Description of some standard types
— Pumps.

III. Fous-Cycle Engines , . . 19

General construction — Description of standard types.

IV. Vaporizers and Carbureters 26

Vaporization of fuel — Principles of operation and description
of standard types.

V. Ignition Devices 35

Principles of ignition — Mechanisms of igniters — Timers —
Spark coils — Plugs — Batteries — Dynamos and Magnetos.

VI. Wiring 54

Diagrams for wiring — Spark coils — Distributor.

VII. Oil Engines 64

VIII. Lubrication 70

Methods of lubricating the several parts.

IX. Multiple-Cylinder Engines 76

Description and construction of standard types.

X. Reversing Mechanism 89

Reversing propeller — Reversing gears — Reversing engines.

XI. Propellers 98

Definitions — Efficiency — Measuring propellers — Calculations.

XII. Installation 103

Foundation — Piping — General considerations and description.

XIII. Operation and Care of Engines 113

General instructions — Hints on finding troubles — Care of
engine and outfit.

XIV. Power oe Engines 122

Horse-power — Formulas for power — Methods of finding
power — Brakes.

XV. Selecting an Engine 130

General considerations as to tjTJe, size, and construction.

V

MARINE GAS ENGINES

CHAPTER I

Types of Engines

The rapid development of the gas engine during the past few
years has made possible a great increase in the use of small units
of power for various purposes. This is shown by the increasing
use of the gas engine in automobiles, power-boats, and many
other places where compact powers are necessary.

The gas engine, for small powers particularly, has many ad-
vantages over the steam engine. It is self-contained, with no
cumbersome boiler, feed pumps, and piping. It is comparatively
light and easily installed. As there is no fuel to be handled it is
easily kept clean, and as the supply of fuel is nearly automatic,
it may be run with the minimum amount of care, and little labor
is required beyond the regulation of the lubrication and the fuel
supply. Properly installed and in good hands, the gas engine
may be nearly as reliable as the steam engine. The underlying
principle of the operation of any engine, whether gas or steam,
is the fact that a gas tends to expand when heat is applied to it,
and if allowed to do so has the power of doing work. Any gas or
vapor will absorb heat; during the process its tendency to expand
is increased, or in other words, the pressure is increased. If the
gas or vapor can then be confined, as in the cylinder of an engine,
and allowed to expand, it can be made to do work upon the piston.
In the steam engine the heat is appUed to the boiler, vaporizing
the water and raising the pressure of the vapor in the boiler.
The vapor is then carried to the boiler under pressure, and allowed
to expand in the cylinder, thus doing work on the piston. The
action of the steam engine is thus complicated by the boiler,
piping, and pumps, and the operation by the care necessary to
feed the fuel, and maintain the proper quantity of water in the
boiler.

MAEINE GAS ENGINES

The gas engine, whether operated on gasoline, alcohol, or kero-
sene, is of the type technically known as the internal combustion
engine. The name originates from the fact that the combustion
of the fuel and the consequent generation of heat take place
directly in the cyhnder of the engine, instead of in a separate
chamber, or boiler, as in the steam engine.

Gas engines for marine use may be practically divided into
two general classes, the two-cycle and the four-cycle. The cycle
of events is the same in both cases, but the means of accomplish-
ing it are quite different. In either type there are four operations
to be accomplished during each cycle, viz.: (i) Drawing in a
fresh charge of gas into the cylinder; (2) compressing and firing
the charge; (3) expansion of the ignited charge and the absorp-
tion of its energy; (4) expulsion of the burned and exhausted gases.
The completion of this series of events is termed a "cycle."

The "Two-cycle" Engine. — This type, being simpler of the two
types, will be described first. The general outline of a two-cycle
engine is shown in Fig. i, where C represents the cylinder; the
piston P moves freely up and down in the
cyUnder; the connecting rod R connects the
piston with the crank shaft 5. As the piston
moves up and down it imparts a rotary mo-
tion to the crank shaft by means of the con-
necting rod. The crank case B, or chamber
surrounding the crank, is made gas-tight.
An opening into the crank case is provided
with a check valve V, which allows gas to
enter the crank case, but not to pass out.
A transfer passage T leads from the base and
opens into the cyUnder at the inlet port I,
which is above the piston when the latter is
at the lowest point of its stroke, as in Fig. 3.
At E another port, called the exhaust port,
opens from the cylinder to the outside. The
exhaust port is somewhat higher up than the
inlet port. Both inlet and exhaust ports are covered by the piston
except when it is near the bottom of its stroke. The flywheel F is
provided in order to give a steady rotation.

For the operation, suppose tibe piston to be at the bottom of

Fig. I. — Outline of
Two-cycle Engine.

TYPES OF ENGINES

Fig. 2. — Two-cyde
Engine on Com-
pression Stroke.

its stroke, and to ascend, as in Fig. 2 ; this action will create a

partial vacuum or "suction" in the crank case and will draw in

a charge of explosive mixture through the check valve. When the

piston reaches the top of its stroke, the "suc-
tion " ceases, allowing the check valve V to seat,

confining the charge in the crank case. As the

piston again descends, the charge in the base,

being confined, is compressed in the base and

the transfer passage, the outlet of which is

closed by the piston, as in Fig. 4.

When the piston reaches nearly the bottom

of its stroke fit uncovers the inlet port I and

the charge from the crank case rushes in and

fills the cyUnder as in Fig. 3. Before, however,

any of the new charge can escape through the

exhaust port E which is also open, the piston

has begun its next upward stroke and cov-
ers both ports, so that the cylinder is now

filled with nearly fresh gas. As the up stroke

continues, the charge in the cylinder is com-
pressed into the space above the piston. When
the piston has reached the top of its stroke, the
compressed charge is ignited by some means,
producing a powerful impulse from the heat
generated by the combustion, which drives the
piston downwards, giving the power stroke. As
the piston nears the bottom of its stroke it un-
covers the exhaust port E, allowing the pressure
in the cylinder to drop and a part of the burned
gas to escape. A moment later in the stroke
the inlet port / is again uncovered and a fresh
charge is admitted from the crank case, which
drives out the most of the remaining burned
gases and fills the cylinder as before. This new

Fig. 3. — Two-cycle charge is then compressed on the next up stroke
lof^oFoas^'^™'^' and a new supply drawn into the crank case
and the operation continues.
Following through the sequence it will be seen that the cycle

is completed during every revolution, or for every two strokes.

MAMNE GAS ENGINES

For this reason it is called the two-stroke cycle, or, as commonly
stated, the " two-cycle." This cycle has a working or power stroke
during each revolution. The momentum of the
fljnvheel is depended upon to carry the piston
up during the compressive stroke.

The projection D on the top of the piston
is a deflector, or shield, in front of the inlet
port to deflect the incoming gas upwards, which
not only produces a scouring action, but pre-
vents the new charge from rushing directly
across the cylinder and out through the exhaust
port. The exhaust port is usuallj* opposite and
is somewhat higher up than the inlet port, in
order that the pressure may be reduced and the
burned gases partially escape before the fresh
charge is admitted. If this were not done, the
temperature in the cyUnder would be so great
that the incoming charge would be fired pre-
The relative position and size of the inlet and exhaust

The pis-

FiG. 4. — Two-cycle
Engine at Exhaust.

maturely,

ports is the key to the success of the two-cycle engine.

ton, in this type of engine, acts as its own valve, so that the

engine, from its very principle, is valveless.

"Three-port" Engines. — A variation of the two-cycle engine,
known as the "three-port" engine, is illustrated in Fig. 5. Aside
from the means of admitting the vapor, the gen-
eral characteristics and operation are the same as
the usual two-cycle type. Instead of admitting
the vapor to the crank case through the check
valve, a third port K is provided, which is cov-
ered by the piston except when it is at the top of
its stroke, as in Fig. 5, at which time this port is
open into the space below the piston. The piston
on its up stroke creates a partial vacuum in the
crank case, and when the third port is uncovered
at the top of the stroke, the vapor rushes in. The
vapor is thus admitted in a sort of puff, instead
of during the entire up stroke as in the two-port
type. The action is therefore more energetic and j-jg_ j_ "Three-
positive at high speeds. As the piston covers the port" Engine.

TYPES OF ENGINES

Fig. 6. — Four-cycle
Engine on Admis-
sion Stroke.

admission port except during the admission, a check valve on the
vapor inlet is unnecessary, and the admission
of the vapor is less obstructed.

The action of the check valve on the two-
port engine becomes somewhat uncertain at
high speeds, as it does not have time to seat
squarely between the strokes, so that some of
the vapor is likely to be blown back around
it instead of being confined in the base. For
these reasons the three-port engine can prob-
ably be run at a higher rate of speed, and this
type is usually adopted for light high-speed
engines. There are one or two makes of en-
gines which have both the check valve and
the third port, which, it is claimed, have all
the advantages of each type.

The Four-cycle Engine. — In this tj^e of
engine the admission and exhaust of the gases
are controlled by mechanical means. In Fig. 7, / is the inlet
valve opening from the admission chamber into the cylinder, and
E is the exhaust valve opening from the cylinder into the exhaust
chamber. These valves are controlled by gears from the engine
shaft. The other parts of the engine are substantially the same
as the two-cycle engine, except that the crank
case does not require to be gas-tight.

For the operation, suppose the piston to be
moving downwards, as in Fig. 6; the inlet valve
/ is open and the suction draws in a charge of
fresh gas, filUng the cylinder. On the piston
reaching the bottom of its stroke, the inlet
valve closes, confining the charge in the cyhn-
der. On the next upward stroke, shown by
Fig. 7, both inlet and exhaust valves remain
closed, and the charge is compressed into the
space above the piston. When the piston
reaches the top of its stroke the compressed
Fig 7— Fourcycle ^"^^^^^ '^^ ignited, expanding and driving the
Engine on Com- piston down, as in Fig. 8; both valves remain-
pression Stroke, ing closed. This gives the impulse or power

MARINE GAS ENGINES

Fig. 8. — Four-cycle
Engine on Power
Stroke.

stroke. During the next up stroke the exhaust valve E opens, and
the burned gases are forced out by the piston
through the exhaust port, as in Fig. 9. The
cyhnder is now clear and ready for the adihis-
sion of a fresh charge through the inlet valve
on the next downward stroke of the piston.

This cycle is completed in two revolutions,
or four strokes, and is therefore called the
four-stroke cycle, or "four-cycle." There are
three idle strokes and one working or power
stroke during each cycle, thus giving a power
stroke for each alternate revolution. The fly-
wheel must be heavy enough to carry the pis-
ton through the three idle strokes.

Advantages of Each Type. — The two-cycle
engine has Uie advantage of extreme simplicity,
owing to the absence of valves or other ex-
ternal moving parts which would be likely to

need adjustment and care. As the piston receives an impulse during

each revolution, more power may be obtained from the same size

cylinder than in the four-cycle type. It might seem that, since

the two-cycle engine receives twice as many

impulses as the four-cycle, twice the power

should be obtained, but this is not so, as owing

to the superior regulation of the four-cycle type

the difference is much less. The more fre-
quent occurrence of the impulses does, how-
ever, allow the use of a lighter flywheel and

produces a smoother running engine with less

vibration.

The valveless feature of the two-cycle type,

while giving simplicity, at the same time gives.

rise to some uncertainties and irregularities in

the action of the engine. The action of the

gas in the cyhnder is somewhat uncertain; it

is hardly to be expected that the inflow of gas

will continue exactly long enough to fill the

cylinder and no more; it is entirely possible

Fig. 9. — Four-cycle
Engine on Exhaust
Stroke.

either that some of the exhaust may not have time to escape, or

TYPES OF ENGINES 7

that some of the fresh charge may pass over and out through the
exhaust. Again, it is hardly possible for the incoming gas to
entirely scour the upper parts of the cyHnder, and some waste
gas is sure to be caught, thus diluting the new charge. The
driving out of the burned gas by the fresh mixture while some
combustion may be still going on frequently results in the pre-
mature ignition of the new charge, the flame following down the
transfer passage and igniting the reserve in the base. This pro-
duces a back explosion, causing an irregular action and even stop-
ping the engine.

There are also some disadvantages which may be termed struc-
tural. While the working parts are very simple, they are entirely
enclosed and not easily examined and adjusted. As the crank
case for the usual t3^e requires to be jgas-tight, any leakage around
crank-shaft bearings from natural wear causes a loss of crank-
case pressure, and consequent loss of power. Any leak around
the piston will allow the partially burned gases to pass down and
deteriorate the quaHty of the fresh gas in the crank case. The
lubrication of the parts in the closed crank case, which are exposed
to the direct action of the fuel gas, is sometimes diflScult, and the
wear on these parts is consequently greater.

While there are two-cycle engines in which the enclosed crank
case is dispensed with, an additional compression chamber must be
provided, which adds comphcation and robs the engine of much
of its simplicity.

The four-cycle type, although more complicated, is surer
and more certain in its action, as the behavior of the gas is
mechanically controlled. The idle stroke allows the cylinder a
short time to cool between explosions. On account of the
mechanical regulation there is less chance for waste of fuel and
the economy is therefore greater than that of the two-cycle. As
the flow of gas in the cylinder continues throughout the stroke,
instead of in a sudden puff, the four-cycle engine may be run eco-
nomically at a higher rate of revolution. No enclosed crank case
is necessary and the working parts can be easily lubricated and
taken care of.

On the other hand, the three idle strokes require a very heavy
flywheel, and as the impulse occurs only on alternate strokes,
the four-cycle engine must, for the same power, be larger and

8 MARINE GAS ENGINES

heavier than the two-cycle. Each impulse, or explosion, is much
heavier than that in the two-cycle, and the tendency to vibration
is consequently much greater.

While the two-cycle engine has some theoretical disadvan-
tages, it practically has reached a high state of perfection, both
as to reliability and economy, although in the latter respect it is
probably not the equal of the four-cycle.

It may be stated as a general conclusion that for small, light
engines where economy is not of great importance, and which
receive little attention, the two-cycle type is to be preferred.
For single-cyUnder engines the two-cycle type is decidedly to be
preferred, on account of the excessive vibration of the single-
cylinder engine of the four-cycle type. For engines of large size,
where fuel economy becomes of importance, together with increased
reliability, the four-cycle type is probably preferable.

CHAPTER II

Two-Cycle Engines

Two-cycle engines seem to divide themselves into two more
or less distinct classes, as shown in section by Figs. lo and ii.
The former type is of low rotative speed, moderate to heavy weight,
, and is generally fitted with the make-and-break spark mechanism.
The latter is of the high-speed type, of moderate to Ught weight,
generally fitted with the jump spark and is commonly of the three-
port tj^e.

The heavier type of engine is shown somewhat in detail in
Fig. lo. The piston P is shown at its lowest position, its highest
point being just above the

line c. Above the line c _t ,"L t

the bore of the cyUnder is
slightly enlarged; this is
called the counterbore, and
is for the purpose of allow-
ing the piston to overrun
the edge of the working
part of the cylinder bore
and prevent a shoulder be-
ing formed at the upper end
of the stroke as the bore
wears. Unlike a steam en-
gine, the piston does not
travel to the top of the
cylinder, but a considerable
space, or compression cham-
ber, is left to contain the gas
compressed to the proper
volume for ignition.

The cylinder is sur-
rounded by the water jacket

Fig. 10. — Two-cycle Engine.

/, through which water is circulated to cariy ofE the excess heat

9

10 MARINE GAS ENGINES

which is generated in the cylinder, and which if not carried away
would cause the cylinder and other parts to become overheated
and perhaps damaged. The cyUnder head H, which is also hollow
for water circulation, is held in place by several bolts or studs
b, b. The joint between the cylinder and head is filled with a thin
sheet of packing to make it gas-tight. The water enters the jacket
at w, circulates around the cyUnder and through the head and
passes out at j. The water may pass from the cylinder jacket to
the head either through an outside pipe as shown, or through an
opening directly upwards between the studs. The former method
is preferable as, when the opening is cut in the packing, there is
a chance for a leakage of water into the cyUnder. In order to
make the piston P gas-tight, it is provided with spring-packing
rings as shown, usually three in niunber, which are set into grooves
turned in the piston. They are turned to a diameter sUghtly
larger than the bore of the cyUnder and are sprung in, so that
they press out against the walls of the cyUnder and prevent leak-
age past the piston. The piston itself is a rather loose fit in the
cylinder. Two of the rings are placed at the top of the piston
and the other at the lower edge. This is to prevent leakage from
one port to another. For example, when the piston is part way
down, the gas in the base might be forced past the piston and out
the exhaust port, were it not for this lowest ring. The joints on
the rings are shown halved, which is much preferable to cutting
them across at an angle as is sometimes done, as there is less
chance for leakage when cut in this way. Piston and rings are
of cast iron.

The piston or wrist pin W is a. steel pin upon which the con-
necting rod R swings. It is held from turning by a set screw either
in the piston or the top of the connecting rod.

The connecting rod R may be either of steel or bronze; the
upper end of the rod consists simply of an eye, through which
the wrist pin is inserted; the lower or crank-pin end is parted, and
the under part fastened on with two or more bolts; this is neces-
sary in order to get it into place and to allow the taking up of the
wear. When the rod is of bronze, as is usually the case in small
engines, the bearings are turned directly in the metal of the rod;
when, however, a steel rod is used, either babbit or composition
bearing surfaces must be inserted.

TWO-CYCLE ENGINES II

The crank shaft 5, 5 should be made from the best of steel
as it is subjected to great stress. It turns in bearings in the base,
which are lined either with composition sleeves B, B, or babbit
which is run into grooves provided for it. These sleeves or linings
not only make a smooth bearing for the shaft, but allow the
insertion of new ones when wear has taken place. On the end of
the crank shaft is the iiywheel F, of cast iron. It is held in place
by a key K which is of rectangular section and is sunk half in the
shaft and half in the flywheel hub. The handle h, for use in
starting the engine, is contained in a hole in the rim of the
fljnvheel, and is pulled out for use. It is encircled by a coiled
spring which draws it in when released, preventing injury to
the operator.

The pump Q, for circulating water through the jackets, is of
the plunger type; it consists of the plimger Z, working in the barrel.
This plunger is made water-tight at the upper end of the barrel
by the packing gland as shown, and at the lower end are the usual
two foot valves. The water is drawn in through one valve on
the upward stroke and forced out through the other on the down-
ward stroke, each valve allowing the Water to pass in one direc-
tion only. The pump is operated by the eccentric N on the
crank shaft, and the eccentric strap M.

The thrust bearing A takes up the forward pressure of the
propeller and prevents the crank shaft being forced against the
bearings by the pressure. It consists practically of two hardened-
steel rings with steel balls rimning between them.

The igniter mechanism I is operated by an extension of the
pump rod. At D is a drain cock to allow the water to be drained
from the jacket in cold weather, as the freezing of water in the
jacket would be Ukely to spUt the casting. At C is an opening
from the cylinder, which is fitted with a pet-cock, for the purpose
of relieving the compression when turning the engine over by
hand.

An oil-cup O feeds oil into the bore of the cylinder, lubricating
the piston and rings. A grease-cup G, G lubricates each crank-
shaft bearing.

The coupling X allows the attachment of the propeller shaft;
it is a sleeve of cast iron held on the shaft by set screws or keys.

In Fig. II is shown the general outliiae of the high-speed,

12

MARINE GAS ENGINES

three-port type. The general characteristics are the same as the
previous example, but some details are different. In this case
the Cylinder and head are cast together, thus simplifying the water
circulation; the joint between the cylinder and base castings
being on the line of the center of the shaft. The pump is con-
nected directly to the cyUnder,
the water passing through the
stem; the outlet for the cooling
water is at j. At G, G is a pair
of bevel gears, one of whicJi is
fast on the crank shaft; the
other is on the vertical shaft
and drives the timer T. The
spark plug is inserted at P.

The transfer passage and the
exhaust port E are the same
as before. The inlet port / is
shown dotted on the farther
side of the cylinder. The other
inlet at V on the base is used in
the two-port engine. Some few
engines are fitted with both
openings, allowing them to be
used either two or three port as
desired. This engine is arranged
for jump-spark ignition, so that

; ^'Atc4|

Fig. II. — Two-cycle Engine.

no igniter gear is shown, the spark plug P screwing into the head
of the cylinder.

The several parts will not of course always be arranged in
just the above relations; the transfer passage T is very often
placed on one side, with the exhaust on the opposite side; the water
pump may be placed either front or rear of the cyhnder. Any
of the several types of pumps later described may be used; the
plunger pump may be placed horizontal and piped to the cylin-
der; in the case of the rotary or gear pimip it may be driven by
gears or sprocket chain. In at least one make of engine the gear
pump is driven directly from the timer shaft.

Figs. 12, 13, and 14 show the outlines of three styles of stand-
ard makes of engines. In Fig. 12 the cylinder and upper part

TWO-CYCLE ENGINES

13

of the base are cast together; the lower part of the base being a
separate casting joined to the upper base at the line of the shaft;
the cylinder cover also is separate. The several parts are lettered
the same as in the preceding cuts. In the medium and large
sizes a hand-hole plate h allows access to the base for cleaning
or adjustment. An opening in this plate is threaded for attach-
ment of the vaporizer V. The exhaust pipe connection is on the
rear of the engine at E. The water pump is just back of the fly-

FiG. 12. — Two-cycle Engine. Fig". 13. — Two-cycle Engine, Heavy Type.

wheel and delivers the water to the jacket through the pipe W;
the water discharges from the jacket at /. At i^ is a small oil-
cup and cock for admitting oil to the base. The igniting gear
is at I. In this type the sleeves for the crank-shaft bearings are
held by being clamped between the upper and lower base cast-
ings. The engine is bolted to the bed by the flanges X.

In Fig. 13 an engine of somewhat similar type is shown, except
that the cylinder and base are in one casting, and the shaft bear-
ings are carried in plates bolted on front and rear of the base
casting. This is a very strong construction, its only disadvan-

14

MAEINE GAS ENGINES

tage being that in the event of damage to the cylinder the entire
engine must be taken down. Access is given to the base through
the hand-hole plate E, and an additional plate h on the bottom
is placed there for constructive purposes principally. The trans-
fer passage is on the side, as shown by Uie raised portion at T;
the exhaust is on the opposite side at E. The oU-cup on the front
of the engine is for the purpose of oiling the crank pin through
a ring oiler, while the oil-cup is the usual cylinder oil-cup.

Fig. 14 shows a high-speed, three-port engine similar to Fig.
11; in this case the cylinder, which has a soUd head, is joined to

the upper base casting by the flange
at F. The upper and lower base cast-
ings are joined at the shaft line by
the flanges at /. The inlet I, in-
stead of being on the base, is higher
up on the cyUnder. This type of con-
struction is very desirable on account
of the comparative ease with which
it may be overhauled; the cyUnder
may be removed without disturbing
the working parts of the engine.
Other parts are lettered the same as
before. In some engines of this tyf»e
the flange F is omitted and the cylin-
. der casting is carried down to the

I base as in Fig. 12; this construction,

however, makes overhauling rather
difficult, as removing the cylinder
practically knocks down the entire
engine. On the larger sizes a hand-hole cover H gives access to
the base.

Engines with Separate Compression Chamber. — There have
been many attempts to overcome the disadvantages of the enclosed
crank case necessitated by the usual two-cycle engine. This may
be accompUshed by performing the initial compression in some
chamber other than the crank case. Fig. 15 represents one design
for accomplishing this purpose. The piston is provided with a
piston rod C which passes through a stuffing box B and connects
with the crosshead K below. The crosshead K runs in guides,

Fig. 14. — Light Two-cycle
Engine.

TWO-CYCLE ENGINES

IS

and carries the wrist-pin bearing for the connecting rod R. Sur-
rounding the cyUnder is the annular space ^,

which is connected with the space below the

piston by the small ports T. The inlet port

to the cyUnder is at I and the exhaust port

is at E. At F is a check valve in connection

with the annular space A. As the space

below the piston is made gas-tight by the

stuffing box B, this space, together with the

annular space A, fulfils the same purpose

as the crank case of the ordinary engine.

When the piston ascends a charge is drawn

in through the check valve V to the chamber

A, filling it and the space below the piston.

On the next downward stroke the charge is

compressed, and then passes into the cylin-
der through the inlet port / which is un-
covered by the piston. The operation is

thus the same as the ordinary two-port

engine. As no enclosed crank case is neces-
sary, good lubrication
may be had, and the
charge entering the cylinder will be clean
and free from oil. On the other hand there
are many more parts than in the ordinary
engine, and the engine must be considerably
higher above the shaft center.

Oil Engine. — In Fig. i6 is shown a
section of an oil engine operating on the
two-cycle principle. Its form is similar to
the usual two-cycle engine, with the excep-
tion, however, that no fuel is admitted to
the base. Pure air is admitted through the
third port /, compressed in the base, and
forced through the transfer passage into
the cylinder, where it is compressed. The
hollow ball B is kept hot by the succes-
sive explosions and the heat generated

during compression. At the proper time a small amount of oil is

Fig. 1$. — Two-cycle
Engine with Separate
Compression Cham-
ber.

Fig. i6. — Oil Engine.

i6

MAHnSTE GAS ENGINES

injected into the cylinder through the pipe 0. This oil strikes
the hot plate at the opening to the ball and is at once vaporized
and burned.

The oil is fed by the pump P, which is operated by a side shaft
somewhat similar to a cam shaft. This pmnp has an attach-
ment for varying the stroke and consequently the amount of
fuel fed, by which means the speed is regulated. The lamp L
is arranged for heating the ball B for startmg. This engine uses
the igniter described in Fig. 53. Engines operating on this prin-
ciple are described more in detail in tibe chapter on Oil Engines.

In another type operating on the two-cycle principle, each
cylinder has a separate jacket surrounding the hot exhaust pipe,

Fig. 17. — Plunger Piunp.

Fig. 18. — Eccentric Pump.

and communicating with the cylinder through a third port. This
jacket is connected to a pressure tank holding the oil. The engine
is started on gasoline and run until the exhaust pipe is well heated,
when the kerosene is turned on. On striking the hot surface,
the kerosene is at once vaporized and admitted to the cylinder
through the third port. The gasoUne is then cut o2 and the motor
runs on kerosene, the air necessary for combustion entering through
the usual check valve and being forced into the cylinder by the
base compression.

Pumps. — The water pump may be one of several styles;
the most common is perhaps the plunger pump shown in Fig. 17.
The suction valve S lifts on the up stroke of the plunger P, allow-
ing the barrel to fill. On the down stroke of the plunger the
valve 5 seats and closes the inlet, while the discharge valve D

TWO-CYCLE ENGINES

17

opens and allows the water to discharge. This fonn of pump is
on many accomits the best for use in connection with gas-engine
work, especially where there may be some sand or grit in the water.
It is easily kept in good condition and is very reUable. This form
is the best where the water has to be Ufted. It may be made in
either vertical or horizontal form; the valves 5 and D must,
however, have a vertical movement. In the pump, as shown in
Fig. II, the valve D may be in the form of a metal ball placed at
the top of the vertical barrel.

The eccentric piunp, shown in Fig. 18, consists of a circular
outer shell containing the revolving hub H, which is set eccen-

FiG. 19. — Gear Pump.

Fig. 20. — Centrifugal Pump.

trically; the hub H carries the two blades B, which are set out by
the springs between so as to be always in contact with the inner
circumference of the shell. As the hub H revolves the blades are
carried aroxmd, drawing in the water through the suction opening
S and discharging it through the opening D.

This form of ptmip, while it works well when new, has not a
long life as the friction of the blades B against the side plates
soon causes leakage, especially when the water contains grit.

When this pump is used it is run by a pair of gears or a bicycle
chain. There may be either two, three, or four blades.

The gear piunp illustrated in Fig. 19 consists of a pair of gears
meshing together and fitting closely inside the casing. The gears
are driven by one of the shafts, which extends through the side

1 8 MARINE GAS ENGHSTES

of the casing for that purpose. As the gears revolve in the direc-
tion of the arrows, the water which enters at S is caught in the
spaces between the teeth and the casing and carried around the
gears and discharged at the opening D. It should be noted that
the water does not pass between the gears, but around the out-
side.

This form, while more durable than the preceding, is subject
to some wear and wiU finally leak.

In Fig. 20 is shown the "centrifugal" pump; the rotator or
impeller R has vanes curved somewhat as shown and revolves in
the direction of the arrow. The water enters through the opening
S along the shaft. The rapid rotation of the impeUer rotates the
water and also throws it outward by the action of centrifugal
force so that the water is accumulated at the circumference and
discharged from the opening D.

This form of pump is probably the best of the rotary forms,
as it is not dependent upon the fit of the impeller between the
side plates. For water containing grit it is well suited. It has
a longer Ufe than either of the two previous forms. The relative
direction of rotation of the impeller should be noted; it must be
such that the water is thrown outward by the centrifugal force
and the curved blades, and finds its way around the diverging
periphery until it reaches the discharge opening D.

CHAPTER III

Four-Cycle Engines

Fig. 21 shows a section of a common type of four-cycle engine.
The working parts are similar to those of the two-cycle type, but

are complicated by the addition of
the valves and the means for oper-
ating them. The inlet valve / and
the exhaust valve E open into small
chambers connecting with the cyl-
inder. The valves / and E have
stems passing down through the
casing to a point just above the
cam shafts A and B; the lower end
is squared to form a guide and is
fitted with a roller R, to reduce
friction. The square guiding piece
is usually made separate, with the
stem resting upon it, in order to
allow the valve and stem to be
readily removed without disturb-
ing the guide and roller. The coiled
springs 5, 5 return the valves when
they are raised by the cams. The
cam shafts, or, as they are often
called, the "half-time" shafts A
and B, are driven from the crank
Since each valve only opens once for

Fig. 21. — Outline of Four-cycle
Engine.

shaft by the gears L, M,N.

each two revolutions of the engine, the two cam shafts must
revolve only one-half as fast as the main shaft; for this reason
the gears N and M are twice as large as L. The cams are so
placed on their shafts as to strike the roller R and raise the valve
at the proper time.

The cylinder and head are surrounded by the water jacket J, J.
Just above the valves are plugs, either bolted or threaded in

19

20

MARINE GAS ENGINES

place, which, when removed, allow the examination or removal
of the valves. The carbureter is attached at F and the exhaust
pipe at X.

The base in this t3TJe of engine is made of ample size and
comparatively easy of access, as size is of Uttle consequence.
The sides of the base are usually covered by plates to keep out
dirt and prevent the splashing of oil; these plates are usually
easily removed, exposing the entire contents of the base for adjust-
ment or examination.

A spark plug is shown at P, and the engine is also provided
with the usual lubricators, compression and drain cocks already
noted. The devices for regulating the electric spark and the
water pump are also driven from one of the cam shafts. The
valves may be on opposite sides of the cylinder as shown, or may
be placed side by side on the same side of the cyUnder, in which
case they may be operated by the same cam shaft.

Referring back to Fig. 6, it is plain that the suction of the
piston on its down stroke will tend to raise the inlet valve and
draw in a charge. It is thus possible to dispense with the cam
and gear on the inlet valve and
allow it to be operated by the suc-
tion of the piston. The exhaust
valve, however, must always be
mechanically operated as it has to
be lifted against the pressure in the
cylinder. When the automatic in-
let valve is used the arrangement is
as in Fig. 22, the inlet valve / being
inverted and directly above the ex-
haust valve E; the inlet valve / is
held in place by the coiled spring 5.
This illustration shows a common
arrangement for a single-cylinder
engine. The half-time gears are
inside the base, the cam F being
driven by the gear G through the
short shaft A; on the end of the
valve stem is the roller R, bearing
on and lifted by the cam F. In order to allow access to the

Fig. 22. — Diagram of Four-cycle
Engine.

rOtTR-CYCLE GAS ENGINES

21

valves the part containing the inlet valve is made removable,
making both valves accessible.

The flywheel, crank shaft, and other working parts are similar
to those of the two-cycle engine. The igniter gear iV^, N is oper-
ated from the cam shaft. At P is the cooUng water pimip and
eccentric. The ball-thrust bearing is at T, and at K is the coup-
ling, which is of the flanged type. The propeller shaft has a
similar flange, and the two are held together by bolts through the
flanges. This is a much stronger coupling than the sleeve coup-
ling, before described. The cylinder is surroimded by the water
jacket / and has the usual compression cock and oil-cup.

The cylinder, valve chest, and base are a single casting, the
head being bolted on and the shaft bearings being contained in
separate flanged castings, bolted to the sides of tiie base. The
gears G, G, being inside the base, are well lubricated by the splash-
ing of the oil in the base.

In Fig. 23 is shown a representative single-cylinder motor;
the valve chest is on the front of the cylinder and the exhaust
valve is operated by the gears G, G, shown just back of the fly-
wheel. The inlet valve is just be-
low the spring S in the removable
cap, and is automatic. The entire
cover is also removable. This par-
ticular engine has a frame open at
the ends which allows the main
bearings to be fitted with oil-cups
O; this form of base makes all
bearings accessible.

The water pump P discharges
into the jacket through the pipe W,
the outlet from the jacket being on
the opposite side of the valve chest.
At F is a special vaporizer. The
exhaust is at E. The igniter gear
N is operated from the cam shaft.

In this engine the cylinder, base,
and bolting flanges are one casting;
the upper half of the main bearing
the insertion of the shaft. The

Fig.

23. — Heavy Type, Four-
cycle Engine.

boxes being removable for

22

MARINE GAS ENGINES

cover and valve chest also are a single casting bolted to the
cylinder.

In Fig. 24 another style is shown, the valves and valve gear
being on the side of the cylinder. The edge of the cam-shaft
gear can just be seen behind the fljrwheel; the cam shaft and cam
are contained in the casting X which is bolted to the side of the
base. The automatic inlet valve is contained in the removable
bonnet I, the outside pipe leading down with an elbow at V, where
the carbureter or vaporizer is attached. The exhaust is at E.

Fig. 24. — Single-cylinder Four-
cycle Engine.

Fig. 25. — Light Four-cyde
Engine.

The water pump is on the rear of the engine, the cooling water
discharging at J. At P is a spark plug for jump spark ignition.
The compression or priming cock, C, has a sort of tunnel-shaped
opening to allow a small amount of gasoline to be run into the
cyUnder to facilitate starting. Cylinder, head, and valve chest are
in one casting, which is bolted to the upper part of the base. Side
plates X on the base give access to the interior.

Fig. 25 shows a light, high-speed engine; the valves are on
the back of the cylinder and the gears are inside the base. The
carbureter is attached to a pipe leading to the elbow A which

FOUR-CYCLE GAS ENGESTES 23

contains the automatic inlet valve. The timer T for the ignition
is on the end of the cam shaft, and the spark plug is at P. At C
is the priming cock and R the rehef or compression cock. The
base is in two parts, spUt on the hne of the shaft; the cylinder,
head, and valve chests are a single casting bolted to the upper base.
No side plates are fitted in this engine, as the base is kept tight to
allow of oiling by splash.

Single-cylinder engines are almost entirely built with the
automatic inlet valve. With two or more cylinders, however,
both automatic and mechanically controlled inlet valves are
used. There seems to be no particular rule governing the use
of either; it may be said, however, that while the automatic
inlet works well on slow-turning engines, as the speed increases
it is liable to become uncertain and irregular in its action. For
high-speed engines the mechanically controlled inlet valve is
much to be preferred.

Arrangement of Valves. — While there is no special rule as to
the arrangement of the valves, certain systems have come to be
accepted as good practice. The more conmion forms are shown
in Fig. 26. In the "L" bead type A the two valves are located
in a pocket at one side of the cylinder, being placed either side
by side, or one above the other. In this type both valves are
driven from a single cam shaft, which is naturally the simplest
and cheapest arrangement. The size of the valves, and conse-
quently the port areas are Umited by structural considerations, as
the length of the pocket can be little, if any, longer than the
diameter of the cylmder. This arrangement is therefore likely to
be used on the slower turning types of engines where the speed
of the gases is moderate.

When the two valves are on opposite sides of the cylinder as
in B, we have the "T" bead t)^e. As only one valve must be
accommodated on each side, the diameters of the valves can be
as large as desired. This arrangement is suitable for quick turn-
ing engines where the valve areas must be large to allow the gases
to flow rapidly. Two cam shafts must be used, but inasmuch as
it is becoming increasingly common to fit a magneto, generator,
or starting motor, the additional cam shaft is made use of for
driving these instruments.

Another very satisfactory arrangement of valves, termed the

24

MARINE GAS ENGINES

"valve in the bead" 1)^6 C is also shown. The valves are placed
in the head of the cylinder, opening directly into it. As shown at
the left, the two valves are placed side by side in a longitudinal
direction and are actuated by rocker arms, wMch are in turn
operated by rods leading down to the valve lifters.

U HCAO.

T HCAO.

Vauve in. head.

Fig. 26. — Types of Valve Arrangements.

This arrangement allows a very direct passage of the gases to
and from the cylinder, also permitting a very simple cylinder
casting, which is readily molded and machined, and easily kept
cool. The valves are carried in cages C which are inserted into
the bead and connect with the inlet or exhaust port P. Only one
cam shaft is required. While the size of the valves is limited by

FOUR-CYCLE ENGINES 25

the cylinder diameter, the direct passage for the gases seems to
offset any deficiency from this cause.

Another arrangement of the valves in the head is shown at D:
in this case the valves move horizontally and are actuated by the
long vertical rocker arms R, R pivoted on the sides of the cylinders,
the lower ends of which carry rollers bearing on the cams. Two
cam shafts are used. This arrangement allows a very small com-
pression space where a high compression is desired, and is used
on some special types of engines.

CHAPTER IV

Vaporizers and Carbureters

Before the fuel can be used in the cyUnder of the engine it
must be converted into vapor and mixed with the proper pro-
portion of air to form an explosive mixture. The principle of
the 9peration of both vaporizers and carbureters is the picking
up of the fuel in a finely divided state by a ciurrent of air. In
practice the fuel is made to flow from a small orifice directly into
the current of air which is drawn in by the suction stroke of the
engine. Means must, of course, be provided for regulating the
relative proportions of fuel and air, as the proper mixture is much
more effective and economical than one which is either too weak
or too rich. All carbureters or vaporizers to properly perform
their duties must have means for regulating the air and fuel
supplies. The simplest form of vaporizer, or mixing valve, as it is
sometimes termed, is shown in diagram in Fig. 27. It consists of a
circular brass casting, containing
the lifting valve V and its seat,
and the openings A and /. It is
attached to the crank case of the~
engine by the threaded end /. The
fuel enters at F, flowing around
the needle valve N and into the
small opening at 0, which is cov-
ered by the valve V. The valve
V has a stem extending upward and fitting into the guide in the
cover C; this stem makes the valve lift squarely and assures
its seating correctly after being raised. The spring S is added
to return the valve to its seat quickly. The needle point N may
be turned in or out by means of the thread T and the thumb
nut W, thus regulating the flow of fuel. It should be noted that
the valve V, when seated, covers the opening O, thus preventing
the escape of the fuel.

This form of vaporizer is most commonly fitted to two-cyde,

26

Fig. 27. — Simple Vaporizer.

VAPORIZERS AND CARBURETERS

27

two-port engines, for use with gasoline. The suction created in
the crank case by the upward stroke of the piston causes the
valve V to lift and the air to rush in through the opening A. The
raising of the valve V uncovers the opening O and allows the fuel to
flow out into the current of air, winch at once absorbs it. The
mixture passes into the crank case and is ready for use. When
the piston reaches the top of its stroke the suction ceases and the
valve V returns to its seat, aided by the pressure of the spring
S, cutting o£E the fuel and preventing the escape of the mixture
on the downward compression stroke. This valve V is the check
valve referred to in Chapter I.

This type of vaporizer, having no means for adjusting the air
supply, is not very sensitive. While owing to its simplicity it
is well suited to small engines, it is not sufficiently sensitive for
engines of the larger sizes.

A more approved type of mixing valve is shown in Fig. 28, Its
main features are the same as of that just described, but in addi-
tion it has the thumb wheel
R, the threaded stem of which
screws down on to the top of
the stem of the valve V and
thus regulates its lift. It also
has a throttle valve T, which
consists of a disc which may
be turned so as to partially or
wholly close the passage.

The proportions of the mix-
ture may be varied thus: the
fuel supply may be varied by the needle point N and the thumb
wheel W, giving a weaker or richer mixture. The air supply is regu-
lated by the thumb screw R; as the latter is screwed down the lift
of the valve, and consequently the air supply, is decreased. These
two adjustments allow the regulation to suit the varying con-
ditions under which the engine is run. \ The speed of the engine
is regulated by turning the throttle T more or less, thus varying
the amovmt of mixture passing through without varying its pro-
portions. The same result can of course be obtained by manipu-
lating the screws R and W, but in adjusting them for any
particular speed the best proportions of the mixture may be

Fig. 28. — Vaporizer.

28

MAIUNE GAS ENGINES

lost and a readjustment required for ordinary running. The cap
C is threaded to allow access to the interior.

Vaporizers of this type are suited to engines of the two-cycle,
two-port type, which require a check valve on the crank case.
For three-port and four-cycle engines some form of float-feed
carbureter may be used to advantage. While there is no differ-
ence between the functions of vaporizers and carbureters, those
just described are commonly called vaporizers, or mixing valves,
while those governed by a float and having no check valve are
usually called carbureters.

In Fig. 29 is shown a diagram of a simple form of float-feed
carbureter. It consists of a cylindrical chamber contaiiung the
float F, which is guided by a
stem above and below. Just
outside of the float chamber is
the air passage A-I, contain-
ing the vertical fuel tube X.
The fuel enters at G, filling the
float chamber and passing
into the fuel tube through the
regulating needle valve N.' At
F is a small valve attached to
the float, which closes the
opening at G as the float rises,
shutting off the fuel supply.
The level of the fuel is thus
kept steady at a certain point

^

73

^

.

V

Fig. 29. — Float-feed Carbureter.

in the float chamber and fuel tube, and is so adjusted as to not
quite overflow from the opening O of the fuel tube.

The air, drawn in by ihe suction stroke of the engine, rushes
past the opening O and draws up and absorbs a small amount of
the fuel. At/W is a cone of fine wire gauze, which catches any
fuel not carried away by the air current, and holds it in suspen-
sion ready to be taken up on the next stroke. The carbureter
is fastened to the engine by the threaded end I.

At T is the throttle, consisting of a sort of shutter which may
be turned by the handle H and partially or wholly close the out-
let opening /, thus varying the amount of mixture passing to the
engine, and consequently the speed. The fuel supply is regu-

VAPORIZERS AND CARBURETERS

29

lated by the needle valve N as before. The float F is made either
of copper or of cork. At P is a small plunger which, when pressed,
forces the float down and admits an amoimt of fuel to flood the
chamber and fuel tube and make certain of a plentiful supply
of fuel for starting. The cover C unscrews to allow access to the
float chamber.

In operation, as the fuel is used up by the engine, the level in
the float chamber drops sUghtly, lowering the float F and finally
opening the valve V and allowing the fuel to flow in, restoring
the level. This raises the float, closing the valve V and stopping
the flow. Thus the level of the fuel in the fuel tube is kept steady
and the same amount is drawn in at each stroke.

Fig. 30 shows a further appKcation of the float principle. In
this case an annular or "doughnut" shaped float is used, which

floats freely just above the long
end of a lever L, which is pivoted
at p. The short end of this lever
is forked and rests under the pro-
jection on the fuel valve V. The
fuel enters at G as before, and
flows out through the small open-
ings to the outlet 0, where it is
picked up by the current of air
entering at A. The throttle T is
a disc regulated by a short lever
as before. At^isaflatauxiUary
air valve held in place by the spi-
ral spring S, which admits more

, „ „ . , air as may be needed. In opera-

FiG. 30. — Central Flow Float-ieed .. „„ .•', ,,„i .„ „„„j „„ ^.1

Carbureter. tion, as the fuel IS used up the

level falls in the fuel chamber,
allowing the float to settle and finally by its weight press down the
end of the lever L. This raises the valve V and allows fuel to enter
and raise the level in the float chamber, lifting the float clear of the
lever and allowing the valve V to settle by its own weight aided by
the small coiled spring, closing the fuel, supply. The fuel flow
is regulated by the needle valve N. It is found that if the
fuel supply is regulated for slow speed, the increased suction at
high speed will draw in an undue amount of fuel, making the

30

MAEUSTE GAS ENGINES

mixtiure too rich. For this reason the atixiKary air valve A is
fitted; it is so adjusted that the increased suction at high speed
will draw it from its seat and admit a certain amount of pure
air to dilute the mixture to the proper point. The amoimt of
air admitted by the auxiliary air valve may be regulated by
changing the tension on the spring S, by means of the threaded
spindle E. Increasing the tension on the spring will decrease
lie lift of the valve, and consequently decrease the amount of air
admitted, and vice versa.

It will be noticed that the air passage is contracted opposite
the opening 0; this is for the purpose of reducing the area of the
passage and increasing the velocity of the air current and making
the action of the carbureter more positive at low speeds.

The carbureter is secured to the engine by the threaded end
/. The air inlet is also often threaded and a pipe fitted to allow
the air to be drawn from some warm part of the engine, as around
the exhaust pipe. The use of warm air tends to steady the action
of the carbureter, particularly in rough or foggy weather when
the air drawn in would otherwise be more or less moist. As the
moist air will take up less fuel than the warm air, the amount of
mixture would vary from time to time, making the speed of the
engine unsteady; this is pre-
vented by warming the air.

Another carbureter operating
upon a similar principle, but of
different appUeation, is shown in
Fig. 31. In this case a horse-
shoe-shaped float is used, which
is rigidly connected to the short
lever, pivoted at P, controlling
the fuel valve F. The air enters
at the upper opening and passes
through the space B under the
auxiliary air valve A. When
more air is required at high
speed the suction draws in the

auxiUary valve and increases the _ m . t j o v .

: • rn. • 1 • 1. ij Fig. 31. — Float-feed Carbureter.

opemng. The air valve is held

in place by the spring S, the tension on which can be regulated by

screwing the threaded stem 2? in or out.

VAPORIZERS AND CARBURETERS

31

The fuel opening is placed in a small projection into the air
passage in order to bring it into the center of the current of air.
At T is the throttle, consisting in this case of a thin plate, which
may be moved by the lever L so as to partially or wholly close the
opening. The threaded end / serves to attach it to the engine.
At £ is a "tickler" consisting of a small bent lever and a plunger,
which may be pressed down to depress the float and produce a
slight overflow from the opening for starting the engine. A
pet-cock is fitted at D to drain off any sediment that may collect.
The carbureter shown in Fig. 32 is constructed on a slightly
different principle. The level in the float chamber is adjusted

somewhat higher than the fuel
opening 0, so that a small puddle
is formed about the orifice in the
bottom of the U-shaped air pas-
sage. The air passage is contracted
just at this point, increasing the
velocity of the air current. The
air in passing over the surface of
the puddle absorbs some of the
fuel. This device is claimed to
give a constant mixture owing to
the fact that as the speed of the
engine increases more of the pud-
dle is carried away, leaving less
surface exposed, so that when the
increased velocity of the air current woxUd naturally absorb a
greater amoujit, there is less surface for it to draw from. The
mixture cannot become too rich and no auxiliary air valve is
necessary. At high speed the puddle is entirely carried away and
the fuel sprays out. An annular float is used, rigidly connected
to a short lever pivoted at P. Other parts are similar to those
of the carbureters already described.

Although the actual details of different carbureters may
differ considerably, the principles governing their action will be
found to be similar to the above, and the several parts will be
fotmd in one form or another.

Comparing the carbureter last described with that shown in
Fig. 29, it will be seen that if this carbureter is tipped sidewise

Fig. 32. — Carbureter of the
"Puddle" Type.

32

MARINE GAS ENGINES

the relation of the orifice to the level in the float chamber will
vary, causing an irregular flow of fuel from the orifice. This is
what would take place when the boat rolls in a seaway. This
irregularity is avoided in the types with the circular float, termed
"central flow" type, as no matter what the angle of the carbureter
the center of the float is always at the orifice.

Among the advantages of the float-feed carbureter over the
mixing valve are: The check valve is done away with, avoiding
the noise and the loss of the suction necessary to raise it. A more
uniform mixture is obtained, as the fuel is always at the same
level; this is particularly so in a sea, as there is a sufl&cient body
of fuel in the float chamber to draw upon, at times when the boat
is pitching and the tank might be momentarily lower than the
engine, interrupting the flow. The speed is more readily controlled
and the engine may be run at a slower speed where the suction
would not be great enough to Uft the check valve. The float-
feed carbureter cannot be fitted directly to a two-port, two-cycle
engine, as there is no valve to hold the base compression, but may
be used by fitting a check valve between, such as are regularly sold
for that purpose. It may be fitted directly to the three-port tjrpe.
Check Valve for Two-port Engine. — Fig. 33 shows a very
convenient form of check valve for use when it is desired to use

a float-feed carbureter on a two-port,
two-cycle engine. The stem of the
conical seated valve V is carried in
the projection N from the inside of
the shell. It is held against its seat
by the cofled spring 5. The large
thread is screwed to the engine and
the small end carries the carbureter.
The suction is thus in the direction
of the arrows. The valve V should
be made as Ught as possible so as not
to introduce unnecessary friction.

This valve may to good advantage be incorporated in the
inlet to the carbureter, as is to some extent done.

Fuels. — The carbureters already described are primarily
designed to operate on gasoline as a fuel. While under certain
conditions they may vaporize alcohol or even kerosene, they cannot
be said to be generally suited to these fuels.

Fig. 33. — " Check Valve " for
Two-cycle Engine.

VAPORIZERS AND CARBURETERS

33

Kerosene is far less volatile than gasoline and to so vaporize
it that it can be ignited by the electric spark special devices must
be used to preheat it to a considerable degree. For this purpose
the heat of the exhaust is usually used. The various devices,
although varying in detail, are in effect little more than jackets
or annular chambers around the exhaust pipe through which the
fuel is passed, thereby becoming heated by the hot exhaust pipe.
Arrangements are made to start the engine on gasoline and change
to kerosene when the engine has become thoroughly heated.

The device illustrated in Fig. 34 is a fair example of this form
of device. It is cut into the exhaust pipe £ £ so that the exhaust

Fig. 34. — Kerosine Vaporizer.

gases pass directly through it. The flange F is bolted to the intake
manifold in place of the regular carbureter, which is connected
below the device at C. There are three annular chambers P, S,
and H. The kerosene enters through the pipe K to the chamber
P, where it is heated moderately. It passes out of the top of the
chamber through the pipe as shown, through the shut-off X and
the T, to the carbureter in the usual way. At the same time
air is drawn into the chamber H through the slots A, and heated
thereby. This air then passes out through the air pipe to the
carbureter C, where it takes up the hot kerosene. This noixture
then passes into and through the chamber 5, where it is mixed

34 MARINE GAS ENGINES

and further heated on its way to the intake manifold. Gasoline
for starting is brought in through the pipe G having the shut-off
Y. The engine is started on gasoline wifli the shut-off X closed;
when it is heated up the gasoline is shut off and the valve X
opened, allowing the kerosene to flow.

The engine shown in Fig. 23 has a device of this kind shown
at V. Devices working on this principle can only be used on four-
cycle engines, where the fuel does not pass through the base.

This principle is often incorporated in a special form of exhaust
manifold, having annular spaces around the central pipe which
carry out the functions above described.

The use of a single carbureter for both fuels requires that the
contents of the bowl be exhausted or drawn off before the fuel
can be changed. For this reason, a dual carbureter having two
float chambers, with a single air passage; or two separate car-
bureters may be used.

In connection with devices of this nature provision is often
made for injecting a small quantity of water into the cyUnder
with the object of preventing the formation of carbon, but if the
vapor is kept sufl&ciently hot this appears to be unnecessary.
' This form of arrangement can be made to operate well on
kerosene, but will not take care of the heavier oils which require
a greater degree of heat to ignite and can only be burned in engines
carrying a high compression built specially for this fuel.

CHAPTER V

Ignition Devices

In order that the compressed charge of fuel may explode and
do work upon the piston, it must be ignited. In the case of the
gasoline engine and some kerosene engines the electric spark is
used. Two forms of electric ignition are used, viz.: the "make-
and-break" or "touch" spark system and the "jump" spark
system.

"Make-and-break" Ignition. — The principle upon which this
system depends is the formation of a spark when an electric cir-
cuit is broken. A property of the electric current, which need not
be discussed here, causes a current to flow for a short time after
the circuit is broken; it thus will jump across a short space and
form a spark. This property is accentuated by the use of a spark
coil as described in the next chapter.

The operation of the make-and-break spark may be illustrated
by Fig. 35. The point P is electrically insulated from the metal
of the engine; the "flipper" or rocker arm F
is on a short shaft and may be turned sUghtly
to make an electric contact between it and
the point P, completing the circuit. The two
points are brought together while the piston
is on its up stroke, allowing the current to
flow for a short time. At the time of ignition
the two points are quickly drawn apart by a
spring or some other means, breaking the cir-
cuit, and the spark occurs. It can thus be
seen that the idea is to provide a means
whereby an electric circuit may be "made"
and "broken" inside the compression space at the proper time.

The mechanism for operating the make-and-break ignition is
well illustrated in Fig. 36. The lever L is on the outer end of
the shaft carrying the flipper F. The rod R moves in the guides
G, G, and is moved up and down by the same eccentric which

35

Fig. 3S- — Sparking
Points for "Make-
and-break" Ignition.

36

MARINE GAS ENGINES

Fig. 36. — " Make-and-
break" Ignition.

operates the water piunp, the connection being made at E. On
the rod R is the sliding collar C and a pivot
carrying the tappet T. The screw A is in
line with the projection on the tappet T. In
operation the collar C is pressed down by the
spring 5 on to the lever L, forcing the latter
down and separating the points inside the
cylinder. The eccentric operating the rod R
is so placed upon the shaft that the rod moves
in exact time with the piston. As the piston,
and consequently the] rod R, moves upward,
the tappet T strikes the collar C and lifts it
out of contact with the lever L. The lever
L is then raised by the small spring, bring-
ing the sparking points into contact and allowing the current
to flow. As the rod R rises still further, and comes nearly to
the top of its stroke, the tail of the tappet T strikes the screw A,
throwing this end down and the upper end out, and allowing
the collar C to snap off and be forced rapidly down by the
spring S. The collar strikes the lever L, throwing it down quickly
_ and breaking the contact in the cylinder. As the

rod R descends, the tappet T snaps over the collar C
and is ready for the next stroke. The contact is
thus broken suddenly, the more suddenly the more
effective the spark. By turning the screw A, the
tappet T may be made to strike it earlier or later,
thus changing the time of ignition. An engine hav-
ing this particular mechanism is shown in Fig. 12.

A section of the plug P is shown in Fig. 37 ; the
large collar C is threaded and screws into the cylin-
der cover. Through the center of this collar is the
insulated sleeve / of mica or fiber. The pin P is
threaded through the insulated sleeve and held in
sulat'ed Ter- place by the lock nut N. On the top of the pin are
minal for binding nuts for the electric wires.
'h^^"'l^^'. "^^^ sparking points require cleaning at inter-
tion. ^°'" "v^^^i which is accomplished by removing the en-
tire upper combination; the flipper can then be
cleaned through the hole thus opened in the cover.

Fig. 37. — In-

IGNITION DEVICES

37

Another form of gear is shown in Fig. $8 which is easier to take
care of than the preceding. Both insulated point and movable
flipper are mounted on a sort of plug which
is bolted to the side of the cyluider, with
the sparking points on the inside. The
rod J^ and tappet T are similar to the
other. The rod I is insulated from the
body of the plug and extends a short dis-
tance beyond the back. The spindle B
carries the flipper F on its rear end and
the lever L on the front end. On the
same spindle B, but free to turn, is the
flat hammer H; the circular spring S
presses the hammer H down against the
lever L. As the rod R rises, driven by
the eccentric, the tappet T strikes the
hammer H, turning it and the lever L im-

"ivf l~ f°i*^^^"^? • til the flipper is in contact with the in-
'Make-and-break" Igni- i j. j j x t'u i t ^ i

tion. sulated rod /. The lever L can turn only

a short distance, so that as the tappet T
rises still higher it carries the hammer H away from the lever
L, separating them by a considerable angle, against the pres-
sure of the spring S. As soon as the tail of the tappet T strikes
the screw A, the upper end is drawn in and the hanuner forced
down quickly by the spring, striking the lever L and quickly sepa-
rating the points.

The two mechanisms just described are both used on two-cycle
engines, as they are driven from the shaft and operate on every
revolution; their operation also is independent of the direction of
rotation of the engine.

Similar gear is used on four-cycle engines; in this case the
sparking points are placed as near as is convenient to the inlet
valve so as to be always in the purest mixture. The gear must
be operated from the half-time shaft. In Fig. 39 is shown a very
simple form of gear; it consists of a removable plug carrying the
insulated point /, the flipper F, and the lever L as before. The
lever L has a hole in the end through which passes the rod R.
The lower end of the rod is guided at G and rests upon the cam
K on the end of the cam shaft. As the cam K revolves the rod

38

MARINE GAS ENGINES

Fig. 39. — "Make-and-
break" Igniter.

is gradually raised, lifting the lever L until the points are in
contact. The lever L then remains sta-
tionary; the rod, however, continues to
move, compressing the spring S and rais-
ing the head H considerably above the lever
L. When the cam has turned sufficiently,
the lower end of the rod R drops off the
step and the rod is forced down by the
spring S, the head H striking the lever a
sharp blow and separating the points. The
time of ignition is varied by moving the
end of the rod to the right or left, causing
it to drop off the step earUer or later. As
this gear will only work in one direction the
cam K must be provided with a ratchet to
prevent damage when the engine is turned
in the opposite direction to which it runs.

Gears similar in action to the above
are on some engines arranged entirely on the top of the cylinder
cover, and operated by shafts and bevel gears. This makes the
gear very compact and allows it to be protected by an ornamental
cover.

These illustrations will serve to show the principles on which
the gears operate. A successful gear should have the following
qualities, viz. : it should separate the parts quickly, as the strength
of the spark depends upon the speed of separation; it should be
simple, with as few parts as possible; some means should be pro-
vided for changing the time of ignition while the engine is running,
as the best time for ignition will vary for different speeds; it
should be easy to get at and clean the sparking points; the points
should be tipped with platinum or some hard metal, as the steel
points are rapidly worn away by the heat, and become fouled.

Spark Coil. — The type of coil used in connection with the
make-and-break ignition is shown in Fig. 40. It consists of a
bundle of soft iron wires C, encircled by a coil W of several layers
of rather coarse wire. The ends E, E are of wood and carry the
binding posts B, B,to which the ends of the coil W are fastened.
The coil is connected into the battery circuit, and the electric
current simply passes through it. The electrical action of the coil

IGNITION DEVICES 39

may be sufficiently explained by saying that the passing of the

current around the iron core
greatly intensifies the spark
at the breaking of the circuit.
Jump-spark Ignition. —
This system of ignition is
very simple in appearance,

17.^ T^• _ « "TVT 1 J v 1 » the only mechanism on the

Fig. 40. — Diagram of Make-and-break " • iT • ^i j. j.

Spark CoU. engme bemg the commutator

or timer, a device for making
and breaking the battery circuit when the spark is desired. The
coil used in connection with this system is similar to the usual
type of induction coil, having primary and secondary windings.
The circuit in the primary or battery wire is made and inter-
rupted by the timer and a spark occurs in the secondary wire,
which is connected to the spark plug.

The simplest form of timer is shown in Fig. 41. It consists
of a small frame F which is supported by the end of the engine
bed B and can be rotated upon it.

The small plunger P is carried in a holder which is insulated
from the body of the frame by the insulating material /. A spring
behind this plunger forces it out against the insulating fiber disc
D, which is fastened to the engine shaft and revolves with it.
A small brass segment S is fastened on the circumference of the
disc and is in electrical connection with the shaft by the wire or
clip. The binding post B takes one end of the battery circuit;
the other end being grounded on the engine. When the plunger
P rests upon the fiber the circuit is not complete and no current
passes, but as the segment S passes under the plxmger, the circuit
is completed for a short time through the engine shaft and body
of the engine, and then broken again. By turning this device
one way or the other the time of the spark may be changed.

This timer is very simple and compact and works very well
on small two-cycle engines. If two cyhnders are to be fired
another plunger would be fitted directly opposite the present one.

Another simple form of timer is shown in Fig. 42. The cast-
ing F, carried by the engine frame, has a projecting arm, at the
end of which is the post P- On the shaft is the cam C having the
projection or "nub" on its face. The contact spring S is carried

40

MARINE GAS ENGINES

by the post P and rests normally on the round face of the cam
C. At 5 is a binding post which is insulated from the main body
and which carries the adjustable contact screw. The contact
screw is adjusted to leave a slight space between it and the spring
5. One battery wire is attached to B and the other to the engine.
In the position shown no current will pass; at the time of ignition,
however, the nub on the cam will pass under the spring and force
it up into contact with the point of the contact screw, completing
the circuit and breaking it again as the cam passes on. The
handle H is used to revolve the whole mechanism, thus varying
the time of ignition by causing the cam to strike the spring earlier
or later.

The timers just described are for single-cylinder engines, but

Figs. 41-42. — Simple Timers.

may be adapted to double cylinders by duplicating the mecha-
nism in a diametrically opposite position. Timers of this type
are well suited to two-cycle engines.

The more pretentious timers are made entirely independent
of the engine shaft, as in Fig. 43. They are operated from an
independent shaft, as the cam shaft of a four-cycle engine, or, in
a two-cycle engine, from a shaft driven by gears from the engine
shaft as in Fig. 11. This timer is somewhat similar to that last
described, the action of the cam C and the spring S being the
same. In this case, however, the entire base is made of fiber,
thus insulating both posts B and P. A wire to each post passes
through the holes H, and a removable cover is fitted over the

IGNITION DEVICE 41

whole. By means of the eye E to which a link is fitted, the whole
timer is kept from turning, but may be turned slightly when
desired, to vary the time of ignition. This timer is shown on the
engine in Fig. 25 on the rear end of the cam shaft.

Fig. 44 shows a timer for a two-cylinder engine on somewhat
the same principle as the last. The posts B, B are insulated
from the body of the timer by the insulating sleeve /. The con-
tact points P are forced out by the coiled spring 5, but are in
electrical contact with the posts B.

The lever L is pivoted at E and at its outer end carries the
friction roller R. The flat spring F presses the lever L out so that
the roller always bears on the face of the cam C. As the projec-
tion on the cam C passes under the roller the contact is made

Fig. 43. — Single-point Timer. Fig. 44. — Two-point Timer.

with the point P. The roller is added to reduce friction. The
springs behind the points P are introduced in order to have a
furm contact between the points without undue pressure on the
lever L.

The entire timer is covered with a cap.

This timer, with the contact points placed opposite one
another, is arranged for use on an engine where the impulses occur
at regular intervals. When used on a four-cycle engine having
the arrangement of cranks shown in Fig. 80, which gives irregu-
larly occurring impulses, the contact points, instead of being
placed opposite, are located on the quarters, or at right angles.
This allows for the idle strokes between the impulses.

42

MARINE GAS ENGINES

Fig. 45. — Four-point Timer.

A timer for four cylinders is shown in Fig. 45. The contact
here is a rubbing contact between the
projection P on cam C carried by the
timer shaft, and the steel ball B which
is pressed out by the coiled spring S.
The rubbing contact gives excellent
results, as any corrosion of the points
is quickly rubbed off by the friction.
The' ball holders must be insulated
from each other and from the body
of the timer, either by insulating
sleeves or an entire ring of insulat-
ing material; both methods are com-
mon. By means of the arm A the
timer is prevented from turning, and its position also is regulated.
Spark Plugs. — In order to utilize the spark produced in the
coil by the action of the timer, some form of spark plug is neces-
sary; different forms of plugs are shown in Fig. 46. The principle
of all is essentially the same: the outer shell ,S has a threaded end
and screws into the metal of the cylinder; inside of this shell
is a core C of in-
sulating material
such as porcelain,
mica, or lava;
through the center
of the insulating
core passes the
metal stem R hav-
ing a binding post
on the upper end.
Points from the
core and the shell
are brought out to
within about -^"
apart. As the body
of the plug is

Fig. 46. — Spark Plugs.

screwed into the cylinder and the wire carrying the ignition
current is attached to the binding post at the top of the inside
rod, the circuit is complete except for the gap at the points.

IGNITION DEVICES 43

and it is the jumping of the current across this gap that causes
the spark.

Plugs are made in a large variety of forms — but the principle of
all is the same. The core may be either molded in place or secured
by a threaded sleeve as at N, the joints being made tight by the
washers or gaskets G. It is of the greatest importance that the
joints between the various parts of the plug be pressure-tight, as
otherwise a loss of compression wiU occur. The insulation at the
same time must be perfect, as the secondary current is of very high
voltage and will penetrate the usual forms of insulation. One
of the most serious difficulties with spark plugs is the deposit
of soot around and on the sparking points, causing a short circuit
and preventing the formation of a spark. Various shapes are
given to the points and to the ends of the core and shell with the
idea of lessening this deposit, the most common design being to
leave an annular space around the core, between it and the shell
or the rod. The several sketches are self-explanatory.

Jump-spark Coil. — Fig. 47 shows a diagram of an induction
coil such as is used in jump-spark ignition. It is similar in prin-
ciple to the ordinary induction or medical coU. It consists of
a core C, of soft iron wires, about which is wound the primary
coU, shown by the heavy Une helix. The primary winding con-
sists of a few layers of heavy wire, whose electrical resistance is
very smaU. Outside of the primary winding, and very thoroughly
insulated from it, is wound the secondary winding, shown by the
hght line helix. The secondary winding consists of a great many
turns and layers of very fine wire, of very great electrical resist-
ance. By the electrical principle of induction, each time the
current is made or broken in the primary winding, a current will
pass through the secondary. If then die ends of the primary
winding be connected through the timer and a battery, and the
ends of the secondary winding are connected through a spark
plug, a spark will pass in the plug each time the primary circuit
is made or broken by the timer. There must be no direct connec-
tion between the primary and secondary coils, the action of one
coil on the other being by induction only, with no passage of
current from one Coil to the other. A coil of this description gives
one spark for each make or break in the circuit. It is called a
"non-vibrator" coil, or transformer. In order to cause a series

44

MARINE GAS ENGINES

Fig. 47. — Diagram of "Jump-spark" Coil.

of sparks to pass at each break in the primary circuit, the vibrator
is added. The two ends of the secondary winding are connected
to the binding posts S, S, and the ends of the primary winding

are connected, one to the
upper binding post B, and
the other to the post ^. The
post E carries the vibrator
spring V, on the end of which
is the iron disc D standing
opposite to and a short dis-
tance away from the end of
the iron core C. The post A
carries an adjusting screw
against which the vibrator
spring V bears. The post E
is connected with the lower
binding post B. If now the connections are made to the binding
posts B, B, a circuit may be formed through the primary binding
post A, adjusting screw, vibrator spring V, and post E, and a cur-
rent will pass through the primary winding, causing a consequent
passage of current in the secondary. The flowing of the current
around the iron core magnetizes it and causes it to attract and
draw towards it the iron disc or armature D. This draws the
vibrator spring out of contact with the screw A and breaks the
primary circuit, causing a current to pass through the secondary
in the opposite direction. The breaking of the primary current
also causes the core to lose its magnetism, thus releasing the disc
D and allowing the vibrator to spring back into contact with the
screw A, when the action is repeated. This automatic interruption
of the primary circuit, which is very rapid and independent of
that of the timer, causes a series of currents to pass rapidly in
the secondary.

Owing to certain electrical effects, the spark which passes
when the primary circuit is completed is not as strong as that
which passes when the current is broken, and it is the "break"
spark which is made use of.

The current in the primary winding is of low voltage and
relatively large volume, while that in the secondary is of extremely
high voltage but very small volume. The relative proportions

IGNITION DEVICES

45

CT^

of the two currents are regulated by the size and amount of wire
in each coil. The condenser, shown below the coil, consists of
layers of tin-foil, insulated from each other, alternate sheets of
which are connected to two terminal wires, which terminal wires
are cormected, as shown, with the posts A and E. The action
of the condenser is entirely electrical, and need not be considered
here, except to say that it intensifies the spark. The entire coil
is enclosed in a box with only the binding posts and vibrator in
sight.

Coil and Plug Combined. — Fig. 48 shows a combination of
spark coil and plug which is designed to be fastened
directly to the cylinder. The spark coil is supported
upon the end of tie plug, and the ends of the secondary
winding are connected directly to the sparking points
P, P. The primary winding is connected to the bind-
ing posts B,B. The whole is enclosed in a mica-covered
case which is protected by a brass cage. A screw
thread T allows the whole to be screwed into the cyl-
inder in place of the regular spark plug. As only the
primary winding is exposed, this system is claimed to
be waterproof. The primary current is interrupted by
a separate vibrator operating on the same principle as
that of the usual type of coil. This system requires
a separate coil for each cylinder, although all the coils
are operated from a single vibrator. This system is
therefore apt to be more expensive than the usual
system, although very satisfactory for use in exposed
positiolis.

Primary Batteries. — To furiiish the primary current, for
starting at least, some form of electric battery must be used.
There are several forms of wet cells on the market, but they all
are likely to require considerable attention. It is probable that
the dry cell is the best for all-around boat use. While they are
sometimes imreliable, if care is used in their selection and they
are carefully kept free from moisture, good service can be obtained
from them.

The cells should be tested when bought, and from time to
time diuring their use, and any which may have run down should
be replaced by new ones, as a single weak cell in a set will retard

Fig. 48.

Combined

Coil and

Plug.

46 MARINE GAS ENGINES

the action of the good ones. In testing the cells, the ammeter
should be kept in contact only long enough to obtain the reading,
as it forms a direct short circuit, and if held in place for any length
of time wUl soon ruin the cell.

For ignition use the cells are connected in "series," that is,
the carbon of one to the zinc of the next, and so on.

From four to six cells should be used in each set; if fewer are
used the spark is likely to be weak, and if more are used the current
is of such intensity that the contact points of spark coils or igniter
are rapidly burned away.

Dry cells should be fitted in duphcate sets so that one set
may be recuperating while the other is in use.

Even when a magneto is fitted, the batteries must be relied
upon for starting, after which the magneto may be switched in.

When dry cells are used alone, considerable economy may be
had from a series-multiple connection. In this method several
sets are made by connecting four or five cells in series. These
sets are then connected up in multiple. Although more cells are
required it is claimed that this method of connection results in
final economy.

Storage Battery. — This form of battery is one of the best for
ignition purposes, as it is very reUable as long as it is charged.
It must, if used alone, be taken on shore for charging, which is
something of a care. A very satisfactory arrangement is the fitting
of a dynamo in connection with the storage battery, and so con-
necting them that the d5Tiamo charges the battery, while the
current for ignition is being drawn from it. In tJiis way the
battery acts as a sort of reservoir for the current, and 'makes
the ignition independent of the engine and dynamo speed, and
also avoids the inconvenience of taking the battery ashore for
recharging. At the same time the engine can be started on the
current from the battery. This arrangement also allows the use
of a certain amount of current for fighting purposes, or if the
dynamo and storage battery are large enough, the entire boat
may be lighted. This is fuUy explained imder wiring.

Dynamos and Magnetos. — There is little fundamental difference
in the action of a dynamo and a magneto. Both generate a cur-
rent of electricity by the revolution of an armature containing
many turns of wire within a magnetic field. The points of dif-

IGNITION DEVICES

47

ference are found in the construction, in that the magnetic field
of the dynamo is maintained by the passage of the current through
coils of wire which are wound on the fields; in the magneto,
permanent magnets are used for field magnets. The current gen-
erated may be either "direct" or "alternating." The former is
of constant amount and always flows in the same direction: the
latter or alternating current flows first in one direction and then

Fig. 49.

in the opposite, at rapidly recurring intervals, and also varies in
intensity at every point in the cycle. The dynamo may be ar-
ranged to put out either a direct or alternating current, while the
magneto gives only alternating current.

For use with small engines, as an alternative to the batteries,
the simplest forms of magneto or d)mamo are used, being usually
driven by a belt or friction wheel from the fly wheel. For use

48 MARINE GAS ENGINES

with the make and break system either may be usually used,
while for a jump-spark system and a coil like Fig. 47 the direct-
current dynamo must usually be used.

The fundamental difference between dynamo and magneto is
shown in Fig. 49. The armature of the dynamo shown at D has
a series of slots running lengthwise with a coil of wire through
each. The ends of these coils are connected to a commutator C
at one end of the armature, from which the current is collected
by brushes. The windings of the field coils are shown at F. As
far as general construction goes it is the same for dynamo and
motor and under most conditions these are interchangeable. ^

The magneto sketched at M has a so-called "shuttle" arma-
ture, with only a single coil; there is no commutator, but collector
rings may be fitted. The permanent magnets are shown at F.

Magnetos. — Magnetos are used in such a variety of forms
that it is not possible to attempt a description of all, but in all
cases the same general principles apply. The best and perhaps
least compUcated form of magneto is the so-called "high tension"
type. Tlus instrument is entirely self-contained, generating, trans-
forming and distributing the current without the aid of outside
coils. This form must be gear driven from the engine shaft, and
exactly timed with it, as flie distribution of the ignition current
to the plugs is dependent upon it. It is usually geared from the
cam shaft, as this gives a convenient place of attachment to the
engine.

Fig. 50 shows an elementary section of a high-tension magneto.
The armature 4 revolves in ball bearings between the poles of
the permanent magnets M, usually made up of two or more sepa-
rate magnets for constructional reasons. The armature carries
two separate coils, a primary winding, made up of a few turns of
coarse wire, and a secondary^ winding, of many turns of fine wire.
The armature is of similar construction to the coil of Fig. 47 and
does the same work. The current in the primary coil is generated
by its revolution in the magnetic field of the magnets: this
primary current is then periodically interrupted, which induces
currents in the secondary coil. The secondary coil is placed on
the armature simply for convenience in construction, the fact of
its revolving having no electrical effect of value. These windings
are shown at P and 5 respectively, a condenser, is also fitted as

IGNITION DEVICES

49

V J^^^^%.

rr

"kM

fv nH

f^

11 11

li e

■^

l-l,NI

--

<n

/^

-

^s- 1

"

so UARINE GAS ENGINES

shown at C. The arrangement for interrupting the primary circuit
is shown at the right in the circular box called the breaker box.
On the end of the armature shaft, is a plate carrying the breaker
block B and the pivoted breaker arm A. The block B is insulated
from the plate and carries one of a pair of contact points P; the
other point is carried in the end of the pivoted arm A. The con-
tact is made or interrupted by a sUght movement of the arm A.
This mechanism revolves with the armature. The enclosure,
which is circular in form, remains stationary and carries on its
inside surface two diametrically opposite projections or trips T.
The end of the breaker arm in its revolution rides up on these
trips and separates the points at P. As one end of the primary
coil is attached to the insulated block and the other end to the
metal of the armature, the primary circuit is complete until inter-
rupted by the separation of the points P, which causes a current
to flow in the secondary winding.

On the opposite end of the shaft is a slip ring R to which one
end of the secondary winding is attached, with a collector brush
N to which the secondary current is delivered. In the case of a
single cylinder motor it could be wired direct to this brush.

Motors of more than one cylinder are served by an additional
distributor mechanism. A gear G on the armature shaft meshes
with a larger gear G, carried by the frame of the magneto. In
front of the larger gear is a stationary distributor plate D of fiber
shown in the front view, on which are arranged in a circle a nimiber
of equidistant contact pieces equaling the niunber of cylinders
to be fired. Attached to the large gear is an insulated contact,
which in revolving passes over each of the contacts on the dis-
tributor plate D; connection is made from the brush N through
the hollow shaft to the contact on the gear G. In this way the
secondary current is sent to each cylinder in turn. In Fig. 49 it
will be seen that there are two points in a revolution of the arma-
ture where a current will be generated. This is the reason for two
trips in the breaker; it is for this reason also that the distributor
arm revolves at a slower rate than the armature shaft, for a four-
cylinder engine one-half as fast. The interrupter mechanism is so
arranged as to break the circuit at the point of Fig. 49, as at this
point the primary current is strongest. An elementary circuit dia-
gram for this form of magneto is shown in Fig. 51, the grounded

IGNITION DEVICES

SI

lines representing the completion of the circuit by the metal
of the engine.

At 5 is a safety gap consisting of two points a short distance
apart, one of which is connected to the brush N. This gap pro-
vides a ground for the current in case of a broken external circuit
and prevents damage to the armature. At X is a spring making
contact with the insulated block B by which the primary circuit

To Plugs

"I'M •\'"^

C/

'1.-2 1
' r-tt I

l» I

\,^

./•i

ARMA-rui^e.

Fig. SI- — Circuits in High Tension Magneto.

is grounded, stopping the action of the magneto. The taper and
nut on the end of the shaft fasten the coupling or gear for driving it.
As before stated, the high-tension magneto is a complete and
self-contamed system of ignition. It will, however, give a current
only when the armature is turning at a fair speed. A small motor
may often be turned by hand at a high enough speed to start
on the high-tension magneto directly, but this is plainly impossible
with a large engine. For this reason some form of battery igni-

52 MARINE GAS ENGINES

tion must be used for starting or a starting motor fitted. Many
varieties of magneto are in use which allow the use of batteries
and transformer coil for starting. The high-tension magneto may-
be so modified as to allow this, without altering its action or the
wiring connections. This form is the "dual" system, and the
modifications consist of the addition of an extra interrupter arm
in the breaker box and the necessary wiring to and from a trans-
former coil. This extra interrupter is necessary as the regular
interrupter is closed except at the moment of the break, which
would be too great a drain on the battery. The transformer coil
is similar to that of Fig. 47 but without the break mechanism,
that on the magneto taking its place. When the battery is in use
the armature coils are idle, only the breaker being used. The
current from the battery passes to the primary of the coil through
the breaker, and the high-tension current produced in the secondary
by the interruption of the primary circuit is brought back to the
distributor arm of the magneto and sent to the proper cylinder.
The engine can thus be started on the batteries, and the magneto
current cut in after the engine has started.

The "low tension" magneto is similar in action to the dual;
the armature, however, has only a single coarse winding and
generates only a current of low voltage, about the same as that
of the battery. A transformer coil must always be used; but the
secondary current is distributed by the magneto as before. Con-
nections are made to cut in a battery for starting.

There are so many variations in the arrangement of the cir-
cuits that no diagrams except for the high tension can be given,
but individual diagrams can always be obtained from the makers
of any particular magneto.

The speed of the magneto is governed by the number of
cylinders. For four-cycle motors these speeds are as follows:

2 cylinder motors, cranks as Fig. 74 cam shaft speed

2 " " " " " 73 crank "

3 " " f crank shaft speed

. tt IC li U it

6 " " i| " " "

Q (( IC (1 (( ((

For two cycle motors the speed is doubled.

IGNITION DEVICES 5$

Ignition by Hot Bulb. — In the case of engines burning fuel oil,
whidi does not vaporize and cannot be passed through a car-
bureter or similar device, the "hot bulb" igniter shown in section
in Fig. 52 is used. It consists, as the name impUes, of a chamber
or bulb B, of spherical or other convenient shape formed in or
fitted to the cylinder head. The cylinder head can be kept hot
without detriment to the action of the engine, and as the ignition
depends upon the heated con-
dition of the device, the head
is the logical place for it.
When this form of ignition is
used air alone is drawn into
the cyUnder and compressed
as usual. The bulb is first
heated by a torch or other
external means. At about
the point of maximum com-
pression the fuel is injected
in through the nozzle N, and
upon striking the hot surface
of the bulb is at once ignited,

Fig. 52. — Section of " Hot Bulb " Igniter.

The heat taken up by the bulb
during the explosive stroke keeps it hot for the next injection of
fuel; the heat due to the compression also adding some heat to it.
This class .of igniter is used in crude oil engines. There are
many different shapes of bulb adopted, but the above fairly repre-
sents the principle.

CHAPTER VI

Wiring

Single Cylinder, Make and Break. — The wiring for the make-
and-break system is the simpler of the two, and will be considered

first. It is shown in diagram
in Fig. S3. If one wire of
the circuit is fastened to the
metal of the engine and the
other to the insulated point
of the igniter, there can be
no passing of current except
when the points are in con-
tact inside the cylinder. The
insulated point is shown at
I; at G is the other wire of
the circuit attached to the
engine base. The circuit is
completed through the bat-
The batteries are connected, the zinc of one

Fig. S3- -

- Single-cylinder, "Make-and-
^break" Ignition.

teries and the coil C.
cell to the carbon of the next,
and so on. The switch 5 is
inserted to open the circuit
when not in use and prevent
waste of batteries. When the
switch is in contact the cir-
cuit is complete except as
made and broken at the spark-
ing points. When duplicate
sets of batteries are used, a
three-point switch is fitted in
place of the switch S, allowing
either set to be used at will,
as is shown at T in Fig. 54.

CmI.

Fig. 54- — Double-cylinder, "Make-and-
break" Ignition.

Double Cylinder, Make and Break. — This figure also shows the

S4

WIRING

55

connections for a two-cylinder engine, the only addition being
the extension of the wire from the coil to the insulated post of
both cylinders. If a magneto is used in addition, shown at M,
it is connected in parallel with the batteries, one terminal being
connected to the ground wire and the other to the three-point
switch 5. This three-point switch allows the use of either bat-
teries or magneto as desired. In operation, the batteries are used
for starting and the magneto switched in circuit after the engine
has fairly started.

Single Cylinder, Jump Spark. — The typical connections for
a jump-spark coil to a single-cylinder engine are shown in Fig.
55. The coil of the four-post type is shown at C with the two
primary binding posts B, B
and the secondary binding
posts 5, S; the spark plug is
shown at P and the insulated
post of the timer at T. The
batteries are connected in
series as shown; one battery
terminal is grounded at G on
the metal of the engine; the
other battery terminal is con-
nected to one of the primary
posts B; from the other pri-
mary post B a wire is run
to the insulated post T of the
timer. It is plain that the
primary circuit is Jcomplete
except as made or broken by
the timer T. One of the secondary posts 5 is wired to the spark
plug P and the other to a ground wire at G; thus the secondary
circuit is complete except at the sparking points of the plug.
From the previous description of the action of the coil, it will now
be seen that whenever the primary or battery circuit is made or
broken by the timer, a spark, or series of sparks, will take place
at the sparking points of the plug P.

In Fig. 55 one of the secondary posts is grounded on the engine
and a wire also runs from the post B to the timer. In place of
running both of these wires, the post S may be grounded on the
wire from post B, as in Fig. s6.

Fig. 55- — Single-cylinder Engine with
Four-terminal Coil.

S6

MARINE GAS ENGINES

As this last method of connection joins the post B and S
together, it is becoming the practice to join them inside the box

and run the lead to a single
post C, making a three-post
coil as shown in Fig. 57, the
connections being practically
the same as in the preceding
figure.

In Fig. 58 is shown the
additional connections for a
double set of batteries and a
dynamo. It is similar in
principle to that of Fig. 54.

Some types of double-cyl-
inder engines can also be fired
from a single four-terminal
coil, the wiring being as
shown in Fig. 59. The timer
a double-pointed cam, giving two
A secondary wire is
' " This

Fig. s6- — Single-cylinder Engine Fired
by Four-terminal Coil.

has a single terminal but
contacts for each revolution of the timer,
run from each secondary post to one of the spark plugs,
occurs twice in each cylinder during the cycle, and the sparks
are so timed that one fires the
charge and the other occurs at
a time when the contents of
the cylinder are not inflam-'
mable, as during the exhaust.
Thus the first series of sparks
will fire the charge in cylin-
der No. I, and have no effect
in cylinder No. 2, while the
next series will fire No. 2 cyl-
inder and be ineffective in
No. I. This method may be
used in a four-cycle engine of
the double-opposed type, or a
vertical engine with the pis-
tons moving together,

Fig.

57. — Single-cylinder Engine Fired,
by Three-terminal Coil.

The usual practice, however, is to use a separate coil for each

WIRING

57

EiG. s8. — Wiring Diagram with Magnets.

cylinder as in Fig. 60 where connections are shown for four-post

coils. For three-post coils I "~3fcp

the connections are shown *-* — • er"*^

in Fig. 61, which figures are
self-explanatory. For more
than two cylinders the con-
nections would be simply
an extension of the above.
Duplex Coils. — Where
more than one coil is neces-
sary it is usual to combine
them all in one box for sim-
pUcity and compactness.
There are many ways in
which the binding posts
may be arranged, Fig. 62 showing a common form for two cylinders.
A single ground wire is used connecting with both coils inside the
box. One battery terminal is used, the other battery wire being
grounded. There are two posts C, C for connection, one to each
post of the timer. The two secondaries S, S are each connected

/to a plug. This is a six-
post duplex coil.

Another form of duplex
coil, a five-post coil with
connections, is shown in
Fig. '63. No groimd wire is
used, one battery wire being
grounded and the other
connected to the B post.
The posts C, C are wired to
the timer and posts S, S to
the plugs.

Coils for three cylinders
are triplex coils and for
four cylinders quadruplex
coils. The posts C and S
only are increased with
the number of cylinders,

Fig.

59. — Two-cylinder Engine, Fired with
Single Coil.

the B and G connections remaining single.

58

MARINE GAS ENGINES

In Fig. 64 the wiring is shovra for a four-cylinder engine; it

is similar in prindple to
Figs. 62 and 63, the coil
box containing four units
and there being four posts
on the timer. The post G
and the ground wire may
or may not be used accord-
ing to the interior arrange-
ment of the coil.

As here shown, the cyl-
inders are fired in regular
order; as a fact, however,
this is not possible with
the usual arrangement of
cranks as shown in Figs.
77 and 78. The order of
firing for four-cycle engines
may be either i, 3, 4, 2 or

Fig. 60. — Two-cylinder Engine with
Separate Coils.

I, 2, 4, 3, and for two-cycle engines either i, 3, 2, 4 or i, 4, 2, 3,
according to the direction of rotation. To make this variation
one of the wires, either
primary or secondary, is
crossed over to the proper
post, according to the cir-
cumstances.

The usual orders of firing
for a six-cylinder engine are
I, S. 3. 6, 2, 4 or I, 4, 2, 6,
3, s ; others are possible also.

Advantages of Each Sys-
tem. — In the case of the
make-and-break system the
principal advantage is the
simplicity of the wiring and
the use of the low-tension
current. There is far less
trouble from leakage of the

Fig. 61. — Two-cylinder Engine with
Separate Three-terminal Coils.

low-tension current, and less perfect insulation is required. On

WIRING

59

the other hand, the igniter gear is apt to be rather complicated,

with many small parts
which wear and become
noisy. The moving parts
in the cylinder also are
likely to become dirty or
worn and give trouble. At
high speeds the action of
the gear is apt to be rather
erratic, as the springs may
not act quickly enough
between strokes, and even
when in good condition it is
noisy. For engines in work-
ing boats, or others which
are given Uttle care, this
system is well suited, as it is,
on the whole, less sensitive
than the jump-spark system.
The jump-spark system

Fig. 62. — Two-cylinder Engine with
Duplex Coil.

makes a very simple engine possible, as the only parts of the en-
gine are the timer and the
spark plug. No compU-
cated igniter gear is neces-
sary, requiring oiling and
care. Trouble at the
sparking points is easily
remedied by replacing the
plug with another and
cleaning up the first at
leisure. The timer also is
simple and easily kept in
good order. On the other
hand, the wiring is more
complicated and must be
most carefully done. The
current in the secondary
wires is of extremely high
voltage and special insu-

FiG. 63.

— Two-cylinder Engine, with
Five-terminal Coil.

6o

MARINE GAS ENGINES

lation must be used to prevent leakage. The coil and secondary
wiring must be protected from moisture, which is sure to cause a
short circuit. It is quite imcomfortable if the current becomes
short-circuited through any part of the body. With care, how-
ever, these points may be easily guarded against, and the jump-
spark system becomes very simple and satisfactory. While the

electrical outfit is
more expensive than
that for the make-
and- break system,
the cost of the com- '
pUcated igniting gear
is saved, so that on
the whole the cost is
probably not more
than that of the
other system. For
cabin boats where
the engine is pro-
tected from rain and
spray, the jimip
spark is well suited,
but there is no rea-
son why it may not,
with proper precau-
tions, be used, if de-
sired, in almost any
circumstances.

The separate independent coil system has many of the advan-
tages of the jump-spark system without the disadvantage of the
exposed secondary wiring. It is, however, possibly more expen-
sive on account of the separate coil for eadi cylinder. As only
the primary wiring is exposed, which is far less susceptible to
moisture, for open boats this system on the whole gives good
satisfaction.

Distributor. — This is a device by which a single coil may be
made to fire any number of cylinders, the secondary current
being sent from the single coil to each cyhnder in turn. It is
somewhat like the usual timer in appearance and action, and

Fig. 64. — Four-cylinder Engine with Four-unit Coil.

WIRING

6l

is shown in prindple in Fig. 65. A primary contact maker, C, con-
sists of a cam having as
many projections as there
are cylinders, in this case
four; these projections rub
past the insulated contact
point I, and thus make and
break the primary circuit.
There will thus be four
passages of the primary cur-
rent for each revolution of
the cam C. A single coil
is used, the wiring of which
is substantially the same as
for a single-cylinder engine
in Figs, ss and s?- One
primary wire is groimded
and the other is connected
to the insulated point /.
The secondary wire, instead
of nmning to the spark
plug, is connected to an arm
A which revolves on the same shaft as the cam C, but is insu-
lated from it. The arm A in revolving makes contact with the
plates P P P P, from which wires run to the spark plugs. It is so
arranged that whenever one point of the cam C completes the
primary circuit, the arm ^ is in contact with one of the plates
P and delivers to it the resulting secondary current. Thus the
arm A will distribute the secondary current to each of the plates
P, in turn. The number of plates, P, and the number of points
on the cam C must be the same, and equal to the number of
cylinders to be fired.

By comparing this figure with Fig. 64 the simphcity of the
wiring is evident. Although not used as much as the preceding
system in marine work, the distributor may be made to give
good results with proper care.

Wiring for Individual CoUs. — Fig. 66 shows the wiring for
four cylinders for the individual combined coil and plug described
in the previous chapter. Only the primary circuit is to be con-

FiG. 65. — Diagram of "Secondary
Distributor."

62

MARINE GAS ENGINES

sidered, as the secondary circuit is self-contained in the apparatus.

The vibrator for all coils
is shown at F; it consists
of a small magnet and
vibrator similar in opera-
tion to that of the usual
coil. One battery termi-
nal is grounded on the
engine; the other ter-
minal is coimected to
one pole of the vibrator.
From the other vibrator
terminal a wire leads to
one terminal of each coil.

H

oap

Ki

HBr-

V

V

Xf

Xf

_9

^jy^

Fig. 66. — Wiring Diagram for Individual Coils.

From the timer T, which has as many posts as there are coils, a
wire is run from each post to the remaining post of each coil. The
primary current is thus sent through the timer to each coil and
plug in turn. The wiring for this system is somewhat s imil ar to
that of the make-and-break system of Fig. 54.

The simpUcity of the wiring for the high-tension magneto is
shown in Fig. 67. Only the leads from the distributor block ter-

r — — » f — — ^ f — — >

r T— r r-f r—r

— J I — ,

, — J . —

rtmiHO ORDER- l-ft-^-S.

Fig. 67. — Wiring Diagram for High Tension Magneto.

minals to the cylinders are required, although these must be
arranged according to the order of the firing of the cylinders.
A lead from the grounding terminal to the metal of the engine
with proper switch is run for stopping the action of the magneto.

WIRING 63

Storage Battery in Connection with Dynamo. — To obtain the
best effect from either storage battery or dynamo, they should
be used in conjunction. The dynamo normally furnishes the ciu:-
rent required, the storage battery being connected into the circuit,
so as to take its share of the current, this being continuously under
charge when the dynamo is running at speed. If the dynamo
slows down or stops, the storage battery automatically takes up
the load. Referring to Fig. 68 the usual connections for such
a system are shown. The generator G is connected to the main
lead wires; the storage battery B, the lamp circuit L, and the ig-

FiG. 68. — Wiring Diagram for Dynamo and Storage Battery.

nition circuit / are connected across the leads. In normal opera-
tion aU of these draw their share of the current from the dynamo D.
As the voltage of any dynamo is dependent upon its speed of
revolution increasing or decreasing with the speed, should the
voltage of the dynamo fall below that of the battery it will dis-
charge back through the dynamo. To prevent this, a cut out C
is connected across the circuit. This cut out is an automatic
magnetic switch which remains closed as long as the voltage
dehvered by the dynamo is greater than that of the battery, but
which opens when tiie voltage of the dynamo current drops, cutting
it out of the circuit. When this takes place the circuit is stiU
complete through the battery and lamps as can be readily figured.
At A an ammeter may be put into the circuit to show whetheir the
battery is charging or discharging. A volt meter V is connected
across the circuit to show the dynamo voltage.

If in addition to the lamps and ignition circuits an electric
starting motor is used, the leads should be taken directly off the
two terminals of the battery, as much heavier wire is required for
this than for the lights and ignition.

CHAPTER Vn

On- Engines

Engines working on crude or fuel oil must be operated on
a different principle from those already considered. Gasoline
vaporizes readily and is ignited by the electric spark; kerosene
also can be ignited after being vaporized by the application of
heat; crude or fuel oil, however, being heavy and unrefined does
not vaporize at ordinary temperatures, and special treatment is
required as a high degree of heat is necessary to ignite it. To obtain
this high temperature advantage is taken of the fact that when air,
or any gas, is compressed, it becomes heated, as is noticed in the
quite common case of the tire pmnp, the barrel of which becomes
hot when in use. In order to obtain this high pressure, the com-
pression space is made as small as possible in comparison with
the cylinder volume, thus raising the compression pressiure and
consequently the temperature. All heavy oil engines make use
of this principle to a greater or less degree. The simplest of these
engines is the so-called "surface ignition" type or as it is some-
times termed the "semi-Diesel," although the latter name is not
looked upon altogether with favor.

An example of the simpler form of oil engine is shown in Fig. 69;
this engine much resembles the two-cycle gasoline engine both in
construction and operation, having the closed crank case C,
transfer passage T, and exhaust port E. No carbureter is used
and no spark plugs. Pure air is drawn into the crank case on the
up stroke of the piston, through check valves in the crank case
cover plates A; this air is compressed in the base on the next
downward stroke of the piston and transferred to the cylinder
where it is compressed on the next up stroke. In the head of the
cylinder is a bulb, plate, or plug, on tiie principle of Fig. 52, which
has previously been heated. At the proper point on the up stroke
a small amount of fuel is injected through the fuel nozzle F. The
oil strikes the hot surface, vaporizes, mixes with the air and ignites

64

OIL ENGINES 65

at or near the top of the stroke. The heat of the hot surface, com-
bined with the heat of compression, vaporizes the oil and then ignites
it. At the end of the next downward or power stroke the ejdiaust
valve is vmcovered and the burned gases escape to the mufiBer,
The incoming air scours the cylinder of burned gas and drives
out the remaining exhaust products. The bulb, or plate, retains
sufficient heat to ignite the next
charge with the aid of the heat of
compression. It will be seen from
the sketch that the head is not water
jacketed as it is necessary to keep it
as hot as possible, although a light
cover is worked over the top of it.

The speed of the engine is regu-
lated by the amount of oil fed into
the cylinder at each stroke. This is
taken care of by a special form of
pmnp with arrangements for varying
the amount fed per stroke. The
spray nozzle F is of a variety of
shapes, all of which are designed to
break up the oil into small particles
and inject it into the cylinder in a
fine spray which is most easily
ignited. The time of injection of
tibe fuel must be nicely timed ac-
cording to its quality and the pres-
sure of compression, to assure that it
will vaporize and ignite at the most
favorable point of the stroke.
Arrangements are provided in con-
nection with the fuel pump to vary F1G.69. — Section of OUEngme.
the amount of fuel fed per stroke

and also the timing of the same. As the ignition is dependent
upon both the heat of the bulb and the compression pressure,
considerable variation of the two is found. The higher the com-
pression, the lower the temperature of the bulb can be, which is
advantageous for operating reasons.

The term "semi-Diesel" has probably arisen from the fact

66

MARINE GAS EiSTGINES

that the compression is utilized in part to produce ignition, al-
though the term "surface ignition" is a stricter definition.

Engines working on this principle have the comparative sim-
pUcity of the two-cycle gasoline engine in comparison with the full
Diesel engine. For smaU powers they can be Ughter than the
Diesel, and as no fuel is injected into the cylinder until after the

exhaust port is covered, there is no
loss from this source and the econ-
omy is therefore good.

Qi!^r^'^^^TS^ii»«^i?' For starting the engine the bulb

1 iI^fiM f^E °^ other device must be heated by
" external means; a system of torches

is a common arrangement for this
purpose, although in some cases a
special form of plug is used which
can be electrically heated.

The Diesel engine makes full use
of the heat of compression, with-
out other means of ignition. The
action is in some ways similar to
that of the surface ignition type
but carried a step further, the com-
pression pressure being so great
that no hot plate or other device
is necessary. Engines working on
this principle may be either of two-
or four-cycle type, although for such
sizes as might fall within the scope
of this work the four-cycle type is
commonly used. A representative
engine of the four-cycle t3^e is
shown in Fig. 70. This will be
seen to bear some resemblance to
the four-cycle engines already described, except that no car-
bureter or spark plugs are fitted. In the pla,ce of these there is
an additional valve F in the head of the cylinder. The valves
are arranged as in sketch D of Fig. 26; the inlet valve I is actuated
by the rocker arm R, the lower end of which carries a roller which
bears oh the cam C; the exhaust valve E on the opposite side has

Fig. 70. — Diesel Engine.

OIL ENGINES 67

the same arrangement of rocker arm actuated by the cam C.
Pure air only is taken into the cylinder from the air pipe A running
along the tops of the cylinders; the exhaust valve E opens into
the exhaust manifold as usual. In the top of the cyliader head
is another smaller valve F through which the fuel is fed; this
valve is controlled by the bell crank lever B, the down turned
end of which is in contact with another rocker arm similar to R,
which is in turn actuated by a special cam on the cam shaft. The
chamber around the valve F is in connection with the fuel pump
and also an air supply which is kept at a pressure much higher
than that of the compression. In operation the air is drawn in
during the suction stroke and compressed as usual; the fuel is
fed into the chamber F in the proper amount by a small pump;
at about the time of maximum compression the fuel valve F is
opened by the cam and rockers, and the fuel blown into the
cylinder against the compression by the air pressure. The high
pressure of the compression has so heated the air in the compres-
sion space that the oil is at once ignited, after which the power
stroke and exhaust stroke follow as usual.

In this sketch, which is in approximate proportions, it will
be noted that the parts are, in comparison with the cylinder bore,
much heavier than in the gasoline engine; this is due to the greater
pressures employed and the consequent greater stresses.

It is in no way essential that this particular arrangement of
valves should be used; this has been chosen for illustration as
representing a successful type and also showing well the relation
of the various parts. It is quite customary to arrange the valves
side by side in the head with the fuel valve to one side; but in
every case it is usual to place the valves in the head as in this
way the strongest construction can be had; also the compression
space can easily be kept small as is necessary if a high compression
is to be had.

It is necessary for the operation of this type that a continuous
supply of high-pressure air be available for fuel injection, and also
a supply at moderate pressure for starting, as described later; this
is suppUed by an air compressor driven off the crank shaft at the
forward end of the engine.

Large engines are being built on the two-cycle principle. The
action as regards compression and fuel injection are the same as

68

MARINE GAS ENGINES

just described; near the lower end of the stroke, however, the
piston uncovers ports through which the burned gases escape as
in the two-cycle gasoline engine. Valves in the head then admit
a considerable volume of air which blows out the remaining gases
and furnishes pure air for the next compressive stroke.

In Fig. 71 is shown a descriptive section of an oil engine work-
ing on a slightly different principle in regard to the feeding of the

fuel. The usual inlet
■ ■ and exhaust valves V
(O) " (p) are located in the head
side by side and actu-
ated by the rocker
arm R and another
directly behind it.
The fuel feeding ar-
rangement is as fol-
lows: a sort of plug
is set into the head
which carries a fuel
valve F, which is held
up against its seat by
the spring S and a
needle valve N which
closes the small pas-
sage leading to the
fuel valve F. The
fuel enters at into
the space around the stem of the needle valve N. Below these
valves is a sort of cup C having a ring of small holes H slightly
above the bottom. The fuel valve F is depressed by the lever
L which bears against the projection T on the side of the rocker
arm R. Thus whenever the rocker depresses the inlet valve / it
also depresses the lever L and opens the fuel valve F.

The operation is as follows: on the suction stroke the inlet
valve is open and air is drawn into the cylinder, at the same time
the fuel valve F also opens and a small amount of fuel flows out
and is caught in the cup C. At the end of the downward suction
stroke both valves close and the air is compressed in the cylinder
and heated to a high temperature thereby. The pressure and heat

Fig. 71. — Section Through Head of Oil Engine.

OIL ENGINES 69

pass through the holes in the cup C to the oil within, vaporizing
a small amount which explodes, forcing the remainder of the
charge through the small holes, at about the time of greatest
compression, into the heated air in the cylinder. The charge
then burns as in the Diesel engine, the expansion and exhaust
being carried out as usual.

Regulation of speed and power is obtained by adjusting the
needle valve N to allow a greater or less flow of fuel per stroke.
The extreme simphcity of this system is apparent; no high-pres-
sure air is used for fuel injection and the fuel is nowhere imder
pressure until the time of ignition. This type is very well suited
to small powers and engines of this type are built in much smaller
sizes than in the Diesel , type, as the necessary complications of
the latter would make it improfitable to build in small sizes.

The action of the fuel in engines of the Diesel and surface
ignition types is_ somewhat different from that of gasoline in the
gasoline engine. In the gasoline engine the explosive charge is
compressed and at the time of ignition actually explodes, giving
a maximum pressiu-e several times that of the compression. In
the oil engine, however, the ignition of the fuel is more gradual
and extends over an appreciable part of the stroke; the maximum
pressure is therefore not raised greatly above the compression
pressure, and the impulse is comparatively steady over about
the first tenth of the stroke, after which the pressure falls by the
expansion to the exhaust.

Oil engines are usually built with several cylinders, as high as
eight being used; this is done to promote smooth operation and
ease of handling and avoid unnecessarily large cylinders.

CHAPTER VIII

Lubrication

One of the most important considerations in any engine is
the question of lubrication. The Ufe of the engine depends very
directly upon the efficiency of the lubrication. Insufficient lubri-
cation may cause great damage to an engine in a short time.
The pistons especially must be well oiled, as a lack of lubrica-
tion under the conditions of extreme heat which exist in the cylin-
der is likely to cause the piston to stick and finally cut the
surface of the cylinder.

Oil-cup. — The simplest means of feeding oil is shown in
Fig. 72, which is a plain oU-cup. It is screwed into place by the
thread T; the screw cap C allows it to be filled with
oil, which feeds down to the bearing through the hole
in the stem. This style of cup may be used on bear-
ings where there is no outward pressure against the flow
of oil. There is, however, no means of regulating or
stopping the flow of the oil.

Sight-feed Oiler. — For feeding oil against pressure the
sight-feed oil-cup shown in Fig. 73 is used. A section
Off glass tube G is closed at the ends by the covers C p _ ,
and B. The central tube T projects from the lower oil-cup.
cover and on its upper end has a thread on which the
cover C screws. A ring of packing is placed under the edges of
the glass tube and the cover C screwed tightly down, making a
tight joint. The threaded stopper F allows it to be filled with
oil, which flows through openings into the central opening and
down to the bearing. In the stem a piece of small glass tube H
is inserted and sight holes are placed in the sides of the stem,
through which the flow of oil may be observed. A small tube A
leads from the lower chamber to above the level of the oil, to
admit the pressure to take the place of the oil which is fed out
and prevent the formation of a partial vacuxmi above the oil,
which might finally prevent its flow.

70

LUBRICATION

71

Inside the stem T is the small plunger V, which is pressed down
by the coiled spring S. The finger lever L is pivoted to the top
of the rod V; when this lever is horizontal
the rod V is free and is forced down into
its seat below, closing the opening and stop-
ping the flow of oil. When the lever is
raised to a vertical position the square end
bears upon the cap R and raises the plunger
V, allowing the oil to feed. The cap R
may be screwed up or down on the threaded
end of the tube T, varjdng the amount
which the plunger V is raised and thus
regulating the flow of oil. Raising the
cap R increases the flow, and lowering it
decreases it; the drops of oil can be seen
through the glass H, and the cap R raised
or lowered until the drops fall at the
proper frequency. The ball inside the
lower stem is designed to prevent a sud-
den inrush of pressure, by being carried
up and closing the opening above. When
the engine is not running the lever L is
turned down and the supply stopped.
Grease-cup. — For feeding grease, the grease-cup. Fig. 74, is
used; it consists of a flat disc D which is threaded on the edge;
a cover C is threaded internally to screw on to the disc. The
cover is filled with grease and then screwed doMrn over the disc
D, the pressure forcing the grease out
through the hole and on to the bearing.
The cover can be gradually screwed down
imtil all of the grease is forced out. Grease
is used where the pressure on the bear-
ing is great, or where the viscosity of the
grease is an advantage. The use of grease
on the main bearings of the two-cycle engine
is almost universal, as it fills the space be-
tween the shaft and the bearing and pre-
vents the reduction of the base compression, by the escape of the
gas along the shaft.

Fig. 73. — Sight-feed Oil-
cup.

Grease-cup.

72 MARINE GAS ENGINES

Oiling of Cylinder. — The cylinder is lubricated by oil de-
livered on to the inner cylinder walls from a sight-feed oiler or
other device, so placed as to deliver the oil at about the middle
of the piston travel. The piston has a series of grooves turned
in its circumference, which collect the oil and distribute it over
the entire siurface. The lubrication of the piston is very impor-
tant, and on account of the high temperature only the best oil
should be used. A poor oil will burn and the resulting carbon
will deposit in the counterbore, passages, and on the spark plug,
and will become heated and fire the charge on the compression
stroke, causing pre-ignition. The carbon on the plugs also pre-
vents the passage of the low-tension current of the make-and-
break system and furnishes a path for the high-tension current
of the jump spark, thus interfering with the action of either.

Piston Pin Lubrication. — The piston pin requires, and usually
receives, but little lubrication. An axial hole is usually drilled
through the pin, with a radial hole opening into the bearing.
Oil from the cylinder wall is scraped up, and works its way along
the hole and into the bearing. It is not hkely that much oU
reaches the bearing in this way, but as the angle of oscillation of
the rod is small, not much oU is required.

Crank-pin Oiling. — This bearing does the heaviest work of
all the bearings in the engine; and it is at the same time the most
difficult to properly lubricate, especially on two-cycle engines
with the enclosed base. There are several ways of oiHng this
bearing, the most common of which is the splash system illus-
trated in Fig. 75. On the lower side of the con-
necting rod is the small scoop S, and directly over
it is the hole leading to the bearing surface.
The base of the engine is partially filled with oil,
a small portion of which is scooped up at each
revolution and carried to the bearing. This is the
most common way on small two-cycle engines,
and while it does very well, there are some dis-
advantages connected with it. The incoming
vapor, where gasoline is used for fuel, absorbs a - __T, , _

small amount of oil with each charge, and carries '^'pto Oiling?
it away through the cylinder, not only weaken-
ing the charge, but affecting the lubrication.

LUBRICATION

73

Fig. 76. — Oiling
Crank-pin.

Where the connecting rod is made as in Fig. 75 with an / sec-
tidn, one side of the / may be walled in, making a sort, of pocket
from which the oil hole H reaches the bearing.
Oil is fed into this pocket at intervals through
an opening in the crank case, or continuously
by a tube leading from a sight-feed oil-cup
above.

A very reliable way of crank-pin lubrication
for single-cylinder engines is as shown in Fig. 76,
a small hole is drilled through shaft, crank, and
pin to the surface of the pin. A grease-cup is
fitted in the end of the shaft outside the fly-
wheel. In this way the grease is fed directly to
the bearing; grease is especially well suited to
use in the crank-pin bearing on accoimt of the
high pressure upon it.

Fig. 77 shows another satisfactory form of crank-pin oiler.
It is a shallow receptacle forming a sort of ring, which is fastened
to the side of the crank. It is drawn out at one point, at which
there is a hole connecting with the axial hole in the crank pin.
Oil is delivered into the Up by the tube T from an oil-cup above.
As the shaft turns, the oil is thrown by the centrifugal force to
the circumference of the ring and finds its way to the bearing
through the hole 0. In this way a continuous feed may be had.
Multiple Sight-feed Oilers. — Where there are several sight-feed
oil-cups to be fitted they are often combined into one large reser-
voir, with several sight-feeds leading from it. This is a consider-
able saving of space and of labor, as
one filling of the reservoir serves for all.
The cylinder oilers are, however,
often kept separate, as the oil suitable
for the cylinders is likely to be dif-
ferent from that used in the bearings.
Mechanical Lubrication. — For oiling
a number of points the mechanical
lubricator shown in Fig. 78 is almost universally employed; it
consists of a rectangular reservoir containing a series of small
pumps all operated from a single shaft which is in turn driven
o£E some rotating or oscillating part of the engine. Pipes lead

Fig. 77. — Crank-pin Oiling.

74

MARINE GAS ENGINES

from each pump to the desired point. The amoimt of oil
pximped per stroke is regulated individually, and sights are pro-
vided to observe the feed.

The oiling of multi-cyUnder engines is a more complex problem.
The crank-pin bearings in moderate speed engines are lubricated,
on the principle of Fig. 75, small troughs being provided in the

base for the scoops to
dip into. These troughs
are fed by a small pump
drawing the oil from a
reservoir in the base.
The oil is picked up by
the scoops and what
does not enter the
crank-pin bearings is
spattered about in the
base, part of it finding
its way to the cylinder
walls, and to such cam
shaft or other bearings
as may be within the
base. It is usual in
slow-speed engines to
fit either a sight-feed
or force-feed oiling sys-
tem to take care of the
main bearings, with pos-
sibly a lead to each cyl-
inder wall in addition.
In small, medium
duty, high-speed en-

78. — Forced Feed OUer.

gines, the entire oiling of the engine may be taken care of by the
splash system, it only being necessary to see that the oil in the
reservoir is maintained.

High-speed engines of larger sizes, where the duty is more
severe, may be fitted with force-feed oiling throughout. The main
shaft bearings are taken care of on the principle of Fig. 76, the
oil hole, however, running the entire length of the shaft. A ring
is cut around the end shaft bearing, registering with a hole into the

LUBRICATION

75

drilled shaft as in Fig. 79. The oil is delivered to this opening
under a considerable pressure and in such volume as to flow
through the hollow shaft and force out at each bearing, return-
ing to the reservoir.
A mechanical oiler
may be used in ad-
dition, to supply such
bearings as may not
be exposed to the oil
spray. In connection
with this system some
form of gauge or in-
dicator must be fitted
to assure a continuous
supply of oil, as a
failure of the supply with this sytem is much more serious than
with the other systems where there is a greater surplus.

Oil engines cannot be lubricated by the splash system, as the
air in the base would carry a portion of it into the cyhnders with
liability to pre-ignition and other troubles. One of the several
forms of forced feed is therefore adopted, the mechanical oiler
having the preference.

Fig. 79. — Oaing Through Bottom Crank Shaft.

CHAPTER EX

Mxjltiple-Cylindee Engines

Engines of more than one cylinder are necessary and desirable
for a number' of reasons. It is evident that when the limit of
power of a single cylinder is reached, more cylinders must be
added according to the power desired. Even when this considera-
tion does not apply there are others which make at least two
cylinders desirable, even for moderate power. In a single-cylin-
der engine the parts must be relatively heavy, and the stopping
and starting again of these parts at each end of the stroke causes
a throw which is felt as a vibration. A two-cylinder engine may
be so arranged that one set of working parts is moving upwards
whUe the other is moving downwards, thus neutralizing the throw
of each and practically stopping the vibration. The impulses in
the several cylinders may be made to occur at different points
in the revolution, thus reducing the interval between the impulses.
Thus in a two-cylinder engine there will be twice as many impulses
in each revolution as in the single cylinder. This gives a more
even turning effect on the shaft and, in consequence, a steadier
running engine; as the interval is shorter between the impulses
a Ughter flywheel can be used. The weight, power for power, of
a double-cylinder engine is less than that of a single-cylinder,
owing to the Ughter weight of the flywheel and other parts. In
the case of the disablement of one cylinder there is the possibility
of running on the remaining cylinder or cylinders.

While for marine work single-cylinder engines are built as
large as eight or ten horse-power, they are so large as to be rather
cumbersome and suited only to working boats. For use in pleasure
boats, engines should be built jwith multiple cylinders when above
five horse-power. There are several makes of engines with double
cylinders as small as three horse-power, which, as to weight and
reUability, are superior to those of a single cylinder.

The original method of constructing a multiple-cylinder engine
was to couple two or more single engines togetlier with couplings

76

MULTIPLE CYLINDER-ENGINES

77

up a great

of

Fig. 8o. — Arrange-
ment of Cranks on
Two-cylinder,
Two-cycle Engine.

between. This is a cumbersome method and takes
amount of space, and is seldom used now.

Several combinations may be made in the arrangement
the cyUnders, those for the two-cylinder engine
being shown in Figs. 80, 8i, and 82. Fig. 80
is for two vertical cylinders with the cranks
opposite, one set of parts moving upwards
while the other moves downwards; the parts
are thus practically in mechanical balance.
When this arrangement is used in a two-
cycle engine, the impulses or power strokes
will be regularly distributed, with two power
strokes for each revolution. When applied
to a four-cycle engine the impulses will not
be regularly distributed, but will occur on
adjacent strokes with an interval of two
strokes, or one revolution, before the next two.

In Fig. 81 the cranks are both on the same side of the shaft and
the working parts move together. This arrangement is in very
bad mechanical balance, and coxmterweights on the opposite
ends of the cranks are required to balance the weight of the work-
ing parts. This arrangement would not be used in a two-cycle
engine, but in a four-cycle engine so distributes the impulses
that they occur regularly, one during each revolution. As this
arrangement is used to some extent it is considered that the poor
mechanical balance is more than offset by
the advantage of the regularly occurring im-
pulses.

Fig 82 shows an "opposed" motor, the
cylinders being placed horizontal, on opposite
sides of the shaft, and travel in opposite
directions, both moving towards or away
from the shaft at the same time. The parts
are in almost absolute mechanical balance.
Fig. 81. — Arrangement When this arrangement is used in a two-cycle
of Cranks °^ Jj°-^ engine both cylinders act together, the im-
pulse occurring in both cylinders at the same
time. In a four-cycle motor the impulses

JJU

cylinder,
Engine.

on
Four-cycle

occur regularly, once during each revolution. This arrangement

78

MASINE GAS ENGINES

ET

has some advantages; it lies very low in the boat, and may even
be placed under a transverse seat; wlule for
auxiliary work it is particularly convenient as
it may many times be placed under the stand-
ing room floor where there is little head room.
Three-cylinder engines are arranged as in
Fig. 83, with the cranks spaced on thirds
around the circle, or 120 degrees apart. This
arrangement gives a good mechanical balance,
and a regular distribution of the impulses in
either the two- or four-cycle engine. Although
the three-cylinder engine is httle used in auto-
mobile work, it is quite popular in marine
work.

Figs. 84 and 85 show the arrangement of the

cranks in four-cyhnder engines. The former

. — Arrange- is the usual arrangement for the two-cycle en-

"(\S'^^^^" &^^'> '-^^ cranks of cylinders i and 2 are oppo-

Opposed gj^g^ g^g j^j.g ^Yso those of cyhnders 3 and 4, with

the two pairs at right angles. The cranks are
thus spaced equally around the circle as shown in the small circle
at the right. With this arrangement the parts are well balanced,
and the impulses occur at equally spaced intervals, each cylinder
coming to the top of its stroke and receiving its impulse in turn.
There are four impulses for each revolution.

The arrangement for a four-cylinder, four-cycle engine in Fig.
85 differs in that the two
pairs of cranks are in the
same plane. This ar-
rangement is made neces-
sary by the fact that the
four-cycle engine has an
impulse only on alternate
revolutions. The posi-
tions of cranks 3 and 4
may be reversed, bringing
I and 3 up and 2 and 4
down, but the former is
considered the better arrangement,

Fig. 82.
ment
for
Engine.

m

J "=M=gig=8Jff= ^^i^

ft •> 9

Fig. 83. — Arrangement of Cranks for Three-
cylinder Engine.

This arrangement gives four

MUrTrPLE-CYlINDER ENGINES

79

impulses for two reyolutions, or two impulses for each revolution,
occurring regularly.

It will be readily seen that in any engine of more than two
cylinders, while one cylinder is on the compression stroke, one of

/^s

> \

A fc » *•

Fig. 84. — Arrangement of Cranks on Four-cylinder,
Two-cycle Engine.

the other cylinders is receiving its impulse; the work of compres-
sion is thus overcome more directly, and the duty removed from
the flywheel, which may thus be made lighter.

For higher powers or for reasons of lightness and better
balance, six, eight, or even twelve cylinders may be used. Six-
cylinder engines consist of two imits like Fig. 83. Eight cylinders
are disposed in two ways,
in the simpler they are set
in tandem, like two units
of Fig. 85, but with the
planes of the crank of one
set at right angles to that
of the other. This arrange-
ment makes a long engine
although accessible. When
saving of space is desir-
able, the V type shown in
Fig. 86 is adopted. This
may be likened to two
four-cylinder engines side by side but inclined at a right angle,
using only one shaft; the connecting rods of opposite cylinders being
attached to the same crank throw. The shaft is the same as that

9. 3> 3 ^

Fig. 83. — Arrangement of Cranks on Four-
cylinder, Four-cycle Engine.

8o

MARINE GAS ENGINES

-r-^

Fig. 86. — Arrangement of Crank
for Eight-cylinder Engine.

of Fig. 85 but with two rods taking hold of each pin. This arrange-
ment allows a very short engine, which is also well balanced for
high-speed work., Consideration will show that for even timing
the planes of the two sets must be at a right angle.

Twelve-cylinder engines are made
up of two six-cylinder units inclined
as above, but on account of the
extra cylinders the planes of the
two sets are at an angle of 60°.

While the first multiple-cylinder
engines were 'built by coupling to-
gether two or more single engines
on a common bed, this method is
bulky and clumsy, and is now little
used. The usual method is to pro-
vide a common base, to which the
several cylinders are bolted, bring-
ing them much nearer together and making the engine much
more compact.

The simplest form of two-cylinder engine is shown in Fig. 79,
it is made up of two cylinders like that of Fig. 12, bolted to the
one-piece base. Provision must, of
course, be made to keep the crank cases
separate, which is accompHshed by a
special center bearing between the two
cranks. This particular engine is of the
two-port type, with two vaporizers, V, V,
joined to a common fuel pipe F. The
water pump is at P, the discharge W
from which is divided and branches to
each cylinder. The cooUng water outlet
is at /. It will be seen that the pipe W
and the outlet / are in the middle of the
pipe leading to the cyUnders; this is „^^?- 87. — Arrangement of
S ^ . .° , . 1 iT. 4.1. 1. Cranks for Twelve-cylmder

done to mamtam an equal path through Engine.

both cylinders and assure each obtaining

its share of the cooling water. The igniter gears for the make-and-
break spark are shown at N, N and are botti connected by rods to
the lever L, so that the time of ignition may be kept the same in

MULTIPLE-CYLINDER ENGINES

8i

Fig. 88. — Two-cylinder, Two-cycle Engine.

both cylinders. This engine may be fitted with a single vapo-
rizer, or carbureter, in the
same manner as Fig. 89, if
a check valve is fitted in the
pipe at the entrance to each
crank case. Both cylinders
exhaust into the common
exhaust pipe E. This is a
very simple way of building
a two-cylinder engine, as
nearly all of the parts are
the same as in the single-
cylinder.

Fig. 89 shows a two-
cylinder engine of the three-
port, jump-spark t3^e. A
single carbureter C is used
with a branch pipe leading
to the third port of each
cylinder. The suction to the water pump is at S, the discharge
being through the pipe D leading to the cylinders on the opposite
side of the engine. The outlet from the cylinders is at W. The

timer T has a terminal for
each cylinder and is similar in
construction to that of Fig. 41.
At 0, O are oil-cups feeding
the crank pins by means of
ring oilers Uke that in Fig. 42.
Similar oil-cups on the oppo-
site sides of the cylinders feed
oil onto the bore of the
cylinder.

In the engine shown in Fig.
90 the two cylinders are com-
bined in a common casting.
This engine is of the two-cycle
three-port type. The inlet I,
frorft the carbureter, opens^
into a chamber cored in the casting, with which the third ports

Fig. 89.

- Two-cylinder, Two-cycle
Engine.

82

MARINE GAS ENGINES

.90,

- Two-cylinder, Two-cycle
Engine.

communicate. The exhaust E opens from a similar cored chamber.

The pump i* is in this case a rotary pump driven by the sprocket

chain B and delivering
fls H» water through the pipe

'^ — D, which, after circuk-

ting around the cylin-
ders, overflows at W.

The two-pole timer is
at T. There are some
advantages of this me-
thod of construction as
it allows a very compact
engine and also saves
some weight. In the
event of trouble with one
cylinder, however, both
must be disturbed, and
in case of damage to one
cylinder the entire casting
is spoiled, so that repairs

are likely to be more expensive with this type of construction.
In Fig. 91 a usual type of two-cylinder four-cycle engine is shown.

The parts are lettered as

before. The cam shaft is

contained inside the base

and, in additionto driving

the valves, drives the two

igniters iV, iV, and the

pump P. The discharge

from the pump is piped

to the cylinders on the

further side, and the over-
flow W is piped down

into the common exhaust

pipe E. The inlet pipe

/ from the carbureter C

branches to each cylinder.

In a multiple-cylinder engine, great care is taken to have equal

distances from the carbureter to die inlet of each cylinder, as only

91. — Two-cylinder, Four-cycle Engine.

MULTIPLE-CYLINDER ENGINES

83

in this way can all cylinders be made to take the same amount
of mixture.

In other than small engines it is customary to provide a sub-
base B, either of cast iron or of angle iron, which carries the engine
and also some form of reversing gear. This subbase keeps all parts
in line and has flanges for bolting down to the bed in the boat.

Three- or four-cylinder engines are of the same general design
with the additional cylinders added. In the case of the engine
shown in Fig. 90, one of three cyhnders has the three case in a
single casting, while the four- or six-cylinder is composed of two
or three two-cylinder units.

Fig. 92. — Two-cylinder "Opposed" Engine.

In Fig. 92 is shown the two-cylinder opposed motor having
the arrangement of cranks in Fig. 75. The carbureter C is
attached to the inlet pipe / which branches to the two cylinders;
it should be noted that this inlet pipe leads to a point midway
between the cylinders before branching in order to keep equal
lengths of pipe to each. The exhaust from each cylinder is at
E, E. The timer T is on the end of the cam shaft, the gears
driving which are inside the casing, at K. The pump P, of the
rotary type, is also driven from the cam shaft by an independent
gear or sprocket chain. The discharge from the pump branches
at D to each cylinder, entering on the lower side and flowing out
at W, W. The fljnvheel F is on the further side of the engine. In
the heads of the cylinders are the spark plugs 5, S. The several
flanges are shown, by which the parts are bolted together.

84 MAIONE GAS ENGINES

A four-cylinder engine of a style similar to Fig. 21 is shown
in Fig. 93. The inlet and exhaust valves are on opposite sides
of the cylinder and are operated by independent cam shafts driven
by the gears B and C respectively. These two gears are driven
from the crank shaft through the gear A on the crank shaft and
the idle gear G. The idle gear G is inserted on account of the
distance between the crank ^af t and the cam shafts, to gear direct

necessitating unduly large
gears. The inlet valves are
on the left of the engine,
their chambers connecting
with the inlet manifold /
which is bolted to the sides
of the cylinders. The car-
bureter V is attached to
an elbow at the middle of
the inlet manifold. A
similar manifold on the
opposite side of the engme
connects with the exhaust
chambers. The cylinders
are separate and are bolted
to the base by the flanges
shown.

The small gear D, driven
Fig. 93. — Four-cylinder, Four-cycle Engine, by the gear B, drives the

magneto M, and a similar
gear E on the opposite side drives the plunger pump P. The
cooling water leaves the cyhnders by the pipe / which is bolted
along the tops. The pump P delivers the water to the cylinders
through a similar pipe on the farther side of the engine. At is
a forced feed oiler as already described.

In place of the usual flanges for carrying the engine, the cross-
bearers F, F, F are provided. The gears are covered by a plate
which, together with the case already in place, entirely encloses them.
Starting Arrangements. — While small engines are easily started
by a crank or even by the rim of the flywheel, large engines must
have some more powerful means. For this purpose a ratchet
wheel is fitted on the end of the shaft outside the flywheel and a

MULTIPLE-CYLINDER ENGINES

8S

long lever used for turning the engine over. The ratchet allows
the engine to run away from the lever when it starts.

In place of the compression relief cocks which are fitted on the
small engines, large multi-cylinder engines, which are designed
to be started by hand, may be provided with a device to lift the
exhaust valves sUghtly from their seats, thus reducing the com-
pression. This is accompUshed by a small lever and supple-
mentary cam, the valves being allowed to seat as soon as the
engine starts.

In the more refined engines of the medium duty type, used in
pleasure boats, electric starting systems are now quite commonly
used. The system consists of a motor connected to turn the
engine over by current from a storage battery, the battery being
kept up to charge by .

a generator driven by "' TOVi Ji „ i a O

the engine. The motor f*-*—

and generator may be
separate vmits or may
be combined in a single
unit acting as either
motor or djTiamo. In
the latter case the
motor generator is
geared direct to the
engine shaft as in Fig.
94 and runs continuously. Where two instruments are used the
generator is geared direct and runs aU the time, while the starting
motor is so arranged as to run only when it is required. The
former is termed the single-unit, and the latter the two-unit
system. The generator is run off either the cam shaft or the main
shaft by gears or silent chain; the starting motor, when a separate
machine is usually arranged to connect with a gear cut on the
rim of the fi3rwheel. The end of the motor shaft carries a small
gear which meshes with the gear on the flywheel rim; normally
the gear stands at one side out of mesh, but when in use is drawn
into mesh by mechanical or electrical means and automatically
shifted out of mesh when the engine has started.

In the case of large, multiple-cylinder engines, notably those
using oil fuel, compressed air is used for starting. A reservoir of

Fig. 94. — Four-cylinder Engine.

86 MARINE GAS ENGINES

compressed air is maintained which is admitted to two or more
of the cylinders, turning the engine until the other cylinders take
up the cycle. This is accomplished by a sort of revolving dis-
tributing valve, working in the same manner as the timer, which
passes the air to the proper cylinder in turn, or, as is done in
engines of the Diesel type, by means of a separate set of valves
on the starting cylinders, worked by special cams on the cam
shaft, which may be thrown into or out of engagement. The
pressure in the air tank is maintained by a pump or air com-
pressor. In the case of small oil engines the air compressor is
usually operated by means independent of the engine, but in
larger engines the direct connected compressor is fitted for this
purpose.

In Fig. 96 the extra lifters for the air-starting valves are shown
just to iJie right of the rocker arms of the middle two cylinders.
Extra cams on the cam shaft can be moved into place to operate
these lifters and at the same time the cams are moved from under
the fuel valves, leaving them closed while the air is on. The shift-
ing of the cams is accomplished by fingers extending from the
shaft just below the cam shaft, operated in turn by tJbe vertical
lever. All starting systems employ one or a combination of the
above principles.

Fig. 94 shows a sketch of a most refined type of engine; the
cylinders are cast in one block and all the moving and working
parts are entirely enclosed, including flywheel and reverse gear.
Covers, easily removable, are provided for inspection and adjust-
ment. Plates H, H also cover the valve tappets. This form of
construction is very cleanly as no oil is thrown and dirt is kept out
of the bearings. A single-unit electric starter shown at S is geared
to the shaft by a silent chain. Provision is made for fitting a
double-unit system, in which case the generator is placed as above
and the starting motor geared with teeth on the rim of the flywheel,
the shaft extending into the front gear case through the hole D.
The spark and throttle controls are shown at A. Arrangements
are also made for the insertion of a hand-starting crank at the
front of the gear case.

Fig. 95 illustrates the general appearance of a heavy oil engine
of two cylinders; separate crank cases are provided in order to
assure tightness and the bearing between each two cylinders is

MULTIPLE-CYLINDER ENGINES

87

readily accessible. This construction is not, however, essential,
as some makes are built with separate cyUnders and a common
base, the compression being obtained by partitions in the base.
The oil pump P is directly behind the flywheel; fuel pipes leading
from it to the head of each cylinder. The governor G acts directly
upon the fuel oil pump, which is also controlled by the hand
gear H. At W is the usual water pump worked off an eccentric
on the shaft. The reversing gear R is set into the same bed with
the engine to assure the alignment. The mechanical oiler is
in this particular case supported on the reverse gear, and operated
by the lever L, but it >^^

is usually disposed on J^^^

some part of fiie crank 2 J ?— *^

case or cylinders;
small pipes, notshown,
lead from this oiler to
the main bearings and
cylinder bores. The
exhaust chamber M
is disposed on the
back of the cylinders.
The same construction
is followed in engines
having a greater num-
ber of cylinders.

An example of a
small four-cycle Diesel engine with four cylinders is shown in
Fig. 96. It has the usual outlines of the gas engine, with the
addition of an air compressor at the after end. The valves
are in the sides of the head as in D of Fig. 26, operated
by the rocker arms shown. The sketch shows the intake side of
the engine, the air supply pipe A running along the tops of the
cylinders. Two rocker arms are shown for each cylinder; the
left-hand one actuates the admission va^ye, and the right-hand
one the fuel valve, through a bell crank lever which is behind
the air duct. The tops of the fuel valves can be seen at F above
the air duct. The cam shaft is shown plainly, extending from the
case G alongside the crank case. At the front of the cylinders
is the fuel pump P, which in an engine of this design is of the

Fig. 95. — Two-cylinder Oil Engine.

88

MARINE GAS ENGINES

greatest importance as practicaUy the entire regulation of the
speed and power is dependent upon it. The air compressor C

Fig. 96. —Four-cylinder Diesel Engine

IS run off an extra throw built in the crank shaft; its purpose
IS to supply air for starting and fuel injection. At O is the
mechanical lubricator, driven by chain from the cam shaft The
water pump W is driven from the main shaft as usual. Engines
ot this type are built up to eight cylinders.

CHAPTER X

Reversing Mechanism

Unlike the steam engine, the gas engine of the usual design
has no ready means of reversing. Although most two-cycle
engines and some four-cycle engines will run equally well in either
direction, the means of accomplishing it are slow and not always
certain. Some few engines have permanent means for reversing
them, which work very well, but the majority of engines must
be stopped and started in the opposite direction. It is possible
to reverse a two-cycle engine by a proper manipulation of the
timing of the spark, as is explained under the handling of engines;
it cannot, however, be relied upon in emergencies. This fact,
and the fact that most four-cycle engines can be run in one direc-
tion only, necessitate the adoption of some form of independent
reversing device. Small engines fitted in light boats may con-
veniently run without any reversing gear, but for engines of more
than five or six horse-power some form of reversing gear should
be fitted. One of the greatest advantages of the independent
reverse gear is that it allows the engine to be rtm free of the pro-
peller and shafting, thus making the engine easy to start.

Reversible Propeller. — The simplest form of reversing device
is the reversing propeller, as shown in Fig. 97. It is fitted with
a mechanism for changing the angle of the blades, causing them
to act in the opposite direction without changing the direction
of rotation of the shaft. In this case the propeller shaft S is made
hollow and is fastened to the hub JB of the propeller. Inside of
the shaft is the round rod R, which is enlarged and made square
inside the propeller hub. On one side of the square end of the
rod is a diagonal groove A. The blade B has a collar C, which
fits under the projections D, D of the hub> holding the blade in
place while allowing it to turn. The face of the collar C bears
evenly on the flat of the rod R, so that all parts are held snugly in
place. On the under face of the collar C is a pin P which pro-
jects down and fits into the slot A. If now the rod R is moved

89

90

MARINE GAS ENGINES

along the shaft, the pin P will slide in the slot A and thus turn
the blade. When the rod has been moved into its extreme right-
hand position, the pin P will have moved to P'j having swung
across the center Une into the opposite position and caused the
blade to take an opposite angle to its former one and to exert its
force in the opposite direction. At some point about midway
between these two the blade will be practically at right angles
to the shaft and will turn idly without exerting any force. By

turning the blades sHghtly
either way a sUght force mil be
exerted; thus any speed may
be obtained from full speed in
either direction down to noth-
ing. This allows the boat
to be readily maneuvered, and
even stopped entirely, without
touching the engine. The
other blade is operated in the
same manner by a slot and pin
on the opposite side of the rod
R so that both blades move
together. On the inboard end
of the rod R is an attachment
connected with a lever for mov-
ing the rod in and out.

This form of propeller is a
cheap and fairly satisfactory
way of controlling the speed
where the power is small. If
properly constructed it may be

Fig. 97. — Diagram of Reversing
Propeller.

made nearly as strong as a soUd wheel; many reversible propellers
on the market to-day are, however, poorly designed and con-
structed, and care must be taken in the selection of this type of
propeller. It should also be noted that the shape of the blades
is correct for one angle only, and for all others is more or less
imsuited; for this reason, unless the correct position happens to
be hit upon for the full speed position, a certain loss of power is
apt to follow. A reversible propeller is thus likely to waste more
power and give less speed than a solid propeller. The usual

REVERSING MECHANISM

91

reversible propeller should hardly be used for over ten horse-power;
above this some form of mechanical gear should be fitted.

Reversing Gears. — For the present purpose reversing gears
may be divided into two general classes, those using bevel gears
and those using spur gears. Fig. 98 shows a diagram of a bevel
gear reversing device. The engine shaft E is prolonged and
carries on its end the large bevel gear A. The propeller shaft P
carries a similar gear B. The frame F encircles the shaft E and
has bearings carrying the bevel pinions C, C, which mesh with
the gears A and B. The frame F
has two locking devices, one of
which locks it to the shaft E and
causes both to revolve together;
the other device locks it to the
engine frame, holding it stationary
wMle allowing the engine shaft to
revolve.

Suppose now that the frame F
is locked to the engine shaft and
turning with it; the gears A and
C, C are locked together rigidly,
and drive the gear B in their own
direction. The whole mechanism
is thus locked together, and the
shafts E and P turn in the same
direction. This is the forward
speed. If now the frame be re-
leased from the shaft E and locked to the engine bed so that it
cannot turn, the gears C, C will be brought into action. If
the shaft E and gear A continue to revolve in the direction as
shown by the arrows, a Uttle consideration will show that the
gears C, C turn in the direction of their arrows, turning gear B
and shaft P in the direction of its arrow, which is opposite to that
of the shaft E. This is the reverse motion. If now the frame
F is left free, the shaft E may turn and the gears C, C will roll
idly upon the gear B without turning it and the shaft P remains
stationary. The frame F also revolves idly with the gears C, C.
This is the neutral gear which allows the engine to be started
without turning the propeller. As the gears A and B are of the

Fig. 98. — Diagram of Bevel-gear
Reversing Gear.

92

MAEINE GAS ENGINES

same size, the motion will be transmitted from one to the other
by the gears C, C at the same rate; that is, the shaft P will always
turn at the same rate as E, so that the reverse speed is the same
as the forward speed.

A reversing gear using spur gears and pinions is shown in Fig.
99. On the end of the engine shaft £ is the spur gear A, and on
the end of the propeller shaft P is a similar but somewhat larger
gear B. The case G encloses these gears
and has bearings for the shafts E and P.
A bearing on the side of the case G carries
the pinion D, which is in mesh with the
gear A. The pinion C, also carried by a
bearing in the case, meshes with the pinion
D and also with the gear B, thus forming
a complete connection between gears A
and B. As before, the case G is arranged
to be either connected to revolve with
shaft A or to remain stationary. Suppose
now that the case is made to turn with the
shaft E; this locks the gears inside of the
case and drives A and B together, thus
driving the propeller shaft in the same di-
recljon as the engine shaft. Suppose now
__ that the case G is released from the shaft

FiG.99.-DiagramofSpur-^'A'''^.^°'=^^'^J? the engine frame so as
gear Reversing Gear. i^o^ to turn. The mside gears then come
into action, the gear A driving the pin-
ions D and C and thus the gear B and the propeller shaft, but
in a direction opposite to that of the shaft A. This may be
followed out by referring to the arrows on the gears.

If the case G is left free, while the shaft E turns, the pinion C
will simply roll around on the gear B without turning it, but
revolving the case G slowly. The engine can thus run idle. While
in the bevel gear mechanism both shafts always turn at the
same rate, it is not so in this case, owing to the difference in size
of the gears A and B. This difference is necessitated to accom-
modate the idle gear D. Since the gear B is larger than the gear
A, it will not turn as fast, so that the speed of the propeller shaft
when reversed will be considerably less than that of the engine.

REVERSING MECHANISM

93

In practice the reverse speed is about three-fourths the ahead
speed. This difference is of

V^//////////////W////^

FiG.ioo. — Diagram of Spur-gear
Reversing Gear.

Uttle account in actual run-
ning, as it is seldom necessary
to have extreme power in re-
versing.

In the actual gear the pin-
ion Z? is placed to one side so
that the gear A is relatively
larger than shown.

Another form of gear,
shown in Fig. loo, requires the
use of individual clutches. The
engine shaft E is connected by
an internal friction clutch with
the gear ^, and propeller shaft
P with the gear 5 in a similar manner. At K is another clutch
connecting shafts E and P. For forward gear the clutches to the
gears A and B are disconnected and the clutch K is thrown in.

For the reverse gear the
clutch K is thrown out
and those to gears A
and B are connected,
the driving taking place
through the gears A, C,
D, E, B.

In Fig. loi is shown
a section of a reversing
gear employing bevel
gears. Inside of a pro-
longation of the case G is
the internal friction band
F, which is fastened to
the arm S, which is in
turn fastened to and
driven by the engine

„ -a ^ -D ■ n shaft E. The band F is

FiG.ioi. — Bevel-gear Reversing Gear. u i c ^x.

normally clear of the

case, but by means of a tumbler T it may be expanded to grip

94

MARINE GAS ENGINES

the inside of the case and cause it to revolve with it. At F is a
tapered collar, which sUdes on the shaft E. The lever L, on
the end of which is the tumbler T, normally bears against the
shaft, but as the collar V is moved to the left it rides up on the
taper and thus turns the tiunbler T and opens the friction F.
Another friction band /, / encircles the drum and is secured to
the frame of the engine. It also is normally clear of the drum,
but may be drawn together by the wedge W so as to clasp the
drum. The lever L, which is pivoted at the foot, is provided
with a collar which fits into the groove in the sliding block V. The
wedge W also has a rod attaching it to the lever L. The rods
and levers are so adjusted that as the cut shows both friction
bands are free, and the shaft E can revolve freely. If the lever
H is moved to the right, the lever L is moved outward, turning
the timibler T and opening the friction F for ahead gear. If the
lever H is moved to the left, the wedge W is drawn in, tightening
the band /,/ and causing the drum to
remain stationary for reverse gear. The
gears ^, B, C, C are the same in action as
already described in Fig. 98.

In Fig. 102, is shown a spur-gear re-
verse similar in principle to that of. Fig.
99, but using an internal gear and a cone
friction. The engine shaft E carries the
spur gear A; a shallow case D, which is
free on the shaft A , carries the pinions C, C,
of which there are several, to distribute
the wear. The case has a conical fric-
tion surface F on the inside of the rim
and a parallel friction surface on the out-
side. The propeller shaft P is fastened to
a drum H, which on the outside of its rim
has a conical friction surface/,/, and on
the inside has an internal gear B which
is in mesh with the pinions C, C. A ring
R, fitting into the grooved collar and con-
nected to the lever L, allows the shaft and
drum to be moved in or out. The friction
band K is tightened by a wedge, holding the drum stationary

Fig. 102. — Spur-gear Re-
versing Gear.

REVERSING MECHANISM

95

when desired. If the shaft P and the drum H are moved to the
left, the conical frictions F and/ will be brought into contact, lock-
ing the gear and driving both shafts together. If the band K
be tightened, holding the drum D stationary, the gears will come
into action and the shaft P will reverse. As shown in the sketch,
both frictions are free and the engine turns idly. In this gear
the entire propeller shaft and propeller must be moved in shift-
ing the gear, which movement must be allowed for.

In another form of gear, shown in Fig. 103, the engine shaft E
carries a sprocket and chain C; the
drum D carries the gear A to which
is attached the other sprocket.
The propeller shaft carries the gear
B which is similar to .4. At F F
is the go-ahead friction band as
before, which is expanded by the
levers L and conical sliding piece G.
At /,/ is the astern friction band
which is tightened by a short lever
and circular wedge at W. These
are operated by the hand lever H
as before. The gear as shown is in
the neutral position. For ahead
motion the lever H is moved to the
left, throwing in the ahead friction,
while for astern motion the lever H
is moved to the left, throwing out
the ahead friction and tightening
the astern friction band.

A spur-gear clutch with a different form of friction is shown
in Fig. 104. The case with the gears and the reversing friction are
similar to those already described. For the go-ahead friction,
however, a series of discs is used. These discs are fastened alter-
nately to the shaft E and to the case. Those D, D, D fit on the
squared part S of the shaft and therefore turn with it, while those
d, d are held in place on the drum by the splines T, T, which fit
into corresponding grooves in the discs. All the discs are free to
move along the shaft. The small levers L, L bear against the outer
disc D and the collar K on the shaft. By means of the conical

Fig. 103.— Reversing Gear, using
Sprocket Chain.

96

MARINE GAS ENGINES

sliding piece V the levers L are pressed outward, bearing against
the disc D and pressing them all closely together. There is thus
a friction surface over all of each disc, giving a very powerful
and simple go-ahead friction. The reverse friction and the hand
lever H operate the same as before. This form of friction is well
suited to high powers, on account of its simpUcity and the large

surface. The nimiber of discs is
regulated according to the power
to be transndtted.

The principal requisites of any
reversing gear are: The gears
should be in mesh at all times to
avoid the danger of stripping them
when the power is thrown in sud-
denly. The gears shovild rim in oil
to reduce friction and wear. It
must be so arranged that both
frictions cannot be put in action
together, which would damage the
gear. The gears should be in ac-
tion only in the reverse motion.

Reversing Engines. — As before
stated, the majority of two-cycle
engines iwill run equally well in
either direction according as they
are started. The engine may be
reversed while in motion, as fol-
lows: the ignition current is broken and the engine allowed to
slow down, the spark is retarded so as to take place well over
on the up stroke. After the engine has slowed down sufficiently,
the igniting current is again switched on, but at the moment
when the piston is ascending. The resulting impulse prevents
the piston reaching the top of its stroke and sends it down in the
reverse direction. The spark is then returned to the proper
running position, and the engine continues to nm. While this
can usually be done, it is not always to be depended upon, and is
moreover a considerable strain on the crank shaft of the engine.
The engine shown in Fig. 90 has an automatic device for
accomplishing this purpose. The lever R is pivoted on the rear

Fig. 104. — Spur-gear Reversing
Gear, with Disc Clutch.

REVERSING MECHANISM 97

face of the fljrwheel; on the front end of the base is a ring which
is insulated from the base, but is connected by a wire with the
timer contact. The timer contact is so arranged that when
the spark is advanced or retarded to the utmost, the contact is
broken by an insulated segment. While in rotation, the arm R
is thrown out by centrifugal force in opposition to a spring. To
reverse the engine it is oidy necessary to retard the spark as far
as possible, thus breaking the circuit and allowing the engine to
slow down. When it has slowed down to the proper point the
spring draws the arm R inwards, until it finally bears on the
insulated ring and remakes the circuit. This causes ignition to
take place again, but as the spark has been retarded the ignition
occurs on the up stroke, sending the piston down in the reverse
direction. This device operates very satisfactorily and surely,
as it allows the engine to slow down to the proper speed before
reversing, and thus also lessens the strain on the parts.

Four-cycle engines are made reversible by fitting a double set
of cams, either set of which may be brought into action by shifting
the cam shaft in its bearings, or similar means. In some Diesel
engines two cam shafts are used, either of which may be brought
into use.

CHAPTER XI

Propellers

Of the many problems which the marine engineer or launch
builder has to deal with, the question of propellers is one of the
most difficult and in some respects the least satisfactory. The
conditions are so varied that calculations are difficult and not
always satisfactory. The size and pitch of a propeller for any
given purpose are very largely determined by experiment and
from experience with other propellers.

The principal characteristics and definitions regarding the
propeller are as follows:

Diameter. — The diameter is the diameter of the circle described
by the tips of the blades.

Pitch. — The pitch is the distance which the propeller would
advance in one complete turn, considering it to be a portion of
a screw turning in a soUd medium.

Pitch Ratio. — This is the ratio of the pitch to the diameter
and is obtained by. dividing the pitch by the diameter. Thus if
a 24-inch wheel has a pitch of 30 inches, the pitch ratio is 30 -^ 24
= 1.25.

Disc Area. — This is the area of the circle swept by the tips
of the blades; thus the 24-inch propeller above will have a disc
area of J X 24 X 24 X ^7^ = 452 square inches.

Expanded Blade Area is the actual area of the faces of the
blades.

Surface Ratio. — The surface ratio is the ratio of the blade
area to the disc area, and is obtained by dividing the blade area
in square inches by the disc area, also in square inches. If the
blade area of the 24-inch propeller were 150 square inches the sur-
face ratio would be 150 -5-452 = .33.

Slip. — The slip is the difference between the distance which
the propeller actually advances per revolution and the distance
which it would advance if it were turning in a soUd medium.
For example, if the pitch of a propeller is 30 inches, but it only

98

PROPELLERS 99

advances 24 inches per turn, the slip is 30 — 24 = 6 inches per
turn, or in per cent, as it is usually figured, 6 -=- 30 = 20 per cent.
As a further example, suppose a propeller of 30-inch pitch, turning
306 turns per minute, drives a boat at 6 miles per hour. The
nominal advance of the propeller would be fS X 300 =750 feet
per minute. The advance of the boat in feet per minute is ^^§^^
= 528. The slip is then 750—528=222 feet per minute; or,
as a percentage, ff J = 29.6 per cent.

A right-hand propeller is one which when looked at from astern
revolves right-handed, or in the direction of the hands of a clock.
A left-hand propeller is the reverse. Propellers are usually built
right-handed unless for special conditions.

The most important characteristic from the power standpoint
is the blade area. A square inch of blade area will absorb a cer-
tain amount of power at each rate of revolution. A certain blade
area may be obtained by a relatively wide blade on a small
diameter or by a narrow blade on a relatively large diameter.
In the former case the surface ratio is greater than in the latter.
There are certain limits for this surface ratio beyond which it is
not advisable to go; well-proportioned propellers will have surface
ratios somewhere among the following:

For two blades, surface ratio, .20 to .25.

For three blades, surface ratio, .30 to .40.

For four blades, surface ratio, .35 to .45.

This means that for the 24-inch wheel having three blades,
disc area 452 square inches will have a blade area varying between
452 X .30 = 136 square inches, and 452 X .40 = 181 square inches,
depending upon the power to be absorbed by it. The blade area
should not be made greater than these proportions for ordinary
use, as the blades then become so wide as to interfere with the
action of one another. There are, of course, certain unusual
conditions which may require extreme proportions and a result-
ing loss in economy of propulsion may be accepted.

In general terms the blade area fixes the amount of power
which the propeller can deliver, while the pitch, combined with
the turns per minute, governs the speed. The two are, however,
very intimately connected, and a change in one is likely to have
an effect upon the other. To illustrate, a propeller may have a
small blade area and so great a pitch that the blades act like fans

lOO MARINE GAS ENGINES

and simply churn the water; this propeller will absorb the power
but does little effective work. While the power of the engine
is used up, but little effort is exerted in propelling the boat. This
propeller would be improved by decreasing the pitch to a reason-
able amount and adding blade surface to absorb the power.

The other extreme is illustrated by a propeller of large blade
area and very small pitch, so that the blades are almost flat; in
this case the blades tend simply to revolve edgewise through
the water and the power is absorbed by surface friction. The
engine turns at a high rate but has little effect on the motion of
the boat. This propeller will be improved by increasing the
pitch and reducing the blade area.

Either too large a blade area or too coarse a pitch will tend
to slow the engine down below its proper rate of revolution and
thus prevent the development of the required power. On the other
hand, either too small a blade area or too fine a pitch will allow
the engine to run away or "race" without benefit to the speed of
the boat.

If the blade area is correct for the power of the engine, the
pitch will, within certain Umits, take care of itself. This explains
why many engine builders can furnish a certain propeller wheel
with each engine regardless of the conditions xmder which it is
to be used. The same propeller will usually be furnished for all
circumstances, whether for a heavy working boat which can only
be driven at a low speed, or for a Kght launch, and it will appear
to work equally well in both cases. This is due to the difference
in the slip; in the first case the wheel is working with a large
sUp and in the latter case with a small slip, but with fair efficiency
in each case.

While it might seem that a perfect propeller would work with-
out sKp, such is not the case, as, since the forward thrust is
obtained by the forcing back of the stream of water, some sUp is
necessary. The amount of slip is not necessarily a measure of
the efficiency of the propeller. A propeller may work efficiently
at a high shp, but the revolutions of the engine are unnecessarily
high, perhaps bpyond the point of efficient working of the engine.
The average slip for a good working propeller may be taken at
from 15 to 20 per cent. A slip of 30 per cent or above will usually
indicate that a different propeller would probably give better
results.

PROPELLERS lOI

«

The shape of the after end of the hull has a marked effect
upon the slip and efficiency of the propeller; a very full stern
will impede the flow of water to the propeller and thus reduce
its efi&ciency. For this condition a propeller of large diameter
should be used, with narrow blades which will reach out into
the less disturbed water.

Efficiency of Propellers. — The propeller does not utilize in the
propulsion of the boat all the power which is deHvered to it
by the shaft. There are several ways in which power is lost,
the most important of which are skin friction and eddy making.
The efficiency of the propeller may be defined as the proportion
of the power given to it which it uses effectively in propelling
the boat. Expressed as a percentage, the usual efficiency of a
propeller is between 50 per cent and 70 per cent; that is, for
every 10 H.P. delivered to it, from S to 7 H.P. is actually used in
driving the boat.

There are several causes affecting the efficiency of the propeller
which can be taken advantage of, viz.: The surface of the blades
should be ground smooth and even, to reduce surface friction as
far as possible. The thickness of the blades should be no greater
than is required for strength, and the edges should be sharp and
even. At imduly high speeds of rotation the water is forced back
by the propeller faster than is possible for a continuous flow, and
a partial vacuum is formed under the stern, drawing it down
and retarding the speed. The pitch and surface must be suited
to the power and speed, to avoid excessive slip. The form of
the under-water body should be such as to give a free access of
water to the screw to replace that which has been forced back.
The propeller should be kept as far as is convenient from stern
post or deadwood, and should have an immersion of its upper tip
of at least a quarter of the diameter, in order to avoid the churn-
ing up of the surface.

Measuring Propellers. — To measure the blade area of a pro-
peller a center line is drawn down the middle of the face of the
blade, from hub to tip. The length of the blade along this center
line is then divided into several equal parts, and lines drawn across
the blade as shown in Fig. 105. The width of the blade on each
of these lines is then measured, including the tip. These widths
are all added together and the average taken; this average is

I02

MARINE GAS ENGINES

then multiplied by the length of the blade. This gives the area
of one blade, which must be multiplied by the
number of blades.

To measure the pitch, the propeller is laid
upon a flat surface with the shaft exactly ver-
tical. The pitch at any point X may be found
as shown in the lower sketch; ^ C is the width
across the blade; C5 is a vertical line at one
edge and AB is the width projected on to a
horizontal Une. By considering the sketch it
will be seen that in turning the distance A B the
advance is an amount equal to B C. Now the
circumference of a circle through X is equal to
OA" X 2 X V^, and since the pitch is the ad-
vance for one turn, the pitch will bear the same
relation to the distance B C that the circumfer-
ence of the circle bears to A B or

Pitch: BC = Circumference: AB ot
_.^ , BCX Circumference

p^*'=^ = AB ;

In many propellers the pitch may vary at different points
along the blade, in which case the average pitch may be taken.

Fig. 105. — Measur-
ing Propeller.

CHAPTER XII

Installation

Foundaticm. — Before the motor can be installed in the boat
some suitable bed or foundation must be provided. It may be
built in any one of several ways according to the form of the
boat and the shape of the engine base. The simplest form of
bed, and one which is used often for single-cylinder engines, is
made simply of two planks placed on edge athwartships and so
shaped as to fit the contour of the inside of the hull. They
are firmly fastened in place and the engine rests across them with
the flywheel overhanging and parallel with the forward one. The
engine is held in place by lag screws through the holes in the
flanges. This bed will answer the purpose in a heavy boat where
heavy bearers can be used, but in a boat of moderate weight the
strain is not properly distributed, but is concentrated in one
spot, which is likely to cause trouble.

The most approved form of bed consists of a pair of fore and
aft bearers extending under the flanges on either side of the engine
base and resting in turn upon several cross timbers or floors. In
light boats the cross timbers may be dispensed with and the bearers
may rest upon and be fitted to the plank and frames. A bed of
this type is shown in Fig. io6, the cross timbers or floors being
shown at F, F, F and the

fore and aft bearers at B. , ^ ^

The bearers B are notched
down over the floors F
to give additional stiff-
ness and are fastened by Fig. io6.— Engine Bed.
long bolts driven down

through from the top. The cross-braces C are fitted, where pos-
sible, to give transverse stiffness; they must, of course, be fitted
where they will be clear of the projecting under part of the base.
In this style of bed the strain and vibration of the engine are dis-
tributed over a considerable length of the boat so that they are
less marked.

103

I04

MARINE GAS ENGINES

One of the most difficult points in installing the engine is in
so setting it that its shaft is in line with the propeller shaft so
that everything may turn freely without straining. In the first
place the foundation must be built to the proper height and angle.
A cord or thin wire is passed through the shaft hole, stretched
tightly and adjusted so that it is as near as possible in the center
of the hole and also in the center line of the boat. It is then fas-
tened in place, the forward end being secured to an upright well
forward of the proposed bed. This hne then represents the center
of the shaft. The distance D of the flanges of the bed, above or
below the shaft center, is then measured from the engine, and also
the widths w and W, as shown in Fig. 107. The bed is then built
I . I with its upper edge paral-

f — I © — 7^'^T -j^ isj;- — ■r ^ lei with the cord or wire

r\jrrj ^^1 _^ and at the distance D
i L--_nr_J ' above or below as the case

<« « * may be. The inside meas-

riG.107.- Base Measurements. urement TO on the bed

should be slightly greater,
about I inch, than the engine base, to allow some leeway for
adjustment in setting. If the bed is carefully laid out and true
to the measurements, little trouble will be found in getting a
good alignment of engine and shaft.

The engine may now be set into place on the bed, and the
propeller shaft put in position. It is in coupling the propeller
shaft to the engine that care is required to obtain the true line
between the two shafts; if this line is not correct, not only is an
undue amount of friction developed, but the parts are subjected
to a continued strain. If flange coupUngs are used they may be
of great help in obtaining the alignment. The two parts of the
coupling are brought nearly together, within about tV inch, as in
Fig. 108. The space between the faces, as S, S, is now tried at points
all around the circumference by inserting a thin steel wedge or
case knife and noting the distances which it enters. By shifting
the engine slightly on 'the bed this distance may be made equal
all around the circumference so that the wedge or knife will
always enter the same distance. This adjustment may take a little
time and it may even be necessary to remove the engine and trim
the bed somewhat; it is, however, necessary that it be true. When

]zi

INSTALLATION 105

the adjustment is satisfactory the coupling bolts should be put
into place, but without drawing the two parts together; the engine
should now be given half a turn and the spacing between the
flanges tried again. If it remains true the flanges may be brought
together and the bolts tightened up. The whole should now
turn over with very little more friction than the engine alone.

If a sleeve coupling is used as in Fig. 11, the method must
be less direct. The shaft should be tried in the coupUng before
the engine is placed in the boat to make sure that it fits. After
the engine has been put on board, the shaft is inserted into the
coupling and oscillated a few times with a
gentle end pressure. If the shaft and coupUng y®

are not in Une the sharp edge of the latter
will leave marks on the smooth shaft, and by «-
their position one can judge what change must ^
be made in the alignment.

The engine is held in place by lag screws. ^

Care must be taken in boring for them to - g _t • •
bore directly in the center of the hole in the " Coupling,
base, as otherwise there is a chance of throw-
ing out the alignment when screwing down the lag screws. The
base also must bear evenly on the bed with no spaces between
the two. Any space between them should be filled with thin
wood shims Ughtly driven in just before the lag screws are finally
set up. When everything is finally set into place the aUgnment
should again be tried by turning the engine over several times
to make sure that there is no xmdue friction."

Piping for Exhaust. — This is the largest pipe in the outfit
and would best be fitted first. It should be run of pipe the same
size as the exhaust fitting on the engine and should be as direct
and with as few bends as possible. In a two-cycle engine espe-
cially, the power developed may be considerably reduced by any
undue resistance in the exhaust. When bends must be used they
should, if possible, be made from 4S-degree instead of 90-degree
ells, as the resistance of the former is much less than of the latter.

The muffler may be placed wherever convenient, a common
location being under the after deck with the outlet leading out-
board above the water Une. The exhaust pipe should run to the
muffier as directly as possible; a imion should be fitted where

106 MARINE GAS ENGINES

the exhaust pipe joins the engine and another where it connects
to the muffler, this allowing the exhaust piping to be readily
taken down. Galvanized iron piping and fittings should be used
for the exhaust pipe. When the engine is near the middle of the
length of the boat the exhaust piping may be run along under
the floor or inside the lockered seats. A very good practice is
to lead the exhaust pipe out through the bottom of the boat by
a special fitting, along the bottom to a point near the stern, where
it again enters the boat by another special fitting and connects
with the muffler, which leads outboard as before. This method
avoids the loss of space and the heat of the exhaust pipe, which
in the case of a cabin boat is a considerable item. The water
surrounding the pipe quickly cools the exhaust, reducing the
pressure and making the final exhaust almost noiseless. When
it is desired to have the outlet from the muffler below the surface
of the water, a pipe shaped Uke an inverted U should lead from
the muffler as high as the deck will allow before leading outboard;
this is to prevent the entrance of water into the muffler when the
boat is in a heavy sea. Joints in the exhaust pipe should be
smeared with a mixture of graphite and oil before screwing up.

Function of the Muffler. — The fxmction of the muffler is
to provide a comparatively large space into which the exhaust
may pass and expand, thereby reducing the pressure and deaden-
ing the sharp impulses. The gas under the much reduced pres-
sure then passes out into the air with Uttle disturbance. No
particular shape is essential, the volume being the only require-
ment. Mufflers for small engines are usually made of cast iron,
while for the larger sizes they are of sheet metal riveted together.
In some cases the exhaust pipe itself may be enlarged to serve as
a muffler.

Many special forms of muffler have been devised, in which, by
a suitable arrangement of plates and orifices, a suction effect is
obtained, which tends to draw the exhaust gases toward the muffler
and thus lessen the back pressure. In other forms the same effect
is obtained by introducing the cooling water into the muffler in
such a way as to quickly cool the exhaust gases and greatly reduce
the pressure.

Under Water Exhaust. — It is often possible to carry the
ejdiaust directly outboard just below the surface of the water, thus

INSTALLATION 107

saving nearly all exhaust piping and completely deadening the
noise of the exhaust. While this is a very convenient way of dis-
posing of the exhaust, and is many times satisfactory, great care
must be taken in fitting it, or poor results will be obtained. When
the exhaust is led directly outboard a certain pressure is required
to displace the water; this pressure is furnished by the exhaust
and is a back pressure, acting to retard the piston, reducing the
power of the engine. Some form of shield must be fitted over
the opening of the exhaust pipe to direct the stream of the exhaust
aft and thus reduce the back pressure. Several devices of this
kind are on the market, most of which consist of a brass casting
bolting on the outside of the hull, and having a threaded stem
projecting inside the boat, to which the exhaust pipe is connected.
It is often possible to use a right-angle elbow for this purpose,
screwing it on so that the outlet leads aft; and fitting a washer
and packing between it and the planking. Some form of expan-
sion chamber or small mufBer must be provided between the
engine and the outlet to break up the violent pulsations and make
the outward flow fairly constant. A pet-cock, or other opening,
should be provided in the exhaust pipe, which may be opened
when the engine is at rest, to prevent the water being drawn up
by any partial vacuum which might arise. As there is some-
times difficulty in starting an engine with the under-water exhaust,
it is well to fit a cock or valve some size, so that it may be used
as an outlet while starting the engine.

Cooling Water Pipiftg. — This system of piping should next be
fitted; it should be of brass and of the same size as the fittings
on pump and engine. The suction to the pump is connected to
a pipe extending through the bottom of the boat at some con-
venient point. The joint at the planking must of course be water-
tight; special fittings should be used for this purpose, having
some provision for fitting packing water-tight at the plank, and
an inside stem for the attachment of the piping. This is one
of the fittings which are provided with every engine outfit. This
pipe may be made up soUd if desired, but it is considered good
practice to fit a short length of stout rubber hose at some con-
venient point to take up any vibration and prevent the starting
of the joint at the plank. The outer end of the pipe must be
covered with some kind of strainer to prevent the entrance of

Io8 MAEINE GAS ENGINES

weeds or other material which wovild clog the pump. If desired,
a branch suction pipe may be run to the lowest point inside the
boat, allowing the boat to be drained by the pump while the engine
is running. When this is done a valve should be placed in each
branch so that the pump may draw from either as desired. Both
valves should be closed when the boat is put up, to prevent the
water from backing up through the two suctions and flooding the
boat. It is considered by. some not to be good practice to run
the water from the bilge through the jackets on account of the
liability of depositing sUme and oil in the passages of the jackets.
If, however, a strainer is fitted on the end of the suction, and care
is taken to use it only at the beginning of a run, no objection can
be made to this method of piping.

The piping from the pmnp discharge to the cylinders is usually
fitted up when the engine is assembled, or in many cases the pump
discharges directly into the cylinder as in Fig. ii.

The overflow from the cylinders is piped directly overboard
in a convenient place. It is good practice to branch tiiis overflow
pipe, leading the second branch to an opening in the exhaust
pipe, so that a part of the cooling water passes directly into the
exhaust pipe and mingles with the exhaust gases. The presence of
the cooUng water in the exhaust cools the latter very materially,
reducing the noise of the exhaust and rendering the pipe itself
cooler. All of the cooling water can hardly be run into the exhaust
as the cooling effect HMght be too great; for this reason a valve
should be fitted in each branch so that any desired amount may
be run into the exhaust. The point where the cooling water pipe
enters the exhaust pipe should, if possible, be at a level lower than
the exhaust from the engine, to avoid any possibility of water being
drawn back into the cylinders. The cooling water should not
be run into the exhaust until the pipe has become well heated,
as otherwise the water might not be carried out, but might collect
at some point and cause trouble. A pet- or drain-cock should
be placed at the lowest point of the exhaust pipe to drain off any
collection of water which may condense.

Joints in the water piping should be smeared with white or
red lead before setting up.

Carbureter and Fuel Piping. — The piping of the carbureter
to the engine should be fitted when the engine is assembled. The

INSTALLATION

109

inlet to the carbureter or vaporizer should be screened so that any
spray or rainwater cannot be sucked in with the air, thus spoiling
the mixture. When possible, warm air should be delivered to
the carbureter, by running a pipe from the air inlet to a point
between the cylinders, or to a perforated jacket aroxmd the
exhaust pipe. Many carbureters, and vaporizers are provided with
a threaded air inlet, making this piping an easy matter. Where
the end is plain, it can many times be tapped out, or the pipe may
be clamped on. For this air pipe, a sheet metal pipe is amply
strong. The furnishing of warm air to the carbureter is much
to be recommended, as, since the temperature of the incoming air
is always nearly the same, the mixture is less affected by atmos-
pheric changes and the engine rims more regularly. When the
drawing of warm air is not provided for, the proportions of the
mixture will change with each change of atmospheric conditions,
requiring slight adjustments of the air and fuel supplies from time
to time.

Even if it is not feasible to supply warm air to the vaporizer,
it is advisable to so pipe the air supply as to draw it from a dry
place, as from a locker. Care must, however, be taken to fit a
screen over the end of the pipe and otherwise prevent hght articles
like cotton waste from being sucked into the pipe to cause trouble.

The fuel tank and piping must be made and fitted with the
greatest care, as any leak may have fatal consequences. Too
much stress can hardly be laid on this point, as nearly all accidents
can be traced to a leak in the fuel tank or piping, combined with
more or less carelessness.

The tank should be of strong construction, of either copper
or galvanized iron, well riveted and then soldered, with suitable
swash plates if the tank is of large size. When convenient to use,
the round, cylindrical form of tank is best as it has the fewest
joints and is the strongest shape. The filling pipe should extend
from the tank to above the deck with no break, so that any over-
flow while filUng the tank will run overboard instead of into the
boat. A screw cap should be fitted to the filling pipe above the
deck. A small vent hole should be fitted at some convenient
point to admit the air as the fuel is drained out.

Some builders and designers favor the fitting of pans or other
arrangements imder the fuel tank to catch and carry off any pos-

no MAEINE GAS ENGINES

sible leakage, but in the writer's opinion it is as well to make sure
that all joints are absolutely tight at the start and by constant
observation assure that they stay so.

The fuel piping should be either of copper, brass, or lead, and
should have as few joints as possible, and these, except a union at
each end, should be soldered. A stop-cock should be fitted to
the fuel tank and another where the piping joins the engine;
this allows the overhauling of either the carbureter or the pipe
without draining the tank. Some form of strainer should be
fitted in the fuel pipe near the carbureter to catch any sediment
or other foreign matter which would clog the carbureter. A
device of this kind is shown in Fig. 109, it consists of a fitting
containing a screen G of wire gauze through which the fuel must
pass. The bottom can be imscrewed and any collection removed.
The same effect can be had by the fitting shown in Fig. no.

Tee, f-,

M3]

Cap

F1GS.109-110.— Fuel Strainers.

The fuel pipe is joined to the carbureter by a Tee fitting, one
branch of which points downwards; into this branch is screwed a
piece of pipe a few inches long, and one or two sizes larger than
the fuel pipe. Sediment or water, being heavier than the fuel,
will settle down into the vertical pipe and may be removed by
unscrewing the cap.

The fuel tank may be placed wherever most convenient,
provided that the outlet is always a few inches above the
carbureter to assure a flow. A common place is at the bow, as
the space there is usually the least valuable. Under the seats in
the standing room is also a convenient position. If a water-tight
standing room is fitted any possible leakage will thus drain over-
board. The tank should, of course, be kept as far as possible from
hot pipes or the muflSer.

INSTALLATION III

This completes the usual piping; additional piping may be
fitted in some cases to carry out some particular idea, or for some
special make of engine. Many engine builders furnish piping
plans to accompany the engine, and many others will furnish
them if requested.

In all piping and wiring care should be taken to make aU con-
nections as simple and direct as possible, so that in the case of
trouble or repairs it can be easily and quickly gotten at. Unions
should be used in such positions that piping may be removed
without breaking any threaded joints. When piping runs through
lockers or other woodwork it should be so arranged that it can
be taken down without disturbing the woodwork.

Batteries, Coils, and Wiring. — All parts of the ignition out-
fit should be placed in a dry place, as moisture greatly interferes
with their action or may in time ruin them entirely. Dry bat-
teries especially shovdd be kept with great care, as moisture will
run them down very quickly. In a cabin boat the batteries
should be placed in a locker well above any moisture from the
bilge water. In an open boat, the batteries should be packed
into a box with paper stuffed in around them and the whole kept
as dry as possible. For small boat work a very satisfactory arrange-
ment is to fit batteries and jump-spark coil into one box with
a cover. Connections are made inside the box to binding posts
on the outside so that connections can be readily made. This
box may be kept on shore when not in use so that all may be
kept dry and in good order. In this way the life of the batteries
may be greatly prolonged and the reliability much increased.
It is often advised to seal up the batteries in a box or cover them
completely with tar or pitch, with the object of rendering them
waterproof. This is not always to be advised^ as a single poor cell
in a set will spoil the action of all and it is best to have them
accessible so that in case of trouble they can be tested and the
poor ones replaced.

From four to six batteries should be used in a set. If too few
batteries are used the current and the resulting spark will be weak;
on the other hand, if too many are used, the contact points on the
coil are apt to suffer. As a rule six batteries may be used in a set
without fear of damage, and these will give sufficient current
to make the ignition fairly sure and allow of some deterioration
in the batteries without replacing.

112 MAEINE GAS ENGINES

If a magneto is fitted, it may be placed on the floor and run by
a friction wheel against the fl)rwheel, or by a belt. When it can
be done, it is preferable to arrange brackets from the engine frame
to support the magneto; as it may then be placed clear of the floor
where it is less liable to damage.

A convenient tool and supply locker, with a lock, should be
arranged. Too often small tools or parts are thrown loosely
into a locker, to be lost or ruined by water. The locker should
be convenient of access and in such a position as to prevent the
access of water. This locker is a point to which too little atten-
tion is usually given.

It is, of course, impossible to enumerate all points in connec-
tion with the installation of all the varied types of engines under
the varying conditions, but the general principles remain the same
with only the differing details of each individual installation.

CHAPTER Xni
Operation and Care of Engines

Starting. ^- Before attempting to start an engine one should
acquaint himself with the operation of all parts of the engine, and
the water, oiling, and ignition systems.

If the engine has been stancUng some time, the ignition sys-
tem should be tested to make sure that it is in good order. The
make-and-break system may be tested by first closing the switch
in the circuit, then turning the flywheel imtil, by observing the
action of the mechanism, the points inside the cylinder are known
to be in contact, dosing the circuit. The wire is then removed
from the insulated terminal of the igniter and brushed across it;
if the circuit is complete a briUiant spark will result. If no spark
is obtained all connections must be examined and, if necessary, the
sparking points removed from the cylinder and cleaned. After
a spark has been obtained through one cylinder the other cylin-
ders should be tested.

The jump-spark system is tested by removing the plug from
the cyUnder and resting it upon any of the bright metal parts
of the engine with the secondary wire still in contact. With the
primary circuit closed the engine is then turned until contact is
made by the timer, which should be indicated by the buzz of the
vibrator. The sparks should pass across the points of the plug
at the same time. If no buzz of the vibrator occurs it shows a
defect in the primary circuit. If the vibrator buzzes, but no
spark passes the sparking points, it shows a fault in the secondary
circuit. This may often be remedied by removing any deposit
of carbon or oil which may have collected on the points of the
plug, or by fitting another plug. After a rain, or in damp weather,
the most common sources of ignition troubles are weak batteries
or a "ground." The former can be found by testing the bat-
teries with an ammeter; the latter is caused by the current,
especially the secondary, jumping across from the wire to some
adjacent pipe or other part. It may be found by carefully examin-

"3

114 MARINE GAS ENGINES

ing the wires, or, in the case of the secondary current, the sparks
may be seen to pass where the current jumps. The wiring of
each cyUnder should be tested in turn. At the same time that
the ignition is tested, the point of ignition should be noted in
reference to some point on the flj^wheel, and its variation with
the different positions of the timer handle noted. The gear or
timer should be so set that the spark occurs when the piston is
at the top of its stroke.

Oil- and grease-cups should now be filled and a small amount
fed from each.

The fuel supply should now be turned on, both at the tank and
at the carbureter. The needle valve on the carbureter or
vaporizer should be opened sUghtly and the carbureter primed
somewhat to make sure of a good flow of fuel. The engine may
now be turned over by hand in the direction in which it is to run,
using the crank, lever, or flywheel rim, as the case may be. After
a few trials the engine should explode a charge and turn a few
turns and possibly continue to rim. If it does continue to run,
the fuel and air supplies should be adjusted gradually until the
engine turns at its highest speed. Oil-cups should then be opened
to allow the oil to feed.

If, in the case of a four-cycle engine, it does not start at once,
all that is necessary is to turn it under varying conditions of fuel
and air suppUes, after making sure that the ignition system is
operating and that fuel is flowing to the carbureter. In the case
of a two-cycle engiae the fuel should be shut off and the compres-
sion cock opened. It is probable that several charges of gaso-
line have been taken into the base and not exploded; making
the mixture far too rich and "flooding" the engine, as it is
termed. The flywheel is now turned several times and the mix-
ture diluted and partially expelled. An explosion will finally take
place and the engine run until the supply in the base has been
used up.

Another trial can now be made, with a reduced fuel supply, and
continued imder the varying conditions until the engine starts,
always making sure that the ignition occurs properly, and taking
care not to flood the base.

Starting is often made easier by priming the engine, that is,
by inserting a small amoimt of gasoline directly into the cylinder

OPERATION AND CARE OF ENGESTES 115

through the compression cock, or through a special priming cock
which on some engines is provided for that purpose.

When turning the engine over by hand care must be taken
to have the sparking gear so set that the spark cannot occur until
the piston has reached the top of its stroke. If this is not done
and ignition takes place before the piston has reached the top of
its stroke, it will be driven violently downward in the wrong direc-
tion, giving a "back kick," which is liable to cause damage.

After the engine has rtui a short time it will often gradually
slow down and finally stop, with a muffled explosion in the base.
This is a sign of a weak mixture, and the fuel supply should be
slightly increased. On the other hand, if the engine labors, slows
down, and finally stops, with black smoke issuing from the
exhaust, it shows a too rich mixture and the fuel supply should
be cut down.

The best fuel mixture can be found only by experiment, and
will even then vary somewhat, according to atmospheric con-
ditions. The proper regulation of the air supply to the fuel
supply has a marked influence upon the fuel economy.

Two-cycle engines of the two-port type are easily and readily
started as follows: The spark is advanced to a point somewhat
below the usual running point so that the ignition wiU take place
on the up stroke when the engine is tinned in the opposite direc-
tion to which it runs. The flywheel is then turned imtil the pis-
ton is at the bottom of its stroke, and is then rocked backwards
and forwards a few times; the piston thus acts as a pump, draw-
ing a few small charges into the base and charging the cylinder.
The flywheel is then turned quickly in the reverse direction to
which it runs, bringing the piston up against the charge, which
finally ignites and forces the piston down again, but in the right
direction. The flywheel is then released and the engine starts.
The spark is then restored to the running position.

This method cannot be used on a three-port engine, which
must be started by turning it over the center.

Some engines will start with the compression cocks fully or
partly open, which lessens the labor; others must be pulled over
against the full compression.

In starting the engine with a crank or lever it should be held
loosely in the hand, so as to be quickly released in the event of

Il6 MARINE GAS ENGINES

a back kick. Frequent accidents happen from the disregard of
this precaution.

Oiling. — When the engine is well started the fuel and air
supplies should be regulated until the engine is running on the
least possible amount of fuel. The oil supply should be regulated
to a point just below that at which smoke would issue from the
muflBer. Blue smoke coming from the muffler usually shovvS that
too much oil is being fed, which instead of being of use in the
engine is burned or carried away by the exhaust, and wasted.

The cylinder oil-cups should be adjusted to feed from three to
six drops per minute, according to the size of the engine. Where
splash lubrication is used, oil must be fed into the crank case or
base at intervals. Exterior parts, such as thrust bearing, igniter
gear, and pump journals, are, of course, oiled from an oil can when
necessary. In running a new engine oil should be used rather
freely at first while the bearings are wearing down into place.
The cylinder surface may be greatly improved by feeding in some
powdered graphite mixed in oil, wMch fills up the pores and helps
to form a sort of scale on the bore of the cylinder. While too
much oil should not be fed, as it is not only wasted, but makes
the engine dirty, a sufficient lubrication should be made certain
at all times, as much damage may be done in a short time if bear-
ings are allowed to go dry.

Under some circmnstances good results can be obtained by
mixing the lubricating oil with the gasoline in the tank and feeding
both together. No difficulty is experienced with the vaporization
and the lubrication is simplified. Although the relative amounts
will vary considerably, a fair proportion seems to be about one
pint of oil for every five gallons of gasoline.

Spark Advance. — While running the engine it will soon be
noted that the time of ignition has a great effect on the speed.
It will be found that the engine runs best when the ignition takes
place just before the piston reaches the top of its stroke. This
is due to the fact that the burning of the charge is not instan-
taneous, but requires an appreciable time. If the charge is fired
at the moment when the piston is at the top of the stroke, the
time taken by the charge to thoroughly ignite dlows the piston
to descend through a part of the down stroke, so that some of
the effect of the impulse is lost. If the spark is so timed in

OPERATION AND CAKE OF ENGINES 117

advance that the charge is completely ignited at the time when
the piston is just ready to descend, the full effect of the impulse
is received and absorbed.

This advance of the spark is called the "spark advance" or
"lead." It will of course vary somewhat according to the speed.
The speed of the engine can be varied by shifting the point of
ignition, and this is advocated by many. Starting with the spark
occurring as the piston is at the top, it will be found that up to
a certain point the speed will increase as the spark is advanced.
Beyond this point the engine will pound and act irregularly. If
the spark is retarded imtil after the piston has begun to descend,
the speed will decrease. The speed of the engine may thus be
regulated by changing the spark advance, but this practice is
not to be recommended, as nearly the same amount of fuel is
passed through the engine per stroke at all speeds. At low speeds
the charge ignites so slowly that all the heat generated cannot
be absorbed, but is passed along into the exhaust pipe and muffler,
heating them beyond their usual temperature. The speed of the
engine should be regulated by the throttle which is usually pro-
vided for that purpose; in this way the amount of the mixture
is cut down in proportion with the speed. The speed should be
regulated by the throttle and then the spark advanced to the
best point by trial. In this way the greatest econdmy in the
use of fuel may be obtained. Extremely slow speed must, how-
ever, be obtained by retarding the spark, in connection with the
throttle.

Care of the Engine. — The degree of care which the engine
receives, not only when running, but when laid up as well, has a
great effect upon its Ufe and also its satisfactory operation. Many
engines which are well taken care of while in operation are allowed
to suffer from exposure during the time when they are not in use.
If the engine is in a cabin boat it is very easily kept in good shape,
but if in an open boat, constant care is required to prevent it
from being damaged by rust. A cover should be made from water-
proof canvas, wMch will fit snugly over the engine and shed aU
rain. A water-tight pan imder the flywheel wiU prevent the bilge
water from rising around it and causing it to rust. Before leaving
the engine for a few days all bright parts of iron or steel should
be' smeared lightly with grease, which may be readily removed

Il8 MARINE GAS ENGINES

with cotton waste. This precaution will save a large amount
of scouring and polishing later.

One should become thoroughly familiar with the construction
of his engine as soon as possible. It is not meant by this that the
engine should be pulled down just to see how it is constructed,
but quite the contrary. As long as the engine is running, particu-
lar pains should be taken not to disturb it. The construction
should, however, be studied so that in case of necessity it could
be taken down. Much expense can often be saved by this knowl-
edge, as there are many small repairs which can easily be made
by the amateur owner.

Before starting on a run all nuts and bolts should be examined,
and any which may be loose should be tightened.

Engine Troubles. — The presence of trouble in the engine is
usually indicated by a peculiar hammering noise, known as a
"knock." It may be caused by excessive friction on some part
and the oiling system should be at once examined and perhaps
an additional amount fed for a few moments. A similar knock
may be caused by the failure of the water-circulating pump,
which may be told by the unusual amount of heat radiated from
the cylinders. The lack of cooUng water causes the cyUnders to
become much too hot for use, increasing the friction and even-
tually causing damage to cylinders and pistons. If the knock
cannot be found in this way, the engine should at once be stopped,
as damage may be caused. The knock is probably caused by
some part which has become loosened, and all parts should be
thoroughly examined. A loose flywheel is a common cause of
knocking. Where the flywheel is fastened with a key as in Fig.
lo, the keyway may become worn so as to leave a small space
between it and the sides of the key, allowing the flywheel to "play"
slightly around the shaft. If this is the case the key should be
withdrawn and a slightly wider one fitted, or a thin "shim" of
steel may be carefully fitted into the keyway and the key driven
in alongside of it.

A bearing which has become overheated and ground out will
cause a knock; this is a more difficult cause to remedy, and is
likely to require the services of a machinist to reset the bearing.

Sometimes the engine will run with apparently no trouble,
and yet will show less than the usual power. This may be due

OPERATION AND CARE OF ENGINES I19

to loss of compression, or in other words, a leakage from the com-
pression space. This may be due to a loose plug or screw at
some point, or in the case where the cylinder head is fastened on
with studs, it may mean that the gasket under the head has
become broken at some point and it may be remedied by fitting a
new gasket. If the cyUnder has been flooded too freely with oil,
the excess may carbonize and collect around the piston rings,
cementing them to the piston and allowing the gas to escape
by the piston. This may often be remedied by flushing the cylin-
der with kerosene oil. It may often be necessary to remove the
cylinder and separate the rings from the piston. In removing the
rings from the piston great care is necessary as they are of cast
iron and very brittle. Before attempting to remove them they
should be well washed with kerosene, to loosen them as far as
possible. In removing a ring, one corner should first be raised
with a screw-driver or other tool, and a narrow strip of tin placed
across the groove under it to keep it from springing back; this is
followed up all around the ring, tapping it lightly and adding
more strips until the ring is entirely supported clear of the groove.
It may then be shd from the piston. Rings and grooves should
be thoroughly cleaned with the help of kerosene. In replacing
the rings the reverse operation is followed.

In the four-cycle engine it is necessary to "grind in" the
valves at intervals when the seats and surfaces become pitted
or worn. When the valves are arranged as in Fig. 24, the inlet
valve may be removed to allow access to the exhaust valve. The
springs are rertioved from the stems, the valve is raised and the
bevelled edge smeared with a paste of oil and emery. The grind-
ing is done by rotating the valve in its seat by means of a screw-
driver or brace; and the process continued until the surfaces are
left smooth and polished, with no sign of corrosion. This paste
is then removed and the finish put on with a mixture of water and
pumice. During the grinding the entrance to the cylinder should
be carefully stopped with a wad of waste to exclude the emery
from the cylinder, where it would do great damage. If the inlet
valve is removable it may be ground while held in the hand.

In replacing the valves it may often be found diflScult to com-
press the springs sufficiently to allow them to be replaced. If
no other means is at hand the spring may be compressed in a vise

120 MARINE GAS ENGINES

and bound with a few turns of strong cord. It may then he
slipped on the stem and the key and washer put on. The string
may then be cut and the spring let out.

Care of Spark Coil and Ignition Outfit. — The entire ignition
outfit is somewhat delicate and requires its share of attention.
It should be examined at intervals to make sure that all binding
screws are tight and all contacts good. The insulation should
be examined and any places where it becomes worn should be
taped. Two parallel wires should never be fastened by a single
staple, as the insulation is Ukely to chafe through, causing a short
circuit. Each wire should have its separate staples.

The most common place for a wire to break is at some place
where it is bent back and forth, as where the wires are connected
to the timer; a short coil at such points will greatly increase the
life of the wire.

The entire system, including the plugs, and sparking points,
should be kept clean and free from oil. Oil on the outside of the
plug will cause a short circuit, as does the collection of soot around
the points.

The spark coil should be looked over and if necessary read-
justed sKghtly. Many operators Set the vibrator adjusting spring
too tight, with the idea that the very rapid motion gives a stronger
spark. This may seem true when tested in the atmosphere, but
on a quick running engine it may give trouble by skipping. A
more reUable spark is given with, a moderately rapid vibration
of the buzzer, with considerably less battery consumption. A
satisfactory adjustment of the vibrator may be obtained as fol-
lows: The vibrator adjusting screw is drawn back until it is clear
of the spring; the spring is then set so that the iron button is
from tV to I inch from the end of the core. The adjusting screw
is then screwed in until it touches the spring lightly. The engine
is then started and the screw turned in slightly until the engine
runs steadily; the spring should be left as weak as possible and
still have the engine run steadily. The spring must bear against
the screw when the engine is not running, as otherwise no current
will pass and the engine will not start. In testing the spark in
the secondary circuit, the spark should not be drawn out to the
limit, as this strains the coil and is almost sure to cause trouble
if there is any weakness in the coil.

OPERATION AND CARE OF ENGINES 121

The magneto requires only a small amount of attention. It
should be kept oiled and dry. The breaker points should be
cleaned when necessary and adjusted to separate on the break to
about the thickness of a worn ten-cent piece. They should also
be faced off when pitted, with a thin fine file. In the case of serious
trouble with the magneto it should not be taken apart, but should
be entrusted to some one making a business of such repairs.

Dry Cells, — Dry cells also should be examined occasionally.
Weak cells may be located by testing with an ammeter.
When new, dry batteries of the usual size should test from i8 to
25 amperes, and as a rule they should not be used after they have
fallen below about 8 amperes. A single weak cell will spoU the
action of an entire set; even if no new ones are at hand the action
will be improved by cutting out the weak one. In testing a bat-
tery the ammeter should be held across the terminals only long
enough to get the reading, as if held there even for a short time
the battery is quickly run down.

Batteries which have been run out may be temporarily revived
by punching a hole in the top and pouring in some water.

Storage Baitery. — The storage battery should be disposed in
a dry place and securely chocked against the motion of the boat.
It should be kept fuUy charged as far as possible, as in this condi-
tion the deterioration is least. The battery should be examined
at intervals and the specific gravity tested with a hydrometer,
directions for doing which usually accompany the instrument.
By unscrewing the caps the height of the liquid inside can be
observed, and if the plates are not covered, distilled water should
be added. When removed from the boat for any reason it should
first be fully charged, and when replaced great care should be taken
to connect it up as before, as a wrong coniiection wiU quickly
ruin the battery. During the season when the boat is laid up the
battery should be sent to some station making a business of caring
for batteries, as it must be charged periodically and cared for, as
otherwise it would probably be spoiled during the long laid up
season.

CHAPTER XIV

PowEB OF Engines

The term "horse-power," when applied to the ordinary small
engine, is a somewhat elastic and in many cases an abused one.
Few boat owners are aware of the real meaning of the term and
are even less well informed as to the actual power which they
should expect to get from their engines. Manufacturers, even,
are not always informed as to the power of their engines, as great
differences may be observed in the rating of the same size of engine
by the different manufacturers.

The term horse-power is an arbitrary one, and signifies the
abiUty to do 33,000 foot pounds of work in one minute; in other
words, a force which can overcome a resistance of 33,000 pounds
at the rate of i foot per minute will generate a horse-power. The
same will be done by a force of i poimd acting at the rate of 33,000
feet per minute, or a force of 1000 pounds acting at the rate of
23 feet per minute. It may be expressed thus:

Work = force in pounds X distance in feet.

_- force in poimds X distance in feet

Horse-power =

33,000

The horse-power of the engine may be considered under the
following heads:

1. Indicated horse-power or I.H.P.

2. Actual developed or brake horse-power — B.H.P.

3. Effective horse-power or E.H.P.

Indicated Horse-power. — Although this method of measuring
the power of the engine is used mostly in the case of steam engines,
it can be used on gas engines, and is so used in measuring the power
of large engines. This method of calculation is dependent upon
the use of the indicator; details of this instrument, which is very
simple, can be found in any book on steam engineering. All that
need be noted here is that by means of a moving strip of paper

POWER OF ENGINES

123

and a pencil which is controlled by the pressure in the cylinder,
the pressure is recorded at all points of the stroke. This will
be made plain by referring to Fig. in. The length A-B of the
diagram represents the stroke of the piston. Vertical distances
above the line of no pressure, A-B, represent pressures; at any-
point in the stroke, then, the pressure in the cylinder will be shown
by the distance from the base or zero line A-B to the diagram
outline. The upper Une is the diagram for the power stroke,
while the lower Une is that for the return stroke. The point C,
where the pressure is highest, is just after ignition, when the
maximum pressure is reached. The pressure falls as the piston
descends, until the point D is reached, where the exhaust opens,
after which it falls rapidly to
the end of the stroke and
becomes equal to the atmos-
pheric pressure. At the point
E the exhaust closes and the
contents of the cylinder are
compressed until the point P
is reached, where ignition
takes place and the. pressure
rises rapidly imtil the point
C is reached again. This is
the diagram for a two-cycle
engine; that for a four-cycle engine is very similar As the Unes
of the exhaust and suction strokes are under practically atmos-
pheric conditions, the exhaust stroke will be continued from B
to ^ in a Une coincident with the zero line, and the inlet stroke
will also Ue in this line from A to B; the compression Une B, E, F
is the same as before.

The expansion Une C, D, B represents pressure acting upon
the piston, forcing it ahead, while the line B, E, F represents pres-
sure tending to retard the piston, or back pressure. Thus the
width of the diagram at any point shows the net pressure acting
on the piston, and the average width shows the average pressure
throughout the stroke. This average pressiire, or, as it is called,
the "mean effective pressure" or M.E.P., is the force acting on
the piston to produce the power. If we call the M.E.P. simply
"F," and the area of the piston in square inches "A," the force

FiG.iii. — Pressure Diagram.

124 MARINE GAS ENGINES

acting on the piston is P X A. If now this force is multiplied
by the length of the stroke in feet, "L," PXAXL equals the
work done per stroke, and it is only necessary to multiply this
by the number of power strokes per minute and divide by 33,000
to obtain the I.H.P.

In the case of the ordinary steam engine, which is double
acting, there are two working strokes for each revolution. If
the number of turns per minute equals "N," 2X N will be the
number of pow^r strokes per minute. Then the

^„^ PXAXLX2N
l.xl.ir. = — — -

33,000

or, as it is usually written for ease in remembering it,

2-P-L-A-N

I.H.P. =

33,000

It must be remembered that in this work the pressure is measured
in pounds per square inch and the length of the stroke in feet.

The quantity 2 X Z, X iV is tenhed the "piston speed" and is
the distance travelled by the piston in one minute.

In the case of the gas engines the method is similar. In the
single-acting two-cycle type, having one impulse for each revo-
lution, the

J.H.P. = l^^^^AlN
33,000

For the four-cycle engine having an impulse on alternate
strokes the number of power strokes per minute is | N, so that
the

I.H.P. = ^-^-^-^
2 X 33,000

These formulas are for the power of one cylinder and must
be multipUed by the number of cylinders in the case of a mul-
tiple-cyUnder engine.

The I.H.P. is a measure of the work done in the cylinder,
rather than the power delivered by the engine. It will be plain
that a certain amount of power is necessary to overcome the
friction of the several working parts of the engine itself, or, as

POWER OF ENGINES 1 25

it is termed, the "engine friction." The remainder, which is
delivered to the shaft, is the developed or brake horse-power. The
proportion which the brake horse-power bears to the I.H.P. is
called the "mechanical efficiency"; it might be further defined
as the percentage of the I.H.P. which is available at the shaft.
This proportion for gas engines is about 85 per cent for large
engines and 80 per cent for small ones.

The indicator card, besides giving the power, also shows much
regarding the general proportions and operations of the engine.

Brake Horse-power Formula. — There are several ways of
arriving at the probable B.H.P. with sufficient accuracy for many
purposes. The following formulas are found to give it quite closely
for engines of usual design:

For four-cycle engines B.H.P. = —

For two-cycle engines B.H.P. =

1000
A XLXNXC

75°

where A = area of cylinder in square inches.
L = stroke of piston in feet.
N = turns per minute.
C = number of cylinders.

It should be noted that the area is in square inches and the
stroke is in feet.

Results similar to the above will be obtained by calculation
by the I.H.P. formulas just given, using a net M.E.P. of 66 pounds
per square inch for four-cycle engines and 44 pounds for two-cycle.
This net M.E.P. takes account of the losses and approximates
to the B.H.P.

Brake Test. — Where it is possible to apply it, the brake test
gives a very satisfactory and easily applied means of determining
the power. This method gives directly the actual power which
is available for use at the shaft.

The simplest form of brake is the rope brake shown in Fig.
112. It consists of 'several turns of rope around the flywheel,
the ends of the rope being connected to the spring scales P and Pi.
Some means of varying the tension in the rope is provided, such
as the pulley S. The flywheel turns in the direction of the arrow.

126 MARINE GAS ENGINES

The tension in the rope is adjusted until the engine nins at the
desired rate; the pull on both scales is then read off, that on P^
being found to be the larger. As these two scales oppose each
other the difference between their readings will represent a net
pull, which we may call F. It is this pull F which, acting at
the rim of the flywheel, absorbs the power, and it may then be
considered that the power is generated by a force equal and
opposite to F, acting around the rim of the flywheel. Calling the
diameter of the wheel D, the circumference will be

7
and the work done during one revolution of the wheel will be

FXDX -

7

If the wheel turns N times per minute, the work done per minute
will be

FXDX — XN,
7

and if this result is divided by 33,000 the result

FXDX22XN
33,000 X 7

will be the horse-power developed.

Small chock pieces B, B may be fitted to prevent the rope
slipping over the edge of the rim, but for small powers this is
not necessary. The face of the wheel is lubricated and the num-
ber of turns of rope so adjusted as to absorb the power without
undue tension. This form of brake cannot be used for a long test
on account of there being no way of getting rid of the heat gen-
erated by the friction. For occasional testing, however, it will
answer very well.

Where the power to be measured is greater, the "Prony"
brake shown in Fig. 113 is used. It consists of a metal band B
encircUng the wheel, and carrying the series of wooden blocks
which rest on the face of the wheel. The grip of the friction band
is varied by the screw and hand wheel W. A frame F is coimected

POWER OF ENGINES

127

Fig. 112. — Rope Brake.

to the band B, to the end of which the spring scale S is attached.
With the wheel turning in the direction
of the arrow the hand wheel H is tight-
ened gradually until it runs at the de-
sired rate. The band is prevented from
turning by the tension on the scale S,
which can be read off. The figuring of
the power is the same as in the previous
case, the horse-power equaUng

FX22X2XRXN
7 X 33,000

F being' the pull on the scale, R the dis-
tance from the center of the wheel to
where the scale is fastened, and N the
revolutions per minute.

This style of brake may be appKed
to any flywheel, although with the usual
flywheel only short tests can be run on
account of the heat generated. Special brakes are often made, to
which the engine may be coupled; in this case a fljrwheel having a
deep trough-like rim is used. Water may be fed into this rim, to
be distributed over it by centrifugal force; the heat generated by
the friction is used up in evaporating the water, which is replen-
ished when necessary. This brake may then be used almost con-
tinuously. Where much testing is to be done, as in an engine

factory, a brake of this
description may be made,
with wheel and bearings
complete, independent of
the engine. By means of
a couphng the engine
to be tested may be
quickly attached. For
large brakes the pressure
of the arm F may be
taken on a platform scale.
By making the brake of

Fig. 113. — Friction Brake.

sufficient size, large powers can be measured.

128

MARINE GAS ENGINES

A very convenient method is by electrical measurement, in
which the power developed is converted into electrical energy,
measured and absorbed. The engine is coupled to the dynamo
and the power developed is measured by volt and ammeters and
absorbed by some electrical resistance, either lamps or water
resistance. Fig. 114 shows the general arrangement for a test;
the engine is coupled to the dynamo D and run at the proper speed,
the load is adjusted by varying the resistance R, and the current
generated is measured for voltage by the voltmeter V and for
amperage by the ammeter A. The product of the amperes multi-

pUed by the volts gives
the number of "watts,"
which is the electrical
measure of power. A
horse-power equals 746
watts, so that if the num-
ber of watts developed is
divided by 746, the result
will be the horse-power
developed by the dynamo.
As the dynamo will not
give out as much power
as is put into it, the
power developed by the engine must have been greater according
to the efficiency of the dynamo. Thus the

T, xrp _ amperes X volts
746 X % efficiency

This is a very good method for general use as the efficiency
of the dynamo is readily determined.

The revolutions of the engine do not enter into the final cal-
culation of the power, but should be recorded so that the power
may be known for each rate of speed.

Effective Horse-power — or Horse-power Used in Propulsion. —
As stated in the chapter on propellers, the propeller does not use
in actual propulsion all the D.H.P. delivered to it. The effective
horse-power is thus less than the D.H.P. by the amount wasted
by the propeller in friction and resistance. Taking the efficiencies
there given it will be seen that for a large engine having a mechani-

FiG. 114. — Wiring for Electrical Test.

POWER or ENGINES

129

cal eflBciency of say .85, turning a well-designed propeller whose
efficiency may be perhaps .65, there will be a proportion .85 X .65
= .55 of the I.H.P. actually used as E.H.P. in propelling the boat.
For a small engine whose mechanical efficiency would be about
.80, with a small propeller whose efficiency is Ukely to be not
above .50, the E.H.P. is ,80 X .50 = .40 of the I.H.P. There
are undoubtedly many boats in successful operation which would
show an efficiency much less than the latter figure.

CHAPTER XV

Selecting an Engine

Type. — In selecting an engine for any particular purpose,
several conditions must be considered. The most important of
these is the use to which the engine is to be put. An engine for use
in a heavy working or fishing boat should be of the heavy, slow-
speed type. Under these conditions the engine is subjected to
severe usage and only the heavy engine, with strong parts, will
give the required service with the minimmn amovmt of repairs.
It is not advisable to fit a light, high-speed engine in a heavy
boat, as the high rotative speed of the engine is not well suited to
the slow speed of advance of the boat. For boats of this type
large single-cylinder engines may be used to advantage, as they
are less costly than those of more cylinders, and the vibration is
not noticeable in the heavy boat.

For latmches of the usual proportions which are used for
pleasure only, engines of moderate weight and rotative speed
should be used. A two or more cylinder engine should be used
when possible to decrease the vibration and render the riding
more pleasurable. Although the multiple-cylinder engine is more
expensive, it is far more satisfactory in long runs where the vibra-
tion of a single-cyUnder engine becomes objectionable.

For high-speed launches the light-weight high-speed engine
may be used, as these launches are customarily used on short runs
only, where the high-speed engine will be found satisfactory.
For extreme high speed the maximum amount of power must be
obtained on the lightest possible weight, which can, of course,
only be done with a light, quick-running engine. This type of
engine must be used with the greatest care and cannot be recom-
mended for general use.

For use as an auxiliary a rather light engine should be selected;
as for this purpose the engine is used only occasionally and the
duty is not as severe as in a launch. The horizontal, double-
opposed engine is in many cases well suited to this use, as it can

130

SELECTING AN ENGINE

131

be stowed away under the standing-room floor where the space
is otherwise of little importance.

As to whether a two- or four-cycle engine should be selected
is largely a question of personal preference, as either type wiU
give good service. For small engines there is no reason why the
two-cycle engine should not be entirely satisfactory, as it requires
less care and has the added advantage of much less cost than the
four-cycle. For medium and large engines, where the economy
of fuel and extreme reUability are of importance, the four-cycle
engine has its advantages.

Size of Engine. — The proper size of engine for any boat is
largely a matter of Judgment. While there are niunerous ways
of figuring for the required power for any desired speed, some are
not suited to launches and others are too complicated for the
present work. For laimches of ordinary form a guide to the
proper power may be obtained as follows: Divide the length by

two and subtract seven, or — § 7 = H.P. If the launch is

2

narrower than usual the speed will be greater; on the other hand, an

unusually wide or heavy boat will require more power than given

by the above. It will, however, do as a starting point. This

formula is not, of course, suited to a speed launch, as in this case

as much power should be installed as is possible without adding

an excessive amount of weight.

It must be remembered that the speed of the boat does not
increase in direct proportion to the increase of power. Starting
with a given power, doubling the power will by no means double
the speed. The power required really increases as the cube of
the speed, so that to double the speed of the boat an amoimt of
power equal to 2X2X2 = 8 times the original power must
be installed. Doubling the power only increases the speed by
an amount equal to '^2 = 1.25 so that the speed is only a quarter
greater. This illustrates the futiUty of trying to drive a bulky,
heavy boat at a more than moderate speed. A small or moder-
ate power will drive the boat practically as fast as a greater power,
and much more economically, as so much of the greater power is
used up in piling up waves at and near the bow.

Quality of Engine and Cost. — As to the quality of the engine,
as good an engine should be bought as the money at hand wiU

132 MARINE GAS ENGINES

allow. A cheap engine, while low in first cost, has a short life
and is likely to break down in service and cause vexation if nothing
more. It should be borne in mind that it costs a certain amount
to build an engine, and although a saving may be made by economy
of production, the very cheap engine must be lacking either in
size or quaUty.

The ratings of the engines of the different makers vary greatly,
the ratings of similar engines varying sometimes as much as 50
per cent. It will be found that the extreme low priced engines
are rated at a very high rotative speed, in many cases much in
excess of what can be actually obtained in practice. The pro-
spective buyer should consider the bore and stroke of the engine
and form his own estimate of the probable power. By doing this
he will often find that to obtain his required power a size larger
than the rated size will be required, which brings the cost almost
or quite up to that of the more conservatively rated medixun
priced engine.

Another point to be considered is the question of "outfit";
some makers Ust the engine alone, with the outfit as extra items,
while others list the complete installation, including everything
necessary to install and run the engine. The latter is much the
better way, as the purchaser knows just what his outfit is to cost
him.

For use on salt water, the engine must have "salt water fit-
tings." This means that all parts coming in contact with the
water must be of composition; including propeller, shaft, stem
gland, and all screws and nuts. No steel and composition should
be allowed to be ia contact when in salt water, as the steel is
rapidly eaten away by galvanic action. In fresh water these
parts may be made of iron or steel without great detriment, but
even here the bronze is better.

The general construction of the engine should be carefully
examined; although the amateur can tell little as to the quahty
of material and workmanship, there are some points which can
be looked into. As to the quality of the material the word of the
builder must be taken.

One of the most important points is that the various parts
be readily accessible, for examination or adjustment. While it
is not of course intended that the engine shall be pulled down

SELECTING AN ENGINE 133

except in case of accident or overhauling, it is at the same time
very desirable that the parts be so arranged and fastened that
they may easily be taken down and examined or, in the case of
accident, repaired. An engine which is easily accessible is likely
to have better care and last longer than one which is not.

The bearing surfaces should be hberal, especially that of the
crank-pin bearing which is under a severe pressure. Some means
also should be provided for taking up the wear of all bearings
which are under heavy pressure. The main bearings should be
either of babbitt or bronze, and on four-cycle engines are usually
made so that any wear can be taken up.

INDEX

Arrangement of valves in four-
cycle engine 23

Bevel-gear reversing gear 93

Brake horse-power 125

Carbureter 28

Care of engines 117

Check valve 32

Combined coil and plug 45

Crank-pin oiling 72

Diesel engine construction 87

Diesel engine, principles of

operation 66

Disc clutch 96

Distributor construction 61

Dry cells 4S

Engine piping 105

Engine troubles 118

Forced-feed lubrication 73

Four-cycle engine S

Four-cycle engine construction . . 19

Hot-bulb igniter 73

Igniter mechanism 36

Ignition, make-and-break 35

Indicated horse-power 124

Indicator diagram 123

Installation of engines 103

Kerosine vaporizer 33

Lubrication 70

Magneto 48

Magneto circuits 51

Magneto, high-tension 48

Measurement of horse-power ... 125

Multi-cylinder engines 76

Oil engine, principles of opera-
tion 64

Oil engine, type 15

Operation of engines 113

Power of engines 122

Propeller definitions 98

Propeller measurements loi

Propellers 98

Reversing mechanisms 89

Reversing propeller 90

Secondary distributor 61

Selecting an engine 130

Sight-feed oil-cup 71

Spark coil 4o-44

Spark plugs 42

Spur-gear reversing gear 93

13s

136

INDEX

Three-port engine

Timer

Two-cycle engine construction.
Two-cycle engine — principles .

Vaporizers.

4 Water pumps 16

40 Wiring diagram for dynamo 63

9 Wiring for high-tension magneto. 62
2 Wiring for make-and-break

ignition 54

Wiring for multi-cylinder engines. 58

26 Wiring for jump-spark ignition . . $5

D.Van nostrand Company

are prepared to supply, either from

their complete stock or at

short notice,

Any Technical or

Scientific Book

In addition to publishing a very large
and varied number of Scientific and
Engineering Books, D. Van Nostrand
Company have on hand the largest
assortment in the United States of such
books issued by American and foreign
publishers.

All inquiries are cheerfully and care-
fully answered and complete catalogs
sent free on request.

25 Park Place - , _ New York