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THE NORMAN W. HENLEY PUBLISHING Co.

132 NASSAU STREET. NEW YORK

PRACTICAL SILO
CONSTRUCTION

A TREATISE

ILLUSTRATING AND EXPLAINING THE MOST SIMPLE AND EASIEST
PRACTICAL METHODS OF CONSTRUCTING CONCRETE SILOS OF
ALL TYPES; WITH UNPATENTED FORMS AND MOLDS. THE
DATA, INFORMATION AND WORKING DRAWINGS GIVEN IN THIS
BOOK WILL ENABLE THE CONCRETE BUILDER TO SUCCESSFULLY
CONSTRUCT ANY OF THE MOST PRACTICAL TYPES OF CONCRETE
SILOS IN USE TODAY.

By
A. A. H^OUGHTON

Author of "Concrete from Sand Molds," "Ornamental Concrete
Without Molds," Etc., Etc.

TWENTY ILLUSTRATIONS

NEW YORK

THE NORMAN W. HENLEY PUBLISHING CO.

132 NASSAU STREET

1911

COPYRIGHTED, 1911,

BY
THE NORMAN W. HENLEY PUBLISHING Co.

FOREWORD

IT is the purpose of the writer to present in this
series of books a complete explanation of various
successful methods of concrete construction that may
be employed by the beginner as well as by the more
experienced worker. I shall endeavor to give the
details of molds and ideas that are not covered by
patents, such as may be easily and cheaply con-
structed; hence the reader is not compelled to pur-
chase expensive patented molds before putting into
practise the many successful types of concrete con-
struction I have exhaustively described in this series.
There is no practical value to the reader in explain-
ing a patented system of construction, other than a
few words on its merits, as the owners of same are
always pleased to give this information; hence in
going outside the beaten track of concrete authors
and presenting ideas, systems, and molds that are
practical, successful in operation, and, above all,
easily and simply constructed, I trust that I have
merited the sincere gratitude of all fellow workers
in the concrete field who seek such information.
Yours very truly,

A. A. HOUGHTON.

215500

PREFACE

THE concrete silo has easily demonstrated its
superiority over all other types of silo construction,
and to-day stands, in the opinion of every practical
builder, as the nearest to perfection of any type of
structure for the preservation of green crops in si-
lage. When we hark back to the civilization of the
past centuries, we find that the silo is but another
modern adaptation of ancient building construction,
bringing more forcibly to our notice "that there is
nothing new under the sun."

In this treatise I have endeavored to show the
requirements of silo construction to insure success,
and the best methods of complying with these requi-
sites when concrete is the material for the struc-
ture. The importance of the foundation is fully
treated, as the structure can be no stronger than the
foundation upon which it rests, and it is far better
to err on the safe side in construction of the founda-
tion than to find it inadequate for the load it must
carry. As the solid wall silo is the usual type erected
at the present time in monolithic construction, I
have presented one of the most practical and posi-
tively the most simple and easily constructed wood
form that has been published up to the present time.

9

10 PREFACE

The fact that this wood-clamp silo form is rigid and
amply strong for the work of a construction that
requires the minimum of lumber, and is easily raised
in a manner that makes it almost impossible to get
the walls from a perfect vertical line, should be of
vast interest to every contractor or silo builder.

The molding of monolithic silo walls, with a
continuous air-chamber between same, is also fully
treated; one by employing a simple and easily con-
structed automatic wall-clamp, and also by the well-
known method of building the walls from blocks or
units.

The construction of silos from concrete plaster or
stucco is also explained, as well as the reinforcement
of silos, with tables for the proper placing of this
reinforcing material. The different types of silo
doors, and two methods of making a concrete roof —
plain and ornamental — for the silo, are explained in
detail.

Believing that this volume will fill every need of
the contractor for practical and easily understood
instruction upon this subject, and that it will be of
value to you, I am,

Very truly yours,

A. A. HOUGHTON.
February, 1911,

TABLE OF CONTENTS

PAGE

THE CONCRETE SILO 13

REQUIREMENTS OF A SILO 14

SIZE OF SILO TO ERECT 17

FOUNDATIONS FOR THE SILO . 20

FOUNDATION WITH FLOOR BELOW GROUND-LEVEL . . 23

FORMS FOR MONOLITHIC WALLS WITHOUT AIR-CHAMBER . 23

A SIMPLE AND INEXPENSIVE SILO FORM 25

METHOD OF RAISING FORMS . 32

USING AUTOMATIC CLAMP 35

PLASTERED SILOS 38

CONCRETE BLOCK SILOS 41

CONCRETE FOR SILO WORK . . . . . . . .49

REINFORCEMENT OF SILOS 50

DOORS FOR THE SILO . 55

SILO ROOFS 60

ORNAMENTAL ROOF OR WALL FOR SILO 62

PRACTICAL
SILO CONSTEUCTION

THE concrete silo has within the past year demon-
strated to the majority of builders its superiority
over all other types of silo construction. Not only
for the great durability of properly made concrete
does it base its claims for consideration, but in the
fact that it can be made water-proof and frost-proof,
as well as being absolutely air-tight, has done much
to advance the concrete silo in the favorable opinion
of the farmer as well as the builder. In the process
of ensilage we are only adapting to our present day
needs a method of preserving grains and green crops
that has been in successful use for centuries. The
fact that the masonry silos or granaries of the an-
cient Egyptians were built on practically the same
plan as our present-day silos, and that this method
of ensilage was in successful use for centuries, will
be of interest to the doubter who believes that stone,
either natural or artificial, is not the best material
for the construction of a structure for the preser-
vation of grain or any crop. In fact, the greatest
enemy of the concrete silo to-day is the man who

13

14 PRACTICAL SILO CONSTRUCTION

has a silo to sell of some other material. The unani-
mous verdict of those who have built of concrete is
that it has given the greatest satisfaction, with
practically no future expense for painting and re-
pairs, which is a large item with the wood and metal
silo. Adding to this the fact that a properly con-
structed concrete silo is everlasting, we have a bal-
ance in favor of concrete that no other building
material can hope to overcome.

The word silo is used to designate a closed pit or
reservoir, in which green fodder or dry grain may
be placed for preservation. Ensilage is the process
of preserving the grain or green fodder in the pit or
silo. Silage is the preserved fodder or grain, or
the results produced by the process of ensilage. In
present-day use the silo is employed for green crops
almost exclusively, and upon our dairy farms of this
country green corn is usually the material for our
silage; in other countries, clover and other grasses,
tares, rye, and oats, are used to produce silage.

REQUIREMENTS OF A SILO

The requisites of a successful silo are, first, its
air-tight features. This can be accomplished for the
first year or so in the lighter and less durable meth-
ods of construction ; but, after the first few years of
use, the seams or joints of the wood silo will spread
apart and thus admit air. This demands repairs;
and, in the years of use, it is easily to be seen that
the slight extra cost of a concrete silo is saved many

PRACTICAL SILO CONSTRUCTION 15

times over in the upkeep or repairs necessary to the
wood or metal silo.

These arguments, which are understood by those
who have had the experience, apply also to the other
features of a successful silo— durability, and a small
repair bill.

The silo is best when water-proof and frost-proof.
The penetration of moisture through the silo is very
apt to injure the silage, as the preservation of the
moisture is necessary to the process, while the freez-
ing of the silage is very annoying when feeding it
out, as large masses of it will adhere, by freezing,
to the wall of the silo, and cannot be removed until
thawed out. This does not injure the silage, but is
an annoyance when feeding the silage, in the winter
months.

The water-proofing of the silo can be easily ac-
complished by using any of the water-proofing com-
pounds on the market, or by making the concrete in
the walls as dense as possible. By using a wet mix-
ture of concrete, the mortar will the more tightly
pack together, thus reducing the size of the pores
for the admittance of moisture to the silage, as well
as preventing the moisture in the green fodder from
escaping through the walls. Again, by the use of
a brush, coat over the completed walls, of ordinary
Portland cement, one part; hydrated lime, one-half
part; this is mixed with water to the consistency of
paint and applied with a wide brush to the walls as
soon as forms are removed, and aids materially in

16 PRACTICAL SILO CONSTRUCTION

water-proofing the silo. In ordinary practise two or
three thin coats of this material applied over the
walls will be ample water-proofing for the purpose,
as this brush coat fills the pores of the concrete in
an effective manner. Caution must be observed
in using this brush coat, that it is not applied too
thick, as then it will craze or check, thus supplying
cracks for the admission of moisture. By having it
quite thin, and brushing well when spreading, the
purpose is accomplished with two coats, successfully
filling the pores but not applying more material than
will perfectly bond with the concrete in the wall.

The thickness of wall does not prevent the free-
zing of the silage, for concrete, as with stone ma-
sonry, is not frost-proof in any ordinary thickness
as employed for walls. The most successful method
to avoid freezing of the silage is to build double
walls to the silo, with an air-chamber between same.
This is accomplished in the block construction and
also in the monolithic type of construction. While
freezing is not an injury to the silage, the protection
of a double wall against same is a positive preventa-
tive against this annoyance in feeding — a feature
that is of value in our cold winters of the Northern
States.

The double wall silo with sealed air-chambers is
also an assurance against the danger of air reaching
the silage, as well as moisture penetrating the walls.

PRACTICAL SILO CONSTRUCTION 17

SIZE OF SILO TO ERECT

The diameter of the silo should not be larger than
will enable the silage to be fed from the entire top
each day. If the top is not fed out every twenty-
four hours the silage is apt to mold; so, in construc-
tion, the number of animals to be fed from same
should be the greatest consideration in planning the
size.

A cubic foot of silage will vary in weight from 35
to 50 pounds. In estimating, 40 pounds to the cubic
foot may be taken as the weight, with safety, in
approximately determining the storage capacity of
the silo.

The amount fed to a cow each day varies from 40
to 60 pounds, when used with other feed ; hence, by
employing a safe average of 50 pounds daily for each
animal, it is possible to estimate the best size of silo
to erect for the purpose, as each animal at this rate
would consume three-quarters of a ton in each thirty
days. It is always better to err slightly on over-
capacity than otherwise, as the settling of the silage
that takes place after filling will vary with the con-
dition of the fodder at the time of filling; so this can-
not be positively estimated. This is, of course, only
in reference to the height of the silo, as the layer
that is to be removed each day in feeding, to prevent
molding of the ensilage, can be accurately deter-
mined so as to consume a layer of two or three
inches in depth daily.

18

PRACTICAL SILO CONSTRUCTION

The following table will enable the size of the
silo to be quite accurately estimated as to height
when the diameter has been determined. Thus, by
multiplying the capacity per foot of height by the
proposed height of silo, you easily secure the ap-
proximate capacity in tons.

TABLE I

SIZE OF SILOS

diameter contains f ton to each foot of height.

1

1 J to
3
4

Q S

ns to each foot of height.

. .. ,

t t

< « t

, .

6'

8'
10'
12'
U'
15'
16'
18'
20 '
25'

The usual practise is not to make the inside di-
ameter of the silo greater than one-half the height,
consequently a diameter of more than 20' inside
is not often required; where larger quantities are
needed the best practise is to build several silos of
smaller diameter and capacity, thus exposing as little
of the silage to the air between feeds as possible.

By the table given it will be seen that, to furnish
the silage ration for a herd of 10 cows — the lowest
number that it is practical to build a silo for — they
will consume about one-fourth of a ton daily, or 45
tons in 180 days, 60 tons in 240 days. This would
require a silo 10 ' in diameter and 33 ' in height for
6 months' feeding, allowing 3' for the settling of

PRACTICAL SILO CONSTRUCTION 19

the silage, which cannot be accurately estimated, as
heretofore explained. In a silo 12' in diameter the
height for 6 months' feeding would be 23', with
the same allowance for settling. For 8 months'
feeding the height of a 12' silo would be 30', on the
above basis. As the 10 ' diameter would permit the
feeding of 500 pounds daily to remove a 2" layer
of silage, while the 12' diameter would remove ap-
proximately about |", it will be seen that the 10'
diameter would be the most practical from an eco-
nomical point of view.

LOCATION OP SILO

The location of the silo should be such that it
permits easy feeding, and when possible to place
upon the south of the barns there is always less
annoyance in removing the silage in bad weather,
when it is constructed separate from the barn ; also
the animals may then be often fed in racks in the
yard with less labor in placing the silage before them.

Where the floor of silo is placed too far below
ground-level it is found to be more annoyance in re-
moving the last few feet of silage; hence the floor-
level should not be more than 4 ' below ground-level
to insure an easy removal of the contents. The mat-
ter of drainage is not needful to consider, as the
material placed in the silo has a large percentage of
water, which the silo must retain to prevent the
silage from "dry firing"; so the foundation should
be made as water-proof as possible, which will

20

PRACTICAL SILO CONSTRUCTION

also keep out the surface water as well as retain
the moisture in the silage,

FOUNDATIONS FOR THE SILO

These must be given careful attention, as the life
of the structure depends upon same. The practise
of constructing the foundation in a haphazard man-
ner is to be regretted; for, when we consider the
weight of the concrete structure, as well as the weight
of the column of silage it contains, the vast impor-
tance of amply protecting this in constructing an
adequate foundation is easily to be seen.

At Fig. 1 is shown the usual type of foundation
for a concrete silo, where the floor of same is at
ground-level, as indicated at a. The dotted lines
at 6 show the form of constructing footings, which
are determined by the size of silo.

The following table will aid in determining the
diameter and size of the footing courses for the
different sizes of silos usually constructed.

TABLE II

DIAMETER AND SIZE OF FOOTING COURSES

Diameter of Silo
in Feet.

For Stone, Clay, or Gravel.

For Sand or Loam Soil.

A.

B.

C.

D.

A.

B.

C.

D.

10 ' .

to to co «o co co co

<N *•# CO t> CO O <N
rH r-t i— 1 r-t r-i <N CM

j to to to to to to to

1
1
1
1
1
1
1

12 "
12"
IS"
IS"
U"

16"

CO CO CO CO CO CO CO
CO 1C t- 00 Oi i-l CO

r-1 rH r-l »-l i— 1 C<i C\J

V V V V ^ V V

CO CO CO CO CO CO CO

00 CO 00 00 00 CO CO

12 "
12"
13"
13"
14 "
15*
16"

12'

14'
15 '

16 '

18'

20 ' . ...

FIG. 1. —Foundation for a silo with floor at ground-level.

22 PRACTICAL SILO CONSTRUCTION

In the preceding table, A refers to the outside
diameter of the foundation, including footing; B to
the width of the footing or bearing course on the
soil; C to the thickness of the footing course, and
D to the thickness of the wall of foundation that
rests upon footing course, and extends to ground-
level.

The foundation course should be placed of con-
crete that is not leaner than 1:2:4 of well-graded
sand and gravel or crushed stone. This is well
tamped, and allowed to harden permanently before
the walls of silo are erected upon same, otherwise
the weight of the concrete placed [upon the foun-
dation may develop defects in the foundation that
would not happen if it had ample time and oppor-
tunity to thoroughly cure before the walls were con-
structed above ground-level.

Where the soil is firm the excavation can be em-
ployed to furnish the mold for the outside walls of
foundation, by cutting it down to the size desired;
the forms for the inside wall surface can then be
erected and the concrete placed.

Where the forms will permit, the floor of silo can
be laid at the time the foundation is placed, and thus
form a part of same ; but, where the wall forms de-
mand supporting uprights inside the silo, the floor
must then be placed after the silo walls are com-
pleted.

PRACTICAL SILO CONSTRUCTION 23

FOUNDATION WITH FLOOR BELOW GROUND-
LEVEL

At Fig. 2 is shown the usual type of silo founda-
tion, where the floor-level is below the ground-level,
which is designated by a a in illustration. The
footing course is shown by the dotted lines 6 6, and
at all times forms a part of the foundation-wall to
ground-level. The best practise is to also make the
footing-course a part of the floor of silo, although it
cannot be done when uprights must be erected in-
side the forms, as previously explained; in which
case the footing extends the proper distance outside
and inside the foundation-wall, as shown by dotted
lines, and the floor is laid inside this when the silo
walls are complete. Where the silo floor is not laid
with the foundation, extreme care must be employed
to make the joint between edge of floor and footing
water-tight, otherwise surface water will collect in
the bottom of silo.

The thickness of foundation-walls, given in Ta-
ble II, apply to the foundations where the floor is at
ground-level as well as to those below ground-level.

FORMS FOR MONOLITHIC WALLS WITHOUT
AIR-CHAMEER

After the foundation-walls have had ample time
to permanently harden — so that they will bear the
weight of the concrete for walls of silo — the forms
for the type of wall you desire to erect are placed,
with the necessary staging or uprights to carry the

FIG. 2,— Foundation for a silo with floor below ground-level.

PRACTICAL SILO CONSTRUCTION 25

wall forms to the height of the silo. These uprights
should be placed plumb, and securely braced or held
by guy wires or ropes, so that they will serve as a
guide in building the silo walls absolutely vertical.

A SIMPLE AND INEXPENSIVE SILO FORM

The most simple silo form or centering, and one
that requires the least amount of lumber to erect, is
shown in detail in Fig. 3. The wood clamp is built
of 2x4" strips that are at least 12" longer than the
sheet steel used for centering is wide. Thus, if the
sheet steel is the usual size of 24x101", the sides
of the clamp will be 3 ' in length. The upper cross-
piece to clamp is cut long enough to lap onto the
side-pieces and leave space for the silo wall of the
desired thickness between the vertical strips. This
can be made longer, and then holes bored in same so
as to enable the worker to regulate the width of the
wall from 6" to 12" in thickness, or more, as may be
desired, thus making the same form adaptable to
different sizes of silos.

The long strip, shown in Fig. 3, is of sufficient
length to reach entirely across the diameter of the
silo and then lap onto the vertical strips, to which
the sheet steel is attached at each side. Thus, for a
silo 10 ', inside diameter, this piece would have to be
12' long, to permit an 8" wall to be molded. This
strip is bolted to the vertical strips, as illustrated,
and also bolted to the clamp upon the opposite side
of the silo.

26 PRACTICAL SILO CONSTRUCTION

As the weight of raising the forms is largely upon
these pieces, they should be at least 2x6" and of
selected wood, so that they will not bend or break
from the strain.

A number of the clamps are constructed so
that they will hold the sheet steel to the true
circle. This requires less where the 24-gauge steel
is employed than where lighter weight sheets are
used.

The arrangement of the clamps and braces are
shown in the plan of one-half of silo form, at Fig. 4,
in which a a refers to the central vertical upright
used to raise the silo form, as required; b b is the
2x6" strip extending across the top of the silo form,'
by which it is raised; c c are the guide-strips em-
ployed to keep the silo form level when it is raised,
and also when the weight of concrete is all upon one
side of form; d d illustrates the position of the wood
clamps or vertical strips attached to the horizontal
2x6" strip, as explained for Fig. 3. The clamps
designated by this letter at the quarter segment of
silo form are connected to the main horizontal strip
by two brace rods, //, which may be made of 2x4"
lumber, bolted to the clamp and also to the sliding
guides c c at center. The clamps e e, shown be-
tween the quarter segments of circle are simply
employed to keep the sheet steel to the true circle.
These need not be as strong construction as the
clamps placed at each quarter of the circle, and are
held from spreading or warping from position by

[IP

FIG. 3.— Wood clamp for molding monolithic walls.

28 PRACTICAL SILO CONSTRUCTION

the braces g g, as shown in plan. The number of
these clamps must be determined by the diameter
of the circle, but should never be less than two,
placed between each clamp at the quarter segment
of circle; nor, when the 24-gauge sheet steel is em-
ployed, should they be more than 36" apart on the
outside circumference of circle.

The strips shown at h h in Fig. 4, cut along one
edge in a convex form, may be employed to keep
the sheet steel from bending under the weight of
the concrete. These are cut in the proper segment
of circle so that they will fit between each clamp,
around the inside circumference of your circle.
Those shown at i i are cut in a concave form and are
fastened to the outside circumference of your circle,
between clamps. By using these retaining strips,
or pieces of strap, iron bent into the same form and
riveted to the sheet steel, the lighter weight steel
may be employed. Thus, with three of these re-
taining strips between each clamp, No. 28-gauge
sheet steel has been successfully employed for the
forms or centering.

The value of employing the retaining strips and
using a lighter grade of sheet steel is that the forms
will thus be made lighter, as the 24-gauge sheets
weigh about 17 pounds to the sheet of 24x101"; the
26-gauge weighs 13 pounds to the sheet, while the
27-gauge weighs 111 pounds, and the 28-gauge
weighs but 10J pounds to the sheet. This is also
able to effect a saving in the cost of the forms, as

FIG. 4.— Plan for clamps and braces used with wood silo forms.

30

PRACTICAL SILO CONSTRUCTION

there is a difference of 20 cents a sheet between the
28-gauge and the 24-gauge.

The following table shows the number of sheets
of steel required for the forms or centering for
various diameters of silos, with the approximate
circumference of the inside form or core, also the
number of wood-clamps demanded for the forms to
insure their being held rigidly in position.

TABLE III

STEEL SHEETS REQUIRED

Inside
Diameter
Silo.

Inside
Circumference
Core.

Number
of Sheets
for Core.

Number
Sheets
Outside,
6 "Wall.

Number
Sheets
Outside,
8 "Wall.

Number
Sheets
Outside,
10 'Wall.

Clamps
Required
for Form.

10'

31 ' 4 "

4

4

5

5

12

12 '

37 ' 6"

5

5

5

6

12

14'

44' 0"

6

6

6

7

12

15'

47' 1"

6

7

7

7

16

16'

50' 2"

7

7

7

7

16

18'

56' 6"

8

8

8

8

20

20'

62 ' 8 "

8

9

9

9

20

i

If no other means for bending the sheet steel to
the required curve are at hand it may be placed over
a round stick of at least 6" in diameter, and, by
fastening one end securely and exerting pressure
upon the opposite end of sheet, it can be bent to
conform to the desired curve. The above table
shows the number of the usual sized sheets to order
for both outside and inside, or core form. These are
bent to the desired curve and then cut so to have
the form meet exactly at the four quarters of the
circle. By thus making the centering in four quar-

PRACTICAL SILO CONSTRUCTION 31

ter segments of a circle they are the easier taken
down and assembled again. Where the diameter of
silo is 18' or 20' the forms can be built in one-
eighths, or segments equal to one-eighth of the entire
circumference of circle, thus making the weight of
each section less than if made in quarters. The
segments or sections are bolted together, when in
use, by bolts through the two clamps, that join to-
gether at the point, where each segment joins onto
the next section. Thus, by placing a clamp at both
ends of each section, whether quarter sections or
eighths, the joining of sections is a simple matter
of bolting the clamps together, making the work of
assembling the forms a very easy and simple job.

The method of bolting these wood-clamps to-
gether is shown by the position of the clamps at d d
in Fig. 4, and also by the holes in clamps shown in
Fig. 3, thus making a simple and easily operated
method of securing the joints. As the sheet steel
can be bent slightly, the forms may be built to be
adjustable to many different sizes of silos. Thus, if
the forms are erected for a 10 ' silo, using 4 sheets
for the core form and 5 sheets for the outside form,
the steel centering is attached to clamps with
screws, placed through holes punched in the steel
sheets. Then, to adjust to a 12' silo, you would only
have to add a portion of one steel sheet to the core
and outside form and adjust the clamps around this
new size of circle. This makes it easily possible to
erect any diameter of silo with the one set of clamps

32 PRACTICAL SILO CONSTRUCTION

and steel centering by adding or removing sections
to make up the desired circumference.

Where it is desired to erect an 8 " or 10 " wall for
a portion of the height, finishing with a 6" wall,
two sections of the form are fitted with steel sheets
to make the desired circumference. Then, when the
thickness of wall is to be reduced, the clamp is
slipped along the length of these sheets, allowing
the surplus length of sheet to lap over onto the one
that joins to same, thus reducing the circumference
of circle to mold a wall of the required thickness.
This leaves a mark of mold or indentation upon two
sides of silo, where the sheets lap; but, as this is
slight it will not be a serious defect to the work.

METHOD OF RAISING FORMS

The method of raising the forms after each
course is placed is shown at Fig. 5, as well as a
cross-section of wall and the molding form or cen-
tering. The vertical post shown at a a is made of
two 2x8" strips, placed together with a space be-
tween them of 2", so as to permit the braces b b to
slide between same as the silo forms are raised.
The two vertical strips, c c, are guides that are
bolted to the horizontal braces b b, and by press-
ing against the vertical posts a a the silo form is
kept from tipping to one side; nor is it allowed to
be raised higher at one side than the other. This is
a most important feature, and these guides should
never be left off the form, otherwise you will have

*£t

',?*.'

•"./

^v\

** i^-
'».

//

/,'r.

II
tf

\

\

\\
v\
\\

L., 1

Li

FIG. 5. — Sectional view of silo forms in operation.

34 PRACTICAL SILO CONSTRUCTION

no assurance that the form will not be raised higher
upon one side than upon the opposite side of silo,
thus throwing the wall from the vertical line or
plumb. With every silo form heretofore explained,
this feature has never been given attention; and its
importance is apparent to any one at a glance, as it
insures a perfect wall without the bother of leveling
the form each time after raising. The clamps at
sides are shown by d d; and, as the same designating
letters are given to each part in Fig. 5 as in Fig. 4,
it is an easy matter to understand the invaluable
and important features of this simple and easily
constructed silo form.

The tackle used to raise the forms is shown by
the dotted lines in Fig. 5. The wire cable, or ropes,
pass down upon one side of the posts, in center, to a
drum or roller at the bottom of same. This drum is
fitted with a ratchet-wheel and pawl, to lock the
drum at any point desired, also with two arms, or
cranks, for moving the drum. Hence, with two men,
the form is very easily raised each time in a far
more simple and desirable manner than by wire
loops over levers, which do not raise the forms
evenly, and consequently require greater effort, with
danger of breaking out pieces of the concrete wall.

The vertical posts in center of Fig. 5 are braced
at the bottom by horizontal pieces bolted to same.
This is made so as to have ample bearing surface
upon the ground, so the weight of forms will not cause
it to sink or bury into the earth at one side, and thus

PRACTICAL SILO CONSTRUCTION 35

draw the wall from the vertical or plumb line. With
this form of post the concrete floor may be laid in the
bottom of the silo, and the uprights set upon same
without injury. By keying or bracing this securely
at the bottom, and staying the top of the post with
guy wires, the walls of silo must be built absolutely
plumb, for the forms cannot be raised in any other
manner. This "fool-proof" feature will be of in-
terest to the contractor who must intrust his work
to others ; and, as mistakes in this work are costly,
every safeguard against errors is of great impor-
tance.

This style of form permits the placing of any re-
inforcement desired. The upright rods are placed
with the first course of concrete, spacing them the
proper distance apart. These are held in a vertical
position by braces nailed to the top of the center
posts until the wall has advanced enough to hold
them securely. Then the braces can be removed, to
finish the silo.

By nailing short strips to the center posts, hori-
zontally, a ladder can be made for convenience in
reaching the forms at every stage of the construc-
tion.

USING AUTOMATIC CLAMP

The illustration at Fig. 6 shows the use of the
automatic wall-clamp, explained in CONCRETE WALL
FORMS of this series, as adapted to silo work. This
permits the molding of a hollow wall with a continu-

FIG. 6.— Using automatic wall-clamp, as explained in
CONCEETE WALL FORMS, for silo work.

PRACTICAL SILO CONSTRUCTION 37

ous air-chamber between the walls, a feature that is
an absolute preventative against freezing of the
silage.

These wall-clamps are constructed of strap iron,
and may be built by any one at a slight cost. The
steel sheets are bolted or riveted to the clamps as
shown in Fig. 6, and each section is then bolted to-
gether or fastened with a small clamp, if the sec-
tions are to be raised separately. The core form
collapses when the center-bar with handle is raised.
This same operation causes the outside forms to
draw away from the concrete wall, thus freeing the
form from the concrete at all points.

When the form is again lowered into position the
core is pressed outward to its proper place, and the
outside forms drawn in to the correct circumference.
The simple act of lowering the form automatically
locks it into position for filling, while the small
metal bars at the bottom of the center-bar engage
with the concrete wall and prevent the centering
from slipping down.

The sections are reinforced with bars of strap
iron riveted to the sides of the steel sheets, as shown
in illustration, thus holding them to the true circum-
ference of the circle.

The easiest method of using this style of form is
not to have more than two or three clamps to each
section, thus making the sections quarters or eighths
of the circumference of the silo. These sections
are raised separately by removing the small clips or

38 PRACTICAL SILO CONSTRUCTION

clamps holding the sections together. Each section
can be raised and then the segments or sections
again fastened together, avoiding the use of any
tackle to raise the forms after each course, as two
men can lift the sections from the staging erected
for the workmen in placing the concrete.

By having small segments or sections the forms
can be employed for many sizes of silos, by adding
or removing a section as demanded, which is a valu-
able feature to the contractor who must build all
sizes of silos.

PLASTERED SILOS

A successful type of silo construction has been
recently used; and that it is exceedingly practical is
shown by the illustration at Fig. 7, which illustrates
the method of arranging the vertical and horizontal
reinforcement and also the use of the wire lath that
is attached to same.

This type of silo construction employs the placing
of § " vertical rods around the circumference of silo,
ground plan, as per the spacing for diameter given
in Table IV. To this is added the horizontal or
"hoop" reinforcement, using §" rods, and spacing
them as instructed in Table V. These horizontal
rods are tied with wire to the vertical rods at each
point they intersect, thus making a skeleton or "bal-
loon" frame of the silo.

The vertical and horizontal rods are placed so
that they will be about 1J " from the outside of the

FIG. 7.— Method of constructing plastered silos.

40 PRACTICAL SILO CONSTRUCTION

completed wall, which is usually made about 3J"
in thickness.

After the framework of rods are in place, sheets
of wire lath, or expanded metal lath, are fastened to
the rods by tying with wire at each intersection of
the rods and also at the joints of the metal lath, so
that the sheets are securely fastened to the frame-
work, and thus make a reinforcement that will be
ample to resist the pressure of the silage, also the
strain placed upon the silo from other causes.

The concrete is then plastered upon the inside of
the silo to an average thickness of 2", and while this
is damp enough to insure a good bond the plaster
coat is then placed upon the outside of the metal lath.
The methods followed in stucco work are of use in
this system to insure a good bond between the two
coats of concrete plaster applied.

The door-frames are inserted in spaces left for
same as the work progresses. By having a groove
on the outside of the door-frame into which the
metal lath will fit, the frames are securely held in
position. The roof is placed by having the | " rods
extend several inches above the top of silo, and these
are threaded for a nut. Thus the rafters are bolted
to the vertical rods that form a part of the reinforce-
ment of the structure.

This system of construction is far in advance of
the method of using a wood frame, to which wood
lath are nailed and the entire surface coated with
concrete plaster coats.

PRACTICAL SILO CONSTRUCTION 41

The plastered silo may be constructed with a con-
tinuous air-chamber by attaching the wire lath to
the outside and also to the inside of the |" rods.
By plastering upon each side a space is left between
the plaster coats that is a preventative against frost
in the silo.

CONCRETE BLOCK SILOS

Silos of concrete blocks, or units, have been em-
ployed so generally that a description of this type of
construction is not needful to the average concrete
contractor. The manufacturers of concrete block
machines put out a silo block machine for molding
hollow building blocks for any diameter of silo, thus
making the construction of the units the same as the
manufacture of building blocks for any type of wall.

For the man who desires to make his own blocks,
the type of mold shown in Fig. 8 is of value, as this
molds a wet process hollow block. The molds are
easily constructed by using two planks for the sides.
In width these should be about 2" more than the de-
sired width of block (or thickness the wall is to be)
at the points where the desired height of each block
is measured. The planks are cut with a saw kerf
for 3 " in depth. These are to receive the sheet iron
dividing plates between the blocks, as illustrated.
A convex form is built for the bottom of mold from
wood strips, cut into the proper curve for the seg-
ment of circle the block is to take, on the inside of
silo. These strips are covered with sheet iron, and

FIG. 8.— Mold for silo blocks, wet process.

PRACTICAL SILO CONSTRUCTION 4&

the form constructed to make a bottom for the en-
tire length of the mold.

The sheet iron dividing plates are cut in the con-
vex and concave form shown in Fig. 9, at top. The
length is equal to the length of the block, plus 4 " at
each end for inserting in the saw kerf and for a hole
in the ends for putting an iron pin into, to hold the
side forms or planks tightly up against the " shoul-
der" cut upon the dividing plate.

A beveled or triangular strip of wood is now cut
of the exact length of the block. This, by soaking
in water, can be bent to the curve of the block, and
is then nailed to the top of the dividing plate, or
about li " from the top, as shown in the illustration
at Fig. 9. This molds a groove in the silo block for
the placing of the hoops or wires used as reinforcing
material. This groove is shown in the completed
block at Fig. 9.

Below the triangular strip, round holes are cut
for inserting lengths of gas-pipe, which mold the
hollow spaces in the blocks. These pipes are well
greased when the mold is assembled and also slightly
flattened at one end, into which a key or crank is
placed for turning the pipe around before removing
same from the completed series of blocks. This is
necessary, as otherwise the pipes could not be as
easily drawn; but, by breaking the bond, if any, be-
tween the pipes and concrete, they are withdrawn
quite easily.

Two of the dividing plates are used between each

FIG. 9.— Sheet iron dividing plate and completed silo block.

PRACTICAL SILO CONSTRUCTION 45

block, or one dividing plate with a triangular strip
upon each side, so as to mold the channel or groove
for wires into both sides of block.

The form is now assembled in the manner illus-
trated in Fig. 8, and the concrete placed in the
mold, finishing the top with the trowel, or using a
template of the desired curve. The concrete is placed
wet and the blocks allowed to cure in the mold, when
the iron pins through dividing plates can be drawn
and the side planks removed, thus releasing the en-
tire series of blocks, which can be as many as the
length of plank will accommodate.

The wood portions of this mold should be well
treated to several coats of shellac or oil paint, so as
to prevent the moisture in the concrete from warping
the wood. The concrete is placed wet; thus a dense
block is obtained with but little tamping.

The method of laying the blocks is shown in Fig.
10, also the usual manner of securing the door open-
ings.

While not necessary, a wire hoop can be placed in
each course of blocks in the groove or channel for
that purpose. This will bring the reinforcement the
height of the block apart. Thus, if a block 7J " high
is employed the reinforcement should be ample for
any strain it will be required to withstand. This
can be placed in each second course of blocks for the
5 ' of distance from the top of the silo downward,
if No. 5 wires are used for the wire hoops, and
make the wall of ample strength.

FIG. 10. — Reinforcing block silos and molding door-openings.

PRACTICAL SILO CONSTRUCTION 47

For the door-openings a double length block is
constructed, as shown in illustration. This should
be of the proper curve to conform to the circumfer-
ence of circle, and also be reinforced with at least
three § " rods placed horizontally in same. Two of
these rods are placed within about 1 " of the bottom of
block, which forms the upper part of the door-frame ;
the third rod is placed about 3" above this, and may
be further strengthened by short stirrup rods con-
necting the horizontal reinforcement. The door-
frames may be set in position as the blocks are
placed; and, by attaching to the reinforcement of
the silo, the frames are thus held rigidly in posi-
tion against the pressure of the silage.

At Fig. 11 is shown a plan of laying the silo
blocks so as to make a continuous door-opening from
top to bottom of the silo. The blocks are molded or
cut at the point they intersect at the door-opening
so as to lock in the manner shown. This can be accom-
plished by using a block of wood set vertical in one
end of the mold used for these blocks, and thus saving
the labor of cutting each block to join in this manner.

The reinforcing wires are bent to form a contin-
uous reinforcement or bond to the end of the door-
opening.

In constructing the blocks for a known size or
diameter of silo it is an easy matter to make them
of a length so that it requires a certain number of
blocks to make the exact circumference. Then, by
molding a number of half blocks, the joints may be

FIG. 11. — Ground plan of silo with continuous door-opening.

PRACTICAL SILO CONSTRUCTION 49

broken in each course laid, and the work of laying
greatly simplified. This can also be arranged so as to
bring the hollows or holes in blocks made by the gas-
pipe exactly over those in the block below, thus per-
mitting vertical reinforcement, if so desired.

CONCRETE FOB SILO WORE

For the manufacture of silo blocks or monolithic
silo walls the usual mixture is 1:2:4, using clean,
sharp sand that is well graded, and crushed stone or
coarse gravel for the larger aggregate. This should
not be over J " in diameter. The materials call for
thorough mixing and enough moisture to completely
wet the mix. This makes it impossible to raise the
forms until the concrete placed has had time to
harden or set. While this may seem a hardship to
the contractor in a hurry, it is the one and only safe
policy, even when a semi-dry mixture is employed.
Many jobs are injured by haste in construction ; for,
if the concrete has not had from 24 to 36 hours to
harden, even under the most favorable conditions it
is a menace to the workmen employed on any job
where the concrete must support the staging or scaf-
fold. Where the forms can be filled in a few hours
or one-half a day, the concrete can easily be given
24 hours to harden without delaying the work.

Where the mixture is made semi-dry it must be
tamped very solidly ; but in the event of a wet mix-
ture the tamping can be replaced by placing the
mixture in thin layers or courses and pressing it out

50 PRACTICAL SILO CONSTRUCTION

against the forms or "puddling." The wet mix will
thus pack more solidly than a semi-dry mix well
tamped, hardening with equal speed under favorable
conditions, and giving a smoother and more perfect
finish to the surface of walls.

The composition usually employed for plastered
silos is the same as that used for stucco; and often
a small amount of plastering hair is added to the
mixture. Where lime is added to the mix the
usual proportions are 2:5:1, cement, sand, and lime.
Without the addition of lime the best proportion is
1:2J, using well-graded sand, although a proportion
of 1:3 has been employed with success. The use of
lime, either the hydrated lime as sold almost exclu-
sively to-day or the cream of lime prepared by the
plasterer as needed, is of advantage in the concrete,
as it gives it great plasticity and lightens the work
of spreading to a large extent.

REINFORCEMENT OP SILOS

The question of reinforcement is an important
one to the silo builder; and in planning and placing
the steel every precaution should be taken to pre-
vent a weak point in the work.

At Fig. 12 is shown a type of reinforcement that
employs vertical |" rods around the wall of silo,
except upon each side of the door-openings, where
the rods are replaced by 2" angle irons or bars.
These are connected together between each door-
opening with a horizontal bar of the same material

FIG. 12.— Silo reinforcement and method of placing.

52

PRACTICAL SILO CONSTRUCTION

bolted to the uprights. The hoops or wires extend-
ing horizontally around the silo wall are tied to the
angle bars, thus forming a continuous reinforcement
entirely over the wall of silo. By referring to the
drawing at Fig. 12 the advantages of this type of
reinforcement is easily seen ; and, as it is simply con-
structed, there is nothing to prevent its general use.
For the vertical reinforcing rods there is nothing
as satisfactory as those of !" in diameter. These
weigh .375 of a pound to the foot; and, when spaced
around the circumference of the silo, as explained in
the following table, make a reinforcement that will
support its own weight and the reinforcement added
to same without bending or becoming displaced, as
is usually the trouble with vertical reinforcement
formed of wires.

TABLE IV

VERTICAL REINFORCEMENT AND SPACING f " RODS.

Height of Silo
in Feet.

To 25'.

To 30'.

To 35'.

To 40 '.

No.

Space.

No.

Space.

No.

Space.

No.

Space.

10 ' to 14 ' Diam.
14 'to 17 ' Diam.
18 ' to 20 ' Diam.

1
1

30"

28"

1
1

19 "
24"

2
1
1

26"
17"
20"

2
2
1

19"
27"

17"

The height of silo is given in the first line, and
the number of rods to use, spaced at the proper dis-
tance apart, in the second line. Thus, in a silo 10 '
in diameter and 25' high, one f" rod is used for

PRACTICAL SILO CONSTRUCTION

53

vertical reinforcement, each 30 " of the distance
around the circumference;

The horizontal reinforcement may be rods or
wires (where rods are used the most satisfactory are
those I" in diameter), while No. 5 and No. 8 wire is
usually employed for the horizontal hoops, as they
are easier bent to the proper circle than § " rods.

TABLE V

SPACING HORIZONTAL REINFORCEMENT OR HOOPS.
Distance Measured from Top of Silo in 5' Spaces

1-5'.

2-5'.

3-5'.

4-5'.

5-5'.

6-5'.

7-5'.

8-5'.

Diameter

Size of Rods or

Silo Inside.

Wires Used.

N.-S.

N.-S.

N.-S.

N.-S.

N.-S.

N.-S.

N.-S.

N.-S.

10'— 14'

1-18"

1-18"

1-15"

1-14"

1-11"

1-9"

1-8"

1-7"

|"rods

10'— 14'

1-16"

1-11"

1-8"

1- 6"

2- 9"

2-7"

2-6"

2-5"

No. 5 wire

10'— 14'

1-12"

1-7"

2-9"

3-9"

3- 8"

3-7"

3-6"

3-5"

No. 8 wire

14'— 17'

1-18"

1-18"

1-14"

1-11"

1-9"

1-7"

1-6"

1-5"

|"rods

14'— 17'

1-12"

1- 9"

1-6"

2-8"

2-7"

2-5"

3-7"

3-6"

No. 5 wire

14 '-17'

1-11"

1- 5"

2- 7"

3-8"

3- 6"

3-5"

3-5"

3-4"

No. 8 wire

18'— 20'

1-18"

1-18"

1-12"

1- 9"

1-7"

1-6"

1-5"

1-4"

i'rods

18 '_ 20'

1-12"

1-7"

2- 9"

2-7"

3-8"

3-7"

3-6"

3-5"

No. 5 wire

18'-20'

1-9"

2- 9"

3-9"

3- 6"

3-5"

3-4"

3-3"

3-3"

No. 8 wire

The distance from the top is measured in spaces
of 5'. Thus, in the first line, 1-5' refers to the first
5 feet from top o± silo downward; 2-5' is the second
5'; 3-5' is the third 5'; or 15' from top of silo, and
in this manner to the distance to 8-5 ', or 40 feet,
measured downward from top of silo. The great-
est pressure is at the bottom of silo, the silage ex-

54 PRACTICAL SILO CONSTRUCTION

erting a side pressure of about 11 pounds to each
square foot, for every foot of depth.

In the next line N. refers to the number of rods
or strands of wire used for each hoop or horizontal
reinforcement. S. refers to the distance in inches
these hoops or horizontal reinforcements are spaced
apart. The first column states the inside diameter
of the silo, while the last column states the size of
the wire or rods used.

Thus, for a silo 10 'to 14 ' in diameter we would
use 1, | " rod, spaced 18 " apart for the first 5 ' from
the top, also for the next 5 ' to 10 ' ,' 15 " apart for 10 '
to 15', 14 " apart for 15' to 20', 11 " apart for 20' to
25 ', 9 " apart for 25 ' to 30 ', 8 " apart for 30 ' to 35 ',
and 7 " apart for 35 ' to 40 ', thus bringing the great-
est strength of the reinforcement at the bottom of
the silo, where the greatest pressure is exerted by
the column of silage.

The hoops or horizontal reinforcement should be
tied to the vertical rods with wire. These may be
added as the forms are filled and raised, so they will
not interfere with the clamps used on the forms.

The system of reinforcing given is ample for a
wall of 6" in thickness or greater when made mono-
lithic, or it may be applied to plastered silos where
the wire lath or expanded metal lath is securely tied
to the reinforcing wires and rods.

PRACTICAL SILO CONSTRUCTION 55

DOORS FOR THE SILO

The usual size of silo door is 24x30", and in some
types of construction the height has been increased to
36 ". The door should be amply large so as to permit
the easy removal of the silage, yet if made too large
there will be a weak point in the wall by the exces-
sively large opening. For a door 24 x 30 " they should
be spaced 5 ' 6 " apart, center to center, on the wall
of silo, beginning at a point about 3 ' from the bot-
tom on a silo with floor at ground-level and about
18" above ground-level, on a silo where the floor is
below ground-level.

At Fig. 13 is shown two types of silo doors. That
at a has a channel or groove molded upon the inside
of the silo wall, into which one side of the silo door
fits tightly. The door is built of an outer and inner
sheathing of tongued and grooved lumber, nailed to
4 or 6 cleats of 2x4" lumber, which are in length
equal to the width of the door. The door shown at
a fits tightly into the opening; and, with strips of tar
paper inserted around between door and frame, the
joint is made air-tight.

The type of door shown at b (Fig. 13) is made of
the tongued and grooved lumber nailed to the 2x4"
cleats upon each side. This door is beveled upon all
four sides ; and when drawn tight with the bolt and
cross-bar, with strips of tar paper around same, the
joint cannot but be air-tight. Care should be used
to make the doors so that they fit perfectly, as other-

FIG. 13.— Sectional view of two styles of silo doors.

PRACTICAL SILO CONSTRUCTION . 57

wise the silo cannot be absolutely air-tight; and
unless so the results will not give satisfaction.

The view of door shown in Fig. 14 illustrates the
cross-bar or 2x4" strip, which is cut 3' long and
bolted to the center of door. This strip rests against
the walls of silo on each side of the door-openin'g.
Thus, by tightening the nut on the bolt, the door is
drawn closely into the frame or opening for same.

The dotted lines in Fig. 14 show how the rein-
forcement should be placed at the point where each
door-opening will come in the silo wall. Two I"
rods are used upon each side of the opening, and
these are placed so that they are within 1J " of the
surface of concrete around the door-frame. The
pressure exerted against the silo wall at this point,
by drawing the doors into position, makes this pre-
caution of ample reinforcing an important one for
the builder who desires durability in construction,
even in monolithic silos with heavy walls. This re-
inforcement is necessary where plastered silos are
constructed, as the thickness of wall is not enough
to withstand the pressure exerted by drawing the
doors into position with the bolt, unless strongly
reinforced.

A continuous door for the silo is shown in the
illustration at Fig. 15. The forms are built to mold
this opening of the desired width, which is usually
the same upon the inside as the width of the silo
door. The thickness of these wing walls is best
made the same as the walls of silo, which will avoid

;p

!

•^"»

I f

1 |

-

—

-

-

-

L L I.

1 1

1 1
1 1

1 1

1 1
1 1
1 1

, !

(

S>

; ;

i i

1 1
1 1

1 1

i ,

|i

• i
i •
i '

. 1J.

I*--:

t i
1 t
1 I

t i

' i
1 t

FIG. 14. — Silo door and reinforcement for opening.

FIG. 15.— Continuous door in concrete silo.

60 PRACTICAL SILO CONSTRUCTION

having a separate form to mold same. The opening
is closed by using short lengths of tongued and
grooved planks, supplemented with a thickness of
tar paper behind same. Two thicknesses of these
planks are employed, one at the outside opening of
the door, with the other at the opening upon the
inside of silo. The latter depends upon the pressure
of silage to hold them in place and are placed as
the silo is filled.

The outside planks are held in place by 2x4"
strips bolted to the concrete walls, the bolts for same
being imbedded in the concrete as the material is
placed in form.

SILO HOOFS

A successful type of silo roof, using concrete as
the covering material, is shown at Fig. 16. The
rafters are cut to give the pitch desired, and the
roof framed so that a dormer-window or opening is
placed upon the side of silo from which it will be
filled. The rafters are securely fastened to the wall
by bolts imbedded into the concrete of the last
course. The § " rods used as vertical reinforcement
can also be permitted to extend above the last course
of concrete and then fitted with threads and a nut so
as to bolt the rafter at the foot, cut securely to the wall
of silo. The space between rafters is now filled with
concrete, flush to the top edge of rafters, and over
the top of rafters wire lath, or expanded metal lath,
is nailed. This is treated to a plaster coat of con-

FIG. 16. — Details of constructing concrete silo roof.

62 PRACTICAL SILO CONSTRUCTION

crete, pressing it well against the laih to press
through and form a secure key. This should not be
less than l|"in thickness, and is best at about 2" or
2J ". The rafters must be spaced close enough so
that the metal lath will not sink or bend under the
weight of the concrete placed, or they may be rein-
forced by heavy wires stapled to the rafters every
6" apart around the roof for the first 3' from the
eaves upward.

Before the plaster coating is applied, a thin wood
strip may be nailed to the butt ends of the rafters as
a fascia or finishing strip to the roof. This must be
thin, so as to bend easily to the circle. In placing the
concrete plaster, this strip will be of value in getting
the eaves or edge of the roof even and symmetrical.
The concrete for the roof will give the best satis-
faction when made in the proportions of 1:3, using
sharp, well-graded sand.

ORNAMENTAL ROOF OR WALL FOR SILO

At Fig. 17 is shown an ornamental wall for the
silo that extends above the top of the roof. This is
in the form of a parapet, with embrasures and
merlons molded to suit the wishes of the builder.
The diameter of the parapet is 4 inches more than
the diameter of the silo. This requires a 2 " strip
to be placed at the bottom of mold for parapet, as
shown in illustration (Fig. 18). The inside mold for
this part of the wall is 4 " more in diameter than the
silo, thus molding a 2" ledge entirely around the

FIG. 17. —Ornamental roof for concrete silo,

FIG. 18. — Details of constructing ornamental roof to silo.

PRACTICAL SILO CONSTRUCTION 65

inside of the silo for the placing of rafters for the
roof. This ledge is placed so that it will be even
with the embrasures entirely around the parapet,
thus enabling the water to be easily carried off from
the roof.

The concrete is filled into mold up to the point
where the ledge is placed, then the wood forms for
embrasures are set inside the mold at the desired
distances apart, and the concrete tamped around
same to the top. These wood forms are constructed
of three short boards, with the center one, or cross-
piece, bored to supply a hold for removing the form
from the concrete. The construction of forms is
shown at Fig. 18, with the method of placing and
filling the form with the concrete.

INDEX

PAGE

Adjusting forms for various sizes of silos 31

Adjusting forms for thickness of walls 32

Advantages of the concrete silo over other types 14

Air-chamber in plaster silo 41

Amount of silage fed daily 17

Assembling silo form 26-29

Automatic clamp applied to silo forms 35-37

Bending steel centering 30

Blocks for silo construction 41-45

Breaking joints in laying silo blocks 47-49

Brush coat of neat cement, value of 15

Building silo forms 26-28

Clamps used on silo forms 25-36

Concrete for plastered silos 50

Concrete for silo construction 49

Construction of silo block molds 43-44

Continuous door opening:

block silos 47-48

monolithic silos 59-60

Cores for silo block molds 42-43

Doors for silos :

block silos 46ni7

construction 55-57

continuous 57-60

monolithic silos 55-60

plaster silos 40

reinforcing 57-58

size of 55

Dry-firing, cause of 19

67

68 INDEX

PAGE

Ensilage defined 14

Fastening sections of mold together 31

Floor of silo, how placed 19

Footing course, size of 20

Foundation of silo :

concrete for same 22

with floor at ground-level 20-21

with floor below ground-level 23-24

Freezing of silage, how prevented 16

Groove molded in block for reinforcement 43

History of the silo 13

Horizontal reinforcement or "hoops" 53

Laying silo blocks 45-46

Location of silo 19

Metal centering for silo construction 36-37

Method of raising forms 32-33

Mold for silo blocks 41-42

Molding ornamental roof to silo 62-65

Molding silo blocks 45

Monolithic silo walls :

with continuous air-chamber 37-41

without air-chamber 23

Ornamental roof for silos 62-65

Plaster silos, how built 38-39

Proportions of the silo 18

Rafters, how fastened to the silo walls 60

Reinforcement of silos 50-54

Reinforcement placed in silo blocks 45

Requisites of a successful silo 14-15

Roof for silos :

monolithic 60-61

ornamental 62-63

reinforcing. . 62

INDEX 69

PAGB

Sheet metal used as centering 25-26

Side pressure exerted by silage. 54

Size of silo to erect 17-18

Tables :

capacity of silo per foot of height 18

footing courses for silos 20

horizontal reinforcement of silos 53

steel sheets and clamps required 80

vertical reinforcement for silos 52

Tackle to raise forms 33-34

Thickness of wall in plaster silo 40

Tying reinforcement with wire 54

Vertical reinforcement 52

Vertical or plumb line, how assured 35

Waterproofing the silo 15-16

Weight of a cubic foot of silage 17

Weight of steel centering 28

Wet mixture, advantages of 50

Wire lath used in plaster silo 40

Wood clamp for silo forms 25-27

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