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Full text of "Description and instructions for care and operation of firing magnetos, types GA and MA"

GIFT OF 




J 




No. 1814 



DESCRIPTION AND INSTRUCTIONS 
FOR CARE AND OPERATION 



OF 



FIRING MAGNETOS 

TYPES GA AND MA 



(TWO PLATES) 



MARCH 10, 1917 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1917 



No. 1814 



DESCRIPTION AND INSTRUCTIONS 
FOR CARE AND OPERATION 

OF 

FIRING MAGNETOS 

TYPES GA AND MA 



(TWO PLATES) 



MARCH 10, 1917 




WASHINGTON 

GOVERNMENT PRINTING OFFICE 

1917 



c. 



Wab Department, 
Office of the Chief of Ordnance, 

Washington, March 10, 1917* 
Tliia manual ia published for the information and government of the Regular Army 
and National Guard of the United States. 
By order of the Secretary of War: 

William Crozier, 
Brigadier General, Chief of Ordnance. 
10067—17 C3 > 



365263 



Digitized by the Internet Archive 

in 2007 with funding from 

IVIicrosoft Corporation 



http://www.archive.org/details/careoperationOOunitrich 



DESCRIPTION AND INSTRUCTIONS FOR THE CARE AND 
OPERATION OF FIRING MAGNETOS. 



1 . The firing magnetos described below have been developed to 
replace the firing pistol and battery used on seacoast gun carriages 
and the D. C. magneto used for firing mortars. 

MAGNETO TYPE GA, FOR GUNS. 

(Plate I.) 

2. For gun firing, type GA'is used. This magneto is designed for 
firing one primer only, and is issued for all guns using separate 
ammunition. 

3. The magnetos are numbered serially, the first 100 having a base 
differing slightly from those of higher number. Numbers 1 to 100 
have two threaded lugs on the base through which the old-style 
firing cable with spiral armor passes. By means of a gasket, nut, and 
sleeve, the cable is made fast to the base. 

4. Numbers 101 and following have a single entrance provided in 
the base for the twin conductor leaded and armored firing cable. 

5. The principal parts of this magneto are: Case with base, firing 
lever, lever catch, lever spring, spring plunger and spring lever, 
lever shaft, gear segment, clutch-shaft pinion, clutch shaft, clutch- 
shaft bracket, clutch and spring, clutch-shaft gear, armature-shaft 
pinion, and magneto proper. The parts are named approximately 
in their order in the train from lever to magneto. 

6. The firing magneto, complete, weighs 33 pounds. 

7. The case is of bronze, and protects the interior from dust and 
excessive moisture. By means of a lug at the rear it is securely 
attached to the bracket provided on the sight standard. 

8. The firing lever is heavily constructed to resist bending under 
excessive strain. It is held in the locked position by a catch, and 
when the lever is gripped preparatory to firing the catch is automati- 
cally released. The lever is returned to the locked position by the 
lever spring, assisted by the weight of the lever itself. It has been 
found that it is not necessary to raise the lever violently, as even a 
small and slow movement will fire a primer. The gear ratio is such 
that one complete revolution of the lever would give 48 revolutions 
of the armature. As the lever can be easily moved at the rate of one 

(5) 



T « c^ ^ c 



6 



turn in a second, it is seen that very high armature speeds may be 
obtained. When the lever is raised, the gear segment on the far end 
of the lever shaft turns the combination pinion and clutch. The 
latter, through the clutch sleeve, turns the clutch shaft and the large 
gear on the other end of this shaft meshing with the pinion on the 
armature shaft. The pinion on the clutch shaft is extended through 
the clutch shaft bearing and has on its inner end ratchet teeth. 
These are normally in mesh with the teeth on the clutch sleeve. The 
sleeve slides free on a flat section of the shaft, but must turn with it, 
and is held in mesh with the pinion by a spring. Thus, when the 
lever is raised, the armature is revolved, and when the lever stops the 
clutch teeth slide over each other, the spring allowing the sleeve to 
back off from engagement with the pinion clutch. The armature is 
thus allowed to revolve until its momentum is lost and sustain the 
current, 

9. This magneto will deliver on open circuit about 45 volts at 
2,000 r. p. m. Through an external resistance of 1 to 3 ohms, it 
will, at 2,000 r. p. m., generate about 0.8 ampere at 1 volt pressure. 
Small external resistances do not greatly affect the output and a 
primer can be fired with as much as 60 ohms resistance in the circuit. 
The armature and brush resistance is about 3 ohms. 

10. The average current being about 0.8 ampere it will be ample 
to fire one primer. However, the capacity is in general not sufficient 
to fire in parallel, since about 0.4 ampere or more is necessary to fire 
a primer. As the resistance of the firing circuit is less than 1 ohm it is 
seen that while a large number of primers might be fired in series, 
only two could be fired in parallel, under favorable circumstances. 
The magneto should not therefore be expected to fire more than one 
primer except in series. 

11. The magneto proper is made by the Sumter Telephone Manu- 
facturing Co., and is their type JR. The armature is wound with 
530 to 540 turns of No. 21 wire (B. & S.) 

MAGNETO TYPE MA, FOR MORTARS. 
(Plate II.) 

12. This magneto is quite similar in principle and construction to 
the type GA, the capacity being considerably greater, however. It 
is designed to fire four primers in parallel and for this purpose the 
current output must be at least 1.5 to 2.5 amperes. In the branches 
of a divided circuit the greater portion of the current flows in the 
branches of least resistance. It is therefore desirable to have as 
great an output of current as practicable in excess of the necessary 
requirement in order to insure that all branches have the necessary 
current. It is also very important that the resistance in all branches 
be kept as nearly the same as possible. 



13. The characteristics of this magneto are as follows: The voltage 
on open circuit is about 50 at 4,000 r. p. m. Through an external 
resistance of 2 ohms at 4,000 r. p. m. the output is about 8 amperes 
at 16 volts, and at 1,000 r. p. m., through the same external resistance, 
the output is about 4.5 amperes at 9 volts. The armature and brush 
resistance is 0.4 ohm. 

14. The gear ratios are such that one turn of the firing lever causes 
30 turns of the armature. 

15. It is expected that four primers will fire simultaneously with- 
out great effort. In experimental firing, the primers have been found 
to explode upon a very small and relatively slow movement of the 
handle. When difficulty is experienced in firing all primers simul- 
taneously, examination should be made to ascertain whether the 
branches of the divided circuit have approximately equal resistances. 

16. The magneto, complete, weighs about 86 pounds. 

17. The magneto proper is made by the Sumter Telephone Manu- 
facturing Co. and is designated by them as type AGD. 

18. A wall bracket is provided in or near each mortar pit for 
mounting the magneto, which is there attached to the engineer cables. 

CARE OF MAGNETOS. ^ 

19. The construction of the magneto complete is very simple, and 
but little attention is required to keep it in good condition. All nuts 
are of the crown type held by a split pin to avoid unscrewing by 
vibration. The studs for the six nuts at the base are pinned in 
position. 

20. When the magneto is not in use for extended periods it should 
be removed from the carriage, mount, or emplacement, if practicable, 
advantage being taken of this opportunity to examine the interior 
before storing. 

21. The only attention required is examination of the interior 
approximately twice during the year to prevent starting of rust and 
to allow oiling of gears and bearings. Openings in the case for this 
purpose have been omitted for the sake of greater protection. To 
examine the interior, remove the nuts at the comers and sides of the 
base. The base, with magneto which is held to it by the remainiag 
studs, can then be removed. There may be slight binding of the base 
on the studs so that it wiU be necessary to insert a thin tool between 
the base and the case in order to separate them. 

22. The armature-shaft bearings are provided with grease pockets 
and these should be kept packed with waste soaked with light engine 
oil. 

23. If difficulty is experienced in firing primers, it will probably be 
found that there is some irregularity in the firing circuit or magneto, 
and an examination should be made, rather than an attempt to over- 



come the difficulty by violent raising of the- lever. The lever should 
be raised with a moderately quick action aifd under proper conditions 
a relatively slow movement will fire the primer. The magnets should 
not be removed from the magneto frame unless absolutely necessary. 
To do so weakens the field and decreases the voltage. When the 
magnets are necessarily removed, they should be placed with the ends 
on pole pieces. 



COVER FOR^ FIRING MAGNETO. 

24. A cotton duck cover is provided with each magneto for pro- 
tection against the weather when not in use. 

TESTING LAMP. 

25. There is provided a testing lamp for testing out the gun-firing 
circuit and magneto. It consists of a low-voltage incandescent lamp 
attached to a dummy primer. When this dummy is inserted in the 
vent, the firing circuit is closed in the usual manner. Upon operating 
the magneto the lamp will glow. If the circuit is in good condition 
the lamp will glow brightly, but the capacity is such that a current 
which will even produce a duU-red glow will fire a primer. 

List of parts of firing magneto, their piece marks, number, and location. 

TYPE GA. 



Piece Num- 
mark. i ber. 



P67Q. 
P66G. 
P67P. 
P67L. 
P67S. 
P67T. 
P67X. 
P61H. 
P67A. 
P67J.. 
P67K. 
P67C. 
P67F. 
P66K. 
P80E. 
P66H. 
P80F. 
P66C. 
P66E. 
P80D. 

P66N. 
P61F. 
P67N. 
P67G. 
P66F. 
P67H. 
P67E. 



P66D. 
P67Y. 



P67B. 
P61G. 



Name of part. 



Base (for use with flexible conduit) . 
Base (for use with armored cable) . . 

Bushings 

Case 



Clutch 

Clutch sleeve 

Clutch-shaft bracket . 
Gaskets, coupling. . . 

Gear 

Intermediate shaft. . 
Key. 



Location. 



...do 

Key, Woodruff No. 1 

Lever 

Lever catch 

Lever-catch pin 

Lever-catch spring 

Lever-return spring 

Lever shaft , 

Lever stop 

Magneto, Sumter JR, or equal . 

Nameplate 

Nuts, coupling 

Nuts, crown 

do 

do 

do 

Pinion 

Pins, dowel 

Pins 

do. 
Plunger pin . 
Rivets, countersunk. 
Screws, filister head. 

do. 
Segment , 
Sleeves, conduit. 
Split pin. 

do. 



Bottom of case. 

Do. 
For base P67Q. 
Slips on magneto bracket. 
On intermediate shaft. 

Do. 
Secured to armature yoke. 
On conduit sleeves. 
On intermediate shaft. 
In clutch-shaft bracket. 
Intermediate shaft. 
Lever shaft. 
Armature shaft. 
On end of lever shaft. 
On lever. 

Lever catch to lever. 
Riveted to lever catch. 
Around spring plunger. 
In bearings in case. 
Riveted to lever catoh. 
Secured to base of case. 
On front of case. 
Screw on bosses on base. 
For studs P67M;. 

On clutch end of intermediate shaft. 
On end of lever shaft. 
On gear end of intermediate shaft. 
On end of armature shaft. 
In bottom of case for base. 
For studs P67M;. 
For studs P66P. 

Connects spring plunger and spring lever. 
For fastening spring to lever catch. 
For fastening clutch shaft bracket. 
For nameplate. 
On intermediate shaft. 
In coupling nuts. 
For plunger pin. 
For lever-catch pin. 



List of parts of firing magneto, their piece marks, number, and location — Continued. 

TYPE GA— Continued. 



Piece 
mark. 


Num- 
ber. 


Name of part. 


Location. 


P61G 




Split pin .. . 


For nut P67H. 








For nut P67G. 


P67U 


Spring clutch .... 


On intermediate shaft 


P66A 


Spring lever . 


Do. 


P66B . 


Soring nlunger 


Between spring lever and lug on case. 
Fasten base to case. 


P67M 


Studs 


P66P 


..do . .. . 


To hold magneto to base. 
On lever-catch pin. 
On intermediate shaft. 


P66J 


Washer 


P67W.... 


Washer, clutch 


P67D 


Washer 


Do. 









TYPE MA. 



P74B 


1 

1 

4 
1 


Base .. . 


Bolted to bottom of case. 


P74A 


Case 


Slips on magneto bracket. 
On intermediate shaft. 


P76R 


Clutch 


P76K 


Clutch sleeve 


Do. 


P76L 


Clutch spring > 


Do. 


T97P 


Conductor terminal 


Attaches to terminal end bracket. 


T97Q 

P76M 


do 

Dowel pins 

Intermediate gear 


Do. 
In bottom of case for base. 
On intermediate shaft. 


P76F 


Intermediate shaft 


In terminal end and pinion end bracket 


P75A 


Lever 


bearings. 
On lever shaft. 


P75E 


Lever catch 


On lever. 


P75G 


Lever-catch pin 


Lever catch to lever. 


P75F 


Lever-catch spring . 


Riveted to lever catch. 


P75B 


Lever shaft 


In bearings in case. 


P75P 


Lever stop ... 


Riveted to lever catch. 


P73E 

P73C 


Magneto, Sumter AGD, or equal 

Magneto cable 


Bolted to base. 
From plug to terminals. 
Connects to plug box. 
On armature shaft. 
Do. 


P73D 


Magneto-cable plug 


P76N 

P76P 


Magneto pinion 

Magneto-pinion key 


P73A 

P74G 

P74E 

P76G 

P75C 

P76H 

P73F 

P76E 


Nameplate 

Nuts, crown 

do 

do 

do... 

do 

do 

Pins 

Pinion end bracket 


On front of case. 

For studs P74C. 

For studs P74D. 

For intermediate shaft. 

For lever shaft. 

For intermediate shaft. 

For armature shaft. 

Secure studs f P74D) in case. 

Secured to pinion end of magneto. 


P73B 


Rivets 

Screws, fllister head. 


For fastening spring to lever catch. 
Fasten nameplate to case. 


P76D 

P76C 

P76B 

P76B 


do 

do 

do 

do 


Clamps end of terminal end bracket. 
Conductor terminal to terminal end bracket. 
Pinion end bracket to magneto. 
Terminal end bracket to magneto. 


P75L 


Segment 


On intermediate shaft. 


P75D..... 


Segment spring ... . 


Between spring hanger and spring stud. 
In lever shaft. 


P75M 


Segment key 




Snlitpta.. . , 


For lever-catch pin. 




do 


For spring hanger. 
On segment. 


P75N 


Spring hanger 


P74P 


Spring stud 


Screwed and riveted to inside of case. 


P74C 


studs. : . . ::.:.... 


Fasten magneto to base. 


P74D 


do 


Connect base to case. 


P76A 


Terminal end bracket 


Secured to terminal end of magneto. 


T96EA... 


Terminal tube, complete 


Screwed into base. 


P75H 


Washer 


For lever-catch pin. 


P75K 


do 


For spring hanger. 


P76Q 


do 


For intermediate shaft. 









War Department, 

Office of the Chief of Ordnance, 

Washington, March 10, 1917. 



Form No. 1814. 
Ed. Aug. 27-17—500. 



NOU/SOd SIHl Nl SI d3A31 N3HN^ 
a39\/0N3 Xnnj HJ.33J. HOimO HJ.IM IVlNOZiyOH 39 01 3ynivu/ijv- 




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STAMPED Je^W^®^ "Ara 

AN INITIAL FINS ni. o. 

OVE^OUE. "° *'°° ON THE SE^V^EWTr^J? 




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YC 6437 



Ca^ord Bros. 

Makers 
Syracuse, N. Y. 

pit; JAM. 21 .\m 



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UNIVERSrrY OF CAUFORNIA UBRARY