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Handbook of the
Incendiary Drop Bombs
LIBRARY THE NATIOiIAL ARC!{I\CJ
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WAR DEPARTMEN'f. Document No. ?7?. Ofi,ce
of the Adiut.ant
Gen'eral.
WAR DEPARTMENT, Wessrxero*, March 25, 7918. The following pamphlet entitled. "Ifandbook of the Incendiary Drop Bombs, Mark I and fI," is published for the informatlon and ggidance of all concerned. [062.1 A. c. O.]
Bv
onnon oF TEE Sncnnrenr oF'Wen,
PEYTON C. MARCH,
Major General, Acti,ng Chi,eI of Staff. Ornrcrer,:
H. P. MoCAIN, The Ad,jutant General.
TABLE OF CONTENTS
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Chart II.-Nomenclature
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Plate L-Assembly drawing-Incendiary Drop Bombs, ....... 5 l\Iark I ... 6 Chart I.-Nomenclature 6 ....... (a) Thebotty. 8, (b) The firing mechanism (c) The explosive and incendiary materials 10 IncendiaryDropBomb,MarkI..... :..'...... 10 ....1........ (a) The botly . (b) . .. firing mechanism The . .. . .. 16 (c) The explosive and incendiary materials .-.- t7 bomb the of Operation . . 18 Plate Il.-Auxiliary nose flring mechanism mechanism the of Operation Plate III.-Assembly drawinS-Incendiary Drop Bomb, .......2L MarkII ... (a)ThebodY. (b) The flring mechanism Incendiary DroP Bomb, Mark II . . . (a) The bodY . (b) The firing mechanism (c) Incendiary and explosive materials. ;..." .'.... Operationofthebomb
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&'pnoouceo ar rHE NATIoNAL ARoHIvES
Nomenelatur.-r'""fr1T i'op norot, Mark I. SYMBoL qaaNTtTY
(a)
Front
The Bods
body. ...steer . ....
Nose nuing
prue'. '
C
I
stops.
D
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Front
.
LOCATION AND PONPOSE
MATENIAL
NAME
plate.
Plate sealing
material.
"steer ..sheet
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steer..
nring mechan-
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Locate and
...Soldiied_in front bodv'(A) ag.aiust stois
...Sheetsteel.
(C).
Separates nose powder .charge
(AQ) from incendiary charge (AS); supports firing tube guide (F). ....Soldered on front plate (D). Prevents infrom entering nose powder
disk....Tin
fi:*f,:{.fluid
front pla.te (-DJ, Locates and tubeguide....steel ....;....Soldered on firins tube (G) and loading ilB|i:f)' . .'Extdnds from diaplragT".$) to firing tube. .Steel. Firing tube. . guide (F). Guides- bullet and flash of
Firing
diseharge.
Fitilg
H
tube
disk.
K
sealing Tin. .
Loading tube.
.
Tin.
,
,
M
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.
N
Connecting ring. . . . .Steel. Rear body . . . . Sheet steel. Safety wire guide. . . . Sheet
Diaphragm " R
Re.arcap...
"sheet
..
.
steel.
T
Filling
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Filing
hore disk. . . . .
. .Sheet
Lead.
tube ineendiary
end of firing tube (G). Facilitates assembly of front and re&r body after
Rear of bomb body-contains incendiary material (AS) rear powder chargi (AR) and firins mechanism. . . . Riveted oi rear lody (M). in line with stabilizer (V). Supports loop of safety .
su*isteer.. ,.
of
..Connecti front body (A) to rear body (M).
steel"
steel. hole plate'. . . .Sheet steel.
Renr filling plug.
of firing
loading.
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(G).
Prevents entranee fluid into firinc tube (G).
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Soldered over forward end
it,ljfrand
steadies bomb
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drrring
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Carries stabili",ers (V) end is traversed by release pin (AH). . ..Screws into filling hole plate (T). Permits insertion of rear powder charge (AR). i..Soldered in rear body (M). Receives rear
"r*"fit 'hole.
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AT THE NATIoNAL ARcHIvES
DECLASSIFIED
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Stabilizer screws and Steel nuts.
AB
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AC
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AD
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AE
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Striker tube washer.
.
Striker
AF
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AG
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striker
Steel
.Steel
spring
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.
steer
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Fits in
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under striker tube (AD). Holds
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AH
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AK
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AL
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AM
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AP
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Release pin seat.
spring
Steel.
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tridge (AT) in place. . ..Slides in striker tube (AD).IOn contact, fires cartridge (AT).
.
INCENDIARY DROP BOMB, MARK I.
The Incendiary Drop Bomb, Mark I, is intended fo.r use against light structures, ammunition dumps, grain fields, or like objectives where only a low clegree of igniting power is required. It is of the so-called "scatter" type, clue to the action of the exploding charge, which capts out the incendiary
material within a radius of from 15 to 30 yards from thf point of contact In size and shape the bomb is similar to the Mark III High Capacity Bomb. It has a ntaximum diameter of 6.10 inches and a length of 36.64 inches and weighs about 40 pounds. It consists of three rnajor parts: (a) The body. (b) The firing mechanism. (c) The explosive and incendiary'materials.
(a) The Body. The body consists of the ?ront Bod.u (A), the Nose Fil,ting
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PIug (B), the Btops (C), the Front Plate (D), the Plate Bealing Disk (E), the Fi,r'i,ng Tu,be Gu'ide (X'), the Firing Tube (G), the Piring Tube Seaii'ng Disk (H), the Load,i,ng Tube (K), the Connecti,ng Ring (L), the Rear Body (M), t]rg Safetg Wire Guid,e (N), the Diaph.ragm (Q), the Rear Cop (R), tt,.e Rear Filli,ng Pttr'g (S), the Filli'ng Hole Plate (T), the Iitli,ng Hole Di'sk (U), the Stabi'li'zers (V), the Stabili,zer Lugs (W), and the Btabil'i,zer Screws and, Nuts (X). Tbe Front Bod,y (A), is a hollow steel paraboloicl 6.10 inches in diameter at the base and 12.2 inches high, with walls 3/16 ot an inch thick. In the rounded nose a hole has been drilled ancl tapped to receive the .Nose Filli'ng Plug (B), which is a half-itich standard pipe plug. Through this hole the nose charge of powder is inserted; it is also designed to receive an auxiliary nose-firing mechanism, when this ip found desirable. X''or a distance of 7/z of an inch, thq rear end of the front body (A) is threaded on the inside to receive the connecting ring (L). Three sheet steel Btops (C) , 7/z of an inch square and $ of an inch tbick, are silot welded to the inside of the front bocly
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(A), at a point 8.3 inches from the'base, to locate and support the front plate'(D). The Front Plate (D) is a circular piece of sheet steel 4.2 inches in diameter and t/J,6 ot an inch ilrick, with the outer etlge bent uprvard for 12 0f an inch to fit into the front body (A) against the stops (C) where it is soldered. in place. A hole /a of an inch in diameter is bored through its center and sealed by means of the plate seating Dr;sk (E), a circular
piece of tin .01 of an inch thick. and. Ll2 inches in diameter, which is soldered in place. . The Firi,ng Tube Gui(te (X') is a steel cylinder 1/2 inches in diameter and /a oL an inch long. x''or a distance of la of an inch from the front end it is drilled to a rliameter of y* of an inch to receive the firing tube (G). The bore is increased to I-.05 inches for a distance of. E/L6 of an inch from the rear end to receive the loading tube (K). The guide is soldered to the plate sealing disk (E) with the bore.in line with the hole in the front plate (D). The Eiring Tube (G) is a steel cylincler 29s7, irLeh.es long with an insitle diameter of 9/16 of an inch ancl an outside diameter of- Ll/16 of an inch. The front end is sealed by means of the tin Eiring Tu,be Sealing Disk (H), 7/8 of an inch in diameter and .01 of an inch thick, peened. over and. soldered in place, antl is inserted in the flring tube guide (X'). The rear end is inserted in the hole in the ctiaphraCm (e), and. over the front end of the cartridge chamber (AA), and brazed in
position.
Th.e Loading Tube (K') is a tin cylinder 6.87b inches long and 1 inch in diameter, the forrvard end of which is inserted in the recess iu the flring tube guicle (F). It serves to facilitate the flnal assernby of the front and rear bodies after these have been loaded with the incendiary charge (AS). The Gonnecting Ring (L) is a steel cylinder 6.088 inches in diameter and 1r/s inehes long. The front end is turned down and threaded to a diameter of 5.85 inches to fit itrto the front body (A). Around the center of the rear portion is cut a rounded channel 5/32 ot an inch wide and 1/16 of an inch deep to provide a binding surface wherein the rear body (M) is crirnped and. soldered to the connecting ring (L). The Rear Bocly (M) is made of sheet steel 1/32 of an inch thick. It is in the shape of a truncatecl cone with a total
inches. The base of the cune is 6.038 inches in diameter to fit over the shoulder of the eonnecting rins (L). Four Stabilizer Lugs (W) are riveted and soldered to the rear body (NI) at a point 10.64 inches from the rear end to serve as a means of attaching the stabilizers (V) and rear cap (R). The lugs are sheet steel rectangles bent at the center, thus forming two sections Yz of at inch square perpendicular to each other, which receive the rivets and stabilizer serews (X). Th.e Safetg Wire Guide (N) is a sheet steel rectangle with rounded corners,.92x1.31 inches; it has a raised portion tA of an inch high antt 3/L6 ot an inch v'ide running lengthwise through its center to form a channel for the passage of the safety wire (AP). The bottom is curved to flt the rear body (M) to which it is riveted by means of four tubuiar rivets, at a point 13/e inches from the nose of the bomb. The raised. portion fits into the frame of the release mechanism and serves to steady the bomb tluring flight. In the center of the upper' surface a hole is punched to permit the passage of the safety wire in such a manner that the upturned edges act as a support for the loop of the safety wire (AP). T];g Di,aphragm (Q) is a sheet steel tiisk l/16 of an inch thick with the outer edge turned down f.or 12 of an inch to conform to the shape of the rear body (M), to which it is soldered at a point 15.84 inches from the front end. A hole is punched in its center and a flange is turned up for a distance of a/+ of an inch, leaving a hole 11/16 of an inch in diameter to receive the base of the firing tube (G) to which it is solclerecl. The rear portion of the body tapers down to a diameter of. 2.20 inches to receive the cartriclge chamber (AA). At a point 2y2 inclaes from the reat end, ancl midway between the rear stabilizer lugs, a filling hole is driiled in the shell to receive the filling plug (S). Tlrg Rear Fi,Ui,ng Plug (S) is a steel cylinder sl of an inch in diameter and. 5/32 ot an inch long, threacled to flt into the fllling hole plate (T). A slot 3/32.of an inch wide and 3/32 of an inch deep is cut across the upper surface to provide length of
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a grip lor a screw driver. T)ae Ei,lling Hole Plate (T) is a sheet steel cylinder /s of an inch in diameter and a/+ of an inch iong. A recess 5/32 of an inch dedp is cut in one surface and tapped to receive 72
tlre filling plug (S). A hole. s/s of an inch in diameter is drilled through tire center of the filling hole plate (T) to permit the insertion of the charge in the rear powder chamber. The filling hole plate (T) is soldered to the inner surface of the rear body (M) directly over the filling hole, ancl the learl Fdllitt,g Hole Disk (U),
a/z of an inch in diameter by t/32 of. an inch thick, is used as a washer under the plug (S) to seal the filling hole. TIr.e Rear CaIt (R) is a hollow steel cone 2.2 inches in diameter ancl 4.4 inches high, with walls t/t6 of- an inch thick. At a clistance of 2/a inchei from the base, the walls of the cone are flattened in two places exactly opposite each other. These surfaces are traversed by a hole Y+ of an inch in diameter to receive the safety pin. on liue with these holes, a slot .2 of an inch deeB is cut in the base of the cap to receive the steel locating pin (AB) ' The Stabitizers (V) are irregularly shapetl steel quadof 16.27 rangles .05 of an inch thick, with 4 maxirnum length 'At a point inches and a maximum width of 3.19 inches. 3.35 inches from the rear end is a lug 5/t6 ot an inch wide a,nd 1.3? inches long, by means of which the stabilizer is weldecl to the rear cap. Ong inch from the front end an elliptical hole is drilled Y+, of an inch lrom the innner edge to receive the No. 6-32 Stabi,lizer Screu and, Ntct (X) which fastens.the, stabilizer to the stabilizer lug' (b) The Firing Mechanism. The firing mechanisrn consists of the cartri,d,ge chamber (AA) the'Locating Pin (AB), the Flash, Hote (AC), the Striker Tube (AD), the Striker Tube Washer (AE), the Striker (AF), the Stri,ker Sttring (AG), the Release Pi'n (AH) , ttre Release Pin S?trdng (AK), the Release Pin Spring Seot (AL) ,l]ne Release Pin Washer (AM), the Goskets (AN), and the SaletY Wire (AP). The cartrirtge chamber (AA), is an irregularly shaped steel cylind.er 5!a inches long and 2als inches at its largest diameter. For a distance of 1 1/16 inches from the front enQ it is turned to a diameter of .560 of an inch for insertion in the firing tube (G). At a point 1/L6 ot an inch from the rear end of this section, t]ne Flash Hole (,LC) is tlrilled into the central recess for the purpose of comurunicating the flash :
13
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of the cartridge to the rear. powder charge (AR). Frorn a shoulder L 1/76 inches from the front end and tL/I6 of an
in d.iameter, the cartridge chamber (AA) tapers outward to its maximum diameter at a poiuL 4Ys inches from the same end. From this point it tapers down at a l3-degree angle for a distance of 6/s of an inch to a diameter of 2.138 inches. A concave recess is turnetl in the center of the inch
surface Just described, 5/32 of an inch s'ide and, t/L6 of an inch deep, to provitle a binding surface into which the base of the rear body (M) is peened at the time of assembly. The extreme end of the cartridge cha,nber (AA) is offset and tapers from a diameter of 2.075 inches at a 13-degree angle for a distance of Yz of an inch. About .2 of an inch from the upper shoulder a hole is drillerl with its axis perpendicular to this surfaee to receive the /s-inch steel Locat-
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ing Pin, which locates the rear cap. A recess is bored in the rear of the cartritlge chamber (AA) L 5/16 inches in diameter and 17i inches deep to receive the striker tube (AD). For a distauce of /a of an inch from the entl this recess is tapped to a diameter of LYs inches to fit the threadetl portion ot the striker tube (AD). A hole leatling from the recess to the front entl of the cartridge charnber is bored out to receive a 30-caliber service cartridge (AT). The Striker Tube (AD) is a brass cylinder 2 9/16 inches long with an outside diameter of I&/e inches and an inside diameter of 1 inch. The front end is turned down to a diameter of. LY+ inches for a distance of 1 inch to flt into. the recess in the cartridge chamber (AA). The central section is threaded for a distance of /a of. an in,:h to fit the threaded portion of the cartridge chamber (AA). The outer edge at the base is rounded off, while the inner shoulder at this point is cut away at a 45-degree angle to facilitate the iusertion of the striker (AF) Tt.e Stri.ker Tube Washer (AE) is a steel cylinder t t inches in diameter and t/a of an inch long, with a Y+ of an inch hole through its center. It is placed in the recess ln the cartridge chamber (AA), and the striker tube (AD) is screwed down over it. Its purpose is to Secure tbe cartridge
(AT) in
place.
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(AF) is an irregularly L4
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shaped steel cylinder
with a total length of }7/+.inches and a maximum diameter of .985 of an inch. The section of largest diameter is the central portion which is tYz inches lon€i. At the front'end lug 5/16 of an inch long and s/a of an inch ln diameter ', aprojects frorn the center, and acts as the rear bearing for the striker spring (AG). From the base of this lug a pin' , 1A of an inch in diameter at its base and tapering to a rounded. point, projects 3/16 of. an inch above the face of the
lugantl'servesasafirlngpin.Therearsectionofthe
striker (AF) is 1/2 inches longAnd !2 of an inch in diameter'
withaT/S2ot.aninchholedrilledV+ofaninchfromthe rear end to receive the release pin (AH)' TheStrikerS1lring(AG)ismadeotfourcoilsofsteel spring wire, approximately 3/64 of an inch thick' with an outsitle diameter of 15/16 of an inch ai one end, tapering down to 9/16 of an inch at the other. 'Ihe spring is Ts of' an inch long before compression' T]oeReteasePin(AH)isanirregularlyshapeclcoldrolled steel cylintler 3 5/32 lrrrehes long and' 7 /16 of an inch wide
atitslargestdiameter.Thissection.isL/|6ofaninch
long anrl seryes as the upper seat for the coiled' release Bin spring (AK). For a distance of LV+ inches the pin is turned down to a'diameter of 5/L6 ot an inch to flt into the spring (AK). The remaining sectiou is intended for insertion through the spring seat; it has a length ot' t 27 /32 inches' and distance of /3 of an a. diameter of 3/16 of an inch except for a inch from the'entt where it tapers to iBoint. A 3/32 of an inch hole is drilleit through the pin 19 /64 of an inch from the point to receiYe the safety wire' Tine R,el,ease Pin Spring (AK) consists of about 12 coils
of.0S2muslcwirewithaninsidediameterof.2|/6aof.an inch, and a normal length of about 2r/2 inches' T:ne spring Beat (AL) is a built-up cylintler
ot steel Ys ofaninchlongwithamaxlmurndlameterof.T/|6ofaninch' For a elistance of l+ of an inch frorn one end' it is turned r]owntoadiameterotS/16ofaninchtoserveasthelowerin bearlng for the spring (AK)' A hole t3/64 of an inch diameterlsdrilledthroughthespringseat(AL)torecelve the t release Pin (AH).(AN), soaked in paraffin' are placed on T*o felt baskets
thereleasepin(AH)torendertheboleslntherearcap .16
(R) waterproof. The gaskets (AN) are t/L6 of an lnch thic\ and 7 /L6 of an inch in diameter with a hole B /t6 ot t an ineh in diameter. ' ' The Release Pin Washer (AM) i's a steel cylinder 8/16 of an inch long and, 7 /L6 of an inch in tliameter with a bore
The Incend,iary Charge (AS) consists of a mass of cotton in a highy inflammable fluid, and pressed into the front and rear bod.y before these are assembled.. This material has a ver.y low flash point and will burn flercely for about 15 minutes. The Cartri,clge (AT) is a standard 30-caliber service cartrltlge. rvaste balls soaked
ot 13/64 of an inch, which is pJaced over the end of the release
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pin (AH) to serve as a bearing for the release Bin (AH), and a support for the safety wire (Ap). The sprinC (AK), the spring seat (AL), and a felt gasket (AN), are slipped over the end of the release pin (AH) ii the order given, and the pin (AH) is then inserted through the holes in the rear cap (R), and the hote in the striker (AF) which has'been placed insiile the rear cap (R).. Another felt gasket (AN) is then placed over the end of the release pin (AH), followed by the steel washer (AM). The end of the safety wire (Ap) is passed through the hole in the release pin (AH) and is ieated on the steel washer (AM). Ih.e SafetE Wire (AP) is a piece ot 1/BZ of an inch music wire with a loop /a of. an inch in diameter 22 inches from one encl; this end is passed through the safety wire guide (N) and extends through the release pin (AHy, the loop resting in the groove in the safety wire guide (N). The opposite enh of the wire is 16/a inches long below the loop and extends through the safety wire guide to the nose firing mechanism. When this device is uot used, the extra length of wire is cut off close to the loop. (c) The Explosive and Incendiary Materials. The expldsive and incendiary materials consist of the
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Pouder Charge (AQ), the Rear Powcler Charge (AR), the Incendiary Charge (AS), and the Cartrid,ge (AT). The Nose Powder Charge (AQ) consists of a quantity of black powder, which is inserted in the front powder chamber upon removal of the nose filling plug (B). The explosion drives the incendiary charge (AS) out of the rear of the
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bomb as: from a mortar, and, at the same time, ignites it. The Rear Powd,er Charge (AR), is composed, likewise, o[ black powcler which is inserted through rhe rear filling hole, '" Upon explosion it breaks open the rear of the bomb so as to pr6vide' for the wicle dispersion of the incendiary materials. It also serves to ignite the incentliary charge (AS). 16
Operation of the Bomb.
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Upon release of the bomb from the plane, the safety wire (AP) is withdrawn from the release pin (AH), which is thrown' off by the action of the release pin spring (AI(). The striker (AF ) is now free to move forward., except for
the restraining action of the stpiker spring (AG). Upon contact, inertia drives the striker (AF) forward, overcoming the force of the spring; the firing pin strikes the primer ot the cartridge (AT) and flres it. The bullet passes up the firing tube (G) and the flash of the discharge, following the path of the bullet, sets off the nose powder charge (Ae). The flash, at the same time, is cornmunicated to the rear powder charge (AR) through the flash hole (AC). The incendiary charge (AS) is thereupon blown out to a distance of from flfteen to thirty yards from the point of impact. .The radius of dispersion is, of course, depentlent upon the character of the structure or terrain at the point of impact, and the depth to which the bomb has penetraled.
Norn.-The exterior surfaces of the Mark I Incendiary Bomb are paintetl with an olive drab paint. A black band, 1 inch wide, is painted around. the body to indicate the center
of gravity; on this band are painted, in white, the designation of the bomb, the manufacturer's name, the lot number, the serial number, and the inspeetor's initials. At a point three inches from the tip, o' red, band,, 1 inch wide, is painted around the nose to further indicate the type of bomb. The bomb is shipped, with the powder charges in a separate tin can, held in the shipping container, to prevent any malfunction of the bomb due to saturation of the powder charge with the incendiary fluid. The powder is loadetl in the nose and rear polr'der chambers when the r-romb is made reatly for use. L7
Auxiliary Nose Firing Mechanism. .
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t,o cause explosion of the nose powder charge as soon as possible after contact with the target, and before any appreciable penetration has occurred. rts use results in the more rapid functionins of the bomb, and a wider dispersion of the in-
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The auxiliary nose firing r4echanisrn consists of : The Pri,mer Container, the primer, the BtriL;ing ptug, the .l/ose tr'iri,ng PLn, the Retease pin, tlne Retease pin Spring, the Spring Beof, the Coll,ar, the Shear Wire, and the Safetg Wire. The Primer contai'ner is a steel eylind.er, measuring 1 Lr/r6 inch'es in ldngth and .840 of an inch at the point ot largest diameter. A concave recess vz of an inch wide and B/82 ot an inch d.eep, at its central point, is turned 5/L6 of. an inch from the front end. The recess is flatted in two
the release Bin.
The rear end carries a
for a distance of hole.
n 2
places
'exactly opBoslte each othen, to provide a supporting surface for the spring seat and collar. a .204 of an inch hole is drilled through the center of ilrese two surfaces to receive s/b
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of an inch stantlard pipe thread nose flllling
of an inch to fit into the
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recess is bored in the front end of the primer container of an inch in diameter and L E/L6 inches long to receive f.he firing pin. Ir'rom this recess a hole .z2z of. an inch in diameter is drilled to the rear end. to receive the .22-caliber McAda.m primer. At a point g/L6 ot an inch from the front end, and perpendicular to the axis of the hole for the release pin, another hole 3/32 ot an inch in diameter is drilled.through .512
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. The Auxiliary Nose F iring Mechanism is a flring device inserted in the nose of the rncendiary Drop Bomb, Mark r,
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tbe Brimer contaiuer to receive the shear wire. The Primer is a .22-caliber McAdarn rifle grenade primer. The Nose Firin'g Pin is a cord rolled stdel cyrin der Lr/+ inches long and .4gG of an'inch in diameter. projecting frori tlre rear end is a pyramidal lug measuring 5/L6 ot an inch at the base antl 7/+ of an inch high, which is inteuded to strike the primer. The Striking plug, a steel disk Lyz inches in diameter and ye of an inch thick is riveted to the 19
flring pin by means of a lug 7 /32 ot an inch loug antl Y+ of an inch in diameter projecting from the front end of the pln. The Release Pitt, is a built-up cold rolled steel cylintler 3 5/32 inches long and 7 fLG ot an inch at its largest diameter. This section is t/L6 ot an inch wide and acts as the uppbr seat for the spring. The pin is turned down to a diameter ot 5/16 of an inch for a distance ot LY+ inches for insertion in tlre spring. The lower end of the pin ls made 3/t6 of an
inch in diameter for insertion through the holes in the
nose
firing pin and primer container, except for a distance of +b of an inch from the end, where it tapers to 4 point. A.3/32 of an incl.r hole is drilletl through the pin at a point L g5/64 inches from the lower shoulder to receive the release wlre. T}ae Spring Seat is a steel cylinder Ya of an inch long and 7 /L6 of an inch in. diameter. It is turned to a diameter of . 5/L6 of an inch for a distance of V+ of an inch'from one end for insertion in the spring. A hole L3/64 of an inch in dlame-
x
E
xa
ter is ctrilled through the spring seat to receive the release piu.
The Gollar is a steel cylinder /s of an inch in diameter and ?/16 of an inch long. A hole 7 /32 of. an inch in diameter is drilled through the center to receive the release pin. Th.e Spri,ng is made of about twelve coils of .052 of. an inch rnusic wire, with an outside diameter of 2L/64 of an inch and a normal length of. 212 inches. Th.e Shear Wi,re is a 15/16 of an inch length of copper wire 3/32 ot an inclr. in diameter. It is inserted through the holes Brovided for the purpose in the primer coutainer and nose firing pirr, and serves to prevent the firing pin from striking the primer until contact occurs. The SolcfE lli,re is a piece of. L/32 of an inch music wire. 16/a inches long below the loop, and extcntls from the safety wire guide to the release pin in the nose flring mechanism.
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Operation of the Mechanism. Upon release of the bomb the release lvire is withdrawn from the hole in the release pin, and the latter is thrown off by the action of the spring. 'When the striking plug comes in contact with any object, the force of the impact breaks the sh.ear n'ire and drives the point of the firing pin agalnst the primer. The flash from the primer passes through the hole in the base of the primer container and ignites the
a l!
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powcler charge
J
z.
20
E
z
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tu,"
in the nose of the
.
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bomb.
gE F€ ct
N
AT THE NATIONAL ARCHIVES
Authority
ey
5
NARA Date
Nomerclatut*rro.HiT #;" (o) TIw SYMBOL QUANTIT''
NAME Front
B
I
c
3
D
l I
Bomb, MarE rr.
Boily
LOCATION AND PARPOSE
MATENIAL
body.
...Steel... ..
Thermit can cover. Igniter can..... .. .,..Tin.. ..
Tin.
Firipg.tube sealing
H
Connecting ring.
'Rear
M N
.
.
body.... .....sheetsteel..
saretv wire guide"
'
sheet steer"
""
Rear cap
Stabilizers .....Sheetsteel..
R?r. portion of bomb. body.-
contains
firing mechanism and incendiary charge
' "#iill;;",l: H$l JH;,"li,HThf:l _ trap during flight. lzg5 (V) and i:s traveised by release pin ..Witaea to rear cap (R) and fastened to (AE).
ear bo.dv (4). Steady bomb after release from the plane.
in flight
w
stabilizer lugs.. .....sheet
Y
Fri"fi'ryhltrJYl';*0u"*, ,u, and stabl_.kur -lugr (IV), fastening them togethbr. Supporting m&ss.. . . .Inflammabte solidi- FiUs alt s;"ii'fi;;;;tB";L-"nd?r Therfied mass. mit cad (D). Supports thermit can (D).
sx
Stabirizer screws and
nuts.
steel..
provide means of fastening stabilizer (V) to
steer
(b) Tie Firing.
Mechanism
chamber...steel
AA
I
certridge
AB
I
Locating pin.
AD
I
Striker tube...... . . . . Brass
.
..ni"eiJa-rfi*"iaiat"ri#["av (u).
steer.
.. ..solde.red in rear of'rear bodv (M).. carries suqn'i"ot
il:*Tt'"Hl#'li'jm$?i
Locates rear cap (R).-
(AA).
AI,THE ...i;:l:.
NANOMI
ARCHIVES
DECLASSIFIED Authority
sy5
SYMBOL gUANTITY
NARA
natefp2pt
NAME
LOCATION AND PURPOSE
MATENT AL
Fits in
AF
I
Striker.
recess
in
cartridge chamber (AA)
under,striker tube (AD). Secures cartridge (AT) in position. Slides in striker tube (AD). On contact
.
fires cartridAe (AT).
AG
.
AH
.
cord roued steer. . . . . H;1"#tr""tsTI
AL AM AN
'
'
:::* ffi"ftlf""$lLot'
forward. movement ol striker (Af'). aced on . . Placed on upper end of release pin (AH) in Forces reteese releese pin (AH) out of hole in' wlen the safety wire (AP) rear gap re&rcap (R) when is withdrawn. Iower . . . . . .Plaeed on release pin (AH); acts as lower bearing for release pin spriirg (AK). . .Placed on release pin (AH); acts aa bearing for release pin (AH) and as seat for safety wire (AP). .. ..Placed on release pin (AII) over holes in
AK
AP
in striker tube (AD) under striker (AF), I{olds striker (Af1 away from
. . . . Held
Piano wire'
'
rear cap (R). Soaked in parafrn. Prevent entrance of moisture.
txTflf; t;ia
;:"::': fil"'S:t'-l*"""',1
aetuating release pin (AII).
(c) The Incend,iarg anil Erplodoe Materialt AQ
I
Creates intense
through, rear lgnrtes rncenAR
Thermit Igniter. ... . ..Igniting composition
AT
I l. I
AU
I
Black powder.
AS
L9
ctl
.
cen
(F).
Ignites
INCENDIARY DROP BOMB, MARK II. The Incendiary Drop Bomb, ntark II, is intended for use against heavy permanent structures lvhere a high degree of igniting powder is required. It is known as the '"intensive" tilre because its object is' to create and concentrate a fire of high temperature in a corhparatively small area. .
(a) The Body. The shape and external dimensions of the body are the same as those of the Incendiari Drop Boutb, Mark I. The rear body (M) is rnade of sheet zinc, .05 of an inch thick, instead. of steel; on burning the zinc produces a dense white smoke which serveb to conceal the origin of the flre. The
front plate (D), firing tube guide (F), thc loading tube (K), diaphragm (A), anal flash hole (AC), shown in Plate I have been omitted and the flring tube (G) has been shortenecl. No powcler charge is carried in the nose or rear of the bomb. T}.e Therm,it Can (D), held in the front body, is a truncated cone of 28-gauge tin plate 5.7 inches in diameter at its
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it'. L lA ia l.
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lu T F F
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L.
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top, 4 inches in d.iameter at its bottom, and 7.8 inches high. A hole .875 of an inch in diameter is drilietl in the center of the Couer (E), which is Y+ of an inch high, and closely fits the top of the cau. Inside the cover (tr), and immediately . over the hole is solderetl. thc small lgtt'i,ter Can (F) for the thermit igniter. This tin receptacle is made 1 inch high and. tr/a inches in diameter with a cover fltting securely over the top. The bottom of the therniit can (D) rests on the three stops (C) set in the nose of the front body (A) ' The cover (E) of the t[ermit can (D) is seated. on the projecting shoulder of the connecting ring (L). The nose of the bomb is fllled with a solidifled inflammable mass (Y) up to the leve1 of the stops (C) to provide aclclitional supBort for the ther mit can (D).
(b) The Firing Mechanism. The firing mechanism is the same as tirat used in the Incendiary Drop Bomb, Mark I, except t.htrt the firing tube (G) has been shortened to 16 3/16 inches. (c) Incendiary and Explosive Materials. Tt,e Thermit (AQ) is containecl in the thermit can (D). 'Ihe Therm,r,t lgni'ter is contained in the igniter can (F)' 26
On the igntting mixture is a L/e of an inch layer ot Black Pou;der (AU). As the igniter can (F) is attachecl inside the
(E) of the thermit can (D), the igniting mixture is by the thermit (AQ) when the cover of the larger can is put in place.
cover
Surrounded
The Incend,i.ary Charge (AS) consists of a specially preoil emulsion which fills the rear body. T!;.e Cartrndge (,LT) is a 30-caliber U. S., Service Cartridge.
pared
Operation of the Bomb.
(4T) is fired, and the buliet passes up the firing tube (G) thus opening the igniter receptacle (F ) to the flash of the discharge. With the aid. of the black powder (AU) this preparation (An) is ignited, and in turn sets fire to the thermit (Ae). An inUpon impact of the bomb, the cartridge
tense heat is immediately produced, and the walls of the rear body (M) are burned through; the vaporized oil is forcetl out through these orifices .and ignitetl. As the body is consumed the oil emulsion (AS) is melted and spreatls in flames
over the acljacent surfaces. Nors.-The exterior surfaces of the Mark II Incendiary Romb are painted with an olive drab paint. A black band, f inch wide, is painted around. the body to indicate the center of gravity; on this band, in white, are painted the designation of the bomb, the manufacturer's nane, the lot number, the serial number, and the inspector's initials. At a point three inches from the top, two red, band,s, 1 inch wicle antl two inches apart, are painted afound the nose to fnrther indicate the type of bomb.
,ry
