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Handbookof the

Incendiary Drop Bombs

THE NATIOiIAL ARC!{I\CJ LIBRARY

WAR DEPARTMEN'f.Document No. ?7?.

Ofi,ce of the Adiut.ant Gen'eral.

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WAR DEPARTMENT,Wessrxero*, March 25, 7918.

The following pamphlet entitled. "Ifandbook of the Incen-diary Drop Bombs, Mark I and fI," is published for the infor-matlon 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.

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TABLE OF CONTENTSPect

Plate L-Assembly drawing-Incendiary Drop Bombs,l\Iark I ... ....... 5

Chart I.-Nomenclature 6

(a) Thebotty. ....... 6

(b) The firing mechanism 8,

(c) The explosive and incendiary materialsIncendiaryDropBomb,MarkI..... :..'...... 10

(a) The botly . ....1........ 10

. (b) The firing mechanism . ..(c) The explosive and incendiary materials .. . .. 16

Operation of the bomb .-.- t7Plate Il.-Auxiliary nose flring mechanism . . 18

Operation of the mechanismPlate III.-Assembly drawinS-Incendiary Drop Bomb,

MarkII ... .......2LChart II.-Nomenclature

(a)ThebodY. "' 23

(b) The flring mechanismIncendiary DroP Bomb, Mark II . . .

(a) The bodY . " 26

(b) The firing mechanism " 26

(c) Incendiary and explosive materials. " 27

Operationofthebomb .'.... ;..." ""'27

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&'pnoouceo ar rHE NATIoNAL ARoHIvES

SYMBoL qaaNTtTY NAME

Nomenelatur.-r'""fr1T i'op norot,

MATENIAL

(a) The Bods

Mark I.

LOCATION AND PONPOSE

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Front body. ...steer . .... u.il,Ti""_.i*'.Ht j?fdfl#i""TfifiSmaterial.

Nose nuing prue'. ' "steer ' "t"liff;iT#T"$.Ptf;rIri6j",l#"i;t*ffi:"tLflY*:i:ose

nring mechan-

stops. ..sheet steer.. *;11*11',1?i3"",r3?Y).(^) Locate and

Front plate. ...Sheetsteel. ...Soldiied_in front bodv'(A) ag.aiust stois(C). Separates nose powder .charge(AQ) from incendiary charge (AS); sup-ports firing tube guide (F).

. Plate sealing disk....Tin ....Soldered on front plate (D). Prevents in-

fi:*f,:{.fluid from entering nose powder

Firing tubeguide....steel ....;....Soldered on front pla.te (-DJ, Locates and

ilB|i:f)' firins tube (G) and loading

Firing tube. . . .Steel. . .'Extdnds from diaplragT".$) to firing tube-guide (F). Guides- bullet and flash ofdiseharge.

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Fitilg tube sealing Tin. . , , Soldered over forward end of firing tubedisk. (G). Prevents entranee of ineendiary

fluid into firinc tube (G).Loading tube. . Tin. .

end of firing tube (G). Facilitates as-' sembly of front and re&r body afterloading.

Connecting ring. . . . .Steel. ..Connecti front body (A) to rear body (M).Rear body . . . . Sheet steel. . . Rear of bomb body-contains incendiary

material (AS) rear powder chargi (AR)and firins mechanism.

Safety wire guide. . . . Sheet steel. . . . Riveted oi rear lody (M). in line withstabilizer (V). Supports loop of safety

it,ljfrand steadies bomb in'trap drrring

Diaphragm " "sheet steel" *I;lEoTo,Lu' srli${"(H;""ffi"#"'"0*"-:

Re.arcap... .. su*isteer.. R"Ss)"1"i-"f"f,""9i:o;;"1"T,**1?'',r,.Carries stabili",ers (V) end is traversedby release pin (AH).

Renr filling plug. ,. . .Sheet steel. . ..Screws into filling hole plate (T). Permitsinsertion of rear powder charge (AR).

Filling hole plate'. . . .Sheet steel. i..Soldered in rear body (M). Receives rear

Filing hore disk. . . . . Lead. "r*"fit

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*;.Epnooucro AT THE NATIoNAL ARcHIvES

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Stabilizer screws and Steelnuts.

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Striker tube washer. . Steel . . . Fits in recess in cartridge chamber (AA)under striker tube (AD). Holds c&r-

. tridge (AT) in place.Striker .Steel . ..Slides in striker tube (AD).IOn contact,

fires cartridge (AT).striker spring . . steer *i'1. r"lr'$j,r':f,i:lo,"o$rJ_:rtl;St*lrlfr?]

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Release pin spring Steel.seat.

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INCENDIARY DROP BOMB, MARK I.The Incendiary Drop Bomb, Mark I, is intended fo.r use

against light structures, ammunition dumps, grain fields, orlike objectives where only a low clegree of igniting power isrequired. It is of the so-called "scatter" type, clue to theaction of the exploding charge, which capts out the incendiarymaterial within a radius of from 15 to 30 yards from thfpoint of contact

In size and shape the bomb is similar to the Mark IIIHigh 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

PIug (B), the Btops (C), the Front Plate (D), the PlateBealing Disk (E), the Fi,r'i,ng Tu,be Gu'ide (X'), the FiringTube (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 RearCop (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), theStabili,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, withwalls 3/16 ot an inch thick. In the rounded nose a hole hasbeen drilled ancl tapped to receive the .Nose Filli'ng Plug (B),which is a half-itich standard pipe plug. Through this holethe nose charge of powder is inserted; it is also designedto receive an auxiliary nose-firing mechanism, when this ip

found desirable. X''or a distance of 7/z of an inch, thq rearend of the front body (A) is threaded on the inside to re-

ceive 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 supportthe front plate'(D).

The Front Plate (D) is a circular piece of sheet steel 4.2inches in diameter and t/J,6 ot an inch ilrick, with the outeretlge bent uprvard for 12 0f an inch to fit into the front body(A) against the stops (C) where it is soldered. in place. Ahole /a of an inch in diameter is bored through its centerand sealed by means of the plate seating Dr;sk (E), a circularpiece 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 inchesin diameter and /a oL an inch long. x''or a distance of la of aninch from the front end it is drilled to a rliameter of y* of aninch to receive the firing tube (G). The bore is increased toI-.05 inches for a distance of. E/L6 of an inch from the rear endto receive the loading tube (K). The guide is soldered to theplate sealing disk (E) with the bore.in line with the holein the front plate (D).

The Eiring Tube (G) is a steel cylincler 29s7, irLeh.es longwith an insitle diameter of 9/16 of an inch ancl an outsidediameter of- Ll/16 of an inch. The front end is sealed by meansof the tin Eiring Tu,be Sealing Disk (H), 7/8 of an inch indiameter and .01 of an inch thick, peened. over and. soldered inplace, antl is inserted in the flring tube guide (X'). The rearend is inserted in the hole in the ctiaphraCm (e), and. over thefront end of the cartridge chamber (AA), and brazed inposition.

Th.e Loading Tube (K') is a tin cylinder 6.87b inches longand 1 inch in diameter, the forrvard end of which is insertedin the recess iu the flring tube guicle (F). It serves tofacilitate the flnal assernby of the front and rear bodies afterthese have been loaded with the incendiary charge (AS).

The Gonnecting Ring (L) is a steel cylinder 6.088 inchesin diameter and 1r/s inehes long. The front end is turneddown and threaded to a diameter of 5.85 inches to fit itrtothe front body (A). Around the center of the rear portionis cut a rounded channel 5/32 ot an inch wide and 1/16 of aninch 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 inchthick. It is in the shape of a truncatecl cone with a total

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length of 19.72 inches. The base of the cune is 6.038 inches indiameter to fit over the shoulder of the eonnecting rins (L).

Four Stabilizer Lugs (W) are riveted and soldered to therear body (NI) at a point 10.64 inches from the rear end toserve as a means of attaching the stabilizers (V) and rearcap (R). The lugs are sheet steel rectangles bent at thecenter, thus forming two sections Yz of at inch square perpen-

dicular to each other, which receive the rivets and stabilizerserews (X).

Th.e Safetg Wire Guide (N) is a sheet steel rectangle withrounded corners,.92x1.31 inches; it has a raised portiontA of an inch high antt 3/L6 ot an inch v'ide running length-wise through its center to form a channel for the passage ofthe 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 apoint 13/e inches from the nose of the bomb. The raised. por-

tion fits into the frame of the release mechanism and servesto steady the bomb tluring flight. In the center of the upper'surface a hole is punched to permit the passage of the safetywire 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 con-

form to the shape of the rear body (M), to which it is solderedat 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 toreceive the base of the firing tube (G) to which it is solclerecl.

The rear portion of the body tapers down to a diameterof. 2.20 inches to receive the cartriclge chamber (AA). Ata point 2y2 inclaes from the reat end, ancl midway betweenthe rear stabilizer lugs, a filling hole is driiled in the shellto receive the filling plug (S).

Tlrg Rear Fi,Ui,ng Plug (S) is a steel cylinder sl of an inchin diameter and. 5/32 ot an inch long, threacled to flt into thefllling hole plate (T). A slot 3/32.of an inch wide and 3/32of an inch deep is cut across the upper surface to providea grip lor a screw driver.

T)ae Ei,lling Hole Plate (T) is a sheet steel cylinder /s ofan inch in diameter and a/+ of an inch iong. A recess 5/32of an inch dedp is cut in one surface and tapped to receive

tlre filling plug (S). A hole. s/s of an inch in diameter isdrilled through tire center of the filling hole plate (T) to '

permit the insertion of the charge in the rear powder cham-

ber. The filling hole plate (T) is soldered to the inner sur-

face 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 byt/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 indiameter 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 thecone are flattened in two places exactly opposite each other.These surfaces are traversed by a hole Y+ of an inch indiameter 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 toreceive the steel locating pin (AB) '

The Stabitizers (V) are irregularly shapetl steel quad-

rangles .05 of an inch thick, with 4 maxirnum length of 16.27

inches and a maximum width of 3.19 inches. 'At a point

3.35 inches from the rear end is a lug 5/t6 ot an inch widea,nd 1.3? inches long, by means of which the stabilizer isweldecl 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) whichfastens.the, stabilizer to the stabilizer lug'

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(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 inthe 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

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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 aninch in d.iameter, the cartridge chamber (AA) tapers out-ward to its maximum diameter at a poiuL 4Ys inches fromthe same end. From this point it tapers down at a l3-degreeangle 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 thesurface Just described, 5/32 of an inch s'ide and, t/L6 of aninch deep, to provitle a binding surface into which the baseof the rear body (M) is peened at the time of assembly.

The extreme end of the cartridge cha,nber (AA) is offsetand tapers from a diameter of 2.075 inches at a 13-degreeangle for a distance of Yz of an inch. About .2 of an inchfrom the upper shoulder a hole is drillerl with its axis per-pendicular to this surfaee to receive the /s-inch steel Locat-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 re-ceive the striker tube (AD). For a distauce of /a of an inchfrom 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 cart-ridge charnber is bored out to receive a 30-caliber servicecartridge (AT).

The Striker Tube (AD) is a brass cylinder 2 9/16 incheslong with an outside diameter of I&/e inches and an insidediameter of 1 inch. The front end is turned down to a

diameter of. LY+ inches for a distance of 1 inch to flt into. therecess in the cartridge chamber (AA). The central sectionis threaded for a distance of /a of. an in,:h to fit the threadedportion of the cartridge chamber (AA). The outer edge atthe base is rounded off, while the inner shoulder at thispoint is cut away at a 45-degree angle to facilitate the iuser-tion of the striker (AF)

Tt.e Stri.ker Tube Washer (AE) is a steel cylinder t tinches in diameter and t/a of an inch long, with a Y+ of aninch hole through its center. It is placed in the recess lnthe cartridge chamber (AA), and the striker tube (AD) isscrewed down over it. Its purpose is to Secure tbe cartridge(AT) in place.

Tl;.e Striker (AF) is an irregularly 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

, a lug 5/16 of an inch long and s/a of an inch ln diameter' projects 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.Therearsectionofthestriker (AF) is 1/2 inches longAnd !2 of an inch in diameter'

withaT/S2ot.aninchholedrilledV+ofaninchfromtherear end to receive the release pin (AH)'

TheStrikerS1lring(AG)ismadeotfourcoilsofsteelspring 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/|6ofaninchlong 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

a. diameter of 3/16 of an inch except for a distance of /3 of an

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.aninch, 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/16ofaninchtoserveasthelowerbearlng for the spring (AK)' A hole t3/64 of an inch indiameterlsdrilledthroughthespringseat(AL)torecelvethe release Pin (AH).t

T*o felt baskets (AN), soaked in paraffin' are placed on

thereleasepin(AH)torendertheboleslntherearcap.16L4

(R) waterproof. The gaskets (AN) are t/L6 of an lnchthic\ and 7 /L6 of an inch in diameter with a hole B /t6 otan ineh in diameter. ' ' t

The Release Pin Washer (AM) i's a steel cylinder 8/16of an inch long and, 7 /L6 of an inch in tliameter with a boreot 13/64 of an inch, which is pJaced over the end of the releasepin (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) iithe order given, and the pin (AH) is then inserted throughthe holes in the rear cap (R), and the hote in the striker(AF) which has'been placed insiile the rear cap (R).. An-other felt gasket (AN) is then placed over the end of therelease pin (AH), followed by the steel washer (AM). Theend of the safety wire (Ap) is passed through the hole inthe 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 musicwire with a loop /a of. an inch in diameter 22 inches from oneencl; this end is passed through the safety wire guide (N)and extends through the release pin (AHy, the loop restingin the groove in the safety wire guide (N). The oppositeenh of the wire is 16/a inches long below the loop and ex-tends through the safety wire guide to the nose firingmechanism. When this device is uot used, the extra lengthof wire is cut off close to the loop.

(c) The Explosive and Incendiary Materials.The expldsive and incendiary materials consist of the JVose

Pouder Charge (AQ), the Rear Powcler Charge (AR), theIncendiary Charge (AS), and the Cartrid,ge (AT).

The Nose Powder Charge (AQ) consists of a quantity ofblack powder, which is inserted in the front powder chamberupon removal of the nose filling plug (B). The explosiondrives the incendiary charge (AS) out of the rear of thebomb 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 topr6vide' for the wicle dispersion of the incendiary materials.It also serves to ignite the incentliary charge (AS).

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The Incend,iary Charge (AS) consists of a mass of cottonrvaste balls soaked in a highy inflammable fluid, and pressedinto the front and rear bod.y before these are assembled..This material has a ver.y low flash point and will burnflercely for about 15 minutes.

The Cartri,clge (AT) is a standard 30-caliber servicecartrltlge.

Operation of the Bomb.Upon release of the bomb from the plane, the safety wire

(AP) is withdrawn from the release pin (AH), which isthrown' off by the action of the release pin spring (AI().The striker (AF ) is now free to move forward., except forthe restraining action of the stpiker spring (AG). Uponcontact, inertia drives the striker (AF) forward, overcomingthe force of the spring; the firing pin strikes the primer otthe cartridge (AT) and flres it. The bullet passes up thefiring tube (G) and the flash of the discharge, following thepath of the bullet, sets off the nose powder charge (Ae).The flash, at the same time, is cornmunicated to the rearpowder charge (AR) through the flash hole (AC). Theincendiary charge (AS) is thereupon blown out to a distanceof from flfteen to thirty yards from the point of impact. .Theradius of dispersion is, of course, depentlent upon the char-acter of the structure or terrain at the point of impact, andthe depth to which the bomb has penetraled.

Norn.-The exterior surfaces of the Mark I IncendiaryBomb are paintetl with an olive drab paint. A black band,1 inch wide, is painted around. the body to indicate the centerof gravity; on this band are painted, in white, the designa-tion of the bomb, the manufacturer's name, the lot number,the serial number, and the inspeetor's initials. At a pointthree inches from the tip, o' red, band,, 1 inch wide, is paintedaround the nose to further indicate the type of bomb.

The bomb is shipped, with the powder charges in a separatetin can, held in the shipping container, to prevent any mal-function of the bomb due to saturation of the powder chargewith the incendiary fluid. The powder is loadetl in the noseand rear polr'der chambers when the r-romb is made reatlyfor use.

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Auxiliary Nose Firing Mechanism.

. . The Auxiliary Nose F iring Mechanism is a flring deviceinserted in the nose of the rncendiary Drop Bomb, Mark r,t,o cause explosion of the nose powder charge as soon as possi-ble after contact with the target, and before any appreciablepenetration has occurred. rts use results in the more rapidfunctionins of the bomb, and a wider dispersion of the in-cendiary Faterials.

The auxiliary nose firing r4echanisrn consists of : ThePri,mer Container, the primer, the BtriL;ing ptug, the .l/osetr'iri,ng PLn, the Retease pin, tlne Retease pin Spring, theSpring Beof, the Coll,ar, the Shear Wire, and the Safetg Wire.

The Primer contai'ner is a steel eylind.er, measuring 1 Lr/r6inch'es in ldngth and .840 of an inch at the point ot largestdiameter. A concave recess vz of an inch wide and B/82 otan inch d.eep, at its central point, is turned 5/L6 of. an inchfrom the front end. The recess is flatted in two places'exactly opBoslte each othen, to provide a supporting surfacefor the spring seat and collar. a .204 of an inch hole isdrilled through the center of ilrese two surfaces to receivethe release Bin.

The rear end carries a 7/z of an inch stantlard pipe threadfor a distance of s/b of an inch to fit into the nose fllllinghole.

A recess is bored in the front end of the primer container.512 of an inch in diameter and L E/L6 inches long to receivef.he firing pin. Ir'rom this recess a hole .z2z of. an inch indiameter is drilled to the rear end. to receive the .22-caliberMcAda.m primer. At a point g/L6 ot an inch from the frontend, and perpendicular to the axis of the hole for the releasepin, another hole 3/32 ot an inch in diameter is drilled.throughtbe 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 froritlre rear end is a pyramidal lug measuring 5/L6 ot an inchat the base antl 7/+ of an inch high, which is inteuded tostrike the primer. The Striking plug, a steel disk Lyzinches in diameter and ye of an inch thick is riveted to the

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flring pin by means of a lug 7 /32 ot an inch loug antl Y+ ofan inch in diameter projecting from the front end of the pln.

The Release Pitt, is a built-up cold rolled steel cylintler3 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 uppbrseat for the spring. The pin is turned down to a diameterot 5/16 of an inch for a distance ot LY+ inches for insertionin tlre spring. The lower end of the pin ls made 3/t6 of aninch in diameter for insertion through the holes in the nosefiring pin and primer container, except for a distance of +b

of an inch from the end, where it tapers to 4 point. A.3/32of 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-ter is ctrilled through the spring seat to receive the release piu.

The Gollar is a steel cylinder /s of an inch in diameterand ?/16 of an inch long. A hole 7 /32 of. an inch in diameteris drilled through the center to receive the release pin.

Th.e Spri,ng is made of about twelve coils of .052 of. an inchrnusic wire, with an outside diameter of 2L/64 of an inchand a normal length of. 212 inches.

Th.e Shear Wi,re is a 15/16 of an inch length of copper wire3/32 ot an inclr. in diameter. It is inserted through the holes

Brovided for the purpose in the primer coutainer and nosefiring pirr, and serves to prevent the firing pin from strikingthe 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 safetywire guide to the release pin in the nose flring mechanism.

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 offby the action of the spring. 'When the striking plug comesin contact with any object, the force of the impact breaksthe sh.ear n'ire and drives the point of the firing pin agalnstthe primer. The flash from the primer passes through thehole in the base of the primer container and ignites thepowcler charge in the nose of the bomb.

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AT THE NATIONAL ARCHIVES

Authority

ey 5 NARA Date

SYMBOL QUANTIT'' NAME

Nomerclatut*rro.HiT #;" Bomb, MarE rr.(o) TIw Boily

MATENIAL LOCATION AND PARPOSE

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Front body. ...Steel... ..

Thermit can cover.

Igniter can..... .. .,..Tin.. ..

H Firipg.tube sealing

Connecting ring. .

Tin. .

M

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'Rear body.... .....sheetsteel.. R?r. portion of bomb. body.- contains

firing mechanism and incendiary charge

saretv wire guide" ' sheet steer" " " ' "#iill;;",l: H$l JH;,"li,HThf:l_ trap during flight.

Rear cap

lzg5 (V) and i:s traveised by release pin(AE).Stabilizers .....Sheetsteel.. ..Witaea to rear cap (R) and fastened toear bo.dv (4). Steady bomb in flight

after release from the plane.stabilizer lugs.. .....sheet steel.. ..ni"eiJa-rfi*"iaiat"ri#["av (u). pro-

vide means of fastening stabilizer (V) to

Stabirizer screws and steer Fri"fi'ryhltrJYl';*0u"*, ,u, and stabl-nuts. _.kur -lugr (IV), fastening them togethbr.Supporting m&ss.. . . .Inflammabte solidi- FiUs alt s;"ii'fi;;;;tB";L-"nd?r Ther-

fied mass. mit cad (D). Supports thermit can (D).

(b) Tie Firing. Mechanism

certridge chamber...steel .. ..solde.red in rear of'rear bodv (M).. carries

Locating pin. . steer. suqn'i"ot il:*Tt'"Hl#'li'jm$?iLocates rear cap (R).-

Striker tube...... . . . . Brass(AA).

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Authority

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SYMBOL gUANTITY NAME

AF I Striker. .

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AN

AP

AQ

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AT

AU

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MATENT AL LOCATION AND PURPOSE

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AH

AK

Fits in recess in cartridge chamber (AA)under,striker tube (AD). Secures car-tridge (AT) in position.

Slides in striker tube (AD). On contactfires cartridAe (AT).

. . . . . Held in striker tube (AD) under striker(AF), I{olds striker (Af1 away from

. cord roued steer. . . . . H;1"#tr""tsTI :::* ffi"ftlf""$lLot'forward. movement ol striker (Af').aced on upper end of release pin (AH)Forces releese pin (AH) out of hole inForces reteese pin (AH) out of hole in'rear cap (R) when the safety wire (AP)re&r- gap (R) wlen the safety wire (AP)is withdrawn.

. . . . . .Plaeed on release pin (AH); acts as lower

. . Placed on

aetuating release pin (AII).

Iowerbearing for release pin spriirg (AK).

. .Placed on release pin (AH); acts aa bearingfor release pin (AH) and as seat for safetywire (AP).

.. ..Placed on release pin (AII) over holes inrear cap (R). Soaked in parafrn. Pre-vent entrance of moisture.

' ' Piano wire' ' txTflf; t;ia ;:"::': fil"'S:t'-l*"""',1

(c) The Incend,iarg anil Erplodoe Materialt

Thermit Igniter. ... . ..Igniting composition

Black powder. .

Creates intensethrough, rearlgnrtes rncen-

cen (F). Ignites

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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 fireof high temperature in a corhparatively small area.

(a) The Body.

The shape and external dimensions of the body are thesame as those of the Incendiari Drop Boutb, Mark I. Therear body (M) is rnade of sheet zinc, .05 of an inch thick,instead. of steel; on burning the zinc produces a dense whitesmoke which serveb to conceal the origin of the flre. Thefront plate (D), firing tube guide (F), thc loading tube (K),diaphragm (A), anal flash hole (AC), shown in Plate Ihave 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 trun-cated cone of 28-gauge tin plate 5.7 inches in diameter at itstop, 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 centerof the Couer (E), which is Y+ of an inch high, and closelyfits the top of the cau. Inside the cover (tr), and immediately

. over the hole is solderetl. thc small lgtt'i,ter Can (F) for thethermit igniter. This tin receptacle is made 1 inch highand. tr/a inches in diameter with a cover fltting securely overthe top. The bottom of the therniit can (D) rests on thethree stops (C) set in the nose of the front body (A) ' Thecover (E) of the t[ermit can (D) is seated. on the projectingshoulder 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 thermit can (D).

(b) The Firing Mechanism.

The firing mechanism is the same as tirat used in the In-cendiary 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)'

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On the igntting mixture is a L/e of an inch layer ot BlackPou;der (AU). As the igniter can (F) is attachecl inside thecover (E) of the thermit can (D), the igniting mixture isSurrounded by the thermit (AQ) when the cover of thelarger can is put in place.

The Incend,i.ary Charge (AS) consists of a specially pre-pared oil emulsion which fills the rear body.

T!;.e Cartrndge (,LT) is a 30-caliber U. S., Service Cartridge.

Operation of the Bomb.

Upon impact of the bomb, the cartridge (4T) is fired, andthe buliet passes up the firing tube (G) thus opening theigniter receptacle (F ) to the flash of the discharge. Withthe aid. of the black powder (AU) this preparation (An) isignited, and in turn sets fire to the thermit (Ae). An in-tense heat is immediately produced, and the walls of the rearbody (M) are burned through; the vaporized oil is forcetlout through these orifices .and ignitetl. As the body is con-sumed the oil emulsion (AS) is melted and spreatls in flamesover the acljacent surfaces.

Nors.-The exterior surfaces of the Mark II IncendiaryRomb are painted with an olive drab paint. A black band,f inch wide, is painted around. the body to indicate the centerof gravity; on this band, in white, are painted the designa-tion of the bomb, the manufacturer's nane, the lot number,the serial number, and the inspector's initials. At a pointthree inches from the top, two red, band,s, 1 inch wicle antltwo inches apart, are painted afound the nose to fnrtherindicate the type of bomb.

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