Japanese submunition

[SG500]

I'm sure someone has posted one of these on the forum before but I couldn't find it. Photo of a small Japanese munition. Can someone send me the link to the thread all about this please.
Ta.
Dave.

[BOUGAINVILLE]

Here is some information on the 1/3 Kg Cluster Bomb.

TYPE 2 1/3KG H.E.A.T. CLUSTER BOMB

The 40mm warhead is a shape charge (H.E.A.T.) type. The 1/3 Kg Type 2 air dropped cluster munition used a wind activated screw safety for the base detonating fuse.

CHARACTERISTICS.
a) The bomb utilizes the body of Fuze B.5(A) as part of its own construction
b) The principle of a hollow-cone charge is employed

DETAILS.
Dimensions:
Lengths – overall 10 1/4"
body including nose 4 1/4"
tail tube 2"
tail unit 4"
Diameter of barrel 1 1/2"
Barrel wall thickness 3/100"

Weights:
Burster charges – TNT/RDX 104 grams
RDX 4.6 grams
Booster charge RDX 5.7 grams
Total charges 114.3 grams

Colour:
BLACK body and nose
ALUMINIUM – like tail tube and fins

Markings:
YELLOW 3/8" band around barrel.

USE.
· ARMY Air force bomb which is carried in a cluster of 76 bombs in a container.

· Bomb is mainly for AA usage, both airborne and grounded. Other suitable targets include AFVs and constructions.

DESCRIPTION (See diagram)
The bomb comprises 3 main structural portions:
a) Nose piece. Attached for ballistic purposes is a hollow domed-cone constructed of 1/50" thickness sheet steel. (In UXBs, the nose will tend to collapse on impact with hard surfaces.)

b) Body. The barrel wall is of pressed steel 3/100" thickness, and bent over to retain the nose piece. Located in the body is a hollow-cone of thin pressed steel. The main burster charge of TNT/RDX is cast in the space between the cone and the body walling. Cast in the neck of the body is a smaller burster charge of RDX which serves as a subsidiary booster.

c) Tail assembly is constructed wholly of anodised duralumin (aluminium-like in appearance) and com­prises –
i. Tail tube (or tail extension piece) which screws over the neck of the body and is threaded at the rear end to receive the body of fuze B.5(A). The septum is perforated centrally to take an initiator. A cup containing a burster charge of RDX (5.7 grams) fits inside a cardboard cylinder, both sliding into the tube below the septum.
ii. Fuze body. This also serves as a tail cone. For detail description see Japanese Bomb Fuze B.5(A).
iii. Tail fin unit. 3 fins are screwed to the conical fuze body and are braced mid-length with hexagonal-strutting of shape and length as shown. A hexagonal-shaped plate closes their extreme end to ensure vertical descent.

FUZING.
Tail fuze B.5(A) is a structural part of the bomb. For description see Japanese Bomb Fuze B.5(A).

LEGEND

ITEM -----------------------------MATERIAL

1 NOSE PIECE ---------------------STEEL
2 CENTRAL CONE ---------------STEEL
3 BODY CASING ------------------STEEL
4 CONE CAP -----------------------STEEL
5 TAIL TUBE ----------------------DURALUMIN
6 BODY OF FUZE ----------------DURALUMIN
7 CYLINDER -----------------------CARDBOARD
8 BOOSTER CONTAINER------ ALUMINIUM
9 WASHER -------------------------ALUMINIUM
10 BLUE SILK GAUZE
11 BLUE SILK GAUZE
12 WASHER -------------------------ALUMINIUM
13 LEAD AZIDE CONTAINER --ALUMINIUM
14 CUP HOLDER -------------------ALUMINIUM
15 DETONATOR HOLDER -------BRASS
16 CREEP SPRING -----------------STEEL
17 INERTIA PELLET --------------STEEL
18 GUIDE SCREW -----------------STEEL
19 INITIATOR
20 BURSTER -----------------------R.D.X./T.N.T. (50/50)
21 BURSTER -----------------------R.D.X.
22 BOOSTER -----------------------R.D.X.
23 DETONATOR -------------------LEAD AZIDE & P.E.T.N.
24 TAIL FINS -----------------------DURALUMIN

[SG500]

Thanks Bougainville, very useful information.

Dave.

[JCB99]

Good item. Here is a great website with some pics and info about these cluster bombs.

http://www.inert-ord.net/jap02h/index.html

Jim

JapaneseOrdnance(at)yahoo.com

[pzgr40]

Very nice! Must be an absolute rare piece.

[SG500]

Thanks again, interesting web site on that link.
Dave.

[ogreve]

Hi Dave,

That's a lovely sample you have there, and it's nice to see the rotating-cup-screw in place too!

Bougainville already provided a lot of useful information, but there's a funny thing about this item, which I didn't see mentioned here (unless I overlooked it): this cluster bomb has got a funky shape, right?
Well, there's a reason for that: it is based on the 40mm rifle grenade.

I have attached two PDF excerpts from OpNav 1667, one treating the cluster bomb, and the other one treating the rifle grenade.

Note: I had to split the PDF file on the cluster bomb in two separate ones, as it was 7Kb bigger than the allowed PDF file size limit.

Request to the moderators: it would be nice if the size limitations for attachments could be set a bit less tight... I hope that's possible (without wasting too much disk space)? :P

Enjoy!
Olafo

[BOUGAINVILLE]

Hi all,
Thought that this might be of iinterest. This is the container for the 1/3 Kg. Cluster Bomb.

JAPANESE 1/3 Kg H.E. CLUSTER BOMB CONTAINER
DETAILS
Dimensions:
· Overall length 3' 5 1/2"
· Diameter 8"
· Wall thickness 0.050" (16 gauge)
· Thickness of end plates 0.075" (13 gauge)

Weights:
· Container empty 20 1/4 lbs
· Filled (bombs & packing) 35 Kg (78 lbs)

Colour:
· Painted BLACK.

USE
Contains 76 ARMY Air force type 1/3 Kg H.E. bombs packed in 4 sections each of 19 barbs.

DESCRIPTION (See diagram)
The container is formed by 3 interlocking lengths of corrugated sheet steel closed at each end by hexagonal sheet steel plates. The 3 lengths are held in position by 4 encircling sheet steel bands and clips. The clips are prevented from opening by 2 arming wires.

Attached externally to each end plate are 3 Bungee cords 7 1/2" long with a steel hook at the end of each.

One of the 3 interlocking lengths serves as the upper portion of the horizontally suspended container. To this portion is spot welded a smooth semi-circular sheet steel piece 2' 10" long, in the centre of which is located a swinging type suspension lug.

On each side of the lug, between it and the inner steel bands is welded a small eye-bolt through which the arming wires pass.

The 4 internal sections, each containing a group of 19 packed bombs, are formed by a transverse card­board disc between each group.

OPERATION (assumed).
The arming wires are made fast at their centre to the bomb rack. On release of the container the arming wires slip the eye-bolts and clips, the encircling bands and end plates fall away and the interlocking sections separate, thus releasing the cluster.


Cheers,
BOUGAINVILLE

[SG500]

Thanks Olafo and Bougainville, very interesting information. Its amazing to think of the amount of time it must have taken to make not only one of these little bombs but then to pack them in a bigger container made up of loads of them, same as with Butterfly bombs I suppose, a lot of work needed to do it.
Dave.

[BOUGAINVILLE]

Hi once again,
Thought that I might post the information about the B-5(a) Fuze which is used exclusively on the 1/3 Kg Cluster Bomb.

B-5(a) Army Mechanical Impact Tail Fuze
Bombs Used In: 1/3 Kg. Anti-Aircraft Cluster

Data
Colour: Aluminium.
Overall Length: 3.37 inches (including tail extension).
Overall Width: 1.3 inches
Material Of Construction: Aluminium

Position & Method Of Fixing In Bomb: Tail fuse held under tail cone with vanes and arming spindle protruding perpendicular to side of bomb body.­

Components Of Explosive Train: Lead azide primer, cyclonite detonatar and T.N.T Cyclonite main filler.

Delay Times: None

Description: Fuze body houses an inertia striker which is secured by the arming vane assembly which protrudes from the side of the body. The arming vanes are cup-shaped. A guide key keeps the striker from turning. A creep spring keeps the striker away from the primer flash cap after the arming vane assembly falls away. The tail assembly hides the fuze to a great extent.

Operation: The arming vane assembly unscrews and falls away after the bomb ia released from the container. The striker has a tendency to creep up to the top of the primer flash cap. This is prevented by the creep spring. On impact, inertia causes the striker to move downward against the creep spring. The striker pierces the primer and the exploder system is set into operation.

Remarks: On modified 1/3 Kg, bombs recovered, the arm­ing spindle was lengthened about 1/8 of an inch. The new length allows the cup shaped vanes to protrude further into the wind stream.

Hope you all enjoy,
Cheers,
BOUGAINVILLE