Imperial Japanese Army Explosives
Type 97 15kg Concrete Bomb
Fuzes: A-2(b) or A-2(d)
Overall Length: 26 inches
Length of body: 17 and 3/4 inches
Diameter of body: 4 inches
Thickness of wall: 1/32 inch
Material of wall: Sheet steel
Type of suspension: Horizontal or vertical
Suspension lug: A typical Army suspension lug attached to a steel band around the body. Another suspension lug is fastened to a pipe which is part of the tail assembly.
Color and markings: Black overall. Red stripe on nose. Yellow stripe and white stripe forward of suspension lug.
Length of tail: 8 and 1/4 inches
Width of tail: 5 and 1/2 inches
Width of tail fins: 2 and 1/4 inches
Width of tail fins: 2 and 1/4 inches
Dimensions of tail struts:
-Length: 3 and 3/4 inches
-Width: 1/2 inch
-Thickness: 1/16 inch
-Length: 3 and 3/4 inches
-Width: 1/2 inch
-Thickness: 1/16 inch
Material: Sheet steel
Type of filling: Cast picric in a central exploder tube surrounded by steel pellets set in concrete.
Type of filling: Cast picric in a central exploder tube surrounded by steel pellets set in concrete.
Weight of filling:
-Picric Acid: 3 pounds
-Picric Acid: 3 pounds
Total weight of bomb: 32 pounds
Construction of body: The body is constructed of a light sheet steel cylinder which surrounds a steel central burster tube. The space between the tube and the outercasing is filled with steel pellets set in concrete. The nose of the bomb is slightly tapered. A steel adapter ring is welded to the end of the nosepiece. It is threaded internally to receive another ring which contains the nose fuze pocket. The central burster tube is an explosive filled 1/8 inch steel cylinder, 2 and 3/8 inches in diameter and 16 and 1/2 inches long. A base plug is inserted into the after end of the central tube and held in place by a friction fit.
Construction of tail: A steel pipe 7/8 inch in diameter and 9 inches long is welded to the base plug. Four tail fins are welded to the pipe and to the base plug. The tail fins are braced by a single set of box-type struts. A hinged lug for vertical suspension is attached to the after part of the steel pipe.
Type 94 10kg Substitute Bomb
Fuzes: A-2(b)
Overall Length: 27 and 1/2 inches
Length of body: 18 and 1/4 inches
Diameter of body: 4 and 1/8 inches
Thickness of wall: 1 inch (approx.)
Material of wall: Concrete
Type of suspension: Horizontal
Suspension lug: Normal Army hinged lug
Color and markings: Black overall with a red band on the nose. Markings in white: weight, place and date of manufacture.
Length of tail: 9 and 1/4 inches
Width of tail: 5 and 1/2 inches
Width of tail fins: 2 and 3/8 inches
Width of tail fins: 2 and 3/8 inches
Dimensions of tail struts:
-Length: 3 and 1/2 inches
-Width: 1/4 inch
-Thickness: 1/16 inch
-Length: 3 and 1/2 inches
-Width: 1/4 inch
-Thickness: 1/16 inch
Material: Sheet steel
Type of filling: Central tube filled with black powder
Type of filling: Central tube filled with black powder
Weight of filling: 1.2 pounds
Total weight of bomb: 22 pounds
Construction of body: The bomb consists of a thick concrete case surrounding a steel central tube. The tube is filled with loose black powder. It is threaded internally at both ends. A steel well containing a nose fuze pocket threads into the forward end of the tube. A brass disk is placed between the fuze and the black powder. The after end of the tube is closed by a male base plate. A length of pipe is attached to the base plate by four screws.
Construction of tail: Four tail fins are welded to the pipe extending from the base plate. Four single struts support the fins.
Type 1 30kg Substitute Bomb
Fuzes: A-2(b), A-2(d); or B-1(a)
Overall Length: 32 inches
Length of body: 20 inches
Diameter of body: 5 and 1/8 inches
Thickness of wall: 1/16 inch
Material of wall: Sheet steel
Type of suspension: Horizontal
Suspension lug: A typical hinged Army suspension lug is attached to a steel band which fits around the bomb.
Color and markings: Black overall with a red-tipped nose. Size and type of bomb are stenciled forward of the suspension lug. Place and date of manufacture are stenciled aft.
Length of tail: 11 and 11/16 inches
Width of tail: 7 inches
Width of tail fins: 2 inches
Width of tail fins: 2 inches
Dimensions of tail struts:
-Length: 5 and 3/16 inches
-Width: 1 and 3/16 inch
-Thickness: 1/16 inch
-Length: 5 and 3/16 inches
-Width: 1 and 3/16 inch
-Thickness: 1/16 inch
Material: Sheet steel
Type of filling: Main filling is steel pellets set in concrete. Central tube contains black powder and high explosive.
Type of filling: Main filling is steel pellets set in concrete. Central tube contains black powder and high explosive.
Weight of filling:
-Explosive filling: 2.8 pounds
-Explosive filling: 2.8 pounds
Total weight of bomb: 63 pounds
Construction of body: The body is constructed of a light sheet steel cylinder which surrounds a steel central burster tube. The space between the tube and outer casing is filled with steel pellets set in concrete.
The nose section is welded to the barrel. A steel adapter ring is welded to the end of this section. The adapter ring is internally threaded to receive another ring which contains the nose fuze pocket.
The central exploder tube contains two tinned steel canisters. The forward container is filled with black powder. The larger after container is filled with a high explosive.
The tail cone is welded to the barrel and has a fuze pocket at its apex.
The nose section is welded to the barrel. A steel adapter ring is welded to the end of this section. The adapter ring is internally threaded to receive another ring which contains the nose fuze pocket.
The central exploder tube contains two tinned steel canisters. The forward container is filled with black powder. The larger after container is filled with a high explosive.
The tail cone is welded to the barrel and has a fuze pocket at its apex.
Construction of tail: Four tail fins are welded to the tail cone and braced by a single set of box-type struts.
Remarks: The bomb body and tail cone may be pierced by 4 rows of holes 90 degrees apart. Each row contains 11 holes which are 1/64 inch in diameter. It is assumed that the purpose of the holes is to release the moisture and air in the newly cast concrete filling.
Type 95 4kg Practice Bomb
Fuzes: None
Overall Length: 26 inches
Length of body: 16 and 1/2 inches
Diameter of body: 4 and 13/16 inches
Thickness of wall:
-Concrete nose: 9/16 inch
-Steel body: 1/32 inch
-Concrete nose: 9/16 inch
-Steel body: 1/32 inch
Material of wall:
-Nose: Concrete
-Body: Sheet steel
-Nose: Concrete
-Body: Sheet steel
Type of suspension: Horizontal
Suspension lug: Rectangular suspension lug held to the bomb body by a steel eye.
Color and markings: Black overall, "4K" marked on the nose.
Length of tail: 9 and 1/2 inches
Width of tail: 4 and 7/8 inches
Width of tail fins: 1 and 7/16 inches
Width of tail fins: 1 and 7/16 inches
Dimensions of tail struts:
-Length: 3 and 1/2 inches
-Width: 3/4 inch
-Length: 3 and 1/2 inches
-Width: 3/4 inch
-Thickness: 1/32 inch
Material: Sheet steel
Type of filling: Tannic chloride smoke compound
Material: Sheet steel
Type of filling: Tannic chloride smoke compound
Weight of filling: 6.4 oz
Total weight of bomb: 8.8 pounds
Construction of body: The bomb is of three-piece construction consisting of a concrete nosepiece, sheet-steel body and wooden tail cone. The steel body fits over the after part of the nose and is held there by four screws.
The nose houses a wooden spindle extension. A steel shear wire passes through the nose and spindle extension. A wooden spindle supported by a metal collar fits into the after end of the extension. The spindle extends the full length of the body and into the tail cone. The wooden tail is held to the after end of the body by four screws. It is drilled centrally to accommodate the spindle.
A metal disk with a striker point is nailed to the after end of the spindle. A perforate steel cylinder is attached to the apex of the tail cone. This cylinder houses an ampoule containing the smoke compound. It is held in place by a base plate. A 1/8 inch steel safety pin fits through the tail cone and wooden spindle.
The nose houses a wooden spindle extension. A steel shear wire passes through the nose and spindle extension. A wooden spindle supported by a metal collar fits into the after end of the extension. The spindle extends the full length of the body and into the tail cone. The wooden tail is held to the after end of the body by four screws. It is drilled centrally to accommodate the spindle.
A metal disk with a striker point is nailed to the after end of the spindle. A perforate steel cylinder is attached to the apex of the tail cone. This cylinder houses an ampoule containing the smoke compound. It is held in place by a base plate. A 1/8 inch steel safety pin fits through the tail cone and wooden spindle.
Construction of tail: Four steel fins are attached to the tail cone by screws and are soldered to the steel cylinder. The fins are braced by two sets of box-type struts.
Operation: The safety pin is removed and the bomb is dropped. On impact the nosepiece is crushed and the wooden spindle extension is pushed into the tail of the bomb shearing the shear wire. The striker point at the end of the spindle breaks the ampoule freeing the smoke compound.
Type 2 1/3kg Cluster Bomb
Fuzes: B-5(a)
Overall Length: 10 and 1/4 inches
Length of body: 4 and 1/4 inches
Diameter of body: 1 and 9/16 inches
Thickness of wall: 1/32 inch
Material of wall: Steel
Type of suspension: Carried in clusters of 30 or 76 in a container
Suspension lug: None
Color and markings: Body is black with yellow band around center. The tail extension and tail are grey.
Length of tail: 6 inches
Width of tail: 1 and 3/4 inches
Width of tail fins: 7/8 inch
Width of tail fins: 7/8 inch
Dimensions of tail struts:
-Diameter: 1 and 3/4 inches
-Width: 1 and 1/2 inches
-Thickness: 1/16 inch
-Diameter: 1 and 3/4 inches
-Width: 1 and 1/2 inches
-Thickness: 1/16 inch
Material: Aluminum
Type of filling:
-TNT: 60%
-RDX: 40%
Type of filling:
-TNT: 60%
-RDX: 40%
Weight of filling: 4 oz
Total weight of bomb: 11 oz
Charge/weight ratio: 37%
Charge/weight ratio: 37%
Construction of body: The cylindrical steel body is crimped around the nosepiece and screwed into the forward end of the tail extension. An inner cone is found at the forward end of the body which gives a "Monroe Effect" on exploding. The tail cone which houses the fuze is screwed into the after end of the tail extension. The booster assembly is contained in the tail extension.
Construction of tail: Three aluminum tail fins are attached to the tail cone by screws. They are braced by a single hexagonal strut and by a hexagonal end plate. (See modified bomb)
Remarks: Modified Bomb: A container full of modified Type 2 40mm bombs has been recovered. These bombs are filled with Japanese Army Mark 2 explosive (Tanoyaku - 50% TNT, 50% RDX). A 5/16 inch layer of pure cyclonite poured in on top fills up the bomb body.
Evidently in an effort to reduce UXB's the arming spindle of recent bomb was lengthened about 1/8 of an inch. This increase allows the cup-shaped vanes to protrude further into the wind stream.
The end plate on the modified bombs is omitted. A 5/16 inch strut at the extreme end of the fins is substituted. A golden lacquered, thin, tinned steel is substituted for the older type aluminum tail fins.
Captured documents describe the use of this bomb in air-to-air bombing.
Type 3 1/2kg Cluster Bomb
Fuzes: A-6(a) or A-6(b)
Overall Length: 4 and 3/4 inches
Length of body: 2 and 3/4 inches
Diameter of body: 2 and 1/8 inches
Thickness of wall: 3/64 inch
Material of wall: Drawn steel
Type of suspension: Carried in clusters of 63 in a container
Suspension lug: None
Color and markings: Black overall with 9/16 inch yellow stripe 1/2 inch forward of base and a red band around the nose.
Length of tail: 2 inches
Width of tail: 3 inches
Width of tail fins: 1 and 1/8 inches
Width of tail fins: 1 and 1/8 inches
Dimensions of tail struts:
-Length: 2 and 5/32 inches
-Width: 3/8 inch
-Thickness: 1/16 inch
-Length: 2 and 5/32 inches
-Width: 3/8 inch
-Thickness: 1/16 inch
Material: Sheet steel
Type of filling:
-TNT: 58%
-RDX: 42%
Type of filling:
-TNT: 58%
-RDX: 42%
Weight of filling: 7 oz
Total weight of bomb: 14 oz
Charge/weight ratio: 50%
Construction of body: The body consists of a drawn-steel cup to which is welded a cast-steel nose.
Construction of tail: Four tail fins are spot welded to the base of the body. They are supported by a single set of box-type struts.
Remarks: A distinguishing feature of these bombs is the construction which permits fitting the nose of one bomb into the tail of another. This union of the nose and tail serves two purposes:
(1): It prevents the fuze vanes from rotating while in the cluster;
(2): It decreases the length of space needed to contain the fuzed bombs in cluster containers.
Type 2 1/2kg Bomb
Fuzes: A-7(a)
Overall Length: 4 and 13/32 inches
Diameter of body: 2 and 1/2 inches
Thickness of wall: 3/32 inch
Color and markings: Black overall with a red band around the nose.
Type of filling:
-TNT: 60%
-RDX: 40%
-TNT: 60%
-RDX: 40%
Weight of filling: 8 oz
Total weight of bomb: 14 oz (without fuze)
Charge/weight ratio: 60.7%
Description: The bomb assembly consists of a small bomb and fuze, a reel of steel cable, and two parachutes packed in a split can with a hinged bottom and a screw top. The bomb proper is a steel cylinder closed at both ends. The walls and base are made in one piece with a smaller extension drawn out from the base to take the base plug. The nose end is closed by a disk welded onto the walls. A protruding threaded collar is welded onto the disk. The cable attachment is threaded to a base plug which screws into the base of the bomb and is held there by a locking nut.
A-7(a) is an all-ways action fuze screwed into the nose collar of the bomb.
The parachute assembly consists of the main parachute, attached to the auxiliary parachute, which is attached to the reel containing 164 feet of 1/16 inch diameter steel wire, which is connected to the cable attachment on top of the bomb.
The small auxiliary parachute is 13 and 1/2 inches in diameter unfilled, and is attached to the top of the reel by nine 15-inch silk shrouds. The main parachute is 36 and 1/2 inches in diameter unfilled. Thirteen silk shrouds, 37 and 1/2 inches long, are attached to a cord leading out of the top of the auxiliary parachute by 8 and 1/2 inches of double bungee cord.
A-7(a) is an all-ways action fuze screwed into the nose collar of the bomb.
The parachute assembly consists of the main parachute, attached to the auxiliary parachute, which is attached to the reel containing 164 feet of 1/16 inch diameter steel wire, which is connected to the cable attachment on top of the bomb.
The small auxiliary parachute is 13 and 1/2 inches in diameter unfilled, and is attached to the top of the reel by nine 15-inch silk shrouds. The main parachute is 36 and 1/2 inches in diameter unfilled. Thirteen silk shrouds, 37 and 1/2 inches long, are attached to a cord leading out of the top of the auxiliary parachute by 8 and 1/2 inches of double bungee cord.
Operation: This bomb is designed for air-to-air bombing. Prior to release, the container lid is unscrewed and the safety pin removed from the arming vane. It is probable that the entire can without the lid is discharged from the airplane. Air resistance would quickly eject the contents from the container.
As soon as the bomb starts to fall through the air, the parachute opens, the cable partially unwinds, and the arming vane rotates. Ten revolutions suffice to unscrew the spindle from the fuze body: the vane and spindle then fall away. The striker and primer are now free in the fuze body, held apart only by a spring.
When the plane strikes the cable, the bomb is either drawn up against the plane or whipped up eventually hitting the plane. On impact with the plane, inertia causing the fuze parts to move in any direction except toward the nose of the fuze, will cause the striker and primer carrier to be driven together, firing the fuze, and detonating the bomb.
As soon as the bomb starts to fall through the air, the parachute opens, the cable partially unwinds, and the arming vane rotates. Ten revolutions suffice to unscrew the spindle from the fuze body: the vane and spindle then fall away. The striker and primer are now free in the fuze body, held apart only by a spring.
When the plane strikes the cable, the bomb is either drawn up against the plane or whipped up eventually hitting the plane. On impact with the plane, inertia causing the fuze parts to move in any direction except toward the nose of the fuze, will cause the striker and primer carrier to be driven together, firing the fuze, and detonating the bomb.
Remarks: Since the fuze is designed not to fire when the bomb strikes on its nose, the bombs may not explode in impact with the ground (if it misses the plane). Since the spring is quite weak, a highly sensitive and dangerous UXB may be expected.
Next Time: More cluster munitions and containers
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