Monday, 14 March 2016

Imperial Japanese Navy Explosives - Bombs (Part 3)

 
 
 
Imperial Japanese Navy Explosives
 
 
 
 
 
 
Type 99 No.6 Mk 2 Bomb Modification 1
  
 
Fuzes: A-3(a)
Overall Length: 42 inches
Length of body: 21 inches
Diameter of body: 9 and 3/8 inches
Thickness of wall: 3/16 inch
Material of wall: Steel
 
Type of suspension: Horizontal
Suspension lug: Normal Navy type suspension lug
 
Length of tail: 21 inches
Width of tail: 13 and 1/4 inches
Width of tail fins: 6 inches
 
Dimensions of tail struts:
Outer Struts
-Length: 9 and 1/2 inches
-Width: 1 and 3/8 inches
-Thickness: 1/16 inch

Inner Struts
-Length: 4 and 3/4 inches
-Width: 1 and 3/8 inches
-Thickness: 1/16 inch
Material of tail: Sheet Steel
 
Type of filling: Type 98 explosive
Weight of filling: 85 pounds (approximate)
Total weight of bomb: 140 pounds
Charge/weight ratio: 60%
 
Color and markings: Gray overall with a green-tipped nose and a blue band just aft of the green.
 
Construction of body: A cast-steel nose is attached to a tubular-steel body by a continuous circumferential weld and 2 rows of 16 plug welds.  An anti-ricochet nose attachment consisting of a cylindrical metal ring 1/8-inch thick bent at a 90 degree angle is spot welded to the bomb at a point 1 and 1/2 inches forward of the junction of the nose and body.

The ring is 9 and 3/8 inches in diameter and 3 and 3/4 inches long.  There are two notches 7/8-inch wide and 2 and 1/4 inches deep cut into the forward edge of the ring 180 degrees apart and in line with the suspension lug.

The tail cone is attached to a collar by a continuous circumferential weld and 16 plug welds held there by 2 rows of 16 screws.
 
Construction of tail: Four tail fins are welded to the tail cone and are braced by four sets of box-type tail struts.



 
Type 1 No.25 Mk 2 Bomb Model 1

 
Fuzes: A-3(a), B-3(a)
Overall Length: 72 inches
Length of body: 35 and 1/2 inches
Diameter of body: 13 and 3/4 inches
Thickness of wall: 1/4 inch
Material of wall: Steel
 
Type of suspension: Horizontal
Suspension lug: Normal Navy type suspension lug
 
Length of tail:
-First section: 21 and 1/2 inches
-Extension: 15 inches
Width of tail: 14 inches
Width of tail fins: 5 and 1/4 inches
 
Dimensions of tail struts:
Forward Struts
-Length: 5 and 1/4 inches
-Width: 2 inches
-Thickness: 1/8 inch

After Struts
-Length: 5 inches
-Width: 1 and 1/8 inches
-Thickness: 1/16 inch
Material of tail:
-First section: Sheet Steel
-Extension: Plywood

Type of filling: Type 98 explosive
Weight of filling: 317 pounds
Total weight of bomb: 572 pounds
Charge/weight ratio: 56%
 
Color and markings: Gray overall with a green band forward of a blue band on the nose.
 
Construction of body: A cast-steel nose is attached by a continuous circumferential weld and 16 plug welds to a longitudinally welded tubular steel body.  A tail cone is attached to a collar by 36 screws.  The collar is held in the base of the bomb body by a single row of 16 plug welds.
 
Construction of tail: The tail is constructed in two sections, the first section has eight 1/8-inch sheet steel fins welded to the tail cone and supported by seven steel struts.  The second section consists of eight plywood fins in steel frames supported at their inner edges by a metal cylinder 4 inches in diameter and on their outer edges by seven steel struts.  The second section is attached to the first by bolted steel plates on each of the eight fins. 

Apparently the wooden tail section is designed to come off on water impact.



 
Type 1 No.25 Mk 2 Bomb Model 1 Modification 1


 
Fuzes: A-3(a), B-3(a)
Overall Length: 72 inches
Length of body: 35 and 1/2 inches
Diameter of body: 13 and 3/4 inches
Thickness of wall: 1/4 inch
Material of wall: Steel
 
Type of suspension: Horizontal
Suspension lug: Normal Navy type suspension lug
 
Length of tail:
-First Section: 21 and 1/2 inches
-Extension: 15 inches
Width of tail: 14 inches
Width of tail fins: 5 and 1/4 inches
 
Dimensions of tail struts:
Forward Struts
-Length: 5 and 1/4 inches
-Width: 2 inches
-Thickness: 1/8 inch

After Struts
-Length: 5 inches
-Width: 1 and 1/8 inches
-Thickness: 1/16 inch
 
Material of tail:
-First Section: Sheet Steel
-Extension: Plywood
 
Type of filling: Type 98 explosive 
Weight of filling: 317 pounds
Total weight of bomb: 585 pounds
Charge/weight ratio: 54%
 
Color and markings: Gray overall with a green band forward of a blue band on the nose.
  
Construction of body: A cast-steel nose is attached by a continuous circumferential weld and 16 plug welds to a longitudinally welded tubular steel body.

An anti-ricochet attachment consisting of a metal ring and two supporting plates is welded to the bomb at a point 1 and 3/4 inches forward of the junction of the nose and body.  The ring has a 13 and 3/4 inch diameter, is 5 inches long and 5/32-inch thick. 
 
The two semicircular supporting plates are welded to the interior of the forward end of the ring and to the nose of the bomb.  There are two notches cut into the forward edge of the ring 180 degrees apart.  One notch is in line with the suspension lug.  The supporting plates fail to meet by 7/8-inch at the two notches.

A tail cone is attached to a collar by 36 screws.  The collar is held in the base of the bomb body by a single row of 16 plug welds.
  
Construction of tail: The tail is constructed in two sections: the first section has eight 1/8-inch sheet steel fins welded to the tail cone and supported by seven steel struts.  The second section consists of eight plywood fins in steel frames supported at their inner edges by a metal cylinder 4 inches in diameter and on their outer edges by seven steel struts.  The second section is attached to the first by bolted steel plates on each of the eight fins. 
 
Apparently the wooden tail section is designed to come off on water impact.


 

Type 99 No.3 Mk 3 Bomb
  
  
Fuzes:
-Nose: A-1(b), A-3(c)
-Tail: Solid plug or D-2(a), D-2(b), or D-2(c) 
Overall Length: 24 and 1/2 inches
Length of body: 13 and 1/2 inches
Diameter of body: 5 and 3/4 inches
Thickness of wall: 3/16 inch
Material of wall: Steel
 
Type of suspension: Horizontal
Suspension lug: Two normal Navy suspension lugs diametrically opposed
 
Length of tail: 11 inches
Width of tail: 6 and 1/8 inches
Width of tail fins: 1 and 11/16 inches
 
Dimensions of tail struts:
-Length: 4 and 1/8 inches
-Circumference: 3/16 inch
Material of tail: Sheet Steel
 
Type of filling: Canister containing 168 phosphorus-filled steel pellets.  Picric acid in tail cone and central burster charge.
 
Weight of filling: Picric Acid - 3.5 pounds
Total weight of bomb: 70 pounds

Color and markings: Gray body and tail.  A 2-inch silver band around the nose, a 1-inch silver band on the end of the tail fins, and two red lines diametrically opposite run from nose to tail.  New markings will be found.
 
Construction of body: A cast-steel nose piece is circumferentially welded to a longitudinally welded steel body.  A canister containing the incendiary pellets is fitted inside the body.  A steel tube containing the central burster charge is screwed into the nose and extends the length of the body. 

A tail cone is circumferentially welded to a collar which threads into the after end of the body.  The tail cone is filled with picric acid.  A steel plate separates the explosive from the incendiary filler.
 
Construction of tail: Four steel fins are spot welded to the tail cone.  They are braced by a single set of 3/16-inch round struts flattened at each end and riveted to the fins.

To impart the rotary motion necessary to arm the D-2 fuzes, the ends of the tail are bent at an angle of approximately 19 degrees.

Remarks: A factory variation of the incendiary filling consists of 21 lengths of mild steel pipe, 1-inch in diameter, packed vertically in the canister.  Each length is divided into 8 equal sections by being cut completely through except for 1/4 inch of circumference left along 1 side.  The bomb contained 168 phosphorus-filled pellets.

Modification 1: A variation of this bomb listed as Modification 1 has four fins welded to the body and utilizes the new color markings.  The fins, which are 6 inches long, 1 and 1/2 inches wide, and 1/16-inch thick, are welded tot he body at 4 and 5/8 inch intervals, two between each suspension lug. 

They are offset 35 degrees from the longitudinal axis of the bomb and serve to accelerate its clockwise rotation.  The bomb is painted gray.  It has a silver nose tipped with green.  The tail struts are red.





Type 3 No.6 Mk 3 Bomb Model 1


Fuzes: D-2 series
Overall Length: 40 inches
Length of body: 23 inches
Diameter of body: 7 and 7/8 inches
Thickness of wall: 1/8 inch
Material of wall: Steel
 
Type of suspension: Horizontal
Suspension lug: Normal Navy suspension lug
 
Length of tail: 17 inches
Width of tail: 7 and 7/8 inches
Width of tail fins: 2 and 1/2 inches

Dimensions of tail struts:
-Length: 5 inches
-Width: 1 and 1/2 inches
-Thickness: 1/8 inch
Material of tail: Steel
 
Type of filling: Three cylindrical steel canisters each containing 87 white phosphorus filled cylindrical steel pellets.  Each canister has a central exploder tube filled with Type 98 explosive.  A heavy wax coating covers each canister.

Dimensions of filling:
-Length of canister: 4 and 3/8 inches
-Diameter of canister: 7 and 1/4 inches
-Length of pellet: 1 and 1/4 inches
-Diameter of pellet: 1 and 1/8 inches
-Diameter of exploder tube: 1 and 7/16 inches
-Weight of individual canister: 24 pounds
  
Weight of filling: 3 canisters, 72 pounds; tail cone charge - 11.2 pounds
Total weight of bomb: 118 pounds
Charge/weight ratio: 71%
 
Color and markings: Silver nose tipped with a green band.  Body is gray overall, except for red tail struts.  Marked "Provisional designation Type 3 No.6 Mk 3 Model 1".
 
Construction of body: The bomb consists of a nosepiece, body, and tail assembly.  The conical-shaped nosepiece is welded to the body and has a steel plate welded where the fuze pocket would be.  The cavity in the nosepiece is filled with a wooden block.  The body is cylindrical in shape and is welded longitudinally. 

The tail cone is welded to a coupling ring which fits into the body and is held there by a single row of screws. A burster charge of cast Type 98 explosive is contained in the tail cone.  A perforated steel plate separates the explosive from the incendiary filling.
 
Construction of tail: The tail cone is welded longitudinally.  Four angled fins are welded to the cone and braced by a single set of box-type struts.  The angle of these fins imparts a counter-clockwise rotation in flight to the bomb, thereby arming the clockwork fuze.

Operation: Upon release from the plane the aerial burst fuze functions initiating the tail cone charge which detonates the central burster tube.  The bomb case and canisters are ruptured, scattering the incendiary pellets.  The white phosphorus is ignited when it is exposed to the air.




Type 2 No.25 Mk 3 Bomb Model 1
 

Fuzes:
-Nose: A-3(a)
-Tail: D-2(a)
Overall Length: 71 inches
Length of body: 40 inches
Diameter of body: 12 inches
Thickness of wall: 1/4 inch
Material of wall: Steel

Type of suspension: Horizontal
Suspension lug: Normal Navy suspension lug

Length of tail: 31 inches
Width of tail: 12 inches
Width of tail fins: 5 and 1/4 inches

Dimensions of tail struts:
-Width: 2 inches
Material of tail: Sheet Steel
  
Type of filling:
-Incendiary filling: 750 (approx.) steel cylinders containing an incendiary mixture
-Barium nitrate: 35.8%
-Iron oxide: 27.2%
-Aluminum powder: 13.6%
-Magnesium shavings: 10.3%
-Synthetic shavings: 13.1%

Dimensions of cylinders:
-Length: 2 and 3/4 inches
-Width: 1 and 1/16 inches
-Thickness: 1/8 inch

Packing of cylinders: The cylinders are packed in circular rows in nine perforated nitrocellulose containers.

Burster charges: Two burster charges are contained in the nose piece and in the tail cone.  The explosive is also scattered throughout the interstices of each incendiary section.

The composition of the charge is as follows:
-Barium nitrate: 75.2%
-Aluminum powder: 24.2%
-Oil: 2%

Note: Perforated steel plates in the nose and tail separate the burster charges and the incendiary filling.

Weight of filling:
-Burster charges: 73 pounds
-Incendiary filling: 300 pounds
Total weight of bomb: 550 pounds

Color and markings: Gray overall.  Silver nose tipped with green.  Red tail struts.

Construction of body: A cast-steel nose is welded to a tubular-steel body by a continuous weld and a row of 12 plug welds.  The tail cone is held by 1 row of 18 plug welds and a continuous weld to a collar which is held in the base of the bomb by 2 rows of round-headed screws, 20 in each row.

Construction of tail: Four steel fins are welded at an angle to the tail cone.  The fins are braced at the juncture with the tail cone by a steel strip welded to the underside of the bent fin and the cone.

At the after end, the fins are braced by two sets of box-type struts.  The angle of the fins imparts a counter-clockwise rotation in flight to the bomb.

Operation: The aerial burst fuze functions at a preset height.  The detonation of the burster charges ignites the inflammable trays and the incendiary cylinders and ruptures the bomb case.  The fragments are scattered over a 175 yard radius when air-burst occurs 100 feet above ground.



 
Type 3 No.25 Mk 4 Bomb Modification 1
Please make sure to read the remarks section of this entry
 
 
Overall Length: 1.9 meters
Weight of explosive: 3.5 kilograms
Diameter: 0.3 meters
Weight of propellant: 15.0 kilograms
Maximum speed: 100m/sec
Total weight: 315 kilograms

General description: Design work on this bomb was originally started in 1935, and produced the Basic 3 No.25 Mk 4 bomb, which was used for all early Japanese Navy rocket testing and research.  Production commenced on the Type 3 bomb in 1943, and a reasonable number of the bombs had been produced or were in the process of production at the end of the war.

This bomb is an example of the early ideas on the use of rocket power.  It is essentially an armor-piercing bomb, designed to utilize rocket power to increase penetration.  However, as finally produced, the bomb had a maximum velocity of only 100 meters per second, and consequently was of little value.

The bomb consists of an armor-piercing explosive nose section, a rocket motor tail section, and a cylindrical center section joining the two, and carrying the fuzes for both sections.  The armor piercing nose is of extremely heavy construction, and is fuzed in the base with a fuze incorporating a short delay.  A very small explosive charge, approximately 3.5 kilograms in weight, is used as a burster.  Type 91 explosive is used, as in all other Japanese Navy armor piercing ammunition. 

The rocket motor tail section constituted about half of the overall length of the bomb, and carried 15 kilograms of propellant of the ballistite type.  It is fuzed at its forward end for ignition of the propellant, with a fuze which operates after the bomb leaves the plane.  The tail section is equipped with standard fins for stabilization of the bomb in flight.

The cylindrical center section of the bomb has the function of joining the nose and tail sections and of carrying the fuzes for both.  Both fuzes, with arming vane extensions which project out of the side of the bomb.  Two hinged doors in the side of the bomb allow access to the fuzes.

Remark: The data on this bomb are the result of incomplete investigation, and must not be considered as specific, accurate information.
 
Next Time: Even more Navy bombs!

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