Imperial Japanese Navy Explosives - Bombs (Part 6)

 
Imperial Japanese Navy Explosives



 

Type 3 No.25 Mk 31 Bomb Model 1
 

Fuzes: Type 3 electric firing device B-3(a)

Overall Length: 62 inches

Length of body: 30 and 3/8 inches

Diameter of body: 11 and 3/4 inches

Thickness of wall: 1/2 inches

Material of wall: Steel
 

Type of suspension: Horizontal

Suspension lug: Normal Navy type suspension lug
 
Length of tail: 32 inches
Width of tail: 16 and 1/8 inches
Width of tail fins: 7 and 1/8 inches

Dimensions of tail struts:
-Length: 17 and 1/4 inches
-Width: 3 and 3/8 inches
-Thickness: 1/8 inch

Material of tail: Steel
 

Type of filling: Type 98 explosive, cast

Weight of filling: 175 pounds

Total weight of bomb: 378 pounds

Charge/weight ratio: 33%
 

Color and markings: Gray overall.  Green tail struts.  No color bands on nose.
 

Construction of body: The bomb consists of a nosepiece, barrel, and tail assembly.

The nose of the bomb is blunt.  A flat metal plate is fitted into the forward end of the barrel and welded there.  The plate is drilled centrally and a gaine pocket is welded in the hole.  A flange 3 and 7/8 inches long, and 7/32-inch thick and of the same outer diameter as the barrel is welded to the forward end of the barrel.  The flange is pierced by four 1/2-inch holes just aft of the forward end.

The barrel is of tubular steel construction.  The tail cone is held by 1 row of 18 plug welds and a continuous weld to a coupling ring which fits inside the barrel.  The ring is held in the barrel by 2 rows of screws numbering 40 in all.  There is a standard tail fuze pocket at the apex of the tail cone.

Construction of tail: Four Navy type fins are spot-welded to the tail cone.  The fins are braced by a single set of box-type struts.
 
Operation: The Type 3 electric firing device is an influence fuze, operated by a photo-electric cell, which is activated by reflection of a beam of light projected from the fuze, and reflected from the target.  Aerial burst at an altitude of 7 meters or above was desired by the designers.  Fifty percent accuracy was considered to have been attained.

Type 3 No.80 Mk 31 Bomb Model 1
 

 
Fuzes: Type 3 electric firing device B-3(b)

Overall Length: 113 inches

Length of body: 72 inches

Diameter of body: 18 inches

Thickness of wall: 9/16 inches

Material of wall: Steel
 

Type of suspension: Horizontal

Suspension lug: Two guide studs on the bomb body position the steel suspension band.
 
Length of tail: 41 inches
Width of tail: 25 inches
Width of tail fins: 10 and 1/2 inches

Dimensions of tail struts:
-Length: 17 and 1/4 inches
-Width: 3 and 3/8 inches
-Thickness: 1/8 inch

Material of tail: Steel
 

Type of filling: Type 98 explosive cast in paper-wrapped blocks

Weight of filling: 922 pounds

Total weight of bomb: 1,584 pounds

Charge/weight ratio: 58%
 

Color and markings: Gray overall.  Green tail struts.  No color bands on nose.
 

Construction of body: The bomb consists of a nosepiece, barrel, and tail assembly.

The slightly tapered longitudinally welded nosepiece is closed at its forward end by a flat plate which has an 11 and 3/8-inch diameter.  The plate is drilled centrally and this nose pocket can only accommodate a Navy gaine.  

 

A metal flange is welded to this plate. It is 5 and 1/4 inches long by 7/32-inch thick and has an 11 and 3/8-inch inner diameter.  It is pierced by four 1/2-inch holes 3/4-inch aft of the forward end.  The nose section is attached to the barrel by a continuous circumferential weld and 17 plug welds.  There is a second circumferential weld at the point where the nose section begins to taper.

 

The barrel is of tubular-steel construction.  The tail cone is attached by 30 plug welds to a coupling ring which fits inside the barrel.  The coupling ring is held in the barrel by 2 rows of screws numbering 34 in all.  There is a standard tail fuze pocket at the apex of the tail cone.

 

Four Navy type tail fins are welded to the tail cone.  The fins are braced by a single set of box-type struts.

   

Remarks: The Type 3 electric firing device is an influence fuze, operated by a photo-electric cell, which is activated by reflection of a beam of light projected from the fuze, and reflected from the target.  Aerial burst at an altitude of 7 meters or above was desired by the designers.  Fifty percent accuracy was considered to have been attained.

Type 5 No.25 Mk 33 Bomb
Please make sure to read the last line of this entry

  
This bomb is designed to detonate upon approach to the earth.  It is a combination of a number of mechanical and electrical devices, all of which must operate if the bomb is to function properly.

 

Proximity detonation is to be initiated through the action of an all-ways action electrical fuze contained in a plummet which falls ahead of the bomb in flight.  An atmospheric fuze functions at the tail to open a set of four drogue plates at the tail, and release the nose plummet.   A type 15 Model 2 tail fuze is provided to detonate the bomb in case of failure of either of the other fuzes.

 

The nose section contains a 20-kilogram spherical plummet housing an all-ways action electrical fuze, connected by 20 meters of silk-clad copper cable to a Type 3 electric gaine projecting into the main explosive charge of the bomb.  The plummet is held in place in the nose of the bomb by two hinged latches held in the closed position by two steel wedges controlled, through wires, by the action of the tail drogue plates.

 

The barrel of the bomb is standard in construction, bu added provision for fragmentation has been made by the addition of a layer of cylindrical steel pellets just under the case of the bomb.

 

The tail cone is standard with the Type 15 Model 2 tail fuze (B-3(a)) in place at its apex.  The tail fin assembly is unique.  It is designed to perform the function of slowing the fall of the bomb.  It consists of a standard set of fins to which are hinged four rectangular drogue plates.  These plates are hinged at their after end so that they may lie either flat against the fins or may be extended to serve as retarding plates.  They are held in position flat against the fin surfaces by four pins which are in turn held in place by a blowout plug.

 

The blowout plug is operated by an atmospheric fuze welded in place at the tail on the longitudinal axis of the bomb.  The tail drogue plates operate the release mechanism for the nose plummet through two wires which run forward through eyelets on the outside of the barrel of the bomb.

 

When the bomb is dropped, the aneroid in the atmospheric tail fuze operates at the preset altitude, firing a squib electrically, which blows out the blowout plug at the tail, allowing the drogue release pins to move, releasing the drogue plates.  The plates assume an angle of 90 degrees with the fin surfaces, and act to slow the fall of the bomb.  

  

Through the action of the plummet release wires, the plummet is release, and falls to the end of its cable.  The all-ways action fuze in the plummet is armed by air travel, and operates through its cable and gaine to fire the main charge of the bomb upon striking the target. The Type 15 Model 2 tail fuze operates in case of failure of the all-ways action nose fuze.

 

Both atmospheric tail fuze and the all-ways action nose fuze carry their own electrical supply for firing in the form of self-contained batteries.  

  

The data on this bomb is the result of incomplete investigation, and must not be considered as specific, accurate information.

 

 

 

1-kg Practice Bomb Modification 2 and Modification 3

  

Fuzes: A-5(a)

Overall Length: 10 and 1/4 inches

Length of body: 2 and 3/4 inches

Diameter of body: 3 inches

Thickness of wall: 1/8 inch

Material of wall: Steel
 

Type of suspension: Horizontal

Suspension lug: A rectangular hinged steel lug on a plate riveted to the body with four rivets.
 

Length of tail: 7 and 1/2 inches

Width of tail: 1 and 1/4 inches
Width of tail fins: 3 and 1/2 inches
 

Dimensions of tail struts: None

Material of tail: Sheet steel
 

Type of filling: Picric burster and a red or white phosphorus main charge.

Weight of filling: 3 ounces (approximately)

Total weight of bomb: 2 pounds 3 ounces

Charge/weight ratio: 9%
 

Color and markings: White rubber nose, black body, white tail cone and fins.  Brass band just aft of rubber nose.
 

Construction of body: A hemispherical rubber nosepiece is attached by screws to the forward end of the one-piece, cast-iron body.  The bomb fuze is contained in the nose and body.  A burster charge is attached to the after end of the fuze and extends into the tail cone which is held to the bomb body by five screws.
 
The burster charge is surrounded by cotton wadding which is contained in a central tube.  The remaining space in the tail cone is filled with red or white phosphorus.

A safety plunger is depressed when the bomb is loaded in the bomb rack.  A screw type safety pin is removed when the bomb is in the bomb rack.
 

Construction of tail: Four fins are welded to the sheet metal tail cone.  There are no tail struts.

No.3 Practice Bomb Model 1

 

 

Fuzes: B-6(a)

Overall Length: 33 and 3/8 inches

Length of body: 16 and 15/16 inches

Diameter of body: 7 inches

Thickness of wall: 1/4 inch

Material of wall: Steel
 

Type of suspension: Horizontal

Suspension lug: 2 Normal Navy type lugs 180 degrees apart
 

Length of tail: 17 and 1/4 inches

Width of tail: 9 and 1/2 inches
Width of tail fins: 4 inches
Thickness of tail fins: 1/16 inch
 

Dimensions of tail struts:

-Length: 6 and 7/8 inches
-Width: 1 and 3/16 inches

-Thickness: 1/16 inch

Material of tail: Steel 
  

Type of filling: Concrete in nose and body.  Titanium tetrachloride and picric burster charge in tail cone.
Total weight of bomb: 68 pounds
 

Color and markings: The body forward of the suspension lugs is black.  Aft of lugs, the bomb is white.  Two red lines 90 degrees on either side of the suspension lugs run the length of the body and tail cone.  New color markings will be found.
 

Construction of body: The nose and body are constructed in one piece of machined steel.  The sheet steel tain cone is attached to the after end of the body by screws.  The nose and body are concrete filled.  A wooden block fills the lower part of the tail cone and a conical steel tank containing a spotting charge of titanium tetrachloride and a picric burster fits into the apex of the cone.

Four slots in the tail cone allow the smoke to escape when the burster charge ruptures the metal container.
 

Construction of tail: Four steel fins are welded tot he tail cone and are braced by a single set of box-type struts.

Type 99 No.3 Practice Bomb

 

Fuzes: B-6(a)

Overall Length: 35 and 3/4 inches

Length of body: 19 and 1/2 inches

Diameter of body: 7 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: 16 and 1/4 inches

Width of tail: 9 and 1/2 inches
Width of tail fins: 4 inches
 

Dimensions of tail struts:

-Length: 6 and 7/8 inches
-Width: 1 and 3/16 inches

-Thickness: 1/16 inch

Material of tail: Steel 

  

Type of filling: The nose is filled with fine gravel held in place by a steel separating plate.  The body contains 15 glass disks 6 and 1/2 inches in diameter and 3/4-inch thick.  A spotting charge of titanium tetrachloride and a picric burster are contained in a tank in the apex of the tail cone.  A wooden block fills the remainder of the cone.
 
Total weight of bomb: 72 pounds
 

Color and markings: The forward half of the bomb is painted black and has a green band around the nose.  The after half, including the tail cone, fins, and struts, is painted white.
 

Construction of body: The bomb is of three-piece construction.  A steel nosepiece is attached to a tubular-steel body by screws.  A tail cone is attached to a collar by screws.  The collar fits into the after end of the body and is held there by screws.

Four slots in the tail cone allow the smoke to escape when the burster charge ruptures the metal container.
 

Construction of tail: Four steel fins are welded tot he tail cone and are braced by a single set of box-type struts.

 

Remarks: The purpose of the glass disk filling in practice bombs is to lessen the damage to the target ship while still preserving the correct trajectory and ballistics of the bomb.

Type 96 Landing Flare
  

Fuze: Pull Igniter

Overall Length: 16 and 3/8 inches

Length of body: 16 and 3/8 inches

Diameter of body: 5 and 1/8 inches
 

Thickness of wall:
-Nosepiece: 1/8-inch
-Body: 1/32-inch

Material of wall: Brass nose, sheet steel body
 

Type of suspension: Hand thrown

Suspension lug: None
 

Length of tail: 6 and 3/4 inches

Width of tail: 5 and 1/4 inches
Width of tail fins: 1 and 5/8 inches
 

Dimensions of tail struts: None

Material of tail: Sheet Steel 

 
Type of filling: Illuminant
Weight of filling: 1 pound
Total weight of bomb: 6 pounds

Color and markings: Gray overall

Description: A brass nosepiece, ogival in shape is brazed to a conical body.  A brass plug screws into the nose of the flare.  It is threaded internally to hold a central tube containing the pull igniter, delay train, and illuminant.  The after end of the flare is closed by a lead cap.

Four fins are soldered to the after end of the body.

Operation: The igniter cord is pulled firing the primer which ignites the delay train.  This in turn ignites the quick match which fires the illuminant.  The heat melts the lead cap and the flame escapes through this hole.

The flare burns for 3 to 5 minutes.



 

 Landing Flare
 

 

Fuze: Pull Igniter

Overall Length: 22 and 9/16 inches

Length of body: 15 and 1/16 inches

Diameter of body: 6 and 1/4 inches

Thickness of wall: 1/32 inch

Material of wall: Sheet steel
 

Type of suspension: Launched by hand

Suspension lug: Two handles held flush against the case by springs are riveted to the body.
 

Length of tail: 7 and 1/8 inches

Width of tail: 10 inches
Width of tail fins: 2 and 1/4 inches
 

Dimensions of tail struts: None

Material of tail: Steel 
 
Type of filling: Illuminant
Weight of filling: 5 and 1/8 pounds
Total weight of bomb: 13 pounds (approximately)
Charge/weight ratio: 39%

Color and markings: Gray.  Label just below carrying handles reads "Manufacturing Date - September 1940. Naval Aerial Factory Illuminating Flare Bomb."

Construction of body: Consists of three distinct parts: Nose, Body, and Tail.  The nose is a solid metal weight which is hemispherical in shape.  It is welded to the body.  The body is of sheet-metal construction and conical in shape.  It is welded to the nose and secured to the tail portion by eight small screws.  On the exterior of the body is a tear strip which covers a small water inlet hole.  

 

Inside the body is a long central tube which extends the full length of the flare.  This tube contains the illuminating composition.  It is held in place by a large wooden spacer disk situated at the junction of the body and the tail with another wooden spacer at the junction of the body and the nose.  Spacers are held in place by small screws, six at the nose and eight at the tail.

Construction of tail: Constructed of light sheet metal with 4 fins soldered to it.  A metal cap is soldered over the end of the tail and fits around the central cylinder.  There is a small air outlet in the cap.  A percussion igniter is inserted through a hole in the cap and soldered into position. 

 

Over the end of the central cylinder is a lead cap which is soldered to the end cap.  This lead cap has a central disk of the same metal but much thinner.  The central cylinder is surrounded by an asbestos liner covered by a metal sheath.  This extends down to the wooden spacer, also covered by a metal disk.

Operation: Before dropped, remove tear strip and safety wire and pull the igniter cord.  When catch has been pulled out approximately 3/4-inch, the spring-loaded striker is released.  The striker then impinges on the primer.

A 10-inch safety fuze is ignited by the flash from the cap and, after burning for 35 seconds, the safety fuze ignites a coil of black powder.  The resultant heat melts the lead cap, allowing flash to escape.  The illumminant burns rapidly with brilliant greenish-white flame which lasts approximately 1 minute and 20 seconds.

  

Next Time: More IJN flares