American Projectiles and Explosives - Chemical, Incendiary, Smoke - "M" Series Bombs

American Projectiles and Explosives



Explosive Bombs

"M" Series

10-pound Incendiary M74

Overall length: 19.4 inches
Body length: 19.4 inches

Body diameter: 3 inches
Tail length: 6.3 inches
Tail width: 2.5 inches
Filling: PT 1 or NP

Construction: This bomb has the same type of construction as the 6-pound Oil Incendiary Bomb AN-M69, with a sheet-steel leak-proof casing and a nose cup housing the fuze.  A small chemical container, located immediately behind the dome of the nose cup, is filled with white phosphorus, to aid ignition of the incendiary composition and produce smoke.  In bombs with NP, the filling is enclosed in a cheesecloth sock; if PT 1 is used, it is loaded directly into the bomb.  The Incendiary Bomb M74 has a telescope-type tail which fits inside the tail cup and is ejected under spring pressure when the bomb is released from the cluster.  A well inside the tail cup holds the tail sleeve when the assembly is compressed in the cup.

Operation: The striker of the Fuze M142 or M142A1 ignites the primer, which sets off the booster and main ejection charge.  This activates the auxiliary ejection-ignition charge.  Expanding vases rupture the dome-shaped ejection diaphragm, which forces the WP-filled cup, incendiary filling, tail cup, and tail assembly out of the bomb casing.


Remarks: Do not reinsert arming pin after it has been ejected, as it may cause the fuze to function.

The experimental bombs of this type with other fillings are designated the E5 series.  The experimental bomb with a white phosphorus filling has been rejected; however, the one with the mustard filling, E5R8, is still under development.  This bomb will be carried int he Cluster E61 holding 38 bombs (Cluster Adapter M23).




Cluster Adapter E6R2

Overall length: 59.06 inches
Body diameter: 14.69 inches
Tail width: 16 to 18 inches


General: The cluster adapter has a thin steel body that is shaped like a bomb, except the nose is not rounded off to make a full hemisphere.  A standard-type bomb fin is affixed to the rear of the adapter, and a fuze fits in the nose.  Hoisting and suspension lugs are located at the top.  Internally, the adapter is equipped with cluster bars for positioning of the bombs when loaded.  An L-shaped angle bar runs the entire length of the adapter along the bottom cluster bar.  Into the angle bar is fitted a light steel tube which encloses a length of primacord that extends from the nose fuze to the other end of the cluster adapter.  When the cluster is filled, the bomb are packed nose-forward, 19 in the front half of the adapter and 19 in the after portion.  The assembly is held together by nine nailless steel straps.  The cluster adapter then becomes a 500-pound aimable cluster that will fit any 500-pound bomb station, and, when dropped from high altitude, approximates the trajectory of a 100-pound demolition bomb.

Operation: On release, the arming wire is pulled, allowing the clockwork to start and the vanes to turn.  When the vanes have made the proper number of turns, a striker-pin safety block falls out, completely arming the fuze, so that it functions upon expiration of the predetermined time setting.  Firing of the fuze detonates the primacord, which runs the full length of the adapter.  Explosion of the primacord breaks the nine nailless steel straps, allowing the cluster adapter wall to open and the bombs to scatter.


Remarks: If desired, the cluster adapter may be kept intact during the entire period of flight, bursting open on impact.

This adapter is being replaced by the Cluster Adapter M28

Cluster Adapter M10A1

No picture available

Overall length: 56 inches

Diameter: 15.3 inches

General: The cluster adapter is streamlined in shape, and, when filled, it becomes a 500-pound aimable cluster designed to be carried by any plane equipped to carry a 500-pound bomb.  Clusters formed with this adapter are the AN-M14, which contains 104 Incendiary Bombs AN-M50TA2, four AN-M50XA3 Type A, and Two AN-M50XA3 Type B; and the AN-M17A1, which contains 88 Incendiary Bombs AN-M50A2, 16 AN-M50XA3 Type A, and six AN-M50XA3 Type B.

The cluster adapter consists of a thin metal case with a channel bar extending through the center, and a standard tail fin fixed to the after end plate by means of a single heavy bolt.  At the forward end, a rounded nose fairing is fastened to the forward end plate.  From the fuze seat, a length of primacord extends through a thin metal tube to the after end of the adapter.  The adapter is equipped with three suspension lugs, the center lug added for use in British planes.  When the cluster adapter is loaded, the bombs are packed around the channel bar and the assembly is held in place by nine metal straps.

Operation: On release, the arming wire is pulled, allowing the fuze to arm and fire at the pre-set time.  When the fuze fires, the primacord is detonated, breaking the metal straps holding the assembly together and allowing the bombs to fall free.


Remarks: The Cluster Adapter M10A1 is similar in appearance to the E6R2, but differs internally.  The bombs in the M10A1 are packed around a channel bar, while in the E6R2 the cluster bars surrounding the bombs hold them in place.

Cluster Adapter M23

Overall length: 59.5 inches

Body diameter: 14.75 inches
Tail width: 19 inches

General: Cluster Adapters M23 are used in forming 500-pound aimable clusters of incendiary or chemical bombs.  Cluster may be carried by planes equipped to handle 500-pound bombs.  They are designed for use in high- and medium-altitude bombing, the flight characteristics resembling those of the Practice Bomb M38A2

Description: The cylindrical halves of the cluster wall are joined at the top by a suspension bar and at the bottom by a burster-shield support bar.  Cluster bars, fitted into the end plates, hold the bombs in position inside the adapter.  Ballast weights are bolted by studs to the front and rear of the adapter's end plates.  Nine steel straps, drawn tight and fastened by a metal connector, are attached to release buckles which are placed on alternate sides of the suspension bar.  The buckles are held closed by two release wires attached to a release lever, which in turn is attached to a stud on the tail cone.  The tail assembly is composed of a modified box-type fin on a conical support, with two tail-fuze adapters attached to opposite sides of the cone.  The long stud, which extends through the rear ballast weight, supports the tail assembly.

The primacord wiring of the adapter is in two sections.  A metal tube channels a 60-inch length of primacord from the forward end of the burster shield, through the tail cone, and into the base of the "long" fuze adapter.  A 31-inch length extends from the tail cup into the "short" fuze adapter.


Clusters: Bombs are clustered in two sections, 19 bombs in each, with the nose to the front of the cluster.

Operation: On release, the arming wires are withdrawn and the two fuzes arm.  Upon expiration of the time setting, the "short" fuze operates to set off the booster and the primacord, which is channeled to the fin-retaining cup.  The cone is blown off by the primacord detonation, thereby withdrawing the buckle release wires and opening the cluster.  Upon failure of the "short" fuze to function, the "long" fuze operates two seconds later.  This detonates the primacord extending the length of the cluster, which shears the steel straps and releases the bombs.


Remarks: Some lots of adapters were shipped without buckles and release wires, the release of the bombs being dependent on the severing of the steel strapping bands.  The primacord from the "short" fuze is taped at a right angle to the primacord leading from the "long" fuze, to form one primacord assembly.  Operation of either fuze would detonate the primacord extending the length of the cluster, thereby severing the steel strapping bands and releasing the bombs.





115-pound Chemical M70

Overall length: 48.7 inches
Body length: 40.4 inches
Body diameter: 8.1 inches
Wall thickness: 0.224 inches

Tail length: 12.9 inches
Tail width: 10.9 inches
Tail weight: 3.5 pounds

Filling: Mustard (H)
Weight of filling: 57.1 pounds
Total weight: 122.5 pounds
Charge/weight: 46.6%


Construction: The bomb is made from a seamless steel tubing, with an ogival nose threaded to receive the nose fuze.  A burster-well tube runs the entire length of the body, fitting into a positioning cup at the rear.  The tail assembly consists of four fins welded to a sleeve, which is secured by a locking nut threading into the tail closing block.  The fins are supported by box-type struts.


Suspension: The bomb is carried horizontal by dual lugs seven inches on either side of the center of gravity, or a single lug 180 degrees removed at the center of gravity.

A cluster of four M70's is formed by using the Cluster Adapter M22.


Remarks: On impact, the fuze functions instantaneously, setting off the burster charge, which explodes the bomb and scatters the main filling.

The M70 can also be filled with white phosphorus, or with IM or NP incendiary mixture.





10-pound Smoke M77

Overall length: 19.5 inches
Body length: 19.5 inches
Body diameter: 2.9 inches

Filling: HC
Weight of filling: 9.5 pounds
Total weight: 13 pounds
Charge/weight: 73%


Construction: The body is a sheet-steel case extending the entire length of the bomb.  The tail cup fits into the after end of the casing, having a dome housing the Fuze M4.  The bomb does not have a device for stabilization in flight; therefore, an all-ways fuze is employed.

Operation: As the bombs are released from the cluster from the cluster, the arming pin is forced out by its spring, permitting the safety pin to enter the cavity in the striker.  Impact forces the striker and sleeve together, piercing the primer, which in turn ignites the first fire mixture and subsequently the H.C. smoke mixture.  The heat generated by the burning of the first mixture and the H.C. smoke mixture melts the zinc-alloy fuze body.  The smoke is then emitted through the fuze hole in the tail cup.


Remarks: Once the arming pin jumps out, the fuze is armed, and any attempt to reinsert the pin may cause the fuze to function.

Next Time: Chemical, Incendiary, Smoke - "MK" Series Bombs

American Projectiles and Explosives - Explosive Bombs - "M" Series (Part 2)

American Projectiles and Explosives



Explosive Bombs

30-pound Frag. M5 (Obsolete)

No picture available

Overall length: 25.5 inches
Body length: 13.05 inches
Body diameter: 4.2 inches
Wall thickness: 0.6 inches
Tail width: 6.5 inches

Type of filling: TNT
Weight of filling: 4.66 pounds
Total weight: 29.8 pounds
Charge/weight ratio: 16.3%
Fuzing: Mk XIV

Body Construction: The body consists of a seamless steeel tube over which are fitted rings cut from cast-steel pipe.  Cast-steel nose and base pieces thread onto this center tube.


Suspension: The bombs may be suspended horizontally, vertically, or in a cluster.  U-shaped eyebolts are welded to the bomb at the center of gravity and to the rear of the tail.  Later issues of bombs were in the Cluster M3, which contained six 30-pound Frag. Bombs, M5.


Tail construction: Four rectangular sheet-steel vanes are welded to a length of one-inch cast-iron pipe that screws into the base filling plug.

2,000-pound S.A.P. M103

Overall length: 89.29 inches
Body length: 68.5 inches
Body diameter: 18.63 inches
Wall thickness: 1.3 inches
Tail length: 25.6 inches
Tail width: 25.8 inches
Tail weight: 52.7 pounds

Type of filling: Picratol
Weight of filling: 556 pounds
Total weight: 2039 pounds
Charge/weight ratio: 27%

Fuzing: Unlike smaller S.A.P. bombs, the M103 has a solid nose, permitting tail fuzing only.


Construction: The body of the M103 is fabricated from seamless steel tubing, somewhat streamlined in shape and with a semi-pointed nose.  No provision is made for nose fuzing in this bomb.  Suspension lugs are welded tot he case in a manner similar to the G.P. bombs.  Trunnions on a band may be fitted for dive-bombing.  A box-type tail is employed as on the G.P. bombs.


Filling: Picratol, a mixture of 52% Explosive "D" and 48% TNT, is poured as the main charge, with a wax pad in the nose to cushion the explosive against premature detonation on impact with a hard target.


Remarks: The suspension lugs are 30 inches apart.  Suspension bands are under development and will be issued, when available, for installations requiring 14-inch suspension.

4-pound Frag. "Butterfly" M83

Overall length: 3 inches
Body length: 3 inches
Body diameter: 3.1 inches
Wall thickness: 0.25 inches

Type of filling: TNT
Weight of filling: 0.47 pounds
Total weight: 3.2 pounds
Charge/weight ratio: 15%

Fuzing: M129 Air or Ground burst, M130 Time, maximum 30 minutes, or M131 Anti-Disturbance.

Body Construction: The bomb body is cylindrical in shape, cast in two halves and welded together.  The fuze cavity is situated athwart-ships in the body, is 1 and 3/4 inches in diameter, and is threaded with a left-hand thread.  The left-hand thread is to prevent unscrewing of the fuze while the bomb is in flight.


Arming vane assembly: The vane assembly consists of four pieces hinged together - two semi-cylindrical surfaces (wings) and two discs (propeller blades) inclined at a slight angle.  While the bomb is still in the cluster, the vane assembly is folded around the bomb to form a cylindrical casing which can be closed against the pressure of the vane coil springs by means of a safety clip.  The arming spindle projects through the bomb casing.

When the bombs are packed in the cluster adapter, the safety clips are removed by the bombs remain in their closed status because of their proximity to each other.  When the cluster adapter bursts open, the bombs scatter and the vane assembly on each bomb is spread open by the force of its coil springs.  The vane assembly is forced by air resistance to the top of the arming spindle, where the square head on the spindle engages the square hole in the assembly.  The two wings reduce the velocity of descent of the bomb.  The two propellers, being set at angles to each other, case the vane assembly to turn in a counterclockwise direction, thereby screwing the arming spindle out of the fuze body and permitting the fuze to arm.  The arming spindle is not completely withdrawn from the fuze, being retained in the fuze by a collar on the spindle.


Markings: The bombs are painted olive drab, with a half-inch yellow band running horizontally around the folded wings.

90-pound Frag. M82

Overall length: 28 inches
Body length: 19.8 inches
Body diameter: 6 inches
Wall thickness: 0.94 inches
Tail length: 9.3 inches
Tail width: 8.1 inches
Tail weight: 2.8 inches

Type of filling: Composition B
Weight of filling: 12 pounds
Total weight: 91.6 pounds
Charge/weight ratio: 13.1%

Construction: Nose and tail pieces of cast steel screw onto a central section of seamless steel tubing.  A square helical steel spring is wound around the steel tubing.  The nose and tail pieces are partially cut through, to afford greater fragmentation.  The bomb is suspended by single lug or in a cluster (M27) of six bombs.  The tail is of normal U.S. box construction and is secured to the bomb by a locking ring.

120-pound Para-Frag. M86

Parachute container length: 35.5 inches
Diameter: 6.5 inches


Description: The M86 consists of the 90-pound Fragmentation Bomb M82, and a Parachute Unit M5 which is screwed to the base of the bomb body in place of the normal tail fin assembly.  Both units are issued separately and must be assembled prior to use.

The Parachute Unit M5 consists of a cylindrical container housing the parachute.  The lid of the container is fastened by a latch, which is secured by the arming wire.

The bomb is fuzed with the Fuze AN-M120 or AN-M120A1 by using the Adapter Booster M117.

Suspension: The bomb can be used ina  bomb station having the clearance of a 500-pound bomb, and may be suspended singly or as a two-bomb cluster with the Cluster Adapter M12.  One suspension lug is welded to the bomb at the center of gravity, and two suspension bands are issued with the parachute unit.  The larger-diameter band is secured on the parachute unit to be used in conjunction with the suspension lug or the smaller-diameter band secured on the bomb body.


Operation: Thea arming wire, which is fastened to the bomb shackle, passes through the lug of the rear suspension band and the latch on the parachute container, but not through the fuze.  This secures the latch and prevents the parachute from opening until immediately after release of the bomb.  The arming wire which passes through the fuze is fastened to the parachute by the arming cord.

On release, the arming wire is withdrawn from the latch on the container.  As the bomb falls, the air stream removes the lid from the container and allows the parachute to open.  The arming cord is attached ot the shroud line and is pulled as the parachute opens, thereby permitting the fuze to arm.

Fragmentation Bomb Clusters

M1 - Adapter M1

100-pound size for six 20-pound Frag. Bombs AN-M41.  It is 46.75 inches long and weighs 125 pounds.  It has lugs for double-hook suspension only.  The release mechanism operates by means of a cartridge and firing mechanism.



M27 - Adapter M14

500-pound size cluster for six 90-pound Frag. Bombs M82.  The adapter consists of two longitudinal steel tubes, 56 inches long, to which are welded four steel plates forming the support for the six bombs.  The lower tube serves as the backbone of the cluster; and the upper tube carries the suspension lugs, the buckles for the releasing straps, and the adapters for the nose and tail fuzes.  The Nose Fuze M111A2 or M155 is used; however, there is no mechanical time fuze in the tail.

The cluster may be adjusted to release the bombs immediately or, through the use of mechanical time fuzes, to discharge the bombs 5 to 92 seconds after the release of the cluster from the plane.  If it is intended that the cluster is to open immediately, the shear wire is cut after the arming wire is installed, and no fuze is used.  The immediate opening of the cluster produces the most favorable impact pattern.  The cluster must open at a minimum altitude of 1,000 feet in order that the bomb fuze may arm.

M28 - Adapter M15A1

100-pound size for twenty-four 4-pound Frag. Bombs M83.  It is a cylindrical sheet-metal case, which opens longitudinally, being hinged at the rear and closed by a nose cup.  It is 47.35 inches long and 8 inches in diameter, and weighs 155 pounds loaded.  It uses Fuze M155 or AN-M146.

These clusters are released from altitudes of not less than 3,000 feet and not more than 5,000 feet.  Fuze settings for function after release are varied from five seconds at minimum release altitude to eight seconds at maximum release altitude.  When the fuze fires, it releases the nose closing cup, allowing the adapter to open and release the bombs.  The bombs scatter to form a pattern over an area of approximately 300 by 200 feet.

M28A1 - Adapter M15A1

The Cluster M28A1 is the same as the M28, except that it incorporates a spoiler ring around the nose and a drag plate secured ot the tail by four screws.  These two devices were added because the dropping altitude for the M28 was limited by the high velocity attained by the clusters at high altitudes, resulting in damage to the butterfly when the cluster opened.  When drag plates and spoiler rings are used, the recommended release altitude is 1,500 feet with a six-second fuze setting, or any high altitude which will open the cluster at a height between 1,000 to 2,5000 feet.

M28A2 - Adapter M15A2

This A2 modification has a new locking cup, which is secured to the adapter by two slotted screws.  Otherwise, it is the same.

M29 - Adapter M16A1

500-pound size for 90 4-pound Frag. Bombs M83.  The container is like the M15, except for size.  In the Adapter M16, the bombs are loaded in "wafer" assemblies.  This cluster has a third single lug for British suspension.

M29A1 - Adapter M16A2

This A1 modification has the new locking cap, secured to the adapter by two slotted screws.  Otherwise, it is the same.

Remarks

For Navy usage, the Bureau of Ordnance recommends that the case-locking bushing it has developed be used with all "Butterfly" fragmentation clusters, including the M28, M28A1, M28A2, M29, and M29A1.  One end of the bushing screws into the fuze adapter, and the other end is threaded internally to receive the fuze.  The locking cup is retained positively by a safety wire which passes through a hole in the locking-cup tab and around a cotter pin placed int he bushing.  When the fuze fires, the locking cup is blown into the cluster, shearing the loops of safety wire and allowing the adapter to open.

Next Time: Navy "MK" Series (Part 1)

British Explosive Ordnance - Cluster Projectiles Part 2

British Explosive Ordnance

Cluster Projectile 500lb No.14 Mk I (Service)

Contents: One hundred and six 4lb incendiary bombs
Overall length: 67 inches
Body diameter: 14 inches
Tail length: 21 inches
Tail diameter: 14 inches
Total weight: 450 pounds

Fuzing: Nose Fuze No.42 Mk IV
Tail No.: No.42 Mk I
  

Color and markings: Dull red overall, one of the tensioning straps painted bright red

  

Description: The cluster comprises two fagots of 53 bombs each.  The bombs in the two fagots are arranged nose-to-tail, and with their safety plungers inwards so that hey are all depressed.  The bombs are held in place by a front end plate and a rear end plate, a top beam and a bottom beam, four wooden slats, tensioning straps, and a retaining bar having lateral pins which engage tabs on the tensioning straps.  A shear wire passes through a bridge and the retaining bar at a position near the rear end plate.  A channel, secured to the rear end plate, supports a fuze adapter, the outer end of which is closed by a transit plug fitted with a leather washer.  Inside the adapter is a piston through which a pin is arranged to engage the lower end of a pivoted lever.  The fuze adapter and the piston are slotted to receive the lever.  The upper end of the lever is forked and is connected to the retaining bar.  The rear end plate has two dowels for locating the tail in position, and a nut welded to the center of the rear end plate to receive one end of a tail tie rod when the tail unit is fitted to the cluster.  A nose cover is fitted to the front end plate to decrease the drag of the cluster.
 

Tail Construction: The Tail Unit No.42 Mk I is a shortened drum-type tail, having a tail cone to which a tail ring is secured by fins.  At the base of the tail cone are two holes to fit over the dowels on the rear end plate of the cluster.  The tail unit is fitted with a bearing for an arming spindle, so that, if it should ever be required to fuze the cluster with an air armed fuze, a suitable arming spindle with an arming vane could be readily fitted.  Also, to provide against this contingency, a bracket to receive a safety wire is welded to the tail cone and a hole passes through a projection on the support for the arming-spindle bearings.  A tie rod passes through the center of the tail, and one end of the rod is screw threaded to go into the central nut of the rear end plate.  Two windows, one of which is open, are provided in the tail cone.  The open window is provided so that when the cluster is prepared for use, the fuzing link, connected to the pull percussion mechanism of the Fuze No.42 Mk IV, can be passed through it and connected to the fuzing unit of the bomb carrier.


Functioning: When a cluster is released from an aircraft, the fuze functions, and after a period of delay during which the cluster projectile falls freely, the fuze magazine charge is fired.  The products of combustion of the magazine charge force the piston in the fuze adapter against the lower end of the pivoted lever, which is thus rocked about its pivot and exerts a pull on the retaining bar to break its shear wire, and to move so that the pins on the bar disengage the tabs on the tensioning straps.  The straps then fly outwards and the cluster disintegrates, the component parts failing away separately.  The individual 4lb bombs function on impact.


Suspension: A British type suspension lug is fitted to the top beam, and tapped holes in the beam are provided for fitting American type lugs.

 

Cluster Projectile 750lb No.15 Mk I (Service)
   

Contents: One hundred and fifty eight 4lb incendiary bombs
Overall length: 67 inches
Body diameter: 17.3 inches
Tail length: 21 inches
Tail diameter: 17.8 inches
Total weight: 668 pounds

Fuzing: Nose Fuze No. 42 Mk IV
Tail No.: No.42 Mk I

  

Color and markings: Dull red overall, one tensioning strap painted bright red

  

Description: This cluster comprises two fagots of 79 bombs each.  The bombs in each fagot are arranged nose-to-tail with their safety plungers inwards so that they are all depressed.  The bombs are held in place by a front end plate and a rear end plate, a top beam and a bottom beam, four wooden slats, tensioning straps, and a retaining bar having lateral pins which engage tabs in the tensioning straps.  A shear wire passes through a bridge and the retaining bar at a position near the end plate.  A channel secured to the rear end plate supports a fuze adapter, the outer end of which is closed by a transit plug fitted with a leather washer.  Inside the adapter is a piston through which is a pin arranged to engage the lower end of a pivoted lever.  The fuze adapter and the piston are slotted to receive the level.  The upper end of the lever is forked and is connected to the retaining bar.  The rear end plate has two dowels for locating the tail in position, and a nut welded to the center of the rear end plate to receive one end of a tail tie rod when the tail unit is fitted to the cluster.  A nose cover is fitted to the front end plate to decrease the drag of the cluster.


Tail Construction: The Tail Unit No.42 Mk I is a shortened drum-type tail, having a tail cone to which a tail strut is secured by fins.  At the base of the tail cone are two holes designed to fit over the dowels on the rear end plate of the cluster.  The tail unit is fitted with a bearing for an arming spindle so that, if it should ever be required to fuze the cluster with an air armed fuze, a suitable arming spindle with an arming vane could be readily fitted.  Two windows, one of which is open, are provided in the tail cone.  The open window is provided so that, when the cluster is prepared for use, the fuzing link connected to the pull-percussion mechanism of the Fuze No.42 Mk IV can be passes through it and be connected to the fuzing unit of the bomb carrier.


Functioning: When a fuzed cluster projectile is released, the fuze functions, and, after a delay during which the cluster projectile falls freely, the fuze magazine charge is fired.  The products of combustion of the magazine charge force the piston in the fuze adapter against the lower end of the pivoted lever, which is thus rocked about its pivot and exerts a pull on the retaining bar of the cluster.  This causes the retaining bar to break its shear wire and to be moved so that the pins on the bar disengage the taps on the tensioning straps.  The straps then fly outwards and the cluster disintegrates, the component parts falling away separately.  The individual 4lb bombs function on impact.


Suspension: A British type suspension lug is fitted to the top beam, and tapped holes in the beam are provided for fitting American type lugs.

Cluster Projectiles 1,000lb No.16 Mk II (Service)
  

Contents: Two hundred and thirty five 4lb incendiary bombs
Overall length: 73.5 inches (approx.)
Body diameter: 18 inches (approx.)
Total weight: 935 pounds 

Fuzing: Nose Fuze No. 42 Mk IV
Tail No.: No.48 Mks II and III

  

Color and markings: Dull red overall, one tensioning strap painted bright red

  

Description: This cluster consists of three fagots of 4lb incendiary bombs.  The bombs in each fagot are arranged nose-to-tail with their safety plungers inwards so that they are all depressed.  The bombs are held in place by a front end plate, a rear end plate, a top and bottom beam, four wooden slats, tensioning straps, and a retaining bar.  The retaining bar has a series of lateral pins which engage tabs on the tensioning straps.  A shear wire passes through a bridge and the retaining bar at a position near the front end plate.  A channel secured to the rear end plate supports a fuze adapter, the outer end of which is closed by a transit plug fitted with a leather washer.  Inside the adapter is a piston, through which a pin is passed, arranged to engage the lower end of a pivoted lever.  The fuze adapter and the piston are slotted to receive the level.  The upper end of the lever is forked and is connected to the retaining bar.  A nose cover is fitted to the front end plate to decrease the drag of the cluster.  The tail unit is attached to a spring-loaded rod extending through the center of the cluster.  the tail is held compressed against the spring by an arming wire arrangement.


Tail Construction: The Tail No.48 Mk II and III is of the telescopic type and is supplied fitted to the cluster in the closed position.  It consists of five fairings, forming a shortened cone, carried by the rear end plate of the cluster, and a strut mounted on supports, carried by an inner tube which slides in an intermediate tube.  The intermediate tube extends through the whole length of the outer tube, which is secured to the end plate of the cluster.  The intermediate tube replaces the central bomb of the middle and tail-end fagot of the cluster.

A spring is housed in the inner tube, with one end bearing against a stop in the tube and the other end bearing against a cap which closes the inner end of the intermediate tube.  The spring, which is under compression, tends to slide the inner tube out of the intermediate tube to extend the tail.  This movement is limited by a ferrule on the inner tube, which engages a ferrule in the intermediate tube when the tail is fully extended.

The inner and intermediate tubes have holes provided in them, which register when the tail is closed.  A safety wire is threaded through the holes to retain the tail in its closed position against the action of the spring.  A 4-ft fuzing lanyard is attached to the eye of the safety wire by a shackle, and a similar shackle is provided at the free end of the lanyard.


Functioning: When a fuzed cluster projectile is released from the plane, the arming wire is withdrawn, starting the delay of the fuze and releasing the tail unit, which then springs out on its rod to the fully extended position.  When the fuze functions, the fuze magazine charge is fired and the pressure of the gases forces the piston in the fuze adapter against the lower end of the pivoted lever.  The lever is thus rocked about on its pivot and exerts a pull on the retaining bar of the cluster.  This causes the retaining bar to break its shear wire and to be moved so that the pins on the bar disengage themselves from the tabs of the tensioning straps.  The straps then fly outward, and the cluster disintegrates, scattering the bombs, which fall away separately.  The individual incendiary bombs function on impact.


Suspension: A British type suspension lug is fitted to the top beam, and tapped holes in the beam are provided for fitting American type lugs.


Remarks: The fagot at the nose end of the cluster contains 79 bombs.  The central and tail fagot contains 78 bombs each, the central bomb of each of these fagots being removed to allow insertion of the outer tube, which accommodates the stem of the tail and is secured to the rear end plate of the cluster.

 

Cluster Projectile 500lb No.17 Mk II (Service)

Contents: Twenty six 20lb fragmentation bombs, specially designed for use in this cluster
Overall length: 63 inches (with blunt nose)
Width across flats: 15 inches (octagonal in shape)
Tail length: 27 inches
Total diameter: 17.5 inches
Total weight: 582 pounds 

Fuzing: Tail Fuze No.885 Mk I
Tail No.: No.63 Mks I and II

  

Color and markings: Dark green overall

  

Description: The cluster comprises twenty-six 20lb fragmentation bombs arranged in two fagots of thirteen bombs each.  The bombs are held in place by a front end palte and a rear end plate, a top beam and a bottom beam, side plates, which overlap each other, and tensioning straps and a retaining bar, which hold the components together.  The bombs are completely enclosed.  Lateral pins on the retaining bar engage tabs forming part of shoes attached to the ends of the tensioning straps.  A shear wire passes through the retaining bar and a bridge on the top beam.  A channel secured to the rear end plate supports a fuze adapter, the outer end of which is closed by a transit plug and leather washer.  Inside the adapter is a piston through which is a pin to engage the lower end of a pivoted lever.  The fuze adapter and piston are slotted to receive the lower end of the lever.  The lever passes into the fuze adapter.  Links connect the upper end of the lever to a downwardly projecting plate, welded to the retaining bar.  The rear end plate has two dowels for locating the tail in position, and a nut welded to the center of the plate to receive one end of a tail tie rod, when the tail unit is fitted to the cluster.  The front end plate has two dowels for locating either a blunt nose fairing or a streamlined nose fairing in position, and a nut welded to the center of the plate to receive the securing stud of the blunt nose fairing, or the tie rod of the streamlined fairing.  The blunt nose fairing is fitted to the cluster if it is to be carried internally in an aircraft.  The streamlined nose fairing consists of a hollow metal dome, the base of which is partly covered by an end plate welded to the dome, and is to be fitted to the cluster when carried externally on an aircraft.


Tail Construction: The Tail Unit No.63 Mk I consists of a tail cone, having an approximately octagonal base and a tail strut secured to the cone by six supports.  The tail unit has an arming spindle mounted in bearings, and has a fork at its inner end and an arming vane at its outer end.  Two inspection windows in the tail cone are provided to enable the armorer to watch the fork of the arming spindle, when fitting the tail unit to a cluster fuzed with a Tail Fuze No.855.  The Tail No.63 Mk I is only used when the cluster is carried internally in an aircraft.  The Tail No.63 Mk II is similar to the Mk I, except that it is generally strengthened and has seven tail drum supports as compared with the six of the Tail No.63 Mk I, and is to be used when the cluster is carried externally on the aircraft.


Functioning: When the fuzed cluster projectile is released, the fuze functions, and, after a period of delay during which the cluster falls freely, the fuze magazine is fired.  The products of combustion of the magazine charge force the piston in the fuze adapter against the lower end of the pivoted lever, which is thus rocked about its pivot and exerts a pull on the retaining bar of the cluster.  The pull breaks the shear wire passing through the retaining bar and moves the bar so that its pins disengage the tabs on the tensioning straps.  The straps then fly outwards and the cluster disintegrates.  Its component parts fall away separately and the individual bombs descend, supported by their parachute, to function in the normal manner.


Suspension: A British type suspension lug is fitted to the top beam, and tapped holes in the top beam are provided for fitting American type lugs.

Cluster Projectile 350lb No.23 Mk I, and 500lb No.24 Mk I (Service)

  
350lb No.23 Mk I

Contents: Fourteen modified US 20lb fragmentation bombs
Overall length: 62.25 inches
Body diameter: 11.1 inches
Tail length: 27.5 inches
Tail diameter: 12.6 inches
Total weight: 335 pounds 

Fuzing: Tail Fuze No.885 Mk I
Tail No.: No.65 Mk I

500lb No.24 Mk I

Contents: Twenty modified US 20lb fragmentation bombs
Overall length (blunt nose): 62.25 inches
Overall length (streamlined nose): 71.75 inches
Body diameter: 14.5 inches
Tail length: 30.5 inches
Tail diameter: 18 inches
Total weight: 467 pounds 

Fuzing: Tail Fuze No.885 Mk I
Tail No.: No.66 Mk I

  

Color and markings: Dark green overall, one tensioning strap painted red.

  

Description: These clusters are identical in construction, and function in a similar manner.  The Cluster No.23 Mk I, however, is approximately hexagonal in cross-section, while the No.24 Mk I is roughly octagonal.


The bombs forming the cluster are retained in two fagots of 7 bombs each in the No.23 and 10 bombs each in the No.24 by means of top and bottom beams, front and rear end plates, side fairing, and four tensioning straps.  The tensioning straps are held in position by lateral pegs on the release rod, which is carried on the top beam.  The release rod is connected to a lever and piston mechanism, the cylinder of which also forms an adapter for the barometric fuze and is located on the rear end plate.  Before the fuze is fitted, the adapter is closed by a washered plug.

The cluster is converted into an amiable cluster by the addition of a blunt nose fairing and a drum-type tail.  A special streamlined nose fairing is designed only for the Cluster No.24 Mk I, when it is to be stowed externally on the aircraft.

Tail Construction: The Tail Unit No.66 Mk I of the Cluster No.24 consists of a tail cone having an approximately octagonal base to which a circular strut is attached by seven tail fins.  The cone is fitted with the conventional arming assembly consisting of arming vanes, arming spindle, and an arming fork.  The tail is fastened to the cluster by a tie rod, and has two dowel holes in its base to position it.  The cone is fitted with two inspection windows.

The Tail Unit No.65 Mk I is similar to the No.66 Mk I except that it has a hexagonal base, and only six tail pins.


Functioning: On release from the aircraft, the cluster falls until the fuze functions.  The explosion in the magazine forces the piston forward in its housing and causes a rocking movement of the pivoted lever.  The sudden movement of the lever exerts a pull on the retaining bar and breaks the shear wire, disengaging the lateral pins from the tabs of the tensioning straps.  The straps are thus released and fly outwards, releasing the bombs.


Suspension: A British type suspension lug is fitted to the top beam, and two crutching pads bolted to the beam are used when a British type bomb carrier is fitted to the cluster.  Two sets of four tapped holes are provided in the top beam for the attachment of American type suspension lugs.  Two of the four holes at the nose end of the beam normally house the bolts securing one of the crutching pads to the beam.  If American type lugs are fitted, the British type lug and crutching pads must first be removed.

Nose Ejection Clusters

  

General Information: Experts have long strived to obtain a better type of cluster projectile, because of the inherent problems of aiming accuracy, dispersion of contents, weight factor, etc., presented by this type of ordnance.  The British believe that the solution to the search lies in the use of the Nose Ejection type cluster described herein, or its successor as modified by further research.

Nose ejection clusters were put into production near the end of World War II.  The information presented here is a generalized summary of nose ejection clusters, due to the fact that many of the individual clusters of this type are still in the developmental stage. 

  

General Requirements: The fundamental requirement of any cluster is to provide a means of placing cluster contents effectively on the target, the effectiveness being regarded broadly as a function of the angle and velocity of strike, functioning of fuzes or strikers, density of pattern, and accuracy of aim.  Complementary requirements of equal importance are that the cluster shall provide an economical aircraft bomb load, that its preparation for use shall be simple and speedy, that it will withstand road, rail, and ship transport without endangering its safety or usefulness, and that it will meet the strength requirements specified for carriage of bombs in British and American aircraft.

The type of nose ejection cluster now being developed and in production goes far towards meeting these requirements in a simple and direct manner.  It is not possible to generalize on the stability of nose ejection clusters as a group, since this depends on weight and dimensional characteristics, which are mainly due to the type of cluster contents carried.  Ballistic stability resulting in an aiming error of between 2 and 6 mils is being obtained, and will be improved upon as the development of folding and telescopic tails progresses.

The effectiveness of cluster contents from nose ejection clusters is largely fortuitous.  It appears to depend mainly on the inherent stability of the cluster contents and the parent cluster, although the velocity and height of disintegration of the cluster has some bearing.  Control of cluster velocity at disintegration is a problem now being explored.  Earlier investigation showed that decreased velocity at disintegration is invariably accompanied by a closing in of the scatter pattern, and much work on the control of the scatter pattern remains to be done.

Increasing the size of scatter patterns by means of attachments to the cluster contents and asymmetric parasheets is being investigated, but the results so far obtained, though promising, do not justify immediate embodiment.
 


Body Construction: The cluster body consists of a cylindrical steel shell made from 10- or 12-gauge steel plate, and is closed at the rear end by a steel plate of similar gauge, which is welded in position.  Two fuze pockets, which are deep enough to accommodate the burster ejectors, are attached to the end plate, which also embodies a centrally tapped hole for attaching the cluster tail.  A test plug, by which air pressure is applied at the filling factory to check that the rubber sealing joints in the nose are properly tight, is also provided in this plate.  The end plate is shaped to form a shallow truncated cone, the sloping surface of which locates the tail centrally on the cluster body.  The nose end of the cluster is closed by an iron casting secured in place by a number of screws.  On the inside of the casting is an internal steel squash plate secured by a central screw.  Its purpose is to compress the rubber sealing ring against the internal surface of the cluster body to exclude air.  A knife is attached at the front end of the cluster for the purpose of cutting the steel straps as the fagot of cluster contents is ejected.  A pressure plate is assembled in the cluster behind the fagot of cluster contents.  Suspension lugs for British and American type bomb stowage are permanently attached to the cluster body.

The cluster is designed, manufactured, and tested to withstand the climatic conditions experienced in the Far East.  After assembly at the filling factory, the rubber sealing joints in the nose and under the knife fixing screws are tested for tightness by an air-pressure test.


Tail Construction: Two types of cluster tail are in use, the conventional type with a tail cone and cylindrical strut, and one having collapsible fins, which is used where the space available is too small to permit the use of a norm-type tail.  Twin arming mechanisms are locked by means of fuzing wires engaging holes in the arming vanes.  Windows are provided through which the fuze can be observed as the tail is assembled to the cluster.  The tail is located on the tapered end plate of the cluster body, and is secured by a single central bolt.  It is designed, manufactured, and boxed for use in tropical climates.


Transit Bases: To prevent the cluster from sustaining damage affecting the safety of its contents, or destroying the hermetic seal in the nose, each cluster is fitted with transit bases which are intended to remain in position until the cluster is prepared for use.

The transit bases consist of two light-gauge steel rings filled with a material designed to withstand shock loads resulting from rough handling, and also to distribute the load over a large area of the cluster and so prevent damage to the nose seal, which would inevitably result from a blow concentrated at any one point on the nose cover.  The material used in the Mk I design is a resin-bonded sawdust, which is light in weight and resistant to tropical climatic conditions, fungi and insect growth, etc.  The bases are fitted one at each end of the cluster, and secured by tie rods, which embody a quick release device designed to enable the bases to be removed in a minimum of time.


Fuzing: One fuze and burster only are necessary to disintegrate the cluster, but two of each are used as an insurance against complete failure.  Clusters containing 4lb I.B.'s are fuzed with two Tail Fuzes No.42 Mk IV, while all others use two Barometric Tail Fuzes No.886.


Burster Ejectors: Ejection of the cluster contents in effected by a burster ejector, which is ignited by the cluster fuze.  The bursters are placed in the cluster at the time of fuzing.  There are two types of burster, the No.6 Mk I containing 70 grams of G.20 powder for large clusters and the No.7 Mk I containing 50 grams of G.20 powder for the smaller clusters.  The powder is contained in a plastic cylinder manufactured from a polyvinal chloride.  This material is fully resistant to tropical conditions and does not affect the gunpowder.  The cylinders are provided with two small extrusions by which they can be removed from the cluster if required.

For transport and storage the bursters are packed two or four (according to suze) in a sealed metal cylinder, 18 of which are packed in one wooden box.  The metal cylinders are opened by means of a tear-off metal strip.


Contents: The cluster contents are assembled in two or more banks of bombs, with light-gauge steel end plates and longitudinal steel struts, to form a fagot, which is firmly secured by a number of circumferential steel straps.  When properly assembled to a fagot, the cluster contents are safe and the fuzes cannot arm accidentally.  Damage to components of the cluster contents by the force of the ejector charge is prevented by the steel struts, which transmit the force of the explosion from the pressure plate directly to the nose cover, and not through the bombs themselves.


Functioning: On release from the aircraft, the fuzing lanyards are withdrawn from the fuzes and from the air arming vanes.  When a folding tail is used, the lanyard is also withdrawn from the retaining device to allow the tail to assume an expanded position.  At a predetermined height the fuzes operate and ignite the burster.  The expanding gases from the burster drive the fagot of contents forward.  As the fagot passes the cutting edge of the knife, the steel straps binding the cluster are severed, and the screws holding the cluster noose in place are broken.  The contents are then fully ejected.


Developmental Priority: The following is a list of nose ejection clusters in order of their development priority.  The first six items were cleared for production on 7 July, 1945.

Cluster N.E., ANM 69 I.B., 500lb. Mks I & II
Cluster N.E., 18-lb Mg. I.B., 800lb. Mk I
Cluster N.E., J 20-lb I.B., 800lb. Mk I
Cluster N.E., ANM 40 H.E., 600lb. Mk I
Cluster N.E., ANM 40 H.E., 350lb. Mk I
Cluster N.E., F. 8-lb H.E., 550lb. Mk I
Cluster N.E., F. 8-lb H.E., 350lb. Mk I
Cluster N.E., F. 8-lb H.E., 1,000lb. Mk I
Cluster N.E., ANM 69 I.B., 550lb. Mk III
Cluster N.E., 4-lb I.B., 800lb. Mk I
Cluster N.E., J. 30-lb I.B., 500lb. Mk I
Cluster N.E., 4-lb I.B., 500lb. Mk I
Cluster N.E., 4-lb I.B., 950lb. Mk I
Cluster N.E., ANM 69 I.B., 1,000lb. Mk I
Cluster N.E., 3-lb I.B., 1,000lb. Mk I

Next Time: High Explosive Rockets Part 1