Cutaway model of a WW1 British 40x157R 2 pdr. QF Pompom HE anti-aircraft cartridge.
The 2 pounder Pompom is a 40mm dia cartridge, most known for it’s use by the royal navy in the multiple barrel arrangement, called Pompom (after it’s sound when firing) , or “Chicago piano”.
Pompom guns were used on different mountings with 1, 2, 4 and 8 barrel configurations.
The Pompom type gun can be traced back to the Boer war, when the first pompom appeared, a 1 pounder 37mm belt fed version, in fact an oversized machinegun, used by the Boers against the British in the Boer war. The British saw the advantages of the weapon and had it taken into production by Vickers. The 1 pounder was surpassed by the 37mm 1,5 pounder, which was however soon surpassed by the 40mm 2 pounder.
All weapons are water cooled by means of a jacket around the barrel, therefore enabling it to maintain a relatively high rate of fire over a longer time. As the shells off all pompom types are relatively slow (short shellcase with relatively small powder charge), recoil is also low, so the weapon does not need a heavy carriage, making it easily transportable.
The 2 pounder QF Mark II was adopted by the royal navy as the standard anti-aircraft weapon for ships of cruiser size and below in 1915. As the fabric belt feeding appeared to be no success, it was soon replaced with a disintegrating steel belt.
The cartridge depicted here is a WW1 era cartridge, the projectile is steel made, and filled with gunpowder. It has a single red copper driving belt. It is fuzed with the pyrotechnic time fuze No.121, and has a simple impact fuze screwed into the base. This type of cartridge however was used up to WW2.
The shellcase is brass made and has filler of cordite sticks, held together by a single strand of rope.
The pyrotechnic time fuze No.121 (pict03):
The fuze is fully brass made. It consists of a brass fuze body in which a needle plug is crewed into the base. Above this needle plug a firing cap pellet is placed in an inertia weight, kept in upper position by a brass stirrup spring (painted grey) around the pellet. Upon firing, inertia moves the firing cap pellet into the needle plug Between the firing cap in the pellet and the top of the pellet, a hole is drilled that allows the flame to travel upward. Above the pellet a central hole is drilled, ending in an angular hole which ends in the fixed upper powder ring of the pyrotechnic fuze. The lower ring is the adjustable ring which is rotated to set to time. The adjustable ring has a small hole in top which allows the flame of the fixed upper pyrotechnic ring to reach the pyrotechnic ring of the lower adjustable/rotatable ring. As soon as the lower ring is burnt up, the flame travels doen into the black powder magazine, which fires a flame into the main black charge in the projectile body, exploding the projectile.
The base fuze (pict.04);
In the base of the projectile a base impact fuze is placed, enabling the projectile to explode if impact occurs before the time fuze is expired. On the BOCN forum it is claimed to be a Hotschkiss design. It consists of a brass fuze body housing a brass set back weight, kept in forward position by two outward protruding lugs on the brass firing pin, formed by punching a radial hole through the firing pin. Upon firing , the set-back weight moves backward, bending the lugs inward, thereby placing the point of the firing pin over the top of the set-back weight. Upon impact, the setback weight moves forward, pushing the firing pin into the firing cap (red). The flame of the firing cap travels through the channel above (blue) into the gun powder, exploding the projectile.
There is discussion about the colour scheme of the projectile, however, I took over the colours as found on existing projectiles:
http://www.bocn.co.uk/vbforum/threads/4365-2-pdr-Pom-Pom-HE-with-base-fuze-40x157R
I have no further info or drawings of this cartridge. However, a few months ago I found a drawing of the cartridge on the internet on an unrelated site. Stupidly enough I forgot to save it. I do remember however that it stated that the shellcase was filled with powder sticks, and the projectile was black powder filled.
I can also remember having read on another forum that some Pompom guns had an automatic fuze setter, what would come in handy when using the No.121 fuze. Another possibility would be to set the fuzes when placing the cartridges in the belts, as to form a splinter screen at a certain distance of the gun. If anybody has some more info about this subject, please let me know.
If anybody has some added info about this cartridge (as well as a drawing), please let me know.
Regards, DJH
The 2 pounder Pompom is a 40mm dia cartridge, most known for it’s use by the royal navy in the multiple barrel arrangement, called Pompom (after it’s sound when firing) , or “Chicago piano”.
Pompom guns were used on different mountings with 1, 2, 4 and 8 barrel configurations.
The Pompom type gun can be traced back to the Boer war, when the first pompom appeared, a 1 pounder 37mm belt fed version, in fact an oversized machinegun, used by the Boers against the British in the Boer war. The British saw the advantages of the weapon and had it taken into production by Vickers. The 1 pounder was surpassed by the 37mm 1,5 pounder, which was however soon surpassed by the 40mm 2 pounder.
All weapons are water cooled by means of a jacket around the barrel, therefore enabling it to maintain a relatively high rate of fire over a longer time. As the shells off all pompom types are relatively slow (short shellcase with relatively small powder charge), recoil is also low, so the weapon does not need a heavy carriage, making it easily transportable.
The 2 pounder QF Mark II was adopted by the royal navy as the standard anti-aircraft weapon for ships of cruiser size and below in 1915. As the fabric belt feeding appeared to be no success, it was soon replaced with a disintegrating steel belt.
The cartridge depicted here is a WW1 era cartridge, the projectile is steel made, and filled with gunpowder. It has a single red copper driving belt. It is fuzed with the pyrotechnic time fuze No.121, and has a simple impact fuze screwed into the base. This type of cartridge however was used up to WW2.
The shellcase is brass made and has filler of cordite sticks, held together by a single strand of rope.
The pyrotechnic time fuze No.121 (pict03):
The fuze is fully brass made. It consists of a brass fuze body in which a needle plug is crewed into the base. Above this needle plug a firing cap pellet is placed in an inertia weight, kept in upper position by a brass stirrup spring (painted grey) around the pellet. Upon firing, inertia moves the firing cap pellet into the needle plug Between the firing cap in the pellet and the top of the pellet, a hole is drilled that allows the flame to travel upward. Above the pellet a central hole is drilled, ending in an angular hole which ends in the fixed upper powder ring of the pyrotechnic fuze. The lower ring is the adjustable ring which is rotated to set to time. The adjustable ring has a small hole in top which allows the flame of the fixed upper pyrotechnic ring to reach the pyrotechnic ring of the lower adjustable/rotatable ring. As soon as the lower ring is burnt up, the flame travels doen into the black powder magazine, which fires a flame into the main black charge in the projectile body, exploding the projectile.
The base fuze (pict.04);
In the base of the projectile a base impact fuze is placed, enabling the projectile to explode if impact occurs before the time fuze is expired. On the BOCN forum it is claimed to be a Hotschkiss design. It consists of a brass fuze body housing a brass set back weight, kept in forward position by two outward protruding lugs on the brass firing pin, formed by punching a radial hole through the firing pin. Upon firing , the set-back weight moves backward, bending the lugs inward, thereby placing the point of the firing pin over the top of the set-back weight. Upon impact, the setback weight moves forward, pushing the firing pin into the firing cap (red). The flame of the firing cap travels through the channel above (blue) into the gun powder, exploding the projectile.
There is discussion about the colour scheme of the projectile, however, I took over the colours as found on existing projectiles:
http://www.bocn.co.uk/vbforum/threads/4365-2-pdr-Pom-Pom-HE-with-base-fuze-40x157R
I have no further info or drawings of this cartridge. However, a few months ago I found a drawing of the cartridge on the internet on an unrelated site. Stupidly enough I forgot to save it. I do remember however that it stated that the shellcase was filled with powder sticks, and the projectile was black powder filled.
I can also remember having read on another forum that some Pompom guns had an automatic fuze setter, what would come in handy when using the No.121 fuze. Another possibility would be to set the fuzes when placing the cartridges in the belts, as to form a splinter screen at a certain distance of the gun. If anybody has some more info about this subject, please let me know.
If anybody has some added info about this cartridge (as well as a drawing), please let me know.
Regards, DJH
