No. 106 Fuze
Encyclopedia
Number 106 Fuze was the first British instantaneous percussion artillery fuze
, first tested in action in late 1916 and deployed in volume in early 1917.
and 18-pounder
), intended to burst above head-height for anti-personnel use. British heavy artillery was expected to attack fortifications, requiring high-explosive shells to penetrate the target to some extent before exploding. Hence British artilley fuzes were optimised for these functions. Experience of trench warfare on the Western front
in 1914–1916 indicated that British artillery was unable to reliably destroy barbed-wire barricades, which required shells to explode instantaneously on contact with the wire or ground surface: British high-explosive shells would penetrate the ground before exploding, rendering them useless for destroying surface targets.
British No. 100 and later No. 101, 102 and 103 nose "graze" fuzes available in the field from August 1915 onwards could explode a high-explosive shell very quickly on experiencing a major change in direction or velocity, but were not "instantaneous": there was still some delay in activation, and also had limited sensitivity: they could not detect contact with a frail object like barbed wire or soft ground surface. Hence they would penetrate objects or ground slightly before detonating, instead of above ground as required for wire cutting. These graze and impact fuzes continued to be used as intended for medium and heavy artillery high-explosive shells.
Up to and including the Battle of the Somme in 1916, British forces relied on shrapnel shells fired by 18-pounder field guns
and spherical high-explosive bombs fired by 2-inch "plum-pudding" mortars
for cutting barbed-wire defences. The disadvantage of shrapnel for this purpose was that it relied on extreme accuracy on setting the fuze timing to burst the shell close to the ground just in front of the wire: if the shell burst fractionally too short or too long it could not cut the wire, and also the spherical shrapnel balls were not of an optimal shape for cutting strands of wire. While the 2-inch mortar bombs cut wire effectively, their maximum range of 570 yard limited their usefulness.
The steel hammer had a softer aluminium cap which absorbed the force of a glancing blow and prevented the spindle from bending or breaking, hence reducing the risk of misfire.
, hence activating the fuze. Hence usage of this fuze in action was characterised by British troops in the front lines noticing the descending tapes detached from the fuzes as they travelled overhead towards the enemy lines.
After the tape detached during flight, the hammer was prevented from being forced inward by air resistance by a thin "shearing wire" passing through the hammer spindle, which was easily broken by the hammer encountering any physical resistance. The spindle was prevented from rotating relative to the fuze body in flight, and hence from snapping the shearing wire, by a guide pin passing through a cutout in the spindle.
Later versions (designated "E") incorporated an additional safety mechanism: an internal "shutter", also activated by rotation of the shell after firing, which closed the channel between the striker in the nose and the powder magazine in the base until it was clear of the gun which fired it. On firing, the shutter resisted acceleration ("setback") and the accelerating shell body pushed against it, preventing the shutter from moving. When acceleration ceased shortly after the shell left the gun barrel, the shutter ceased to "set back" and was free to spin outwards, activating the fuze.
The chain of events necessary to allow the fuze to activate a shell were:
On the Western Front
in 1917 and 1918, the No. 106 fuze was typically employed on high-explosive shells for cutting barbed wire, fired by 18-pounder field guns
at short to medium range, and by Mk VII and Mk XIX 6-inch field guns at long range. Its instantaneous action also made it useful for counter-battery fire: high-explosive shells fired by 60-pounder and six-inch field guns were targeted on enemy artillery, and by bursting above ground could cause maximum damage to enemy artillery, mountings and crew. It was also approved as the primary fuze for high-explosive shells for QF 4.5 inch Howitzer
s from August 1916 onward.
This fuze was also used to burst smoke shells.
There were many versions of No. 106 and it remained in service in the form of its streamlined variant No. 115 until World War II.
Artillery fuze
An artillery fuze or artillery fuse is the type of munition fuze used with artillery munitions, typically projectiles fired by guns , howitzers and mortars. A fuze is a device that initiates an explosive function in a munition, most commonly causing it to detonate or release its contents, when its...
, first tested in action in late 1916 and deployed in volume in early 1917.
Background
Britain entered World War I with a policy of using shrapnel shells for its field guns (13 pounderOrdnance QF 13 pounder
The Ordnance QF 13-pounder quick-firing field gun was the standard equipment of the British Royal Horse Artillery at the outbreak of World War I.-History:...
and 18-pounder
Ordnance QF 18 pounder
The Ordnance QF 18 pounder, or simply 18-pounder Gun, was the standard British Army field gun of the World War I era. It formed the backbone of the Royal Field Artillery during the war, and was produced in large numbers. It was also used by British and Commonwealth Forces in all the main theatres,...
), intended to burst above head-height for anti-personnel use. British heavy artillery was expected to attack fortifications, requiring high-explosive shells to penetrate the target to some extent before exploding. Hence British artilley fuzes were optimised for these functions. Experience of trench warfare on the Western front
Western Front (World War I)
Following the outbreak of World War I in 1914, the German Army opened the Western Front by first invading Luxembourg and Belgium, then gaining military control of important industrial regions in France. The tide of the advance was dramatically turned with the Battle of the Marne...
in 1914–1916 indicated that British artillery was unable to reliably destroy barbed-wire barricades, which required shells to explode instantaneously on contact with the wire or ground surface: British high-explosive shells would penetrate the ground before exploding, rendering them useless for destroying surface targets.
British No. 100 and later No. 101, 102 and 103 nose "graze" fuzes available in the field from August 1915 onwards could explode a high-explosive shell very quickly on experiencing a major change in direction or velocity, but were not "instantaneous": there was still some delay in activation, and also had limited sensitivity: they could not detect contact with a frail object like barbed wire or soft ground surface. Hence they would penetrate objects or ground slightly before detonating, instead of above ground as required for wire cutting. These graze and impact fuzes continued to be used as intended for medium and heavy artillery high-explosive shells.
Up to and including the Battle of the Somme in 1916, British forces relied on shrapnel shells fired by 18-pounder field guns
Ordnance QF 18 pounder
The Ordnance QF 18 pounder, or simply 18-pounder Gun, was the standard British Army field gun of the World War I era. It formed the backbone of the Royal Field Artillery during the war, and was produced in large numbers. It was also used by British and Commonwealth Forces in all the main theatres,...
and spherical high-explosive bombs fired by 2-inch "plum-pudding" mortars
2 inch Medium Mortar
The 2 inch Medium Trench Mortar, also known as the 2-inch Howitzer, and nicknamed the "Toffee Apple" or "Plum Pudding" mortar, was a British SBML medium trench mortar in use in World War I from mid 1915 to mid 1917...
for cutting barbed-wire defences. The disadvantage of shrapnel for this purpose was that it relied on extreme accuracy on setting the fuze timing to burst the shell close to the ground just in front of the wire: if the shell burst fractionally too short or too long it could not cut the wire, and also the spherical shrapnel balls were not of an optimal shape for cutting strands of wire. While the 2-inch mortar bombs cut wire effectively, their maximum range of 570 yard limited their usefulness.
Detonation mechanism
The Number 106 Fuze drew on French technology to provide a mechanism for reliably detonating a high-explosive shell instantaneously when the nose made physical contact with the slightest object like a strand of barbed wire or the ground surface. Hence it was a "Direct Action" rather than a "graze" fuze: simple deceleration or change of direction would not activate it, only direct physical contact between the hammer projecting from the nose and an external object. The basic mechanism was a steel hammer on the end of a spindle projecting forward from the nose of the fuze. The slightest movement inwards of this spindle caused the fuze to detonate and hence explode the shell before it penetrated the ground.The steel hammer had a softer aluminium cap which absorbed the force of a glancing blow and prevented the spindle from bending or breaking, hence reducing the risk of misfire.
Arming and safety features
The first safety mechanism was a length of brass tape wrapped around the spindle between the fuze body and the hammer head, which prevented the spindle from moving inward. On firing, the hammer's inertia caused it to "setback" fractionally i.e. it resisted acceleration, and hence the accelerating fuze body forced the tape wrapped around the spindle against the underside of the hammer head, preventing the tape from unwinding. When acceleration ceased shortly after the shell left the gun barrel, the hammer and fuze body were travelling at the same speed and the hammer ceased to "set back", freeing the tape. The shell's rotation then caused a weight on the end of the tape to unwind the tape through centrifugal forceCentrifugal force
Centrifugal force can generally be any force directed outward relative to some origin. More particularly, in classical mechanics, the centrifugal force is an outward force which arises when describing the motion of objects in a rotating reference frame...
, hence activating the fuze. Hence usage of this fuze in action was characterised by British troops in the front lines noticing the descending tapes detached from the fuzes as they travelled overhead towards the enemy lines.
After the tape detached during flight, the hammer was prevented from being forced inward by air resistance by a thin "shearing wire" passing through the hammer spindle, which was easily broken by the hammer encountering any physical resistance. The spindle was prevented from rotating relative to the fuze body in flight, and hence from snapping the shearing wire, by a guide pin passing through a cutout in the spindle.
Later versions (designated "E") incorporated an additional safety mechanism: an internal "shutter", also activated by rotation of the shell after firing, which closed the channel between the striker in the nose and the powder magazine in the base until it was clear of the gun which fired it. On firing, the shutter resisted acceleration ("setback") and the accelerating shell body pushed against it, preventing the shutter from moving. When acceleration ceased shortly after the shell left the gun barrel, the shutter ceased to "set back" and was free to spin outwards, activating the fuze.
Use in action
The fuze was first used experimentally in action in the later phases of the Battle of the Somme in late 1916, and entered service in early 1917 . From then onwards British forces had a reliable means of detonating high-explosive shells on the ground surface without merely digging holes as previously.The chain of events necessary to allow the fuze to activate a shell were:
- Gunner removes the fuze's safety cap before loading
- Fuze accelerates violently on firing: setback of hammer prevents tape from unwinding while still in or near gun barrel
- RiflingRiflingRifling is the process of making helical grooves in the barrel of a gun or firearm, which imparts a spin to a projectile around its long axis...
in gun barrel causes shell and hence fuze to spin rapidly - Fuze exits gun barrel and ceases accelerating: hammer ceases to setback, freeing up tape
- Fuze continues to spin between 1,300 and 1,700 revolutions per minute: Safety shutter spins out ("E" models from 1917 onwards)
- Centrifugal forceCentrifugal forceCentrifugal force can generally be any force directed outward relative to some origin. More particularly, in classical mechanics, the centrifugal force is an outward force which arises when describing the motion of objects in a rotating reference frame...
of weight on end of tape causes tape to unwind and detach from hammer spindle - Hammer encounters physical resistance and decelerates, causing momentum of fuze body to snap the shearing wire and force the detonator onto the pointed end of the hammer spindle
- Detonator explodes, sending flame through centre of fuze body to C.E. (Composition Exploding) magazine in fuze base
- C.E. magazine detonates, sending flame into shell nose
- Flame activates shell function, typically high-explosive or smoke
On the Western Front
Western Front (World War I)
Following the outbreak of World War I in 1914, the German Army opened the Western Front by first invading Luxembourg and Belgium, then gaining military control of important industrial regions in France. The tide of the advance was dramatically turned with the Battle of the Marne...
in 1917 and 1918, the No. 106 fuze was typically employed on high-explosive shells for cutting barbed wire, fired by 18-pounder field guns
Ordnance QF 18 pounder
The Ordnance QF 18 pounder, or simply 18-pounder Gun, was the standard British Army field gun of the World War I era. It formed the backbone of the Royal Field Artillery during the war, and was produced in large numbers. It was also used by British and Commonwealth Forces in all the main theatres,...
at short to medium range, and by Mk VII and Mk XIX 6-inch field guns at long range. Its instantaneous action also made it useful for counter-battery fire: high-explosive shells fired by 60-pounder and six-inch field guns were targeted on enemy artillery, and by bursting above ground could cause maximum damage to enemy artillery, mountings and crew. It was also approved as the primary fuze for high-explosive shells for QF 4.5 inch Howitzer
QF 4.5 inch Howitzer
The Ordnance QF 4.5 inch Howitzer was the standard British Empire field howitzer of the First World War era. It replaced the BL 5 inch Howitzer and equipped some 25% of the field artillery. It entered service in 1910 and remained in service through the interwar period and was last used in...
s from August 1916 onward.
This fuze was also used to burst smoke shells.
There were many versions of No. 106 and it remained in service in the form of its streamlined variant No. 115 until World War II.