SOME FRENCH FUSES

During the post 1870 war years, that saw the Armies of the French Emperor Napoleon III being defeated by those of the young German First Reich, French military engineers developped new technolgies, particularly in the artillery rechniques, amongst them the ammunition fuses.

The old percussion fuses Desmarest (1859) and Tardy (1860) were progressively replaced by a new generation of omproved material. The principles of those new percussion systems Henriet (1874), Budin (1875), Siège et Montagne (1878), Saussier (1887) et Robin (1888), equipped with more and more reliable arming and percussion mechanisms, were afterwards used in the XXst century fuses.

The Percussion fuse of 25/38 mm System Budin, model 1875 presented here had a mobile starter-bearer, blocked in lower position by a hollow inertia block hold in place by a wavy brass blade, and separated from the top plug percussion pin by the safety spring.

At the departure of the ammo, the force threw the inertia block downwards, the brass blades were compressed and let the starter-bearer enter in it.

Thanks to that arming movement, the starter was only separated from the percussion pin by the safety spring. The arriving hit throwed that new assembly 'starter-bearer / inertia block' upwards, compressing the safety spring, and hitting the percussion pin, causing the explosion.

The head plug screw was machined with a deep middle-height breaking groove, in order to induce at that place the occasionnal breaking of the top of the fuse at the impact arrival, without risk for the fuse functionning.

When that Budin fuse was armed, a simple 50 cm fall was enough to make it explode.

Designed for Siege and Mountain ('S.M.') artillery, whose indirect (curved) shots needed variable propulsive charges, that Percussion fuse / detonator 30/45 S.M. model 1878 was built to be armed with the same security level either at high or low charge. It could also detonate at the arrival on the objective, even with low speeds.

For that reason, the inertia load was heavier, and the arming system was composite : arming staple system for lower charges, arming grooves on the starter-bearer for the higher charges.

It mainly equipped the projectiles of the

• 120 mm and above heavy howitzers
• Crapouillots trench mortars (big caliber bombs)

The original Mark 1878 evoluated in 1881 (Percussion fuse / detonator 30/45 S.M. model 1878-81) by the addition at the top of the fuse of a percussion pin-bearer plug. Later, in 1892, a second change was made (Percussion fuse / detonator 30/45 S.M. model 1878-92) with a smaller diameter plug.

A variantion of the 1878-81 mark was also built, with a cylindrical head instead of a conical one, and a stronger security spring, dedicated to the shells of the big

• 370 mm heavy mortars

For each of the 3 marks of this 'Siège et Montagne' fuse, there was differnt sizes models, in order to suit shells of different upper hole :

• 25/38 (thread 25 mm, cone base 38 mm)
• 30/45 (thread 30 mm, cone base 45 mm)
• 40/55 (thread 40 mm, cone base 55 mm)

Very sensitive, it needed very careful handling, since it could be armed only with the shock of a fall from a height of 3 to 4 meters !

Basic type of the French percussion fuses, the percussion fuse 24/31 Mle 1899 design was quite simple, and therefore robust. It was basically an evolution of the classical 22/31 use model 1888, system 'Robin' (its inventor), by the addition of a second security arming system, invented by 'Lejay'

The top steel cap was containing the additional 'Lejay' arming system (inertia block + spring + staple). The classic 'Robin' percussion system, with its own arming mechanism, was located at the centre, igniting the explosive charge of the bottom part, whose action was multiplied by the addition of a detonator, that could be itself inserted inside a powerful relay-charge.

It equipped most of the explosive projectiles of the :

• 75, 80, 90, 95, 120, 155 mm guns and howitzers

In 1908, a variant, the percussion fuse 24/31 Mle 1899-08, was adopted including a small 0.05 seconds delay, allowing the 75 mm 'ricochet' shootings (hitting alive objectives with explosive shells shot at low angle - lower than 15° - so that it rebounds on the ground and explode at low altitude).

In 1914, the French Army had soon to admit that most of the artillery fightings were made at too long a range to allow those low-angle shots. Consequently, the original 1899 fuses without delay were quickly re-adopted.

Those two marks cannot be distinguished externally, unless the original cap paint is still visible : white for the Mle 99, and black for the Mle 99-08.

The use of the preceeding percussion fuse (24/31 Mle 1899 and 1899/08) showed several disfunctions in the case of specific circumstances :

• with heavy projectiles having a high velocity at the impact, or hitting too hard surfaces, the fuse head cap with the security system could be badly damaged, and cause a misfunction of the fuse, not exploding.
• with short tubes shooting with low charges, the initial acceleration was sometimes too low to allow the arming.

This new model, Percussion fuse 24/31 Mle 1899-15, system Robin, keeps the 'Robin' percussion system of the 1899 and 1899/08 fuse, but replaces the head security system 'Lejay' with a simple cap with the percussion pin, then, in a later version, a massive head.

There was non delayed, short delay (0.05 seconds), and long delay (0.15 seconds) models. Those versions are not discernable, unless the ink markings are still present, or if the cap paint is still visible : white for non-delayed fuze, black for short delayed fuze.

This fuse equipped most of the explosive projectiles of various calibers :

• 75, 80, 90, 95, 120, 155, 220 mm guns and howitzers
• Trench bombs shot with heavy loads

Invented by Mr Peuch, this Percussion fuse 24/31 Mle 1914 was an important evolution of the 1899 model. The novative principle was a new arming inertia delayed system, based on a security piece blocked with a tin pin, that could rotate and retire sliding on a helicoïdal slope also machined on the starter-bearer.

That movement allowed the shortening of the inertia block at the shot departure, unmasking the strater therefore accessible to the percussion pin fixed on the fuse head by a plug.

That mechanism insured a quicker functionning that the one of the model 1899 fuse, generally exploding when the the shell top penetrated the ground. The embarked explosive load was a 2 grammes fulminate detonator.

That fuse usually equipped the projectiles of the

• 75, 80, 90 and 95mm field guns
• 120mm guns
• 155mm howitzers

, mostly when surface-effect explosion were wanted.

However, those fuses were not to be used with trench mortars, since the departure shock energy was not sufficient to arm the mechanism.

The fuses armed by centrifugal force used to have two main problems : there was a high risk that the spin was quickly sufficient to blow the shell still in the gun tube, at the departure, and it was also possible that, on the contrary, the spin slowers during the flight and disarms the detonator.

This Percussion Fuse model 1916, Schneider system had a security device based on inertia blocks and springs keeping safe the centrifugal arming segments during the acceleration phase (when the shell was still in the tube), and blocking them in armed condition when the spped began to be constant.

This mechanism was pretty precise, and was working well only for spin speeds over > 12000 rotations/minute. It was then very important to use them only with the famous 75mm field gun. The embarked explosive charge was a 2 grams fulminate detonator.

That fuse usually equipped the projectiles of the

• 75mm field gun

where it replaced the instantaneous fuse 24/31 Mle 1914. Two versions were developped, without delay and with 0,05 s delay. Several profiles were developped ('tracé A. 1644, 1644 B, 1644 BA, 1644 D ter, 1772, etc...

The development of the trench artillery, the famous 'Crapouillots', induced the need of new resistant materials, not too sensible to the wet and dirt conditions of the first lines. A certain Capitaine Rémondy designed this variation of the Percussion fuse / detonator 24/31.

This Percussion fuse model P.R. 1916 ('P.R.' = Peuch - Remondy) had the particularity to have no outside entry to the internal mechanisms. Once the fuse was mounted on the projectile, it was 'waterproof'.

Consequently, it was necessary that its arming mechanism was sensible enough (the departue acceleration of the mine-throwers projectiles were relatively smaller than for the conventional artillery), but also shock resistant (to allow the safe handling in the trenches) without having any safety mechanism such as safety pin or screw actionable before the shot.. This mechanism, based on the rotation of helicoïdal ramps, was winning this challenge.

That fuse usually equipped the projectiles of the

• 58 mm to 240 mm trench mortars

It has been developped in no-delay and 0,20 s delay versions. Moreover, some models with top percussion-pin bearer plug have been produced.

This Mod 1915 Schneider fuse for Schneider shells is unusual for different reasons. The diameter of its thread (47,5 / 55 mm) is specific to the 105 mm Schneider shell mod 1913, its shape and its weight are not common, and it is the only French fuse to contain a pyrotechnic security.

Located at the fuse top, under a screwed plug, the pyrotechnic security acted just like the one of many German systems : at the departure, a percussion pin hits a starter igniting a compressed black-powder grain. The disparition of this latter made free the movements of a stem that normally blocked, at rest, the heavy inertia block of the percussion system.

The percussion system was, except for the bigger dimensions, the same as the one of the 24/31 Mod 1916 system Schneider fuse (see above), with centrifugal arming. The fuse was completely closed, so the lack of any escape hole for the combustion gasses of the pyrotechnic securuty system was compensated by a inner expansion room.

This fuse equipped exclusively the high explosive Schneider shells of the

• 105 mm Schneider guns

It has been built either without any delay, or with a 'long' delay of 0,25 s.

The I.A. mod. 1915 fuse was designed to induce maximum surface effects of the explosive shells, making them explode as soon as the top of this long fuse was hitting the objective. Those fuses, designed in 1915, had to act better than the 1914 instantaneous fuse.

Therefore, those ammunitions were practically making no shell hole, and their effects on infantrymen were devastating...

The fuse I.A. Mle 1915 was armed by the means of the centrifugal force, ejecting during the flight two brass half-rings under the 'hat', those half-rings beeing blocked at rest by a tissue ribbon or a tin cover.

At the impact, the hat was actionning a rod, shearing a small safety pin, and made the percussion pin violently meet the starter, linked to the main charge by an explosive tube.

This fuse was generally equipping the shells of the

• 75 mm field guns (explosive shells)

Its use generally needed very careful handling : its good functionning was depending of the spin velocity of the shell, it was subject to accidental explosion in the gun tube in the case of brutal deceleration, and its shape was modifying the shell maximum range, that had to be corrected by means of appropriate tables.

In 1916, a new mark 'I.A.L. Mle 1916 fuse' was built. The biggest change concerned the disappearing of the explosive tube, too dangerous, for a hollow channel communicating the flame from a fulminate starter in the fuse head.

The long profile of the elongated instantaneous fuse I.A. and I.A.L. used to bring some troubles. In particular, this long piece trended to destabilize the trajectory of the shells on which it was screwed. Moreover at the arrival, if the landing was not perpendicular enough, the fuse could be bent and therefore prevent the percussion mechanism to operate properly.

This is the origin of the development of the T.C.A.L. Fuse Mle 1917, shorter, but keeping the internal principles of the I.A.L. fuse; Hera again, the arming was realized by the unscrolling of a tissue ribbon, caused by the shell spin (system 'Lefèvre'), the round percussion head was linked to a long axial percussion rod that could hit a starter, igniting the detonator.

A security pin crossing the percussion head prevented the mechanism from unwanted functionning during the flight caused by air pressure, but was sheared by the arrival shock.

That fuse equipped mainly the shells of the

• 75 mm field guns (high explosive shells)

There was a single rotation direction, and like its ancestors, it was coverd with a tin cap before the shot. It was exploding closer to the ground, but gave satisfactory results.

The 1917 and 1918 marks are impossible to discernate externally, the only difference being in the tail pyrotechnic chain (percussion pin - upper percussion starter - primary starter - detonator for the Mle 1917; percussion pin - percussion starter, detonator for the T.C.A.L. Fuse Mle and 1918).

The functionning of the instantaneous fuses with spiral arming system (see above - "IAL") was depending on the spin speed of the shell, and used to slightly modify the ballistic properties of the shells.

This new RY 24/31 model 1917 fuse devellopped in 1917 by Remondy ws designed to solve those problems, by using an arming mechanism with an inertia ring forced back at the departure of the shell, allowing the starter bearer to be hit by the percussion rod when hitting the objective.

This fuse was mainly used with the projectiles of the

• 75 mm fiel guns (high explosive shells model 1917)
• 81 mm mine-throwers

Small proportions of thes fuses have been manufactured including a delay gun powder grain (0,05 and 0,15 seconds)

The instantaneous fuse RY 24/31 mod 17 was strongly modified in 1918. The new fuse, named RYG 24/31 Mle 1918 fuse, was given the important advantages of

• being easier to be manufactured,
• using a double mechanism of forcing and inertia system for an even quicker detonation,
• being safer.

Vesions with short or long delay, or with male or female starter-bearer were successively built. One must note that this fuse survived during the WW1 to WW2 period, was manufactured in steel for the German troops during WW2, and was still in service in the French Army after 1945, machined in a light density alloy.

Just as the the first Remondy fuse, the use with too high initial velocity projectiles was prohibited, or must be made with a protection cap covering the fuse top, since the air pressure was able to provoke the percussion head forcing back.

That instantaneous fuse for trench mortar was less sophisticated than the celeb 24/31 mod. P.R.1916. It however had the same function, a cylinder containing a stem preceding the projectile, so that the projectile exploded before the head of the shell hit the objective.

There was though both a non delayed AND a delayed model !

That fuse mainly equipped the bombs of the

• 58mm n°1 bis trench mortars (projectiles with rear rod, 16 kg)
• 240mm trench mortars (projectiles with rear rod, 87 kg)

The french pyrotechnic barrel system is a major technologic evolution of the antique wooden or metallic polygonal time fuses, drilled with time channels. Its principle, applied for the first time in these time and percussion 25/38 mm Mle 1880 field fuse will be used under several evolutions until the second world war.

This initial fuse was made with a spiralled fusing tube. Graduated windows (from 0 to 22 seconds) on the protecting hat allowed to pierce the tube at the desired length, in order to let it communicate with the central room where was the igniting inertia system, actionned by the departure of the shot.

The time before explosion was determined by the length of the tube between that piercing and the base, where it would communicate fire to the powder room.

The double effect fuse 25/38 m80, was moreover equiped with a percussion system of the Budin type, that would act at the impact time.

The model shown here is the one with mobile hat, in which additionnal graduation at the cone base allowed to add 0 to 10 seconds to the fusing time. A mark with static hat also existed, without that additional time.

The time and percussion 30/38 mm Mle 1884 fuse was a double effect fuse. Therefore, it included both a time french-type barrel system, and a percussion system inside the tail. The hat covering the time system was graduated from 0 to 22 seconds.

The graduated hat window corresponding to the desired fusing time had to be pierced before the shot in order to let the spiralled tube communicate with the inner igniting mechanism. That manual operation was soon realised with the help of a double time setter box, needing the addition of a small stud at the cone base in order to make it compatible with that apparatus (the '30/38 mod 84' became the time and percussion 30/38 mm Mle 1884 T fuse since that date).

The percussion mechanism, inside the tail, was quite similar to a Saussier system one.

A new mark was adopted in 1887, with a pure Saussier percussion system, the time and percussion 30/38 mm Mle 1886 fuse. A second mark, the time and percussion 30/38 mm Mle 1886/89 fuse was equipped with a 'Robin' percussion system.

Including all its different marks, that fuse usually equipped the shells of the :

• 65 and 90 mm, as well as 10, 14 and 16 cm grape-shot shells
• 80, 90 and 95 mm grape-shot shells
• 80 mm mod 1895 A shrapnell shells
• Rear charge 120 mm shrapnell shells
• 80 mm mod 1895 A shrapnell shells

In 1886, the Time and percussion fuse 30/55 Mod 1886 fuse became the standard long fusing time fuse of the Marine.

Its time system was a classical French one (fusing spiralled tube, ignited by central inertia mechanism, and set by piercing the graduation corresponding to the desired combustion time), like the double effect fuse 30/38 mm mod 1884. The percussion mechanism was a Robin one.

But this fuse allowed longer flight times than its contemporaries, since it was graduated from 0 à 49 secondes.

This fuse mainly equipped the projectiles of the :

• 14 and 16 cm marine guns (grape-shot shells)

In 1890, the Robin percussion system was replaced by a Saussier one. This new version was named Time and percussion 30/55 mm modèle 1886/89 fuse. In 1902, a stud was added to the cone base to make the fuse compatible with the double time setter apparatus. The fuse was then named Time and percussion 30/55 mm modèle 1886/89 T fuse.

It mainly equipped with the projectiles of :

• 105 mm field guns (rear charge shrapnell shells)
• 120 mm guns (grape-shot and shrapnell shells)
• 155 mm (grape shot, shrapnell, and lightning shells)

A purely time model (without any percussion system) was designed in 1913, mainly for anti-aircraft use, allowing that a shell having missed does not explode when hitting the ground, usually in friendly territory.

This time 30/55 mm modèle 1913 fuse mainly equipped the projectiles of the :

• Anti-aircraft 75 mm guns (mixed shrapnell / explosive, rear charge shrapnell or tracing shells)
• 105 mm guns (tracing shells).

A mark of the double effect fuse 25/38 mm mod 1880, designed for the pig iron heavy shells (having an upper hole of 40 mm), of superior size, was developped yet in 1880, with a mobile hat (base graduations 0 to 10, added to the classical barrel graduations), and a 'Siège et Montagne' type percussion system.

This old time and percussion 40/55 mm fuse mod 1880 was modernised in 1893 by the use of the classical barrels, looking like the 30/55 ones.

This new mark was named 'Time and percussion non-detonator fuse 40/55 mm mod 1880/93'. It included a spiral fusing tube under a hat graduated from 0 to 49 seconds. The pieces of the 93 series were modified so that the mobile hat movements were blocked.

It seems that those old fuses were very seldom used during the war. However, the pictures shown at left are presenting a fuse of that type, mounted on a 75 mm shrapnell shell head, marked '40/55 - ECP 1-96 - ECP.R.1.08', and having a time-setter stud. Moreover, the percussion pin of the percussion system tail room is missing...

Hybrid assembly of the beginning of the war with pieces recuperated from stocks, or unknowned mark ?

This celeb fuse, using the typical French spiral tube fusing system, was specifically designed on the basis of the 18/28 Mle 1886/89 fuse for the famous 75mm quick-firing fieldgun Mle 1897, for its rear-charge shrapnell shells.

Graduated from 0 to 24 seconds for the time function (initiated by an inetria igniter located inside the head axis), the time before the explosion was set by piercing the graduated hat with a specific apparatus called 'débouchoir double' ('double time-setter'), needing the presence of a stud on the fuse cone base.

The items manufactured after the beginning of WW1 did not have intermediate graduation marks anymore between the holes of the hat.

The percussion system of that fuse was a Saussier one, for impact explosion.

The time and percussion 22/31 Mle 1897 fuse mainly equipped the projectiles of the :

• 65 mm guns (pig iron shells mod 1908 and shrapnell shells mod 1908)
• 75 mm field guns (ordinary mod 1898 shells, rear charge shrapnell shells mod 1897, mixed shrapnell / explosive mod 1897 A and M, incendiary shells mod 1916 G, incendiary shells type G, two lead bottles gaz shells, propaganda sheets shells, lightning shells type Bourget)

Solely designed for the communication of fire to the rear powder room of the shell via the 'tulip' and the central tube, it was not equipped with a detonator.

In 1916, a new model was produced, similar to the mod 1897, but without any percussion system in the tail (not visible externally). This exclusively fusing model, named 'Time fuse 22/31 mod 1916', mainly equipped the projectiles of the :

• 65mm guns (shrapnell shells mod 1908 and mod 1918/1911)
• 75mm field gun (ordinary mod 1898 shells, rear charge shrapnell shells mod 1897, incendiary shells mod 1916 G.)

An elongated model (with graduations from 0 to 31 seconds), named 'Time fuse 22/31 mm A modèle 1916' was also developped.

The fuse 22/31, in its versions 1897 or 1916, is the time French fuse that is most easily found on the battlefields nowadays.

Designed on the basis of a 22/31 time fuse, but with a 24 mm tail thread, this fuse filled the need for a detonator-fuse, time and percussion, that was missing within the French material at the beginning of the war (none of the time or time and percussion fuses of that period allowed the addition of a detonator).

Having a detonator coupled to the fuse rather than attached to the shells was an advantage, because of the easier ways of keeping the fuses safe from the weather than the shells.

The fuse tail bottom had a male thread where a detonator (of the same type that the ones used with percussion fuses Mle 1899) could be screwed.

The time apparatus was graduated from 0 to 24 seconds, just like the 22/31 time and percussion fuse Mle 1897. The percussion system in the fuse tail was a Robin-type one.

It was separated from the time system by a shutter, to avoid its accidental activation during the combustion. A short delay of 0,05 seconds wad systematically added to avoid explosions in the gun tube of high-explosive shells equipped with that fuse.

This model, named Time and percussion fuse-detonator 24/31mm Mle 1915, was mainly used with the projectiles of :

• 65, 75, 90, 105, 120 and 155 mm guns (high explosive shells, with low ranges for the calibers higher than 75 mm)
• 65 et 75mm (Shrapnell shells Mle 1926)

A strictly time version, of identical shape (and externally really similar) was developped in 1915 just by removing the Robin percussion system from the tail body. That fuse was called the Time Fuse-detonator 24/31mm Mle 1915 It was used with high explosive anti-aircraft shells (in order to avoid a ground explosion when descending in friendly territory if the time system was failing).

The increase of the range of the 75 mm field gun, thanks to the use of more aerodynamic shells, made the duration of the time system of the 24/31 Mle 1916 fuse too short for the full trajectory.

Therefore, in 1918 a time and percussion fuse-detonator was designed, elongated by the addition of an additional spire (6 spires instead of 5), graduated from 0 to 31 seconds, named 'Time and percussion fuse-detonator A 24/31 mm Mle 1918', with a 'A' for 'Allongée' ('Elongated'). A Robin-type percussion system was located in the tail.

It is easy to recognize that fuse thanks to the graduations, of course, but also by the thinner cone base, about half the regular one.

A purely tiem model, dedicated to the anti-aircraft fire, having the tail percussion system removed, had been put into service earlier in 1916 : the 'Time fuse-detonator A 24/31 mm Mle 1916'

The duration of the combustion of the time and percussion fuse-detonator was insufficient for the long ranges of the artillery of higher calibers than the 75 mm (before the 75 mm fielgun range was also upgraded). Consequently, a highly elongated model, with 9 fusing tube revolutions instead of 5, was designed.

That 'Time and percussion fuse-detonator LD 24/31 mm Mle 1917', with 'LD' for 'Longue Distance' ('Long Distance') was graduated from 0 to 51 seconds, and was equipped with a Robin-type percussion system in the tail.

It mainly equipped the projectiles of the :

• 105, 120 and 155 mm guns (high explosive shells)

This time again, a purely time model was designed in 1918 by the removal of the percussion system from the tail. That 'Time fuse-detonator LD 24/31 mm Mle 1918' was used for the anti-aircrafts fire.

To be exhaustive, we must notice the design in 1918 of a 'Time and percussion fuse-detonator LDA 24/31 mm Mle 1918' (also built in a purely time version), with 'LDA' for 'Longue Distance Allongée' ('Elongated Long Distance').

Having 10 revolutions, and graduated from 0 to 75 seconds, this latter fuse equipped the shells of the heavy artillery, and in particular of the ALGP ('Artillerie Lourde à Grande Puissance' - High Power Heavy Artillery).

Notable exception to the general use of revoluting fusing tubes for time fuses in France, this Saint Chamond time and percussion 2-discs fuse was using the classical revolving discs system that was generalized in all the other armies. The lower disc was graduated from 1 to 18.

The St Chamond time and percussion fuses were set by using a special apparatus named 'Regloir' ('regloir automatique sur banc a trepied')

It mainly equipped the projectiles of the :

• 70 mm semi-automatic mountain gun Saint Chamond
• 75 mm campaign guns of various types Saint Chamond