Canon de 240 modèle 93/96 TAZ

Canon de 240 modèle 93/96
A 240 mm modèle 1893-1896 gun, on St Chamond railway mounting.
Type	Railway gun
Place of origin	France
Service history
Used by	France
Wars	World war I
Production history
Designer	St Chamond
Manufacturer	St Chamond
Produced	1918
No. built	8
Specifications
Mass	140 t (140 long tons; 150 short tons)
Length	19.5 m (64 ft)
Barrel length	10 m (33 ft) L/42
Width	2.6 m (8 ft 6 in)
Height	2.7 m (8 ft 10 in)
Shell weight	162 kg (357 lb)
Caliber	240 mm (9.4 in)
Elevation	+15° to +35°
Traverse	58°
Rate of fire	6 rpm
Muzzle velocity	840 m/s (2,800 ft/s)
Maximum firing range	23 km (14 mi)

The Canon de 240 modèle 93/96 was a French Railway gun piece used by the French Army during World War I.

History

Although the majority of combatants had heavy field artillery prior to the outbreak of the First World War, none had adequate numbers of heavy guns in service, nor had they foreseen the growing importance of heavy artillery once the Western Front stagnated and trench warfare set in. Since aircraft of the period were not yet capable of carrying large diameter bombs the burden of delivering heavy firepower fell on the artillery. Two sources of heavy artillery suitable for conversion to field use were surplus coastal defense guns and naval guns.

However, a paradox faced artillery designers of the time, while large caliber naval guns were common, large caliber land weapons were less common due to their weight, complexity, and lack of mobility. Large caliber field guns often required extensive site preparation because the guns had to be broken down into multiple loads light enough to be towed by a horse team or the few traction engines of the time and then reassembled before use. Building a new gun could address the problem of disassembling, transporting and reassembling a large gun, but it didn't necessarily address how to convert existing heavy weapons to make them more mobile. Rail transport proved to be the most practical solution because the problems of heavy weight, lack of mobility and reduced setup time were addressed.

Design

The Canon de 240 modèle 93/96 started life as eight coastal defense guns that were removed from fortifications at Dakar, Senegal and Saigon, Vietnam. Because of this the guns were often referred to as "colony" guns. The eight gun barrels were placed on the existing rail carriages for the Canon de 305 modèle 93/96 manufactured by the firm of St Chamond. The carriages were originally deployed in 1916 but it was too much gun for too little carriage so the 305 mm (12 in) barrels were replaced with 240 mm (9.4 in) barrels by St Chamond and entered service in 1918.

The guns were mounted on rectangular steel bases, which were suspended on two railroad bogies. The rear bogie had four axles, while the front bogie had six axles. The number of axles was determined by the weight limit for European railways of 17 tonnes per axle and 17x10 = 170 tonnes. Since the barrels were coastal defense guns that were not intended for use at high angles of elevation the trunnions were relocated relatively far forward and the howitzers were nose heavy which is why the front bogie had more axles than the rear. The guns sat on a circular central pivot pedestal mount which sat on a large diameter geared steel ring. A rectangular steel firing platform sat on top of the ring with the barrel of the gun overhanging the platform at the front and an overhanging loading platform for the gunners to the rear. The firing platform was then traversed by a worm gear which attached to the base.

The guns had a Welin breech block and used separate loading bagged charges and projectiles. To load the howitzer the barrel was lowered to -8° and there was an elevated shell handling trolley at the rear. The howitzers had a hydro-pneumatic cradle recoil system where the cradle recoiled up a slightly inclined rear deck which helped return the howitzer to battery after firing. The carriage used ground platform anchoring and the rear bogie could be jacked up to help absorb recoil. The carriage used a car traversing mount so traverse was limited to a few degrees each side of the howitzers centerline. The howitzers normally required two days of setup before firing, which consisted of reinforcing an area of track with wooden beams and digging a pit for the earth anchor and another for howitzers breech at high angles of elevations more than 45°. There were also four jack stands that could be lowered onto the platform and fastened to the timbers to provide a stable firing platform.