Musée de l'Armée aux Invalides
Lat : 48.85720 / Long : 2.31390
General comments on this surviving gun :
Identical items in the same location :
Items covered by this file :
Historic context :
designed in 1915 by the Commandant Van Deuren of the Belgian Royal Military School, this mortar in service in his country armies soon seduced the french authorities looking for a successor to the 58 Nr 1 bis mortar. An order of 400 such wepons was passed in 1915 (plus an additional 200 in 1916), and the mortars, manufactured in the Westinghouse Works in Le Havre, arrived slowly on the front from December 1915 to participate to the rude fights of the Frech army in 1916.
This simple mortar used the same princoples as the ones invented by the French Commandant Duchêne with its mortar 58 Nr 1, since it was based on a solid cylindric mandrel, this time of 70 mm, on which the hollow tail of the projectile was inserted. This latter was a 3-fins tail bomb, weighing 19.5 kg (including 6 kg high explosive). the propulsive charge of 50 g or 100 g 'BC powder' plus 12 g 'F3 powder' was placed on cartridges inserted into the projectile tail, and equipped with two conductive wires for a electric triggering.
Very simple and robus, setup in a very stable firing position on a platform, the 'mortier de 70 mm Van Deuren' or 'mortier V.D.' was also quite lightweight and therefore easily transportable on a special car on after dismounting into individual loads lighter than 60 kg each.Its fire rate was high thanks to the simultaneous introduction of the preconditionned propulsive charge and the projectile. It could launch its bomb up to a range of 600 to 700 m with a remarkable precision. The elevation angle of the tube was constant at 45 degrees, the aimed range was setup by both the choice of the propulsive charge and the modification of the expansion chamber of this propulsive load, thanks to a brass wheel located at the base of the cylinder and changing the position of the projectile along the 70 mm tube.
The real combat conditions revealed some issues of the V.D. mortar : its electric triggering proved itself sensitive to the trenches muddy conditions, and its tube was quickly overheating, making it necessary to change it every 5 or 6 shots for cooling down. For these reasons, but also because of the apparition of more modern weapons such as the 58 Nr 2 mortar, the French army progressively abandoned the VD mortars, some of them being recycled as anti-submarine grenade launchers on the navy ships.
The Belgian army continued using this weapon, that was still in service in May 1940. At lease two alternative versions were succesfully introduced :
- a 'mortier de 70/58 mm Van Deuren' specially modified to use the fin tail projectiles of the French 58 mm mortars (LS and DLS bombs of the 58 Nr2 mortar).
- a heavier version mortier de 90 mm Van Deuren (1916) with an increased 90 mm mandrel, firing a heavy 120 kg bomb to a range of 1400 m
Technical data :
- Complete description : 70 mm Van Deuren M 1915 mortar
- Design year : 1915
- Calibre : 70.00 mm (inside diameter of the projectile tail)
- Weight in firing position : 350 kg
- Weight for transportation : On a caddie (550 kg), or dismounted in several loads < 60 kg
- Tube length in calibres : 5.00
- Grooves : 0 n/a
- Projectile weight : 19.5 kg (mortier de 70) - 18 et 35 kg (mortier de 70/58 mm - bombes LS et DLS) - 120 kg (mortier de 90)
- Initial speed : unknown
- Fire rate : 3 to 4 rounds per minute
- Range : 700 m (1400 m for the 90 mm mortar)
- Elevation range : constant 45 degrees angle
- Direction range : 120 degrees total range