Škoda Experimental 10.5 cm Compressed Air Mortar
By Michael Heidler
When the U.S. Third Army arrived at Pilsen in Czechoslovakia on 6 May 1945, their primary target was the armament industry of this region. One of the most important companies was Škoda. Founded in 1859, the company began its business with steam engines, bridge building and armament of battleships. Later, Škoda became famous for the developments of heavy artillery like the 42-cm Küstenhaubitze M14 and armoured vehicles like the Jagdpanzer 38(t) "Hetzer". In 1942 the company became part of the German controlled holding "Waffen-Union Škoda-Brünn" based in Berlin. By the middle of 1944 more than 45,000 people were working at the plant in Pilsen, with a total of 100,000 in the whole concern. Near the end of the war the Pilsen plant was largely destroyed by an Allied bombing attack on 25 April.
Nevertheless a lot of equipment, machinery and weapons survived the attack and was captured by the U.S. Army. The booty also contained an experimental mortar operated by compressed air. It was originally designed for the German army, but the dates of development and manufacture are not known. The weapon with the designation "10.5 cm Druckluftwerfer" (4.13-inch compressed air mortar) was to be mounted on a vehicle.
The mortar is fired by compressed air and does not have a recoil mechanism. The outstanding features of the mortar are that there is no muzzle flash and no sound of explosion. The mortar is mounted on a heavy, circular base plate. Handwheels for traversing and elevating the piece are attached to the framework near the base, the elevating handwheel on the right side and the traversing handwheel on the left. A small spring equilibrator is provided to overcome muzzle mass.
Between the handwheels, at the base of the breech end of the mortar, is a spring-retained lever. This lever operates a valve that controls the air pressure going into the base of the tube. To fire the weapon a slight pressure on the lever, releasing the air, is all that is necessary. There are also two smaller valves at the base of the tube. These valves are operated by means of knobs, and one controls the intake of air and the other the pressure gauge.
The tube is opened by pivoting it to the side of the base. It is opened for loading by a lever on the right side. In order to pivot the tube, the lever is rotated downward and to the side. After a round is loaded into the tube, the lever is rotated in the opposite direction from those used for opening, thus locking the tube in the firing position.
According to documents and interrogation of workers only one mortar had been completed. Tests were conducted by the German army, but the results are not known.
Caliber: 10.5 cm (4.13 inches)
Elevation: 0° to 75°
Weight in firing position: 450 kg (992 lbs)
Air pressure to fire the weapon: 150-200 kg/sq.cm (2,130-2,840 psi)
(The author would like to thank the Aberdeen Proving Ground Ordnance Museum, USA)
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