Polish armoured motor wagon wz.28
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  © Michał Derela, 2011 Updated: 19. 02. 2014 - minor update

Polish armoured motor wagon wz.28

One of least known Polish armoured fighting vehicles of interwar period is a prototype of an armoured motor wagon, first known to wider public from mysterious photos published in a fundamental Paul Malmassari's book on armoured trains. Polish prewar sources referred to it as: "wagon pancerny elektro-spalinowy" (armoured wagon with electric-internal combustion drive). It is sometimes known as the wagon "wz.28" (1928 Pattern) in current publications, although it was never standardized and this designation is unofficial. It was one of only few Polish armoured motor wagons, and the strongest of them. The information on it is far from complete, but we have been able to gather all known facts and photos here, some unpublished before.


History

First published photo of the armoured motor wagon, during exercises of the 2nd Armoured Train Detachment in Pilawa in 1934. Note ball machinegun mountings. [own collection]

In the second half of 1920s, the Polish armoured trains were in deep stagnation. A handful of stock left after Polish-Soviet war was mostly remaining in reserve and its condition was degrading, while funding was scarce. In spite of this, theoretical studies on the question of most valuable armoured train type were carried out. In 1928 a head of the Engineers Department ordered the Armoured Weapons' Construction Bureau to design a light armoured train. It was to consist of only two armoured wagons and two flatcars. The first wagon was to be a motor one, armed with a 75 mm gun and five machine guns. The second towed wagon was to be armed with two 37 mm guns and 10 machine guns. The motor wagon was supposed to be used within the light train, or separately, as a heavy armoured draisine (it is not know, if the towed wagon was eventually built, although there are known photos of a mysterious wagon with one turret of Ursus type for 37 mm gun).

A construction of the motor wagon was ordered in State Sappers Works (Państwowa Wytwórnia Saperska). It was to be completed in August 1929 (there exist only several documents regarding this wagon, so actual date of completion is not known). Since it was an experimental design, a two-axle flatcar chassis was utilized, with tramway-type traction engines, driving axles by chains.

First trials showed some flaws of the design. Moreover, during one ride, the wagon was derailed. The design could have been improved, but military authorities apparently ceased interest in it and stopped funding. On 8 March 1932 it was reported, that the wagon had remained on proving ground track for 5 months and needed cleaning from rust before it could be given to the 1st Armoured Train Detachment in Legionowo. The commission could not accept the wagon without bringing it to working condition.

Above, below and on a title photo: the motor wagon during trials, lacking side machine gun mountings. Visible are two universal ball machine gun mounting in front (above). [CAW]
Below: first published photo of the armoured motor wagon in Pilawa in 1934. A box on the wall might cover a braking crank. [own collection]

There is no information on the wagon's further fate. It was apparently not treated as a combat vehicle. According to information researched by Arthur Przeczek, it probably carried number 684 717 (as Pddkz series flatcar), and in 1933 it was in the 1st Armoured Train Detachment, then in 1937 in the 2nd Armoured Train Detachment in Niepołomice. Unpublished photos on this page however suggest, that the wagon had been in the 2nd Armoured Train Detachment already in 1934, and it was used there for exercises for some time. It is not known, if it was in working condition until the war. There is no information, that it was used in September 1939 campaign, even as a towed wagon. It was not used later by the Germans either.


Description

The armoured motor wagon was built upon a chassis of a flatcar series Pddkz, type VIIC. It was fitted with a body of flat plates, screwed or bolted to a frame. Its side silhouette was close to rectangular. Upon a roof, on one end, there was an angular artillery turret made of screwed plates (original description suggests, that this was a front end, though the wagon certainly could ride in both directions with the same speed). The body was first made of wood, to examine a silhouette, but soon it was replaced with a steel one (most probably made of boiler steel, not armour steel, as it was an experimantal unit). A thickness of plates was to be 6-12 mm, which should be enough against rifle bullets from some distance. In cross-section, the wagon was octagonal, its walls were slightly sloped to increase chances of bouncing shots, although apparently not much. Entrances were in front and rear end walls, with two-leaf doors, enabling passing between wagons.

Main armament was French 75 mm wz.1897 field gun in a turret, mounted on a naval pedestal mount. A horizontal field of fire was 360°. 200 artillery rounds were carried.

The armament was supplemented with machine guns 7.92mm wz. 25 (Hotchkiss), in ball mountings. According to an original description, there were three machine guns: one in a front wall, and the other two - in side half-turrets, offering quite wide angle of fire. The photos show, that the wagon had also machine gun mountings in a rear end wall and in a turret's front. That would make a number of 5 machine guns, planned initially, although there are no photos with any machine guns actually mounted. There were also designed openings in turret to fire a machine gun against aircraft, but there are no closer information (probably they would offer a limited field of fire). 6000 rounds for machine guns were carried in total.

The wagon had an aircraft petrol engine SPA, nominal power 220 HP (actual power was estimated in technical description to be some 170 HP, probably due to the engine's wear). It powered a generator Brown Boveri (power 100 kW at 1300 rpm, 600V), which gave electric power to two tramway-type traction engines D54. The traction engines were under a floor and powered the two axles by chains (the engines were borrowed and could not drive axles directly, because it would need modifications to engines due to bigger axle diameter). A water radiator was a provisional one, borrowed from an electrotechnical battalion. The main engine was started with a crank or an electric starter Bosh BP L9, powered by 24V batteries. The wagon had a small generator Brown Boveri 110V, driven by a chain from the main engine's shaft, used for battery charging, lightning, ventilation and signalization. The wagon also had an auxiliary generator with engine Vinton 5 kW for these purposes, when the main engine was off. It could also drive traction engines to ride with slow speed, in case of damage to the main engine. There is no information, if the wagon had one or two steering places, but two would be logical. Probably the wagon had crank-operated mechanical brakes.

A crew was 13: the train's commandeer (officer), driver, three men of gun crew, five men of MG crews, two men for the engine maintenance and an orderly (medic).


Specifications

A drawing of the armoured motor wagonu [source: Kartonówka Nr. 1(5)/2002]

Sources:
1. Grzegorz Pomorski (? - uncredited), "Wagon pancerny elektrospalinowy", in: Kartonówka Nr. 1(5)/2002 (Polish magazine, also including a H0 cardboard model)


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Text copyright to Michal Derela © 2011