By the early 1930s, the Polish army still didn’t have any type of reconnaissance vehicle that was truly successful. The main armored car (actually a half-track vehicle) was the wz.28, which had a lot of imperfections, like weak armor and armament. The new wz.29 ‘Ursus’ (as these vehicles were produced at the “Ursus” Mechanical Works in Warsaw) was also far from satisfying. Although the wz.29 was well armed and armored, its maximum speed was too low and it had problems off-road. Moreover, the wz.29 was only produced in small numbers.
A new project was started, with the aim of creating a successful armored car for the needs of the Polish Army. In 1930, the Polish PZInż (Państwowe Zakłady Inżynieryjne – the National Institution of Engineering) company (also responsible for later projects like PZInż 220 – the prototype of the famous 7TP) reached an agreement with the Swiss Adolphe Saurer S.A. company for the production and selling of Swiss cars and trucks under licence. The 6×4 chassis of one of the Swiss trucks was a good basis for the new armored car. The project was developed by the designers at BK Br.Panc.WIBI. (pol. Biuro Badań Technicznych Broni Pancernej Wojskowego Instytutu Badań Inżynierii; Armoured Weapons Construction Bureau of the Army Engineer Research Institute). As the final design was ready in 1931, the new project received the designation ‘wz.31’ – ‘wzór 1931’, ‘the specimen 1931’. This name is also shared with a type of helmet, so it can be easily be mistaken on a list of items for example.
Illustration of wz.31 by Janusz Magnuski – it’s currently the only one picture of this armored car. However, it’s imperfect, as this wz.31 has not 37 mm cannon in the turret and front machine gun in the hull. Photo: dobroni.pl
Design and Armament
Unfortunately, today the design of the wz.31 is mostly forgotten, as this project was quickly abandoned during the invasion and all of the wz.31 blueprints were destroyed during World War II. The only existing image of the project is the one created by Polish historian Janusz Magnuski. In his picture, the wz.31 does not have the front machine gun and the turret has no cannon. In Magnuski’s drawing, the wz.31 is looking similar to the German 6-wheeled Sd.Kfz.231 (6-rad) or the Soviet BA-10. However, a number of sources have survived.
The general design was based on the previous wz.29, as it was well armored and armed for its time. The chassis of the wz.31 was derived from a truck created by the Swiss Adolphe Saurer S.A. company. Unfortunately, the exact type of truck is unknown. The vehicle had 6 wheels and the rear two axles were powered by the engine. The car probably had 4 forward gears and one reverse. The engineers designed two types of the engines: a four-stroke, 6-cylinder straight engine providing 100 horsepower and a four-stroke, 6-cylinder diesel engine with 84 hp. Both of the engine types were equipped with a liquid cooling system. They were produced by Saurer. The wz.31 had two driving positions: one in the front and one in the back of the vehicle. Internal communication was provided by an interphone.
The main armament was placed in the turret, which was the same as on the wz.29. The turret had 2 machine guns. One of them was fired through the roof of the turret, providing anti-aircraft fire, while another one was placed facing the rear-left of the turret. The previous wz.29 ‘Ursus’ was also armed with one 37 mm cannon. The weapons were placed asymmetrically, at an angle of 120 degrees in order to provide more space. Moreover, the wz.31 could have had one machine gun in the back of the hull (like the wz.29) and one in the front (with space for a machine gun operator alongside the driver). The machine guns were wz.25s (Polish version of the French Mle 1914 Hotchkiss) and the cannon was also French, the SA-18 Puteaux 37mm.
wz.31 artist impression by David Bocquelet
The project of the new heavy armored car was rejected quickly, despite all the mentioned advantages. The army didn’t even bother to build a prototype and so the wz.31 remained only as a paper project. The main reason for the wz.31’s rejection was simple – the cost of building it was too high. One wz.31 cost 160,000 Polish złotys, with 99,000 for armament and zł61,000 for chassis and hull. For comparison, the construction of one TKS tankette cost just zł47,800. Moreover, the quite expensive, but rather weak anti-tank armament of the wz.31 was evaluated as ineffectual. The modern armored car needed a more powerful anti-tank gun, not numerous anti-infantry weapons. The new vehicle was also deemed to be too big and heavy.
There can also be another reason for the wz.31’s failure. In 1930, the heavy armored car was displaced from its role as a scout vehicle by tankettes. The production of the TK-3 tankette started in 1931.
Unfortunately, in 1939, the Army of the Second Polish Republic was still lacking a satisfying armored car, as the wz.34 produced in 1934 still had a lot of imperfections.
|Dimensions||7 x 2.08 x 2.6 m (23 x 6.8 x 8.5 ft)|
|Total weight||7.8 tons|
|Propulsion||Straight (100hp) or diesel (84hp) engine, 6-cyl, Saurer|
|Maximum speed||55-60 km/h (30 – 37mph)|
|Armament||37mm Puteaux SA-18 + 4 x 7,92mm wz.25|
|Armor||5 – 12 mm (0.1 – -0.4 in)|
Links, Resources & Further Reading
“Samochody pancerne Wojska Polskiego 1918-1939”, Janusz Magnuski; WiS; Warszawa 1993
‘Pojazdy w Wojsku Polskim – Polish Army Vehicles – 1918-1939’, Jan Tarczyński, K. Barbarski, A. Jońca; Ajaks; Pruszków 1995.
‘Wrzesień 1939 – Pojazdy Wojska Polskiego – Barwa i broń’; A. Jońca, R. Szubański, J. Tarczyński; WKŁ; Warszawa 1990
‘’Broń strzelecka i sprzęt artyleryjski formacji polskich i WP w latach 1914-1939’ A.Kontankiewicz; Wyd. Uniwersytetu M. Curie-Skłodowskiej; Lublin 2003