When the Czechoslovak army bought their first tanks in the early twenties, seven French Renault FTs, they already wanted to produce tanks in their own country. Combined with an interest in the so-called wheel-cum-track tanks, they bought the rights in 1923 to produce an agricultural tractor, modified by German tank designer Joseph Vollmer. This tractor, called WD Z 50PS, was originally produced at the Hanomag company in Hanover, Germany. Although this Czechoslovak project started as an artillery tractor, it ended up being the first tank built in Czechoslovakia
This is the original converted Hanomag tractor by Vollmer, on which the vehicles were based. On the Kolohousenka vehicles, the engine was moved to the back. Photo: warspot.ru
The Idea of Wheel-Cum-Track
Some of the main shortcomings of early tanks were their slow speed and the short life of the tracks. One solution for these problems was designed by famous American tank designer Walter Christie. Christie’s design had removable tracks so the tank could drive on its wheels. This solution is best known for its use on the Soviet BT tank series.
Another wheel-cum-track solution was more sophisticated. This solution consisted of a four-wheeled chassis merged with a tracked chassis. The wheels could be lowered or lifted and be fixed in the needed position, so the tank could either drive on its wheels or tracks. This system combined fast speed on roads with good terrain resistance, but it was very complex, resulting in difficulties in building and repairing, which led to high production costs.
Due to the positive aspects of this system, it gained wide interest in multiple countries, including Britain and Sweden. Several experimental vehicles were developed, like the Swedish Landsverk L-5 and the British Vickers D3E1, but the negative aspects meant that most projects remained in their experimental stage, including the Kolohousenka project.
Good sideview of the KH-50 tank. Note the ramps on the side and the unfolded front hatch. Photo: warspot.ru
After the introduction of tracked vehicles in World War I, caterpillar-tracked vehicles also gained interest in the agricultural department of the German company Hanomag. Two of their designers, Ernst Wendeler and Boguslav Dohrn, started designing tracked tractors and came up, among others, with the WD Z 25 in 1920 and the WD Z 50 in 1921. Both of these vehicles gained interest from the Czechoslovak army and they bought respectively two of the former and four of the latter between 1923 and 1927. The rights to produce both tractors locally were also bought.
At the same time, Joseph Vollmer, who had designed tanks in World War I, designed his own wheel-cum-track system, based upon the WD Z 50. In 1923, the Ministry of Defense (Ministerstvo národní obrany or MNO) bought the documentation on his design for a total of Kč1.3 million (the equivalent of approximately US$516.750 in 2017 values). After evaluation of the design, it was thought to be suitable and the company Breitfeld-Daněk (which would later merge into Českomoravská-Kolben-Daněk) was ordered to build two experimental vehicles. Note that these vehicles were intended as artillery tractors. They also asked the companies Ringhoffer (later Tatra) and Laurin & Klement (later Škoda) to assist in the development and building process. In 1924, the first two vehicles were ready and given the designation KH-50. 50 referred to the horsepower rating of the engine and KH was the abbreviation of Kolohousenka, the merging of the Czech words ‘kolo’ and ‘housenka’, meaning ‘wheel’ and ‘caterpillar’ respectively.
These two tractors were tested in the city of Prague by the Military Technical Institute (Vojenský Technický Útvar or VTU). One of the two vehicles broke down in a very short time and was in such a bad state that it had to be scrapped. The other tractor was modified and an armored superstructure was added, together with a fully rotating turret mounting a 37mm gun. With this armored addition, the vehicle became the first Czech-built tank. Tests continued with the tank, but the army was not convinced that this tank would be a worthy acquisition and no order was placed.
In 1927, the leading company in the design, Breitfeld-Daněk, merged with the company Českomoravská-Kolben and formed CKD. This lead not to the termination of the project, instead it was decided to modify the vehicle again. The complete vehicle was revised and the engine was replaced by a more powerful WD 60PS 60hp engine. The turret was also replaced, by a round-shaped one which carried two machine guns. The designation of this modified vehicle as it now had a 60hp engine was changed to KH-60. Despite the improved performance, the army still decided not to order it, but they accepted the prototype in 1930 and it received the registration number 13362. Two more vehicles were built as tractors, which got the attention of the Soviet Union and both were sold to them in 1927. The Soviets already had the Kommunar tractors in service, which were also based on the WD 50 tractor.
The KH-50 tank showing how the ramps are used to change from tracks to wheels. Photo: Bellona Publishing
After two years, in 1929, CKD made its last attempt to improve the vehicle and sign a contract with the army. The turret was rebuilt and the lifting system of the wheels was improved and made more reliable. The engine was replaced, again by a more powerful one, with 70hp. The designation for this vehicle was now KH-70. However, the Czech army was not interested at all in buying the vehicle, because they viewed it as obsolete. The vehicle was examined by the Italian army, but if it was sold to them is unclear. Due to the failure of this latest creation, the project was finally canceled and CKD turned its attention to building ‘normal’ tanks.
The engineer who participated in the design process of this vehicle and became very successful was the Russian engineer Alexey Surin. He fled to Czechoslovakia after the Reds had won the civil war and became an engineer of CKD in 1923.
The KH-50 used the original engine, a Hanomag four-cylinder, four-stroke, water cooled 50 hp engine, but it was swapped from the front to the back of the tractor. It could be powered with either benzene, gasoline or kerosene. The KH-60 and KH-70 were both powered by more powerful engines from the same company. The driver’s position was moved from the back to the front and lowered into the hull. The front hull was redesigned and somewhat similar to the Renault FT, already in use in the Czechoslovak army.
Picture of the KH-60 tank. The main layout differences are quite good visible. The exhaustion is moved to the top of the tank and the front has been redesigned, as well as the turret. Photo: utocnavozba.wz.cz
When the first vehicle was rebuilt as a tank, the superstructure and turret were designed and built by Škoda. It consisted of riveted flat sheets of armor, and the design was inspired by the Renault FT, especially noticeable in the front armor and turret. In this turret, a 3.7cm Škoda d/27 gun was mounted. When the vehicle was rebuilt as KH-60, the turret was changed to a cylindrically shaped one, designed by CKD. This turret mounted two 7.92mm Schwarzlose vz.24 machine guns. A 47mm Vickers was also considered. A rear tail was added to the KH-70 model to improve trench crossing.
Changing from wheel to track had to be done manually by the crew. This took about fifteen minutes. The ramps to change were carried on the sides of the vehicle. With the KH-70, the time to change was reduced to ten minutes. The crew consisted out of two men, a driver, and a commander. The driver was located in front of the tank, while the commander was located in the turret and also acted as loader and gunner, the same situation as in the Renault FT. The commander could get inside via hatches installed on both sides of the vehicle. The driver could get in through hatches mounted in the front of the vehicle, again comparable to the FT.
The KH-70 tank. Only one vehicle of this type was made. Either the turret is turned, or the armament is not installed. Photo: Aviarmor.net
A distinctive feature of the vehicle were the two headlights, which were mounted on the hull. On the KH-50 tank model, they were built into the hull, resulting in two ball-like extensions. The exhaust pipe was located at the side but was moved to the top of the vehicle with the KH-60 and 70. None of the three models had a radio installed, so communication had to be performed with hand signals or flags. The engine could be reached by one hatch, covering the complete back of the vehicle, and two smaller hatches at the sides. The armor on the turret and the front was 14mm thick.
As already mentioned in the development section, one of the first two KH-50’s tractors was scrapped due to a bad break down. The other vehicle was modified as a tank and later on remodeled into the KH-60, was bought by the army and examined until 1935, when the vehicle was installed as a static monument in front of the Tank School. Although it was effectively taken out of service, it was still mentioned in German handbooks in 1939. After the German invasion of Czechoslovakia, it was taken to a German depot where it was scrapped.
It is not known what happened with the two artillery tractors delivered to the Soviet Union. No photographs are known of the vehicles in Soviet service and their fate is also unknown, as is the case with the KH-70. With the experience gained by this project, Tatra designed a wheel-cum-track tractor on their own in 1929, the Tatra KTT, but the army was not interested in this project either.
After the cancellation of the project in 1930, interest in wheel-cum-track vehicles wained, but research was still being done by both Škoda and Tatra. They received orders in 1929 to design a heavy wheel-cum-track tank and they came up with respectively the Š-III and T-III. Vollmer’s design was not allowed to be used anymore because its building rights had expired and had to be bought again if they wanted to use it. Instead, the companies had to come up with their own design. Each company built two prototypes, but they suffered from severe technical malfunctions. Like the Kolohousenka, these vehicles were a failure, and the army abandoned the idea of a wheel-cum-track vehicle for good.
|Dimensions (L-W-H)||4.5 x 2.39 x 2.53m (14.8 x 7.8 x 8.3 ft)|
|Total weight, battle ready||7.5-10 tons|
|Crew||2 (commander, driver)|
|Propulsion||Hanomag WD 50PS, 50 hp|
|Speed||21.7 mph (35 kph) on wheels, 9.3 mph (15 kph) on tracks (both on road)|
|Range||186 miles (300) km on wheels on road|
|Armament||3.7 cm Škoda infantry gun|
|Armor||6 – 14 mm (0.24 – 0.55 in)|
Links, Resources & Further Reading
-Czechoslovak armoured fighting vehicles 1918-1945, Bellona Publishing, by Charles K. Kliment and Hilary Louis Doyle, 1979.
-V.Francev, Ch.K.Kliment “Československa obrnena vozidla 1918-48”. Prague. 2004
-Czechoslovak heavy armored vehicles. Development, production, operational use and export of the Czechoslovak tanks, armored cars and tracked artillery tractors 1918-1956, PhDr. Ivo Pejčoch, Karlova University, Prague, 2009