The central European nation of Czechoslovakia was established after the First World War as one of the successor states of the Austro-Hungarian Empire. Home to large vehicle and arms industries, it had several military ambitions. Two of those were the acquisition of tanks and tracked artillery tractors. These new vehicles were to be built in Czechoslovakia. Considering that the early tank and tracked tractor designs had some flaws, especially regarding mobility, it was decided to pursue the promising new technology of wheel-cum-track vehicles. A design for such a system was bought from German engineer Joseph Vollmer in 1923, marking the proper start of development of the first Czechoslovak tracked artillery tractor, which would eventually lead into the tank project based upon the same chassis.
Since independence, Czechoslovak military authorities paid close attention to foreign development of tracked artillery tractors. Like tanks, this kind of vehicle suffered from several disadvantages in mobility and service life. Tracks were prone to wear and tear, thus maintaining a large fleet of tracked vehicles would be costly in maintenance and track replacements. Furthermore, the early track designs did not allow great cruising speeds, making them especially disadvantageous during long road travel. Apart from that, road surfaces were easily torn up and damaged by the metal tracks.
Apart from just improving tracked technology, some engineers came up with other solutions to these problems. One such solution, namely the idea of removable tracks, was pursued by the famous (and infamous) American tank designer Walter Christie. It allowed a vehicle to drive on its wheels and when necessary, tracks could be fitted.
A more sophisticated solution was the wheel-cum-track system. Basically, such a system consisted of a four-wheeled chassis merged with a tracked chassis, with the idea that either of those configurations was used depending on the situation. It promisingly combined the characteristics of a wheeled vehicle, with fast speeds on road and little wear and tear to the running gear, while also having off-road capabilities, thanks to the tracks. These prospects garnered interest in several countries during the 1920s and led, for example, to the British Vickers D3E1 (1928), the German/Swedish Landsverk-5 (1928), the French Saint-Chamond M21 (1921), and the Soviet Dyrenkov DR-4 (1929), among others.
It was a typical interwar development, with a great deal of effort put in, and producing few if any substantive results. This was mainly due to the fact that none of the wheel-cum-track systems worked as well as hoped. The systems were complex designs, thus not only time consuming in manufacture and repair, but also costly in production. Furthermore, the systems were fragile and exposed, making them prone to defects and failure.
However, most of these insights had yet to be discovered when the Czechoslovak Army also showed their interest in such a system, designed by Joseph Vollmer.
Joseph Vollmer, Hanomag, And The WD Tractors
Joseph Vollmer (1871-1955) was a German engineer and designer of automobiles. Together with his friend Ernst Neuberg, he founded the company Deutsche-Automobil-Construktionsgesellschaft (DAC) in 1906. Their main business was to design and patent automotive parts and sell production licenses to other manufacturers. During the First World War, business came to a near standstill, as many employees were enlisted in the German Army. Vollmer himself became involved with automotive projects carried out by the Army. From 1916 on, he took part in the German tank program and directed the development of the A7V tank and was also responsible for the K-Wagen and LK series of tanks.
After the war, German tank development had to be terminated, and Vollmer returned to business with DAC. Both he and Neuberg realized that there would be little demand for civilian vehicles in the immediate post-war period and decided to refocus on the development of commercial agricultural vehicles. Vollmer used his war experience with tanks to design several tracked tractors. Production licenses for these were sold to various manufacturers, both in Germany and abroad. One of those was the Hannover-based company Hanomag. In 1922, they would take into production two of Vollmer’s designs, a light tractor with a 25 hp engine, and a heavy tractor with a 50 hp engine.
Hanomag was already producing a motor plough, designed by engineers Ernst Wendeler and Boguslav Dohrn. It was marketed as WD (first letters of their respective surnames) and had built a good reputation. It was decided to market Vollmer’s designs under the same name, WD 25 and WD 50 respectively, with the number referring to the amount of horsepower.
Vollmer’s Wheel-Cum-Track System
Based upon the WD 50, Vollmer developed a wheel-cum-track system which was known as the RR-50, with RR standing for Räder-Raupen (English: Wheels-Tracks). It was one of the earliest examples of this kind of new technology. In 1923, the RR-50 was offered to the Czech Military Administration, which found the design to suit the need for a modern tracked tractor. The Ministry of Defense (Ministerstvo Národní Obrany, abbreviated to MNO) bought the licenses for this design for a total of Kč1.3 million (~ US$516,750 in 2018 values).
While some basic parts were to be imported, two prototypes were to be built by domestic manufacturers. The name RR-50 was transcribed into Czech as KH-50. KH was the abbreviation of Kolohousenka, the merging of the Czech words ‘kolo’ and ‘housenka’, meaning ‘wheel’ and ‘caterpillar’, respectively. Overall assembly and production of the main components was to be done by the firm Breitfeld-Daněk (which would later merge into Českomoravská-Kolben-Daněk, ČKD). The gearbox, rear-wheel drive system, and the tracks were to be delivered by Laurin & Klement (later Škoda), while the steering unit and the front axle with wheels were to be supplied by Kopřivnická vozovka (later Tatra). Meanwhile, the engines were bought in Germany from the Dresden-based manufacturer Hille. They were 4-cylinder K3 petrol engines which produced 50 hp at 1,100 rpm (up to 60 hp at 1,400 rpm).
Construction And Testing
On 17th March 1924, MNO filed Vollmer’s patents concerning the design at the Czechoslovak patent office. It concerned the patents numbered 21575, 21577, 1578, 22123, and 23431. Production of the two prototypes, with serial numbers 2001 and 2002, began at Breitfeld-Daněk and finished just before the end of the year, in December. The first driving and technical tests began on 7th January 1925 and, after these were completed, both tractors were reconstructed. On 6th March, they were officially handed over to the Automotive Artillery Department (Auto Oddělení Dělostřelectva). The MNO paid Kč1,651,820 (~ US$657,000 in 2018 values).
After the takeover, the tractors were immediately put to the test. It was established that they had to drive 3,000 km on wheels and 500 km on tracks, both on the road. Furthermore, it had to tow a 210 mm gun for 1,000 km on wheels and 200 km on tracks. Lastly, it had to maneuver off-road while towing a gun, for 200 hours. During these trials, the tractors often broke down due to the relative crudeness of the design and thus, the tests could only be finished by 1926. By June 1926, both tractors were located in the city of České Budějovice, at the artillery barracks in the part of the city known as Čtyři Dvory (Eng: Four Courts).
While the MNO had originally expressed the intention to potentially buy some 100 examples, no further KH-50s were ordered. Instead, in June, the Ministry allowed the KH-50 to be marketed to other countries, on the condition that 30% of the profit was paid to the Ministry to compensate for the license and development costs. On 24th June, the Military Technical Institute submitted a proposal to reconstruct one of the two tractors in order to perform more tests, but it appears both remained at Čtyři Dvory.
Design And Workings Of The System
As far as the wheels were concerned, the tractor was fitted with a front steering axle and a rear-drive axle with double wheels. The wheels had a diameter of 14 by 77 cm and were suspended by leaf springs. To change from wheeled to tracked drive, arch-shaped wooden wedges were utilized. First, the axle was unlocked and the wheels were driven up the wedges, so the wheels with the axle lifted upwards. Once fully elevated, the axle was locked again. The change could be performed by two people and within five minutes.
Changing from tracks to wheels was done the same, but this time, the tracks had to drive up the ramps, lifting up the tank sufficiently to lower the axles again. The tracks had a width of 30 cm. The track units were similar, but not identical, to those of the WD-50 tractor. Not only were the dimensions changed, but it also utilized a different kind of track links, and the mud shoot was eliminated.
The vehicles lacked a proper superstructure. The crew was seated in the open, while the engine was protected by a simple sheet metal box. The vehicle weighed 6,800 kg and was able to reach a maximum speed on wheels of 21 km/h and 14 km/h on tracks. For shorter periods, the power of the engine could be increased to 60 hp, improving the speed on wheels to 27 km/h and the speed on tracks to 18 km/h.
The Ministry’s approval to sell the design abroad paid off when the USSR placed an order for two tractors with a stronger engine, known as the KH-60. They were produced and completed in 1927. This time, the main construction work took place at ČKD, while Škoda and Tatra delivered several parts. It is unknown what happened to the two tractors after delivery.
It was decided to reconstruct and upgrade one KH-50, based upon the experience gained with the construction of the two KH-60s. It was transported to the ČKD plant at Slaný in 1927, while the other remained with the automotive artillery in Čtyři Dvory. The reconstruction was completed in January 1928, and the KH-50, now upgraded to KH-60 standards but often still referred to as KH-50, was handed over to the military. Testing of the vehicle took place between 17th and 19th January.
During testing, it became clear that the tractor was significantly improved. Steering, braking, and changing gears went better. Thanks to a lengthening of the wheelbase and the increase in speed, the driving experience was also improved. These improvements were reached, among other things, thanks to the installation of an additional independent brake, the reconstruction of the differential brake, and simplification of the steering and wheel drive. A handbrake test revealed that the vehicle while driving at its full speed of 36 km/h on-road, was able to come to a complete standstill within 20 meters. However, due to the changes, the weight significantly increased to 7,830 kg. In terms of weight distribution, 5,100 kg was pressed on the rear axle, and 2,730 kg on the front axle.
After these tests, it was decided to use the KH-60 chassis as the basis for a tank, construction of which began in the same year. Meanwhile, the other KH-50 remained with the automotive artillery in Čtyři Dvory, but it was discontinued in 1929 and disassembled. Several parts were kept by the automotive artillery for training purposes, like the gearboxes, and the engine. The engine proved particularly helpful, since the Regiment had no other spare engines available, and always had to remove one from an active vehicle to use as a teaching aid.
The Need For Tanks
Already in December 1918, efforts were undertaken to acquire the first tanks for the new Czechoslovak Army. The Renault FT was considered to be the best candidate and, after several years of discussion, one FT was bought, which arrived in the Czech city of Milovice on 14th January 1922. An additional four were ordered in 1923, and another two in 1924, totaling seven tanks.
Although a larger number of tanks was wanted (The FTs were only used for training and parades and not destined for regular units), Czechoslovakia did not intend to become dependent on a foreign supplier, and wanted to utilize its domestic heavy industry to develop and build their own tanks. A program set up in 1924 resulted in the purchase of two Praga MT prototypes in 1924 and one Plazidlo Votruba-Věchet prototype in early 1925. Neither design met expectations and the Czechoslovak Army still had no combat tanks available.
This impasse was criticized from various levels, but 1926 saw several breakthroughs. The Czechoslovak Intelligence Department made a report of the situation in the proximate countries of Austria, Hungary, Italy, and Romania. This report was later substituted by a report from the Military Technical Institute, which detailed and analyzed tanks from France, Italy, the United Kingdom, the United States, and the Soviet Union. Not only their construction was analyzed, but also their tactical deployment, and various classifications. A budget of CZK 5,760,000 was made available to construct a light assault vehicle, and a list of requirements was drafted:
1) Weight should be under 10 tonnes, 6-8 tonnes was desired.
2) Speed of 15-25 km/h on hard ground.
3) The armor should provide enough protection against bullets from infantry weapons and machine guns, and shrapnel.
4) Ability to overcome obstacles up to 2 m wide.
5) Climbing ability of 45°
6) Fording depth of 80 cm
7) Armed with one 75 mm gun and one machine gun, or alternatively, two machine guns. They should be able to rotate 360°
8) Crew of three
9) Action radius of 8-10 hours
10) The engine should, as far as possible, be able to run on a mixed fuel containing petrol, alcohol, and benzol, known as biboli.
In 1928, it was decided to use the Kolohousenka chassis as a base for a tank that largely met these criteria.
The KH-60 Tank
The first armored superstructure was mostly intended as a mock-up, and only thin steel plating was used. Much of the planned equipment was also not installed so, in order to compensate for the low weight, steel and lead weights were used to simulate heavier armor and equipment. After testing, the superstructure was removed and stored at the ČKD plant in Slaný, registered under the name of “mock-up KH-50”.
The design of the armored superstructure appears to be older and could already have been proposed by Joseph Vollmer when he offered his patents in 1923. In 1924, the same tank design was presented to the USSR when they bought the licenses for the WD 50 tractor. The Soviets never pursued this design, but the Czechoslovaks eventually did.
The metal body was of riveted construction, except for two headlights which were welded onto the hull, in a similar style as on the PA-II armored cars. The frontal appearance and the turret were similar to the design of the Renault FT. The driver sat in the front and could open a large hatch upwards, while two smaller hatches below it could be slid open to the sides. The turret’s front roof sloped upwards, and a large round-shaped cupola stood on top. On either side of the superstructure, below the turret, entry hatches were located, providing easier access to the crew. The engine could be accessed through hatches installed above the rear wheels on either side of the superstructure.
A novel feature was the installation of a device that overpressurized the crew compartment, protecting the crew from gas attacks.
The first Kolohousenka was armed with a 37 mm gun, often believed to be a d/27 infantry gun of Škoda. However, guns by Bofors and Vickers were considered, and a note from 16th December 1929 states that a Vickers gun was removed from the tank.
Experiences With The Tank
In January 1929, the KH-60 was present in Milovice. A report from February by the Military Technical Institute, requested by the Ministry of Defence, revealed that the KH-60 had been tested alongside the Praga MT and that the KH-60 exceeded the requirements set out earlier. It was recommended to continue testing with the KH-60 and also use it during the 1929 autumn maneuvers, and if these were successful, a platoon of five tanks could be purchased to use during the autumn exercises of 1931. The original requirement for armament of a 75 mm gun and a machine gun was deemed unnecessary, since the tanks would never operate alone, so a mixture of machine gun-armed tanks and gun-armed tanks should be fine.
The testing of the KH-60 tank continued until November 1929. During the same year, a new armored body was made, designed by the 3rd Department of the Military Technical Institute. On 16th December 1929, the Vickers gun was removed from the tank and relocated to the Instruction Battalion in Milovice. On the 17th, the tank was transported to the ČKD factory in Karlín, where the new armored body was to be fitted. The welded turret was of improvised construction. Until May 1930, the tank remained with ČKD and was tested in conjunction with the Military Technical Institute. This included technical tests, and firing tests against the armor. On 21st May, the KH-60 returned to Milovice.
After further refinements of the design, the last order for modifications of the armored layout was placed on 16th July 1930 by the Ministry, which paid CZK 35,338. It is unknown if this also covered the costs for the construction of a new turret. Until this time, the KH-60 was still officially in possession of the Automotive Artillery Regiment, but since it was repurposed, it was formally transferred to the Milovice-based Assault Vehicle Regiment on 11th October 1930, and assigned to the 2nd Armored Car Company. Unlike the earlier two designs, the last design featured a rear tail to improve trench crossing capabilities.
It was subsequently stored, and barely used. In the spring of 1931, the KH-60 and a Renault FT were ordered to perform comparative tests with new Carden-Loyd Mk.VI tankettes. These comparative trials took place on 25th March 1931, after which the KH-60 was put in storage. Some administrative changes occurred in December 1932, when it received the new registration ‘13.362’, and in September 1933, when it was reassigned to the Auxiliary Company. Since it had not been used in a long time, it was reassigned to the School of Assault Vehicles shortly after, on 5th October 1933. It remained with the school until the end of 1935 when its armor was removed and stored, while the chassis was re-registered as a school-aid. In September 1937, the school moved from Milovice to Vyškov, and took the KH-60 with them. There, it was found by the invading German troops when they occupied part of Czechoslovakia on 15th March 1939.
Other Tanks For The Army
Interest in the Kolohousenka already started to fade in 1929, especially after new Carden-Loyd tankettes were examined in Britain and three were ordered, which arrived in the spring of 1930. An extensive program was set up with ČKD, and four copies were built under license. An improved design, the P-I, was eventually taken into service as the Tančík vz.33 (Tankette 1933 pattern). By focusing on this new vehicle, the Ministry of Defense basically eliminated the Kolohousenka project, effectively ending some seven years of development. However, this development period proved to be very valuable for all parties involved, including the manufacturers, the government, and the military. It had provided experience in many fields, ranging from design to tactical deployment.
The Mysterious KH-70
In older literature on the topic, especially in the work of Charles K. Kliment, mention is made of the KH-70 tractor, an upgraded version with an even more powerful engine of 70 hp. It was supposedly sold to Italy. However, recent research was unable to verify the existence of a KH-70, while Italian sources provide no proof that Italy ever bought a KH-70 tractor. It has long been assumed that the latest design iteration of the KH-60 tank was the KH-70, but this appears not to be the case.
That said, in the German military magazine Militärwissenschaftliche Mitteilungen of 1936 (volume 67), it is mentioned that a KH-70 is under construction. Presumably, a wrong designation surfaced in contemporary military literature, and the designation has been stuck with historians since, though it may refer to a different vehicle entirely.
In the Spring of 1929, the Military Technical Institute ordered Tatra to develop a new wheel-cum-track tractor with a more powerful engine. The order for one prototype was signed on 15th May 1929, but the original deadline of December 1929 could not be met, and the vehicle was only delivered by the end of 1930. The tractor, better known as the KTT, was never taken into serial production.
A New Wheel-Cum-Track Tank
The decision to effectively eliminate the Kolohousenka project did not mean that all interest had been lost. In 1929, all companies involved in the project, Tatra, ČKD, and Škoda, were ordered to design a new wheel-cum-track tank. ČKD, involved in the new Carden-Loyd tank project, quickly gave up, while Tatra’s attempt, the T-III, was plagued with issues and unpromising. Škoda’s work was more successful, and a design was presented in 1931, the S.K.U. (also known as KÚV). During production of two prototypes, ordered in 1933, the system showed so many problems that in 1934, it was decided to ditch the idea of a wheel-cum-track tank for good. The tank was modified to a heavy breakthrough tank and work continued on the tank, now designated Š-III.
The RR-50 was originally designed by German engineer Joseph Vollmer, and although pretending to aim at the civil market, he certainly had military use in mind, provided he licensed his work to the Czechoslovak Ministry of Defence and even to the USSR. The first KH-50 experienced many teething problems, but the design was significantly improved with the KH-60. The external design effectively remained a ‘work-in-progress’ until the final design was presented in July 1930. However, by this time, the Ministry was already undergoing trials with the newly bought Carden-Loyd tankettes from Britain, and subsequently, the KH-60 project was canceled. The only tank prototype was effectively never used in its intended role but was useful as a teaching-aid. The chassis was eventually scrapped by the Germans after its capture in 1939.
KH-50 Tractor Specifications
|Total Weight, Battle Ready||6.8 tonnes|
|Crew||2 (Driver, Commander)|
|Propulsion||Hille K3, 4-cylinder, petrol, 8.22 liter, 50 hp (36.8 kW) at 1,100 rpm, 60 hp (44.2 kW) at 1,400 rpm|
|Bore / Stroke||115 / 150 mm|
|Speed with 50 hp at 1,100 rpm||Wheels 21 km/h, Tracks 14 km/h|
|Speed with 60 hp at 1,400 rpm||Wheels 27 km/h, Tracks 18 km/h|
KH-60 Tractor Specifications
|Total Weight, Battle Ready||7.83 tonnes|
|Propulsion||60-80 hp engine|
KH-60 Tank Specifications
|Dimensions (L-W-H)||4.50 x 2.39 x 2.53 (wheels) / 2.38 (tracks) m|
|Total Weight, Battle Ready||<10 tonnes|
|Crew||2 (Commander, Driver)|
|Propulsion||60-80 hp engine|
|Speed, Wheels On-Road||35 km/h|
|Speed, Tracks Off-Road||15 km/h|
|Range||300 km on wheels on road (186 miles)|
|Slope||100 % (45°)|
|Armament||2x 7.92 mm Schwarzlose vz.24 machine guns or 1x 37 mm gun (Bofors, Vickers, or d/27 Škoda)|
Špitálský, Jaroslav. 21st April 2021. “Od tzv. „Rade Raupen“ k bojovému vozu KH-60.” https://rotanazdar.cz/?p=9390&lang=cs.
Pasholok, Yuri. 22nd February 2018. “От «Теплохода «АН» к МС-1.” https://warspot.ru/11309-ot-teplohoda-an-k-ms-1. (translation)
Zincke, Gisela. 1990. “Oberingenieur Joseph Vollmer Chefkonstruktur des deutschen Urpanzers und Pionier des Automobilbaus.” In Sturmpanzerwagen A7V Vom Urpanzer zum Leopard 2, edited by Heinrich Walle, 93-115. Herford: Verlag E.S. Mittler & Sohn GmbH.
Francev, Vladimir, and Charles K. Kliment. 2004. Československa obrnena vozidla 1918-48. Prague: Ares.
Kliment, Charles K., and Hilary Louis Doyle. 1979. Czechoslovak armoured fighting vehicles 1918-1945. Watford: Argus Books.
Pejčoch, Ivo. 2009. “Czechoslovak heavy armored vehicles. Development, production, operational use and export of the Czechoslovak tanks, armored cars and tracked artillery tractors 1918-1956.” PhD diss., Karlova University. Pdf.
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