Czechoslovakia (1936-43)
Amphibious Light Tank – 2 Prototypes Built

In 1933, ČKD (Českomoravská Kolben-Daněk) built the Tančik vz. 33 (P-I), however they were not pleased with the design and started a project on their own which would become the LT vz.34 (P-II) light tank of which fifty were made. These P numbers of the vehicles designated the type of tank. I stood for tankette where II stood for Light tank, however this second category got split up into IIa and IIb in 1934, respectively standing for cavalry tank and infantry tank, so ČKD started designing and came up with the P-IIa and P-IIb in 1936


First prototype outside factory. Photo: rotanazdar.cz

Development

In October 1936, both Škoda and ČKD received orders from the Czechoslovakian Army and the VTLÚ (Vojenský technický a letecký útvar or Military Technical and Aerospace Institute) to develop the first Czechoslovakian amphibious tank. During the same year, ČKD started development and on January 29th, 1937, they delivered two alternative designs to the MNO (Ministry of Defence) which were based upon the already developed P-IIa and b tanks. With no previous amphibious tank design experience and a lack of available foreign assistance, the design process proved difficult. Engineers in Great Britain and the Soviet Union had experience with amphibious designs, but due to a deteriorated relationship with the Soviet Union, caused by the armed conflict between the Bolsheviks and Czechoslovak Legions, and a negative view of British amphibious tank designs, neither were asked to assist.

On April 28, 1937, the commander of the VTLÚ, Ing. Dr. František Kolařík wrote in a report to the MNO: “The amphibious tanks designed by the two companies are based on experience gained in manufacturing and testing light tanks, tracked tractors as well as various river vessels. Regarding the overall concept of the amphibious tanks designed by ČKD, they are both respectively based on the P-IIa and P-IIb prototype tanks, with the exception of the engine and the way the drive and gear assembly are designed. (…) The disadvantage of all projects is the need to have very tightly strung tracks when driving on ground, resulting in a considerable loss of engine power during movements and little ability to adapt to unevenness. The hull is designed with sufficient buoyancy for swimming. Each project has two propellers, which are driven by the drive axle by the ČKD projects, but the Škoda project uses a special transfer directly from the engine. Changes in direction should be performed by disengaging the drive or reducing the speed of one or the other propeller, according to ČKD, or, according to Škoda, by disengaging the propulsion of one or the other bolt or the counter-flow of one of the propellers. The ČKD project is assessed to be better suited because its whole unit is mounted at the rear of the vehicle and completely separate from the combat compartment.

After considering both proposals, the VTLÚ recommended that prototypes should be ordered from both companies, because of the difficult production of amphibious tanks and lack of experience building them. Because ČKD handed in two proposals, a choice had to be made. After comparisons, the second proposal was chosen as it had more favorable characteristics. On November 12, 1937, the MNO ordered the construction of a prototype for the price of 718.000 CZK (nowadays around $350,000). In the order, it was also stated that the prototype had to be delivered before August 12, 1938.

Work on the prototype ran until the spring of 1938. The first reports appeared on April 26 when 16 technical drawings of the vehicle were realized. The number of schematics became bigger and bigger with 47 drawings on June 30 and already a total of 262 drawings on August 6. On August 20, work on the details began and by September 13, a total of 401 schematics had been produced. The deadline was extended by the MNO to 12 October, giving two months extra time.

On October 19, the deadline was again extended to the end of the year. Two liquidation orders were proposed if the tank eventually could not be delivered. Firstly, at least a part of the tests had to be paid either by the company or the military administration. Secondly, if any tanks would be sold abroad, a percentage fee of the price would be requested for intellectual property by the government. At the start of the next month, a report came in from Libeňská Engineering that a total of 415 drawings had been made and work on all the details in the mechanical workshops progressed quickly.

By November 17, the deadline was extended again until January 12, 1939. Four days later, a conference was held at the Ministry of National Defence about the amphibious tanks. The attendants came to the conclusion that the programme shouldn’t be stopped and negotiations had to continue. The percentage fee of intellectual property had to be determined after receiving and testing the vehicles from both Škoda and ČKD, due to delivery delays.

One month later, on the 7th of December, the first engine tests were launched with both alcohol-petrol mixtures and ‘dynalkolem’, a mixture of 50% fermented alcohol, 30% benzene, and 20% gasoline. After about 4 hours, a problem occurred with the electric brake, but six days later everything worked as it was supposed to and the tests were successfully completed.

Next year, on January 25, Libeňská Engineering reported that the vehicle was working. Some months later, in April, it was announced that the vehicle was in running condition and had been tested by the factory in the river Moldau in Prague, but wasn’t officially been tested by the military. Meanwhile, work was still being done on an observation device. After the German annexation of Czechoslovakia in March 1939, work continued on the project and the German military also showed interest in the project.

From 2 to 6 May 1939, representatives of the company, which was renamed Böhmisch-Mährische Maschinenfabrik AG (BMM AG), had negotiations with the German Heereswaffenamt or German Weapons Agency. The German committee consisted of Oberstleutnant Fichtner, Dr. Olbricht, Major Tomala, Oberst Reg. Baurat Beier en Oberst Reg. Baurat Mosel. During these negotiations, it became clear that the F-IV-H wasn’t ripe for serial production and further internal testing at the factory had to take place. This request was approved, but the test results had to be sent to the German WaPrüf 6. WaPrüf is the abbreviation from ‘Waffenprüfamt’or ‘Weapons testing office’. Several of these offices formed the Heereswaffenamt. BMM AG tried to offer the F-IV-H abroad, but the German military administration blocked this and marked the project as secret.

On May 23, the Czech “Ministry of National Defense in Liquidation” extended the delivery time to 31 July. Within delivery time, on June 22, the National Engineering Research and Testing Institute, the former VTLÚ, was informed that the prototype was ready for testing. The formal reply suggested that the company should notify the German army. They indeed showed further interest and on November 2, a second prototype was ordered, which bore the name F-IV-H/II. The factory was visited by Mr. Keiling on behalf of WaPrüf 6 a month later. He promised that the prototype could remain for demonstration purposes. During the same month, the company received permission to offer the F-IV-H abroad, however, the vehicle wasn’t ordered either by the Germans or foreign countries and further development was canceled.

Meanwhile, the Škoda ŠOT had also been built and tested, but it was reportedly too heavy and could barely maneuver in the water. It is not known when the first ČKD prototype was scrapped. The second prototype was sent to Kummersdorf, where it was tested. The last trace of this vehicle was found in early 1943 when new tracks and pins were ordered, but by this time, further development had already been canceled.


First prototype without floatation skirts. Photo: rotanazdar.cz


Illustration of the ČKD F-IV-H by Tank Encyclopedia’s own Jarosław Janas

Design

Initially, ČKD came up with two alternative designs. The first design was propelled by a conventional six-cylinder water-cooled engine, with an output of 95 hp at 2000 rpm. The second design was propelled by a four-cylinder water-cooled engine with an output of 100 hp at 2000 rpm. Both alternatives had an vertical exhaust pipe, which would limit the turret traverse. The second alternative was chosen.

The crew consisted of three people; The commander/gunner, driver and a radio-operator. The driver was located in the right front of the tank and had a sight with bulletproof glass. The radio-operator sat to his left and the commander was located in the turret.


F-IV-H front interior. The driver sat to the right and the radio-operator to the left. Photo: rotanazdar.cz

The chassis was a heavily modified version of one used by the famous LT vz. 35 tank. Power was distributed through a Praga-Wilson gearbox with four road wheels and two return rollers on each side. The engine was a Praga F4 water-cooled 4-cylinder producing 120 hp at 2200 rpm. Two propellers were mounted at the rear of the vehicle and connected to the drive axle. The armament consisted of only a 7.92 mm ZB-37 machine gun, located in the turret. Frontal armour was 14 mm thick and the top and bottom armor plates were 7 mm thick.

The differences between F-IV-H prototype I and II were minor, with the II having a slightly modified turret, a lifted cupola, a better cooling system, a redesigned floating system and a new exhaust system.

Export

At the end of 1939, offers were sent to Sweden, Persia and the Netherlands. The export model received the designation F-IV-HE and was described as a fast and easily manageable combat vehicle. The armor could withstand bullet fire, even at a distance of 100-150 meters. It was suitable for both terrain or water maneuvers. The factory also stated in the offers that 20 to 25 units could be delivered per month within a maximum time span of five months.

Of the three contacted countries, only the Persian War Ministry and General Staff showed interest. In April 1940, a technical description with additional photographs was sent and further communication took place via Berlin. It was assumed that Persia would buy around 200 vehicles, including a few F-IV-H vehicles. In the end, Persia ordered only twenty vehicles and this order didn’t contain the F-IV-H. It is possible that this is due to a lack of interest of the Persian War Department, but it’s more likely a result of a restriction from the German department. Later on, a new offer was sent to Argentina, but they showed no interest either.

Conclusion

Despite the efforts of the engineers, the F-IV-H was not a successful project. The Czech army was skeptical about it because of the long delivery period and when it was tested, it did not perform as planned. Although the German continuation of the project the vehicle was still not suitable for combat and in the early stage of the war already outdated. Both prototypes were scrapped during the war.


The F-IV-H second prototype. Photo: rotanazdar.cz

ČKD F-IV-H specifications

Dimensions (L-W-H) 4.85 x 2.5 x 2.08 m (15.9 x 8.2 x 6.8 ft)
Total weight, battle ready 6.5 t (14,330 lbs)
Crew 3 (commander, driver, radio operator)
Propulsion Praga F-IV, 4-cylinder, 120 hp
Speed 45 kph / 28 mph – road, 6 kph / 3,7 mph – water
Range 200 km / 125 mi
Armament ZB vz. 37 7.92mm machinegun.
Armor 7-14 mm / 0.28 – 0.55 inches
Total production 2 Prototypes

Links, Resources & Further Reading

Czechoslovak armoured fighting vehicles 1918-1945, H.C. Doyle, C.K. Kliment
On Aviarmor.net
On tanksinworldwar2.com
On utocnavozba.wz.cz
On rotanazdar.cz
Google maps view of where the water testing took place, libeňský zámeček (libeňský mansion) HERE

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