CZK - VOŽ (VOŽ-2)

The headquarters of the Engineer Army ordered the development of a heavy amphibious car in a decree of the Ministry of National Defense on September 4, 1950. The program was referred to as VOŽ (Big Amphibian). In the early stage of this program, the contracting authorities had the idea that it would be a three-axle amphibian using a chassis Tatry 111. The vehicle was to be similar in construction to the American DUKW. It was supposed to be a vehicle capable of carrying a load of 3-4 tons, respectively. 75mm cannon with ammunition and crew. The program VOŽ was transformed in 1951 into a pair of design proposals into a four-axle wheeled vehicle ([ url=/topic/view/223294] VOŽ-1[/url]) and tracked vehicle (VOŽ-2). The reason was that the three-axle construction based on the chassis of the truck V3S can not meet the required specifications. According to the decision of 10.8.1951, the project VOŽ-1 was to be worked on in 1952, the development of VOŽ-2 was to be postponed to 1953. However, it was already clear in this period that the required specifications will not be met. VOŽ-1 would not reach the required sailing speed of 12 km/h and would not have favorable driving characteristics in the field. In the meantime, there were disagreements between the company and the army. The company refused to take over the role of VOŽ for 1952 (probably due to lack of capacity). In the end, however, it agreed with the army to complete the project VOŽ-1 for the year 1952. The proposal VOŽ-1 was a company Tatra Kopřivnice np submitted for approval on January 30, 1952, but due to deficiencies in the design, the proposal was not approved.

For the controversy about which type of chassis will be more advantageous, the head of the VTÚ ordered Tatra Kopřivnice n.p. to perform comparative tests in order to find out which construction (wheeled or tracked) is more advantageous. The German half-track artillery tractor Sd.Kfz took part in the tests. 9, american half-track M 14, German four-axle off-road vehicle Büssing ( Sd.Kfz.234?) And tank destroyer ST-I. The belt version proved to be more advantageous, and after the approval of the VTÚ and Soviet advisers, work on the VOŽ-2 belt probably began on March 24, 1952.
There were even two belt amphibian designs. The design based on the artillery tractor DTH 1 of the ČKD company ended in failure. It would be a lightly armored tractor weighing 6,500 kg, which would be able to tow 5,260 kg in a tow. The tractor should drag a pontoon behind it on a two-axle chassis. The pontoon would have its own auxiliary engine with the ship's deed and steerable wheels. It would weigh 3,500 kg and the load would also weigh 3,500 kg. The pontoon would be controlled by the crew with the help of the rudder. The connection of individual pontoons was considered. Due to the low speed of the voyage and the poor driving characteristics of the pontoon lift in the terrain, this proposal was rejected.
Development focused on the second version, whose design, however, exceeded the parameters set by the military. Therefore, the proposals VOŽ-1, as well as both proposals VOŽ-2 at the meeting of 28.5.1952 were not approved. Again, development on a standard truck chassis was required. However, he had to meet the requirements of the army, which were, however, slightly reduced. Only the chassis V3S came into consideration, but the company Praga could not accept this project due to capacity reasons. At the same time, however, the long-term development of the belt version VOŽ-2 and the company Tatra Kopřivnice n.p. submitted a draft on July 2, 1952. We managed to reduce the dimensions for which the project was criticized.
On July 21, 1952, a meeting was held on VOŽ, where the proposal for a wheel version of V3S was rejected after several objections.Although the belt version of the VOŽ was criticized, a consensus was reached, the construction requirements were reduced and the proposal was essentially accepted with comments. However, there were constant requests to change the parameters. The details of the construction were addressed, eg the engine used, the belts, the method of loading and unloading the vehicle, etc. Endless negotiation and changes in the requirements led to disproportionately prolonged completion dates. The final project was officially approved on May 21, 1954. The prototype was to be delivered in 12/1954. Before that, however, a wooden model of the upper deck was to be made in order to verify the concept of loading and unloading. The model was manufactured and tested on July 21-23, 1954. The tests concerned the loading of anti-tank cannons ( 57 mm PTK vz.43, 85 mm PTK vz.52), mortar caliber 120 mm, prototype off-road vehicle Škoda Š -973 and truck Tatra 805. Later, there was a request to transport a truck Praga V3S, but Tatra did not respond at all, because it was an unrealistic request, the fulfillment of which would lead to the return of development to the beginning.
I will give some details of the construction. The engine was a proven diesel tank V-2, the radiators came from the tank T-34/85. The clutch was made of parts from the Tatra 111, the transmission was 6-speed (Of which two gears were reverse). The driver's and crew's areas were to be heated by heated engine air in the winter. The engine was located in the rear of the vehicle, which was the biggest and probably fatal weakness of the vehicle. The vehicle was moving on metal belts with removable rubber feet. Their width was 550 mm. The chassis consisted of a drive wheel at the front, a tension wheel at the rear, seven double castors with a rubber band and three support rollers. The wheels were suspended by torsion bars. The pair of propellers rotated at speeds of up to 1200 rpm, could be switched to reverse and their blades could be adjusted at different angles. The vehicle had a 6-ton winch and a 50-meter-long rope in the front. The hull was waterproof and partially armored. There was a lifting floor in the cargo area, which made loading and unloading easier.
The prototype, meanwhile, redesignated the T-807 was completed on 31.12.1954 and immediately 1.1.1955 tests began. Their evaluation was discussed on September 26, 1955. During the tests, several failures occurred, mainly the transmission and cardan shafts. These disorders were easily eliminated. Due to the soft suspension of the chassis, the diameters of some torsion bars were increased. The adjustable blades of the propellers immediately tore off during the first voyage and therefore fixed blades with different degrees of inclination were tested. The most preferred angle of inclination was 45 °. Additionally, the necessary breakwater was mounted. A number of technical shortcomings were promptly resolved and the prototype was handed over in 2/1956 for control tests of the military administration, which were later extended by comparative tests with the Soviet belt amphibian K-61. The exams began in 3/1956 and lasted until 9/1956. The prototype T-807 proved its qualities, declassifying the Soviet counterpart in most indicators. The biggest advantage of the Soviet K-61 was its better designed cargo space, which allowed trouble-free loading of the car V3S. The transport of the V3S to the VOŽ was tested and was possible, but it was a very risky matter beyond the design characteristics of this vehicle. There were suggestions for further development, which would include this advantage of the Soviet type. At the end of 1956, this possibility was still being discussed, but in 1957, the requirements of the Engineer Command changed so much that a new vehicle would have to be developed. The VOŽ program was thus quietly terminated and its planned use was represented by imported Soviet types of amphibious vehicles.

After successful mastering, the VOŽ program was to be extended to include the development of a crawler artillery tractor (task U-9254), an armored personnel carrier BOPAS a amphibious tank LETÁK. Due to the failure of the entire VOŽ program, these associated development branches also fell.

Mgr. Martin Dubánek - From bayonet to jet - Unfinished Czechoslovak weapons projects 1945-1955, Mladá fronta 2011, ISBN: 978-80-204-2515-7
Mgr. Martin Dubánek - VOŽ, HaPM No.3/2008, ISSN: 1210-1427

In 1954, tests of the prototype VOŽ Tatra 807 (large amphibious car on belts) took place, when the first rides, field and water tests were carried out.

Tatra trucks, MS Press Publishing House, 2004

* edit (Braňo)
The photograph must come from tests on the Danube in a period of about half of 1956. The prototype was completed on the last day of 1954.