The bizarre machine was called the "Tzar-tank" and designed by N. N. Lebedenko. No earlier construction seems to have been his model (or maybee a paddle-wheel boat) and two pro- totypes were built in 1915. It was probably the largest and heaviest (40 tons) tank made anywhere at the time. Two huge wheels were driven by one 250 hp motor each and a pair of minor supporting wheels were placed in the rear. The two machine guns were placed outside the wheels. This photo and the drawings (link below) give different shapes and positiosn of the crew's cabin. The bad trial (they were stuck in the mud) and heavy costs closed the project in 1916. The photo above shows a wreck without supporting wheels. The last of the two units was dismateled for scrap in 1923.