Soviet heavy half-track artillery tractor – AT-14 (abbreviation means “artillery tractor”). In summer 1942 two enterprises (ZIS and NATI) received the order to develop at three months artillery prime mover for heavy and super-heavy cannons (14 t trailers) because of great shortage of such tractors in heavy artillery units. To speed up the development of new half-track Soviet engineers decided to use engine and transmission from the serial ZIS trucks and chassis from the serial light tank T-70M. As for the engine – it was planned to use twin ZIS-5 or twin ZIS-16 with 146-176 hp total because of absence of serial powerful truck engine.
Engineers from NATI developed the half-track prime mover with two parallel ZIS-5M engines and special gearbox, also the second project of such half-truck, but with single 150 hp NATI MB-27 engine existed. Both projects were abandoned because of experimental, not serial gearbox and 150 hp engine.
Engineers from ZIS (general engineer – B.Fitterman) developed the half-track AT-8 for tow the 203mm howitzers. AT-8 had two ZIS-5M engines, each for its own caterpillar moving. The transmission didn’t have the differential gear and for turning the half-track the original vacuum gearing of throttle control of each engine was used. That increased the cross-country ability and could simplify the serial production of AT-8 also. In December 1942 the experimental AT-8 was built and tested during spring-summer 1943. In autumn 1943 two modernized AT-14 were produced. AT-14 had two parallel ZIS-16 engines with two standard radiators, but common cowl. Two gearbox (with common driving) and cabin (more wide) were taken from ZIS-5 serial truck, some elements of transmission – from American lend-lease “Studebaker” truck, the caterpillars and rollers – from T-70M light tank (AT-14 had additional bearing roller in comparison with AT-8 ).
AT-14 was tested for a long time during the winter-autumn 1944 as the completely unique half-track. Its specifications: weight 8 t + 2.5-3 t load + 14-20 t trailer; crew 2 + 15; dimensions 6,535 x 2,550 x 2,410 m; track 2,12 m; width of caterpillar – 36 cm; clearance 38,5 cm; unit pressure 0,502 kg/sq.cm; engine 2 x ZIS-16 with 161 hp total; speed 35 km/h; range 225 km. AT-14 showed excellent cross-country ability and was very maneuverable for its size and weight. The fuel consumption was low and AT-14 could move with only one engine, which was very necessary at the front line. As for disadvantages – AT-14 was bulky and not very reliable, didn’t have a winch and was quite hard in driving by inexperienced driver. It was recommended to serial production, but only 10 were produced (with first two experimental) because of arrival of lend-lease American tractors “Allis-Chalmers”, equipped with winches.