T - 50 tank The T - 50 light infantry tank was built by the Soviet Union at the beginning of World War II . The design for this vehicle had some advanced features , but was complicated and expensive , and only a short production run of 69 tanks was completed . Furthermore , even before it was ready for mass - production wartime experience invalidated the underlying concept of light tanks . Production history . The T - 50 was a light tank developed on the eve of World War II for the Red Army . The experience of the Spanish Civil War led to an effort to upgrade or replace the large Soviet tank fleet . Prior to 1939 , most tanks in Red Army service were improved versions of foreign designs . For example , the most numerous tank , the T - 26 light infantry tank , was a copy of the British Vickers 6 - Ton tank with a Soviet - designed turret and 45 mm gun . However , just prior to and during the war , the USSR developed new light , medium and heavy tanks of wholly indigenous design . The T - 50 light tank was intended to replace the T - 26 infantry tank ; in prewar planning , the T - 50 was intended to become the most numerous Soviet tank , operating alongside the BT fast tank . Development of the T - 50 started as the SP project ( " Soprovzhdeniya Pekhoty " , ‘ Infantry Support ’ ) in 1939 at the OKMO design bureau in the S . M . Kirov Factory Number 185 in Leningrad , under the direction of , and headed by , L . Troyanov and I . Bushnevov , to create a light tank replacement for the T - 26 and BT tanks . Initial prototypes , called T - 126 and T - 127 , were not much improved over the T - 46 - 5 project which had been abandoned earlier that year , but the heavier T - 126 was selected for further development . The design bureau was gutted during the Great Purge , and was unable to continue the project , so it was transferred to the K . E . Voroshilov Factory Number 174 in Leningrad , May 1940 , where two prototypes from the Voroshilovsky and Kirovsky factories were tested . The first 2 vehicles were finished at Factory No . 174 in Leningrad in late 1940 . Troyanov completed the T - 50 design in January 1941 . After a few modifications it was ready for delivery in April 1941 . Production was then authorized , but due to technical problems , it was unable to proceed . In the meantime , a replacement for the BT fast tanks was developed and built at the KhPZ factory in Ukraine , which exceeded its original programme . The result was the very capable and economical T - 34 medium tank . After the German invasion , Operation Barbarossa in June , tank factories were ordered to be transferred to the Urals . Part of OKMO was moved to Omsk after September , and production was finally begun . The T - 50 was of an excellent design , but still suffered from technical problems , and at that time was found to be as expensive to produce as the more capable T - 34 . Much simpler T - 60 light tanks were already being mass - produced . A total of 69 T - 50 tanks were built ( only 48 of them armed ) , before production ended in January 1942 . Some further infantry tank design work on a prototype , called the T - 45 , continued at Factory Number 174 and the Kirovskiy Factory Number 100 . But faced with the need to accelerate T - 34 production , and due to a lack of interest from troops in the field , the Soviet infantry tank concept was abandoned . Description . The T - 50 was an advanced design for its time , with torsion - bar suspension , diesel engine ( in common with all the new Soviet tanks ) and well - sloped , all - welded armor . An excellent feature was the three - man turret with commander ' s cupola , which would not appear on other Soviet tanks until 1942 . Most Soviet tanks of the 1939 - 43 era had either one - man or two - man turrets , which are far less efficient in combat than three - man turrets . Additionally , all T - 50s had radios , a feature only found on the commander ' s vehicle in earlier models . However , the T - 50 had several weaknesses ; to begin with , like many Soviet tanks , it was very cramped inside . The main problems , however , were related to the new V - 4 engine developed specifically for this tank , unlike other Soviet light AFVs , which used standard truck engines . The T - 60 and T - 70 light tanks and the SU - 76 self - propelled gun used standard GAZ truck engines . Specialized tank engines , being more expensive to produce , were reserved for higher - performance vehicles . The very mobile BT - 8 fast tank , the T - 34 medium tank , KV - 1 , the IS - 2 heavy tanks , and their derivatives all used variants of the same standard 12 - cylinder model V - 2 diesel engine . The V - 4 engine was extremely unreliable , and the design flaws could not be worked out . The engine ' s low reliability and high cost contributed to the demise of the T - 50 . Variants . There were two variants ; a basic model and an up - armored model . Just prior to the German invasion of the USSR , many Soviet tanks had their armor reinforced with welded or bolted add - on plates . Some Kliment Voroshilov heavy tank s , T - 28 medium tanks and T - 26 light tanks received add - on armor fittings . A few T - 50s also received these add - ons . This up - armored variant is recognizable by the bolt heads that hold the armor added to the turret sides and hull front . The normal T - 50 is a very ' clean ' looking vehicle by comparison . The uparmored T - 50 had 57 mm of armor at its thickest points . Combat history . The few T - 50s available were deployed on the Leningrad front . Few in - service photos survived and not much is known of their combat record . One uparmored T - 50 was captured by Finnish forces and was used by them in 1944 . This unit survived the war and is now on display in Finland . On paper , the T - 50 should have been easily able to hold its own against any early - war German tank ; however , paper specifications cannot always predict real - world performance . Most light tank production in 1941 – 43 consisted of the less advanced but simpler T - 60 and T - 70 light tanks . By 1943 , the infantry tank role was considered obsolete , and cheaper SU - 76 self - propelled guns took over the light infantry support role . Light tanks in tank regiments were being replaced by T - 34 medium tanks . The liaison and reconnaissance roles of light tanks were assumed by cheaper armoured cars and Lend - Lease supplies of Canadian and British Valentine tank s and U . S . M3 Stuart light tanks . Surviving T - 50s . Today , at least two T - 50s survive . One is at the Finnish tank museum at Parola . This is a later model with bolted - on appliqué armour . A standard T - 50 is on display at the Kubinka armor collection outside Moscow . Scale models of T - 50 . As most of the serial WWII tanks T - 50 exist as scale model in different scales . In 1 / 35 it ' s offered by Mirage , they offer two versions - early and up armored . In 1 / 72 T - 50 is available from OKB Grigorov , they also offer two versions , early tank build in Leningrad , and late one build after the evacuation of the factory in Chkalov .