Soviet tank design underwent a tremendous period of experimentation during the 1930s and this work begat such designs as the "T-24", a medium tank of great promise for the period that was ultimately let down by its reliability issues. Just 25 of the tanks were produced and none remained in service by the time of World War 2 (1939-1945).
Origins of the T-24 set it in the late 1920s when the Locomotive Works (Kharkov) took up design of a new medium tank based in the earlier T-18 and designated the T-12 in prototype (pilot) form. When tested in 1929, this design proved a failure but, with changes to its drivetrain and fuel delivery scheme, was modified to become the T-24 of 1930. The new design was evaluated into 1931 to which point some twenty-five examples had appeared. However, these early-form tanks lacked the 45mm main armament until 1932 due to general unavailability of the weapon system in the numbers required.
Structurally, the T-24 showcased a weight of 18,500 kilograms with an overall length of 5.7 meters, a beam of 2.8 meters, and a height of 3.0 meters. The riveted hull was given some angled facings for basic ballistics protection and armor ranged from 8mm to 20mm in thickness. A crew of five was stuffed into the cramped fighting compartment of the tank that included the primary turret and a smaller, cylindrical turret at the turret's roof (offset to starboard side). The engine was fitted to a compartment at the rear of the hull, leaving the middle-to-frontal portions of the design free for crew spaces and ammunition storage. An anti-ditching structure was fitted to the rear of the hull - a throwback to World War 1 (1914-1918) tank design.
Internally, drive power was provided for by a single M-6 8-cylinder engine developing between 250 and 300 horsepower to a traditional, multi-bogied track-and-wheel arrangement. Suspension was of vertical springs. There were eight small double-tired road wheels to each hull side, two pairs to each of the four total bogies. The drive sprocket was at front with the track idler at the rear and three track-return rollers were used to guide the upper run of track-links about. Road speeds could reach up to 25 kph (16mph) and the tank ranged out to 140 kilometers.
Armament was the typical 45mm cannon of the Soviet Army, giving a good punch against enemy armor for a 1930s design. Up to three 7.62mm DT machine guns were fitted for anti-infantry work - one in the front-left bow, the other coaxially in the frontal turret face, and the final unit installed in the smaller, independently-rotating, turret set atop the primary turret. Overall, the T-24 carried excellent firepower for a tank of the period, capable of engaging enemy armor at range while closing in with a battery of machine gun fire against infantry.
Despite all of the investment in the T-24 design, it too proved itself something of a failure for its reliability issues could not be worked out. The design was dropped from further development and serial production, leaving just the aforementioned 25 units in existence. These were used in training and second-line roles for the duration of their service lives in the Soviet Army.