Masttyazhart AA Daimler
In 1925, as a part of the Mechanization and Tractorization of the Army program, Masttyazhart (Heavy Artillery Workshops) installed a 76.2 mm Model 1915 AA gun on a Daimler tractor (the model was not specified). The gun could rotate 360 degrees, had an elevation of up to 75 degrees, and depression of 0 degrees. The tractor towed a cart with 192 rounds of ammunition and a crew of six. It could only fire while stationary, with spades deployed. The vehicle was not mass produced.
SU-2 and SU-5
The SU-2 self propelled gun was developed in 1931, at the Bolshevik factory. A 76.2 mm model 1902 divisional gun was mounted on a Kommunar 9GU tractor, behind an armoured shield. The gun could rotate 360 degrees. The tractor chassis had to be reinforced, and the driver's seat removed, in order to fit this modification. Armour thickness of the hull was 10 mm. The 75 hp engine accelerated the vehicle up to 12 kph. One of these vehicles was built. The vehicle had a crew of five.
In 1932, another, project at the Bolshevik factory put a 76.2 mm model 1915 AA gun on the same tractor. To compensate for the extra weight, the vehicle had no armour, and had four spades deployed when firing. One of these vehicles was built and passed trials, but the project was not continued due to the insufficient capacity of the Kommunar chassis to support 76.2 mm guns. This vehicle was designated SU-5, not to be confused with the SU-5 light triplex on the T-26 chassis.
NI, or Na Ispug (For Fear) was an improvised armoured vehicle, produced in Odessa. A STZ-5 tractor was equipped 10-20 mm of armour, or even mild steel with wooden boards, which would protect it from bullets. Armament varied based on what was available. NI tanks went into battle with 37 mm or 45 mm guns, 1-2 DT machine guns, sometimes only with a pipe to simulate a cannon. Some sources say that a 76.2 mm model 1938 mountain gun was used. The idea of the tank was not to combat other tanks, but to combat infantry, unprepared for the arrival of tanks, and lacking anti-tank weapons. The loud noise produced by this contraption contributed to the psychological impact of the tank. 55 of these tanks were built. The name NI was given to the after the war. During the war, they are designated as "tractor-tank". Three NI tanks exist to this day, at least one a reproduction for movies.
Kharkov's approach to an armoured tractor was similar, but more uniform. A STZ-3 tractor was chosen for the job. It was equipped with 10-25 mm of armour, a 45 mm gun for enemy tanks, and a DP machine gun for enemy infantry. The turret of the tank did not rotate. Unlike with the NI, the HTZ-16 was set to be mass-produced, but problems with supplies limited the total production run to 60 at Kharkov and 30 at Stalingrad. At least one tank made it through the war and returned to its life as a tractor.
CAMD RF 38-11355-190, a record of a meeting on turning obsolete tanks into tank destroyers, proposes installing the 57 mm ZiS-4 tank gun and, 37 mm and 25 mm automatic AA guns in the STZ-5 tractor "with extended hull and ZiS-16 engine". Meeting notes from Factory #92 list "SU-2-2, 57 mm tank gun on the fast artillery tractor STZ-5" as a potential option for production. However, this option was not chosen.
The same document proposes installing an 85 mm AA gun on a Voroshilovets tractor. The project was deemed unlikely, but launched at Factory #8 under the index 105-K anyway. A prototype was built, but not mass produced, due to the army's lack of heavy tractors.