Monday 27 August 2018


"To the Chief of the 11th Department of the ABTU

Summary of experimental work performed at the T-2O plant in December of 1938
January 3rd, 1937

1. Installation of remote control equipment on BT-7 tanks

One BT-7 tank with remote control went through factory trials. The vehicle made two outings, travelling 200 km during each one. The first trial was not completed due to loss of air pressure. Pressure was lost because the hose leading from the air tank to the compressor burst and the liner of the air cylinder of the final drive was punctured. 
The second trial was not completed due to a breakdown of a differential gear. The following drawbacks were recorded during trials.

  1. A lack of gradual control of final drive clutches means that brakes are activated suddenly and the vehicle is thrown from side to side.
  2. The granularity of control of the throttle results in the tank gaining speed in uneven bursts after shifting from bottom to top gear, and jerks the vehicle suddenly when switching from top to bottom gear. The controls only up the throttle when switching directly from top to bottom gear. When switching is done through neutral gear, in order to reduce speed, then the throttle does not increase and the gearbox gears grind.
  3. The signal lights in the commander's console do not work.
  4. The electric circuit allows the commander to switch gears as long as the driver's console is functional.
 Issues with the remote control make controlling the tank difficult, and its speed is low as a result. Presently, the equipment is being installed on two more BT-7 tanks.

2. BT-8 vehicle trials

Two vehicles were assembled. One vehicle began trials, but after driving for 100 km was sent back for repairs due to the cooling fan breaking. After switching out the fan, it drove for 1 km, after which the fan broke again. The second vehicle had two breakdowns of the fan during testing on the conveyor belt and thus did not enter trials.

3. Gearbox trials

Trials of four BT-7 tanks with Doroshenko and Morozov 3-speed gearboxes continue. The M-17T engines on all four tanks were completely unrestricted. As a result, the tanks completed trials with the following distances travelled.

Overall distance (km)
Counted distance (km)
Average speed (kph)
Average technical speed speed (kph)
Average tactical speed speed (kph)

  1. The difference between the overall distance and counted distance is explained by several instances where vehicles would travel less than 100 km in one outing. This distance was not counted.
  2. None of the vehicles reached the required average technical speed (30-35 kph). All vehicles are undergoing special trials. Out of four vehicles, two were subjected to factory trials. Of those, the vehicle equipped with Morozov's gearbox travelled for 5015 km, and the second vehicle with the same gearbox travelled 3505 km. Since plant T-2O can't deal with the volume of work, trials were performed at irregular intervals.
4. Trials of new track designs
  1. Low profile track with 22 mm track pin diameter. One pair of tracks travelled 646 mm, the second 834 km.
  2. Mass production track with special graded tooth travelled for 372 km. Trials ended due to breakdown of the drive wheel. The breakdown occurred due to jamming of the tracks.
  3. The 8-eye track with the production track pin, where, due to the increase in size of the eyes, the track pin is held by 6 mm rivets inserted into the edge eyes. One pair of these tracks travelled for 1048 km after two reassemblies. The second pair travelled 656 km after one reassembly and was then removed from trials due to tearing.
  4. Trials of tracks designed by engineer Tarshinov (209 mm pitch compared to 254 mm of the production version, graded tooth, two-piece 18 mm track pin, pins are held by 6 mm rivets). The track travelled for 156 km, trials continue.
5. Trials of two "300 series" BT-7 vehicles

Trials of two "300 series" BT-7 vehicles were completed.
Vehicle #435-07 travelled for 1801 km, of those 135 on wheels, before breaking of the bevel gear and pinion. 
Vehicle #435-07 travelled for 1086 km, of those 139 on wheels, before breaking of the bevel gear and pinion. 

The progress of experimental design work agreed upon after the 1st military trials is described in the annual report.

Assistant Military Representative, Military Engineer 3rd Class, Olkhovskiy
Checked by Senior Military Representative, Military Engineer 3rd Class, Petrov"

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