Tuesday, 22 July 2014

SU-85 and SU-57

I wrote about some of these light TDs before, but here is a document describing them in more detail.

"Report of results of a trip to the Molotov GAZ factory in the city of Gorkiy

Experimental work is being done on the following vehicles:
  • SU-85: an 85 mm D-5S-85A gun on the SU-76 chassis
  • SU-57: a 57 mm ZiS-2 gun on the SU-76 chassis
  • KSP-76: a 76 mm ZiS-3 gun on the GAZ-63 chassis
  • Automobile mount of a 76 mm ZiS-3 gun on a GAZ-AA chassis
1. SU-85 on a SU-76 chassis: Consists of an 85 mm D-5S-85A gun on a production SU-76 chassis. It differs in the following ways:
  1. An 85 mm gun is mounted.
  2. The engines are turbocharged to 85 hp.
  3. Planetary final drives are used.
  4. Shock absorbers are installed in the front and rear.
  5. The rear armour hinges downwards.
  6. The return idlers are removed, and replaced with a runner.
  7. The size of the porthole is increased.
The tactical-technical characteristics of the vehicle are as follows:
  1. Mass: 12 tons
  2. Crew: 3
  3. Length with gun: 5500 mm
  4. Maximum speed: 35 kph
  5. Average speed on dirt road: 20 kph
  6. Average speed on highway: 28 kph
  7. Ground pressure: 0.54 kg/cm^2
  8. Effective hp/ton: 14.2
Armament
  1. Gun: D-5S-85A
  2. PPSh: 2
  3. 85 mm shells: 40
  4. Maximum gun depression: -5 degrees
  5. Maximum gun elevation: +15 degrees
  6. Horizontal traverse: +/-12 degrees
  7. Bore axis height: 1670 mm
  8. Periscopic sight: Hertz panorama
  9. Telescopic sight: TSh-15
Engine
  1. Type: GAZ-203F
  2. Maximum hp: 2x85/3600
  3. Gearbox: ZiS-5 type with reinforced roller
  4. Final drive: 2-stage cylindrical pair with a planetary mechanism, ratio 1:7.8
Suspension
  1. Tracks: T-70 type
  2. Number of teeth on drive sprocket: 16
  3. Type: Torsion bar, with additional shock absorbers on rear and front.
The other parameters of the SU-85 are identical to the SU-76. A prototype was manufactured and underwent trials. Trials were satisfactory. Assembly of a second prototype is in progress and will be delivered to trials on June 25th, 1944. In case of successfully completed trials, the factory can begin mass producing the vehicle without much difficulty in 0.5-1 month.

2. SU-57 on the SU-76 chassis: The prototype has been built. The electric firing mechanism has not been tested. The factory has scheduled gunnery trials."

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