Monday 10 December 2018

Servo Controls

"Act #013, composed on May 15th, 1940

The current act is composed by:
  • Bureau "540" researcher comrade I.S. Tomashpolskiy
  • Senior ABTU military representative at the Comintern factory, Captain P.F. Rusakov
  • ABTU military representative at department "500" comrade P.P. Baikov
  • Drivers from plant "530" comrades I.G. Bitenskiy and N.F. Nosik
  • Bureau "520" designer P.P. Vasiliev
to certify that preliminary mechanical trials of mechanical servo devices for control of an A-34 vehicle #311-18-3 were performed from May 12th to May 15th, 1940.

The servo device was designed by bureau 520 designer comrade P.P. Vasiliev and installed in the vehicle based on the author's directions, without installation blueprints.

The proposed servo system eases the effort the driver must apply to levers with the aid of a mechanical system (unlike the earlier pneumatic system), thanks to the actions of the levers and assistance springs. The servo acts when the final drives are disengaged or when the brake ribbons are tightened by the levers. In addition, a change to the return spring on the brake control rods reduced the effort applied to the brake pedal.

During trials between May 12th and May 15th the vehicle travelled 278 km on sand and dirt roads. Within that range turns and figure 8 maneuvers in 1st and 2nd gear were performed on dirt roads and in sand.

No defects in the mechanical servo device were observed during trials. The opinion of all commission members that took part in driving the vehicle, specifically the experienced test drivers, was that the proposed device of the mechanical servo on the A-34 does not require special skills or training to operate, does not cause exhaustion during driving, and does not require special calibration or difficult maintenance.

The effort applied to final drive clutches was measured with a dynamometer as follows:
  1. On hard dirt:
    1. 1st gear 360 degree turn in place: 18-24 kg
    2. 2nd gear 360 degree turn with minimum radius: 16-22 kg
  2. In shallow sand:
    1. 1st gear 360 degree turn in place: 18-30 kg
    2. 2nd gear 360 degree turn with minimum radius: 20-30 kg
Effort applied when turning in 3rd or 4th gear did not exceed 15 kg.

  1. Based on the information obtained during trials, the commission considers it reasonable to introduce the designs proposed by comrade Vasilyev into production for the A-34 instead of the pneumatic system, as it completely satisfies requirements, specifically:
    1. It is simple to produce.
    2. It does not require complex maintenance.
    3. It does not require special skills to operate.
    4. It does not tire the driver during operation.
  2. The commission deems it necessary to equip a trial batch of A-34 vehicles with mechanical servo devices instead of pneumatic.
  3. Bureau 520 must ensure maximum robustness and resistance to wear for components when producing final blueprints.
  4. In addition to the above, the commission considers it necessary for plant #540 to produce one or two sets of servo devices for reliability trials.
May 17th, 1940"

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