Thursday 21 November 2013

Tsyganov's BT

Some of you may have seen a pretty crazy tank model, designed by Soviet engineer Tsyganov.

You may also have read that it could achieve a great speed, over 100 kph! This was possible through the very complicated suspension system:

"February 10th, 1935 Top secret

Memo attached to the "BT" project designed by comrade Tsyganov, 4th tank regiment

This design of the BT tank proposed by the 4th tank regiment alters the method of the vehicle's movement, and has advantages over earlier designs, such as:

  1. With the same speed of the chain (track) or, which is the same, the wheel, the tank has a speed that is twice as high as a regular tank with a caterpillar track.
  2. Using a chain of wheels instead of a mechanical track, the tank does not knock its track links against the ground, and moves quietly.
In this design, the track moves half as fast as the vehicle. Due to this, the energy required to move at 100 kph is equal to the energy previously required to move at 50 kph on regular tracks. 

The wheels are held by flexible tracks, which, for additional flexibility, are made of separate segments with ball and socket joints. The suspension is made with leaf springs, one immobile, and two for balance, which let individual track segments hug the ground. In order to make movement smoother, the tank's tracks are rubber on the outside, and steel on the inside. 

This design does not require a more powerful motor, as the existing 400 hp motor is powerful enough. Subsequent reasoning is provided in the form of mathematical calculations. The calculations are made using data extracted from the works of professor Zaslavskiy, professor Chudakov, and other authors with materials relevant to the design of such vehicles."

I will leave out the math, as whoever will benefit from it probably doesn't need a translation to figure it out. I'll extract some useful figures, though:
  • Maximum chain wheel RPM: 422
  • Minimum chain wheel RPM: 58.5
  • Maximum chain speed: 14.5 m/s
  • Minimum chain speed: 2 m/s
  • Maximum tank speed: 104 kph
  • Minimum tank speed: 14.4 kph
  • Combat mass: 12 tons
Then, the design of the track chain and upper leaf spring is shown. Designs of other suspension elements are shown further in the memo, but this is all I have. 

"Regimental commander Hong
Regimental commissar Zubenko
Calculations by engineer Bessonov

City of Kharkov"

Several of Tsyganov's projects were accepted and built, but not this one, due to its complexity.


  1. I'm still not quite clear on how this works. The wheels are between two sets of tracks?

    1. From the looks of it the wheel-chain effectively form an inner "track" and the "rubber band" outer track goes over that. I'm guessing the latter had teeth on the inside that went into the central depressions of the former (acting as track guides or whatchamacallit) and interfaced with teething in the big wheel at the very rear to get power?
      Guessing further that both the outer track and the inner wheel-chain pseudo-track (via the projecting hubs slotting into the first drive wheel at the rear) were powered, as it's hard to see how the setup would work properly otherwise.

  2. Minimum tank speed: 14.4 kph

    Maybe i am misunderstanding but i dont get how the above works.
    From absolute standstill it will jump to 14.4 kph as the lowest possible speed it can traverse ?
    Seems like a crash waiting to happen.

    1. Lowest gear maybe? :/

    2. Seems awfully fast to start out with and i would not want to drive through an army camp or *gasps* a woodland area if that is the lowest speed it can go.

  3. Pretty useless, as the torque is halved.