Sunday, 1 June 2014

Planetary Transmission for the T-34

"To the GBTU Chief, Lieutenant-General of the Tank Forces, Vershinin

The Academy, on its own volition, developed a technical project for a planetary transmission for the T-34 tank. In this project, one component successfully unites a gearbox and a two-stage turning mechanism. Using this mechanism, thanks to the increased number of gears (six), short distances between high gears, and a friction (knock-less) gear activation, significantly improves the mobility of the tank. The turning is improved due to the two-stage turning mechanism.

A selector device for switching gears decreases the time needed for a shift, due to which the average speed of the tank increases. 

The proposed design is superior to existing single-type planetary transmissions with identical characteristics. This project was discussed at the tank faculty meeting, where it was positively received. I include a copy of the project and ask that it be implemented at experimental factory #100. At the same time, I send two copies to the Deputy People's Commissar of Tank Production, Major-General of Technical Forces, comrade Kotin.

Academy Chair, Major-General of Tank Forces, Kovalev
Acting Chair of the Experimental Department, Engineer-Major Shain

MINUTES of the meeting of the tank faculty at the Stalin Academy of Mechanization and Motorization, Order of Lenin, on March 30th, 1943.

Topic of the day: a project for a planetary gearbox for the T-34. Presenting: designer Solovyev. Co-presenting: Engineer-Lieutenant-Colonel Ivanov

Engineer-Lieutenant-Colonel Antonov: Everything is thought through well, down to the adjustments. You should increase the spread of gears more. I must remark on the difficulty of using such a gearbox. The project is at the height of modern tank design. It must be recommended for production.

Engineer-Lieutenant-Colonel Prokofyev: I have a very good impression of this project. I agree with comrade Antonov, the gearbox must be built. If there is a chance, decrease the 1st gear. Retain the maximum speed. This is a very original design.

Engineer-Captain Baranov: These designs are not new. Earlier, things never went past the design stage. I must remark that building and installing this gearbox will be hard. We must work hard to push this project through. Building this gearbox will require a higher level of production culture.

Engineer-Captain Meyerfeld: The gearbox is original, we must build it. Do not be afraid of its complexity. Our tank factories are capable of building it.

Engineer-Colonel Gruzdev: Of course, the simpler the mechanism the better, but in some cases, more complicated mechanisms cannot be avoided. For a good medium speed, a tank either needs a high powered engine that causes the driver's work to be more complicated, or a more complicated gearbox. There is no question that the transmissions in our tanks are becoming obsolete. What is an obstacle on this issue?

First, it is conservatism. The conservatism of factory engineers that see any external proposal as an impedance. 
Second, it is the fear that the increase in complexity will reduce the amount of vehicles built. Specifically for planetary transmissions, the issue raised is the lack of gear-cutting machines, they are the bottleneck. We can build a gearbox like in the PzIII, where there is a minimum amount of gears, one to one, but then there is a complicated selector, which will be no less complicated to produce than a planetary gearbox.

We can stop with a simple synchronizer, but even in the Valentine, switching from a high gear to a low one is hard. This will be even more noticeable on the T-34 and KV.

The faculty managed the first step, the use of a ChMKD type turning mechanism, we must make the second step, the faster the better. If it is difficult to set up mass production, we must at least build one batch of 10-20 vehicles.

Conclusion: the T-34 planetary gearbox is realistic, matching modern tank development. Ask the Academy command to begin work with the factory on its production."


  1. Did it end up being put in the T-34 afterall?

    1. I suspect not, since AFAIK to the end they were still using clutch and brake steering.