RGASPI 558-2-128, a letter from the Kirov factory director to Stalin.
"On the production of fast T-28 and T-29 tanks in 1936
I reported on October 6th, 1935, that T-28 tanks produced in 1935 include improvements to their construction that increase the speed by 50%, by 16-20 kph on average.
The new speeds gives new value to the T-28 as a medium tactical unit and opens great potential for further improvements.
Meanwhile, ABTU RKKA is proposing shutting down the production of these vehicles in 1936, shifting over to convertible drive T-29s. They forget that it will take 4-6 months of hard work to produce as many of these vehicles as we now produce T-28s, in the meantime, no new T-28s or T-29s can be built.
This transition not only weakens the mobilizational readiness, but once again puts the Kirov factory in a position of having to learn to produce a new vehicle, and take 1-2 years to perfect the process.
As worldwide automobile and tractor manufacturing experience shows, technical progress moves in the direction of perfecting existing products of the factories.
The speedy T-28A vehicle, with a maximum speed of 65 kph and average speed of 48 kph surpasses the average speed of the T-29, which is 42 kph on tracks and 39 kph on wheels.
You can see that the T-29 is still inferior to the T-28A in its tactical characteristics, requires further design refinements, and the former cannot be viewed as a vehicle that is capable of replacing the latter. Until today, tank specialists did not think it possible that heavy vehicles could survive lengthy high speed runs due to wearing out tracks and breaking track links.
The T-28A was equipped with experimental tracks, and cast track links show good results. We can also guarantee a high speed distance of 1000 kilometers with the T-28A using stamped tracks.
Due to the above, I firmly maintain my opinion that the T-29 should not be put into production given its current construction, and I ask for your personal directive to retain the T-28 tank in production at the Kirov factory, with the improvements that have already been performed, and will be performed later."
Let's read some more about these improvements to the T-28.
"The T-28 has been produced at the Kirov factory since 1933. Over the past 3 years, design and production changes increased the combat capabilities of the vehicle. The T-28 had a maximum speed of 45 kph, and an average speed of 30 kph on a good road.
At the end of 1935, due to initiative shown by SKB#2 engineers comrades A.P. Efimov and O.M. Ivanov, changes to the suspension have been made, as a result of which, the T-28 will be capable of a much higher top speed.
As a result of energetic work by engineers, mechanics, and assemblers, the experimental vehicle was ready for the 18th anniversary of the October Revolution. The vehicle passed factory trials, showing a top speed of 65 kph, and an average speed of 46 kph. This speed is an unsurpassed record among heavy tracked vehicles in the world.
The tracks and road wheels, previously weaknesses of the tank, showed high reliability after changes to their design. The changes made to the vehicle drastically increase its combat performance and maneuverability, and will be applied to all T-28s produced at the Kirov factory in 1936.
Next year, one T-28A vehicle will be produced above quota, with increased speed, an improved turret, and an AA machine gun mount.
In order to further improve the vehicle by making it easier to drive and quieter during motion, we will design and produce a vehicle based on the T-28 medium tank with a steam-powered engine and convertible drive."
This is a photograph of what is likely the last T-29, on the territory of factory #100 in Chelyabinsk, in 1942. According to the factory's documentation, it was recycled in 1943 along with several other experimental vehicles, including the KV-7.