"To Chief of the 6th Department of BTU, Engineer-Major Voroshilov
On the condition of the KV-13 as of September 30th, 1942, I report that:
- On September 26th, the first factory trial began, a 20 km march. All components of the transmission and suspension worked well. Oil pressure dropped to 2 atm. as engine RPM increased due to a defect in the oil reductor valve. The defect was corrected after the trial.
- On September 27th, a second trial was scheduled, a 25 km march. The following defects were discovered:
- Worsening of the gearbox actuator on the 30th kilometer.
- Three road wheel hubcaps were lost.
- The water in the cooling system is hot, reaching 110-115 degrees with a temperature of 10-12 degrees outside.
- Controlling the tank is difficult.
- The engine does not increase RPM in 9th gear and works poorly.
- All other tank mechanisms worked satisfactorily.
- An M-1 car following the tank was used to gauge its speed. At 1800 RPM in 9th gear, the tank runs at 55 kph. This is almost the same as the estimated top speed (57.6 kph using a T-34 track).
- Examinations after the trial showed the following:
- The loss of hubcaps was caused by a design defect in the ball bearing in the wheel axle. The wheel could move along the axle relative to the ball bearings and hit against the hubcap. Not able to withstand the force, the hubcap bolts were torn off and the hubcap fell off and got lost. The design of the ball bearing in the wheel axle is being urgently reworked.
- The gearbox actuator worsened due to a knocked off calibration of the main clutch. It was discovered that it is not possible to calibrate the main clutch without removing the radiator.
- Difficulty in controlling the tank can be explained by necessary force of 60 kg on the levers and 90 kg on the main clutch pedal. The servo mechanism of the main clutch works poorly. The design of the controls is being urgently reworked.
- The hand gas lever does not allow the third position of the multiplexor lever to be used.
- The tachometer panel hits the driver's hand when the right lever is pulled to the maximum.
- The air filter cannot be removed for cleaning without removing the oil radiators.
- The turret travel lock disengages during movement.
- The locks on the firing ports are unusable.
- The track tightening mechanism travel is short and does not sufficiently tighten the tracks.
- The balancer is attached weakly and can be turned.
Aside from the above, many small and easily correctable defects were discovered.
Most defects discovered during assembly, trials, and inspection after trials are corrected. Designers are making new blueprints with corrections to the tank's weaker points.
The tank should be disassembled for improvements and corrections of discovered defects.
GABTU Military Representative, Engineer-Major Fedoseev."