Sometimes coupling with big bangs!

According technical specification the coupler has to resist a maximum coupling speed of 15 km/h. The wagon and the payload is shock-protected by the elasticity of the draft gears - but the bodies and the coupler themselves contact directly. It means, the speed raises in a very short time (about 1/1000 sec.) form zero to 7.5 km/h (theoretically) in the longitudinal direction.

An easy calculation make the problem clear:
Taking in consideration the speed-difference of 7.5 km/h = 2.08 m/s and the time-difference of 1/1000 sec. the acceleration a= 2.08/(1/1000)= 2080 m/s². This acceleration is about 200 times the acceleration due to gravity!

In reality the acceleration may exceed this result considerably because of combinations with additional vertical and horizontal components.

This showed sometimes curious test results. For instance breaks of bold-heads from the shafts by their own masses. Sometimes strengthening of parts worsen the test results.

But all these problems have been solved. Even in the cold of Siberia the coupler stands all tests.