If you look closer at this Sauer Danfoss series 51 end cover, you will discover some foreign object damage inside the maximum displacement side of the servo-cylinder.
The most impressive thing is the foreign object itself, or better, two objects, that happen to be two small steel balls! Apparently they spent some time smashing around the servo-cylinder cavity and leaving these stylish round marks!
At this point there's no explanation on where the balls came from. The
only ball of a similar size can be found inside a spool in the
multi-function block (older series), and it was in place. In any case,
if the balls came "with the oil", they would have had to pass the
control spool before entering the servo-cylinder, which seems
improbable... Miracle? Sabotage? Accident? Coincidence?
There's one thing that we all can learn from this -
nothing good comes out from putting balls inside a hydraulic motor! IH strongly advises you not to! Balls belong...well..somewhere else.
