Insane Hydraulics

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Running a Sauer Series 20 Without The Thrust Plate

Sauer Series 20 axial piston closed loop pumps - classic series that's been on the stage for the last... well, I am not sure for how many, but maybe more years than I have on my shoulders.

Despite the fame, immortality, and the fact that this field-fire-and-water-proven design is well known, every once in a while a skillful individual happens to work on a series 20 pump for the first time in his life, and occasionally omits a part of two during the assembly. Such predicaments are of great benefit to this website because they give practical answers to purely theoretical questions like "what would happen to my pump if I forgot to mount the ... (insert a part name)?".

This particular example is about part number 29, namely the thrust plate (check out the exploded view and the cutaway drawing), which was "accidentally dismissed" during an overhaul. Without it, the piston slippers are forced to work inside the thrust plate cavity of the swashplate, which starts to "rectify" the shape of the bronze slippers as soon as the swashplate tilts to its maximum angle.

It took only five minutes of "work" to give the piston shoes the new "rounded appearance". The pump was stopped because of the "very unusual noise" it was making and the fact that it couldn't reach nominal pressures.

So, now you know what happens to a Sauer series 20 pump when you run it without a thrust plate!