Which type of Cup is the best?
A good pump and differential cup should
- be on-size (exactly the same size as the pump (or differential) cylinder)
- be shaped to suit the pump Plunger (the Alderdice Pump has a scalloped seat on the Plunger Block and Spacer)
- be permeable (so water can penetrate through the material and therefore lubricate the sliding surface)
- have good friction characteristics
- have a lubricant built in.
- expand for its own wear.
It is only leather that satisfies all these requirements. Neoprene (which are actually made
from nitrile) and Nitrile Cups will last longer, but they tend to cause the windmill to operate
under an increased load. The Cups last longer but the windmill doesn’t.