Among the more serious problems in the design of high-pressure pumps of the axial-piston type are those relating to the main thrust bearings. At least two bearings in each pump are subject to the full thrust of the pistons under pressure and the swash-plate configuration results in the load on the bearings being off-centre as well as alternating in magnitude. Since the power loss associated with these bearings represents the major proportion of the total mechanical loss in a pump, it must be kept to a minimum.nIn all pumps thrust loads arise between the rotating member and the stationary case, as well as between the pistons and the swashplate. With variable-delivery pumps the cylinder block rotates, in which case it is usual to combine the thrust bearing with a face-valve at the end of the cylinder-block.
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