80 formed in plates 36 and 38 are located to direct the discharge fluid into pool 90 and exhaust through passage 84 to opening 88 in the housing body 24 as shown in fig1 a second set of ports 80 is located diametrically opposite to balance the radial forces upon the shaft 34 and supporting bearings 153 and 154 as shown in fig1 and 2 fig4 a and 5 illustrate operation of the circumferentially continuous hydrostatic pressure pools 90 in accordance with this feature of the invention the arrows in fig4 a 5 and 6 schematically illustrate direction and magnitude of the fluid pressure distribution on the pressure plates adjacent to outlet openings 84 pools 90 are of largest radial dimension and therefore exert the hydrostatic force 90a against the outer surfaces of the pressure plates 36 38 to oppose the pressure distribution within the pump chambers it is also at this region adjacent to outlet openings 84 that the pressure distributions 54a 54c and 54d within the pumping chamber exerts the hydrostatic force against the inner faces tending to separate the pressure plates on the other hand adjacent to inlet passages 70 the pressure pools 90 are of smaller radial dimension and therefore exert a lesser hydrostatic force 90b against the outer pressure plate surface it is also in this region that fluid pressure distributions within the pumping chambers are smaller therefore.