The variable-stroke radial-piston pump (fig. 13-14) is similar in general principle to the axial-piston pump, but the arrangement of components is different. In the radial-piston pump, the cylinders are arranged radially in a cylinder body which rotates around a nonrotating central cylindrical valve. Each cylinder communicates with horizontal ports in the central cylindrical valve. Plungers or pistons, which extend outward from each cylinder, are pinned at their outer ends to slippers which slide around the inside of a rotating floating ring or housing.

The floating ring is constructed so that it can be shifted off-center from the pump shaft. When it is centered, or in the neutral position, the pistons do not reciprocate and the pump does not func-tion, even though the electric motor is still caus-ing the pump shaft to rotate. When the floating ring is forced off-center to one side of the pump shaft, the pistons reciprocate and the pump operates. If the floating ring is forced off-center to the other side, the pump also operates but the direction of the flow is reversed. Therefore, the direction of flow and the amount of flow are both determined by the position of the cylinder body relative to the position of the floating ring. For further information, refer to Naval Ships Technical Manual, chapter 556, and the NAVSEA technical manual for your unit.