Design of hydraulic motors with a radial arrangement of pistons. Radial piston motors are predominantly slow speed high torque motors in which several pistons are positioned perpendicular to the drive axis and are arranged in a star formation in a cylinder block. As with radial piston pumps a distinction is made between internal and external pressurization in the designs.
Radial piston motors with internal pressurization:
These are always multi-stroke hydrostatic motors,, where the cylinder block is generally stationary and the housing (which has a fixed connection to the stroke ring and the central distributor pin) rotates (Figure R 2). The pistons generally perform 6 to 12 strokes/rev, which results in displacement that is too great for the task.
Radial piston motors with external pressurization:
In this case, the stroke movement is created by an eccentric tappet on the drive shaft. Each piston therefore only performs one stroke/rev. The large displacement (torque) is achieved here using large piston diameters. The oil is distributed via control rings in the shaft extension (Figure R 3).
Figure R 2: Radial piston motor with internal pressurization
Figure R 3: Radial piston motor with external pressurization