Core Technology

The Sanderson mechanism represents a major paradigm shift in applications of all types and sizes that require conversion of linear to rotary motion, or vice versa. 

Using a unique, patented rocker arm solution to transfer linear thrust to rotary motion, it applies to any device currently using a crankshaft, bent axis, swash plate, or wobble plate.

Because the design advantages also apply to conversion of rotary to linear motion, the mechanism applies equally to pumps, compressors, electric generators, electric motors, and hydraulic systems as well as engines.

Description of the S-RAM

The S-RAM is a recent invention that uses a new principle to convert reciprocating to rotating motion, producing equally high efficiency in both directions. The application of the S-RAM to engines, fluid pump/motors, and air compressor/motors, through actual prototype testing, has demonstrated the substantial advantages of this low-friction device.

Low friction in hydraulic devices leads to high overall system efficiency, low heat generation, and virtually zero slip-stick.  The operation of the simplest form of S-RAM, showing only a single piston for clarity, is shown in Figure 1.

	Figure 1 – This drawing of the Sanderson Rocker-Arm Mechanism illustrates the method of turning rotation into reciprocation (and vice versa), with just one piston, one cylinder, and one rocker arm.  Adding multiple axial pistons around in a coaxial circle increases the capacity of the mechanism, but still only requires one U-joint, one nose pin and one crank.

The piston is attached to one arm of a 90° rocker arm, through a joint designed to allow only a force parallel to the piston axis to reach the piston. The side-load forces on the piston are therefore zero by definition. The corner of the rocker arm is attached to a conventional universal joint, grounded on one side. This ground supports all of the output torque — none of it goes to the piston. 

The other end of the rocker arm, which carries the nose pin, has to follow the reciprocating motion of the piston as projected on the reciprocating plane; but the U-joint also allows the nose pin to move at right angles to the reciprocating plane. The nose pin can therefore trace a circle, and can thus be connected to the offset crank on the output shaft to complete the mechanism.

Note that while this kinematic description applies to one piston; the design can accommodate as many pistons as can be arrayed in a circle and will physically fit. They all share the same U-joint, nose pin, and crank, but each has its own 90° rocker arm and piston joint, at a phase angle equally spaced with respect to the other pistons.

Rocker arms are far more efficient than swash or wobble plates at transferring energy, and do not exhibit slip-stick. All S-RAM engines, hydraulic motors and pumps share these properties with rocker arms.