Gerotor motors have been in the rotary power transmission market for over 35 years. Rolland Nielson reviewed their usage and potential in his 1977 SAE 770771 paper (1) which was written 20 years after Lynn Charleston introduced the first hydraulic motor based on the principle of the orbiting rotor and stationery stator. Fifteen years prior to Nielson's paper, Hollis and Harvey White introduced valve plate commutation for this orbiting rotor and stationary stator gerotor motor. Also, ten years prior in 1967 Ross Gear, TRW, added stators with rollers to the orbiting rotor, statonery stator, and valve plate commutation gerotor motor.
Gerotor motors of today have become the hydraulic motor power source of choice by providing performance, quality, and price to satiate the challenges of today's highly stressed managers, design engineers and CEO's with world wide markets for their products.
This paper is a discussion on the evolution of the gerotor motor from being a low horsepower, price only device to a sophisticated, high performance, computer controlled rotary power source.