Compliant Overrunning Clutch

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Overrunning clutches, also known as freewheel clutches, transmit torque in only one direction and are used extensively in various applications. These applications include vehicle transmissions, engine starters, agricultural equipment, helicopters, and bicycles, where a one-way torque transmission is necessary. Typically, overrunning clutches have been employed in these areas for their efficiency. Several types of overrunning clutches exist, but the primary four variants comprise the sprag clutch, roller or ball clutch, spring clutch, and ratchet and pawl clutch. The design most closely resembles the ratchet and pawl clutch, which was developed by the Compliant Mechanisms Research Group at Brigham Young University under the guidance of Dr. Larry Howell. The advantages of using a compliant overrunning clutch include lower part counts compared to alternative designs, easy assembly and maintenance, reduced wear on parts, low cost, simplicity, and minimal lubrication requirements. However, disadvantages exist such as difficulty in manufacturing due to extremely thin segments, the need for non-linear analysis methods, and noise generation when clutch teeth rotate past compliant parts.