Compliant Overrunning Clutch - 3D printed 

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Overrunning clutches, or freewheel clutches, are used in applications which require torque to be transmitted in only one direction. These clutches have traditionally been used in applications such as vehicle transmissions, engine starters, agricultural equipment, helicopters, and bicycles.There are several variations of over-running clutches, but the four main types include the sprag clutch, the roller or ball clutch, the spring clutch, and the ratchet and pawl clutch. This design most resembles the ratchet and pawl clutch, and was produced by the Compliant Mechanisms Research Group at Brigham Young University, under the direction of Dr. Larry Howell.
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This overrunning clutch can be 3D printed or milled.
Advantages of using a compliant overrunning clutch:
-lower part count than alternative designs
-easy assembly and maintenance
-reduced part wear
-low cost
-simplicity
-less lubrication required
Disadvantages:
-difficult to manufacture due to very thin segments
-requires non-linear analysis methods
-noisy (when clutch teeth are passively rotating past compliant part)