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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.
Advantages of using a compliant overrunning clutch:
-lower part count than alternative designs
-easy assembly and maintenance
-reduced part wear
-less lubrication required
-difficult to manufacture due to very thin segments
-requires non-linear analysis methods
-noisy (when clutch teeth are passively rotating past compliant part)
The colorful model shown in the images above was printed with purple, blue, and black PLA filament. ABS or other filaments may be used, but PLA demonstrates the function of the clutch very well with the provided dimensions. The clutch teeth were made with an extruded cylinder to resemble a drive shaft and to facilitate functional demonstration.
The white model was cut out of polypropylene using a water jet, then was assembled with screws and an additional square top piece to facilitate functional demonstration.
Water jets, laser cutters, wire EDM, and milling equipment could also be used to produce the compliant overrunning clutch.
Compliant Overrunning Clutch made out of steel using wire electrical discharge machining (EDM)
Compliant Overrunning Clutch cut with water jet out of polypropylene
Compliant Overrunning Clutch with Centrifugal Throw-out
By Roach, G.M. , Howell, L.L.
U.S. Patent No. 6,148,979