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"In machinery, a form of slip-coupling applied in cases where the variations of load are sudden and great, as in dredging-machinery, etc. In the form illustrated a strong pulley, B, is keyed on the driving-shaft, and on the circumference of this wheel, A, is fitted, with a series of friction-plates, a, a, a, interposed, and retained in recesses formed in the eye of the wheel." -Whitney, 1911

Friction Wheel

"In machinery, a form of slip-coupling applied in cases where the variations of load are sudden and…