1. A CYCLING DEVICE COMPRISING A CRANK, A ROTATABLE SHAFT, TIMING MEANS POSITIVELY MOVABLE ALONG SAID SHAFT DURING ROTATION THEREOF, CLUTCH MEANS DISPOSED ABOUT SAID SHAFT AND CONNECTED TO SAID CRANK AND ACTUATED BY SAID TIMING MEANS TO ROTATE SAID CRANK A SINGLE REVOLUTION ABOUT THE AXIS OF SAID SHAFT WHEN SAID TIMING MEANS REACHES AN EXTREME POSITION ALONG SAID SHAFT AND MEANS TO RETURN SAID TIMING MEANS TO AN INITIAL POSITION ON SAID SHAFT FOR COMMENCING ANTHER CYCLE.