EXPERIMENTAL-OBSERVATIONS OF A FLEXIBLE SLIDER CRANK MECHANISM AT VERY HIGH SPEEDS

A slider crank mechanism has been constructed and operated for the pur pose of investigating steady state rod bending vibration induced by a very high speed crank. Features include a combination flywheel and adj ustable length crank, a thin aluminum connecting rod, and a piston sli ding on steel rod slide axes. A strain gage on the rod and magnetic pi ckup on the crank sensed rod strain and crank speed, respectively. For this system configuration, experimental results are categorized as sm all, intermediate and large crank length response. Small and intermedi ate cranks response was amplified due to a large superharmonic compone nt of twice the crank speed frequency and at crank speeds near 1/2 the first natural frequency of the rod. Beyond that speed, period doublin g occurred over a range of speeds for intermediate length cranks. The occurrence of period doubling was experimentally sudden and audibly no ticeable, and characterized by the onset of frequency components of 1/ 2, 3/2, 5/2, and 7/2 times the crank speed. For large crank sizes of 0 .5, 1, and 2 inches an amplified response also appeared in each at a c ertain speed, but at speeds lower than in the small and intermediate c rank cases. Larger cranks required more frequency components to descri be the response than smaller cranks. Experimental responses were corre lated with computer simulations of a one mode nonlinear ordinary diffe rential equation model, and over a wide range of speeds and for a repr esentative of a small, intermediate, and large crank length.