Question

In line-shaft driven product machinery, torsional deflections and vibrations of the camshaft due to the time-varying torque of various cams can cause synchronization problems between the various stations on the machine. We need to design a testing machine that will measure the torsional vibration effects of dynamic torque loading on a camshaft. This machine will accommodate two cams, each of which will drive its own spring-loaded translating roller follower on a slider mechanism at speeds up to 300 rpm. These cams will be designed to give approximately opposite torque-time functions to one another. They can be used singly or in pairs to investigate the effectiveness of the addition to a production machine of a torque-balancing cam that drives a dummy load. The cams will be split to allow removal and installation without disassembling the shaft. The torque-time and follower force time functions for the primary cam are provided as an excel file P09-20 on the books website. The secondary cam will be a mirror image of the primary cam to approximately balance the torque. The camshaft in this test fixture must be designed to have torsional deflections that are large enough to be measured by 5000 count per revolution, optical shaft encoders attached at each end of the camshaft, but not so large as to fatigue fail the shaft. At the same time, we want the camshaft to be stiff in bending and have a bending natural frequency at least 10 times its torsional natural frequency to minimize any coupling effects between bending and torsional modes. Stated another way: what should the shaft diameter be to give sufficient torsional deflections to be measurable under the designed loading conditions, but not to create undesirable bending deflections or vibrations. Plain bearings should be used to avoid vibrations that would come from rolling element bearings. The test machine will be driven by a speed controlled PM DC motor through a gear reduction unit of your design. Motor selection is also your responsibility. What is required is a detailed design of a camshaft torsional vibration test machine including the camshaft, keys, follower trains, bearings, couplings, gearbox, frame and mounting hardware. infinite life is desired.

Answer 1