In the punch press shown in Fig. 9.78a, a slider-crank mechanism with flywheel is used to punch holes in steel plates. A hole is punched for each revolution of the flywheel, which operates at an average speed of 300 rpm. The load Poo the punch during punching is the force necessary to shear the plate, and the variation of punching force with shearing deformation of the plate is shown in Fig. 9.78b. For the maximum size of plate and hole to be punched, it is estimated that 3200 ft. lb of work is required to punch the hole and that the punching is accomplished in one-sixth of a revolution of the flywheel. Figure 9.78c shows the torque diagram for one cycle of punching. Determine the following:
(a) the average crank torque for one cycle;
(b) the horsepower required of the motor;
(c) the required moment of inertia of the flywheel for a minimum speed of 280 rpm just after punching.
