. A punching machine makes 24 working strokes perminute and is capable of punching 30 mm diameter holes in 20 mmthick steel plates having an ultimate shear strength of 350 MPa.The punching operation takes place during 1 10 th of a revolutionof the crankshaft. Find the power required for the driving motor,assuming a mechanical efficiency of 76%. Determine suitabledimensions for the rim cross-section of the flywheel, whichrevolves at 9 times the speed of crankshaft. The permissiblecoefficient of fluctuation of speed is 0.4. The flywheel is to bemade of cast iron having a safe tensile stress of 6 MPa and density7250 kg/m3. The diameter of the flywheel must not exceed 1.05 mowing to space restrictions. The hub and spokesmay be assumed toprovide 5% of the rotational inertia of the wheel. Check for thecentrifugal stress induced in the rim.
