A punching machine makes 25 working strokes per minute and is capable of punching 25 mm diameter holes in 18 mm thick steel plates having an ultimate shear strength of 300 MPa. The punching operation takes place during $1/10^{th}$ of a revolution of the crankshaft. Select standard motor.

Determine suitable dimensions for the rim cross-section of the flywheel, which is to revolve at 9 times the speed of the crankshaft. The permissible coefficient of fluctuation of speed is 0.1. The diameter of the flywheel must not exceed 1.4m owing to space restrictions. Check for the centrifugal stress induced in the rim.

Given data

$k_{s}=0.1, D_{\max }=1.4 \mathrm{m}$

Assumptions - The cross-section of the rim is rectangular, flywheel material-CI with density $7250 \mathrm{kg} / \mathrm{m}^{3},$ width -b = $\mathrm{D} / 5,$ The hub and the spokes assumed to provide 5$\%$ of the rotational inertia of the wheel.

Solution