11. A cast iron flywheel is to be designed for asingle cylinder double acting steam engine which delivers
150 kW at 80 r.p.m. The maximum fluctuation of energy perrevolution is 10%. The total fluctuation
of the speed is 4 per cent of the mean speed. If the mean diameterof the flywheel rim is 2.4 metres,
determine the following :
(a) Cross-sectional dimensions of the rim, assuming that the huband spokes provide 5% of the
rotational inertia of the wheel. The density of cast iron is 7200kg/m3 and tensile stress 16 MPa.
Take width of rim equal to twice of thickness.
(b) Dimensions of hub and rectangular sunk key. The shear stressfor the material of shaft and key is
40 MPa.
(c) Cross-sectional dimensions of the elliptical arms assumingmajor axis as twice of minor axis and
number of arms equal to six.
