For finding out the bending moment for the arm (spoke) of flywheel, the arm is assumed as

Explanation:

The rotating rim of a flywheel is subjected to a uniformly distributed centrifugal force Pc, which acts in a radially outward direction.

The following types of stresses are induced in the flywheel rim.

• Tensile stress due to the centrifugal force
• Tensile bending stress due to the restraint of arms.

The tensile stress due to the centrifugal force is determined in a similar way as a thin cylinder subjected to internal pressure.

The tensile bending stress due to the restraint of arms is based on the assumption that each portion of the rim between a pair of arms behaves like a cantilever beam fixed at the rim and subjected to a tangential force at the rim.

The rim is subjected to tensile stress due to P and bending stress due to M. The resultant stresses in the rim are given by,

\({\sigma _t} = \frac{P}{A} \pm \frac{{My}}{I}\)

or \({\sigma _t} = \frac{P}{{bt}} + \frac{{6M}}{{b{t^2}}}\)

Where,

P = Tensile force in the rim, M = Bending moment on rim section, b = width of the rim, t = thickness of the rim