Design of a Flywheel

flywheel (FW) is for storing Kinetic Energy (KE) for any reciprocating equipment ie. petrol, diesel or gas engine. even for reciprocating pump would require the same. the basic design norm is to have, most of the required flywheel effect at the rim of wheel, which results in lesser dead-weight, for the shaft on which it is mounted.

to make the flywheel (FW) of an overhung type, (for easy mounting and dismounting purpose), this is an important point to keep in mind. hence here, one is trying to keep a minimum weight of the flywheel (FW) and yet this satisfies for the Kinetic Energy (KE) required,for the equipment in mind.

the ribs of adequate strength will make flywheel lighter, as the weight nearer the hub, does not contribute much towards it's Kinetic Energy (KE) generation, by virtue of the flywheel speed. hence it is important to have strong enough hub at the center of FW and ribs in-between, to link the outer rim with hub, having sufficient mass that will generate the required Kinetic Energy (KE) for the speed limits you have given.

KE = W/g . ^ksquare. (where W = weight and k = radius of gyration),

and one should pick suitable units for the calculation.

the outside diameter of flywheel and its width may be decided by the constraining surrounded area near the engine etc. the rim cross-section may be square or rect angle or round depending upon which is easy for manufacturing.

I agree with most of chittaranjan's post but I am not 100% certain about the kinetic energy calculation

The kinetic energy in a rotating body is given by the formula

KE = ½ Iω²

Where I = moment of inertia

And ω is the angular velocity.

The units are important and with SI units the angular velocity is in radians per second mass is in Kg and distance in m.. The moment of inertia is somewhat complex and depends on the axis of rotation and the shape of the object. If you follow the link it will take you to some examples of the moment of inertia for several common shapes.

CORRECTION in Kinetic Energy:

I understand that the KE should be

KE = 0.5MK²ω²

where, M = Mass of the flywheel (Kg)

K = Radius of Gyration (metre)

ω = Angular speed (radians/s) = RPM x π / 30

RPM = Angular speed in (Revolutions/Minute)

π = Pi ( = 3.14)

Here is a link about rotational energy and the equation

KE = ½ Iω²

You equation will only work on a flywheel and doesn't give you the correct answer if the shape is change to say a sphere. The equation I have given will work for any shape as the moment of inertia I allows for the variations due to change in shape and axis of rotation.

It is an old document for calculating the _^WR2, and it's not very clear. However, this is an easier method for arriving at Flywheel dimensions for getting the desired KE. good luck.