A rotor having 8 eight vanes on its periphery.
Each vane is of 20kilo gram weight. During run one vane broke and the rotor get unbalance.
So to balance it a vane opposite to broken one is cut. now i want to know wheathes it is technically balanced or not, if not then what will be the resultant forces left on rotor after reoving the two opposite vanes.

force due to imbalance (pounds)=1.77 * ounce*Inches * (rpm/1000)^2

It may be ok as far as balance goes but that would be a lucky break.

How well the fan functions with 25% of the vanes missing would also be of concern to me.

I assume that this is an emergency measure and that proper repairs are in the plans?

Vinay, I have done the same thing myself, but to a squirrel cage fan having many blades. In my situation, there were enough blades for the fan to keep moving air. But with your situation, on the surface is seems that while you may have balanced the rotor, you have reduced the efficiency by an assumed 25%.

I agree with Danny - it's probably a decent emergency procedure, but not a "fix".

What about your axial vibration in this case?