Having problems on building A bike generator

first, I have problem on choosing suitable generator. my choices are washing machine motor , alternator or water pump (1hp) what should i use ?!
second, how can i calculated the power i will take from the generator theoretically.
third, i had read that if i put a high gear ratio the motor will be destroyed because it can't hold it so how can i fit it with maximum allowable ?


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You did not mention what output you need, nor how strong your legs are.
With no info on the the generator, speed and so on it is impossible to tall how much if any power comes out.
No clue where you got the info on the destroyed motor but maybe whoever told you can explain why he or she thinks this way.
Even a good street racer is lucky to make and hold any speed over 40 km/h for a long time, do the calulations for there to see how little RPM you actually produce this way ;)