How much weight is needed to create a certain amount of power?

[nirvana]

 Hi members,  how much unbalanced weight would be needed on one side of a wheel to be able to run a 5kw generator.
  Lets say the diameter  of the wheel is 2 meters, and spins at 100 RPM.
  So this would need to be geared  up dramatically to run a generator, ( lets say a 20 to 1 gear  ratio)?
  I dont have a clue how to work this out, but i am assuming you would probably need at least a few tonns of difference on 1 side of the 2 metre wheel.
  Also what happens if the revs of the wheel was 500 RPM, (with a 4 to 1 gear ratio to run the generator). ?
  Would it be uniform and  need 5 times less weight ?

Thanks.


   
   

[mapsrg]

ok  lets see.....You want 5Kw from a 2m Diameter unbalanced wheel so................................................
Assuming clockwise rotation of the unbalanced wheel the weight needed to balance and stop rotation of the wheel positioned at 9oclock would be the mass used to work out the Potential Energy of the system.Potential Energy is mass * gravity * height and is measured in joules.5Kw is 5000 joules per second.So 5000=mass*9.8*1    The height of 1m being the fall from 3oclock to bottom of rotation.Therefore the mass is 5000/9.8=510.2kg.....................................................................................

[usama salah]

 ok , if the wheel do its complete rotation at 15 seconds , and i need to run a 25kw generator at 100 RPM , SO how much weight i must use at one side ? and what is the gear ratio i have to use to geared it up ? assume this geared up will need extra work power or weight.

if you please solve it in details
thank you

[mapsrg]

......@510.2 kg............rotation ? rpm.....Thats a lot of weight ?As a guess rpm would be up to 240 maximum.

[hansvonlieven]

G'day all,

Isn't this all a bit academic? Seeing that no-one has gotten a wheel to RUN (at least convincingly so with replications) wouldn't it be wiser to achieve that before trying to work out how many weights one needs for x amount of horsepower?

Hans von Lieven