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Jun20-08, 07:51 AM
Redbelly98's Avatar
P: 12,074
Quote Quote by MechaMZ View Post
btw, now my rpm is around 160 at 4m/s, I'd have to increase it to 260. So I think gearbox is needed. of course I will increase the blade size as well :)

but what are the factors actually will affect the rpm?
Connecting the turbine to a generator will slow down the rpm.

Using a gearbox to increase the rpm is like shifting to a higher gear on a bicycle. And, connecting the turbine to a generator is like riding your bicycle up a hill. If you go to too high a gear, you will not be able to pedal up the hill, and actual rpm becomes zero. Likewise, using a gearbox to increase rpm could actually make the thing run slower (or even stop) when you attach the generator.

There will be an optimum gear for a given wind speed.

edit added:
Given the low winds you are working with (2-3 m/s or 4-7 mph), you would require a relatively low gearing, compared to having the same turbine in say a 15 m/s wind.