alt.energy.homepower

On Sep 14, 12:49 pm, Jordan wrote:
> I've volunteered to help an artist, who wants to place a number of small
> vertical rotor windmills in a seaside park, on top of picnic sheds. (He
> has permission!)
>
> The rotors will be about 6 ft diameter, 3 ft high, and free-spinning -
> won't drive anything.
> The challenge is how to control the things so they don't spin too fast,
> but still be able to start in a light breeze.
>
> Of course, cost matters.
>
> Ideas so far:
> 1. Centrifugal-operated "air brake".
> 2. Permanent-magnet motor, with speed-sensing switch to short out for
> back-emf braking.
> 3. Sails attached with Velcro, to rip out in big wind.
>
> All comments and suggestions welcome.
>
> Jordan

Okay. Take a motorcycle drum brake. Now normally the drum would spin
and the shoes on the backing plate would be stationary.

Proposal; Spin the backing plate with the shoes and have the drum
fixed. You will need to replace the shoe springs with lighter springs.

The faster the backing plate spins the more the braking effect. May
require weight on shoes to increase effect and twin leading shoe brake
would be better.


OR

A chain type governer.

OR

As seems the case you are talking savonius, they are generally self
regulating and by tuning the angle of the blades can be speed limited.