If a large Lawn mower wheel is used with a bike generator then it will be capable of charging small Nicad batteries. To get DC the bike generator outputs 6 Volt AC into a bridge rectifier (can be purchased at Radio Shack). For the Propeller use 3-4 blades 4 ft long molding from a lumber yard mounted on a circular piece of plywood. This is then mounted onto the lawn mower wheel. To allow faster rotation in light winds, mount each blade with a relatively smaller angle made with respect to the mounting plywood. Use a mower axle or shoulder bolt of proper size. Warning: Props are Dangerous! People have lost arms, legs, heads, etc. Keep them high above the ground or put a fence around them. Curious kids and pets could die. You can't see the prop when it's running. The large tire and the small wheel on the generator produces a gear-up ratio making the generator turn faster than the propeller. It can be built for $50 or less.
Offered by Darrell.
Sketch by Mike.