32mm Worm Gear Motor Hollow Shaft With Encoder − 85mm Type Model NFP-JGY-371-EN

This makes a great low RPM dc motor for windmill , waterwheel science fair projects, puts out 24 Volts DC at about 30 RPM, the load (resistance) across the wires will determine the amount of detent when you try to spin the turbine. It is a surprisingly strong and simple worm geared motor.