Step 11: Generator and Electricals
The basic idea is to have the back tyre turn a roller which is connected to a generator. We are trying to have a relatively high rotational speed (to give us a reasonable high voltage (around 12 to 24V DC), hence we have a large wheel turning a small roller.
Building the roller: This is probably the hardest part to do without specialist equipment. It is best to have access to a metal lathe and someone who knows how to use it. Ask around friends and family. Get in touch if you need a roller made and maybe I can get some made up. Some people have had luck using a skateboard wheel.
Lathe a piece of aluminium into a 25mm diameter x 70mm length roller.
Drill a hole into the end of the roller (8.2mm diameter and 20mm deep).
Drill and tap a 5mm hole to hold the roller onto the generator.
Also check out the Magnificent Revolution plans as they have technical drawings for a roller design.
Cut the piece of plywood to the correct size to be able to fit into the gap in the frame. In the case it was around 150mm x 150mm. Drill holes for the hinge and for the generator. The generator has tapped holes for 6mm bolts. 6mm bolts were also used for the hinge.
The roller must be pushed onto the back bike wheel with enough grip to ensure the generator turns. To do this some form of elastic is used to hold the generator onto the wheel. Tent hoop elastic was used in this case, but bungee cords could also be used and might be more durable.
The elastic must clip onto something. In this design additional bolts are added onto which the elastic is clipped. This required two bolts on the stand and two bolts on the piece of wood. Do this on both sides of the generator.