Electric Bike with energy generator.
This project was developed by students from 12th of a vocational Course of Computer Maintenance at EPFelgueiras (Portugal), as part of PAP project under my orientation. The goal was to build an electric bike under European legal rools but with a good performance and autonomy that could be used daily in a frequent up and downhill area, not realy appellative for bikes uses. Half year after, dinabike as over 2600 Km (1600 Miles) with no problems at all, except for regular maintenance: brakes, tires and a few tunings.
Step 1: Stator Windings
After a logic option for a electric bike convertion kit with 250W brushless motor, rear gear and 36V 10Ah Ion-Lithium power, left to profit downhill to produce energy to improve the autonomy of the bike. After some wrong options and consequent changes we've come to this solution. We decided to Build a new axis for the front wheel, wich was able to support, inner rays, magnets and the stator.
We began by the stator building a gadget to do the copper winding.
For a correct placement of the coils we designed and cut with a computerized milling cutter a polyester mold as shown in the picture.
Step 2: Rotor Build
The magnet were glued with epoxy on aluminum discs, side by side of stator. Once again for a correct placement we've built a polyester mold, using the some technique us we used with the stator. For a perfect fixation of the magnets, after removing the mold we gave more epoxy in the outline of the magnets as shown in the picture. As you can see, in the center hole, there's a pair of spheres ready to attach the axys. But it would be better to use bearings. See next step.
2 x 12 neodymium block Magnets Q-30-10-05-N42
18 cm diameter aluminum disc for magnets support
Epoxy for instant glue the magnets in aluminum discs
18 cm diameter polyester mold disc for a correct magnet position (made in CNC cutter)
Step 3: Axys Build and Mount
The front wheel axys was designed in AutoCad and build in a numerique mechanical lathe. This is the innovative part of the project
For a correct system to function we have implemented a double pair of spheres side by side underneath the rotors. As i said before, today i will use bearings because the mounting with spheres is not so easy. You have always to be aware not to lose any sphere in a moment where you have to grip the rotors by attempts, leaving the minimum space between rotors and stator. This is fixed in the middle of the axys. Afterwards, you assemble one side, giving the needed grip. Next you have to tight by attempts because the magnet doesn't leave space to use a tool to attach the nuts even if it was on plastic, there's no space. Interior nuts have to be tight before mounting the rotor.
Unfortunately we don't have any pictures of that assembly.
Step 4: The Tilt Controller
It was important that this dynamo could give us energy without growing friction. That's why we've included a tilt controller in our project. This dynamo is intended to work only at downhill conditions. The timer included grants that any irregularities on the roads don't revert the system state. Although it's advisable to add a on/off switch that habilitates to disable the dynamo/generator in very bad condition roads. The last two pictures in this step, show the electronic system used to double the voltage of the energy generated at the dynamo/generator using star type connection.
Step 5: Summary
In summary, I must confess that after increasing the voltage to 40 volts, there is very little amperage left. Still, it was enough to be able to increase the autonomy of the bike from 15 to 20%. I think it would be a good idea to try to put a generator on the type of brushless motor but with progressive income.
Many things were left unsaid, but I hope to answer all the questions raised by those who are interested on the subject.
For finish I leave some more pictures...