How would I build an electric generator with variable torque? It's my understanding that P=T*rpm, but that T is const.

I am interested in retrofitting a spiinner bike to produce electricity. The spinner currently uses brake pads to adjust the resistance. There is plenty of energy being 'lost' in the form of heat due to the brakes. I would like to be able to adjust the resistance of the bike without losing energy in the form of heat. I understand that gears are a possibility, but I would prefer to be able to adjust the resistance in a continuous manner. Any ideas? I've considered a CVT (continuous variable transmission) design, but this would be quite difficult. I've aslo wondered if the relative motion of a disk with permanent magnets to a disk of stationary coils would vary the resistance. I'm not sure what the range of variation would be however. Any suggestions or insights you might be able to offer would be much appreciated. Thank you.

daveames5 years ago
hi folks,

i have found that it is possible to vary the mechanical resistance/power output levels with a standard PWM controller. you can see the details here.

kindly leave a comment at the end of the project if you find anything of use.

cheers and good luck with your build! dave
jtobako5 years ago
At the local Science Museum, there is a display made up of a bicycle generator and 3-4 appliances like a light bulb, radio, and something else. The more appliances you turn on, the harder it is to peddle the bike. So, I would say, use up the power generated.