Ok I have been thinking about this project again. I believe that it is possible to build a 36 inch diameter alternator that will have a much higher out put than anything most people believe is possible.
How ever it may take a small gasoline engine to run it (and maybe we should just use a car's alternator). I saw the plans in the book "home brew wind power" they have one that will produce 3000 watts at 400 rpm., but it will not do anything at less than 150 rpm.
Right now we are using a two stage gear increase to turn a DC motor, only 35 watts can be maintained for a half hour. gear losses are great: Timing belts are around 90% efficient. Chain around 85%. So we intend to give up the gears, and pedal directly, unless it really is impossible to design a pedal power generator that can maintain a higher power, like one hundred watts (with a load of a charger) at some thing like 60 to 80 rpm.
David Butcher has built a 30 inch diameter fly wheel that turns a very small dc motor, and gets more energy than wasting about 30% of human energy into bicycle gears.
So What I need to know is, what speed does it take to generate a given amount of energy? and how wide of a permanent magnet can you get? ( the wider the more electrons?)
The thing that started me thinking about a 36 inch diameter, is momentum. And increased rim speed. But I also need to know how much foot lbs it will take to turn this concept alternator, what is the magnetic resistance??
Rim speed in inches/minute
Circumference* rev/min
42 inches *pi* 50= 6597 inches/minute.