As a former competitive swimmer who could do 11 pool miles a day, David Butcher knew the human body could crank out a couple hundred watts of work for sustained periods. What if he could turn muscle power into electricity?
Having witnessed the 1969 Santa Barbara oil spill, Butcher is a dedicated environmentalist. He wanted to get off the grid, but he found solar and wind projects unfeasible. “That left me,” he says.
So he built the Pedal Powered Prime Mover (PPPM): a souped-up stationary bike generator that boosts efficiency with a large particleboard flywheel that smooths out the torque peaks of pedaling.
Its generator is a sealed ball-bearing motor from a Razor scooter, driven by a BMX crankset. Completing the setup are a 1,000-watt inverter, Watts Up power meter, and Maxwell Technologies 15-volt, 58-farad ultracapacitor module to store power quickly and dump it on demand.
Butcher, 55, has clocked his peak output at 265 watts (1/3 horsepower), but reckons a younger rider could double that. At his home in San Jose, Calif., he uses the PPPM to power laptops, TVs, a Roomba, even a front-loading washer (with the help of a battery boost to surmount the spin cycles).
In his video on Make: television, he cranks up enough juice to run a 500-watt blender and puree a liter of smoothie in under 60 seconds. He’s cut his energy bills, dropped 40 pounds, and gotten super fit.
“The longest I ever rode was at Maker Faire 2007, from 9 to 6,” Butcher recalls excitedly. “I also watched the entire Battlestar Galactica finale, powering it myself. That was a big one for me!”
Butcher sells detailed DIY plans for the PPPM and promotes it for everyday and emergency power, and for use in remote villages. But he says the most efficient use of pedal power isn’t electricity — it’s direct mechanical connection to turn a pump, fan, or the like. As evidence, he’s also built a pedal-powered pickup truck and a pedal-powered canoe.
Pedal Powered Generator: makezine.com/go/pedgen
Make: television Episode 110: makezine.tv/episodes