Could This Be The Best Bicycle Generator?
Have you ever considered using pedal-power to top off your camper battery…?
Or even bypass the battery and run your camper appliances directly off of pure leg power?
If so, I’m going to recommend that you go ahead and SKIP the expensive bicycle generator options and go directly to David Butcher’s site, where you can learn about the next generation of pedal-powered energy hacks and even purchase plans to make your own super-optimized fitness-fueled electrical generator.
First, check out his “Pedal Powered Prime Mover” running a TV!
David has been experimenting with pedal power for nearly 40 years. So this unique design is no simple hack, but an evolutionary step beyond typical attempts to convert bicycles into practical power that can not only charge batteries, but run appliances at a really high efficiency — precisely because he engineered out the inefficiencies!
There are a few reasons why this design vastly outperforms your typical “bicycle generator”.
- It’s built around a “flywheel” design. The big solid wheel is made of cheap but heavy particle board, and it has a specific engineering purpose. To a mechanical engineer, a flywheel is analogous to a battery — it stores mechanical energy as it spins. Once you get it up to speed, it keeps on spinning on its own, turning the generator by itself, meaning you only need to pedal hard enough to keep its momentum from slowing. And by saving you energy *in your legs*, you’re able to keep the generator going at a higher horsepower for much longer!
- Smoother Power. A problem with bike generators is that your naturally irregular pedaling makes it difficult to run many appliances. In this design, not only does the flywheel smooth the generator *input*, but the incorporation of HUGE capacitor (a 58 Farad car audio capacitor) smoothes out the power so you can directly run household devices like televisions and computers (provided you are fit enough to pedal as hard as you need to.)
- There are no chains, belts, or gears adding extra friction. All of those things add a huge drag on your energy input (your effort) and energy output. You can easily feel this drag just by comparing how quickly your bicycle’s back wheel slows down relative to the front. (A few seconds vs. a half-minute.) It’s not the mass but the friction. For contrast, imagine replacing your front wheel with a heavy flywheel, spinning it up to speed, and observing how long it keeps spinning. The flywheel on David’s machine keeps spinning all that mass for more than a minute, and the motor shaft is spun directly by the rim of the flywheel, eliminating all those intermediary sources of drag.
- It takes up very little space! A typical bicycle conversion requires the length of the bicycle plus the generator stand, on the order of seven feet. But this compact design fits into a 2 foot by 3 foot rectangle.
But that’s not all!
One thing I love about his site — besides the treasure trove of science, experimental data, advice, and interesting ideas — is that he’s not just some guy peddling a bike generator (sic!), but a “true engineer’s engineer”. I say that because he actually understands through both theory and extensive testing exactly how inefficient this method is for charging batteries… and how incredibly efficient it is for running devices directly * without electricity *!
It’s a common misconception in our modern world that it’s best to convert power to electricity, because electricity is a more efficient medium of energy. IT’S NOT!
Converting energy between different forms is always extremely wasteful. For example, a gasoline motor converts chemical energy to mechanical locomotive energy at around 15-25%. For generating electricity -- ie. converting from one form of power to electrical power -- with the exception of hydro-electric systems, which can be 80-90% efficient, most power plants operate in the 20-45% efficiency range. Then in order to use the electricity, we waste a ton converting it into some other form, ex. light which is below 10% efficient or mechanical motion, which actually can be extremely efficient, in the 80-90% range, but when you consider that the electricity was created at 20-40%, we've now dropped that number even further. So making and using electricity is generally a fairly wasteful process -- We do it in order to enjoy the First World convenience of "cheap" electricity.
But it's EXTREMELY efficient if we skip the conversion!
Believe it or not... Ancient "low-tech" pure mechanical energy transfer methods (think of the Roman Empire) can be absurdly efficient. Imagine if you will a mechanical wind turbine at the top of a mountain. At the bottom of the mountain a mile away, there is a mechanical milling wheel. The two are connected by a long loop of cable in such a way that when the vanes of the wind turbine turn, the milling wheel turns with it -- essentially it's a windmill with the components separated by a mile. It turns out that power at the top of the mountain can be transferred down that cable to the milling wheel at near 100% efficiency! If you try that trick with electricity you'll come nowhere close. But it we can achieve such high efficiency not through some sort of low-tech magic, but simply because we haven't diluted the mechanical energy from the wind turbine by trying to convert it to some other form before converting it back to mechanical energy.
Which is all to suggest that if you want a real lesson in some pretty awesome DIY hackery, then you'll want to check out David's BEST experiments in pedal power, in which he uses his pedals to directly drive other devices *mechanically*. For example...
- Pedal powered washing machine and dryer
- Pedal powered blender
- Pedal powered whole house fan
- Pedal powered water pump and irrigation
- Pedal powered air compressor
- Pedal powered hand tools (grinder, disk sander, buffer, drill, reciprocating saw, lathe)
- Pedal powered offset printing press and sewing machine.
In addition of course to many varieties of pedal-powered electrical backup generators.
Hey, how can I use one of these for my camper?
I love the idea of having a pedal-powered system for my camper! The only thing I haven't figured out yet is how to fit it. It would be important to be collapsible, and I think his model has that option to design it that way. At the moment, this is one of those "when I get around to it" projects, especially since my camper's homemade solar panel gives me plenty of energy already. But I already anticipate that this would be one of my funnest favorite camper projects. I can hardly wait to start!