thecombover

For my pre-engineering class, we have to design a product. My friend and I were thinking of making some sort of generator that would charge a cell phone/iPod using the motion of the wheels/gears. We need to see if there is any interest or knowledge on anything like this, so any feedback, positive or negative, would be greatly appreciated! Thanks!

Juha

There are several commercial products available that do exactly what you describe. Usually you'd have a dynohub (dynamo built into the front wheel hub) as the generator, and the charging electronics as an add-on. See Buesch & Mueller homepage www.bumm.de for an example (E-Werk).

unterhausen

look at Peter White's website about dynamos. Specifically, this page
Lots of information about this subject, and my interpretation is you are more than a little late.
You should do more work before you start making surveys.

ks1g

It's an undergraduate pre-engineering (think introduction to) design class. No requirement to be ground-breaking, innovative, or even commercially viable. Learning to do market research, address trade-offs, and balance competing technical and non-technical issues are part of learning product design (which is way different from engineering analysis).

There are several bike generator products out there (best IMO use a dynamo hub on the front wheel) that combine a rechargable battery and various USB-like options for recharging portable electronics. Some include iPod-compatible mounts and a way to mount/protect an iPod or iPhone. Do your research and see what you can come up with. There are some interesting tradeoffs for size, weight, weather protection, vibration, safety (shorts, electronics, and no bits falling into the spokes!) and generating capacity. Consider if it's intended to be a range-extender (assumes wall-jack available someplace for full recharges), or you expect it to keep electronics going for several days (unsupported touring/bike-packing scenario), and if it is solely for add-on electronics or you want to power lights, too. Humans don't produce a lot of power (the capabilities of the pros are the 99th percentile, at least), so a few watts, before conversion and storage inefficiencies, is going to be the most you can expect to harvest.

Airburst

Since we're dealing with actual engineering here, I'm just going to point out that there's technically no such thing as a bicycle dynamo. Dynamos produce direct current, and all bike generators produce alternating current. "Dynamo" has become accepted terminology in the cycling world for any bike-mounted generator, but I'd assume an engineer would be required to call it an alternator. An actual dynamo would probably have quite a lot more drag due to the brushes, so your best bet is likely to be an alternator even if you don't buy something off the shelf.

Throwing out another technical point, the frequency of the AC produced by a bike generator varies a lot with the speed of the bike, so your conversion electronics will need to be able to deal with that.

Not sure what else to add...

krome

A permanent magnet alternator is also correctly called a magneto.

thecombover

Thank you, those all helped a lot! By the way, it is a high school class so ks1g is right in saying it does not need to be revolutionary or viable. All of the research I did before only yielded results concerning stationary generators, so these are great! Thanks again.

fietsbob

Modern dyno-hubs are alternators, put out AC, so a full-wave bridge rectifier
is then part of the system to DC the AC..

solar panel is DC .. , a battery, charged, in common, seems the thing to include.

It should be apparent that you are adding to a market where those things already exist..



A gimbaled maximum solar input seeking (powered) solar panel holder
would be a clever thing
to be towed as part of a bike trailer.. since in motion keeping the large enough panel
at a right angle to the sun as it transits over the day , on moving vehicle is another issue to tackle.

Oh and make it nearly weightless..

ksisler

If time permits, I would recommend your class study group refocus on brainstorming a conceptual or theoretical solution set for a problem not yet solved or for a novel application of an existing solution... For my interest, I would like to see someone examine a potential solution for powering bicycle lights that is based: 1) On the movement of an object in one of the frame tubes that is filled with a special liquid or gas (the ocean bearing wave generators provide at least basic theory to start with); 2) On the interaction of a reformulated tire with the typical pavement material; 3) On the interaction between a reformulated magic tire material with a device mounted fork crown; 4) #3 with the tire being inflated with some percentage of a to be determined gas or perhaps to be developed yet based on properties analysis; 5) To find some kind of liquid or gas to put into a frame tube or in the tires which could store up energy like a battery given either in use charging with a known dynohub or precharging from a wall wart charger; 6) Or some type of mini-fan system that spins up a small dyno from the air flow during riding (the design of the units used on airplanes provide a baseline to start researching. Hope this helps.