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-   -   generator idea (https://www.bikeforums.net/electronics-lighting-gadgets/443611-generator-idea.html)

trekker pete 07-20-08 03:19 PM

generator idea
 
You have your hub type generator/dynamos (expensive), your tire sidewall thingies (not very efficient), how's about this idea. It could be a generator or made big enough maybe a motor to give you a bit of help making that hill.

I was thinking something mounted in the Vee of the frame with chain drive to that little ring they put up front that most folks don't use anyhoo.

The advantage is that it would be plenty sturdy enough. Very easily mounted and could be installed/removed in less than 5 minutes.

I suppose somebody is gonna burst my bubble and tell me it's already out there or why it wouldn't work too well. That's ok, I can take it. The only possible problem I see is the 2 chains rubbing one another when you are on your middle front cog. Spacers for the small ring should fix this, if there is clearance enough.

BTW, what the hell is the difference between a dynamo and a generator?

StephenH 07-20-08 03:44 PM

One drawback- when you stop pedaling, the light goes out.

n4zou 07-20-08 04:11 PM

I hate to burst your bubble but perpetual motion machines don't work.
http://burtleburtle.net/bob/physics/whythere.html
The term dynamo as used when describing the little alternator used on bicycles to power small lights is actually incorrect. Every one has simply used the term "dynamo" for so many years it's stuck and will be very hard to remove from the language. Just in case you've ever wondered what the innards of a bicycle dynamo looks like, here you go.
http://i143.photobucket.com/albums/r...zou/dynamo.jpg
Starting on the left you can see the little wheel that presses on the tire connected to a shaft. The shaft is attached to the magnet which spins with the wheel. The magnet spins inside 4 metal poles producing lines of magnetic flux to flow into the coil. The flux causes electrons in the coil to flow producing current and voltage. This was a vintage dynamo that quit working because the glue used between the shaft and magnet had deteriorated so the shaft could not drive the magnet.
Modern dynamos are much more efficient using rare earth magnets and 8 poles instead of the 4 shown in the photo above. Drag is much reduced. In the old days a vintage dynamo could take 20 watts of energy to spin. The typical modern bottle or BB type dynamo now only requires around 8 watts of energy from the cyclist to produce light. Considering the average cyclist can produce 400 watts that cyclist can actually forget about the slight added drag when powering the lights.

trekker pete 07-20-08 04:41 PM


Originally Posted by n4zou (Post 7098467)
I hate to burst your bubble but perpetual motion machines don't work.

why, you're just another shill being paid off by "big oil"!!! :D

I mean, I saw it with my own two eyes on the interweb. All you need is some magnets, some copper wire and a few bearings and you'll be blowing down the freeway at 80 mph.

Sorry if my original post implied one of these magical devices that "big oil" is keeping from us. You would obviously need a battery or flux capacitor or somethin' if you wanted it to be a motor.

And yes, a genie don't put out much juice when it ain't spinning. I am aware of that.

I was thinking either a small battery or capacitor. I would think that a small battery capable of giving a good output, but, for a short time would work well in this application.

trekker pete 07-20-08 04:51 PM

Thanks for the link on perpetual motion. It made my head hurt a little.

My favorite youtube scientist video is where a guy spins up a heavy ass motor, maybe over 100 lbs. He gets it cranking at some pretty good revs. He then pulls the plug from the wall and .......viola....... the light bulb is still lit.

Halleluleah!!!! (sure I messed that spelling up)

We is saved from global warming. The Arabs can stuff their oil. We have free energy!!!!!! Al Gore can relax now!!!!!

Don't worry about the fact that that fast spinning heavy motor is chock full of kinetic energy that came from good old electricity. Probably from a soot spewing coal plant.


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