Tire driven generators&chargers,a lost cause?



Has any one ever SUCCESSFULLY !! implemented a 12 V battery charging system based on a roller equipped generator,with the roller contacting the tire apex?
I came across a radiator fan motor that looks tempting, for use as a dc. generator.It puts out around 4 V/1000 rpm or at 3500 rpm,14.5 V at 1 Amp plus, based on tests using my drill press.This implies a roller diameter in the range of 1.5 to 2.0 " (assuming 20/25 mph road speed)
Are these standard roller dimensions used in friction drive systems?.In a Staton based setup it might feasible mechanically to come up with a spring-loaded swivel mount located at the back of the gearbox.The electricals I can handle,that's the easier part.
Any caveats or sage advise ?,has any one ever tried something along this line ?,could this be considered do able,or a potential Goldbergian lost cause, if not a mechnical quagmire,who speaks from experience?
Sorry, no experience here. But if I had such a motor and a bit of hardware I'd be likely to give it a try. The only thing is that I don't think I'd count on averaging 20-25 mph at night.
Unless it was able to power some awfully strong lights. But if a smaller roller is the price you have to pay, that shouldn't be too much of a sacrifice.

Reading the posts it seems that others haven't had a lot of luck with generators. But maybe you can make it work. Good luck!
I think it is a good idea, but the key is to hook it up to a regulator and use it to charge batteries- then run the lights off the batteries. With LED's you don't need big, heavy batteries. This way, you get light stopped and do not lose voltage to the lights when slowed up.
Houhmade is right - even the so-called 'bottle generators' can put out enough power, if the power is properly managed, to provide acceptable lighting, especially with the new LED systems. However, I would NOT use a bottle generator. Unless you get an expensive one, they are very cheaply made, and won't stand up to continuous use. In addition, they are exposed to the elements, and to the road crud that gets on the tires. Plus, when it gets wet, they tend to slip. THAT issue remains the same, whether you have a good tire driven generator, or a poor one.

When you say "friction drive," are you discussing a friction drive bike motor, or a friction-driven generator?

If you want to use it with a Staton chain drive system, you could put a sprocket on the generator, and make the generator a part of the chain tightening system. Or, Staton now offers (at extra cost) a dual output gearbox, where the added, intermediate shaft RPM is approximately 1/5 the engine RPM.

Or, with a Staton friction-drive; You should be able to drill/tap a 1/4 inch hole into the center of the end of the friction roller opposite the engine. Add a standoff spacer, and a small chain or pulley, and bolt it down with a 1/4 inch bolt. (The thread direction with a normal right-hand thread will tend to tighten the bolt, not loosen it) Then, mount the generator on the friction drive channel. Be sure to add a full chain/belt cover, not only to keep fingers out, but to protect the drive from the elements.

The other approach is to get a hub-mount dynamo. (Either Shimano or Sturmey-Archer.) I've bought a Sturmey-Archer X-FDD dynamo hub with brake, so that both the generator and the front brake are away from the road crud and elements. That dynamo can keep batteries charged, which in turn provide power for your lights. ref http://www.motoredbikes.com/showthread.php?t=9121

A hub dynamo puts out 3W, 6V at 8-10 MPH. The output tops out at about 6 watts, at about 20 MPH.
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Thanks for the info,the extra take-off on the Staton gearbox looks like it has a chance of working, but it still takes 5/10 times speed-up to run a generator,but for me that approach is no longer an option.I also have my misgivings that over time, the bearings of these motors wont stand up to the side thrust imposed by the friction loading.Automotive parts manufacturers are not noted for goldplating their products.Ordinary bottle generators are too junky,you could probably dig up something durable and expensive in Euroland,if you tried hard enough.
That pretty much leaves the SA hub,the drum brake is certainly worth having,rugged and reliable, but with relatively poor heat dissipation capacity,a good idea is to complement it with a rear rim brake.All in all a good buy at $60/70.
Quite a lot of interesting and useful info about hub generators and in particular bicycle light circuits can be found at http:// pilom.com.I recommend it for perusal by members who have had some exposure to power supply electronics.Most of it is from material in German that has been translated.They have some really fanatical generator investigators over there.