what would happen...

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Ilikeabikea

Ilikeabikea

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Jan 27, 2008
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Math never was my strong suit so all of this may be dead wrong. So take it with a grain of salt. A 26" tire travels 6.8' per revolution. So at 500 rpm's the back tire would travel roughly 3400 ft which would be roughly half a mile a minute or a little over 30 mph. If the engine has to turn say 5000 rpm's to have any power you will need the back tire to turn 1 revolution to every 10 revolutions of the engine. So would that mean if you have a 10 tooth primary you need a 100 tooth secondary? That would be a huge gear. Does any of that make sense or am showing how poor my math skills are????????????????:D
 
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Mobius

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but why would you use a 10 tooth primary? Im talking about using something with 20 to 30 teeth and probably hooking up to the largest hear on teh cassette

not to mention to keep it inconspicuous I need to keep it under 25 mph
 
Ilikeabikea

Ilikeabikea

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Your talking a 20 or 30 tooth on the engine? If you have 20 tooth on the engine you would have to have a 200 tooth on the rear wheel to get a 10 to 1 reduction....................
 
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Mobius

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Well obviously math and ratios were never my strong suit either rotfl

hmm I guess these are all signs pointing to friction...

any ideas on how to help it keep from slipping when its wet?
 
jasonh

jasonh

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are you any good at fabrication? here's my idea....

So, you're going to need 3 of the skinniest road bike rims you can find. Basically you would weld all 3 of them together, and then take a chain and wrap it around the middle one and weld it in place. Then instead of an actual friction drive, you'd have a sprocket on the motor shaft which would lock into the chain in the middle rim and drive the bike. And you'd have a tire on each of the outer rims. so it'd be tire-chain-tire.

And nobody believed me when I said I was nuts :)
 
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Mobius

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brilliant idea but it seems like it would be a fabrication nightmare. getting teh chain welded in straight would be rediculously difficult but I think if you could do it it would tield fantastic results (as long as you didnt end up too wide for the fork)
 
jasonh

jasonh

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hmmm...you could rig up a cover for the motor and drive wheel, and then have some kind of contraption that you could engage to lightly brush the tire before getting to the motor that would help to keep the water off. A slick tire would probably help in that department as well.
 
Ilikeabikea

Ilikeabikea

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My stuff may all be wrong. But I have seen some bikes that use a belt and they have a real larged diameter pulley on the rear wheel. But then you wouldn't be able to use your gears. Pablo needs to make jackshaft kit now to sell to the weedeater guys:D...............................
 
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Mobius

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Sigh I have to admit that this is a daunting task for someone who has never done this before. If I said I wasnt frustrated I would be lying but theres so many ideas its kinda like overload
 
jasonh

jasonh

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The riquimbili guys would have a belt going from the motor to the drive pulley, and a pedal that they would press to make the belt have contact with the pullies. Let off the pedal, no contact, no drive. In otherwords a very homebuilt clutch :)

As for the chain, welding it to the outside of the rim directly probably wouldn't be strong enough. You could weld a very narrow road bike rim to the rim and have the chain on that though. might work.
 
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