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jonboy2five

Member
Joined
Jun 8, 2008
Messages
40
ok guys how does this sound. 24" bmx cruiser+41cc mitsu 2-stroke+homemade rack mount + 6 tooth pinion on cent. clutch with 3rd bearing support to 98 tooth sprocket on hub = 16.333 to 1 and 30.59 mph at 7k rpm, with 22mph cruise....unforseen problems ?(with solutions) are very wlecome...
 
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SirJakesus

Guest
A 98 tooth sprocket is mighty large. Check out statons mini gearbox or some pocketbike gearboxes to get a little more reduction before final drive.
If you're going for homemade a friction drive setup is the easiest way to go.
 

jonboy2five

Member
Joined
Jun 8, 2008
Messages
40
i know..

i know its big but why is it a problem? clearance, maybe? i just thought it would be really simple without a gearbox...
 

SimpleSimon

Active Member
Joined
Apr 18, 2008
Messages
1,180
With standard bike chain that would be a 15.6 inch diameter gear. If 1/8th inch thick, it represents a lot of weight, then add in a lot of inches of chain. Hope you got good brakes.
 

jonboy2five

Member
Joined
Jun 8, 2008
Messages
40
98 tooth

the 98 tooth sprocket is for a goped scooter. it is big but not 16" diameter !...and it will match the pinion sprocket. wish me luck!
 
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SirJakesus

Guest
I may be mistaken but I think its the diameter of the drive gears that count when doing gear reductions not the actual amount of teeth on it. You're basing your calculations on the normal BMX spaced chain others are using rather than small pitched pocket bike chain. Just look at the GEBE system as an example. The clutch bell directly drives a small gear for the belt which then attaches to a larger drive ring on the wheel. You're going to be way over geared without a gearbox. If you're using pocketbike parts why not use a small 3:1 pocketbike bearbox to gear the rpm down to a more manageable range.
 
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