Jackshaft Better than Jackshafting?

Nanonevol

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Oct 1, 2015
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Imagining a design for transmission from a left side output motor (China Girls, etc) to a freewheeling sprocket on the left side of the bottom bracket. This would require a bottom bracket with basically two axles - sprockets on both sides connected and freewheeling on a central pedal crank axle. Someone would have to create this of course as it is not available anywhere. Simpler than jack-shafting to the right side though with less friction and fewer parts to keep tuned and adjusted. I wonder if it could be made with any off the shelf parts or would require some real innovation and a machine shop.
Would then have all the advantages of a jack-shaft. I'd like to see a heavier - than - bicycle sprockets and chain on the right side as well to a sturdy rear hub with internal gears. Anyone?
 


troyg

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Sep 3, 2014
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I believe that's called a freewheel kit, that you can get premade at sick-bike-parts all day long.
 

jaguar

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for the same amount of trouble you can have a bike that goes 48mph maximum and yet still take off good from a start.
That is possible by utilizing my recommendations for these engines. I know because my 55cc Grubee did that.
Shift kits add complexity and rob 8 % of engine power. The people that race these engines don't use shift kits.
 

KCvale

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Or you could just kiss 2-stroke hassles good-bye and use a 4-stoke/transfer case combo that drops the output right above the freewheel pedal chain rings to use the pedal side gears.



That's a 53cc 4-stroke with a 7-speed that does over 45mph too, and it's a pull start, automatic clutch, regular gas burning breeze to ride.

In short there are systems available, I know, I develop them ;-}
 

Nanonevol

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Well that's cool - but the complexity is still there it's just built into the motor (and is surely reflected in the price). And sure, I could improve my 2 stroke and get more power but that's not the point. I want to shift gears. Nobody wants to take on putting a sprocket on the left?
 

Timbone

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Two gears on the 66cc two stroke would be very sweet. Dollar for dollar, jackshaft is the way to go. I can envision a simple two speed gear box with two axles and a simple dog clutch deciding which of the two ratios (high or low). The devil is in the details. You'd have to have a really good, foolproof mechanism for the clutch (and engagement would have to be perfect every time) because diddlng with the tranny on the side of the road would be an enormous pain.
 

Fabian

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Or you could just kiss 2-stroke hassles good-bye and use a 4-stoke/transfer case combo that drops the output right above the freewheel pedal chain rings to use the pedal side gears.



That's a 53cc 4-stroke with a 7-speed that does over 45mph too, and it's a pull start, automatic clutch, regular gas burning breeze to ride.

In short there are systems available, I know, I develop them ;-}
The police would throw you in jail for that setup in Australia, and then give you water boarding torture, and throw you in a cell with a person of the same gender, who takes fancy to a person of the same gender.
 

KCvale

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Well that's cool - but the complexity is still there it's just built into the motor.
I want to shift gears. Nobody wants to take on putting a sprocket on the left?
Actually the 4-stroke engine has no internal gearing or clutch at all, that's why they require an output reduction and cent. clutch.
A simple belt reduction, the gearing shifting gearing is done at the back wheel for there no simpler way.

But you have a 2-stroke with an internal gear reduction and manual clutch.
You can just mount two different size sprockets on the back wheel and make a derailleur to change between the two.
 

Pablo

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for the same amount of trouble you can have a bike that goes 48mph maximum and yet still take off good from a start.
That is possible by utilizing my recommendations for these engines. I know because my 55cc Grubee did that.
Shift kits add complexity and rob 8 % of engine power. The people that race these engines don't use shift kits.
Why not do both? Improve engine power and jackshaft? Sure of course some power is consumed in the drive chain, but racing isn't the street. The racing so far is just a flat track affair, where the person with the biggest and smartest gonads going into corners wins. Some hills, much tighter corners, and people with the skills and engines to use gears, the outcome will be different.
 

butre

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for general rideability and longevity nothing beats a shift kit, but bicycle gears are clunky and inefficient. a CVT would be more ideal on the racetrack.
 
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