Is this even possible? Right side shaft/"Hijacking" front gears.

M

motorizemyride

New Member
Hi all,

I want to do a chinagirl build on a mountain bike with front and back disc brakes. The idea hit me to simply get a motor with a right side drive shaft, chain it to one of the front gears, and voila. Sure, you wouldn't be able to shift the front gears, but you'd still be able to shift the back ones.

What are the community's thoughts on feasibility/difficulty? Do they make right side drive chinagirl kits? Obviously I wouldn't be shifting while the engine is at full RPMs (likely not at all while the engine is running) as that's basically asking for trouble, but are the components going to be up to the task?

Also, I'm curious about 29'ers. If the above idea proves to be utterly ridiculous, what should I be considering for tooth count on a sprocket? What are the pluses and minuses of using the larger tire size?

Finally, what are the benefits of rear shocks vs. just having shocks/springs/whatever incorporated into the seat/seatpost? It seems to add an unneeded level of chaining/sprocket complexity in my mind, and as a bonus robs you of a teensy bit of power, but there may be tangoble benefits I'm unaware of.
 
motorizemyride said:
Hi all,

I want to do a chinagirl build on a mountain bike with front and back disc brakes. The idea hit me to simply get a motor with a right side drive shaft, chain it to one of the front gears, and voila. Sure, you wouldn't be able to shift the front gears, but you'd still be able to shift the back ones.
Click to expand...
The vast majority of motors spin CCW.

If you face a CCW motor to the right side it will turn the rear wheel backwards.

If you face a chinagirl motor to the right side not only will it be spinning backwards
but the chain opening will be facing in the wrong direction unless you mount it upside down.

Have you looked at Sick Bike Parts jack shaft kit?

The scooterguy made front sprocket driven bikes but he used 76 mm
centrifugal clutch motors with a 5 to 1 reversing gearbox and the
motors were mounted where your left knee is sticking out from the frame.

Doesn't sound like you thought your idea through. :)

There are some Clockwise turning motors but they aren't cheap and a
KT 100 would tear your gears to shreds at over 15 HP

I don't know of any cheap, small clockwise motors.

Joker Machine Inc just made a right side drive but it jackshafts over to the
left through a custom built reverse gearbox and you couldn't afford one. :D


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motorizemyride said:
Hi all,

I want to do a chinagirl build on a mountain bike with front and back disc brakes. The idea hit me to simply get a motor with a right side drive shaft, chain it to one of the front gears, and voila. Sure, you wouldn't be able to shift the front gears, but you'd still be able to shift the back ones.

What are the community's thoughts on feasibility/difficulty? Do they make right side drive chinagirl kits? Obviously I wouldn't be shifting while the engine is at full RPMs (likely not at all while the engine is running) as that's basically asking for trouble, but are the components going to be up to the task?

Also, I'm curious about 29'ers. If the above idea proves to be utterly ridiculous, what should I be considering for tooth count on a sprocket? What are the pluses and minuses of using the larger tire size?

Finally, what are the benefits of rear shocks vs. just having shocks/springs/whatever incorporated into the seat/seatpost? It seems to add an unneeded level of chaining/sprocket complexity in my mind, and as a bonus robs you of a teensy bit of power, but there may be tangoble benefits I'm unaware of.
Click to expand...

If the right side shaft is "Hijacking" anything, especially gears, it's probably a terrorist shaft and must be reported to the proper authorities. Don't hesitate, ya don't wanna get shafted by this one :D
 
Yes, I am aware of jackshafts... I'd just rather find a chinagirl which spins in the proper direction. My primary interest is reduced complexity. Unless the proper engine exists (as an in-frame option) I may just simply get a bike with front disc and rear linear brakes. Anything in regards to the rest of my post? If I'm not going to hijack the front sprocket I'm especially curious about how many teeth my rear sprocket should have in regards to a 29 inch tire.
 
motorizemyride said:
Yes, I am aware of jackshafts... I'd just rather find a chinagirl which spins in the proper direction. My primary interest is reduced complexity. Unless the proper engine exists (as an in-frame option) I may just simply get a bike with front disc and rear linear brakes. Anything in regards to the rest of my post? If I'm not going to hijack the front sprocket I'm especially curious about how many teeth my rear sprocket should have in regards to a 29 inch tire.
Click to expand...

No one can say how many teeth you need.
We don't know how much you weigh.
how steep hills you want to climb.

download, install and calculate ratios. :D
http://jimsitton.net/ratiocalc/
 
MotorBicycleRacing said:
No one can say how many teeth you need.
We don't know how much you weigh.
how steep hills you want to climb.

download, install and calculate ratios. :D
http://jimsitton.net/ratiocalc/
Click to expand...

Thanks for the calculator, that's awesome! For reference I'm about 165 lbs. I'm not too terribly sure what kinds of grades I'll be attempting, but 45 degrees is likely the max I'd be encountering. To an extent, I'd imagine that shifting gears will help me with hill climbing should torque be an issue.

I looked at jackshafts a little more closely - they're not nearly as obtrusive or cumbersome as I initially thought. This will probably be the solution I go with rather than searching out some exotic motor. A question with the calculator in regards to a jackshaft: do I have to do two sets of calculations from the engine to the jackshaft, and again from the jackshaft to the final sprocket (with a different calculation for each sprocket I could shift to, obviously)
 
motorizemyride said:
A question with the calculator in regards to a jackshaft:

do I have to do two sets of calculations from the engine to the jackshaft, and again from the jackshaft to the final sprocket (with a different calculation for each sprocket I could shift to, obviously)
Click to expand...
Click the help button on the calculator.

There are 4 ratios with a Sick Bike Parts shifter kit.
The calculator only does 3 but you can combine the
engine and first chain ratio in one box.

The 66 cc motor has a 20 tooth gear driving a 82 toother = 4.1:1 ratio
 
Begging you pardon kind Sir. I believe King's Sales and Service may be of assistance to you. They sell what is called a top hat adapter. This would allow one to install a "china girl" onto a bicycle that has a rear disc brake.
 
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Maxvision said:
China girls can run in either direction. I think if you reversed the magnet it should run either way.
Click to expand...

Won't the physical housing still be wrong?

kevyleven007 said:
I think kings can help you run a sprocket and disc brake on the same side and might save you's a looota headacke buddy.Your already givin me one
Click to expand...

The writing in your post gave me a headache back, so we're even. PROTIP: Those little red squiggly lines under what you've written mean a word is misspelled.
 
Have been watching your thread, and see you want to do somethings "just differently"! That's cool. Two strokes run backwards just fine. The only mod you need is to "retard" the ignition timing an equal amount from TDC as it is now "advanced". The engine will never know the difference. Good luck drn2
 
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