piecepatrol99
Member
Has any one ever tried building a motorized bicycle with a jackshaft for shifting gears and still be able to bump start like a direct drive install?
I started out with a 26" wheel and a 7 speed hub. A frame mounted 49cc china girl backed up by a JS kit to connect my geared driveline.
The fork broke and it was stripped down to stock and exchanged for another bike.
Sadly the cruiser was no longer available in store and I bought the only bike available that the motor would filt in W/O having to buy more parts. A 700c flip flop fix.
Unfortuantely my 7 speed hub is too wide for the new bike. It works with the origonal wheel, but with out a first gear its a bit more work to get started. I've built up the chainring to atleast have a high/low gearing. But the seperation of the ratios is limited by the space in have on the front freewheel and clearance to the chainstay. 30 and 40T CR's make my high/low for now. Any smaller and I have no top end. Any bigger and I can't get the motor started. And I can't increase the gap in CR tooth number, that's limited by front deraileur travel.
In my search for inexpensive parts to better my build, I came across a freewheel cog that is mountable to a 5/8" keyed JS. The same as my JS currently in use.
I also have the 50T direct drive sprocket that came with the motor kit...
I'm thinking:
Motor output to 17T Sprocket on JS input.
9T JS output runs to 48T CR input.
30 or 40T CR output drives the 18T freewheel (currently on the back wheel. I have a 3 speed freehub waiting for a trip to the bike shop to have it installed).
Direct drive sprocket on the left side of the wheel will then turn the (smallest T number freewheel I can find) on the left side of the JS, next to the 17T connected directly to the motor.
I believe this design will work.
But contingent on the output of the motor 'spinning' faster than the 'returning RPM' from the left side of the back wheel.
Any thought, opinions, suggestions, ideas and information is greatly appreciated.
P.S.
I do know this: you can use 1/8 chain on dual chainrings and cassettes...but
You can't shift with 1/8 chain.
Even just on the from derailuer, it shifts just like 3/32, but after a limited number of shifts, the links sieze and start skipping on the rear cog.
This skipping has already taken out my front freewheel.
I was shifting with 1/8 chain because the 3/32 doesn't fit the 1/8 rear cog. It skipped no matter how I fiddled with it.
My to do list is short. Front and rear deraileurs are installed. Front is connected and functional. Rear is waiting for shift lever I ordered and a trip to the bike shop to have the cog swapped for the freehub. Then change the chain to 3/32....
And I'll be back on the road again, hopefully with the third freewheel for bump starting the motor ;-)
Hope you get rolling soon.
