Remeber This
* Old Topic Bump *
The Jackshaft turns 2 years old.
Hats off to the guys at Sick Bike Parts
http://sickbikeparts.com
I haven't tried their jackshaft yet but about to.
It was great to read this whole topic and see how it was developed.
I'm a sucker for cool home grown great ideas ;-}
Considering my own first improvement was about chain tensioners, this one stone kills a whole a flock of birds. Kudos again.
There are trade-offs to using just one drive chain to the wheel with two power sources (pedal or motor). and not have both sources in constant synchronous motion (the pedals moving when the motor takes over), for example.
My next MB project involves a 3-speed hub coaster brake bike.
It's a quality bike with a Shimano 21T 3 speed Internal hub so I think that will hold up fine even with a Grubee 66cc, but I figured since I was researching how it works now anyway I might as well post some simple info.
Advantages
You can use your existing bike gears with the motor!
No second chain drive at all.
No chain tensioner ever!
You don't even need the kit sprocket, chain, chain guard, or even the seat downtube motor mount.
Disadvantages
You can't just pedal up to speed and pop the clutch to start it because there is no direct connection between the wheel and motor.
That means you have to get going pedaling, and continue pedaling because it is just your pedaling force that will turn over the motor with no help from the back wheel.
It also means that any hub brake is rendered useless. Pedaling backwards free wheels as well. That is how the pedals don't have to move when the rear wheel moves when the motor takes over.
No biggie for a derailer bike, they work the same way, but a bummer if you wanted to put it on a 3-speed hub coaster brake and wanted to use that brake.
As mentioned I have yet to install one yet, I am just doing my homework, but I highly recommend you read the Shift Kit Instruction Manual first to decide if you have the skills and tools to install it.
http://www.sickbikeparts.com/catalog/productdownloads.php
Conclusion
I can't wait to try it out for myself ;-}
