dual freewheel front sprocket drive

[jdcburg]

Hello folks - I have developed and bench tested a prototype dual freewheel front sprocket system to allow an emotor to power the bicycle through the pedal crank so the shifting system (rear hub or derailleur) can be utilized. One freewheel allows the cranks to remain stationary when under motor power (nothing new there) and the second freewheel allows the motor driven sprocket (on the BB spindle) to remain stationary when under pedal power, reducing drag caused by the motor system to a minimum. I've posted a video on YouTube of the rough first prototype during a bench test. It's at YouTube - Dual Freewheel Front Sprocket System Prototype If others are interested I'll post details. - jd

[deacon]

Now that's the cat's pajamas. For anyone wanting a chain drive with gears it looks like just the thing.

[Cabinfever1977]

They already have something like that for electric bikes and gasbikes.

http://www.cyclone-usa.com/

http://www.nycewheels.com/giant-lite...sted-bike.html

[jdcburg]

Hi Cabinfever - The system I designed and built is different from the Cyclone systems as well as others that drive through the derailleur/rear hub (SickBikeParts, Elation and Eclipse) in that the freewheel that frees up the motor when under pedal power is on the bottom bracket spindle. All the others have the freewheel on the motor and the motor-driven sprocket (on the BB spindle) is bolted or riveted to the pedal-driven sprocket. In those systems the motor chain is driven by the pedals, causing some excess drag. Also the smallest motor freewheel sprocket is 14T, where my motor sprocket is 9T. The Giant has been discontinued and replaced by the Sanyo Eneloop, a $2300 front hub drive. The Cyclone single chainring system has the motor down in the lower chainline, subject to water, mud and debris. It's all about compromises. Mine can't be used for regen or pedal-start (rules out most 2-cycle CGs) because of the freewheel.

I put a 350W Unite MY1016Z3 (w/built-in gear reduction) and took it out for a short test drive during a break in the weather. There didn't seem to be any problems. I used a little pedal-assist and had good hill-climbing ability in the lower gears and reached an estimated 25 mph in 8th on the flats - jd

[Cabinfever1977]

Yes i see the diffrences now, Its always great to see new ideas.

[roofman6]

I'd love to see more details on how this freewheel works. Do you intend to sell them? I'm wanting to motorize a recumbent similar to one posted at http://www.motoredbikes.com/showthread.php?t=24643 and will need a freewheel front sprocket.

Thanks,
roofman6

[jdcburg]

Roofman6 - you can see more pix and details at Endless-sphere.com • View topic - Dual Freewheel Front Sprocket system. I don't have any intention of manufacturing/marketing the adapter but you are free to copy the design. I had the local voc-tech school fabricate the part to my design. I probably have a thousand miles on it now and it works fine so far (knock on wood). I think the weak link is the Southpaw freewheel as that takes the power of my 350W motor. Using a more powerful motor and/or rough shifting/throttle use may cause it to fail more quickly. PM me if you want more info. jd

[savanne]

I have a 250 w motor and controller, but it has a counter clockwise rotation that can't be reversed. Is it possible for me to fabricate a dual front wheel sprocket drive with the motor driving sprocket on the left crank arm? Thanks.

[Russell]

It looks a lot like the one I built several years ago. Freewheel on chainring and motor. Motor freewheels when pedaling and pedals sit still when under motor power. You can utilize seven gears in either mode.

[jdcburg]

Very similar Russell, except I put the "motor" freewheel down on the chainring on the BB spindle. That way I was able to use a 9 tooth motor sprocket driving a 36 tooth chainring for a 4:1 reduction. To get the same reduction using a 14 tooth freewheel sprocket on the motor I would have had to use a 56 tooth chainring. Also you have the slight extra drag of driving the motor chain when you pedal. But yours is much simpler at the BB because you just bolted the 2 chainrings together, where I have the 2nd freewheel there. Also I was limited to using the Southpaw for the 2nd freewheel as it needed left hand threads. It's all about choices...