Miles' new drivetrain (2.5D schematic)

Miles

Miles

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Moved from E-Bike Technical section 27/11/08

Possible drivetrain to combine pedal and motor power at chain,

Double reduction with toothed belts, from the motor, crossing to join the pedal chain.

Intermediate motor pulleys not coupled to BB axle....

Overunning clutch-bearing on the final pulley; freewheeling crankset.
 
That's just cool.

:mrgreen:
 
Thanks Miles, I was having trouble visualising your description. That's a very neat arrangement!
The only challenging bit would be to get decent chain wraparound on the final pulley, but Cyclone seem to manage it OK.
 
Just looking at this again Miles, will there be enough clearance for two timing belts mounted side by side on the left crank? What width of belt were you thinking of running?

Another idea came to mind while trying to get to sleep last night. Probably pie in the sky, as most of my late-night ramblings are, but do you have any idea how much torque these one-way needle bearings can take? Would it be possible to mount the pedals on such bearings, so that the bottom bracket spindle is free to rotate independently?
 
Hi Malcolm,

I'm not thinking about power levels greater than 1kW, here.

What we need is a source of straight crank arms (Spa cycles still have a few TA ones) - then we could use longer axles without excessive Q factor.

Belt widths would be 15mm or less - maybe even a chain for the second stage - so, about 30mm width needed. It should be doable.

Not sure I understand your one-way needle bearings idea. How would you keep the LH & RH cranks in sync?
 
Malcolm,

Another variant on the mid-drive concept:

Motor to toothed belt pulley on LH side of jackshaft.

Epicyclic reduction inside this belt pulley.

Sprocket to drive chain on RH side of jackshaft.

Not sure if the freewheel would be better on LH or RH....

This is better than the Cyclone/Elation kits because it avoids having the epicyclic as the primary reduction. The Ecospeed uses something along these lines.
 
Hi Miles,

Between the time I download this and get ready to make a few comments you post another design.

I really like the using the Crank for a large pulley. It fits aesthetically and practically. I think you will have a hard time fitting two belts but since you are getting most of the reduction from the first stage I don't think a chain for the second stage is a big deal.

Might be easier to use dual chains than to get the proper wrap with an idler etc. What impact does a tight wrap or idler have on efficiency vs a second chain?

I think I can get you a couple of Heinzmann GB's if you can use them.

I am very impressed with your designs but even more impressed that you can build them.
 
MitchJi said:
What impact does a tight wrap or idler have on efficiency vs a second chain?
Click to expand...

For normal pedalling, my guess is that the idler set-up will be not that much less efficient than a single chain, mostly the added drag of the freewheel/one-way. This is the kind of thing that we need to test for, though.
 
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