Would be too wide I guess. remember, we already put 3 sprockets and chains on the left side of the cranks8M PowerGrip from motor to crank?
it depends on if the motor is coaxial to the jackshaft. if so, the sprocket can be at as big as the motor and still look okay.4:1 is probably too much for crank to jackshaft on the motor side. A large sprocket on the end of the jackshaft would look a bit naff IMO
Thats 203mm in dia. Don't you think this is a bit oversized?20t to 80t
with the pedal to jackshaft overdrive on the right.1 chain and 1 belt. With 8M you could use a 10mm wide belt.
that indeed gains style pointsWould match a 52t chainring on the other side
True. The chainring would be offset quite a lot outwards and the sprocket on the rear wheel would need to be close in, so you'd still need a dished wheel = yuk.crossbreak wrote:A crank to jackshaft reduction on the right side would not be compatible well with the 3 or 4speed output cassette on the jackshaft
Guess this is not so dramatic, since the chain length is enlarged and there are only 3-4 sprockets.The advantage of having a shifting cassette is constant chain alignment, of course.
Don't forget we're using heavy duty 1/8" bike chain.... But I agree that, with 3 sprockets, shifting the chain shouldn't be a problem.crossbreak wrote:Guess this is not so dramatic, since the chain length is enlarged and there are only 3-4 sprockets.
Interesting....crossbreak wrote:Made a plausible specification for the MAC/BMC/PUMA:
crank to jackshaft (or macshaft ) : 48T to 13T
front sprockets: 14-20-27-34, increase rates: 43%->35%->26%
rear sprocket: 25T
highest crank to rearwheel ratio: ~5:1, lowest: ~2:1
average macshaft rpm: 295 @80rpm crank cadence, motor: 1772rpm
That's why I was thinking to have the motor separate, with the first stage to the crankshaft. 3 shafts including the motors.crossbreak wrote:I'm still not sure if the 2-stage reduction easy to build. The space on the left side is quite limited. I made a CAD model of a very similar drive once, but I can't find it atm, but I needed at least a 153mm BB.