Phaser g-boxx style middrive

CSK20 was for 6:1.
I'm aware of this. But since it's 47mm in dia a hub shell would be needed to connect it with both the jackshaft and the sprocket, which adds width.

If we are going with 2 stages from motor to jackshaft then the jackshaft could be 360rpm. 52t to 13t freewheel for the pedals.

That would mean for example 4:1 from motor to the BB-coxial sprockets and 4:1 to the jackshaft @360rpm would mean a motor speed of 5760 :twisted: you wanna use an 80-100! :mrgreen:
 
crossbreak said:
That would mean for example 4:1 from motor to the BB-coxial sprockets and 4:1 to the jackshaft @360rpm would mean a motor speed of 5760 :twisted: you wanna use an 80-100! :mrgreen:
Not me personally... but it seems to be the weapon of choice around here.

Anyway, these are all options. The thing is to accommodate as many needs as is possible with this.
 
This drive anyway can not use hyperglide, since the sprocket cassette is turend the wrong way... wait.. it can be used if the cassette is turned around, but that would be a mess up when using an additional rear derailleur
 
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 :mrgreen:

360rpm 3:1 then 4:1 is 4320rpm.
 
8M PowerGrip from motor to crank?
Would be too wide I guess. remember, we already put 3 sprockets and chains on the left side of the cranks :D

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
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.
 
1 chain and 1 belt. With 8M you could use a 10mm wide belt.
with the pedal to jackshaft overdrive on the right.
Would match a 52t chainring on the other side
that indeed gains style points :D

A 500W MAC/BMC/PUMA with a "axle to output shaft" /jackshaft mod, with the pedal to jackshaft overdrive on the left would be very simple. Insert a good heat connection to the housing, making it capable of 1000W+
continuous. And build it into a folding bike :lol:
 
crossbreak said:
A crank to jackshaft reduction on the right side would not be compatible well with the 3 or 4speed output cassette on the jackshaft
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.
 
So far I can summarize:

We found out that a front-derailleur-only setup, with a jackshaft overdriven by the cranks, makes much sense, since it helps us on some issues:

- the wheel drive chain can be enclosed
- there is no more need of a large and ugly chainwheel on the BB or for weak and tiny 11T sprockets at the rearwheel
- the reduction from the motor to the cranks gets another meaningful stage compared to a GNG/cyclone style drive

all of these points where already met by the deign posted first. But the designs we discussed are simpler (ok the BB-coaxial reduction isn't quite easy to make)
 
Ok. Homing in on a plausible specification.

Pedal drive to jackshaft: 42t - 14t (or 39t - 13t) gives 3:1 ratio which is still reasonable for driving the motor's freewheel. Nominal speed of 280 rpm at the jackshaft.

3 speed drive from jackshaft to rear wheel: 14t, 20t, 28t, to 20t gives ratios of 0.7, 1 & 1.4

Speeds with 665mm dia wheel: 15.3mph, 21.8mph & 30.5mph.

2 stage drive from motor to jackshaft:
280 * 9 = 2520 rpm
280 * 12 = 3360 rpm
280 * 16 = 4480 rpm
 
The advantage of having a shifting cassette is constant chain alignment, of course.

Guess this is not so dramatic, since the chain length is enlarged and there are only 3-4 sprockets.


Made a plausible specification for the MAC/BMC/PUMA:

crank to jackshaft (or macshaft :mrgreen: ) : 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
 

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