Phaser g-boxx style middrive

[Miles]

One could also just use a normal front derailleur. Keeps the possibility to use an enclosed chain to the wheel and is even simpler to build.

That was my first thought. Both seem doable. A lot less work than a phaser type mech.

The big advantage with the Phaser is that it allows a large range in few steps. A bit like having a front and rear derailleur in one.

 

[crossbreak]

Shimano MegaRange MF-HG40 - 7 speed jumps from 24T to 34T. Guess this is the most which might work.

The phaser style gearbox is no possibility for am ES-BB drive. But his one would be.

 

[Miles]

A large ratio between the pedals and jackshaft would allow all the gears to be underdrive. This way one could get away with a single stage from motor to jackshaft, without needing too large a motor.

 

[crossbreak]

4.5:1 from cranks to wheel should be possible. 1:5 would be better. That would also be the least reduction from cranks to jackshaft. Seems like one would have to use the #25 chain then and a 2000mm dia pedal sprocket (cause of the little tensile strength of the #25). which is not as compact as I would like.

 

[crossbreak]

or duplex I would rather like to use a simple 40T crank sprocket on the left side. Just buy and install.

 

[Miles]

4:1 is practical with bike chain. 56t to 14t. Jackshaft speed would be 360 rpm. 14t, 20t & 28t cassette?

 

[Miles]

6:1 is possible with #219 chain. Jackshaft speed 540 rpm.

 

[Miles]

540 rpm would give 40mph at 1:1, speeds below that would be underdriven (26" x 2" wheel)

 

[Miles]

So, 6:1 overdrive from pedals to jackshaft.

14t, 20t, 28t cassette.

36t sprocket on rear wheel.

3 speeds: 15mph, 23mph & 30mph approx.

 

[Miles]

540rpm x 5 = 2700rpm at the motor shaft.

 

[crossbreak]

Where would the freewheel for the pedals be?

 

[crossbreak]

It would also be possible to use a rear derailleur as front derailleur. The tensioner arm would have to be fixedThis way the shifting would not be so painful.

 

[Miles]

Where would the freewheel for the pedals be?

On the cranks.

 

[Miles]

If you wanted 2 stages to the motor, you could use the left side of the crank axle for the intermediary stage. Pedal & Motor inputs would come from either end of the crank axle to either end of the jackshaft.

 

[crossbreak]

If you wanted 2 stages to the motor, you could use the left side of the crank axle for the intermediary stage.

good point. having the freewheel on the cranks it would mean that the pedal chain is always hauled :? I would rather go for a 13T freewheel on the shaft for simplicity.

 

[Miles]

As we discussed in the other thread though, the bigger the ratio from cranks to jackshaft, the greater the resistance felt in the freewheel isolating the motor when pedalling without it.

 

[crossbreak]

jep. that why i like your 2stage coaxial reduction idea

 

[Miles]

..having the freewheel on the cranks it would mean that the pedal chain is always hauled :? I would rather go for a 13T freewheel on the shaft for simplicity.

Then it's spinning at 540rpm = noisy

 

[crossbreak]

Then it's spinning at 540rpm = noisy.

what about a roller freewheel?


In the 2-stage drvie, one could build the motor coaxial to the jackshaft, like in the geared outrunner hubs.

 

[Miles]

You could use a sprag clutch because of the torque reduction, though.

 

[crossbreak]

Then it's spinning at 540rpm = noisy.

one would not go for a 1:6 crank to jackshaft overdrive in a 2-stage drive.

 

[Miles]

You could use a sprag clutch because of the torque reduction, though.

CSK 20 either end of the jackshaft?

 

[Miles]

one would not go for a 1:6 crank to jackshaft overdrive in a 2-stage drive.

Probably not. In that case, it would make sense if the final stage was 1:1 in top gear?

 

[crossbreak]

CSK20 is only rated for 0.5Nm: http://www.stieber.de/pdf/stieber/CSK-manual-de.pdf

 

[Miles]

50Nm