Phaser g-boxx style middrive

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crossbreak
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Re: Phaser g-boxx style middrive

Post by crossbreak » Mon Nov 12, 2012 2:10 pm

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

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Re: Phaser g-boxx style middrive

Post by Miles » Mon Nov 12, 2012 2:17 pm

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.

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Re: Phaser g-boxx style middrive

Post by Miles » Mon Nov 12, 2012 2:24 pm

8M PowerGrip from motor to crank?

20t to 80t

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Re: Phaser g-boxx style middrive

Post by crossbreak » Mon Nov 12, 2012 2:26 pm

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.

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Re: Phaser g-boxx style middrive

Post by crossbreak » Mon Nov 12, 2012 2:27 pm

20t to 80t
Thats 203mm in dia. Don't you think this is a bit oversized?

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Re: Phaser g-boxx style middrive

Post by Miles » Mon Nov 12, 2012 2:29 pm

crossbreak wrote:
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
1 chain and 1 belt. With 8M you could use a 10mm wide belt.

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Re: Phaser g-boxx style middrive

Post by Miles » Mon Nov 12, 2012 2:32 pm

crossbreak wrote:
20t to 80t
Thats 203mm in dia. Don't you think this is a bit oversized?
Would match a 52t chainring on the other side :D

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Re: Phaser g-boxx style middrive

Post by crossbreak » Mon Nov 12, 2012 2:35 pm

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:

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Re: Phaser g-boxx style middrive

Post by crossbreak » Mon Nov 12, 2012 2:40 pm

A crank to jackshaft reduction on the right side would not be compatible well with the 3 or 4speed output cassette on the jackshaft

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Re: Phaser g-boxx style middrive

Post by crossbreak » Mon Nov 12, 2012 2:45 pm

I just bought another bafang for €31 (SWXB 24V front) i'll try another "axle to output shaft" on. And my avatar just got capable of 1KW :evil:

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Re: Phaser g-boxx style middrive

Post by Miles » Mon Nov 12, 2012 2:49 pm

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
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.

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Re: Phaser g-boxx style middrive

Post by crossbreak » Mon Nov 12, 2012 2:55 pm

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)

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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 4:09 am

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

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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 4:17 am

Stationary cassette with chain shifting would take up less room. The advantage of having a shifting cassette is constant chain alignment, of course.

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Re: Phaser g-boxx style middrive

Post by crossbreak » Tue Nov 13, 2012 4:39 am

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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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 4:44 am

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

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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 4:45 am

Shall we change the topic title to ES g-boxx style middrive?

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Re: Phaser g-boxx style middrive

Post by crossbreak » Tue Nov 13, 2012 4:52 am

It's not g-boxx anymore, since it doen't need a g-boxx frame. This drive has a lot of potential, so why should we not call it the omnipotent ES drive :D

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.

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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 4:54 am

crossbreak wrote: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
Interesting....

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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 4:58 am

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.
That's why I was thinking to have the motor separate, with the first stage to the crankshaft. 3 shafts including the motors.

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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 4:59 am

crossbreak wrote:It's not g-boxx anymore, since it doen't need a g-boxx frame. This drive has a lot of potential, so why should we not call it the omnipotent ES drive :D
Ok, that's fine.

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Re: Phaser g-boxx style middrive

Post by crossbreak » Tue Nov 13, 2012 5:03 am

I played around with some numbers. If one can trust the e-bikes.ca simulator, the MAC/BMC should be capable of about 100Nm peak torque. It could be 200Nm at the wheel, making it possible to climb every hill up to 50% gain.
Last edited by crossbreak on Tue Nov 13, 2012 5:43 am, edited 1 time in total.

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Re: Phaser g-boxx style middrive

Post by crossbreak » Tue Nov 13, 2012 5:12 am

The derailleur is a very tricky part. Thought about modifying a regular one, turning it around, so that it moves correctly to the gears. The cage could be sawed apart and a new one could be screwed on, being turned to the other side.

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Re: Phaser g-boxx style middrive

Post by Whiplash » Tue Nov 13, 2012 9:26 am

I actually played around with the cassette on the motor as well, but it leaves very little room for the chain to flex due to shifting sprockets between the motor and the idlers and I think in actual practice will not be very stable. I like the idea of moving the crank ring to the other side like you did but I decided it works best traditionally. I have not had any problems with my freewheel crank in over 1000 miles so far and YES it makes incredible torque in low gear! I believe I could climb a 45* slope easily if I could keep the front wheel down! This is the steepest hill I can find locally and it had no problem climbing it pulling only 1200 watts and motor stayed cool after three climbs!

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Re: Phaser g-boxx style middrive

Post by Miles » Tue Nov 13, 2012 2:00 pm


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