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Old 2018-02-04, 04:32 AM   #1
OneTrackMind
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Hub geared heaven

waaalrus linked this site as an aside on another thread.

Look at the drawing of the "front wheel drive hub".

Seven to twelve hub gears. 100 mm wide. 2 kg. Too good to be true?

Not real yet I'm sure, especially as they have drawn it with radial spokes.
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Old 2018-02-04, 06:17 AM   #2
Vogelfrei80
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I' ve already asked them to write here to get our help developing a fixed wheel one hub
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Old 2018-02-04, 03:46 PM   #3
rich
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Aren't most (all?) the multi-gear IGH systems like Rohloff based on each gear overdriving the others? How can that work in both directions such as for a unicycle?
You'd end up with multiple forward speeds and only one fixed ratio (or a freewheel) for reverse torque.
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Old 2018-02-04, 05:30 PM   #4
finnspin
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Quote:
Originally Posted by rich View Post
Aren't most (all?) the multi-gear IGH systems like Rohloff based on each gear overdriving the others? How can that work in both directions such as for a unicycle?
You'd end up with multiple forward speeds and only one fixed ratio (or a freewheel) for reverse torque.
The gearing itself does not care which way it is turned, the only thing that does is the freewheel integrated into most Geared bicycle hubs. If you eliminate the freewheel, any conventional gears don't care which direction you turn the input shaft, the output will always spin with the (rotational) speed of the input shaft divided by the gear ration.
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Old 2018-02-04, 11:35 PM   #5
rich
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Agree with you about input and output for one set of fixed planetary gears.

But freewheeling is integral to how these hubs can have changeable ratios, with some gears overdriving others.
The freewheel is not totally its own entity; the clutches that allow such a large variety of engagement of individual ratios also act as freewheels therefore don't engage in reverse.

At least in my understanding of how for example a Rohloff works.
https://www.youtube.com/watch?v=s4UpwoDmOb4
12:45 mentions the freewheel as a specific part. Even if you deliberately seized this in place, because of how the other clutches work you still wouldn't be able to drive it in reverse in most (any?) of the ratios.

I suppose this is to avoid complexity, if the clutches were made to be more complex than engagement pawls and a spring then it could perhaps be made to work.

The old Sturmey Archer 3 speed works in a slightly different way, you can hear the clicking when pedalling in the the higher ratio as the other ratios are overdriven and are effectively freewheeling. It still doesn't work in reverse without modification (I believe these can be converted to 2 speed fixed?)

Don't get me wrong, I'd love to see it! Build me a three speed fixed hub and I've got thousands of pounds you can have!

Motor windings and strain gauges on the input side would be essential though, there is not much point gearing these things down!

Edit: Justin LE's solution is probably the best one. http://www.unicyclist.com/forums/sho...d.php?t=119436
One ratio with variable assist. If you've ever ridden a half decent electric bike with a strain-gauge based proportional assist you quickly realise it doesn't matter which gear you are in as long as it's tall enough so you don't spin out!

Last edited by rich; 2018-02-04 at 11:42 PM.
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Old 2018-02-06, 08:44 AM   #6
Vogelfrei80
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Quote:
Originally Posted by rich View Post
Agree with you about input and output for one set of fixed planetary gears.

But freewheeling is integral to how these hubs can have changeable ratios, with some gears overdriving others.
The freewheel is not totally its own entity; the clutches that allow such a large variety of engagement of individual ratios also act as freewheels therefore don't engage in reverse.

At least in my understanding of how for example a Rohloff works.
https://www.youtube.com/watch?v=s4UpwoDmOb4
12:45 mentions the freewheel as a specific part. Even if you deliberately seized this in place, because of how the other clutches work you still wouldn't be able to drive it in reverse in most (any?) of the ratios.

I suppose this is to avoid complexity, if the clutches were made to be more complex than engagement pawls and a spring then it could perhaps be made to work.

The old Sturmey Archer 3 speed works in a slightly different way, you can hear the clicking when pedalling in the the higher ratio as the other ratios are overdriven and are effectively freewheeling. It still doesn't work in reverse without modification (I believe these can be converted to 2 speed fixed?)

Don't get me wrong, I'd love to see it! Build me a three speed fixed hub and I've got thousands of pounds you can have!

Motor windings and strain gauges on the input side would be essential though, there is not much point gearing these things down!

Edit: Justin LE's solution is probably the best one. http://www.unicyclist.com/forums/sho...d.php?t=119436
One ratio with variable assist. If you've ever ridden a half decent electric bike with a strain-gauge based proportional assist you quickly realise it doesn't matter which gear you are in as long as it's tall enough so you don't spin out!
I'm also inquiring Bimoz http://www.bimoz.ch/ to power a Huni-rex http://unicycle-c-1/roadtourbasket-c...ack-p-650.html
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Old 2018-02-05, 12:12 AM   #7
waaalrus
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Quote:
Originally Posted by OneTrackMind View Post
waaalrus linked this site as an aside on another thread.

Look at the drawing of the "front wheel drive hub".

Seven to twelve hub gears. 100 mm wide. 2 kg. Too good to be true?

Not real yet I'm sure, especially as they have drawn it with radial spokes.
Also ISIS. We've been discussing this for a few weeks on the Freewheel Unicycle Chat Facebook group and it was Robin Whitfield who made the discovery. I posted it on Unicycle Chat but there was not much discussion. I'm planning to order a front end if can be equipped with disc brakes. That's the one downside to Justin's design and is almost essential to riding freewheel unicycles.
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