Anyone know anything about this? Adapted to a uni ?
http://www.freeridehubs.com/email_notification_freeridehub_release.htm
I watched their video. It’s mainly a guy going downhill on a mountain bike. He doesn’t even pedal for the first minute or so.
The idea looks interesting, but the design looks complicated and probably heavy.
Still, variable gearing would be very nice.
it’ll be interesting only if we can get rid of freewheel (that is the gearing work both ways).
I have asked another hub builder if we could get rid of the freewheel and answer was “no way”.
I would like to see the general principle of this hub (how the continuous gearing is working)
Good point. I forgot about the “built-in” freewheel. Oh well.
Yes, continuously variable gearing on a unicycle would be very nice. It’s the Holly Grail of gearing designs.
A jump in gear ratios is difficult to handle on a unicycle. The sudden jump from 1:1 to 1:1.5 or from 1:1.5 down to 1:1 is challenging to adapt to. A continuously variable shift would be much easier to handle on a unicycle.
Yet another thread on my all-time fav topic!
The best promising technology is the NuVinci bike hub:
http://www.fallbrooktech.com/03_Bicycle.asp
The internals can shift in any parameter, forward, backward and even stopped. It goes from 1:1 to 3.5:1, a very healthy span of gear ratios. The design is essentially already a fixed gear, but there are two roadblocks.
In its current state there is no way to attach a fixed cog. But this is minor.
The biggest design issue is that the shifting mechanism requires a cable running into the axle, such that any unicycle application would have to have the cable running out not only through the axle but through the cranks as well, and you’d be pedalling inside of the cable loop. If we could rig it up for a uni axle, I could live with that.
Someone would have to purchase a unit, dissassemble it, and fabricate a whole new axle system. But the guts of the design are there and working.
The Freeride hub is by Nupace. I’m not sure if it is based on the Fallbrook design used in the NuVinci hub or not.
Well, how about linking the cable to the hub at the bearing holder (i.e. inside your legs) and using a rotating joint to account for the movement of the axle? e.g. something like the rotor head that allows BMX handlebars to spin 360 whilst being connected to the rear brake.
I’ve also seen bicycle hub brakes that appear to have the cable not coming directly out from the axle, so something like this must already exist in some hub designs out there.
Personally, I’d think a cable shift mechanism like this could be quite appealing for existing style geared hubs too; you can then keep your feet more firmly planted whilst shifting.
the hub that was the orignial reason for this pot appears to have a collar around a shaft on the axle which is rotated by acbles, you can see details towards the bottom of that page. This could be neatly tucked inside the frame, or between the frame and the hub
Note the 10mm axle on NuPace hubs. Not friendly to a unicycle hacker.
It’s another interesting design, for sure, but you’d still have to re-fabricate the whole hub to even attempt a fixed-gear version.
Someone have an angel to finance the fabrication of a radio controlled servo-shifting NuVinci with a redesigned axle?
It would be really interesting to fabricate something similar for unicycle usage. I just saw this one the popular science website: http://www.popsci.com/popsci/flat/bown/2007/recreation/item_98.html#=rss
I’ve had a look at the duvinci hub and the specification says it has a range of0.5 underdrive to 1.75 overdrive.on a 26" unicycle that would give you the equivelant of 13" wheel through to a 45.5" wheel surely enough to satisfy anyone.To be adapted for a unicycle you would have to replace the axle with a hardened crank axle shaft,the input has to be driven by the crank shaft and the gear ratio changer mechanism would have to be re-engineered to exit inboard of the the crank ends.Without having seen one of these hubs in the flesh I doubt it would be possible to carry out these mods however if they decide to cater to unicycles I’m sure they could produce a unicycle version without too much trouble.I want one.
my only question when it comes to the nuvinci hub is: can we get rid of free wheel?
if ok then I think we can do something with it without many changes.
here is what I had in mind: based on Pete Peron’s initial idea except that the chains are on each side of the frame and that the secondary axle is further off.
In that case a slightly modified CVT could be used provided that the free-wheel is off.
for sure it is not that simple but this sketch is to illustrate the general idea I had had in mind for 2 years (but unable to find someone to build a model - a model because I suspect there are some problems with this design-).
wobbling bear the freewheel on the duvinci hub is part of the sprocket carrier like you would find on a derailier type hub so that is easily solved.your design will work but the more components you use the heavier and more complex it becomes also chain drive should be avoided if possible due to maintainance issues.
yep but what I want is a XC machine to dash through forrest trails (not for trialsy things) … So I will be ready to accept the weight penalty (and get ready to fix chains again and again). I am more worried about influence of gear change on balance.
It weighs 4kg, which at that offset would be horrible. Surely it’d make more sense to have it in between the legs of the frame, above the wheel? Assuming you’re thinking a 26" wheel, there’d be loads of room if you used a 36" frame.
Joe
you mean the CVT weighs 4 kg!!!? (I was not aware of that 
)
Without this consideration there is a reason why I wanted to experiment with a different location: I am afraid of balance problems if the secondary axle is vertically aligned with the main axle … But I may be completely wrong!
you are right I am thinking of a 26" wheel. So brainstorming and experiments are welcome!
Weight from
http://www.fallbrooktech.com/NuVinci_Experience.pdf
It’s much easier to balance with a heavy weight on the line of the frame than if you have a weight off axis, or at least it is if it’s luggage strapped to the unicycle, I’d assume the same to be true for this.
Joe
I see … IMHO 4kg is too much for a CVT on a unicycle. (that makes at least a 11kg unicycle … well My Old fashioned Coker weighs around that … but …)
other options?
wobbling bear, the freewheel is screwed onto the NuVinci hub. The hub itself is already set up for fixed gear apps, and can operate in both directions.
dangerdog, the necessary axle mods are more complex than appear. If it were possible, this hub would have been modded for unis by now.
But it is possible. All I said earlier was that it will take resources (money & metal) to modify the existing design.