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Well, the 3 speed survived a full week of abuse and crashes with only a few shifter cable adjustments required. Best thing was running into Neptune, who took me under his wing back at Burning Man in 2005 when I was a total beginner still learning to freemount.
Here he is after getting the hang of it just prior to a group uni ride around the black rock city.
Hello, after reading all the posts I could find about geared unis I think the best chance to get a multigear hub would be to modify the NuVinci hub. It seems the easiest way creating as few as possible customized parts.
Using NuVinci tech won’t allow it to be sold but if we concentrate our efforts we could make a group to share costs and have the custom parts machined with high precision for a relative low cost.
Using a chain seems a temporary solution for unis and, as I’ve seen, theoretically adapting the Nuvinci would just need a customized roller ramp, unfixing the hub shell to the axle and fixing the sprocket part to the axle.
Then taking out the shields and sprocket to shorten the 135mm length to 100mm and fixing the 42mm bearings with welded nuts with ISIS ends, it would be theoretically ready.
Not sure about the final cost, but if enough people get into it, a <900$ solution including the NuVinci hub price seems possible.
I think this thread its great but maybe we should open a new thread focusing in creating a CVT uni hub.
I know this is an oldish post and you might have worked this out for yourself by now, but as the thread has been resurrected and I’ve read it for the first time…
Except that at the point the hub takes over and spins the pedals at a higher rpm, the clutch is still engaged. It still wants to spin the hub at the same rpm as the sprocket (whilst the hub wants to spin the sprocket faster). This will result in the hub locking up in just the same way as you identified earlier when running two gear sets with different ratios.
No way round this one unfortunately - the only point a clutch will work is if the hub is in 1:1 mode, which kind of defeats the point of a gearing system (if you had a hub which geared up rather than down you’d get the lock up when pedalling forwards).
That post appears to make exactly the same point as independently determined by the OP of this thread. The post you’re responding to suggests a solution to that issue (previously also mentioned by the OP) of using a customised roller ramp so that full drive torque can be transmitted in either direction. The remaining issue then is that it seems this would result in a significant amount of backlash. I do also think the use of the word “just” in conjunction with a list of not exactly straightforward procedures is rather unfortunate!
Well, the slippage won’t be so much if we modify the ramp, and the grade of backlash is relative to the forces implied and the allowed slippage. Also the fluid in use has a lot to do with all that. Why not looking for a compromise between them?
Of course it won’t have a perfect grip like a geared one but a little fluid response is not so bad considering the benifits.
I used “just”, because compared to create a whole CVT system, fixing and unfixing those parts is relatively easy by modifying them or creating new customized ones. The Nuvinci system is beautifully simple and taking it as a starting point could be a good way to achieve a real CVT unihub.
Anyway it seems more feasible than magnetic ones Oh man, patents surfing is so cool sometimes…
Hey and thanks for chipping in. I reread and rethought everything and think that it still stands. The system would indeed lock if you were to be pedalling backwards if that’s what you were getting at, but so long as you are pedalling forwards and only have the torque in reverse, then it it should be fine and would allow you to use all 3 gears.
Assuming you are pedaling forwards, the clutch only comes into play for the brief time when you switch from forwards to reverse torque and will remove the backlash during this period with a 1:1 ratio between the sprocket and S3X shell. Once the backlash is absorbed then the sprocket continues to rotate forwards faster then the S3X hub shell, which will cause the freewheeling clutch between the hub and sprocket to simply freewheel.
However, the moment you switch from a reverse to a forwards pedal torque, then there would still be play in the pedal in that direction. So it’s like having 1-way backlash. Not perfect but I imagine an improvement over the 2 way backlash we have now!
Plus, when you are in the 1:1 gear, then backlash would be eliminated both ways, allowing you to ride in high speed mode with no play in the system. So if I’m not mistaken the summary effect of adding the freewheel would be as follows:
Without Freewheel:
Fwd Backlash Rev Backlash Pedal Backwards?
1st gear (0.625) YES YES OK
2nd gear (0.75) YES YES OK
3rd gear (1.00 YES YES OK
With Freewheel:
Fwd Backlash Rev Backlash Pedal Backwards?
1st gear (0.625) YES NO Locks
2nd gear (0.75) YES NO Locks
3rd gear (1.00) NO NO OK
So the freewheel might make sense and be rideable. The system might be a bit strange in its feel, but I agree that I apply reverse torque to my unicycle all the time when riding. Only occasionally do I actually ride backwards or idle.
Keep us posted if you reduce this design to practice.
Fair enough - I agree with your analysis. Fine if you don’t want to ride backwards or idle then - to be fair I can’t do either of those, so it would suit me just fine!
Hey everyone, not much update on the actual hardware since it’s been suprisingly reliable so far. As alluded to previously, the device is on a holiday trip around France with me and An’So right now.
Here is Romain of the Cri-Du-Kangourou shop who got it on first mount. The second photo is Robin riding along the Rhone river in Lyon. He’s got a great inventive mind with lots of projects on the go so we had plenty of fun stuff to talk about.
We’ll be going to Paris tomorrow and there is apparently a unicycle gathering/ride planned for Tuesday, for anyone else in the area who wants to give this a try.
Yes indeed. It turns out that the aluminum ISIS spindle on the Eclipse hubs eventually seem to give to the point that the crank goes on too far and the crank bolt bottoms out, so it can’t be tightened anymore. The exact same thing happened to An’So’s freestyle uni too. We just filed off 1mm of metal from the end of the spindle and now the cranks can be properly snugged up and don’t creak.
Well we just need to get a shot the next time I accidentally slip into the neutral gear, hopefully before landing on my ass
Oh man, patents surfing is so cool sometimes…
