Last year with my previous engineering school we worked on a project with a toroidal CVT (continuous variable transmission) but stopped because too heavy, and would have required a complete reengineering for a uni. So I came back on the way of pinion gear.
My idea is a 3 gears hub based on a 29"/125mm uni with a epicyclic train : a lower gear to have something close to a 24"/150mm for off-road, a direct drive 1:1 and a higher gear equivalent to a 36"/110mm for road.
No more ankle gear shift but a cable shifting system with a MTB gear shifter on the T-bar handle
I have done a sectional drawing which is fine but need to go more into details now. May be will go in production in the future …
I still think that for Uni CVT is the way to go. I am ready to lose efficiency to get something “smooth” that will suffer less with the sudden small forward/backward movement changes involved in uni. And yes I need gear down because uphills are spoiling a lot of Muni joy
My wish list still involves the variable transmission(CVT) failing that I would like to see a three speed hub where you could match the overall gearing to suit your choice of wheel size ,cranks and terrain.I have made a fixed geared uni previously http://www.unicyclist.com/forums/showpost.php?p=955157&postcount=1and given the right amount of imagination and drive I plan to make a geared uni in the future.I think the CVT is only possible if high tech industry get involved and given the obscurity of unicycling that doesn’t look likely at this stage,I think the best we can hope for is to adapt idea’s developed for other machines.The “de-vinci hub” came very close.
I’m pretty happy with what I have. IMHO, no need to make it more complex or heavy. Not sure that I could even make use of a whole host of gears?
However, one big improvement would be an easier and more reliable shifting mechanism i.e. move away from the ankle shift (though it is a lot of fun!) and towards a more mountain bike like cable shifting mechanism.
More than any sort of technological improvement, I would love to see the hub become more affordable. You could dream of a new hub with more gears or lighter or whatever but it is not of very much use if only very few people can afford it.
I too would like to see the cost come down, but not at the expense of quality. As has already been discussed on this forum (under various other threads) the cost is unlikely to come down a whole lot because this is such a niche sport that investing in a more automated industrial production process would not be worth while to Florian and/or others. I think the consensus was that if a way could be found to make this hub, and other things using the same parts (i.e. bicycle bottom brackets / hubs) then you might be talking since such items would appeal to a wider market. So for now we’re limited to these hubs being made by hand which is indeed expensive, but also worth every penny IMHO. (Yes I’ve had to sacrifice a bit to afford one myself).
Wouldn’t it be cool if hub internals could slide out of a “hub shell” and then slide into another “hub shell” on a different uni?
I’m interested in getting a Schlumpf at some point, but there’s always the debate over which wheel size to go with. If I could have a 24", 26", and 29" uni in my garage, and one Schlumpf to ride them all, that would be cool. Yes… I’d be Lord of the Schlumpf! :p:D
Each uni would need to be outfitted with a compatible “hub shell”, and at least one crank arm would need to be removed, but that’s fairly easy to do before a ride, while the alternative wheel build is certainly not!
A hand shifter would be cool! Though the heel shifter in so unique.
I would seriously consider buying a 24" muni with a granny gear. I think I like the 24" better than the 20" for muni.(never rode a schlumpf 20") But with a smaller gear those hills might be easier to climb.
On the cost issue, is there a way to expand the market? Right now these highly specialized hubs are sold to a few unicycle fanatics. Could the same mechanism be adapted to specialized mountain bikes or road bikes? If so that might increase the market by 10-fold and bring some economy of scale.
I admit that I do not see another plausible use for these geared unicycle hubs, but if there was one it might make a difference.
Florian made a bike bottom bracket before he made a unicycle hub. But that doesn’t help us with the cost, because he still makes them by hand in Switzerland. The way to cut the cost is to make them in China, which requires lowering your workmanship standards.
My drawing shows this is possible to fit 3 gears (0,724 / 1 / 1,38) with just 1 planetary gear in the standard 100mm bearing centre - centre, but based on a complete different design from Schlumpf current one.
The only thing id like to see at new schlumpfs hub is to do a lighter hub (maybe made of titan?). Just because its so heavy, i own 2 wheel-sets, one with s-hub and one without it . I also have some problems with shifting on technical terrain because sometimes i automaticly shift to lower or higher speed (its because of my feet position on pedals), thatwhy i think handle shifting would be ok.-but i dont have any problems with shifting when i want to shift.
Few weeks ago i emailed to the manufacturers of the CVT NuVinci if they have plans to develop or were already developing a CVT hub for unicycle application. Their reply was negative.
CVT would be in my limited knowledge of unicycles a perfect fit. Going down gear it is an excellent feature and the option to fit a gear at almost unlimited gear position (within the range of the CVT) is just fantastic.
Maybe in the near future we may be able the get more than one gear hub.