OK… I am an idiot who has not ridden in over 25 years… So could someone please tell me why this won’t work for us?
Short answer: because it’s not a unicycle hub.
Slightly longer: The “axle” part would have to be remade to attach to cranks. Then there’s the slight problem of how the hub freewheels, and is not built to be driven in either direction.
This is a freewheeling bicycle hub. Sturmey Archer is developing the S3X, a fixed internally geared hub, but even with this hub you’d need to modify the axle to be able to attach crank arms.
Also I’m not sure, exactly, how one changes gears on this hub? I’d imagine, like the KH/Schlumpf hub the axle is hollow but I bet there is some sort of cable that runs down that hollow axle and shifts the bits back and forth (I’m not an engineer, sorry). So the other, big question, is how you could even do that with a unicycle as that cable would come right out where the cranks attach!
I figured it would be a one way deal… and i am sure it could not handle the punishment a lot of you guys dish out. Good point about where to put the cranks… what about a 1:1 gear right above it? It would be nice if we could figure a way to make it work… 1300+ is way too much.
I believe they can be routed down the frame… and you could have a shifter any number of places… especially on a commuter.
Another problem with most bike-oriented internally geared hubs is that they are designed to gear down. The S3X has a 1:1 gear and two lower gears; that would only work for us if we combined it with a chain drive. And the shift cable comes in through the outside of the axle, in much the same way as the Schlumpf, but there’s no way to get a cable to that location on a unicycle, and I can’t imagine being able to use foot-controlled shifter buttons (as on the Schlumpf) to manage a 3-speed hub.
I imagine this price “could” come down quite a bit if they were not all hand made! But geared unicycle hubs are not a “hot” commodity in the big scheme of things so it is probably unlikely these will ever be mass produced (I’m too lazy, but I know there is a thread almost like this on this forum somewhere). We’ll have to keep our eyes on that Sturmey Archer fixed-gear hub however. I bet a few intrepid unicycling folks will conjure up something.
Those two aren’t a problem in all cases. Most bike hub gears have the direct 1:1 drive in the middle of the range, with some gears above that and some below. At least two of the common kinds (Shimano and Rohloff) have the gear change mechanism around the axle inside the frame - the Shimano twists the ring round the axle and the Rohloff has a sort of push/pull sequential change I think.
But the running in both directions IS a big problem at least with modern bike hubs (they “cheat” by using ratchets to freewheel unused gears, so cannot be driven backwards by design). And even then, the modifications to have a unicycle-type axle would be pretty extensive. I think there’s hope for using a fixed-gear hub like the old Sturmey ASC or the new S3X (or Davinci?) in some sort of jackshaft arrangement, with the gearbox up by the crown. Although the ASC apparently had a fair amount of slack (enough to annoy fixed-wheel bike fans) so if the S3X is similar it might make for a rather sloppy unicycle. The Davinci design however could potentially have no slop…
Rob - Now we’re talking… I like your “jackshaft” idea. I realize that that it would be a one way uni. This is getting good… let’s get all our ideas together… I am sure one of us can put it on paper and I will have it built. The currently available hubs are uber-expensive (partly) because of a lack of competition. Yes I know am about to hear it… those are hand made… there is not enough demand…blah blah blah taurus-cacas. It’s just like everything else… they get what they can for them until they can’t… economics 101. I believe there are enough people on this forum with enough knowledge to put a more affordable GUNI together for the rest of us… or at least fail impressively.
The reason why they’re that expensive is like what MuniSano says - they’re not selling as many as bicycle hubs. Unless there’s a solution which allows for bike hubs to be adapted into unicycle hubs or if road unicycling starts picking up in popularity, it’s really unlikely the price would drop by that much.
Still, if you consider the fact that KH unis used to cost upwards of 1k in the beginning (well at least here it does) and you can get one for about half the price now, who knows? I’d be happy for a price drop
The jackshaft idea as applied to unicycles was first successfully built by Pete Perron. You can search and find a few of his incarnations. They are works of art. You are welcome to my complete drawing set for the original uni.5 hub (which is on my website) and I have the AutoCad 2k2 drawings as well. Then there are the drawings for the production hub I tried to make several years ago. This set includes the drawings for the matching SH29 frame which makes it tool shiftable, but not shiftable on the fly. There is also a drawing for Steve’s tilt rail adapter which will fit KH saddles as well as earlier models. There was a guy in the Detroit area who was going to build one of my hubs and then check into having a run by a job shop in the MoTown area. I haven’t heard from him recently.
I have all of these zipped in .ps, .pdf, and .dwg formats. Let me know if you want them. You can also search this forum and find the history of geared unicycles from inception to production.
Harper, your project is just awesome! I wish I had the tools to machine all parts, but would be too expensive to pay for it!
Another project that I found a while ago:
Stills hard to make it! Geared hubs are always complex. I saw in Denmark a unicycle with a gears system but not in the hub! It looked really nice and was really fun to ride. Does anyone have this project?! I will try to find pictures…
Both of your links illustrate Frank Bonsch’s hub which he was building at the same time that I was making my two prototypes. He built his into a 28" wheel which he ran in fixed gear mode at something like 1:1.57, slightly better than the exact 1:1.5 ratio I used. For both his and Florian’s designs the tire is worn much more uniformly because of the odd ratio.
The axle on a bicycle hub is fixed. The chain cog is driven. Massive modifications need to be done to change the driven element to the axle. This is the main mechanical reason that it is completely impractical to use these hubs in anything but a chain driven unicycle such as a giraffe.
HARPER - that’s awesome… where is it? how much did it cost you to put together. Also what happened to the one you built with off the shelf parts? Blue Shift is beautiful.
Harper! Can you send the files to me? (just send everything you have). cd at bluetreesoft dot com. I was just admiring your work a few days ago (someone twittered me it asking if I had seen your site, which, of course, I already have).
I’m incredibly interested in geared hubs, and in manufacturing my own. I would love to make a CVT, but the use of belts would probably slip.
I now have a mini-machine shop in my garage, so I’m hoping to learn enough in order to build some sort of geared unicycle. Currently, I’m a pretty green machinist.
I have BlueShift in my basement. It has one of the original hubs and still works fine. Uni.5 I think is still owned by Bill Gilbertson, Gilby’s dad. The parts costs are listed on the website. I guess I put $3600 of time and parts into the pair of prototypes. A job shop could do it for less, especially in this economy and especially in a depressed industrial area like Detroit. I think Steve Howard said he could make a run of 10 or more for around $400 each when he still had a shop but that seemed low to me.
The production prototypes ended up in a couple of different places. Steve reworked one but kept the Chinese gears in it. It’s presently broken in Arizona with a guy who rode the RTL but I think Mike Scalisi still owns it. It needs to be properly reworked with stock gears, good bushings, and a hardened axle.
The other production hub Dave Stockton built one of his super Coker wheels on. We gave that one to Kris Holm. HardCoreCokerRider had it in NYC and it busted. I rebuilt it with stock gears and proper sintered bronze bushings. I made a 17-4PH SS hardened axle for it, too. It went to Ottawa with Ryan Atkins for a while but was shipped to Arizona to be used to train for RTL when the other one broke. I think that one still works and it would surprise me if it is damaged in any way. It should be very robust in its present form.
The history of all of these hubs is floating around in the RSU forum and can easily be searched.
Oops - it’s called Nuvinci.
And no, the jackshaft thing wasn’t my idea - I was just pointing out that a bike-type fixed-gear hub COULD be made to work on a unicycle if used in that way, rather than trying to convert it into a unicycle hub.
That externally-geared unicycle you mentioned was owned (and built?) by a German or Austrian lady I think. It had quite a high gear compared with the Harper or Schlumpf hubs. There was a thread on here some time ago about it breaking, but I haven’t heard anything since.
if you mean this: http://www.unicyclist.com/forums/showpost.php?p=936110&postcount=26
this was built and owend by jogi (member name), but most of time it’s been ridden by enaddi. both are from germany
it’s broken now, because of some “abuse”… (i think somewhere at the axle)