Single gearing Unicycle!

So you know Single speed gearings? Those when you pedal harder the gearing go up and up and up!
Is there any person who have made this kind of mod and could share infomation about this.
cause riding around in slow speed is a bit annoying, but the unicycle is fun and small and dosen’t make it hard to get around with and the size is also good.

(Send video if you could or picture etc.)

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The only single geared in production unicycle that I know of is the Huni-Rex
You can apparently buy them in the “Hunirex 2019” group on Facebook.

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They require certain level of skill to ride, (you pedal below the centre of the wheel) and are really heavy and the riding Q factor is really high. Also I found I had a lot of chain slack which is annoying. But yes, it fits the criteria of being a single speed geared unicycle.

I think Erik meant gears that shrink with pressure maybe it is spring loaded or something ? Hunirex is geared but it is still a fixed ratio. But with this spring loaded gear it allows us to have a ratio for fast riding and another for uphills. Sounds like a good idea.

Well, aside from calling something with different ratios “single gearing”, I could not exactly decipher what kind of hubs he is talking about, despite studying mechanical engineering and being interested in bikes.

The only thing I could imagine are 2 speed internally geared hubs on a bicycle - which suffer from all the classic issues of adapting internally geared bike hubs for unicycling: the shift mechanism is designed to transmit torque in only one direction, and they are build for a stationary axle, not a rotating one.

You can’t shrink/ expand gears without shrinking/enlarging the gear teeth, otherwise they will not smoothly engage with each other. If we could somehow make gears change their size, we wouldn’t have bothered with all the shifting gearboxes in this world… It only sounds like a good idea until you think about how to actually make it work.
Continuously variably gearing exists (using belts, rollers or hydraulic coupling), even on a bike hub ( Nuvinci) and that principle would work in unicycles too, but it’s very very hard.

TLDR: There are good reasons why Schlumpf is the only available geared unicycle hub.


Yeah, I think electronic shifting might be the way to go in order to achieve more than two gear ratios, but that’s probably more of a development than is financially viable.

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I would have a hard time trusting electronics to shift a unicycle. If it messes up and shifts at random when you’re going full speed in high gear, that could be your last time riding or possibly walking. But we’ll cross that bridge when we get there, right now 2 speed hubs are just coming back in production!

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While I don’t fully get the original poster’s aim overall.

I think this feels as close to what we’re talking about

In terms of being able to make a mechanical system with multiple steps. I am fairly certain it has been tried. But the watchword is: longevity.

The only geared hubs I know that hold up to actually being ridden are: uni.5 (BlueShift), Schlumpf, and from what I’ve seen Red Menace and HuniRex.

The Schlumpf hub is the only tried and tested shift-on-the-fly system and I am glad it isn’t that easy to shift - as if it were super easy to go up to down, I’d probably never ride it from a lack of trust of being in the gear / state I’m actually rolling in.

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I’m guessing you mean something like a CVT

I don’t think I’ve ever seen an automatic CVT on a pedal cycle.

There are hubs like the SRAM Automatix (The SRAM Automatix 2-speed Bicycle Hub) which changes up and down automatically based on wheel RPM. I wonder whether something like this could be adapted for a unicycle, and how ridable it would be.

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It would be interesting, I wonder if anyone has ever tried it?

I’ve ridden a bike with one of those, I didn’t like how I didn’t know when it will decide to shift, but maybe with more time you know at what speed the shifting happens.

Looking at the pictures, seems to check all the boxes for typical issues:

  • Small gears (because they don’t have an Isis or square taper sized axle to worry about)
  • one directional clutch, here is the big issue, the weights moving out from centrifugal force engaging in a teethed outer wheel is what does the shifting, this would be hard to make work two directional without much play.

As far as I know, the Sturmey Archer S3X (interesting naming…) and Sturmey Archer ASC are the only internally geared bike hubs designed with a two directional clutch mechanism.

I feel like I make this point every time there is talk about gearing, but the real interesting part of Schlumpf hubs is the clutch mechanism, small play and fast engagement is something we really need on a unicycle, but is not as important on a bike. I think for skilled riders one could make slight compromises and use a worse shift mechanism, but not too much…