Inspired by the car-wheel unicycles, I started imagining a unicycle with a sport bike motorcycle wheel (maybe something like a 110/80-18, which is 2.5 x 18 inches) and a geared hub. Since sport bike tires have a profile designed for the kinds of highly banked turns that such motorcycles are known for, and they have enough weight to store a ridiculous amount of energy on a unicycle, they sure would make for an interesting ride!
Since the tire is nearly 25 inches tall, if there were a way to equip it with a Schlumpf hub that could handle a wheel of that weight, it would have gearing that is only slightly higher than a standard 36er. If I were to have any luck at all cornering a motorcycle-wheel unicycle, I think it might be life-changing for me, lol.
If an internally-geared motorcycle-wheel unicycle is feasible (and I could find a builder who is up for the challenge), I might have to make this my next project! What are your thoughts? Do you think this type of unicycle would be possible? Or would the weight and inertia of the heavier motorcycle wheel nearly guarantee that the geared hub would fail? Without the geared hub, I don’t think I could go fast enough on a 25” wheel to be able to take advantage of the benefits of the tire profile (to any significant extent) when turning, which is why this idea (in my mind, anyway) is contingent on being able to build it with a geared hub. And since the Schlumpf hub wasn’t designed for the stresses that a motorcycle wheel would generate, my guess is that this idea is very likely currently relegated to the realm of dreamland.
I do not see why the idea of using a motorcycle wheel for a unicycle would not work, however I think the idea of a schlumpf hub may create a significant engineering challenge. I do personally believe the internals of a schlumpf hub would be strong enough for this, but am unsure as to how you would be able to attach a schlumpf hub whilst being able to make sure it can withstand the massive amount of forces that a larger motorbike wheel would exert onto it. You have to remember that there is already a lot of force going through a standard unicycle wheel, particulary when climbing or descending a hill, and a heavy motorcycle wheel will just increase those forces. I think you would likely have to come up with some other way of making it geared, but again this is likely to be a massive challenge and would likely become very costly very quickly.
@Uni_Jack I agree that an internally geared hub is not likely to be strong enough for a wheel of that weight. While no gearing method would be easy, it seems like the most viable approach would be some variation of the Huni-Rex type of set-up, with sprockets and chains on both sides of the wheel.
You could easily build a wheel at motorcycle dimensions using bike parts these days. Like, here’s the Surly Clown Royal rim, 24x100mm, designed for a 6.2" tire.
What would the interest of using that kind of tire be ?
It would be heavy → hard to turn and accelerate
It might help turning at high angles, but I’ve never fallen or seen somebody fall because of tire slippage (except in freestyle or muni obviously) → a good road tire is probably enough to take highly banked turns
It would cost a lot and need custom made parts → money is expensive
I’m sure @toutestbon has some good story about falling because of tire slippage in 2018
For his defense, if I remember correctly, the road was wet and he tried to ride around a roundabout at full speed, trying to match the then 10k/marathon/100k/XC/cyclocross World Champion’s speed.
I’m still traumatized. It was my worst injury on a unicycle, a complete tear of the posterior cruciate ligament. For three months, I couldn’t ride my unicycle.
Since then, I’ve mostly given up on turns to focus on straightaways…
Over the past few months, I’ve been thinking a lot about turns; I’ve tried to take a step back and start from scratch, and I’ve had some interesting discussions with other athletes.
For a long time, I’ve had this image of motorcyclists leaning so low they’re almost touching the ground. But it’s not the tire that allows you to lean while maintaining traction, it’s the motorcycle’s counterweight.
I’m now convinced that it’s better to compare it to skiing and cycling. You have to lean your skis or bike, but keep as much of your weight as possible on the outside of the turn. On a unicycle, your movements are much more limited because you’re almost always sitting on the seat. Even so, you can still optimize how you take turns through practice.
Yes, a decent road tire (and virtually any tire at all) is good enough to take highly banked turns, but good enough isn’t what I’m seeking with a motorcycle-wheel unicycle.
One of my favorite things to do on a unicycle is aggressive and highly banked turns, such as this one:
A steel-rim Coker wheel stores a lot more energy than an aluminum-rim wheel, and although I can bank both of them quite significantly, my steel-rim Coker has a far greater fly-wheel effect, which affords me increased stability and carries me through longer, more sweeping turns. With this in mind, I started thinking that given the profile and weight of a sport bike motorcycle tire, the kind of turns I might be able to perform on a geared unicycle with a motorcycle tire would either be quite lame (because the feel of riding a unicycle with a tire of that profile is very strange and hard to get used to), or potentially a lot of fun! And while it would be harder to accelerate, that’s fine with me. Assuming I could ride it ok and it doesn’t feel quite awkward, I am fairly confident that turns wouldn’t be a problem with the right technique. For now, I’m busy with several other projects I am working on, so this isn’t something I would be able to immediately pursue, in any case. But a man can dream!
@tholub That’s super cool! There’s no run-up, so I’d never be able to get enough speed on my 36er to ride something like that, but I sure did have a lot of fun when I went to Ray’s MTB park 20+ years ago and rode this:
Another thinking avenue on the uni-with-a-motorcycle-wheel (would rather ride such uni than the car-wheel one) could be to supplement the axle with an electric motor (pedelec style). Corbin did such electric-assisted uni (his website is Corbin Treehouse) and as usual with bike parts, you are golden if you can find a mid-frame motor that won’t freewheel…
Man, I love these kind of mad-scientist ideas, but honestly? The weight is going to be your absolute worst enemy here, way before the hub even gets a chance to snap.
Have you ever tried to track straight or correct a wobble on a heavy wheel? The rotational inertia on a motorcycle tire is massive. On a motorbike, you have a motor and a rigid chassis to stabilize that weight. On a unicycle, you are the motor and the stabilizer. Every tiny micro-correction you make to stay balanced is going to feel like trying to twist a moving gyroscope. Your ankles and knees would be absolutely thrashed after ten minutes.
If you really want that aggressive cornering profile without the crushing weight, maybe look into wide downhill fat-bike tires or even some of the beefier moped/e-bike tires first. They’ll give you a bit of that rounded edge to lean into without requiring a literal machine shop and a prayer to keep a Schlumpf hub from exploding.
@Guayou Thanks! The weight is what makes the idea interesting! For this type of unicycle what you want to do is find a nice, smooth, clear lane that leads into an area with numerous obstacles. The goal is to get up to speed on that clear lane, and then attempt to maneuver as necessary to avoid crashing into any of the obstacles. Once the motorcycle-wheel unicycle rider enters the obstacle area, he or she must stay mounted on his or her ride for 8 seconds, or get beyond the finish line, in order to receive a score from the judges.
