So, there are many issues with this, but I absolutely love the amount of effort that has gone into the design and animation and I really really want to see someone build a hubless unicycle.
I mean I’d love to be proven wrong, but I only see new problems and no benefits over a conventional wheel with a hub and spokes…
Aside from it just being the coolest looking thing you’ve ever seen?
My thoughts on a hubless unicycle were to go with a giraffe, and then the tried and tested methods that everyone has been using for DIY hubless bicycles.
Sorting the gearing would be tricky, but you could maybe make it 1:1 with two chains (one around the wheel sprocket to a driving sprocket and one from there up to the pedals), being geared up loads initially, then geared down again going around the wheel.
Putting the cranks on the wheel itself slightly detracts from the aesthetics as far as I’m concerned, and it makes actually supporting the wheel much more difficult, but it does stop the gearing being an issue.
Clearly a giraffe is no good for trials unicycling, but in my mind neither is a hubless wheel…
So I’m not sure how the wheel is attached to the frame? I would like to read a description of mechanics of The unicycle. The cartoon implies it is a trials unicycle of muni , would this type of connection. Handle drops? Hopping and other rough riding. As far as pedals they look fixed with no way of changing “crank” length or pedal poposition.
I’m also not sure how they plan to solve the frame-rim problem, but typically it involves a selection of bearings at various angles.
Often the DIY hubless bicycles make a whole new steel ring that supports the rim and tyre, but doing it that way is incompatible with having the cranks attached to the rim.
You could have cranks with more holes I guess, but the further into the centre of the wheel you go, the more the cranks will want to rip themselves off the rim.
I think there are some unsolvable problems in making a useable hubless unicycle that’s anything other than a rideable art piece, but the design and engineering challenges they’re going to have to go through may end up leading to advancements somewhere else in unicycling.
There are only a couple of reasons that I can see for developing a hubless unicycle. Either to reduce the q factor or to reposition the pedal axis for a lower center of gravity. What’s depicted here doesn’t seem to do either one.
I’d also have to assume that this would result in both a heavier and a weaker wheel.
I’d maybe think that about a physical product, even if it still has a lot of problems or is executed poorly. A rendering (no matter how well done it is) - I just can’t get excited about that…
What about a real product?
You’re in luck as apparently they’ve made at least one.
This does clear up a few things about how they’re going about it, and solves a few issues
Edit: Apparently I’m too slow at typing this morning.
Now that is something that does look cool. Rather pointless except being a show piece still, but very cool.
So based on the images, there’s a steel ring on either side of the (presumably all CNC) rim, either connecting to a load of bearings, or forming some kind of bearing on each side. This is how bikes tend to do it.
The frame looks to be CNC solid aluminium.
Based on some quick maths (from the diameter of a 19" rim, the (theoretical) cranks are 135-140mm or so.
I imagine that the wheel probably weighs as much as a whole unicycle right now, and is perhaps 50-70% of the strength (depending on how solid they’ve made it), but I might be a bit out…
The issue with having a ring on either side of the wheel that is completely independent of one another (they have to be to allow the crank connection to be made) is that there’s nothing much resisting any twisting forces. When hubless wheels are done on a bike, the two rings are typically connected together all of the way around the wheel which stiffens things up substantially.
You’ve basically got two sides of a triangle in the frame, and then the bottom of the triangle has a big gap in it.
I think that’s probably my biggest concern about it ever being a functional trials unicycle now, with the actual strength of the rim being secondary. When you do a sidehop, you put insane twisting forces through the wheel which this setup can do little to resist.
It still looks awesome though!
Looks cool but the way the pedals are mounted it will be like having seriously long cranks especially as the wheel sizes increase.
I think this is so inovative that we all that we all need to sit back and see how this shakes out. Obviously the designer and builder have put some serious thought into this and all of the issues we are picking out at a glance they surely have thought of and wrestled with. I look forward to seeing more of what was posted on face book, (actual pictures). Best of luck to all involved in this project.
There’s no reason this couldn’t have spokes, or crossbraces as both a stiffening mechanism and a location for pedal mounts.
I think the whole goal of this was to make a unicycle that had an entirely open wheel centre, so that’s probably a no-go.
(If that wasn’t the goal then I’m stumped)
I’m sure they have, but there are a lot of technical minds about, and “Ye cannae change the laws of physics”
It’s also not so much picking things out at a glance. There are only so many ways you can physically go about doing what they’re doing, so even if we don’t know all of the details of what they’re doing we can still discuss it.
So back to discussion of hubless wheels.
Ignoring all of the durability and strength points for a moment, for free movement of such a hubless wheel, the rim and bearing surfaces (however they’re specifically doing that) need to be perfectly true, and need to stay that way for the wheel to rotate freely.
To an extent you can reduce the tolerances between the two bearing surfaces (the wheel rim, and the frame connection/frame “rim”) to make this less critical, but in doing so you further reduce the stiffness and increase the likelihood of damage.
If the wheel becomes even slightly out of true (either up and down or side to side), it’d almost certainly have to be replaced. There’s no easy way to true up a wheel that has no spokes.
What we have right now to discuss is an animated cartoon and a few facebook pictures. What I’m saying is that is not enough information for anyone on this forum to speculate their concept, process or out come no matter how technically advanced one might consider themselves. For all we know all of theses concerns have been worked through or maybe not, this we cannot know. Discuss all you want but I think it is only fair that the designers and builders have a chance to unvale their product and demonstrate it I’m sure at that point they will be able to answer all of these concerns as well as listening to feedback It seems to me that this time may be close since there is stuff popping up on social media.
Looking at their animation however, it’s obvious they have an intention of marketing it towards trials riding, in which case it’s going to need a strong wheel and the easiest way to get that would be some sort of cross braces. They don’t need to look like traditional spokes. A honeycomb or something else would work too, but it would also give a solid mounting point for the pedals that isn’t right next to the rim.
Speculating is just that, speculating. However I’m mostly commenting on things I can see from their pictures (if talking about their prototype), or potential options for just creating a hubless unicycle.
I also understand that their product is not a final unit and things likely will change, but there’s nothing wrong with discussing the fundamentals of the idea and the concept of hubless unicycles as a whole.
I hope nobody stops them from unveiling and demonstrating their product. Even if they only released a commercial product that can be ridden (no hops, jumps or drops) then I’d still be seriously considering buying one for the novelty of it.
My prediction is that they’ll make a wheel that’s strong enough (albeit a heavy one) for light-medium trials without any bracing, but the attachment of this hubless wheel to the frame is where they’ll struggle the most due to side loading.
Hubless is also bit of a misnomer for most of these cycles as they tend to have a hub, just a huge hollow one. If you add some kind of bracing then I definitely think it’s strayed into just a cycle with a huge hub and it loses the aesthetic appeal.
I also initially thought that the crank length would be a big issue, but for a 19" wheel when you calculate it, their pedals seem right next to the rim, but actually a theoretical 135-140mm. An extra 10-15mm on each side doesn’t seem like it would be a big deal either, and would get you down to about the shortest length that people seem to ride for trials right now.