Haven’t been very active here for some time, but today I found a video I wanted to share with you. My hope is that it will generate some interesting discussions regarding geared unicycles.
First the video:
It shows Lunartic, a prototype for a hubless bicycle. To me it looks like you could just remove the front part, and you would have a hubless geared unicycle. Does anyone know if anyone has built a unicycle like this?
Obviously there are many problems with this design (weight, durability, a lot of custom parts etc.) but I still think it’s interesting and it would be fun to try to ride one. For now the prototype only has one gear it seems, but adding more gears shouldn’t be too hard (compared to a geared hub, for example).
Not sure how that concept would work for a unicycle, since you wouldn’t have the cranks in the center, for even distribution of pedal force, as you do with a hub. Not a problem, it seems, for a bike, which has the front wheel and frame, keeping the crank position similar to that of a bicycle with a traditional rear wheel/hub.
Giraffe unicycles do not have the cranks in the center of the wheel, so I am not sure I see why that would hinder the use of a hubless unicycle. I am sure hansc did not mean simply removing the front wheel and leaving the rest of the frame as shown.
I think it looks cool, but also a bit silly considering how the video mentions the advantages of big wheels and then shows off a bicycle with what looks like a 16" front wheel…
This particular design is not a fixed gear (it can freewheel), so it wouldn’t plausibly work as a unicycle. You could build something similar with a fixed gear, which would make it functionally similar to a jackshaft design, though it would be hard to imagine what the benefit would be of this design over another jackshaft.
I suppose you could theoretically have the drive hub contain some sort of shiftable fixed planetary gearing system, and it would be easier to run a shift cable down to it.
If I have worked out the way the outside rim is supported, then there will be friction on the sides and any friction loss on a bike is not good. The low losses in a bike are one of it’s defining and essential attributes.
With some more complexity it could be improved - say by having two sets of opposing inward inclined roller bearings, each set alternating with the other and opposing it’s paired mate.
But even then, a couple of dozen roller bearings will generate friction at their axles. And they would require a lot of cleaning.
Yes, clever, but not clever enough to make up for serious deficiencies. I think it would be limited to being ridden in public spaces for “cool” but with no pretensions to actually doing much actual distance.
However, with a uni it could be argued that frictional resistances are not necessarily a negative. So on uni maybe it can make sense.
There are 2 benefits here that I think have been largely overlooked.
it can be easily geared - even multi-geared. (this has been mentioned)
It could solve the unicycle suspension problem. Picture the pedals in the center of the wheel, and the drive mechanism at the front or back of the wheel. The pedal mount could be made to pivot at the drive mechanism, and be spring loaded. Finally a way to suspend more than just the seat!
The biggest problem I see is protecting that big gear from debris.
If it were me it wouldn’t have two wheels to begin with.
That’s an interesting point I also thought about. Then I remembered the recumbent unicycle. On a hubless unicycle the saddle could be shifted to the back to compensate for the cranks not being in the center - maybe it could even give a more bike-like position some people seek. Another interesting thing is how off-center cranks would affect the wobbliness.
Yes there was an independent discussion of how offsetting the cranks at least a little bit forward would probably significantly improve riding comfort; however, like so many of these ideas, material science has yet to make the engineering dreams as practical as one might think. Still as unicycles aren’t about pure practicality I think a jackshaft forward offset unicycle design would be worth it for some distance riders.
The bike is cool, and looks like a great subject for the design project it was made for. There was not a clear description of a problem that was solved by the design. A bigger wheel with less weight? It doesn’t look like it. Shorter wheelbase while still having a big wheel for most of the rider’s weight? Yes, but to what purpose, other than fitting it in the car/apartment/bus?
I think part of their point was to get a short wheelbase, but yes, the small front wheel kind of compromises whatever advantage you get from the short wheelbase. It depends what problem(s) you are trying to solve.
And that’s without the suspension. Or, more to the point, I can’t see how the strength of today’s conventional unicycle wheels/frames can be matched in this design without significantly more weight.
I do like the suspension idea though, as an extension of the novelty of the design and a functional reason to work with it. “True” suspension on a unicycle would still be fun to experience, even if not practical for rough terrain use. It could be useful in a future where electric unicycles need suspension, or when it can be made light enough for geared road riding?
That would be an even better place to use a “full” suspension system. Hitting bumps on a recumbent is no fun, and would be worse on a recumbent unicycle. On a bike you can pause pedaling and lift your butt up while crossing the railroad tracks, for instance. This would be harder with a fixed gear.
Depending upon the size of the drive sprocket you could lower yourself by puting the pedals closer to the botom of the wheel. This probably would not be very good for Muni with pedal strikes of rocks but it could be cool for a commuting or touring unicycle.
Yes this is My thinking TOO and you can change the gearing TOO say if a flat couse gear it UP and a hilly race gear it down!
Also if you seat lower on Unicycle than there is less wind because of being lower and more speed! Of couse only for road riding and running a fixed gear