Newcommer. Questions on fast unicycles

Hi everybody. I’m a disegner of fast bikes (for speed records) and this is one of my recent ideas (modyfied centaur (it had two wheels before)). It has drive from hands and legs. Very beta drawing, just idea.

I wold love to hear from unicycle experts :

  1. would it be ridable?
  2. are there hubs with integrated planetary gear for unicycles?
  3. would it be possible to turn?

I like this bike bacause it’s simple and has good aerodynamics => high speed.

Nice idea!

How does the hand pedalling work?


you’d need very strong arms…

This is centaur (combi drive)

centaur in action:

In unicycle case hands drive do the same, but connected diractly (via) chain to legs drive.


oh now i get it. before i thought that you were pedalling with only your hands :sunglasses: That would be very fun to ride if you could make it

i think it would be more efficient to just to use your legs only or your hands only. you will would have to have your legs spinning at the same rpm as your hands.

> Hi everybody. I’m a disegner of fast bikes (for speed records) and
> this is one of my recent ideas (modyfied centaur (it had two
> wheels before)). It has drive from hands and legs. Very beta
> drawing, just idea.

Sounds cool - very cool.

> I wold love to hear from unicycle experts :

I’m nowhere near an expert, but I’m going to stick my oar in anyway :slight_smile:

> 1. would it be ridable?

One thing I’ve learnt on these forums is that almost anything is ridable :slight_smile: No matter how crazy an invention, there’s always going to be someone who can handle it.

I bet many people would be able to ride it sitting upright and not using the hand cranks. Transferring to hand cranking too would be interesting - you’d have to be going slow enough that you could grab hold of the cranks.

Riding this would require decent balance - you wouldn’t be able to flail your arms around :wink: I don’t know how much hand cranking would disrupt one’s balance…

What wheelsize were you thinking of? 36" wheels seem to be popular for speed / distance riding, although geared 29ers have some merits too.

Oh, and a little safety point: it’d be really nice if you could fall off the front of this without getting your feet tangled in any machinery :wink: Although given you’re unlikely to be able to run out of a speed record attempt maybe that’s not so important!

> 2. are there hubs with integrated planetary gear for unicycles?

Yes, see and search the forum history for Harper’s Blueshift and uni.5.

The Schlumpf hub is shiftable on the fly, Harper’s hubs offer a choice of two ratios you can change with a toolkit (by adjusting the torque arm if I remember correctly - which I may not do).

Also, look for PurplePhaze which achieves much higher ratios using a jackshaft system. Again adjustable using a toolkit, but a bit more work. It also featured a “tuck” handlebar arrangement, vaguely like your proposal (without the hand drive). OuttaPhaze is a proposed production variant of this design.

> 3. would it be possible to turn?

If it could be ridden, then it could be turned.

> I like this bike bacause it’s simple and has good aerodynamics =>
> high speed.

The deisgn illustrated would have no advantages for speed at all.

On a bicycle, if you can increase the power input, you can ride a higher gear at a given cadence, and therefore go faster.

Power is not the issue on a unicycle. Turning a 20 - 36 inch wheel is not difficult and does not require a lot of torque at all. The problem is simply one of coordination. How fast can you spin the wheel whilst maintaining control? You can improve this by selecting an appropriate length of cranks (short cranks = potentially faster, but at the expense of some control) and by practising!

As I understand your diagram, the hands and feet are each contributing driving force to the wheel, and are connected by a chain. I assume a 1:1 ratio between hands and feet. Anything other than that would be very difficult to co-ordinate, allthough I guess 2:1 would not be impossible.

So you are increasing the torque available, but not the rpm. In fact, because of the additional co-ordination problem of having hands as well as feet pumping away, you are probably losing rpm.

So you need to gear up the hub. Lots of people have experimented with geared hubs. It is possible to gear up the rotation of the wheel to about 1.6 or 1.7 (approx.) times the rotation of the cranks. Even that is the equivalent of a very low gear on a bicycle.

At best you have a very pretty picture of something that would be more difficult to ride, and much harder to steer than a conventiojnal unicycle; which would if anything be slower on the flat, and a fair bit more dangerous. The only advantage I can see - and that a theoretical one only - is that it might be good for hillclimbing, on smooth straight steep hills.

Thanks for link and replys
At least 1:3 gear needed.
Ok. I see. This is cool but probably not for speed record.

Cool drawing.

  1. would it be ridable?
    Yes, nearly anything’s ridable.

  2. are there hubs with integrated planetary gear for unicycles?
    Yes, but might not work with a chain drive.

  3. would it be possible to turn?
    I assume you mean steer, yes also.

3 1/2. Do good aerodynamics make a fast unicycle?
No. They (generally) don’t go fast enough for distorting your body position to be better than an ergo position that lets you balance, breathe and pedal faster.

You don’t want to pedal with hands and feet at the same time. When pedaling with fee, we use one hand to stay steady on the cycle, and the other to help in balancing. You can get by with no balancing hands, which we generally do in road racing, but on the track things happen fast, and a free hand can be very useful.

The fastest unicycles currently are 36" wheels, and geared-up 29" wheels. Someday maybe geared-up 36" wheels. Read up on those to learn more about what a fast unicycle currently is, then work from there.

For existing unicycles, this is certainly the case, but if we really start to push the limits of technology, it may not be the case forever. If someone wanted to start doing Bonneville Salt Flats-style speed records on a unicycle, he could develop something like this with a gear of something like 80 or 90 gear-inches, which would go fast enough to get benefit from an aerodynamic position. Once you get above 20 mph, aero drag starts to take over as your major limiting speed factor.

A challenge would be that you’d have to find someone who was not only a strong rider, but also willing to pilot an unstable one-wheeled contraption at speeds above 20 mph. Not to mention, an unstable one-wheeled contraption with a row of sharp teeth aimed at your neck.

I wouldn’t expect the hand-crank to be worth the extra complexity, but you could construct something with a seat and bars which put you in a more aerodynamic position than is normal on a unicycle.

Not a challenge at all. just browse our galleries and take your pick of the freestyle/street teenagers :smiley:

I really hope you make this thing. . . I agree that a 1 to one ratio would be pretty important for balance issues. would we be able to keep that 1-1 while shifting?

I also think the best advice i can offer you is: go get a unicycle!!! learn how to ride it (we’ll all help as much as we can) and then uuse what you learn to help you build this marvel!!! you can get a nice starter unicycle (Torker LX) for under a hundred bucks.

I think aerodynamics does start making a difference at something like 15mph or so. Given there are quite a few people who can hit 20mph without problems, they’d probably get benefits from better aerodynamics.

The position looks very cramped, maybe moving the handle higher would be nicer. alternatively if you’re bothering making a chain drive from the handle to the wheels, why not have the pedals on a chain drive too, that way you could lie the person right down, making for a very aero position. It’d be jolly hard to ride an upside down recumbent unicycle but I’d guess there are people who could. If you had guards so you didn’t hit your hands on crashing and kept the rider as low down as possible it could be much more rideable, as you might be able to launch from the lying down position.

Like Mike says, plantetary gears are a bit limited in how high they go, although on the 36" wheel with the 1.55x gearing, it is equivalent to quite a decent sized bike gearing.


I was looking at the riding position… I think it might be harder to shift your weight forward and backwards with your body so horizontal. I agree that the rider would be better off sitting more vertical

I we look at bicycles (and tricycles) where fore and aft stability is not a significant issue:

The Tour de France involves high speed riding uphill and down hill for long distances. If there were any advantage for hand/foot combined power in this type of riding, someone somewhere would have made the point, even if the rules had not allowed them to enter the race.

Ditto for track racing and time trials and so on.

Bicycles weren’t always the shape we see and accept now. They have evolved this way for a number of valid reasons.

The exception is straight line maximum speed, where HPV enthusiasts often go for a recumbent position, with the rider bracing his back against the back of the seat, and pushing extra hard against the pedals and turning a very high gear.

I have ridden purely hand-cranked vehicles. It’s hard work.

I doubt that in any but the most carefully selected circumstances, the additional weight and complexity of the hands/feet drive and the additional co-ordination problems that come with it, would be anything but a disadvantage.

Add to that the further problem of balancing on one wheel…

This is no more than an interesting idea, which is right up there with kangaroo unicycles, geared-up giraffes, and the like, as fun to try, but inherently less effective and efficient than a conventional (or geared) uni.

probably, some gyrostabilizer could be used.

To create gear such schema could be used: chain goes flom legs drive to hands drive and than from hands drive to wheel. Standart bicycle components could be used.

I would say that hands drive can give some advantage if it is well dome and you have enough muscules. I was riding centaur for half a year and I can tell I like it. And I want to build something that uses my hands power.

and yet someone, somewhere, said “I got an idea!!! how about if we only use ONE wheel!!!”

I think it’s a really neat idea, but like he said, it’s preliminary.

I say build it, try and ride it, and when (if) that fails, find someone else to ride it.

It may work real well, it may not, and it may just be another unique (and sexy) unicycle design.

Nice concept :sunglasses:

My thoughts:

  • The current limiting factor for unicycles going fast is how fast you can pedal, not how much power you can exert. Even with 1:1.55 epicyclic gear ( available now, it’s still a relatively low gear. Hence having an extra power transmission via your arms will not help increase speed until the gear ratio get much bigger. Frantically working your arms on a unicycle only destabilises it and slows you down.

  • The low, stretched out position you have there is good for going fast. When I’m riding fast (~30km/hr), my body position is really low (in fact from photos I’ve seen I have my back at about 30 degrees to the ground.) The reason is that this lowers your centre of gravity and and makes you more stable.

  • Aerodynamics certainly play a part once you go above 25km/hr, and most good riders can ride above 30km/hr for short periods. I think the fastest speed I’ve heard of was Christian Hoverath clocking 48km/hr downhill on a 36" Coker.

I’d love to ride one though- it looks so cool :stuck_out_tongue: