pretty simple really. as cool as I think it is that some of you crazy uniracers ride amongst bicycles, does it really have to be that way? yeah, you guys have two speed guni hubs to play with, but I know you can do better than that. hell, look at the nutter in the forums that is hacking up crusty old bike frames making sweet suspension frames. take a few ounces of that guy’s mad scientist juice and pour it into the drive train, and you could see die hard uni riders not only competing, but regularly wining bike comps.
yeah, if the drive train of road unis caught up to even 1960’s bicycles, you wouldn’t look as bad-ass as you crossed the finishline, but think of how sweet it would be to be the first across the tape on a uni?
anyhow, I’m blabbering on here. you engineering folk, can you tell me what the holdup is? last time I checked, wallmart cruisers had 3 speed hubs, why are $3000 uni’s still stuck with two? why the heck doesn’t someone build a road uni with a chain/sprocket driven drivetrain? I have a dirt simple concept for a derailleur based drivetrain that would fit a large rimmed uni, and I’m not an engineer. what gives, guys?
well that is 1 gear in the right direction out of curiosity, is the speed limit loosely enforced by current wheel size/gearing, or simply by the fact that ripping down a road at 60k on one wheel is dangerous? unable to ride my 20", I am already feeling the urge to pick up something with a bigger wheel so I can tear down the road like flash gordon, and derailleured gearing seems like an easy way of making that happen. geared hubs have always kind of sketched me out for some reason
on a different note, how sad is it that I, a canadian, can’t read your websites because they are in french, but if they were in latin or greek, I would be fine. sigh
I have a 2-speed 29er, and I have no desire to go any faster on one wheel (I’ve cracked the 20mph barrier a couple times). My fastest wipe-out was around 16mph (single-speed 36er).
There are two major engineering barriers to unicycle gearing; the location of the cranks, and the requirement that the system be direct-drive in both directions (no coasting). The cranks make it difficult to run a cable to the hub for shifting; Schlumpf solves this by making you shift with your feet, but that doesn’t work very well for two gears and would be worse for any more. The bi-directional direct drive eliminates virtually all gearing systems used on bikes today (except for Schlumpf).
And even with better gearing, unis wouldn’t beat bikes in any meaningful competition.
Gearing is no longer the main limiting factor in road speed.
High speed unicycling with standard, non-geared unicycles means using tiny cranks to enable cadences of 200rpm+.
Now, riding a 36" wheel with a Schlumpf hub (1:1.5 overdrive) means you could cruise at 20mph with a cadence of approx. 130 rpm. That cadence is possible to do even with full-length 170mm bike cranks, and is a fairly comfy cadence with 150mm or shorter cranks.
But…
It’s not easy to maintain 20mph, even on a geared 36" unicycle. Because it becomes pretty hard work on your legs to cycle anything at that speed, and a unicyclist is very un-aerodynamic.
We could reach 25mph on the flat before getting beyond what works well with current gearing (and that isn’t happening for anyone I’ve heard from). Bigger gearing won’t make higher unicycle speeds very much easier!
While reaching high speeds is a concern, that’s not really why we don’t have more gears.
The two gears we get from a Schlumpf are great, especially given the alternative of just one. But if the technology existed to give us more gears, many of us would be very excited… assuming it was reliable, not too heavy, affordable, and user friendly.
I’d love to be able to downshift to a super granny gear. My 24" is close, but still a few gears higher than the granny on my 24 speed mtb. And with the current Schlumpf, it’s quite a jump from 1:1 to 1:1.5. Having some options inbetween would be great.
at the moment, I am thinking of some pretty crazy stuff. like a drive shaft going up one leg of the frame driving a small gear near the top, with a locking derailleur mechanism feeding to a thin cassette. uneven weight distribution is an obvious downside, though I’m not sure how much of a problem that is on a unicycle. another is the narrower spoke profile, but i don’t think that would be a huge problem for a road uni.
my crazier idea is building a transmission that rests inside a hub. weight and complexity aside, I think it would be really damned cool. when I have a solid idea, I will sketch it out and let you guys tell me why it wouldn’t work. I just really like thinking of design ideas for things
@steveyo : I still can’t even ride my darn 20", so i really have no idea how a uni handles at high speeds. on clean tarmac, what sort of dangers does high speed bring? I would imagine the inability to brake fast could be a problem at times, but that doesn’t really bother me (I used to live in the country, and ride my 10 speed ditch bike that had no brakes down the rolling drumlin hills. a bit scary, but not crazy as long as you know that there isn’t anything that will get in your way :). does a uni exhibit speed wobble at high speeds? that is one thing that TERRIFIES me. I’ve only ever been in a speed wobble once, and that was flying down a hill on a skateboard at a good 40K. I thankfully bailed onto a looong stretch of grass, but the fear of speed wobble has haunted me to this day.
@redwelly: I didn’t know unis were capable of hitting 40kph right now. if that is the case, then you just rendered this entire thread pointless.
NEW QUESTION
why not make shifting cranks, so you could change crank length on the fly? that seems a lot more practical now that I think about it!
My top speed is pretty much limited to how fast I can run - if I fall I want to be able to run it out. Anything faster than that is scary, and I personally don’t want to take that kind of risks.
You will probably find this thread interesting: Fastest speed on a unicycle
Note that 3 in the top 10 are ungeared.
Changing crank length is not really the same as gears, as it would still be 1:1. I seem to remember hearing about cranks where the pedal position could be shifted on the fly, but unfortunately I don’t remember where anymore.
I know it would still be 1:1, but being able to adjust the torque on the fly would be pretty handy, wouldn’t it? anyhow, I don’t even know what I just looked at looking at those pdfs, lol. I was thinking a pretty simple cable pull system that pushes a cog out when the cable is pulled. the cranks would be sprung, so that when the cable is pulled, they will slide into the shorter position automatically. if you want a longer crank, pull the cable and push the pedals away from the hub. really pretty basic design in my eyes, and would fit on any frame with an isis hub. if I’m no explaining it well enough, I’ll draw a picture
Well, Dakoroman was a bit… special. I miss that guy.
Check this post in that thread to get an idea of how it would work.
Sure would! The one I’m thinking about shifted depending on your speed I think, i.e. faster = shorter cranks. Maybe it was just an idea, as said I don’t remember clearly anymore.
Tholub, I agree with you, my concept is of course with cable shifting; one under-gear, one direct-gear, one over-gear; distance between 2 gears is shorter than on Schlumpf because too large according to my opinion and I’m not interested by very high speed.
Last summer I had the opportunity to show a drawing to Kris, Roger and Nathan, they liked the idea. Since that, I did a lot of modifications, hope to realize a prototype one day, if possible with Florian support has he has a huge experience on such uni hubs.
I do want a little speed, but the main reason I’m interested in gearing is the same reason as on a bicycle - to be able to achieve and maintain a convenient speed at a comfortable cadence.
Yeah, I hear motorcycles are pretty safe…
Does it really need to be hard direct-drive in both directions? Has anybody tried a setup that drags instead of freewheeling?
I’ve tried such a thing. It’s like a unicycle as long as you’re accelerating, then it’s like and impossible wheel, only harder because the foot platform isn’t stationary.
out of curiosity, is the speed limit loosely enforced by current wheel size/gearing, or simply by the fact that ripping down a road at 60k on one wheel is dangerous? unable to ride my 20", I am already feeling the urge to pick up something with a bigger wheel so I can tear down the road like flash gordon, and derailleured gearing seems like an easy way of making that happen. geared hubs have always kind of sketched me out for some reason
