Any advice from the experts?
I think this one would be great for the disk.
It’s says rockwell, so probably it’s great for idling, but I guess one footed.
Since UW’s tend to stop much more effectively than they “go” I would say that every UW is a disc brake.
In my experience the tire is a great disc and the soft tissue of your calf makes for a very effective caliper/pad combo…
lol
I was thinking more along the lines of a geared hub for a UW. Perfect that then add a disk brake.
Genius.
In fact, if the geared hub had a reverse option that you could select on the fly, maybe you could manage without the brake at all.
I don’t see the point unless your planning some sorta UW to BC wheel activation.
In theory this is possible, but it will not happen unless a fanatic makes it so. Then, learning to stay on while operating the disc brake will be an extreme feat.
Seems like it wouldn’t be that different from gliding, not that that’s very easy.
The thread is a joke. Neither a brake or a geared hub is plausible on a unicycle.
Both require another part to oppose the reaction forces. On a normal uni this the frame and the rider. There is nothing other than the wheel in the ultimate wheel.
I know that was a typo, but it captures perfectly the type of response I get from Joe Public when such matters arise in conversation 
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Oh yee of little faith.
I don’t think any have been built beyond the lego model stage but there are a couple designs that could work. One such design is based on the Dacoroman design. I have drawings somewhere of an UW that would be geared against an internal pendulum weight as well.
Rob Northkott built a lego model based on Dacoroman’s concept:
Dakoroman lives again! 
Would that geared crank arm system work on a standard unicycle?
Just as well as it would work on an UW.
I can’t see any reason why a disc brake couldn’t be made to work on a BC wheel - a geared hub might be more tricky.
Very creative but not workable. A reaction torque equal to the crank torque is applied to the pedal. This problem is evident in the second half of the video.
This would require a very large counterweight to climb even a small gradient without overrunning the pendulum. I doubt that any rider would be able to stay mounted once that happened.
It’s more fun to think of potential solutions than state things are impossible. A torsion bar through a hollow axle connecting the two cranks would help dakoroman’s design as far as usability but there are still multiple problems, like having all that weight flopping around.
The pendulum wouldn’t need to be that heavy. We are talking about an Ultimate Wheel, I can’t ride one but if I did I don’t imagine I would be putting massive acceleration forces into it.
If it was geared like a schlumpf (1.5:1) 1/3 of the force would go into the pendulum and 2/3 into the wheel.
Let’s say you can generate 30ft*lbs of torque (60 lbs more weight on the front pedal than the back with 150mm cranks) 10lb + 1/2 the weight of the rest of the wheel on a 1 foot arm would be sufficient to counteract the force.
If anyone builds one I would nominate them for an Ig Nobel Prize.
We are talking about Ultimate wheels here, not practical transportation.
“It always seems impossible until it’s done.” – Nelson Mandela
“To believe a thing impossible is to make it so.” – French Proverb
“Never tell a young person that anything cannot be done. God may have been waiting centuries for someone ignorant enough of the impossible to do that very thing.” – G. M. Trevelyan
“So many of our dreams at first seem impossible, then they seem improbable, and then, when we summon the will, they soon become inevitable.” – Christopher Reeve
“Sometimes I’ve believed as many as six impossible things before breakfast.” – Lewis Carroll
“It is either easy or impossible.” – Salvador Dali
“To the timid and hesitating everything is impossible because it seems so.” – Sir Walter Scott
“We have more power than will; and it is often by way of excuse to ourselves that we fancy things are impossible.” – Francois Duc De la Rochefoucauld
“Everything is theoretically impossible, until it is done.” – Robert A. Heinlein