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Build Your Own Self-Balancing Unicycle
CaptainKaos[DOH!] writes "Robot hacker Trevor Blackwell is at it again, this time with a self-balancing Eunicycle. Blackwell writes, 'Some time ago I built a self-balancing two-wheeled scooter. Since then I realized that two wheels are redundant, and only a single wheel is needed to make a ridable vehicle. A vehicle with a single wheel is much smaller and lighter. It weighs under 30 lbs and is easily carried with one hand when going up stairs or on public transportation.' Trevor's previous 'Segway' type two-wheeler was mentioned on Slashdot."
A self-balancing power unicycle.
So THAT's what the maintenance crew / army was riding (on the under-road access paths) in Heinlein's _The Roads Must Roll_.
Maybe RH can stop spinning in his grave now that tech is catching up to his earliest stories.
Good work, Trevor!
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
Trevor mentions that you control speed by leaning forward/backward and steer by twisting your body. This is appropriate for low speeds.
But as with a bicycle or motor cycle, at higher speeds you can steer by leaning. For instance:
- Lean right.
- Force on the axle is translated to motion 90 degrees offset in the wheel's direction of rotation, causing the wheel to gradually precess to the right, gradually turning the vehicle.
Twisting continues to work but differently - in reverse and one stage of integration removed:
- Gently push forward on the right handlebar, as if turning left. (There should be a body-twisting motion to produce an equivalent on the unicycle.)
- Force on the axle is translated to motion 90 degrees offset in the wheel's direction of rotation, causing the wheel to gradually precess to lean progressively more to the right. (Stop pushing the handlebars when you're tilted as much as you want.)
- Tilting the wheel moves the center of gravity to the right, causing the vehicle and rider's weight to apply a force on the axle, as with the "lean right" case above.
- When you've turned far enough, gently push forward on the LEFT handlebar (or do the opposite body-twist) to undo the lean.
This only works at moderate-to-high speeds, when the gyroscopic effect is adequate. And it works at much lower speeds on a motorcycle than a bicycle due to the greater gyroscopic effect from the heavy wheels. (It's hard to get a bike going fast enough to do this.)
Try it out on a motorcycle: Find a nice flat, straight, country road with good pavement and no traffic. Get moving maybe 25 MPH, and balanced well enough that you can open your hand around the handgrip and steer by leaning. Once you've got that working, try just barely touching the back of one handle to push it forward.
Once you get the hang of it you can use it to perform extremely abrupt turns on the 'cycle. A stiff push causes the cycle to suddenly drop into a steep bank and begin a tight turn. A stiff push the other way pops it back upright and traveling straight. The banking is just right to keep you stuck to your seat and turning at a constant rate while applying no twisting force to the handlebars. Very relaxed while performing extreme manouvers, since the only muscular effort is used when you CHANGE your RATE OF TURN. (But don't overdoit and break traction or you'll go down.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
THANK YOU! I wish I had mod points at the moment to mod you up!!!
I've seen so many posts along the lines of "why bother?", "what good is it?", and "what a waste of time" that I was beginning to wonder if any geeks were still hanging out on Slashdot.
No, it isn't marketable. No, it won't revolutionize transportation. No, it sin't even particularly practical.
But it is quite an accomplishment! What a COOL thing to do! Like so many real geeks he did it because he could.
Until I hit your post I had begun to feel in a very small minority of people that understand why you do something like this. Then again, I've always loved doing the impractical just to see if I could...
Life is short: void the warranty.
With a fair amount of practice, it's possible to ride a normal unicycle without a lot of arm flailing, so it's fair to say that the same is true for this contraption.
Just like a bike, a smoothly driven uni wheel gives you lateral stability at speed (due to gyroscopic force). It's forward and back balance that keeps your arms doing funny dances at the beginning... eventually, you build core muscle memory and do it with less arm movement. The arms end up moving more or less the same way as when you are walking... in counterstep with your leg movements.
In the unicycling world there is a contraption known as a "BC Wheel" (sometimes called "The Impossible Wheel"). It got its name from the famed BC comic mode of transportation. Basically its a wheel with pegs or platforms that stick out from a freewheeling axle. The idea is that you roll it, jump on, and try to maintain balance.
While it may look "impossible" to people who have never learned how to ride it , BC wheels are actually quite ridable with a few weeks of practice and many in the Unicycling underground (yes this is for real! - check out this video) can do all sorts of tricks on it like jumping from wheel to wheel and riding it on trails.
Segway uses a gyroscope to do just that, and I guess this unicycle thingie does the same.
you might ask how a gyroscope helps, but think why you can balance a boiled egg on its tip by spinning it quickly round the long axis.
gyro works the same way, only the axis does not have to be vertical, it can also be horizontal, and there can be more than one gyroscopes, so you "lock" certain axises, and get the balance you need.
Omry.