Get thyself to the nearest well stocked magazine stand and look for the
latest Popular Science, page 13. It's just a conceptual mockup, not a
working model. I can see it working OK in a straight line, but I really
have my doubts about how well something like this would corner, let
alone handle an emergency stop...
Unicycles handle all (non-falling-over) movement by moving the center of
gravity of the machine in relation to the contact patch.
If you want to accellerate backwards (slow down) you accellerate
so that the center of gravity is behind the wheel, so that the rider is
Now slow down in order to keep the rider at the same angle until it's
Cornering works similarly.
Not a very practical machine, as adhesion is an even worse problem
than on bikes.
For example on the emergency stop, on a bike if you have an adhesion problem,
at worse you'll break a wheel loose, which can be fixed by an alert rider.
On the unicycle, once you put the center of gravity back, you are committed
to continuing to provide that amount of decelleration.
If you can't, the rider moves further back, and you need even more
If you don't get this, you'd better be wearing a helmet with wheels.
Done it. Twice. Not easy to ride. The hardest things are slowing down
(and the need to be able to have some braking effect to keep the wheel
under you) and not overrunning your engine (overrun it, lean formard a
little, and you can't get the wheel back under you)
I did it, both times, with chainsaw motors, centrifical clutch still
in place. Tended to break free when I let off the gas, and at slow
speed, no motor braking. Did a crummy job on construction at the time
(prototypes) and my total ride time between the two is probably about
1 or 2 minutes. Both broke.
The positioners needed for holding balance while stationary are quite
If you eliminate that need, and go with only able to reposition in the
air, it gets a lot easier to build.
Then again, I was thinking of a more direct system, with electronic
valve control of a propane/butane mixture added into a cylinder, and the
piston acting directly on the foot.
Somebody actually *did* that.
A fuel-powered pogo stick.
I'm sure there's a reference somewhere.
please reply to:
JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com
A Russian researcher (university level iirc) built a pair of these and made
mega speed running stilts, also gas powered. Elevated him about 18 inches.
Each step compressed the mixture in the cylinder and the explosion was timed
to happen past top dead center.
Must have been a rush. Could maybe find the article if anyone wants the
One of the members of the CAMS club brought one to a meeting. I
forget whether he told it there, or I read it here, but someone tried
building one with a jug from a VW, and it launched him onto the roof of
his garage the first time he tried it. :-)
The motto -- go for a small version.
They used to use those for compacting road-bed. Imagine a jackhammer,
with no air hose, & a hand-tripped magneto to fire it. You trip the
mag, the thing jumps up, compressing a new charge as it sets down
again. Worked from gasoline.
The modern ones just have a regular gas-powered engine, driving an
eccentric weight to vibrate it. Wimps :)
jim rozen wrote:
:>Then again, I was thinking of a more direct system, with electronic
:>valve control of a propane/butane mixture added into a cylinder, and the
:>piston acting directly on the foot.
:Somebody actually *did* that.
:A fuel-powered pogo stick.
:I'm sure there's a reference somewhere.