In the new Oct. issue of Popular Science is an article on a Segway like “Turbo-unicycle” . I will let one of you scan the picture so we can all see it. It is on page 13. It is a design concept at the moment but fun to look at.
Does someone out there get the Magazine and have a scanner?
The gyros may enable running stability, but “high-performance braking” is another story. How to counter all that torque? It has to go somewhere. The only thing I can think is into a flywheel, which is apparently not accounted for in the sketch.
The way a current uni brake is for the user to get behind the balance point. When he/she applies the brake, the tendency is for the user’s weight to lift up, so that there is work being done against gravity. This only works for small torques, not for the huge ones implied by the drawing.
Cool drawing though.
the thing can lean back just like we do to brake
But U-turn has a point. With only one wheel, there’s a limit to how much braking you can get. The weight of the vehicle plus rider, even when you lean it back until your butt is near the ground, will only give you so much stopping power. Not nearly enough to skid the wheel on dry pavement, for instance.
But the same is true on a Coker as well. Though you could fall backwards and lean on your brake, you are more likely to… turn! This would be a more likely avoidance maneuver, assuming you have someplace to go.
But alas, braking would definitley be a weak point on any motorized one-wheeled vehicle.
I suppose you’d have to bring down the “training wheels” for hard braking, and they’d have to have brakes in them as well. Or be in the back. Without having read the new article, the picture and information I read on the Web site that shows the Bombardier is clearly just an industrial design exercise. If they are taking it to the next step I’m very interested.
Re: Uni Segway in Popular Sci
I drew this “Moto-Uni” way back in high school in the late 70’s. I had no
understanding of unicycles then…
I was an obsessed Star Wars fan at the time, and this exists in either that
universe or one closely parallel to it. So we can rely on our trusty “inertial
compensators” or some such folderol to handle the high-speed braking issues.
Don’t ask me to explain that odd engine technology, either. It was drawn during
my “tubes and hoses” period.
Re: Uni Segway in Popular Sci
Oops, I just posted on the exact same. I copied the text of the article (it
wasn’t that long.) Next time I’ll have to check the newsgroup first before
writing a post.
I have the magazine and a scanner. I’ll post the picture tomorrow.
John Hooten
Zook wrote:
> In the new Oct. issue of Popular Science is an article on a Segway like
> “Turbo-unicycle” . I will let one of you scan the picture so we can
> all see it. It is on page 13. It is a design concept at the moment but
> fun to look at.
>
> Does someone out there get the Magazine and have a scanner?
>
> –
> Zook - 49er
> ------------------------------------------------------------------------
> Zook’s Profile: http://www.unicyclist.com/profile/3296
> View this thread: http://www.unicyclist.com/thread/27753
How would that be different from a motorcycle doing a stoppie? As the bike brakes, most (or all in a stoppie) of the weight transfers to the front wheel anyway.
Not that it would be easy to control it…
Tim
Re: Uni Segway in Popular Sci
In article <johnfoss.tve90@timelimit.unicyclist.com>,
johnfoss <johnfoss.tve90@timelimit.unicyclist.com> wrote:
)
)ubersquish wrote:
)> *the thing can lean back just like we do to brake *
)But U-turn has a point. With only one wheel, there’s a limit to how much
)braking you can get. The weight of the vehicle plus rider, even when you
)lean it back until your butt is near the ground, will only give you so
)much stopping power. Not nearly enough to skid the wheel on dry
)pavement, for instance.
)
)But the same is true on a Coker as well. Though you could fall backwards
)and lean on your brake, you are more likely to… turn! This would be a
)more likely avoidance maneuver, assuming you have someplace to go.
)
)But alas, braking would definitley be a weak point on any motorized
)one-wheeled vehicle.
Two notes:
Skidding the wheel reduces your braking power; you’re much better off
with the dynamic friction of your brake pads than with the dynamic
friction of the tire on the road.
At maximum braking power on a bicycle, almost 100% of the braking power
comes from the front wheel, because the limiting factor is not brake pad
friction, but the tendency to flip over the handlebars. This is one of
the reasons why it’s virtually impossible to skid a bike’s front wheel
on dry pavement by braking.
So, I think a one-wheeled vehicle, properly balanced, could brake just
about as well as a bike.
-Tom
Actually the difference is completely supportive of my point.
The motorcycle has a LOT of weight behind the balance point. The motorcyclist has control of the the degree to which it is behind the balance point by using the brake. When the motorcyclist applies the brake, the torque induced tries to lift the motorcycle up and over the front wheel. Since there is so much weight there (for the lifting), and similarly mass (for the rotational inertia), there is significant braking power.
Note, too, that this is not a panic emergency stop. The motorcyclist is not demonstrating the ability to stop quickly, but rather to feather the brake skillfully. If he jammed on the front brake during that maneuver, he’d crash instantly.
For the motor-unicycle, steady state riding implies that the fore-aft balance point is at the top, and oscillating about that point by means of control systems embedded in the engine control and transmission. There is no reserve behind-the-balance-point leverage to work with. That reserve is what would be required for an emergency stop. If the reserve were there, then the unicycle would be falling backwards, which of course wouldn’t last long. Moreover, the amount of reserve necessary would be speed-dependent. Using a flywheel (or two; one for each side) could work for increasing the effective inertial mass of the uni, but perhaps it would affect side-to-side handling if it were spinning because of the gyroscopic effect. Hmmm… someday…
The use of a brake on a Coker, say, for downhill riding is like the stoppie rather than like an emergency stop.
That page on Craig Jones is amazing! Thanks Klaas.
An “inertial compensator” is definitely required!
Anyhow, that’s my two cents.
using flywheels to ‘hide’ inertia won’t have that much of an effect on handling. the road wheel holds it right before it gets transferred to the flywheel(s). so turning whilst braking (why would you want to do that?) wouldn’t be any more difficult than while not braking. besides, the angular momentum of the wheel is what helps keep the uni upright, at least on the unpowered kind