# stabilising weight?

During lunchtime at work today, my colleague John (not a unicyclist)
made a suggestion which we developed into the following. Suppose you
have a large-wheel unicycle, at least 36" diameter but preferably even
much larger. Suppose you would extend the frame below the axle, almost
to the ground, and you would attach a heavy weight down there (on both
sides). It would at least aid in keeping the uni upright in the
front/rear direction. If the added weight were heavy and low enough,
the uni would keep upright automatically, again only front/rear. The
unicyclist now only needs to control left/right balance by steering as
he goes forward, similar to what a bicyclist does (though steering is
obviously different). If nothing else, it might help the learning
process.

I’m not sure if this suggestion is practically usable but it might be.
Thoughts anyone?

Klaas Bil

If you had this signature, I have forged it.

I love that signature!

Re: stabilising weight?

Sofa wrote:
>
> I love that signature!
>
Yea. It used to be mine…

Re: stabilising weight?

Klaas Bil wrote:
>
> During lunchtime at work today, my colleague John (not a unicyclist)
> made a suggestion which we developed into the following. Suppose you
> have a large-wheel unicycle, at least 36" diameter but preferably even
> much larger. Suppose you would extend the frame below the axle, almost
> to the ground, and you would attach a heavy weight down there (on both
> sides). It would at least aid in keeping the uni upright in the
> front/rear direction. If the added weight were heavy and low enough,
> the uni would keep upright automatically, again only front/rear. The
> unicyclist now only needs to control left/right balance by steering as
> he goes forward, similar to what a bicyclist does (though steering is
> obviously different). If nothing else, it might help the learning
> process.
>

I’m not a physics major, but wouldn’t the counter weight at the bottom
develop it’s own inertia and potentially be problem by turning the rider
into a human pendulum?

Jason

The extra weight would do nothing to stabelize the unicycle, unless it was located below where the whele came in contact with the surface. This could only be done while rideing on a horizontal pole or rope. This is an isue of where the center of mass is located in the system.

Re: stabilising weight?

Although the idea is good, it would end up being very, very heavy. Your
design could be called the Archimedes Uni since it utilizes the lever
principle that he formalized.

At that short distance from the axle, a weight of (as my assistant Harper
manipulates his giant sliderule to calculate) one thousand pounds would be
needed to counter-balance my big asymmetrical body weight. That’s alotta
weight on one tire.

This has been done in that remote control unicycle done by a couple of
students. Their unicycle didn’t have much up on top and so not much counter
weight (batteries and motor) was needed. Someone have the link?

If you built one, and if you had a UPD on a hill, would you run after it or
run the other way?

Doug

“Klaas Bil” <klaasbil_remove_the_spamkiller_@xs4all.nl> wrote in message
news:3d7922c8.5848416@newszilla.xs4all.nl…
> During lunchtime at work today, my colleague John (not a unicyclist)
> made a suggestion which we developed into the following. Suppose you
> have a large-wheel unicycle, at least 36" diameter but preferably even
> much larger. Suppose you would extend the frame below the axle, almost
> to the ground, and you would attach a heavy weight down there (on both
> sides). It would at least aid in keeping the uni upright in the
> front/rear direction. If the added weight were heavy and low enough,
> the uni would keep upright automatically, again only front/rear. The
> unicyclist now only needs to control left/right balance by steering as
> he goes forward, similar to what a bicyclist does (though steering is
> obviously different). If nothing else, it might help the learning
> process.
>
> I’m not sure if this suggestion is practically usable but it might be.
> Thoughts anyone?
>
> Klaas Bil
>
> If you had this signature, I have forged it.

Here is my guess at this hypothetical unicycle.

Unless the weight is enough to actually balance the rider up on top ( the 1000 pounds from Doug’s calculation), it would actually make it harder. If you were perfectly balanced on top, the weight would help keep you from falling (versus no weight). BUT, once you were no longer perfectly balanced (nearly all the time), this weight would make it more difficult to get yourself back to the balanced position. Has to do with the torque required to keep yourself upright. (The further the weight is from the axis, the more work require to move it.)

So, if you can keep perfect balance, the weight might help you. Otherwise, might cause more problems than one can handle.

This is my guess, anybody else agree or disagree? (P.S. I’m relatively new to the unicycle scene, but I know some physics.)

i personally think that the weight MIGHT help, but overall it would make unicycling impossible with the hills and getting started. it might be good for getting usted to the unicycle seat, but otherwise, it’s gonna be harder and more painful then learning to ride.

The idea is based on the superficially obvious but nevertheless wrong idea that the unicycle pivots around the axle. When the unicycle leans forwards or backwards, the important thing is where it contacts the ground. So, putting a weight beneath the axle would help to balance the rider only if the wheel were fixed in position: nailed or bolted to the ground!

Even then, the weight of the rider might be 10 stone or more. The rider’s centre of mass may be 30 - 40 inches from the axle. The radius of the wheel is much less than that, so for the weight to clear the ground but keep the rider upright, it would need to be more than the weight of the rider.

So: screw bolt or nail the wheel firmly to the ground and hang a 25 stone weight beneath the axle, attached to fork extensions, and yes, the rider would find balancing much easier. However, this mechanism would introduce new challenges to the rider - not least when hopping, gapping or crank grabbing.

Practise practise practise: it’s cheaper, lighter and easier to pack.

Re: stabilising weight?

On Sun, 8 Sep 2002 09:11:38 -0500, Mikefule
<Mikefule.ao0jm@timelimit.unicyclist.com> wrote:

>
>The idea is based on the superficially obvious but nevertheless wrong
>idea that the unicycle pivots around the axle. When the unicycle leans
>forwards or backwards, the important thing is where it contacts the
>ground. So, putting a weight beneath the axle would help to balance the
>rider only if the wheel were fixed in position: nailed or bolted to the
>ground!
For the left-right balance I agree, but for the forward-backward
balance I don’t. If the rider leans forward and does no effort to
upright himself, there is no reason for the wheel to move
horizontally. (Otherwise leaning would provide a driving force - hey,
perpetuum mobile!) Just as a thought experiment, I imagine a wheel
with a certain width so that it doesn’t fall to the side. If the
bottom weight is heavy enough it would upright the unicycle.

>Even then, the weight of the rider might be 10 stone or more. The
>rider’s centre of mass may be 30 - 40 inches from the axle. The radius
>of the wheel is much less than that, so for the weight to clear the
>ground but keep the rider upright, it would need to be more than the
>weight of the rider.
Yes, with practical dimensions it would probably need to be at least 3
times the weight of the rider (which in itself is impractical). A very
large wheel would help somewhat.
>
>So: screw bolt or nail the wheel firmly to the ground and hang a 25
>stone weight beneath the axle, attached to fork extensions, and yes, the
>rider would find balancing much easier. However, this mechanism would
>introduce new challenges to the rider - not least when hopping, gapping
>or crank grabbing.
>
>Practise practise practise: it’s cheaper, lighter and easier to pack.
I agree, this thing would not be practical. Heavy on the tyre too,
with a fourfold weight. But fun thinking of, and maybe sometime
someone will pick this up as some engineering to try.

Klaas Bil

If you had this signature, I have forged it.

Re: Re: stabilising weight?

Yes, you are right and I was wrong. And to make it worse, I used the same example in a different discussion on this very forum a few weeks back. I don’t know what came over me. I am indeed a wretched fellow. :0(

Re: stabilising weight?

On Fri, 6 Sep 2002 21:06:04 -0500, Ground-rider
<Ground-rider.al8bc@timelimit.unicyclist.com> wrote:

>The extra weight would do nothing to stabelize the unicycle, unless it
>was located below where the whele came in contact with the surface.
>This could only be done while rideing on a horizontal pole or rope.
>This is an isue of where the center of mass is located in the system.

I still think it would work, see my response to Mikefule.

Klaas Bil

If you had this signature, I have forged it.

Re: stabilising weight?

On Sat, 7 Sep 2002 16:43:17 -0500, jdkimble
<jdkimble.amqxy@timelimit.unicyclist.com> wrote:

>Unless the weight is enough to actually balance the rider up on top (
>the 1000 pounds from Doug’s calculation), it would actually make it
>harder. If you were perfectly balanced on top, the weight would help
>keep you from falling (versus no weight). BUT, once you were no longer
>perfectly balanced (nearly all the time), this weight would make it more
>difficult to get yourself back to the balanced position. Has to do with
>the torque required to keep yourself upright. (The further the weight
>is from the axis, the more work require to move it.)
>
>So, if you can keep perfect balance, the weight might help you.
>Otherwise, might cause more problems than one can handle.
>
>This is my guess, anybody else agree or disagree? (P.S. I’m relatively
>new to the unicycle scene, but I know some physics.)

If you can keep perfect balance you don’t need this weight or anything
else. But if your balance is slightly off, the bottom weight (rather
than being a nuisance) restores it. Surely, the farther the weight is
from the axle, the more torque you would need to move it by muscle
power. But gravity does that moving for you, and gets you back upright
in the process.

Klaas Bil

If you had this signature, I have forged it.

Re: stabilising weight?

On Sat, 7 Sep 2002 20:16:35 -0500, uni_boy50
<uni_boy50.an0nz@timelimit.unicyclist.com> wrote:

>i personally think that the weight MIGHT help, but overall it would make
>unicycling impossible with the hills and getting started. it might be
>good for getting usted to the unicycle seat, but otherwise, it’s gonna
>be harder and more painful then learning to ride.

I agree. But if someone made it, it would be fun to try and feel what
it’s like.

Klaas Bil

If you had this signature, I have forged it.

Re: stabilising weight?

On Fri, 06 Sep 2002 15:31:06 -0800, Jason Neumann
<nospam@nospam.no.no.no> wrote:

>I’m not a physics major, but wouldn’t the counter weight at the bottom
>develop it’s own inertia and potentially be problem by turning the rider
>into a human pendulum?

Yes you could get into an oscillatory movement if you would apply a
rhythmic/periodic force. That might be some sort of fun in its own
right, though.

Klaas Bil

If you had this signature, I have forged it.

Re: stabilising weight?

On Sat, 07 Sep 2002 02:52:08 GMT, “Doug Massey” <dvm@mmcable.com>
wrote:

>If you built one, and if you had a UPD on a hill, would you run after it or
>run the other way?

Depends on which side you dismount. But, really, you would not UPD at
all. Simply stay put, and you will get back on top automatically. Hey
Gilby, is this your autobalance unicycle?

Doug, I’m interested in that remote control unicycle. How does it keep
left/right balance?

Klaas Bil

If you had this signature, I have forged it.

Re: stabilising weight?

Here ya go… http://www.boltontech.org.uk/loony_cycle.htm

“Klaas Bil” <klaasbil_remove_the_spamkiller_@xs4all.nl> wrote in message
news:3d7d3e30.14246233@newszilla.xs4all.nl…
>> Doug, I’m interested in that remote control unicycle. How does it keep
> left/right balance?

Re: stabilising weight?

Klaas Bil wrote:

> Yes you could get into an oscillatory movement if you would apply a
> rhythmic/periodic force. That might be some sort of fun in its own
> right, though.

Yes. I think it’s called a Trebuche.

Jason

After a…well interesting uni ride on the unicycle previously mentioned…

“Ok, whose turn is it to load this heavy thing into the truck?”

aaron

Re: stabilising weight?

On Wed, 11 Sep 2002 14:58:23 -0800, Jason Neumann
<nospam@nospam.no.no.no> wrote:

>Yes. I think it’s called a Trebuche.

Trebuchet. But only if you allow your head to go ballistic, something
I wasn’t planning on…

Klaas Bil

If you had this signature, I have forged it.