Turning without countersteering: photographs and test results

Dave Kahn

On Fri, 17 Dec 2004 11:23:27 +0000, David Martin
<d.m.a.martin@dundee.ac.uk> wrote:

>What about a swing? Surely it is impossible for a swing to start moving from
>rest if there is always a net resultant of 0.

Not at all. A child on a swing appears to be able to move her C of G
without anything to push against but actually this is not the case. As
she grips the ropes and pumps, she provides a force that moves the
seat and much of her body in one direction. There is of course an
equal force acting in the opposite direction. Some of this goes into
the frame of the swing which is attached to the ground. It is the
reaction force from the ground that causes the common C of G of the
frame, swing and little girl to move.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Dave Kahn

On Sat, 18 Dec 2004 10:56:18 +0000, "Just zis Guy, you know?"
<uce@ftc.gov> wrote:

>On Fri, 17 Dec 2004 21:46:36 +0900, James Annan
><still_the_same_me@hotmail.com> wrote in message
><32g2mlF3jd0l3U2@individual.net>:

>>Maybe so, but Simon is not just debating the semantics, he really seems
>>to believe that he has a method for balancing a bicycle that is
>>physically different from the standard method of steering the contact
>>patch under the rider.
>
>Maybe, maybe not. I haven't read each post in detail because as I say
>it sounds like a particularly silly argument but my understanding of
>his original point (before Usenet hyperbole and digging-in took over)
>is that you can steer without countersteering simply by waiting for
>the bike to fall the right way, which eventually it will, plus a bit
>of blurred distinctions between definitions of countersteer as either
>a conscious and deliberate act to provoke a rapid turn, or a slightly
>exaggerated part of the normal weaving motion of riding a bike.

No, it was I who suggested that we normally steer by simply allowing
the bike to fall to that side. It was the next day before I realised
that this was equivalent to countersteering. Simon actually said a rew
posts ago:

: If you are prepared to go far enough back into the past, before every
: turn to the right there was an oscillation to the left, and vice versa. To
: claim that any such oscillation is causative of the turn or required to make
: the turn is nonsense, however.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Dave Kahn

On Sat, 18 Dec 2004 00:48:58 -0000, Mark McN
<marknospam33@gesualdo.freeserve.co.uk> wrote:

>AIUI (and I may well be wrong) you're defining countersteering as the
>micro-correction (or, of course, a deliberate larger move) which puts the
>CofG on the side of the intended turn. Am I right so far?

Yes. That'll do it for me.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Dave Kahn

On 16 Dec 2004 18:04:34 GMT, Mark Thompson
<pleasegivegenerously@warmmail.com> wrote:

>> It's something like this that I believe is happening in normal cycling.
>> The subtle corrections we constantly make to keep the bike upright are
>> enough to provide the countersteering required to enter a turn. This is
>> why we are not usually aware of doing it. If I want to turn right all I
>> have to do is not let the bike fall to the left.
>
><confused>
>
>Um, so countersteering is moving the handlebars to the right to make us
>fall left, but also moving them to the left to stop us falling left?
>
>It's both a pro-active measure to help us turn, and a reactive measure to
>keep us upright?
>
><still confused>

AIUI only the first part of that is countersteering: turning the bars
to the right to initiate the turn. Once the bars are turned in the
intended direction that is normal steering. The movement required to
make it work is tiny. Try riding no hands then give one side of other
of the bars the gentlest of pushes away from you. It will push back
against you and the bike will begin a turn to that side. It's quite a
startling experiment, and very easily performed.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Dave Kahn

On Sat, 18 Dec 2004 16:54:10 +0000 (UTC), Ian Smith
<ian@astounding.org.uk> wrote:

>> Cats are rotating about their own CoG, so I'm not sure how this is
>> relevant.
>
>Because it demonstrates that it is possible to rotate a body (in teh
>general sense) without having something solid to react against.

Whether you can rotate about your C of G is irrelevant to the
discussion as AFAICS. The non-countersteering turn relies on being
able to move one's C of G without something solid to react against.
Remarkable as the movements of a cat are they do not alter the
trajectory of its C of G.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Dave Kahn

On Fri, 17 Dec 2004 16:36:42 +0000, Richard
<richard@nomail.nospam.thanks> wrote:

>Yes, there is; if the push is momentary and of sufficiently small
>magnitude that the pusher can react before they hit the ground, *and the
>pusher moves out the way fast enough* the pushee can jerk his/herself
>back upright, in exactly the same way that a person standing on one foot
>can do so.

No, it's nothing like standing on one foot where your leg muscles
still have a reasonably wide base to work from. Any jerking the pushee
bicyclist does is ineffective. It sounds to me as though you haven't
actually done the experiment.

>Of course, what usually happens balancing on a stationary bike is that
>the pushee overcompensates the initial push, tries to compensate for
>that, etc, and eventually (FCVO 'eventually') goes too far one way or
>the other to recover. A similar phenomenon is known to pilots as PIO,
>pilot-induced oscillation; a plane in level flight encounters a small
>disturbance which brings the nose up or down in pitch, say down. The
>pilot overcompensates too far, the nose rises, he pushes down but
>overcompensates too far again, the nose dives even more, and the
>resultant oscillations grow in magnitude.

As someone who has both tried the pushing experiment and experienced
PIO in a glider close to the ground on an aerotow I am in a position
to state categorically that you are talking bollocks. There is no
oscillation of the tipping bike. The fall is gentle and inexorable
with no response whatsover to anything the rider does.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Dave Kahn

On 17 Dec 2004 08:25:53 -0800, I wrote:

>Now imagine you are seated on your bicycle. I am standing beside you
>and you are leaning very slightly against me, almost upright. The
>slightest push from me will topple you. You are in intimate contact
>with the bike and its contact area with the ground. Short of putting a
>foot down or grabbing hold of me there is nothing you can do to resist
>that push. I'm going to try this with my kids when I get home. Why
>don't you have a go yourself? It's not a difficult experiment or a
>dangerous one - you can put a foot out as soon as you begin to fall.

There was a short delay before I was able to try this out. When I got
home on Friday evening Mark's end of term report had arrived and his
mother needed to be pacified somewhat before we were allowed to play
in the garage. Even his music report was not as glowing as expected;
although his recent composition exercise was "an interesting piece of
work in which much of the harmony is effective he could have used the
woodwind more effectively." A little harsh, I thought.

However, once down to business results with me pushing Mark were
inconclusive. He was remarkably easy to push over in all situations.
With Mark pushing me things were more as predicted. With a wide stance
he was completely unable to move me unless he started with a run,
which is not fair. With my feet together he was able to tip me with a
bit of an effort. Once on the bicycle, however, things were changed. I
was completely unable to resist his push no matter what I tried.
Leaning away from him simply delayed the inevitable, while leaning
towards him magnified the effect of the push. Keeping my upper body
rigid and trying to get a reaction force from the ground convinced me
that this is quite impossible. Mark could not feel any change in the
resistance to his push.

Of course, while we were able to tell Sue that we were doing
experimental physics it's not a proper scientific experiment. No
measurements of forces were made for a start. Also, the experiment was
not "double blind". As experimenter and subject I had an expectation
in advance of what the results would be, and they did conform to my
expectations so they are invalid from a psychological point of view.
It is, however, an interesting and fun thing to try and I urge anyone
who is still wondering whether thay can move their C of G to the left
or right by leaning, or exploiting the bike's inertia, to give it a
try.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Richard

Dave Kahn wrote:
>>Of course, what usually happens balancing on a stationary bike is that
>>the pushee overcompensates the initial push, tries to compensate for
>>that, etc, and eventually (FCVO 'eventually') goes too far one way or
>>the other to recover. A similar phenomenon is known to pilots as PIO,
>>pilot-induced oscillation; a plane in level flight encounters a small
>>disturbance which brings the nose up or down in pitch, say down. The
>>pilot overcompensates too far, the nose rises, he pushes down but
>>overcompensates too far again, the nose dives even more, and the
>>resultant oscillations grow in magnitude.
>
>
> As someone who has both tried the pushing experiment and experienced
> PIO in a glider close to the ground on an aerotow I am in a position
> to state categorically that you are talking bollocks. There is no
> oscillation of the tipping bike. The fall is gentle and inexorable
> with no response whatsover to anything the rider does.

Well, FWIW I've done both the experiment (although I let myself tip
rather than be pushed) and started up some PIO, albeit in a powered
plane a few thousand feet up. I held the brakes locked and let myself
fall sideways. I could correct a fall to one side with a sharp body
displacement to the other, but that usually put me too far over to
recover a second time. A few occasions I managed a double recovery.
I'm sure someone with more catlike reflexes and more patience than me
could do a few more. Just to be absolutely sure, you are saying that
if you start to tip over to one side from a stationary bike, there is
nothing to you can do to recover? (short of bunnyhops, etc?) I fear if
so it is you that is talking small spheroids.

R.

Ian Smith

On Sun, 19 Dec 2004, Dave Kahn <dkahn400@yahoo.co.uk> wrote:

> The fall is gentle and inexorable
> with no response whatsover to anything the rider does.

I think you're saying it's impossible to still-stand a unicycle.
I can do that.

regards, Ian SMith
--
|\ /| no .sig
|o o|
|/ \|

Mark McN

Response to Ian Smith:
> > The fall is gentle and inexorable
> > with no response whatsover to anything the rider does.
>
> I think you're saying it's impossible to still-stand a unicycle.
> I can do that.
>

It's tempting to say that if the CofG is unchanged by any action of the
rider, once you're perfectly balanced it's impossible *not* to still-
stand a fixed-steering bicycle. ;-)

--
Mark, UK.
We hope to hear him swear, we love to hear him squeak,
We like to see him biting fingers in his horny beak.

Mark McN

Response to Dave Kahn:
> >AIUI (and I may well be wrong) you're defining countersteering as the
> >micro-correction (or, of course, a deliberate larger move) which puts the
> >CofG on the side of the intended turn. Am I right so far?
>
> Yes. That'll do it for me.

I was going to come back to this, but RL intervened, as it has a habit of
doing...


My only real reservation, as somebody else said, is that I think it
weakens the meaning of countersteering to use the term as I described
above; ISTR Richard Ballantine describing the technique of making a large
countersteer to begin a sharp or emergency turn, and I assumed (until
this thread made me think about it) that countersteering referred just to
this. After all, I read his book at the right age for prejudices to
form! ;-) So I'm not nuts about using the term as I used it in my PP,
though I can see the logic behind it.

--
Mark, UK.
We hope to hear him swear, we love to hear him squeak,
We like to see him biting fingers in his horny beak.

James Annan

Richard wrote:

> Just to be absolutely sure, you are saying that
> if you start to tip over to one side from a stationary bike, there is
> nothing to you can do to recover? (short of bunnyhops, etc?) I fear if
> so it is you that is talking small spheroids.

As I've said several times, it is possible to correct small imbalances
by violent waving around of the arms, as you may find yourself doing
when you try to balance on a narrow support. However (as I've also said
several times) if you could do this reliably enough to control a bicycle
by it, you would be able to balance a non-steering one, and virtually
no-one can do that.

James
--
If I have seen further than others, it is
by treading on the toes of giants.
http://www.ne.jp/asahi/julesandjames/home/

Dave Kahn

On Sun, 19 Dec 2004 19:49:17 +0000 (UTC), Richard
<richard@percival.demon.co.uk> wrote:

>Well, FWIW I've done both the experiment (although I let myself tip
>rather than be pushed) and started up some PIO, albeit in a powered
>plane a few thousand feet up. I held the brakes locked and let myself
>fall sideways.

That is not the experiment I described.

> I could correct a fall to one side with a sharp body
>displacement to the other, but that usually put me too far over to
>recover a second time. A few occasions I managed a double recovery.
>I'm sure someone with more catlike reflexes and more patience than me
>could do a few more.

That may be your perception of what you did, but I doubt that's what
actually happened. If you displace your body to one side you can't
help displacing the bike to the other, and the common C of G of the
bike and the rider are not affected.

>Just to be absolutely sure, you are saying that
>if you start to tip over to one side from a stationary bike, there is
>nothing to you can do to recover? (short of bunnyhops, etc?)

As long as the topple has not gone too far you can correct it by
turning the bars. Even when you are not rolling, the steering geometry
will cause the contact patch of the front wheel to move to the side.
You can keep balanced in the same way you can balance a broom on your
hand. When you were throwing your body from side to side were you also
moving the handlebars? It's extraordinarily difficult not to. If so,
this is what was correcting your fall, not the body movements.

> I fear if so it is you that is talking small spheroids.

Possibly, but before we decide just who is talking balls you have to
provide an explanation how you can cheat Newton's third law and move
the common C of G of the bike and rider sideways with nothing to push
against. For example, there will be some rolling resistance in the
tyre, even a round, smooth tyre rolling sideways. Is it enough to
account for your ability to reverse a fall? On a wide knobbly tyre it
just might be. Or maybe it's air resistance. If you had a giant fan
you could probably learn to go well past the point of balance and
still recover. It would be quite a good circus trick, and it might be
one solution to the unrideable bike problem. But is it possible to
move just your body fast enough that the air resistance is enough to
stop you falling? Maybe, but it doesn't seem likely to me.

I'm therefore not saying that it's totally impossible to move one's C
of G sideways, but it appears to me that it is practically impossible
within the parameters of normal cycling. If I'm right the people who
claim to be able to turn simply by leaning in that direction are
deluding themselves because you cannot lean and turn to either side
unless your C of G is already on that side.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain

Dave Kahn

On Sun, 19 Dec 2004 21:08:19 +0000 (UTC), Ian Smith
<ian@astounding.org.uk> wrote:

>On Sun, 19 Dec 2004, Dave Kahn <dkahn400@yahoo.co.uk> wrote:
>
>> The fall is gentle and inexorable
>> with no response whatsover to anything the rider does.
>
>I think you're saying it's impossible to still-stand a unicycle.
>I can do that.

Am I? When you say still-stand do you mean idle, or do you mean with
the wheel completely motionless?

Come to think of it, I used to be very good at balancing a chair on
its two back legs. I could go for nearly a minute before I would have
to save myself by putting a foot either on the floor or the underside
of the desk I was pretending to be working at. Once I was definitely
falling there was no recovery, but at the point of balance I would
sometimes have to throw my weight either backwards of forwards. The
chair would move the other way of course, and usually bring the
balancing session to a rapid conclusion. Sometimes, however, it would
save what seemed to be an imminent fall and I could carry on
balancing. I now have to worry about whether I was actually managing
to move my C of G backwards or forwards, and if so how.

--
Dave...

Get a bicycle. You will not regret it. If you live. - Mark Twain