Turning without countersteering: photographs and test results

James Annan

Simon Brooke wrote:

> in message <cpsid7$9d8$1@scotsman.ed.ac.uk>, Chris Malcolm
> ('cam@holyrood.ed.ac.uk') wrote:
>
>>Isaac Newton disagrees with you. The problem is that shifting any part
>>of your body to one side automatically shifts the rest in reaction in
>>just such a way that the orientation of the perpendicular from the
>>CofG to the line of the contact patch with respect to gravity is
>>preserved.
>
>
> That's true, _ignoring_ _inertia_.
>

It has nothing to do with inertia (please explain how you think inertia
over-rules Newton). It seems that your knowledge of elementary mechanics
is on a par with your knowledge of Godel's theorem. Are you not going to
boast about your degree in metaphysics at this point?


> Yebbut, a moving bicycle is an interesting set of feedback mechanisms
> and servos. The control inputs necessary to correct an out of balance
> condition on a moving bike are orders of magnitude smaller than the
> control inputs required to correct a similar out-of-balance
> displacement of a stationary bicycle. That is (in my opinion) why it's
> easier to balance a moving bike than a stationary one.

So can you balance a moving, but non-steering, bicycle? If not, why not?

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

James Annan

Simon Brooke wrote:

> in message <Xns95C188FE68913pleasegivegenerously@130.133.1.4>, Mark
> Thompson ('pleasegivegenerously@warmmail.com') wrote:
>
>
>>> In order to turn left, you start by turning the handlebars to
>>> the
>>>right for a moment. This moves the front wheel out to the right of
>>>the center of gravity, so the bike will start to fall to the left.
>>>This is immediately follwed by turning the handlebars to the left to
>>>cause the bike to remain in balance, which also creates the desired
>>>left turn. "Countersteering" refers to the momentary motion of the
>>>handlebars in the opposite direction of the desired turn.
>>
>>So the only reason we countersteer is to lean the bike over? If we
>>can also lean the bike over just by shifting our weight then a
>>countersteer is
>>not necessary to initiate a turn. The question is, is it possible to
>>shift our body to the side without also turning the handlbars?
>
>
> How do you ride a bike no hands?

According to the description from Fajans in Am J Physics:


Alternately, the required lean can be generated by throwing your hips in
the direction counter to the turn. Throwing your hips is how a bike is
steered no-hands. The sign of the effect is subtle, but a half-hour
session in an empty parking lot should convince you that while riding
no-handed, you steer the bike by leaning your shoulders in the direction
of the desired turn. Since angular momentum is conserved by a sudden
shift of your shoulders, your hips move the opposite way, thereby
leaning the bike the opposite way as well. With the bike now leaning,
the bike’s "trail" becomes important. As the steering axis is not
vertical, the point of contact of the wheel with the road "trails" the
intersection of the steering axis with the road (see fig 1a). The trail
makes the bike self-steer: when the bike leans to the left, the front
wheel steers left; when the bike leans to the right, the front wheel
steers right. This effect is easily demonstrated by standing beside a
bicycle and leaning it from side to side. The trail is the single most
important geometric parameter which enters into the handling of a bicycle.)
The complete hip-turn sequence is similar to the countersteer sequence
illustrated in Fig. 1, except that you initiate the turn by throwing
your hips left. The bike leans left as well, and the trail steers the
wheel left. Centrifugal torques then lean the center of mass to the
right, and gyroscopic forces eventually steer the wheel right.



Do you have a problem with that description?

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

David Martin

James Hodson wrote:

>
> While cycling slowly ina queue of traffic today I was thinking about
> steering in general. Assuming that both hands are on the bars and
> ignoring counter-steering (counta-rap!), when turning left does one
> pull with the left hand, push with the right, or both? Not that it
> really matters.

Lean on the left hand.

...d

Paul - xxx

James Annan composed the following ...
> Paul - xxx wrote:
>
>> Clive George composed the following ...
>>
>>> "Paul - xxx" <notcheckedever@hotmail.com> wrote in message
>>> news:32di9uF3kbf6lU1@individual.net...
>>>
>>>> James Annan composed the following ...
>>>>
>>>>> James Annan wrote:
>>>>>
>>>>>
>>>>>> From "Steering in bicycles and motorcycles", J. Fajans, Am. J. Phys.
>>>>>> 68
>>>>>
>>>>>
>>>>> That's annoying. Half my post vanished. The full ref is Vol 68 No 7,
>>>>> pp 654-659, 2000.
>>>>>
>>>>> And the quote taken directly from the abstract was supposed to be:
>>>>>
>>>>> "Steering a motorcycle or bicycle is counterintuitive; to turn right,
>>>>> you must steer left initially, and vice versa. You can execute this
>>>>> initially counter-directed turn by turning the handlebars explicitly
>>>>
>>>> I disagree that we 'must' use countersteering .. when we can obviously
>>>> also steer without counter-steering.
>>>
>>> I think what you think of as steering without counter-steering is merely
>>> steering withough explicitly countersteering - during the normal course
>>> of riding in a straight line, the bike wobbles a little tiny bit, and
>>> all you do is unconsciously use one of those wobbles to provide the
>>> necessary countersteer to initiate your turn.
>>
>>
>> I guess we'll have to disagree then ..
>>
>
> If you can do what you claim, you would also be able to balance a
> non-steering bicycle. That seems to me to be the most direct proof that
> this idea of Simon's is nonsense.

I think the speed of body movement and co-ordination required might make
that a little awkward, but I'd give it a go, if I had a non-steering bike,
but I'm not prepared to screw perfectly good bikes up just to prove a point
that I make on Usenet. I merely believe that counter steering is not
necessary to induce a turn. It is helpful, simple, advantageous, intuitive
and probably accounts for 99% (halfwit numbers, ie made-up, badly researched
and probably wrong) of turns made, but it is not necessary to initiate a
turn.

I don't need, require or demand proof of counter-steering from anyone, I do
it personally, empirically ..

--
Paul ...
http://www.4x4prejudice.org/index.php
(8(!) Homer Rules ...
"A tosser is a tosser, no matter what mode of transport they're using."

James Annan

Simon Brooke wrote:


> However, Newton would have been the first to point out that you _can_
> move your centre of gravity, briefly, by exploiting inertia.

How? What is this "exploiting inertia", in terms of the forces applied
by each component on each other?

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

Clive George

"Paul - xxx" <notcheckedever@hotmail.com> wrote in message
news:32ej82F3lipf7U1@individual.net...

> (halfwit numbers, ie made-up, badly researched and probably wrong)

Now look what you've done - you wrote that message, and a minute later he
appeared!

cheers,
clive

David Martin

James Annan wrote:

>
> No, you happen to be invincibly ignorant. But never mind, as my wife
> reminded me only yesterday, only a few centuries ago no-one knew
> anything at all about Newton's laws, so I shouldn't be too hard on a few
> laggards who still don't understand them now.

But the equal and opposite reaction only occurs in a closed system. You,
by only considering the cyclist and not the planet to which he is
connected via the tyre, cannot apply Newton's laws in such a way.

...d

Mark McN

Response to James Annan:
> Have you tried the locked headset yet?
>

Boredom compels me to throw a thought experiment into the mix.


You're riding a non-steering bike. This is difficult, so before too long
- a matter of seconds, even - you find yourself beginning to fall to one
side or the other.

Automagically the steering is restored. Which way do you turn the
handlebars to stop falling? Which direction are you now going in?

You've changed direction. Has counter-steering happened?


--
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.

Paul - xxx

James Annan composed the following ...
> Paul - xxx wrote:
>
>
>> Sorry, I earlier said 'nuff said' .. I'm going to stick to that as I
>> don't think you'll persuade me and likewise I don't think I'll persuade
>> you. I just happen to be right ..
>
> No, you happen to be invincibly ignorant.

I'm also in awe at your ability to make friends and influence people ..

> But never mind, as my wife
> reminded me only yesterday, only a few centuries ago no-one knew
> anything at all about Newton's laws, so I shouldn't be too hard on a few
> laggards who still don't understand them now.

What about the force exerted by the frictio of the tyre against the road?
When you lean left to turn left, with no steering input, the tyre tries to
push right, but the road exerts frictional forces, pushing it back, thus you
start to fall over, when the cycle geometry takes over and steers away from
straight to the left. Note, the steering hasn't gone to the right in any
way, shape or form.. If you leaned left on ice, with no steering input, the
tyre (and bicycle and you) would slide away to the right.

--
Paul ...
http://www.4x4prejudice.org/index.php
(8(!) Homer Rules ...
"A tosser is a tosser, no matter what mode of transport they're using."

Paul - xxx

Clive George composed the following ...
> "Paul - xxx" <notcheckedever@hotmail.com> wrote in message
> news:32ej82F3lipf7U1@individual.net...
>
>> (halfwit numbers, ie made-up, badly researched and probably wrong)
>
> Now look what you've done - you wrote that message, and a minute later he
> appeared!

I must most humbly apologise.

Should I resign as well, or can peccadillos of this magnitude be hushed up,
I wonder?



--
Paul ...
http://www.4x4prejudice.org/index.php
(8(!) Homer Rules ...
"A tosser is a tosser, no matter what mode of transport they're using."

Mark Thompson

> You've changed direction. Has counter-steering happened?

Aparrently yes, according to someone that replied to me, but I couldn't see
how. I think I'm missing something about this whole countersteering lark.

David Martin

Mark Thompson wrote:
>>You've changed direction. Has counter-steering happened?
>
>
> Aparrently yes, according to someone that replied to me, but I couldn't see
> how. I think I'm missing something about this whole countersteering lark.

If you turn towards one direction to effect a change in velocity away
from that direction, would that be a definition of counter steering?

If so you can't ride a bike without it.

As you fall to the left the bike turns to the left so you turn to the
left which makes your lean insufficient to counter the centripetal force
caused by the turn so you begin to fall to the right so you turn to the
right and the turn to the right is now producing sufficient force to
cause you to fall to the left, and so on. In going round a corner it is
not so much 'fall to the other side' as 'not fall to the side so
quickly' followed by overcompensate for the change in falling.

Or something like that.

I'd be interested to see anyone demonstrate riding without countersteer
as defined above.

...d

James Annan

"But the equal and opposite reaction only occurs in a closed system.
You,
by only considering the cyclist and not the planet to which he is
connected via the tyre, cannot apply Newton's laws in such a way."

No, you can resolve the forces acting around the contact point, in
which case any force acting _through_ that point has no moment. Given a
sufficiently wide and stiff-carcased tyre, it is not strictly true, and
I am sure that some MTB tyres can stand on edge by themselves, but this
is not what Simon is claiming.

Honestly, this is trivial mechanics, the sort of thing that most of you
probably forgot before leaving school.

As Chris Malcolm put it:

"It is possible to very clever with relative accelerations and
distances above the contact patch to defeat this equilibrium, but it
is a hard trick to learn, e.g. the small number of people who can
balance on a stationary bike (a bike which is rolling back and forth a
bit is not stationary)."

Given that just about everyone can ride a bike, and many of them can
hardly balance on one foot let alone the far narrower and less rigid
contact of a bicycle tyre, it is clear that the bicycle riding does not
usually use these highly specialised skills. It would be astonishing if
all the remotely scholarly work on how bicycles are controlled were to
have overlooked the dominant method, as Simon claims. His extraordinary
claims certainly require more than a fuzzy photograph and vague
handwaving about "inertia" to back them up.

James

James Annan

"Boredom compels me to throw a thought experiment into the mix.

You're riding a non-steering bike. This is difficult, so before too
long
- a matter of seconds, even - you find yourself beginning to fall to
one
side or the other.

Automagically the steering is restored. Which way do you turn the
handlebars to stop falling? Which direction are you now going in?

You've changed direction. Has counter-steering happened?"

No.

Now all you need to be able to do is maintain your balance in this
state indefinitely, and then choose which side you want to fall to, and
you will have proved that bicycles can be controlled without
countersteering. Can you do this, even in your thought experiment?
James