Re: Fell off

in message <[email hidden]>, Richard

(') said:

Simon Brooke said:

a normal bike
turns if you lean it. It is this fact combined with body movement
which makes riding no hands possible - I assume you _can_ ride no
hands.

It depends on the geometry - I can ride no hands on my town runaround,
but on my elderly road bike it's impossible. [1]

Oh, indeed. When I first got my Jekyll I couldn't ride it no hands. I
thought this must be a feature of the lefty fork until I took the
remote rear lockout control off, when it became easy to ride no
hands... it was the springyness of the cable which had been upsetting
the handling.

Bike steering is by and large pretty sensitive; it needs only very small
forces to steer a bike.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; If you're doing this for fun, do what seems fun. If you're
;; doing it for money, stop now.
;; Rainer Deyke

Simon Brooke said:

Quoted message said:

but has little to do with normal bike riding (even
hands off)

Evidence, please? I believe it has everything to do with normal bike
riding.

Because if you could do what you claim, you could ride a bike with a
locked headset. And you can't, unless perhaps you are a circus performer
or an extremely well-practised trials rider.

(Actually, tipping the bike from side to side will shift the contact
patch perhaps a centimetre - even an inch with fat tyres - but this is
certainly an insufficient margin for the vast majority of humans to
balance indefinitely, and therefore cannot explain how they are doing it
in normal riding.)

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

Simon Brooke said:

in message <[email hidden]>, James Annan
([email hidden]'😉 wrote:

Quoted message said:

Quoted message said:

As I've already mentioned, the tightrope moves laterally under the
performer.

I suggested to you that you try this yourself with a line on the floor.
Are you suggesting that the whole building moves? If the whole building
does not move, how does the trick work?

As I said, the width of my foot provides ample margin - several inches,
so long as I can keep my CoG within those bounds there is no problem.
With a tyre contact patch, there is no way of moving the centre of
pressure without actually moving the contact patch itself - which
leaning the bike will do, but only a very small amount. If you claim
this is adequate for you to balance, then you are mch more talented than
me and should also be able to balance (and ride) a bike with locked
headset. Can you do this?

Quoted message said:

No, clearly you can't, because that bike cannot turn; a normal bike
turns if you lean it. It is this fact combined with body movement which
makes riding no hands possible - I assume you _can_ ride no hands.

But a minute ago, you were claiming that you can bodily move your CoG
from side to side by significant amounts just with a wiggle of your hips
while sitting on your bike. Are you now admitting that you can't do this
after all? Does "adjust your balance and carry on normally" (from your
description of hands-free riding) involve steering the bike so that it
moves back under the rider, or the rider moving himself to catch up with
where the contact patch went?

Let's go back to the top here: you are claiming that, starting from a
balanced position, you can turn right just by moving your CoG to that
side, without any need to countersteer. In that case, why can you not
move your CoG from side to side at will to maintain balance on a bike
with fixed headset (which might as well be stationary)? Could it be that
your mental model of what you think you are doing, does not match
reality? If not, then what else do you suggest as a reason?

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

Simon Brooke said:

Quoted message said:

The bike would not need to turn. In order to ride a straight line the
cyclist would simply need to keep the combined CofG of himself and the
bike directly over the line between the contact patches of the two
tyres.

I suspect that's not possible (or at least exceedingly difficult) unless
you are a highly trained acrobat.

I suspect it's just within the bounds of the possible.

Quoted message said:

In any case, places where you could
ride a bike which is only capable of travelling in a straight line are
pretty rare.

Large field? I didn't think we were discussing the bike with locked
steering as practical transport, but rather as an exercise in
investigating stability. So what if the opportunities to ride one are
somewhat limited?

--
Dave...

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

in message <[email hidden]>, James Annan

(') said:

Simon Brooke said:

Quoted message said:

but has little to do with normal bike riding (even
hands off)

Evidence, please? I believe it has everything to do with normal bike
riding.

Because if you could do what you claim, you could ride a bike with a
locked headset. And you can't, unless perhaps you are a circus
performer or an extremely well-practised trials rider.

I don't see that that follows, at all. Very small inputs will steer a
bicycle with unlocked steering, and, as you acknowledge, steering a
bicycle moves the contact point WRT the CoG. Consequently the bicycle's
inherent lean steer acts as a servo mechanism, transforming relatively
small inputs into relatively large corrections.

Again, I suggest to you that you are allowing theory to blind you to
empiricism; you are so certain that you are right that you are not
prepared to actually get on a bike and try it. Theory is fine in
itself, of course, but testing it against the real world is better.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
.::;===r==\
/ /___||___\____
//==\- ||- | /__\( MS Windows IS an operating environment.
//____\__||___|_// \|: C++ IS an object oriented programming language.
\__/ ~~~~~~~~~ \__/ Citroen 2cv6 IS a four door family saloon.

in message <[email hidden]>, James Annan

(') said:

Simon Brooke said:

in message <[email hidden]>, James Annan
([email hidden]'😉 wrote:

Quoted message said:

Quoted message said:

As I've already mentioned, the tightrope moves laterally under the
performer.

I suggested to you that you try this yourself with a line on the
floor. Are you suggesting that the whole building moves? If the whole
building does not move, how does the trick work?

As I said, the width of my foot provides ample margin - several
inches, so long as I can keep my CoG within those bounds there is no
problem.

So place a plank on its edge on the floor, clamping it so that it can't
fall over, and stand on that. Yes, I have done it. Yes, you (or at
least I) can balance on it just as easily. If you won't try the
empirical experiment then we really are arguing about angels and
pinheads.

Quoted message said:

But a minute ago, you were claiming that you can bodily move your CoG
from side to side by significant amounts just with a wiggle of your
hips while sitting on your bike. Are you now admitting that you can't
do this after all? Does "adjust your balance and carry on normally"
(from your description of hands-free riding) involve steering the bike
so that it moves back under the rider, or the rider moving himself to
catch up with where the contact patch went?

This is simply getting silly. Get out on a bike and ride it, no hands,
and then come back with an explanation of how you initiated a 'counter
steer'. If, as you say, a turn cannot be initiated without counter
steer, then, no hands, the counter steer cannot be initiated either;
conversely, if the 'counter' steer can be initiated, then it can be
continued into a turn to the same side - and yes, you will, whether you
like it or not, "adjust your balance and carry on normally". The
movement of the body and of the contact patch form part of the same
feedback loop - the body responds to movements of the contact patch,
and the contact patch responds to movements of the body.

Find a dry road with a puddle on it; ride through the puddle, then
initiate the turn, then go back and look at the wheel tracks. Theory is
fine, but the real world is better.

And remember, I'm not saying you _can't_ counter steer. I know you can.
I'm saying you _don't_ _have_ _to_. So a photograph of tracks showing
counter steer does not disprove what I'm saying. But a photograph of
tracks clearly not showing counter steer clearly does prove what I'm
saying. I'll take one as soon as the rain stops.

Time to put up or shut up.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

;; Semper in faecibus sumus, sole profundum variat.

Simon Brooke said:

So place a plank on its edge on the floor, clamping it so that it can't
fall over, and stand on that. Yes, I have done it. Yes, you (or at
least I) can balance on it just as easily. If you won't try the
empirical experiment then we really are arguing about angels and
pinheads.

Ok, let's walk through this very slowly, one point at a time.

You can balance on a plank edge, but not on a bicycle with fork fixed
straight ahead (I think we probably agree it doesn't matter much whether
the bicycle is rolling or stationary). Can you identify the significant
difference(s) between the two cases?

Quoted message said:

This is simply getting silly. Get out on a bike and ride it, no hands,
and then come back with an explanation of how you initiated a 'counter
steer'. If, as you say, a turn cannot be initiated without counter
steer, then, no hands, the counter steer cannot be initiated either;

That is simply nonsense. It is easy to explain how countersteering works
with hands-free riding. Going from straight ahead into a right turn: tip
the bike to the left, and rider to the right (combined CoG will not move
significantly). The bike turns to the left, the tyre contact point moves
to that side away from under the rider. Then tip the bike back to the
right and rider towards the left - but keeping the rider somewhat to the
right of the contact patch (it would be hard to avoid doing this). The
bike will be leaning right, and the bike plus rider go round the corner
together. During this procedure, the combined CoG of bike and rider
hardly moves laterally, but the tyre contact patch moves to the left
thus enabling the turn to take place.

You, on the other hand, seem to be proposing the following: in order to
turn right, you tip the bicycle to the right, and the rider to the left.
The bicycle turns right, and the contact point moves away from under the
rider. Then, the rider somehow manages to haul himself back across to
the _other_ (RH) side of the contact patch even as it is running away
from him, a near-miraculous process that you dismiss without explanation
as "adjust your balance and carry on normally". During this procedure,
the CoG moves substantially to the right, even while it is being pushed
in the opposite direction (by the ground reaction force as soon as the
contact patch moves from under the rider).

Since you claim to be able to do this, it is not clear why you do not
believe you can also do it in the case where the bicycle is constrained
to run in a straight line. In that case, you have less far to go to get
back on top of the contact patch, which must make it easier. So why is
it somehow harder?

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

in message <[email hidden]>, James Annan

(') said:

Simon Brooke said:

So place a plank on its edge on the floor, clamping it so that it
can't fall over, and stand on that. Yes, I have done it. Yes, you (or
at least I) can balance on it just as easily. If you won't try the
empirical experiment then we really are arguing about angels and
pinheads.

Ok, let's walk through this very slowly, one point at a time.

You can balance on a plank edge, but not on a bicycle with fork fixed
straight ahead (I think we probably agree it doesn't matter much
whether the bicycle is rolling or stationary). Can you identify the
significant difference(s) between the two cases?

Yes. I don't have a bicycle with its steering fixed straight ahead, so I
can't verify it. I do have a blank, and I have tried that.

Quoted message said:

Quoted message said:

This is simply getting silly. Get out on a bike and ride it, no
hands, and then come back with an explanation of how you initiated a
'counter steer'. If, as you say, a turn cannot be initiated without
counter steer, then, no hands, the counter steer cannot be initiated
either;

That is simply nonsense. It is easy to explain how countersteering
works with hands-free riding. Going from straight ahead into a right
turn: tip the bike to the left, and rider to the right (combined CoG
will not move significantly).

Fine. Having done that, what makes it impossible to continue to turn
_to_ _the_ _left_?

Quoted message said:

Since you claim to be able to do this, it is not clear why you do not
believe you can also do it in the case where the bicycle is
constrained to run in a straight line. In that case, you have less far
to go to get back on top of the contact patch, which must make it
easier. So why is it somehow harder?

It is still raining here. I cannot get clear photographs this morning. I
shall post photographs as soon as possible. But it really would be
easier if you would just get out on your bike and try it.

JPEGs, as they say, or retract. Have no doubt that I shall post mine.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
;; This email may contain confidential or otherwise privileged
;; information, though, quite frankly, if you're not the intended
;; recipient and you've got nothing better to do than read other
;; folks' emails then I'm glad to have brightened up your sad little
;; life a tiny bit.

Simon Brooke said:

in message <[email hidden]>, James Annan

(') said:

You can balance on a plank edge, but not on a bicycle with fork fixed
straight ahead (I think we probably agree it doesn't matter much
whether the bicycle is rolling or stationary). Can you identify the
significant difference(s) between the two cases?

Yes. I don't have a bicycle with its steering fixed straight ahead, so I
can't verify it. I do have a blank, and I have tried that.

You must be getting close to realising you are wrong now you are ducking
such a straightforward question.

Quoted message said:

Quoted message said:

That is simply nonsense. It is easy to explain how countersteering
works with hands-free riding. Going from straight ahead into a right
turn: tip the bike to the left, and rider to the right (combined CoG
will not move significantly).

Fine. Having done that, what makes it impossible to continue to turn
_to_ _the_ _left_?

The fact that the rider's CoG is already to the RIGHT of the contact
patch, and therefore the ground reaction force is pushing him _further_
to the right at the same time that the contact patch is moving to the
left. In order to turn left, the CoG must be inside the bend relative to
the contact patch.

If you can find me a picture of a cyclist going round a bend while
leaning out rather than in (outside of the contact patch, not just at a
different angle to the bike), I'd be very interested!

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