Fell off

in message <[email hidden]>, [Not

Responding (') said:

Now that we've sorted whether you turn left or right to turn left, can
we move on to whether the wheel hangs or rests on the spokes please.

I'm not going to hang around for that. I couldn't stand it...

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
Das Internet is nicht fuer gefingerclicken und giffengrabben... Ist
nicht fuer gewerken bei das dumpkopfen. Das mausklicken sichtseeren
keepen das bandwit-spewin hans in das pockets muss; relaxen und
watchen das cursorblinken. -- quoted from the jargon file

Simon Brooke said:

The line or tightrope has some of the physics of a bike. On a bike, the
line is the track. However, on a bike, unlike a tightrope, the line can
be moved WRT the mass, by steering.

That's bass-ackwards, of course. The tightrope can (and does) move
sideways under the performer. Look at those two brackets, and imagine
them to be a view of the performer from the rear. The left bracket has
the feet to the right of the CoG, and vice-versa. The bicycle contact
patch can only move sideways if the bicycle is steered to the side.

Quoted message said:

I think you will find that you make jerky movements of your shoulders
and arms. I think you will find that, some of the time at least, the
inertia from these jerky movements is sufficient to correct your
balance. If so, you must concede that this instinctive exploitation of
inertia gives you sufficient torque around the line to actually move
your centre of gravity. And if it works standing on a line, why can it
not work on a bicycle?

Well, standing on a single foot is not much problem for someone with
decent balance - it provides a platform several inches across and
twisting one's ankle can shift the effective pressure point from one
side to the other, giving a fair bit of wobble room before one risks
overbalancing. As the support gets narrower, it gets much harder, until
one (well, me at least) can only resort to increasingly desperate and
wild waving around of the arms. This can generate small temporary
torques, but has little to do with normal bike riding (even hands off)
and only prolongs the inevitable for a few seconds.

If you think you can control your balance a bicycle by this method, then
you should also be able to ride one in which the fork is locked straight
ahead. A few circus performers might be able to manage it, but 99.9% of
riders certainly cannot, and it has nothing to do with 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:

Quoted message said:

So we have the bicycle marginally to the left of the rider, and
turning further to the left.

In the immortal words of David Vine,

"What happens next"?

You adjust your balance and carry on normally. As to how you do this,
see below.

Quoted message said:

Certainly. The issue is entirely in the rapidity of acceleration and
deceleration of body movement, exploiting inertia. If it were not
possible to adjust balance in this way, riding a unicycle, for
instance, or walking on a tightrope, would be impossible. Yet they are
not. If it can be done on a tightrope, why is it impossible on a
bicycle?

As I've already mentioned, the tightrope moves laterally under the
performer. This is also a trick that takes quite some skill (I doubt
many would go to the circus just to see a normal cyclist riding along).
A unicycle is also moved under the rider, in the fore-aft plane as well
as from side to side. The relevance of that to your point is not clear,
but then again, your point is not clear in itself.

Now, back to the cyclist. Assume this time he is not a circus performer.
How does he apply sufficient torque to himself to move himself bodily
from one side to the other of the contact patch. If you believe he can
do this, do you also believe he can ride a bicycle with the forks locked
straight ahead? If not, why not? Surely the same "adjust your balance
annd carry on normally" trick should work there too, shouldn't it?

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

Jon Senior said:

Not sure that counter steer has any effect on trikes. I think the
steering is always positive (I'm sure Mr Larrington can offer an
example of a lean steer trike to prove me wrong though!).

I would imagine counter-steering to be counter-productive on trikes, just as
it would be in a motorcar[1]. There have been leaning trikes, usually with
the paired wheels in the back, but occasionally tadpoles, notable the
Tripendo.

Quoted message said:

Quoted message said:

It might be trikes aren't prone to the same counter-steer effect, of
course, since they a) don't lean over (no two-wheeled cornering for
me, yet)

This is the key point. There is no lean in trike cornering.

Not of the machine, but the rider may wish to lean towards the inside of the
bend in order to keep the inside wheel on the deck and/or keep the rubber on
the outside tyre. I once managed to scrape my martlehat against the road
while negotiating teh Eastway hairpin on a Windcheetah...

1 - except if one is a mad Scandiwegian intent on circumnavigating Finland
without using the clutch

--

Dave Larrington - http://www.legslarry.beerdrinkers.co.uk/
World Domination?
Just find a world that's into that kind of thing, then chain to the
floor and walk up and down on it in high heels. (Mr. Sunshine)

in message <[email hidden]>, James Annan

(') said:

until one (well, me at least) can only resort to increasingly
desperate and wild waving around of the arms. This can generate small
temporary torques,

Thank you, that is what I 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. You are, of course, correct that balancing on a _moving_ bike
is substantially easier than balancing on the edge of a plank, but that
is because very small control inputs ('small temporary torques', in
your own words) are sufficient, in conjunction with the sensitive
lean-steering of a conventional bicycle, to keep the show on the road.

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

Age equals angst multiplied by the speed of fright squared.
;; the Worlock

in message <[email hidden]>, James Annan

(') said:

Simon Brooke said:

Certainly. The issue is entirely in the rapidity of acceleration and
deceleration of body movement, exploiting inertia. If it were not
possible to adjust balance in this way, riding a unicycle, for
instance, or walking on a tightrope, would be impossible. Yet they
are not. If it can be done on a tightrope, why is it impossible on a
bicycle?

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?

Quoted message said:

Now, back to the cyclist. Assume this time he is not a circus
performer. How does he apply sufficient torque to himself to move
himself bodily from one side to the other of the contact patch. If you
believe he can do this, do you also believe he can ride a bicycle with
the forks locked straight ahead? If not, why not? Surely the same
"adjust your balance annd carry on normally" trick should work there
too, shouldn't it?

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.

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

Morning had broken. I found a rather battered tube of Araldite
resin in the bottom of the toolbag.

In article said:

Velvet said:

I was asking but from a slightly different perspective, that of having
tried a 'bent tadpole. I remembered feeling something the first few
times I steered (then got used to it) where it felt almost like it
wanted to go the opposite direction to where I'd just told it to, then
would snap back to the 'right' way we were turning. At the time I
thought it was possibly just bodyweight shifting to the 'outer' side of
the turn before I compensated to lean 'in' to the turn, but what you
said made me wonder :-)

Not sure that counter steer has any effect on trikes. I think the
steering is always positive (I'm sure Mr Larrington can offer an example
of a lean steer trike to prove me wrong though!).

http://www.maxmatic.com/ttw_hpv.htm but I wouldn't swear any of them rely
on countersteer (I think the Aileron would, in high speed "unlocked" mode).

A "virtual single-track"/"free lean" tilting three-wheeler like
http://www.moebius.es/ccalleja/index.htm will countersteer like a two
wheeler, and you could build an HPV using the same principles.

Some one who reads German might be able to tell whether this does:
http://www.cx500c.de/cx_artikel/1984_02_motorrad.htm

Simon Brooke said:

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

Quoted message said:

I suggest you try riding a bicycle. You will find that if you lean

the

Quoted message said:

bicycle to one side, it will turn to that side, without any need for
any other steering input. If you lean your body to one side, thus
moving your centre of gravity, then the bike will naturally lean to

the

Quoted message said:

other side, and thus you can easily initiate a turn in either
direction. You can demonstrate this easily by holding the bike by the
back of the saddle and pushing it along at walking pace; the bike is
easy to control just by leaning it. Or just ride no hands.

You should read David Jones paper on the Unrideable Bicycle (_The
Stability of the Bicycle_, Physics Today 23, 34-36); you would find

it

Quoted message said:

instructive. There's a PDF on the net somewhere but I've lost the

link.

The paper is concerned with the stability of the bicycle, and at least
lays the gyroscopic theory to rest, but does not appear to address the
issue of how a controlled turn is initiated. I don't think
counter-steering is even mentioned.

Certainly counter-steering can be used to initiate a turn. Try the
experiment of riding no-hands and giving one side or other of the bars
a gentle push forwards. The bike will lean to the pushed side and the
bars will turn against the push, entering a smooth turn. I am not
convinced, however, that this is the mechanism by which I normally
enter a turn. I feel as though the turn happens by itself and I just
control its magnitude.

Here's an alternative idea which may explain Jones' finding that a very
stable bike is difficult to ride, and why racers prefer bikes that are
less stable, or "twitchier", than utility riders would enjoy. As we
ride along we are all the time making minute corrections as the bike
begins to fall one way or the other. We must be doing this or riding
no-hands would be just as easy as hands-on. These corrections are in
the intuitive direction - the bars are turned towards the direction of
lean - and small and quick enough to take place at a subliminal level,
much like the corrections we constantly make in order to stand upright,
for example.

Now, when we wish to turn in one direction we simply stop correcting
when the bicycle naturally starts to fall that way, or over-correct
when it starts to fall the wrong way. When the turn has become as steep
as we wish we correct to stop it increasing further. To exit the turn
we correct some more. Everything is intuitive and we are not aware of
any action on our part to initiate the turn. Learning to ride a bike is
a process of training the nervous system to associate the appropriate
movements with correcting the imbalance. Very like walking, the time
this process takes varies from one individual to another, but once
complete is permanent. It's a truism that you never forget how to ride
a bike.

This also explains why it is so difficult to make a sudden turn. You
cannot turn by the normal process any sooner or any more rapidly than
the bike would naturally have fallen anyway. You can, however, rapidly
initiate a steep turn by counter-steering. This can be learned and
performed consciously but is not intuitive.
That's my theory at any rate.

--
Dave...

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]

R.

[1] FCVO "impossible".

Simon Brooke said:

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

Quoted message said:

Quoted message said:

Now, back to the cyclist. Assume this time he is not a circus
performer. How does he apply sufficient torque to himself to move
himself bodily from one side to the other of the contact patch. If

you

Quoted message said:

Quoted message said:

believe he can do this, do you also believe he can ride a bicycle

with

Quoted message said:

Quoted message said:

the forks locked straight ahead? If not, why not? Surely the same
"adjust your balance annd carry on normally" trick should work
there too, shouldn't it?

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.

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.

--
Dave...

in message <[email hidden]>,

dkahn400 (') said:

Simon Brooke said:

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

Quoted message said:

Quoted message said:

Now, back to the cyclist. Assume this time he is not a circus
performer. How does he apply sufficient torque to himself to move
himself bodily from one side to the other of the contact patch. If

you

Quoted message said:

Quoted message said:

believe he can do this, do you also believe he can ride a bicycle

with

Quoted message said:

Quoted message said:

the forks locked straight ahead? If not, why not? Surely the same
"adjust your balance annd carry on normally" trick should work
there too, shouldn't it?

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.

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

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
-----BEGIN GEEK CODE BLOCK-----
Version: 3.1
GP/CS s++: a+ C+++ ULBVCS*++++$ L+++ P--- E+>++ W+++ N++ K w--(---)
M- !d- PS++ PE-- Y+ PGP !t 5? X+ !R b++ !DI D G- e++ h*(-) r++ y+++
------END GEEK CODE BLOCK------

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

David Martin said:

the.Mark said:

It's not just manhole covers that can be dangerous when damp,
white lines can be too. I came off last week when I crossed
the white line marking out a bus lane. Luckily I ended up
with just a bruised knee.

How did you fall off the windcheetah? or were you too used to
the extra stability of three wheels?

It's risk compensation you know...

..d

The roads are too mucky for the windcheetah. :-(
I was on the MTB and I was changing lanes to overtake all the cars in the
bus lane. I was hardly moving when my front wheel crossed the white line and
just dissappeared from under me.

I was wondering what the bus lanes were for if the cars just use them when
they feel like it. Tonight I saw a police car following all the other
drivers into it like they were sheep.
--
Mark

1x1 wheel, 3x2 wheels & 1x3 wheels.

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.

the.Mark said:

I was wondering what the bus lanes were for if the cars just use them
when they feel like it. Tonight I saw a police car following all the
other drivers into it like they were sheep.

On the way home last night, after 7 pm when most of the bus lanes revert to
being unbus lanes, /no-one/ was using them except cyclists and buses. I'm
just a primitive creature of the heath, so excuse my savage ignorance, but
how do people with that level of inability to read basic road signs manage
to get driving licences?

--

Dave Larrington - http://www.legslarry.beerdrinkers.co.uk/
World Domination?
Just find a world that's into that kind of thing, then chain to the
floor and walk up and down on it in high heels. (Mr. Sunshine)

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/