Fell off

Carol Hague said:

David Martin said:

Carol Hague said:

You *can* lean on corners if you want to - some people swear by it,
particularly at speed. Rob managed to lose some skin off his elbow when
unwisely leaning on his SLR during the trike racing at Spezi in Germany
last year.

Picture in the latest VeloVision? (on the doorstep when I got back from
massacring innocent plants at the allotment this morning.)

Entirely possible, but ours hasn't arrived yet - the post round here is
getting veeerrryyyy slllooowww.... :-)

It's an article on short cranks, where short means really, really short.

P22 there is a pic of Rob leaning into a cobbled corner on something
that looks from the front like a tea tray on wheels and claims to be the
2004 SPEZI trike race.

...d

in message <[email hidden]>, Jon Senior

jon_AT_restlesslemon_DOT_co_DOT_uk ('') said:

JohnB said:

Loadsa tosh.
They just needs some _skill_, sadly lacking in many quarters today.

As do unicycles. The fact that it is possible to master the skillset
required does not change the fact that they are an abomination! ;-)

When I was a kid my parents had friends who used to ride around the
place on an upright tandem trike. It was one seriously fast machine!
Clearly they were skilled at riding it, but no-one on a solo bicycle
was going to stay with them uphill or down.

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

<p>Schroedinger's cat is <blink><strong>NOT</strong></blink> dead.</p>

Brian Drury said:

Tyres are Schwalbe Jets, until now I thought these were brilliant. Not so
sure now. There was no hint of losing traction, just a seemingly
instantaneous transfer from slant to horizontal. Should I blame the tyres?
This has never happened to me on slower tyres.

Having had a scary moment on City Jets today, I'm inclined to agree.
Not impressed by the grip at all. A corner had a thin layer of slurry
on it and the front wheel washed out at about 20mph. I didn't come off
but the road felt as slippery as ice. I also did an interesting
"powerslide" last week on a bumpy cycle track as I veered round a ped.

The old Vredestein S-Licks used to stick like [censored] to a blanket. I may
have to get some more (and a hub dynamo, because S-Licks are not
suitable for bottles).

Pete Biggs said:

Brian Drury wrote:
...........

Quoted message said:

Tyres are Schwalbe Jets, until now I thought these were brilliant.
Not so sure now. There was no hint of losing traction, just a
seemingly instantaneous transfer from slant to horizontal. Should I
blame the tyres? This has never happened to me on slower tyres.

Bad luck, I know exactly what that experience feels like: horrible.

An instant slip can happen with any tyres on-road if the surface is
slippery enough or you lean far enough. I wonder if the tyres were
over-inflated? The pressure stated on the City Jet sidewall is a bit
high, I reckon, especially for the front. (Front should be softer than
the rear in any case). Otherwise I wouldn't blame the tyres, got to blame
yourself or the road--could have been an oil patch, for instance.

There's a big difference between tyres because of the rubber compound
and the flexibility of the carcass. The scariest things I've ever
ridden were some Specialized kevlar tyres in 27" which were comparable
in comfort and grip to riding on the bare rims. The rubber was hard and
I suspect the kevlar stiffened up the carcass so the tyres didn't
conform to the road surface.

Generally, a tyre with a soft tread compound and a high TPI is best for
grip, although it may not last as long.

I hit a stone once when cornering hard. The front wheel jumped 6"
sideways and when it landed the tyre gripped again. That was an S-Lick.
On a bad tyre I would have gone over.

Simon Mason said:

Cornering should be done very carefully, I try to keep my bike at 90 degrees
to the road at all times and steer carefully around bends. Get well soon.

Ye cannae change the laws of physics!

For a given rate of turn, the force trying to make the tyre slide
sideways is always the same whatever the angle of the bike. It might
alter the mode of crashing if you overcook it though ;-)

Zog The Undeniable said:

There's a big difference between tyres because of the rubber compound
and the flexibility of the carcass. The scariest things I've ever
ridden were some Specialized kevlar tyres in 27" which were comparable
in comfort and grip to riding on the bare rims. The rubber was hard
and
I suspect the kevlar stiffened up the carcass so the tyres didn't
conform to the road surface.

Generally, a tyre with a soft tread compound and a high TPI is best
for grip, although it may not last as long.

I agree with all that but air pressure is still a more significant factor.
A hard-compound low-TPI Specialoozled Crapmodel will grip the road better
than a soft-compound high-TPI Victelicious Lovelyjob if it's left squidgy
enough. It just won't be as fast. 1.5" tyres don't have to be extremely
hard to be pinch-flat resistant so there is quite a lot of scope. Wear is
another factor (soft tyres, in bot senses of the term, wear faster) but of
course that's not as important as grip.

So anyone worried about the grip of City Jets should let them down a bit,
slow down, or get different tyres. I think they're good general purpose
road tyres for mountain bikes, though not the lightest and fastest.

~PB

Simon Brooke said:

In order to turn sharply, one may start by turning gently and allow the
turn to increase, rather than limiting it. Note that I'm not saying
that counter steering does not work. All I am saying is that it isn't
the only or the necessary way to initiate a turn.

But you still need to get on to the "correct" side of the wheel track in
the first place, at the right time to make the turn.

Quoted message said:

One can initiate a
turn by any means which moves the CoG away from vertically above the
track. Sudden body movements exploiting inertia do this easily - so
easily, in fact, that it's instinctive.

Can you describe such a movement, with particular reference to the
source of the external lateral force that is required to move the CoG to
one side? You might like to think of it as a torque around the wheel
contact patch since the motion can also be viewed as a rotation about
that point. (This takes the contact point out of the picture entirely.)

Quoted message said:

Well, speaking as a logician, the question of whether counter steering
is necessary _when riding no hands_ is easily resolved.

(i) Suppose it were necessary to start a turn in one direction by
counter steering, which is in effect a short turn in the other
direction.

(ii) Then in order to initiate this counter steer turn one must first
initiate a counter steer turn in the desired direction.

(iii) Then in order to initiate this counter steer turn one must first
initiate a counter steer turn against the desired direction.

(ii)

(iii)

ad infinitam, and no turn is possible at all.

Your logic is broken, I'll merely point out that the countersteering is
NOT "in effect a short turn in the other direction", it is in fact a
loss of balance in which the _bicycle_ (contact patch) moves to one side
while the _rider_ is left behind. If you did it for more than a brief
moment, you would fall off, not turn.

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:

Your logic is broken, I'll merely point out that the countersteering
is NOT "in effect a short turn in the other direction", it is in fact
a loss of balance in which the _bicycle_ (contact patch) moves to one
side while the _rider_ is left behind. If you did it for more than a
brief moment, you would fall off, not turn.

I suggest you try riding a bicycle. You will find that if you lean the
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
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
instructive. There's a PDF on the net somewhere but I've lost the link.

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

The Conservative Party is now dead. The corpse may still be
twitching, but resurrection is not an option - unless Satan
chucks them out of Hell as too objectionable even for him.

Simon Brooke said:

You should read David Jones paper on the Unrideable Bicycle (_The
Stability of the Bicycle_, Physics Today 23, 34-36); you would find it
instructive. There's a PDF on the net somewhere but I've lost the link.

http://socrates.berkeley.edu/~fajans/Teaching/MoreBikeFiles/JonesBikeBW.pdf

..... or so you posted this August.

Mike

David Martin said:

It's an article on short cranks, where short means really, really short.

P22 there is a pic of Rob leaning into a cobbled corner on something
that looks from the front like a tea tray on wheels and claims to be the
2004 SPEZI trike race.

I repeated this to Rob and he laughed and said it sounds like the SLR
all right :-)

These days, it's fully encased in coroplast, so his elbows are quite
safe :-)

--
Carol
"I was just being a little teapot. It's a bad habit of mine"
- Wyvern, Randall & Hopkirk (Deceased).

congokid said:

I wrote about coming off my Brompton just over a year ago.
Brian's 's fall sounds similar to mine, though in my case
there was wheel slippage - on some damp metal manhole covers
at the bottom of an incline.

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.
--
Mark

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

in message
<[email hidden]>, Mike

Causer (') said:

Simon Brooke said:

You should read David Jones paper on the Unrideable Bicycle (_The
Stability of the Bicycle_, Physics Today 23, 34-36); you would find
it instructive. There's a PDF on the net somewhere but I've lost the
link.

http://socrates.berkeley.edu/~fajans/Teaching/MoreBikeFiles/JonesBikeBW.pdf

Quoted message said:

.... or so you posted this August.

Thanks, yes. I knew somebody would remember.

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

my other car is #<Subr-Car: #5d480>
;; This joke is not funny in emacs.

Simon Brooke said:

Thanks, yes. I knew somebody would remember.

In truth, Google remembered for me ......

.... up till today I'd just used the report of Daedelus' findings in
D.G. Wilson's "Bicycling Science" 3rd Ed.

Mike

Simon Brooke said:

in message
<[email hidden]>, Mike

Causer (') said:

Simon Brooke said:

You should read David Jones paper on the Unrideable Bicycle (_The
Stability of the Bicycle_, Physics Today 23, 34-36); you would find
it instructive. There's a PDF on the net somewhere but I've lost the
link.

http://socrates.berkeley.edu/~fajans/Teaching/MoreBikeFiles/JonesBikeBW.pdf

Quoted message said:

.... or so you posted this August.

Thanks, yes. I knew somebody would remember.

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.

Only joking.

Simon Brooke said:

in message <[email hidden]>, James Annan

(') said:

Your logic is broken, I'll merely point out that the countersteering
is NOT "in effect a short turn in the other direction", it is in fact
a loss of balance in which the _bicycle_ (contact patch) moves to one
side while the _rider_ is left behind. If you did it for more than a
brief moment, you would fall off, not turn.

I suggest you try riding a bicycle. You will find that if you lean the
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
other side, and thus you can easily initiate a turn in either
direction.

I agree that it is possible to tip the bicycle to one side while riding
along no-hands. I suggest you consider what happens when an
intantaneously balanced rider does this. Since there is no external
lateral force (I assume from your snipping of my question on this point
that you do not dispute it) then for the bicycle to move a little to the
left, the rider's CoG must move a rather smaller distance to the right.

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"?

Quoted message said:

You should read David Jones paper on the Unrideable Bicycle (_The
Stability of the Bicycle_, Physics Today 23, 34-36); you would find it
instructive. There's a PDF on the net somewhere but I've lost the link.

You should try not to be so patronising from a position of ignorance.
You made an [censored] of yourself only a couple of weeks ago when trying to
pontificate about mathematical concepts that you did not understand. I
doubt anyone needs the lesson reinforced. I certainly don't.

I'll repeat the question from my previous email:

Quoted message said:

Quoted message said:

One can initiate a
turn by any means which moves the CoG away from vertically above the
track. Sudden body movements exploiting inertia do this easily - so
easily, in fact, that it's instinctive.

Can you describe such a movement, with particular reference to the source of the external lateral force that is required to move the CoG to one side? You might like to think of it as a torque around the wheel contact patch since the motion can also be viewed as a rotation about that point. (This takes the contact point out of the picture entirely.)

Once you accept that (for a balanced rider, eg CoG vertically above tyre
contact patch and riding straight ahead) there are no external forces
that can move the combined CoG of bike and rider to one side, it is an
immediate corollary that the only way to turn to the right, is to make
the contact patch move to the left relative to the CoG. That is all that
"countersteering" means.

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 said:

Once you accept that (for a balanced rider, eg CoG vertically above tyre
contact patch and riding straight ahead) there are no external forces
that can move the combined CoG of bike and rider to one side, it is an
immediate corollary that the only way to turn to the right, is to make
the contact patch move to the left relative to the CoG. That is all that
"countersteering" means.

I'm sure that I will regret getting involved in this one but...

Can't the balanced rider just lean from the hips. I'm writing this while
leaning slightly to the right in my chair (In fact, I look a prat
because I'm concentrating on the screen while randomly leaning from side
to side). I see no reason why this cannot be done on a bike and it would
then move the CoG away from the contact patch.

Jon

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

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.

Given the ominous creaks from Igor's back wheel, I think even the spokes
are arguing about that one.

Must threaten it with a spoke key..

...d

in message <[email hidden]>, James Annan

(') said:

Simon Brooke said:

in message <[email hidden]>, James Annan

(') said:

Your logic is broken, I'll merely point out that the countersteering
is NOT "in effect a short turn in the other direction", it is in fact
a loss of balance in which the _bicycle_ (contact patch) moves to one
side while the _rider_ is left behind. If you did it for more than a
brief moment, you would fall off, not turn.

I suggest you try riding a bicycle. You will find that if you lean
the 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 other side, and thus you can easily initiate a turn in either
direction.

I agree that it is possible to tip the bicycle to one side while
riding along no-hands. I suggest you consider what happens when an
intantaneously balanced rider does this. Since there is no external
lateral force (I assume from your snipping of my question on this
point that you do not dispute it) then for the bicycle to move a
little to the left, the rider's CoG must move a rather smaller
distance to the right.

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:

Quoted message said:

You should read David Jones paper on the Unrideable Bicycle (_The
Stability of the Bicycle_, Physics Today 23, 34-36); you would find
it instructive. There's a PDF on the net somewhere but I've lost the
link.

You should try not to be so patronising from a position of ignorance.

And he himself has said it, so it must be to his credit...

Quoted message said:

I'll repeat the question from my previous email:

Quoted message said:

Quoted message said:

One can initiate a
turn by any means which moves the CoG away from vertically above the
track. Sudden body movements exploiting inertia do this easily - so
easily, in fact, that it's instinctive.

Can you describe such a movement, with particular reference to the
source of the external lateral force that is required to move the CoG
to one side? You might like to think of it as a torque around the
wheel contact patch since the motion can also be viewed as a rotation
about that point. (This takes the contact point out of the picture
entirely.)

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?

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/
Ye hypocrites! are these your pranks? To murder men and give God thanks?
Desist, for shame! Proceed no further: God won't accept your thanks for
murther
-- Roburt Burns, 'Thanksgiving For a National Victory'

in message <[email hidden]>, Jon Senior

jon_AT_restlesslemon_DOT_co_DOT_uk ('') said:

James Annan said:

Once you accept that (for a balanced rider, eg CoG vertically above
tyre contact patch and riding straight ahead) there are no external
forces that can move the combined CoG of bike and rider to one side,
it is an immediate corollary that the only way to turn to the right,
is to make the contact patch move to the left relative to the CoG.
That is all that "countersteering" means.

I'm sure that I will regret getting involved in this one but...

Can't the balanced rider just lean from the hips. I'm writing this
while leaning slightly to the right in my chair (In fact, I look a
prat because I'm concentrating on the screen while randomly leaning
from side to side). I see no reason why this cannot be done on a bike
and it would then move the CoG away from the contact patch.

Err, no it wouldn't. James is right about that. Provided it is done
slowly and smoothly, as you lean left, the bike leans right, keeping
the CoG more or less in the same place WRT the track. Try it when
you're riding no hands some time: this is one method by which you can
initiate turns (and, to be honest, I don't know of any other when
riding no hands).

Imagine standing on a tightrope. If you move your upper body slowly to
the left, your hips must move right. You can do this just by standing
on a line on the floor. The reason is that your only contact with the
world is the line, and, as James rightly points out, you have no
purchase or leverage to rotate your mass around that line.

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.

However, while we're on this subject, a suggestion for James. Stand on a
line on the floor, or the edge of a plank, or some similar object, one
foot in front of the other. Stand as still as you can. After a time you
will inevitably begin to fall to one side or the other. What
instinctive body movements do you make to correct your balance?

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?

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

[ This mind intentionally left blank ]