'Backwards' bikes

In article <[email hidden]>, Mark T
pleasegivegenerously@warmail*turn_up_the_heat_to_reply*.com.invalid
says...

Quoted message said:

Rob Morley writtificated

Quoted message said:

Quoted message said:

The counter steer is simply a means of shifting the centre of
gravity. Armchair theorists will say that this can be achieved only
by counter steering, but this is easily achieved without it.

So how do you propose to overcome Newton's third law?

The trick is to lean the bike first, then follow with the body.

Here's what happens in that situation if the steering isn't locked. Say
the bike leans to the left, rider to the right - the bike will steer
into the lean, leaving the rider behind, but in doing so it will soon
lean and steer to the right, thus catching up with the toppling rider
(assuming the bikes going fast enough to catch him before he's gone too
far). That's countersteering - steer the bike one way, either with the
bars or by shifting body mass and it will end up leaning/steering the
other way.

Quoted message said:

Riding no handed (or even handed) is a bit different 'cos the bike will
automatically make small movements of the front wheel as you shift your
weight. AFAIK this is essential to ride any distance.

Given the problems of riding with the steering 'locked', to test it you'd
need a steep ramp/hill and someone elses bike with the headset wrecked or
steering welded in position.

No need, just reverse the stem and clamp it to the frame - a couple of
bits of 4x2 and a couple of G clamps should do it. Or use a short stem
and straight bars, strap one end of the bars to the top tube.

Quoted message said:

Get a push off down the ramp then half way
down someone shouts 'right' or 'left'. The rider then has to shift the
centre of gravity of bike+rider to that side i.e. fall off to the side
chosen.

Tell me when you're coming over and I'll sort out a bike and a hill.
:-)

In article <74fa7f4c-8145-43c9-b8b4-
[email hidden]>, [email hidden]
[email hidden] says...

Quoted message said:

Anyone who thinks they can simply lean from side to side at
will should try riding a bike with a locked headset - just overtighten
it and ride no-hands, it's a 2 minute job to try and you have nothing
to lose apart from your dignity and erroneous beliefs.

And what might have been a perfectly good headset.

In article <74fa7f4c-8145-43c9-b8b4-
[email hidden]>, [email hidden]
[email hidden] says...

Quoted message said:

Anyone who thinks they can simply lean from side to side at
will should try riding a bike with a locked headset - just overtighten
it and ride no-hands, it's a 2 minute job to try and you have nothing
to lose apart from your dignity and erroneous beliefs.

And what might have been a perfectly good headset.

Rob Morley said:

In article <74fa7f4c-8145-43c9-b8b4-
[email hidden]>, [email hidden]
[email hidden] says...

Quoted message said:

Anyone who thinks they can simply lean from side to side at
will should try riding a bike with a locked headset - just overtighten
it and ride no-hands, it's a 2 minute job to try and you have nothing
to lose apart from your dignity and erroneous beliefs.

And what might have been a perfectly good headset.

?

Overtightening it a bit won't do any harm - it only has to be enough
to stop the steerer turning freely, at least if you try riding no
hands.

James

PhilD said:

You can.  Or at least, I can.  It can be quite difficult working up
much movement, but by carefully adjusting your weight it is possible.

Starting from scratch on a swing appears at first sight to violate
Newton's laws of motion. Of course it doesn't really. There is a
substantial reaction force from the ground. See <http://
groups.google.com/group/uk.rec.cycling/msg/d8b2e2b060233156>.

--
Dave...

On Mar 5, 9:59 am, Mark T
<pleasegivegenerously@warmail*turn_up_the_heat_to_reply*.com.invalid>

Quoted message said:

Rob Morley writtificated

Quoted message said:

Quoted message said:

So how do you propose to overcome Newton's third law?

The trick is to lean the bike first, then follow with the body.

Riding no handed (or even handed) is a bit different 'cos the bike will
automatically make small movements of the front wheel as you shift your
weight.  AFAIK this is essential to ride any distance.

Given the problems of riding with the steering 'locked', to test it you'd
need a steep ramp/hill and someone elses bike with the headset wrecked or
steering welded in position.  Get a push off down the ramp then half way
down someone shouts 'right' or 'left'.  The rider then has to shift the
centre of gravity of bike+rider to that side i.e. fall off to the side
chosen.

There speaks a man who has not done the experiment. Firstly you do not
have to wreck the headset to tighten it sufficiently to lock the
steering. Secondly you would be very unlikely to get as far as halfway
down the ramp. Being unable to get a reaction force from the ground
you would fall almost immediately.

An easier way to perform the experiment with locked steering is to get
someone to hold you at the point of balance then tip you just enough
to start you falling either way. Once you have started to tip it is
impossible to recover.

The tip-the-bike-first-then-follow-with-the-body idea is a delusion.
As you tip the bike to the left the body moves to the right. When you
try to follow with the body the bike simply comes upright again. The
bike and the rider's body have a common centre of gravity, and it's
leftness and rightness are not affected by your movements. When it
gets to one side or other of the line joining the centres of the
tyres' contact patches it is virtually impossible to recover without
using the steering. By extreme gymnastic movements it may be possible
to get sufficient reaction force from the ground, but I don't think
this is the sort of movement you have in mind.

--
Dave...

In article <d6c3926c-84fe-4405-a574-8818663e7f96
@s19g2000prg.googlegroups.com>, [email hidden]
[email hidden] says...

Quoted message said:

Rob Morley said:

In article <74fa7f4c-8145-43c9-b8b4-
[email hidden]>, [email hidden]
[email hidden] says...

Quoted message said:

Anyone who thinks they can simply lean from side to side at
will should try riding a bike with a locked headset - just overtighten
it and ride no-hands, it's a 2 minute job to try and you have nothing
to lose apart from your dignity and erroneous beliefs.

And what might have been a perfectly good headset.

?

Overtightening it a bit won't do any harm - it only has to be enough
to stop the steerer turning freely, at least if you try riding no
hands.

You said 'locked', not just a bit stiff.

Peter Clinch said:

Rob Morley wrote:

Quoted message said:

Quoted message said:

So how do you propose to overcome Newton's third law?

I could just lean over... one can steer a bike while riding no-handed,
after all, and quite how one is supposed to "counter steer" a unicycle
is a bit of a poser, but they /do/ go around bends.

Unicycles also work by counter steering and do not violate Newton's
laws any more than bicycles do. You don't have handlebars but that
does not prevent you from rotating the whole thing, including
yourself, about your vertical axis. With a uni you also have the
counter steering effect in a forwards and backwards direction of
course. You use a combination of rotation and forwards and backwards
pedalling to keep the tyre's contact patch directly below your centre
of gravity.

--
Dave...

Rob Morley writtificated

Quoted message said:

Tell me when you're coming over and I'll sort out a bike and a hill.
:-)

If you're local to Manchester send me an email.

dkahn400 writtificated

Quoted message said:

There speaks a man who has not done the experiment. Firstly you do not
have to wreck the headset to tighten it sufficiently to lock the
steering.

From experience, yes you do. I'm guessing you're using a different
definition of 'sufficiently'. I couldn't get the steering locked out
sufficiently and still damaged the headset.

Quoted message said:

Secondly you would be very unlikely to get as far as halfway
down the ramp. Being unable to get a reaction force from the ground
you would fall almost immediately.

This is likely to be the biggest problem. IMO countersteering is
essential to keep balanced and upright

Quoted message said:

An easier way to perform the experiment with locked steering is to get
someone to hold you at the point of balance then tip you just enough
to start you falling either way. Once you have started to tip it is
impossible to recover.

This would likely be an inconclusive test - it tests the riders ability
to regain balance without countersteer rather than to *lose* balance.
Losing balance is a lot easier than re-gaining it![1]

Quoted message said:

The tip-the-bike-first-then-follow-with-the-body idea is a delusion.
As you tip the bike to the left the body moves to the right. When you
try to follow with the body the bike simply comes upright again. The
bike and the rider's body have a common centre of gravity, and it's
leftness and rightness are not affected by your movements. When it
gets to one side or other of the line joining the centres of the
tyres' contact patches it is virtually impossible to recover without
using the steering.

You think it's a delusion, I've got the smug satisfaction of knowing
you're wrong :-P

Quoted message said:

By extreme gymnastic movements it may be possible
to get sufficient reaction force from the ground, but I don't think
this is the sort of movement you have in mind.

The exact method is to stand on the pedals, lean bike over and then move
body over, so you're right in that - no extreme gymnastic movements
involved.

That said, in wheel life countersteering is so easy, quick (and
impossible to eradicate) that it's almost impossible not to use it to
initiate a lean. Sidewinds etc will do it, but not even the P*ncture
Fairy herself has influence over the flatulance of the Wind God.

[1] In my experiments I tried to make sure I regained balance then went
over the other side, but the lost-balance 'envelope' is very thin.

In article <[email hidden]>, Mark T
pleasegivegenerously@warmail*turn_up_the_heat_to_reply*.com.invalid
says...

Quoted message said:

Rob Morley writtificated

Quoted message said:

Tell me when you're coming over and I'll sort out a bike and a hill.
:-)

If you're local to Manchester send me an email.

I'm at least 5 junctions down the M6, so not really local.

dkahn400 said:

Unicycles also work by counter steering and do not violate Newton's
laws any more than bicycles do. <snip>

Thinking further, though one can argue about the terminology and what
constitutes "the steering", I think you've got it right, and I had it wrong.

A uni is actually a poorer limiting case than I first thought, as
locking steering on a bike will have the trailing wheel prevent you from
rolling on a curve like a rolled coin does.

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

dkahn400 wrote on 05/03/2008 15:21:

Quoted message said:

Quoted message said:

Quoted message said:

So how do you propose to overcome Newton's third law?

I could just lean over... one can steer a bike while riding no-handed,
after all, and quite how one is supposed to "counter steer" a unicycle
is a bit of a poser, but they /do/ go around bends.

Unicycles also work by counter steering and do not violate Newton's
laws any more than bicycles do. You don't have handlebars but that
does not prevent you from rotating the whole thing, including
yourself, about your vertical axis. With a uni you also have the
counter steering effect in a forwards and backwards direction of
course. You use a combination of rotation and forwards and backwards
pedalling to keep the tyre's contact patch directly below your centre
of gravity.

I was pondering something related(ish) the other day. A colleague was
idly standing on our pallet/pump truck (as you do) (like
http://www.pallettrucksandscissorlifts.co.uk/product-images/Full-SS-Pallet-Truck.jpg
) astride it, hand on the handle, feet on the arms. He then rotated the
'front' wheels attached to the handle left and right, left and right,
and caused the truck to edge forward. It was all fascinating and I'm
still not sure I've got my head round it from a physics point of view. I
probably should have...

Peter

--
http://www.scandrett.net/lx/
http://www.scandrett.net/bike/

Quoted message said:

The correct answer is that it may be just about technically possible
to lean without countersteer, but it's difficult enough to do in a
controlled manner that it doesn't play a significant role in normal
cycling. Anyone who thinks they can simply lean from side to side at
will should try riding a bike with a locked headset - just overtighten
it and ride no-hands, it's a 2 minute job to try and you have nothing
to lose apart from your dignity and erroneous beliefs.

My bike is desperately in need of new headset bearings (and possibly a
new headset, I'll make a decision when I dismantle it on Friday
evening). For the last week or so the steering has had a definite
notchy feel, with the handlebar sitting very comfortably in the straight
ahead position and being reluctant to move in either direction. The
effect on steering is very noticeable - even if I'm not conscious of
countersteering, I'm obviously having to overcome that notchiness in
order to induce a steering lean.

On the subject of unicycles, I'm conscious of using 3 steering techniques.

At low speeds I twist my upper body smoothly away from the direction
that I want to turn, then jerk it round in the direction that I want to
turn. As I jerk my upper body round my legs and wheel follow, changing
the direction in which the wheel is pointing.

At low speeds when I'm holding a hockey stick (typically when warming up
for hockey, or when changing direction in goal) I'll put my stick on the
floor at the point that is to be the centre of my turn and then pivot
round it.

At high speeds I lean. I lean enough that I changed the cranks on my
20" hockey unicycle from 125mm to 114mm and then to 102mm, specifically
to stop me grounding the pedals in tight turns. I'm not conscious of
countersteering, I can't see that countersteering would be necessary to
induce lean on a unicycle, and the fact that I can make tight high-speed
turns while holding a hockey stick without losing control of the ball
suggests that I'm not twisting my upper body significantly. But I still
wouldn't completely rule out the possibility of countersteer.

These are the best pictures I could find of people leaning into turns:
http://www.redpedals.co.uk/temp/z-hockey1.jpg
http://www.redpedals.co.uk/temp/z-hockey2.jpg

In this one the chap on the right looks like there might be some
countersteering going on:
http://www.redpedals.co.uk/temp/z-hockey3.jpg

I noticed the same sort of position in several of the photos that I
looked at. I'm not entirely sure what's going on there, but it looks
like it's usually someone who has just whacked the ball. I think it's
probably a useful position for maintaining balance while putting power
behind a shot.

--
Danny Colyer <http://www.redpedals.co.uk>
Reply address is valid, but that on my website is checked more often
"The plural of anecdote is not data" - Frank Kotsonis

dkahn400 said:

Peter Clinch said:

Rob Morley said:

So how do you propose to overcome Newton's third law?

Quoted message said:

I could just lean over... one can steer a bike while riding no-handed,
after all, and quite how one is supposed to "counter steer" a unicycle
is a bit of a poser, but they /do/ go around bends.

Unicycles also work by counter steering and do not violate Newton's
laws any more than bicycles do. You don't have handlebars but that
does not prevent you from rotating the whole thing, including
yourself, about your vertical axis.

Technically I think what generally happens is that you turn your lower
body one way and upper body the other (holding the arms somewhat
outstretched increases the moment of inertia of the upper body, making
this easier). (Rotating the whole thing one way seems a violation of
conservation of momentum, just like suddenly deciding to lean one way
on a bicycle.) Then the wheel is at an angle to the general direction
of motion, and thus rolls out from under the cyclist just as on a
bicycle where the handlebars are turned by hand or by tipping the bike
to one side. Unicycling generally seems to consist of a rather zig-zag
process, at least among more moderate riders (for highly skilled one
the effect is still there, but smaller).

But I'm not a unicyclist, this is just from observation (and some
understanding of the basic mechanics).

James

In article <b8521e52-1c00-4db9-8769-b99e543ee940
@s37g2000prg.googlegroups.com>, dkahn400
[email hidden] says...

Quoted message said:

The tip-the-bike-first-then-follow-with-the-body idea is a delusion.
As you tip the bike to the left the body moves to the right. When you
try to follow with the body the bike simply comes upright again. The
bike and the rider's body have a common centre of gravity, and it's
leftness and rightness are not affected by your movements.

Actually they are slightly - because of the radius of the tyres, the
contact points move in the direction of bike lean.
Didn't we arrive at that conclusion last time, too?

Danny Colyer said:

At high speeds I lean. I lean enough that I changed the cranks on my
20" hockey unicycle from 125mm to 114mm and then to 102mm, specifically
to stop me grounding the pedals in tight turns. I'm not conscious of
countersteering, I can't see that countersteering would be necessary to
induce lean on a unicycle, and the fact that I can make tight high-speed
turns while holding a hockey stick without losing control of the ball
suggests that I'm not twisting my upper body significantly. But I still
wouldn't completely rule out the possibility of countersteer.

It occurred to me yesterday that the Unicycle is a poor comparison
point, however, because when it's leaned the axis of rotation is free to
swing, while on a bike with locked steering the rear wheel would prevent
the axis from swinging. You'd creep sideways a little with a leaned,
locked bike as the curvature of the wheel "climbed" the bike a little,
but it wouldn't really swing like a leaning uni, which will turn corners
like a rolling coin a little off true.

I'm not convinced it needs to be counter-steered to get it doing that,
but what I am increasingly sure of is it's not actually relevant to the
case of a bike!

Pete.
--
Peter Clinch Medical Physics IT Officer
Tel 44 1382 660111 ext. 33637 Univ. of Dundee, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net [email hidden] http://www.dundee.ac.uk/~pjclinch/

Peter Clinch said:

I'm not convinced it needs to be counter-steered to get it doing that,
but what I am increasingly sure of is it's not actually relevant to the
case of a bike!

That doesn't make it any less interesting a subject for discussion, IMO.

--
Danny Colyer <http://www.redpedals.co.uk>
Reply address is valid, but that on my website is checked more often
"The plural of anecdote is not data" - Frank Kotsonis

Quoted message said:

Technically I think what generally happens is that you turn your lower
body one way and upper body the other (holding the arms somewhat
outstretched increases the moment of inertia of the upper body, making
this easier). (Rotating the whole thing one way seems a violation of
conservation of momentum, just like suddenly deciding to lean one way
on a bicycle.) Then the wheel is at an angle to the general direction
of motion, and thus rolls out from under the cyclist just as on a
bicycle where the handlebars are turned by hand or by tipping the bike
to one side.

It's so long since I've ridden with arms outstretched (other than when
playing aeroplanes) that I really can't remember from experience whether
it helps with turning. I think it makes turning significantly harder,
as it slows down the speed with which the upper body can be jerked round
in order to drag the wheel round (as described in my PP).

Quoted message said:

Unicycling generally seems to consist of a rather zig-zag
process, at least among more moderate riders (for highly skilled one
the effect is still there, but smaller).

Each downstroke of a pedal causes the wheel to lean and hence to turn
towards that side. That's why you get the zig-zagging. Experienced
riders learn to minimise this effect.

Having thought more about this overnight I think this effect is probably
very important in turning, particularly at speed. As a downstroke
causes the unicycle to lean in one direction, we move the body to
enhance that lean rather than to counteract it. All tight turns seem to
be done on the downstroke of the pedal on the side that I'm turning
towards. A shallower turn is often actually a succession of small turns
done on the downstroke.

BTW, I think I've figured out what's going on in this picture:
http://www.redpedals.co.uk/temp/z-hockey3.jpg

I think the camera has captured the rider at the point of straightening
up after a turn. He has moved his trunk to an upright position and
beyond, and is about to use a flick of the hips to pull the unicycle
into line.

--
Danny Colyer <http://www.redpedals.co.uk>
Reply address is valid, but that on my website is checked more often
"The plural of anecdote is not data" - Frank Kotsonis

Rob Morley said:

In article <b8521e52-1c00-4db9-8769-b99e543ee940
@s37g2000prg.googlegroups.com>, dkahn400
[email hidden] says...

Quoted message said:

The tip-the-bike-first-then-follow-with-the-body idea is a delusion.
As you tip the bike to the left the body moves to the right. When you
try to follow with the body the bike simply comes upright again. The
bike and the rider's body have a common centre of gravity, and it's
leftness and rightness are not affected by your movements.

Actually they are slightly - because of the radius of the tyres, the
contact points move in the direction of bike lean.
Didn't we arrive at that conclusion last time, too?

Yes, you are correct.

--
Dave...