When to Stop Pedalling?

you know? said:

That's the recommended way: no training wheels. Take the pedals off,

I think they would have helped me, if used responsibly (ie, moved up as soon as possible plus
removed soon after). I had a lot of trouble with balance at first. Fine motor skills in general
(were) not so hot.

Jasper

[email hidden] (Pbwalther) wrote in message
news:<[email hidden]>...

Quoted message said:

Dunkirk Spirit? You lost me on that one. Dunkirk was where the English Army and part of the French
army abandoned the fight in France and fled to England. They cleverly declared this a "victory".
So are they all abandoning France?

I believe this refers to the spirit and bravery of the ordinary English citizens who performed a
daring rescue operation by taking small boats across the Channel and picking up the retreating
soldiers on the beach.

In article <[email hidden]>, [email hidden] says...

...

Quoted message said:

Now if you claim that somebody can balance in place with the handlebars pointing dead ahead, then
you ARE talking about something different...

That is exactly what I'm talking about, and I've only seen one person outside the circus who
could do it.

--
Dave Kerber Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

In article <[email hidden]>, [email hidden] says...

Quoted message said:

archer ns_archer1960@ns_hotmail.com said:

In a track stand, they pressure the pedals forwards and backwards, working with the steering to
hold the bike in _nearly_ one place. I'm talking about something like a tightrope walker standing
in place on the high wire, where there is no fore-and-aft motion involved at all.

A tightrope walker doesn't stay in one place, he balances by shifting his weight from side to
side. It's just like standing on two feet in the first place, except you mostly lose the ability
to correct by using muscles to move the position of your foot, plus your contact patch is much
smaller so if you get too far out of whack you'll have a very hard time correcting.

I'll bet his contact patch is about the size of a MTB tire's contact patch...

--
Dave Kerber Fight spam: remove the ns_ from the return address before replying!

REAL programmers write self-modifying code.

David Kerber said:

Quoted message said:

Now if you claim that somebody can balance in place with the handlebars pointing dead ahead, then
you ARE talking about something different...

Quoted message said:

That is exactly what I'm talking about, and I've only seen one person outside the circus who
could do it.

I had the pleasure of seeing Cino Cinelli, a man of 5'4" or so, in business suit, pant legs inverted
over knees, sit motionless on my 26" fame bicycle with his arms folded over his chest, front wheel
straight ahead. It can be done.

For those who have access to it, the movie with Joe E Brown in "The Six-Day Bike Rider" can see him
perform all sorts of tricks that were popular in the heyday of bicycling in the 1930's.

movies.go.comCreditsOpen ↗

Jobst Brandt [email hidden] Palo Alto CA

Archer said:

Nice article! Did you just write this, or had you done it before? I particularly like your idea
about the "science of bicycling" class for schools!

Thank you! No, it wasn't written beforehand. I didn't feel like working this morning; so I
decided to type. Writing does the same thing for my brain that a stationary bike does for a body:
I don't actually get anywhere; but it's good excercise just the same.

Quoted message said:

An optimist says "Good morning, Lord." While a pessimist says "Good Lord, it's morning".

My favorite version is: An optimist thinks the glass is half full. A pessimist thinks the glass
is half empty. And an engineer thinks the glass is twice as big as it needs to be.

Pardon me for posting out of thread order. My ISP is in a bad mood, and I only see about
half of what's posted. I've been using Google to keep up, and I'm hoping things will be
fixed by tomorrow.

KG

Pbwalther said:

Quoted message said:

When was this? The freewheel was one of the earliest inventions after the chain driven Rover
bicycle was introduced by Starley.

My grandfather made decent money racing bikes in the first decade of the 20th century and he
always rode a fixed gear. I believe that fixed gears were used in competition until the mid 1920s
but I am not an expert on this one. I must confess that the talking about descending with feet out
of the pedals is taken from accounts or high wheel riders doing this on descents and I figured
that some diamond frame fixed gear riders must have done it also.

My Dad raced on a fixed gear bike in Alberta in the 30's. His bike was built in Belgium. The big
races were from Drumheller to Edmonton, and Red Deer to Edmonton, I believe. No small thing on a
single fixed gear. Regards, Bernie

In article <[email hidden]>, [email hidden]

(Prometheus) said:

Leave the Engineer to decipher it all!

Are you sure?

Quoted message said:

The high-speed stability of a bike comes from its traction. At high rotational speeds, the
majority of a tire's tractive force (actually a frictional force) is involved in merely keeping
the tire rotating. If you were to try to impart any lateral force(as is done by a turning of the
handlebars), its effect would be greatly reduced. The same is true in your car. High speed
cornering requires a much larger turning radius than at low speeds, because you have less
avaliable(unused) traction. So, yes, a bike is more stable at high speeds, but for the same reason
a car has less maneuverability at high speeds.

This is, to paraphrase Pauli, not even wrong.

The high-speed stability of a bicycle--assuming the bicycle's geometry is stable--is largely a
matter of its momentum, not its traction. It resists changes in direction in proportion to its mass
and speed.

At high speeds, attempting to corner requires a greater force because you're trying to resist a
greater amount of inertia.

A useful example might be to consider a frictionless object like a spaceship (close enough). If it
is moving, you can get it to change direction by applying a force. The faster it is moving, or the
faster you want it to change direction, or the heavier it is, the more force required to change its
direction, and the less time you get to apply it (F=ma, the force here must be enough to counter the
object's m and get the desired a, which in this case is a handy way of describing how quickly you
want the object to change direction, since acceleration describes rates of changes in vector, not
just speed).

On a bicycle you have to use tire traction to impart these forces. That is, you can't let the tire
traction be overcome by the direction-changing forces you are essentially driving through the tire.
Exceed the tire's ability to resist this force, and you slide. Since the tire's coefficient of
friction doesn't change appreciably at speed, and you don't change your mass appreciably at speed
(assuming a cyclist, and not that spaceship I had earlier), the maximum amount of F you can push
into the system at any moment is constant. The higher acceleration required to counter the greater
inertia at higher velocities essentially means it takes more distance to make the same change of
direction (because you can't make it any faster than you can at slow speeds), and more distance
equals bigger turning circles.

In other words, the faster you go, the more room you need to change direction, unless you can absorb
a greater amount of force at any instant, which you can't on a bicycle.

Ryan Cousineau, BA (English), SFU.
--
Ryan Cousineau, [email hidden] sfu.ca~rcousineOpen ↗ President, Fabrizio Mazzoleni Fan Club

In article <[email hidden]>,

Kirk Gordon said:

Quoted message said:

Kirk Gordon said:

The wheels on a bicycle ARE gyroscopes, and stabilize the bike EXACTLY the way that any gyro
will stabilize anything it's attached to.

Quoted message said:

The physics of gyroscopes was established as fact over a hundred years ago. It's well tested,
well understood, and is relied on daily for things as diverse as navigation systems in ships
and aircraft, Segway scooters, and kids' toys. You can buy a simple but fully functional
gyroscope at any good toy store for a couple dollars. Pick one up some time and play with it.
You might be surprised.

I think Jobst knows about gyroscopes. There is, however, a question of how much momentum these
particular gyroscopes (to wit, bicycle wheels) have.

Quoted message said:

Quoted message said:

This is a spoof, isn't it?

No. Just an attempt to be helpful, from someone who's studied physics, who makes his living as
an engineer, and who's spent decades designing and building mechanical things like industrial
machinery. I don't mean to sound arrogant, or to imply that I know any more than I really do;
but some things are so basic, and so fundamental to the way that mechanical stuff works, that
ignoring them can only lead to serious mistakes and misunderstandings.

Kirk: you're an engineer, so you know these equations:

physicslessons.comequations.htmOpen ↗

Pick a wheelset, any wheelset:

geocities.comweight.htmlOpen ↗

Do us all a favour and calculate the angular momentum of the wheelset of your choice at the speed of
your choice. Reasonable assumptions about the weight distribution within the wheel for the purposes
of calculating this are allowable, but please show your work. Then discuss how this momentum
compares to the momentum of a reasonable bicycle and rider at the chosen speed.

I am Spartacus! No, wait, that should be "I am Socrates!"
--
Ryan Cousineau, [email hidden] sfu.ca~rcousineOpen ↗ President, Fabrizio Mazzoleni Fan Club

Ryan Cousineau said:

A useful example might be to consider a frictionless object like a spaceship (close enough). If it
is moving, you can get it to change direction by applying a force. The faster it is moving, or the
faster you want it to change direction, or the heavier it is, the more force required to change
its direction, and the less time you get to apply it (F=ma, the force here must be enough to
counter the object's m and get the desired a, which in this case is a handy way of describing how
quickly you want the object to change direction, since acceleration describes rates of changes in
vector, not just speed).

Mostly correct, except that you don't necessarily have to increase the force (with mass, velocity,
etc). It is the time integral of force (impulse) that must be increased. A large force in a small
time or a small force in a large time will do the trick.

Joe Riel

In article said:

The high-speed stability of a bicycle--assuming the bicycle's geometry is stable--is largely a
matter of its momentum, not its traction. It resists changes in direction in proportion to its
mass and speed.

Pardon me, but isn't that the situation for all objects in motion?

Tim "The faster you go, the rounder you get" McNamara

Elisa Francesca Roselli said:

That's what they all say. It may be elementary physics but it's hard to convince myself when it's
me that's catapulting. Also I'm very bad at steering ...

Just take it as fast as you are comfortable. It's OK to go slow if you don't feel safe. After you
ride enough, more speed will become more comfortable. Don't worry about it and just let that comfort
level rise on its own. I'm quite comfortable descending hills at 65-75 kph when I can find a hill
steep and long enough but I can understand not everyone being so comfortable with that; especially
if they didn't grow up riding.

Quoted message said:

I never get over how nice people are in this forum. Do bicycles accelerate human evolution or
something?

You've come here and asked good questions for a beginner to be asking and you've behaved very well
so you get that back. We were all beginners once and most of us have at least some recollection of
learning the things that you are learning now.

We do have a dark side and it can get very ugly in here. Just stay off controversial topics and try
not to pontificate and you should be safe 🙂.

--Bill Davidson

Quoted message said:

David Kerber said:

That is exactly what I'm talking about, and I've only seen one person outside the circus who
could do it.

I had the pleasure of seeing Cino Cinelli, a man of 5'4" or so, in business suit, pant legs
inverted over knees, sit motionless on my 26" fame bicycle with his arms folded over his chest,
front wheel straight ahead. It can be done.

I'm suprise he fitted! There's a similar height difference between myself (6'7"😉 and my lady (5'6"😉,
and she can't reach the bottom of the pedal arc while straddling the crossbar.

Bill Davidson said:

We do have a dark side and it can get very ugly in here. Just stay off controversial topics and
try not to pontificate and you should be safe 🙂.

And what exactly is a controvertial topic to cyclists?

(Forewarned is fore-armed).

Elisa Roselli Paris, France

In article <N2xIa.97264$MJ5.44472@fed1read03>, [email hidden] says...

...

Quoted message said:

We do have a dark side and it can get very ugly in here. Just stay off controversial topics and
try not to pontificate and you should be safe 🙂.

Pontificate!!!! Who would do that <G,D&R>?

--
David Kerber An optimist says "Good morning, Lord." While a pessimist says "Good Lord,
it's morning".

Remove the ns_ from the address before e-mailing.

Elisa Francesca Roselli said:

Bill Davidson said:

We do have a dark side and it can get very ugly in here. Just stay off controversial topics and
try not to pontificate and you should be safe 🙂.

And what exactly is a controvertial topic to cyclists?

Well.. err.. gyroscopic forces as stability for bikes, for example 😉

Jasper

In article said:

Elisa Francesca Roselli said:

Bill Davidson said:

We do have a dark side and it can get very ugly in here. Just stay off controversial topics and
try not to pontificate and you should be safe 🙂.

And what exactly is a controvertial topic to cyclists?

Um, Critical Mass, leg shaving, bike lanes, helmet usage, helmet laws, spandex, clipless pedal
preferences, Shimano, Campagnolo, steel frames, aluminum frames, carbon fibre steer tubes, quick
releases, saddles, seats, brifteurs, derailleurs, derailers, drug use in pro sport, relative effects
of weight on the frame, wheels, and rider; and Lance Armstrong.

Quoted message said:

Well.. err.. gyroscopic forces as stability for bikes, for example 😉

Is not! We've got that one solved, now!

--
Ryan Cousineau, [email hidden] sfu.ca~rcousineOpen ↗ President, Fabrizio Mazzoleni Fan Club

In article said:

Ryan Cousineau said:

A useful example might be to consider a frictionless object like a spaceship (close enough). If
it is moving, you can get it to change direction by applying a force. The faster it is moving,
or the faster you want it to change direction, or the heavier it is, the more force required to
change its direction, and the less time you get to apply it (F=ma, the force here must be enough
to counter the object's m and get the desired a, which in this case is a handy way of describing
how quickly you want the object to change direction, since acceleration describes rates of
changes in vector, not just speed).

Mostly correct, except that you don't necessarily have to increase the force (with mass, velocity,
etc). It is the time integral of force (impulse) that must be increased. A large force in a small
time or a small force in a large time will do the trick.

Joe Riel

Whoops, thanks for the correction. Pretty good for an arts major, though, eh?

I had an inkling that you could change the object's position with less force over more time, but
couldn't remember what that was, and didn't want to do the math.

--
Ryan Cousineau, [email hidden] sfu.ca~rcousineOpen ↗ President, Fabrizio Mazzoleni Fan Club

In article <[email hidden]>, Tim McNamara

Quoted message said:

In article <[email hidden]>, Ryan Cousineau

Quoted message said:

The high-speed stability of a bicycle--assuming the bicycle's geometry is stable--is largely a
matter of its momentum, not its traction. It resists changes in direction in proportion to its
mass and speed.

Pardon me, but isn't that the situation for all objects in motion?

Tim "The faster you go, the rounder you get" McNamara

Why, yes! It's one the simplest laws of the physics of objects with mass and velocity. But it points
out that bicycles do not get their stability from the gyroscopic effects of their wheels. As Jobst
as pointed out to the point he must be exhausted, there are single-track wheel-less vehicles with
similar geometries and stability to bicycles. The Ski-bike is the simple example.

Gyro effects do start coming into play if your gyros contain enough angular momentum, though. I
believe that at the scale of a motorcycle, gyro effects are significant, though I'd have to do the
math to confirm that.

--
Ryan Cousineau, [email hidden] sfu.ca~rcousineOpen ↗ President, Fabrizio Mazzoleni Fan Club

In article <[email hidden]>, [email hidden] says...

Quoted message said:

In article <[email hidden]>, Tim McNamara

Quoted message said:

In article <[email hidden]>, Ryan Cousineau <[email hidden]>

Quoted message said:

The high-speed stability of a bicycle--assuming the bicycle's geometry is stable--is largely a
matter of its momentum, not its traction. It resists changes in direction in proportion to its
mass and speed.

Pardon me, but isn't that the situation for all objects in motion?

Tim "The faster you go, the rounder you get" McNamara

Why, yes! It's one the simplest laws of the physics of objects with mass and velocity. But it
points out that bicycles do not get their stability from the gyroscopic effects of their wheels.
As Jobst as pointed out to the point he must be exhausted, there are single-track wheel-less
vehicles with similar geometries and stability to bicycles. The Ski-bike is the simple example.

Yes, but NONE of them are as stable as a bicycle at speed. I think the gyro effect helps the
stability, even though it's not the only (or maybe even the major) source.

....

--
David Kerber An optimist says "Good morning, Lord." While a pessimist says "Good Lord,
it's morning".

Remove the ns_ from the address before e-mailing.