"The Stability of the Bicycle"

"Simon Brooke" wrote in message
. uk...
"Phil Holman" writes:

This is why Jobst specified to lift the bicycle onto one's shoulder.
That way it eliminates the random steering tendency of negative
trail.
The considerations are then just gyroscopic moment and mass
imbalance.
If gyroscopic considerations are dominant then one should observe
steering in opposite directions for forward and backward rotating
wheels. Please try that.

OK, done that. My conclusions a

(i) It's extremely sensitive to angle. If the projected axis of the
head tube does not pass exactly through the contact patch, castering
effects overwhelm other effects, either forward or backward (i.e. if
you lift the back of the bike higher than the critical angle, it's
easy to walk the bike backwards; if lower than the critical angle,
it's easy to walk the bike forwards.

(ii) If the bike is held at the critical angle where the projected
axis of the head tube passes through the contact patch, it was
impossible for me to control the bike by leaning it when moving either
forwards or backwards, at least at normal walking speeds.

Once again, it's easy for me to set up the camera and take a quicktime
movie so that you can observe this for yourself, although I imagine
it's equally easy for you to get your own bike out and try it. I
suggest you do so, and report your results.

I'm thinking you have the front wheel resting on the ground. The
instruction was to have the bike resting on your shoulder with top tube
angled down just enough for the stationary front wheel to stay straight
ahead (not touching the ground). Spin the front wheel forward and lean
to the left and the steering will turn to the left under both mass
imbalance and gyroscopic effect. Now spin the wheel backwards and lean
to the left and the wheel will turn in the direction of the dominant
force. Left and it's mass imbalance, right and it's gyroscopic effect.
My result was left but I can see where a much shorter stem, regular
brake levers and a heavy front wheel could result in it turning right.

Phil Holman

wrote in message ...

[snip fascinating bicycle physics]

Once more, how does one pronounce "maths" (aloud)?

Jobst Brandt


Dear Jobst,

You dare to ask how "maths" is pronounced?

I warned you! This is not my fault . . .

Perhaps we need more polymaths here or a
field trip to Klamath's Falls?

You're following Goliath's example, Gath's
grave-filler, grimly going ignorant into
great battle.

(That's also a feeble example of Old English
verse, which favored strong alliteratve pairs
bridging an internal line gap. It leads to
chanting passages from "Beowulf.")

Nothing in Sylvia Plath's work is helpful,
but you might turn to "Jabberwocky" and watch
the mome raths outgrabe. Whatever they are,
they're not my favorite fishes, the ancient
coelacanths, whose living existence came out
after Carroll.

(Drat! Another chantable Old English line,
hack-work and hideous!)

Double-drat!)

Ah, you may quibble, there's an internal -n-
that should disqualify "coelacanths" from
this half-learned "-aths" list, lack-witted
and lengthy.

(Drat again!)

A mere internal -n- is famously of no
consequence to linguistics and etymology. The
brothers Grimm were actually more interested
in how Western languages changed than in the
fairy tales that they collected. Jakob found
predictable patterns of change, one of which
is that t's slowly became th's, which then
turned into d's:
t-- th-- d

The obvious example is how both ends of "dent-"
change as it evolves into "tooth."

That dental -n- (a linguistic pun--see what
your tongue touches when you say "dennnn-tal")
was dropped without any qualms as it turned
into "tooth" in not only Indo-European history
but also this tiny-minded treatise, tiresome and
terrible.

(Drat once more!)

An anonymous linguistic law explains the
importance of any single letter or sound when
words change. Our more coherent grunts may be
divided into two sound groups, the true consonants,
which are short and unsustainable, like -p- or -k-
or -t-, and the true vowels, which are sustainable,
like -eeeeeeee-.

(Hmmm, are there are vocalic consonants? Yesss!
There are more vowels, Horatio, than are dreamt
of in your a-e-i-o-u and sometimes y.)

The etymological rule of thumb is that
consonants count for very little when words
slowly change, while vowels hardly count at
all. (It's not quite engineering.)

Thus the -n- that vanished as "dent-" became
"tooth" doesn't bother word-freaks any more
than the black hole of schwa, the high-falutin'
term for the laziest possible vowel toward which
all vowels tend.

(Schwa? Relax everything in your mouth, even to
the point of letting your tongue hang out, say
"uhhhh," and you'll see where most vowels end
up. D'yuh see thuh point uhv thuh lessuhn?
It's uh simple wuhn tuh illuhstrate. Duh! We
skip, swallow, and slur sounds until someone
says "Huh?" and then repeat ourselves--more
loudly, if not more clearly, a bit like long
threads on rec.bicycles.tech.)

(The -oo- to -ee- change in t**th for
plurality rejoices in the name of internal
vowel gradation. This is strongest in old,
once-powerful words, often animal names like
mouse to mice, goose to geese, and swan to
swine-- Oops, see how easily linguistics trips
us up? Only embittered feminist authorities
suggest a progression from swain to swine.
Vowel gradation also survives in stout old
short verbs like run-ran, speak-spoke, say-said,
sweep-swept, weep-wept, hang-hung, swim-swam,
and lie- Um, just a moment . . . Lay? Laid? Lee?
Lie-reclined! Normal verbs merely add -ed.)

As I'm sure everyone still recalls, I was sneaking
"coelacanth" into a rec.bicycles.tech post on the
pronunciation of "maths." I suggest that I drop my
dead fish and that we all take our baths and go for
our usual rides on the bicycle paths.

Otherwise, I'd have to address the question of
the voiced versus voiced "-ths" and we'd have to
hold the ritual dictionary burning required at the
beginning of any good linguistics class, lest we
forget how we actually speak, start quoting the
lexicographer's printed attempts to define "proper"
pronunciation as opposed to reality, and end up
sounding like a bad production of "My Fair Lady."

If we don't drop this "maths" business soon,
we'll be accused of talking out of our -aths.

(There! Not a hint of alliterative chanting!
Just a straightforward slant-rhyme pun to
illustrate the sort of lisp that Jobst loathes.)

(Try saying those last two words quickly
three times.)

Carl Fogel

On Sat, 11 Oct 2003 13:51:24 -0700, Carl Fogel wrote:

Nothing in Sylvia Plath's work is helpful, but you might turn to
"Jabberwocky" and watch the mome raths outgrabe.

'Outgrabe' is past imperfect; you would watch the raths _outgrab_, or seek
for evidence that they had _outgribben_. Don't they teach you *anything*
in American schools?

(There! Not a hint of alliterative chanting! Just a straightforward
slant-rhyme pun to illustrate the sort of lisp that Jobst loathes.)

Ah, that explains a lot.

[excellent post, BTW. Respect.]

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

;; If God does not write LISP, God writes some code so similar to
;; LISP as to make no difference.

Simon Brooke writes:

After all, pushing a bike forward by
teh saddle is a learned skill and people who haven't learned it don't
find it easy.

There is a simple way to control a bike pushing it by the saddle.
Hold the nose of the saddle and use it to apply torque---you can
now readily control the direction of front wheel. That is,
apply a clockwise torque to turn to right, counterclockwise
to turn left.

Joe

On Sat, 11 Oct 2003 19:26:34 +0000, Phil Holman wrote:

I'm thinking you have the front wheel resting on the ground. The
instruction was to have the bike resting on your shoulder with top tube
angled down just enough for the stationary front wheel to stay straight
ahead (not touching the ground). Spin the front wheel forward and lean
to the left and the steering will turn to the left under both mass
imbalance and gyroscopic effect. Now spin the wheel backwards and lean
to the left and the wheel will turn in the direction of the dominant
force. Left and it's mass imbalance, right and it's gyroscopic effect.
My result was left but I can see where a much shorter stem, regular
brake levers and a heavy front wheel could result in it turning right.

I tried it with a hill bike which happened to be indoors as my road bike
(which I've done all the rest of my tests on) is in the shed. This has a
relatively heavy tyre and short stem; nevertheless my results accord with
yours: spinning the wheel either way does not make an appreciable
difference - mass imbalance overwhelms it. Once again, I would be happy to
film this and post a quicktime.

Jobst?

--
(Simon Brooke) http://www.jasmine.org.uk/~simon/

;; It appears that /dev/null is a conforming XSL processor.

Simon Brooke writes:

In spite of clearly outlining a method for assessing gyroscopic effect
on bicycle steering, without trying to ride or control a bicycle going
backwards, you persist in performing a useless experiment. That rear
steering vehicles are inherently unstable is well known. That is why
forklifts (rear steering vehicles) are driven backwards when traveling
fast from place to place. Wheeling a bicycle backwards is doubly
unstable because it is rear steering and has conflicting caster and
gyroscopic forces.

OK, I've just been out and tried to do this. It's most amusingly
difficult. Hold the bicycle by the saddle and push it backwards. In
my relatively brief experiments, as soon as the bicycle went off
course sufficiently to make a conscious controlling input, I got an
oscillation which rapidly increased in magnitude.

I'm not sure what this proves. After all, pushing a bike forward by
teh saddle is a learned skill and people who haven't learned it
don't find it easy. So possibly with more practice I would have done
better. But going backwards, all the the forces which _may_
contribute to bicycle stability are against you. Try it. It's quite
surprising how very difficult it is!

So let me repeat:

Place the bicycle on the shoulder such that it rests there in the
crotch of top and seat tube, top tube sloping forward just enough to
make the wheel stay straight ahead with the frame in a vertical plane.
Lean the bicycle to either side with the wheel not turning and note
that it responds as one would like steering to do, turning to the side
to which it is leaned.

Spin the wheel forward and there is no change although the response is
sharper. Spin the wheel rearward and the gyroscopic moment overwhelms
the caster or trail effect completely as the wheel steers the "wrong"
way. I think that is a conclusive test.

Jobst Brandt

"Simon Brooke" wrote in message
news
On Sat, 11 Oct 2003 19:26:34 +0000, Phil Holman wrote:

I'm thinking you have the front wheel resting on the ground. The
instruction was to have the bike resting on your shoulder with top
tube
angled down just enough for the stationary front wheel to stay
straight
ahead (not touching the ground). Spin the front wheel forward and
lean
to the left and the steering will turn to the left under both mass
imbalance and gyroscopic effect. Now spin the wheel backwards and
lean
to the left and the wheel will turn in the direction of the dominant
force. Left and it's mass imbalance, right and it's gyroscopic
effect.
My result was left but I can see where a much shorter stem, regular
brake levers and a heavy front wheel could result in it turning
right.

I tried it with a hill bike which happened to be indoors as my road
bike
(which I've done all the rest of my tests on) is in the shed. This has
a
relatively heavy tyre and short stem; nevertheless my results accord
with
yours: spinning the wheel either way does not make an appreciable
difference - mass imbalance overwhelms it. Once again, I would be
happy to
film this and post a quicktime.
Jobst?

Yes please do, a picture is worth a 1000 words.

Phil Holman

Simon Brooke writes:

I'm thinking you have the front wheel resting on the ground. The
instruction was to have the bike resting on your shoulder with top
tube angled down just enough for the stationary front wheel to stay
straight ahead (not touching the ground). Spin the front wheel
forward and lean to the left and the steering will turn to the left
under both mass imbalance and gyroscopic effect. Now spin the wheel
backwards and lean to the left and the wheel will turn in the
direction of the dominant force. Left and it's mass imbalance,
right and it's gyroscopic effect. My result was left but I can see
where a much shorter stem, regular brake levers and a heavy front
wheel could result in it turning right.

I tried it with a hill bike which happened to be indoors as my road
^^

Please explain what "it" is in this context. As was mentioned in the
first paragraph above, you seem to have the front wheel on the ground
which is not "it" the experiment I outlined. Your responses seem like
trying to put a finger on a glob of mercury in a watch glass... can't
quite put your finger on it, or slippery as and eel.

bike (which I've done all the rest of my tests on) is in the
shed. This has a relatively heavy tyre and short stem; nevertheless
my results accord with yours: spinning the wheel either way does not
make an appreciable difference - mass imbalance overwhelms it. Once
again, I would be happy to film this and post a quicktime.

So, stop threatening and post it so we can see what you are doing.
I'm afraid that what you might test and show, judging from the stream
of misinterpretations I've seen up to now.

Jobst Brandt

Carl Fogel wrote:

wrote in message ...

[snip fascinating bicycle physics]


Once more, how does one pronounce "maths" (aloud)?

Jobst Brandt



Dear Jobst,

You dare to ask how "maths" is pronounced?

I warned you! This is not my fault . . .

Perhaps we need more polymaths here or a
field trip to Klamath's Falls?

You're following Goliath's example, Gath's
grave-filler, grimly going ignorant into
great battle.

(That's also a feeble example of Old English
verse, which favored strong alliteratve pairs
bridging an internal line gap. It leads to
chanting passages from "Beowulf.")

Nothing in Sylvia Plath's work is helpful,
but you might turn to "Jabberwocky" and watch
the mome raths outgrabe. Whatever they are,
they're not my favorite fishes, the ancient
coelacanths, whose living existence came out
after Carroll.

(Drat! Another chantable Old English line,
hack-work and hideous!)

Double-drat!)

Ah, you may quibble, there's an internal -n-
that should disqualify "coelacanths" from
this half-learned "-aths" list, lack-witted
and lengthy.

(Drat again!)

A mere internal -n- is famously of no
consequence to linguistics and etymology. The
brothers Grimm were actually more interested
in how Western languages changed than in the
fairy tales that they collected. Jakob found
predictable patterns of change, one of which
is that t's slowly became th's, which then
turned into d's:
t-- th-- d

The obvious example is how both ends of "dent-"
change as it evolves into "tooth."

That dental -n- (a linguistic pun--see what
your tongue touches when you say "dennnn-tal")
was dropped without any qualms as it turned
into "tooth" in not only Indo-European history
but also this tiny-minded treatise, tiresome and
terrible.

(Drat once more!)

An anonymous linguistic law explains the
importance of any single letter or sound when
words change. Our more coherent grunts may be
divided into two sound groups, the true consonants,
which are short and unsustainable, like -p- or -k-
or -t-, and the true vowels, which are sustainable,
like -eeeeeeee-.

(Hmmm, are there are vocalic consonants? Yesss!
There are more vowels, Horatio, than are dreamt
of in your a-e-i-o-u and sometimes y.)

The etymological rule of thumb is that
consonants count for very little when words
slowly change, while vowels hardly count at
all. (It's not quite engineering.)

Thus the -n- that vanished as "dent-" became
"tooth" doesn't bother word-freaks any more
than the black hole of schwa, the high-falutin'
term for the laziest possible vowel toward which
all vowels tend.

(Schwa? Relax everything in your mouth, even to
the point of letting your tongue hang out, say
"uhhhh," and you'll see where most vowels end
up. D'yuh see thuh point uhv thuh lessuhn?
It's uh simple wuhn tuh illuhstrate. Duh! We
skip, swallow, and slur sounds until someone
says "Huh?" and then repeat ourselves--more
loudly, if not more clearly, a bit like long
threads on rec.bicycles.tech.)

(The -oo- to -ee- change in t**th for
plurality rejoices in the name of internal
vowel gradation. This is strongest in old,
once-powerful words, often animal names like
mouse to mice, goose to geese, and swan to
swine-- Oops, see how easily linguistics trips
us up? Only embittered feminist authorities
suggest a progression from swain to swine.
Vowel gradation also survives in stout old
short verbs like run-ran, speak-spoke, say-said,
sweep-swept, weep-wept, hang-hung, swim-swam,
and lie- Um, just a moment . . . Lay? Laid? Lee?
Lie-reclined! Normal verbs merely add -ed.)

As I'm sure everyone still recalls, I was sneaking
"coelacanth" into a rec.bicycles.tech post on the
pronunciation of "maths." I suggest that I drop my
dead fish and that we all take our baths and go for
our usual rides on the bicycle paths.

Otherwise, I'd have to address the question of
the voiced versus voiced "-ths" and we'd have to
hold the ritual dictionary burning required at the
beginning of any good linguistics class, lest we
forget how we actually speak, start quoting the
lexicographer's printed attempts to define "proper"
pronunciation as opposed to reality, and end up
sounding like a bad production of "My Fair Lady."

If we don't drop this "maths" business soon,
we'll be accused of talking out of our -aths.

(There! Not a hint of alliterative chanting!
Just a straightforward slant-rhyme pun to
illustrate the sort of lisp that Jobst loathes.)

(Try saying those last two words quickly
three times.)

Carl Fogel

Are you part of the Gene Daniels school of Usenet posting?

--
Andrew Muzi
www.yellowjersey.org
Open every day since 1 April, 1971

A Muzi wrote in message ...

Are you part of the Gene Daniels school of Usenet posting?

Dear Andrew,

A Google search suggests that you suspect a "gene daniels"
of cocaine-induced ravings:

"For further proof of the corrosiveness of coke, read any
of the assorted 'thoughts' of Gene Daniels"

Let me assure you that my ravings are Coke-induced, the
32-oz bottle being preferred. I fear that the fellow in
question would be appalled to learn that anyone likened
his posts to mine.

Incidentally, I found to my horror that the otherwise
reliable Sheldon Brown failed to scale his gear-inch
calculator down to the clown-cycle 4-inch wheel level that
you mentioned elsewhere in the Dahon thread (see how easily
even decent people are caught up in depravity?), so I'm about
to plead publicly with him to reveal all that he knows about
honest-to-God circus-clown bicycles.

Carl Fogel