A mystery for you all

sounds like the frame broke at the bottom bracket shell. or the bottom
bracket itself broke and they couldn't get it out however hard they tried...

"Reid Priedhorsky" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Hello all,

I'm reading _The Immortal Class_ by Travis Hugh Culley; it's about the
author's experiences as a Chicago bike messenger. In it there is an
episode where Travis's bike breaks down and the mechanic can't fix it,
requiring him to build up a new bike.

I'm curious what went wrong and why the mechanic couldn't fix it, so I
call upon your expertise. Here are the relevant passages (they are on
pp. 144-148):

Quoted message said:

Those first few months at Service First cost me a set of tires, a rear
wheel, a set of brakes, and a cassette. But none of this really
worried me until I heard my bottom bracket split....

[...]

Quoted message said:

"Thirty-nine to base."

"Thirty-nine, go."

"I think my crank just snapped." [parts confusion in original]

"*Snapped?* That doesn't sound good. Does it still work?"

"Well, it doesn't sound good. You had that right"

"10-4. You're on your way to Yojimbo's." [location of mechanic]

[Travis goes to Yojimbo's and finds Marcus, the mechanic.]

Quoted message said:

"Sit down, man. Bracket snapped? Was that the problem?"

"I don't know. Whatever's in there is [censored].

"Bottom bracket, he said, as if it was perfectly ordinary.

[Marcus starts working and Travis chills.]

Quoted message said:

... Marcus had attached a thin wrench to the inside of my pedal, and
he began spinning the crank arms while the chain spun in place. In
seconds the pedal fell to the floor with a thud and Marcus peeled the
chain off the chain ring, to get it out of his way....

[...]

Quoted message said:

... [Marcus had] said that he just needed to get the old bracket out
and put a new one in. It would cost twenty bucks, twenty-five with
labor, and it would take about ten minutes. He handed me back my
pedals and said, "I think your frame is shot."

I encouraged him to give it another try because I had nothing else to
work on. Everything hung in the balance. If I don't have wheels, I
don't have work.

A day and a half later, I came back to find Marcus with the frame on
the floor, a collection of cinder blocks and wrenches all strapped
together to maximize the torque on the bracket. Marcus was standing on
the handle of the elongated wrench set, sweating and cursing. When he
saw me he climbed down from his contraption, grabbed a huge wrench,
and began walking toward me. He put the wrench in my hands, and then
righted it so that I could see the tool's twisted and gnarly teeth.
Something had chewed it to pieces. Marcus said very calmly, "Your
frame *is shot*."

After this, they give up on the frame and Marcus builds up another for
Travis. My questions:

1. What went wrong?
2. Why couldn't Marcus get the bottom bracket out?

I don't know what the original bike was -- either the author didn't say
or I don't remember. But I don't believe it was anything with unusual
threading. The messenger community regards Marcus very skilled bike
mechanic.

Thanks!

Reid

Reid Priedhorsky wrote in message ...

Quoted message said:

1. What went wrong?
2. Why couldn't Marcus get the bottom bracket out?

The French like everything contrary. RH thread fixed cup.
TJ

Reid Priedhorsky said:

Hello all,

I'm reading _The Immortal Class_ by Travis Hugh Culley; it's about the
author's experiences as a Chicago bike messenger. In it there is an
episode where Travis's bike breaks down and the mechanic can't fix it,
requiring him to build up a new bike.

I'm curious what went wrong and why the mechanic couldn't fix it, so I
call upon your expertise. Here are the relevant passages (they are on
pp. 144-148):

....

Quoted message said:

Quoted message said:

A day and a half later, I came back to find Marcus with the frame on
the floor, a collection of cinder blocks and wrenches all strapped
together to maximize the torque on the bracket. Marcus was standing on
the handle of the elongated wrench set, sweating and cursing. When he
saw me he climbed down from his contraption, grabbed a huge wrench,
and began walking toward me. He put the wrench in my hands, and then
righted it so that I could see the tool's twisted and gnarly teeth.
Something had chewed it to pieces. Marcus said very calmly, "Your
frame *is shot*."

1. What went wrong?
2. Why couldn't Marcus get the bottom bracket out?

Sounds somewhat similar to what once happened to me when I wanted to
replace a bottom bracket on our tandem. Took the bike to the LBS to
have them remove the fixed cup. Heard lots of grunting and a few
choice words coming from the back room and finally the owner comes out
front. Says the cup is stuck in there really tight and to come back
with him. They've clamped the wrench in their shop vice so they
can use the whole length of the frame (and tandems are pretty long)
as a lever. He says that all the guys in the shop can push on the
frame together and either the cup will come out or the frame will break.
Before I give him permission to proceed I ask whether it's possible
that the threading is reversed (Swiss and French threading of the
fixed cup is identical except one is left-hand and the other right).
They give it a try turning in the other direction and of course the
cup spins right out.

"Reid Priedhorsky" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Quoted message said:

... Marcus had attached a thin wrench to the inside of my pedal, and
he began spinning the crank arms while the chain spun in place. In
seconds the pedal fell to the floor with a thud and Marcus peeled the
chain off the chain ring, to get it out of his way....

He took off the *pedals* to get at the B.B.? He can't be that good.

--
Derek Hodges
Toronto

"Derek Hodges" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"Reid Priedhorsky" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Quoted message said:

... Marcus had attached a thin wrench to the inside of my pedal, and
he began spinning the crank arms while the chain spun in place. In
seconds the pedal fell to the floor with a thud and Marcus peeled the
chain off the chain ring, to get it out of his way....

He took off the *pedals* to get at the B.B.? He can't be that good.

I missed that!
I got the french thing but even if it wasn't french I wondered why he
didn't just spot weld a giant nut to the fixed cup .. the combination
of high localized heat and extra torque never failed for me.. (in the
maybe three times I ever needed to try it)

ajames54 said:

"Derek Hodges" <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"Reid Priedhorsky" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

>... Marcus had attached a thin wrench to the inside of my pedal, and
>he began spinning the crank arms while the chain spun in place. In
>seconds the pedal fell to the floor with a thud and Marcus peeled the
>chain off the chain ring, to get it out of his way....

He took off the *pedals* to get at the B.B.? He can't be that good.

I missed that!
I got the french thing but even if it wasn't french I wondered why he
didn't just spot weld a giant nut to the fixed cup .. the combination
of high localized heat and extra torque never failed for me..

How does extra torque help if you're trying to turn it to the right when
you should be turning it to the left? The extra torque would just let
you destroy things a little quicker.

While I think that book is very artfully written, and is probably responsible for turning me into a cyclist, reading it again (as I have done a few times) makes me realize that maybe Mr. Culley didn't have quite as tight a grasp of the technical aspects of cycling than he does on writing. I remember in another passage he speaks of the risk of "hydroplaning" a bicycle on wet pavement, something that Sheldon proves to be a technical impossibility (unless, of course, his bicycle is rocket-boosted) somewhere on his site.

It's still a good read.
-Jeremy

[quote="Reid Priedhorsky"]Hello all,

I'm reading _The Immortal Class_ by Travis Hugh Culley; it's about the
author's experiences as a Chicago bike messenger. In it there is an
episode where Travis's bike breaks down and the mechanic can't fix it,
requiring him to build up a new bike.
😎

One has to remove pedals to service a BB when its the old, one-piece forged steel crank design. These has NO threads in the BB shell as the crank itself is threaded to set bearing preload. If something goes wrong, the bearing cups can be forced inward and this might cause a BB shell to split. Or the BB shell could have split, causing the threads on the crank to fail making removal of the lock nut and race very difficult.

"jtill" <[email hidden]> a écrit dans le
message de :
news:[email hidden]...

Quoted message said:

I remember in another passage he speaks of the risk of
"hydroplaning" a bicycle on wet pavement, something that Sheldon proves
to be a technical impossibility (unless, of course, his bicycle is
rocket-boosted) somewhere on his site.

As I like to ask dumb questions, here goes :

What is happening when riding (slithering, wiggling, sliding, and then
falling) on ice ? If the tire displaces the water to the level of a dry bed
of ice, what gives ? That, too, is not hydroplaning ? I used to ride in
winter wonderlands on ice-covered streets, and was careful not to fall too
often.
--
Bonne route,

Sandy
Paris FR

SMMB said:

"jtill" <[email hidden]> a écrit dans le
message de :
news:[email hidden]...

Quoted message said:

I remember in another passage he speaks of the risk of
"hydroplaning" a bicycle on wet pavement, something that Sheldon proves
to be a technical impossibility (unless, of course, his bicycle is
rocket-boosted) somewhere on his site.

As I like to ask dumb questions, here goes :

What is happening when riding (slithering, wiggling, sliding, and then
falling) on ice ? If the tire displaces the water to the level of a dry bed
of ice, what gives ? That, too, is not hydroplaning ? I used to ride in
winter wonderlands on ice-covered streets, and was careful not to fall too
often.
--
Bonne route,

Sandy
Paris FR

The ice melts under the pressure of the wheel making even a blade of a skate hydroplane. Hydroplaning on ice is favored by high contact pressures since the interface is very precise and regelation is also favored by high contact pressures.

--On Friday, August 06, 2004 6:34 AM +1000 Weisse Luft

Quoted message said:

The ice melts under the pressure of the wheel making even a blade of a
skate hydroplane. Hydroplaning on ice is favored by high contact
pressures since the interface is very precise and regelation is also
favored by high contact pressures.

Works in theory, but think practically. How wide is a bicycle tire relative
to an ice skate? Pretty wide, at least 2-3 times the skate's width if I
were to hazard a guess. And I'd bet the contact patch is longer too, making
this a valid but not necessarily true statement. I'd wager it has more to
do with the ice/rubber interface simply having a much lower coefficient of
friction than asphalt/rubber for which the tires are designed.

However, if you can show numbers that would agree with the water tables in
my thermo tectbook, I'll buy your theory.

Mike
Mechanical Engineering 2006, Carnegie Mellon University
Remove nospam to reply.

And what if the ice already was close to melting point?
TJ

--On Friday, August 06, 2004 7:42 AM +0100 Trevor Jeffrey

Quoted message said:

And what if the ice already was close to melting point?
TJ

The temperature of the ice would merely change the numbers in the
calculations, and this could possibly sway it in favor of the ice skate
phenomenon. In this case, the pressure (simply bike+rider weight divided by
contact patch area) required to melt the ice and form a layer of water
would be lower, unless we're already dealing in some temperature that is
below the triple point of water, in which case the water would sublime
(solid->gas) instead of melting (solid->liquid).

Mike
Mechanical Engineering 2006, Carnegie Mellon University
Remove nospam to reply.

Prometheus said:

--On Friday, August 06, 2004 7:42 AM +0100 Trevor Jeffrey

Quoted message said:

And what if the ice already was close to melting point?
TJ

Quoted message said:

The temperature of the ice would merely change the numbers in the
calculations, and this could possibly sway it in favor of the ice skate
phenomenon. In this case, the pressure (simply bike+rider weight divided
by contact patch area) required to melt the ice and form a layer of
water would be lower, unless we're already dealing in some temperature
that is below the triple point of water, in which case the water would
sublime (solid->gas) instead of melting (solid->liquid).

Mike
Mechanical Engineering 2006, Carnegie Mellon University

Better get back to your studies. Since we're talking about a situation
with a patch of ice, the temperature will have to be below that of
the triple point of water since that's the highest temperature at which
water can be a solid.

The phase diagram for water shows a line with a
negative slope separating the solid and liquid phases and therefore
pressure increases can induce the solid -> liquid transition. But
there is no region with a negative slope line between solid and gas
phases, so increased pressure will not induce a solid -> gas transition.
For very low temperatures (< -22C) the water will remain a solid at all
pressures but undergo phase transitions between different ice
structures.
At higher temperatures but still below the triple point the effect of
increased pressure would be to induce gas -> solid -> liquid whereas at
temperatures above the triple point the transition would be gas ->
liquid in response to rising pressure.

BTW, even for ice skates the pressure-induced melting theory is
insufficient. Growing up in North Dakota it was clear to me that
skating was still possible at temperatures well below 0 C even though
the pressure would only raise the melting point by a fraction of
a degree. Local frictional heating of the ice probably
plays a role, but I don't think the phenomenon is completely
understood.
The pressure of bicycles tires is about 7 atmospheres and would only
change the melting point of water less than a tenth of a degree C - not
much of an effect.

You are looking at the AVERAGE contact pressure. The actual contact area can be several time less than the geometric area. Nothing is smooth, nothing is actually flat.

Weisse Luft said:

You are looking at the AVERAGE contact pressure. The actual contact
area can be several time less than the geometric area. Nothing is
smooth, nothing is actually flat.

Even if true, "several times" as high doesn't change anything
substantially. It takes a pressure of 121 atmospheres to
increase the melting point by 1 degree C. And below -22 C
you don't get any melting even with infinite pressure.

Peter said:

Weisse Luft said:

You are looking at the AVERAGE contact pressure. The actual contact
area can be several time less than the geometric area. Nothing is
smooth, nothing is actually flat.

Even if true, "several times" as high doesn't change anything
substantially. It takes a pressure of 121 atmospheres to
increase the melting point by 1 degree C. And below -22 C
you don't get any melting even with infinite pressure.

Sorry, meant to say decrease the melting point by 1 degree C.

"Peter" <[email hidden]> a écrit dans le message de :
news:[email hidden]...

Quoted message said:

Prometheus said:

--On Friday, August 06, 2004 7:42 AM +0100 Trevor Jeffrey

Quoted message said:

And what if the ice already was close to melting point?
TJ

OK ! OK !

I believe all of you !!

So is sliding in the water-on-ice situation really not hydroplaning ?
All I seem to get is that with hydroplaning, the friction surface under the
water is no longer in contact with the tire. Right ? So, can I please get
an answer to the simple Q ?
--
Sandy
Paris FR

*******

La vie, c'est comme une bicyclette,
il faut avancer pour ne pas perdre l'équilibre.
-- Einstein, A.
(And this really seems appropriate in the thread ...)

SMMB said:

"Peter" <[email hidden]> a écrit dans le message de :
news:[email hidden]...

Quoted message said:

Prometheus said:

--On Friday, August 06, 2004 7:42 AM +0100 Trevor Jeffrey
<[email hidden]> wrote:

>And what if the ice already was close to melting point?
>TJ

OK ! OK !

I believe all of you !!

So is sliding in the water-on-ice situation really not hydroplaning ?

Yes, the slipperiness of wet ice is a different phenomenon than
hydro/aquaplaning.

Quoted message said:

All I seem to get is that with hydroplaning, the friction surface under the
water is no longer in contact with the tire. Right ?

Yes.