Seized quill stem

On 12 Feb, 19:08, Jobst Brandt wrote:

Instead of offering rhetorical questions,

As rethorical as you might have read it, it perhaps deserved a better
answer.

how about a positive
suggestion on how to fix it?

That's exactly what I wrote in another, this time quite positive,
message.
Should I divulgate a picture of a frame that I scorched to free a
similarly stuck component?

Tell you what.
A heat shock also freed a stuck cartridge bottom bracket after two
local competent bike mechanics had not been able to remove it.
They had given up the effort, feeling the risk of twisting the frame
(with the extractor held firm in the vise).

Heat waves can do wonders.

Sergio
Pisa

Jobst Brandt wrote:
Heat has no effect on aluminum oxide inside a steel steertube.

sergio wrote:
You serious, Jobst?
Isn't this statement a tad too bold?

Well, narrowly, he's right. The aluminum oxide isn't
affected at these temperatures but the aluminum stem core
does expand, shrink or melt effectively.

Jobst notes that the aluminum oxide layer is inert but I
don't think that phenomenon has any practical effect in the
instant case of a stuck stem. One removes the oxide layer in
shards easily with a pick after the stem is out.

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

On 12 Feb, 19:46, AMuzi wrote:
Jobst notes that the aluminum oxide layer is inert but I
don't think that phenomenon has any practical effect in the
instant case of a stuck stem.

Pardon me.
The shrinkage or expansion, upon cooling or heating below melting
point, of any (very thin) layer is minimal compared to the dimensional
change of the (relatively massive) components nearby.
Was that the message?

Why should one negate the fact that the adhesion through the oxide
layer gets compromised by the heat shock?
Isn't this some relevant effect?

Sergio
Pisa

On 12 Feb, 19:54, Jobst Brandt wrote:
Heat waves can do wonders.
From my experience that is wishful thinking, rather than fact. I am
not sure how solidly your seized parts were attached.

Not so according to my experience.
For example, I was able to unscrew easily a rather stuck pedal by
heating with the flame of a candle.

This other time I had to free a seatpost.
After struggling with brute force, I tried with the heat: no success.
Then I took the thing over to a retired framebuilder, Gino Vanni, an
old man who happens to be a friend of mine. I asked him to melt the
aluminum out.
Before resorting to the flame, ailing Gino grabbed the saddle that was
still in place and freed the post.

Lesson n.1 for me
After heating up I should have waited until cool, better yet if I had
cooled it with a 'negative' shock.

Sergio
Pisa

On 12 Feb, 18:08, Jobst Brandt wrote:
Sergio Servadio wrote:
Heat has no effect on aluminum oxide inside a steel steertube.
You serious, Jobst?
Isn't this statement a tad too bold?

Instead of offering rhetorical questions, how about a positive
suggestion on how to fix it? *I went through the quill stem failure
with several Cinelli stems and a steel Ritchey stem

Any intelligent rider would have got either some paint or oil in there
after the third time. Plugging the bottom of the steerer mitigates
the condensation which causes the corrosion (mixed in with salts,
possilbly from sweating).

before the
threadless steertube came along, for which I was glad and have used
ever since with no problems and amazingly greater handlebar stiffness.

The quill stem rocks around from side-to-side above its expander in
the steertube (pumping in fluids) where, in contrast, the threadless
stem is ultimately stiff. *A great feeling.

Jobst Brandt

On 12 Feb, 19:14, sergio wrote:
On 12 Feb, 19:54, Jobst Brandt wrote:

Heat waves can do wonders.
From my experience that is wishful thinking, rather than fact. *I am
not sure how solidly your seized parts were attached.

Not so according to my experience.
For example, I was able to unscrew easily a rather stuck pedal by
heating with the flame of a candle.

This other time I had to free a seatpost.
After struggling with brute force, I tried with the heat: no success.
Then I took the thing over to a retired framebuilder, Gino Vanni, an
old man who happens to be a friend of mine. I asked him to melt the
aluminum out.
Before resorting to the flame, ailing Gino grabbed the saddle that was
still in place and freed the post.

Lesson n.1 for me
After heating up I should have waited until cool, better yet if I had
cooled it with a 'negative' shock.

Sergio
Pisa

Come to think of it, when releasing the screws on an aging car door, I
whacked 'em not only hot, but as they cooled down before they
released. They not only released tyhe bond, but were positively free,
not anywhere representative of the torque applied (without effect
before the heat and cool cycle).

On 02/12/2010 06:02 PM, Jobst Brandt wrote:
Frank Leake wrote:

snip

In the true path of RBT, "This ones really stuck, I may need a
bigger blowtorch..."

Heat has no effect on aluminum oxide inside a steel steertube. As I
said, saw the stem off at the top of the steertube and bore it out.
You have earned the course in threadless steertubes. Do it.

I'm no engineering type, but I would have thought the expansion wotsit
between the steel outer and aluminum inner would have been a, to coin a
phrase, **** of a lot. The stuck steerer tubes and seat tubes I've had
usually give way to a bit of heat.

On 2010-02-12, Jobst Brandt wrote:
Sergio Servadio wrote:

Instead of offering rhetorical questions, how about a positive
suggestion on how to fix it?

As rhetorical as you might have read it, it perhaps deserved a
better answer.

That's exactly what I wrote in another, this time quite positive,
message.

I didn't see how heating aluminum would make it shrink away from the
steel steertube or how heat would loosen aluminum oxide that had
chemically expanded between the stem and steertube.

I think the idea is just that things move a bit relative to each other
and that breaks the bond gluing them together, even if you're actually
making the part that's on the inside bigger.

In article
,
sergio wrote:

On 12 Feb, 18:02, Jobst Brandt wrote:
Heat has no effect on aluminum oxide inside a steel steertube.

You serious, Jobst?
Isn't this statement a tad too bold?

Al2O3.
Melting point: 2072 deg C.
Mostly insoluble.
The Al sits at the bottom of a deep electrochemical trench.

Fe melting point: 1535 deg C.

--
Michael Press

Jobst Brandt wrote:
Trevor M. Jeffrey wrote:

Heat has no effect on aluminum oxide inside a steel steertube.

You serious, Jobst? Isn't this statement a tad too bold?

Instead of offering rhetorical questions, how about a positive
suggestion on how to fix it? Â I went through the quill stem failure
with several Cinelli stems and a steel Ritchey stem before the
threadless steertube came along, for which I was glad and have used
ever since with no problems and amazingly greater handlebar
stiffness.

Any intelligent rider would have got either some paint or oil in
there after the third time. Plugging the bottom of the steerer
mitigates the condensation which causes the corrosion (mixed in with
salts, possilbly from sweating).

The failure occurs from rider sweat and rain water that has adequate
access at the upper end of the aluminum stem, even though lock rings
on head bearings were equipped with an O-ring so small that it pumps
when the stem swivels from side to side. It does not come in from the
bottom, although various frame makers offered plugged forks without
any effect believing it came from below. These were a nice gestures,
recognizing the effect, but not its cause or solution.

The quill stem rocks around from side-to-side above its expander in
the steertube (pumping in fluids) where, in contrast, the
threadless stem is ultimately stiff. Â A great feeling.

The wooden plugs of old were supposed to keep a crown/column
crack from killing the rider. In my experience they hold
moisture inside the column anyway.

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