unsticking aluminum bar in steel tube
 

In searching for methods to free an aluminum steering stem
from a steel bicycle fork the ideas of using either auto
antifreeze or aqua ammonia have come up. I think the antifreeze
idea is a leftover from the days before aluminum radiators, but
haven't been able to confirm it. The aqua ammonia idea seems
consistent with the chemistry (NH4OH attacks Al(OH)3) but
nobody seems to have any substantive accounts, either of success
or failure.

Does anybody on this group have experience with either method
they'll share?

Thanks for reading!

bob prohaska

unsticking aluminum bar in steel tube
 

On Fri, 4 Aug 2017 01:10:24 -0000 (UTC), bob prohaska
wrote:

In searching for methods to free an aluminum steering stem
from a steel bicycle fork the ideas of using either auto
antifreeze or aqua ammonia have come up. I think the antifreeze
idea is a leftover from the days before aluminum radiators, but
haven't been able to confirm it. The aqua ammonia idea seems
consistent with the chemistry (NH4OH attacks Al(OH)3) but
nobody seems to have any substantive accounts, either of success
or failure.

Does anybody on this group have experience with either method
they'll share?

Thanks for reading!

bob prohaska



There are a number of you tube videos showing the use of lye to
dissolve a aluminum seat post in a steel bicycle frame.

My own experience has been that if dosing with some sort of
penetrating fluid for a few days and a long wrench won't move it that
the lye is probably the best solution as if the aluminum part has been
in the steel tube for a number of years, as bicycle parts often are,
they become almost welded together with corrosion.

--
Cheers,

John B.

unsticking aluminum bar in steel tube
 

On Thursday, August 3, 2017 at 6:14:35 PM UTC-7, bob prohaska wrote:
In searching for methods to free an aluminum steering stem
from a steel bicycle fork the ideas of using either auto
antifreeze or aqua ammonia have come up.

Penetrating oil to start, and maybe some dry ice (aluminum shrinks in cold more
than steel).

unsticking aluminum bar in steel tube
 

whit3rd wrote:

Penetrating oil to start, and maybe some dry ice (aluminum shrinks in cold more
than steel).

Dry ice never occurred to me, it seems worth thinking about.
I believe it's available at the local grocery store.

Thank you!

bob prohaska

unsticking aluminum bar in steel tube
 

bob prohaska wrote:

In searching for methods to free an aluminum steering stem
from a steel bicycle fork the ideas of using either auto
antifreeze or aqua ammonia have come up. I think the antifreeze
idea is a leftover from the days before aluminum radiators, but
haven't been able to confirm it. The aqua ammonia idea seems
consistent with the chemistry (NH4OH attacks Al(OH)3) but
nobody seems to have any substantive accounts, either of success
or failure.

Does anybody on this group have experience with either method
they'll share?

Thanks for reading!

bob prohaska
The aluminum bar is inside the steel tube? If so, freeze it. The aluminum
will shrink more than the steel, making it looser. If you can get dry ice,
that will work best, but just putting the whole assembly in a freezer (if it
will fit) should do it. Otherwise, pack ice around it, let the cold soak
through to the aluminum, and then tap it out.

Jon

unsticking aluminum bar in steel tube
 

On Friday, August 4, 2017 at 9:53:44 PM UTC-4, bob prohaska wrote:
whit3rd wrote:

Penetrating oil to start, and maybe some dry ice (aluminum shrinks in cold more
than steel).

Dry ice never occurred to me, it seems worth thinking about.
I believe it's available at the local grocery store.

Thank you!

bob prohaska

You can improve the heat transfer from the dry ice to the aluminum by making "poor man's liquid nitrogen" which is dry ice in 99% isopropyl alcohol. Be really careful with this stuff, though. It freezes skin on contact. You can also do it with 91% alcohol, but it gets very thick - kind of like honey.. But very, very cold.

unsticking aluminum bar in steel tube
 

"Jon Elson" wrote in message
...

bob prohaska wrote:

In searching for methods to free an aluminum steering stem
from a steel bicycle fork the ideas of using either auto
antifreeze or aqua ammonia have come up. I think the antifreeze
idea is a leftover from the days before aluminum radiators, but
haven't been able to confirm it. The aqua ammonia idea seems
consistent with the chemistry (NH4OH attacks Al(OH)3) but
nobody seems to have any substantive accounts, either of success
or failure.

Does anybody on this group have experience with either method
they'll share?

Thanks for reading!

bob prohaska
The aluminum bar is inside the steel tube? If so, freeze it. The aluminum
will shrink more than the steel, making it looser. If you can get dry ice,
that will work best, but just putting the whole assembly in a freezer (if it
will fit) should do it. Otherwise, pack ice around it, let the cold soak
through to the aluminum, and then tap it out.

Jon
================================================== ======

I'd start with heat first, a heatgun or propane torch. Don't go anywhere
near red hot, just make sure the heat soaks all the way through to fully
expand the aluminum and crush any corrosion between aluminum and steel. I'd
aim for 450-500F, maybe where a drop of water sizzles and floats on steam.
Then quench it in water and cool it all the way back to room temperature and
try tapping on the aluminum to see if it moves. If not, then try the dry
ice.

--
Regards,
Carl Ijames

unsticking aluminum bar in steel tube
 

Carl Ijames wrote:
"Jon Elson" wrote in message
...

bob prohaska wrote:

In searching for methods to free an aluminum steering stem
from a steel bicycle fork the ideas of using either auto


Just to wrap things up, the answer proved surprisingly simple. A hammer
and drift.

The key was supporting the steering fork against the hammering. To my
considerable suprise, two pieces of angle iron hose-clamped to the steering
tube gave the fork crown enough support to let the hammer do its work.

I did flood the parts with acetone and ATF the week before, and it doubtless
helped, but the angle iron crutches were decisive. The real surprise was how
simple and easy the crutches were to set up and use. I expected them to slip,
but one hose clamp sufficed to keep them in place.

There are a few photos at

http://www.zefox.net/~bob/bicycle/stempuller/

Thanks to everybody for helping me sort out the alternatives!

bob prohaska