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
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On Fri, 4 Aug 2017 01:10:24 -0000 (UTC), 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.
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On Thursday, August 3, 2017 at 6:14:35 PM UTC-7, bob prohaska wrote:

Penetrating oil to start, and maybe some dry ice (aluminum shrinks in cold more than steel).
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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
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On Friday, August 4, 2017 at 9:53:44 PM UTC-4, bob prohaska wrote:

old more

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

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
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"Jon Elson" wrote in message
bob prohaska wrote:

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
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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
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