Alu post stuck in alu frame

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SimonCelsa
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Re: Alu post stuck in alu frame

Postby SimonCelsa » 11 Jan 2020, 5:04pm

If you can do so, get hold of some liquid nitrogen


serious stuff; I used to work on Liquefied Natural Gas ships (methane), carrying the product at around minus 163 degC. You wouldn't want any of that splashed on your appendages. Likewise liquid Nitrogen at minus 196 degC..........could do some serious embrittlement.

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RickH
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Location: Horwich, Lancs.

Re: Alu post stuck in alu frame

Postby RickH » 11 Jan 2020, 5:52pm

SimonCelsa wrote:
If you can do so, get hold of some liquid nitrogen


serious stuff; I used to work on Liquefied Natural Gas ships (methane), carrying the product at around minus 163 degC. You wouldn't want any of that splashed on your appendages. Likewise liquid Nitrogen at minus 196 degC..........could do some serious embrittlement.

There is an interesting effect, named after someone who's name escapes me, whereby you can put your hand briefly into a flask of liquid nitrogen with no ill effect. The heat of your hand boils a little of the nitrogen meaning there is a thin film of gas round your hand. I've done it & suffered no ill effects - it feels cool/cold on your hand but not excessively so.

You can also make instant ice cream - pour liquid nitrogen into a small container with some double cream in (plus flavourings as desired) & stir it continuously until it turns into ice cream! :D It could provide some consolation if the liquid nitrogen doesn't free the seatpost! :lol:

(A couple we know used to go into schools to do fun science which is how I got to know these things).

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SimonCelsa
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Re: Alu post stuck in alu frame

Postby SimonCelsa » 11 Jan 2020, 6:37pm

Yes, I think you'd have to put your hand in only very briefly.

Even spilling a few cubic metres of these cryogenic liquids gives fairly spectacular vapor clouds; https://www.tradewindsnews.com/weekly/m ... 1-1-769623 - just hope nobody is smoking in the near vicinity!!

Jdsk
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Re: Alu post stuck in alu frame

Postby Jdsk » 11 Jan 2020, 6:43pm

RickH wrote:There is an interesting effect, named after someone who's name escapes me, whereby you can put your hand briefly into a flask of liquid nitrogen with no ill effect.

Leidenfrost: https://en.wikipedia.org/wiki/Leidenfrost_effect

Please don't try this unless you know what you're doing.

Jonathan

goosegog
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Joined: 3 Mar 2009, 3:30pm

Re: Alu post stuck in alu frame

Postby goosegog » 13 Jan 2020, 2:36pm

My tried and tested method for corroded metal is heating the outer section with a hot-air gun ( used for paint stripping ) then using a plumber`s freezer spray( available in the plumbing section of DIY stores) on the inner section. A couple of goes might be required.

Marcus Aurelius
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Re: Alu post stuck in alu frame

Postby Marcus Aurelius » 13 Jan 2020, 2:54pm

goosegog wrote:My tried and tested method for corroded metal is heating the outer section with a hot-air gun ( used for paint stripping ) then using a plumber`s freezer spray( available in the plumbing section of DIY stores) on the inner section. A couple of goes might be required.

Yep, I tend to use a brazing torch ( or one of those kitchen torches for doing creme brûlée ) and LN2 to cool it afterwards though. It can make quite a noise if it works properly.

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Mick F
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Re: Alu post stuck in alu frame

Postby Mick F » 13 Jan 2020, 3:04pm

I had a wart on a finger as a teenager.
Not nice on the knuckle which would catch on brake cables. :shock:
Hurt like heck and went to the doctor's to make an appointment.

They took delivery of liquid nitrogen from time to time, and I turned up when they had another batch in. It came in a standard thermos flask.
Cotton bud dipped into the liquid and held on my wart.

Killed the virus dead, and within a week the wart fell off.
Mick F. Cornwall

gregoryoftours
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Re: Alu post stuck in alu frame

Postby gregoryoftours » 17 Jan 2020, 7:09pm

Thanks for your replies everyone, I'm waiting on a large freeze spray and I'll try that in conjunction with boiling water or heat gun and see if i can get anywhere! I'm a little reluctant to try ammonia of any strength until nothing else has worked. I absolutely do not trust my ability to saw through a seatpost stuck far into the frame without also cutting into the aluminium seat tube!