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02-24-2005, 11:02 PM

On 24.02.05 05:34 Sheldon Brown wrote:
> Andy Ksjls wrote:
>
>>
>>> I got a stuck seat post in a seat tube. Someone suggested Liquid
>>> Wrench. I found it was just some lubricant. Will the more readily
>>> available WD-40 do the job?
>>
>>
> Jobst Brandt replied:
>
>>
>> That probably won't help either because, although you didn't say so, I
>> suspect you have a steel frame and an aluminum seat post. When these
>> two corrode together aluminum expands enough to stretch the seat post.
>> Yours may not yet be at that point but it probably cannot be removed
>> non-destructively.
>
>
> Maybe so, maybe no. See: http://sheldonbrown.com/stuck-seatposts
>
>> The way frame builders remove these is to saw them off, bore them out
>> to a thin shell and grind away a slot in one side to collapse the
>> aluminum remains to remove them. Oil bases lubricants will not help.
>> An acid solvent might work its way in there but I doubt it.
>
>
> Ammonia is good for this...I believe it's a base, not an acid.

Yup, ammonia is a base. For the more extreme cases, a solution of
caustic (AKA sodium hydroxide) literally removes the seatpost. The base
dissolves aluminum forming sodium aluminum hydroxide and hydrogen gas.
Takes some time with thick-walled seatposts, but it works. I tried it
once after using up two hacksaw blades and still not having gone through
the post.

Don't try this at home, kids, and read the MSDS.
--
Størker "sometimes chemistry is useful" Moe
'97 GT Avalanche, '98 Trek 800, '01 Trek Fuel 90

Email Storker(DOT)Moe(AT)c2i(DOT)net
WWW http://home.c2i.net/storker_moe/

A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

02-24-2005, 11:02 PM	#32 (permalink)
Størker Moe Guest Posts: n/a	Re: Liquid Wrench On 24.02.05 05:34 Sheldon Brown wrote: > Andy Ksjls wrote: > >> >>> I got a stuck seat post in a seat tube. Someone suggested Liquid >>> Wrench. I found it was just some lubricant. Will the more readily >>> available WD-40 do the job? >> >> > Jobst Brandt replied: > >> >> That probably won't help either because, although you didn't say so, I >> suspect you have a steel frame and an aluminum seat post. When these >> two corrode together aluminum expands enough to stretch the seat post. >> Yours may not yet be at that point but it probably cannot be removed >> non-destructively. > > > Maybe so, maybe no. See: http://sheldonbrown.com/stuck-seatposts > >> The way frame builders remove these is to saw them off, bore them out >> to a thin shell and grind away a slot in one side to collapse the >> aluminum remains to remove them. Oil bases lubricants will not help. >> An acid solvent might work its way in there but I doubt it. > > > Ammonia is good for this...I believe it's a base, not an acid. Yup, ammonia is a base. For the more extreme cases, a solution of caustic (AKA sodium hydroxide) literally removes the seatpost. The base dissolves aluminum forming sodium aluminum hydroxide and hydrogen gas. Takes some time with thick-walled seatposts, but it works. I tried it once after using up two hacksaw blades and still not having gone through the post. Don't try this at home, kids, and read the MSDS. -- Størker "sometimes chemistry is useful" Moe '97 GT Avalanche, '98 Trek 800, '01 Trek Fuel 90 Email Storker(DOT)Moe(AT)c2i(DOT)net WWW http://home.c2i.net/storker_moe/ A: Because it messes up the order in which people normally read text. Q: Why is top-posting such a bad thing? A: Top-posting. Q: What is the most annoying thing on usenet and in e-mail?