Retrobike Forum Index

It is currently Tue Dec 06, 2016 9:23 pm

* Login   * Register * Search  * FAQ



Post new topic Reply to topic  [ 11 posts ]  Go to page 1, 2  Next
Author Message
PostPosted: Tue Feb 26, 2013 4:39 pm 
Dirt Disciple

Joined: Wed Jan 23, 2013 12:54 pm
Posts: 28
Location: Bedfordshire
As some of you may have seen via my posts in this thread, I recently bought an old (1992ish) Specialized Hardrock with a stuck seatpost, with the intention of getting the post out and fixing the bike up as a spare ride.

I finished off the hacksaw method job the previous owner had started but it was still stuck, prompting me to start the dreaded caustic method... The bottom bracket wasn't going to come out in a hurry so I decided to feed the caustic solution through one of the bottle cage holes in the seat tube with the bike upside-down, as suggested by another Retrobike member. Rather than using an old syringe like they did, I botched an old spray cleaning bottle into something that would do the same job. This was my second one, the first got a bit melted and leaky after a few uses....

Attachment:
photo(20).JPG
photo(20).JPG [ 27.05 KiB | Viewed 520 times ]


As there was bits of metal protruding out of the top, I ended up using plasticine to seal the seat tube. I mixed the caustic solution in a thick plastic bottle, and poured in about 300ml each session. (In hindsight, I probably should have stripped the bike down to its bare frame, but nevermind...)

Attachment:
photo(21).JPG
photo(21).JPG [ 36.05 KiB | Viewed 520 times ]


As time went on I got braver/impatient so went from using a solution of 1 part caustic to 5 parts water, to using nearly 1:1 by the end of it. Each time after about five minutes smoke would start coming out of the bottle cage hole, along with a black, gooey sludge (see the vid below!). After each session the post seem to be getting a lot thinner, and the top few inches started to disappear.

Attachment:
photo(22).JPG
photo(22).JPG [ 30.92 KiB | Viewed 520 times ]


Image

After one final, rather strong load last Sunday, it looked as though I'd finally done it. Flushed out the rest of the black goo today, and used some pliers to extract this final bit:

Image

Lost track of how many lots it took in the end, I'd say probably 5-6ish, plus a couple of failed attempts with a dodgy lot of caustic crystals that didn't seem to dissolve properly. Ended up using around a kilo of soda crystals in the end, not so bad I thought. Very chuffed now, but I've got an extensive clean up job on my hands!

If anyone is thinking of trying this but is a little fearful of damaging themselves/the bike, just go for it, with some sensible precautions it's a great method of getting an alu post out of a steel frame if absolutely nothing else will work.


Top
 Profile  
 
PostPosted: Tue Feb 26, 2013 7:06 pm 
Devout Dirtbag

Joined: Sun May 09, 2010 12:53 pm
Posts: 137
Location: Great Britain
Nice work. A job well done. I'll be keeping that one in mind should I encounter this problem in the future.


Top
 Profile  
 
PostPosted: Tue Feb 26, 2013 7:33 pm 
Retro Guru
User avatar

Joined: Fri Jan 13, 2012 2:28 am
Posts: 1057
Location: Near Gatwick
So the plasticene was OK, I am sure that's a handy bit of info.


Top
 Profile  
 
PostPosted: Tue Feb 26, 2013 7:38 pm 
Dirt Disciple

Joined: Wed Jan 23, 2013 12:54 pm
Posts: 28
Location: Bedfordshire
integerspin wrote:
So the plasticene was OK, I am sure that's a handy bit of info.

It wasn't too bad, getting it to seal properly was a bit of a pain though. The plug you made for yours looked like a much better solution!


Top
 Profile  
 
PostPosted: Tue Feb 26, 2013 10:56 pm 
Retro Guru

Joined: Wed May 18, 2011 9:26 pm
Posts: 1477
Location: essex
Hi

What make did you use...have been some asdas stuff whichis no good :oops: :oops:


Top
 Profile  
 
PostPosted: Tue Feb 26, 2013 11:12 pm 
Old School Grand Master
User avatar

Joined: Mon Jun 14, 2010 9:06 pm
Posts: 4437
Location: Herts UK
whayne wrote:
Hi

What make did you use...have been some asdas stuff whichis no good :oops: :oops:


yeah, the really cheap stuff like Asdas has been found to contain salt DNA.


Top
 Profile  
 
PostPosted: Wed Feb 27, 2013 12:00 am 
Dirt Disciple

Joined: Wed Jan 23, 2013 12:54 pm
Posts: 28
Location: Bedfordshire
whayne wrote:
Hi

What make did you use...have been some asdas stuff whichis no good :oops: :oops:



Funnily enough the useless stuff did come from Asda, it just wouldn't dissolved and sank to the bottom of the bottle in a big lump. Oddly though it was the same brand as the other bottles which I got from Wilkos (see link below), and those worked just fine. Cheaper from there too.

http://www.wilkinsonplus.com/surface-cl ... t/1159440/


Top
 Profile  
 
PostPosted: Wed Feb 27, 2013 3:46 am 
Retro Guru
User avatar

Joined: Fri Jan 13, 2012 2:28 am
Posts: 1057
Location: Near Gatwick
I buy mine from an ironmongers. 500gram did two seat posts and
I boiled some engine parts in caustic.
Did the asda stuff get hot when you put it in water?


Attachments:
caustic.jpg
caustic.jpg [ 14.17 KiB | Viewed 421 times ]
Top
 Profile  
 
PostPosted: Wed Feb 27, 2013 11:04 am 
Dirt Disciple

Joined: Wed Jan 23, 2013 12:54 pm
Posts: 28
Location: Bedfordshire
It got a little warm but nowhere near as hot as the same branded stuff I purchased from Wilkinsons did. Just a bad batch of it, I suppose.


Top
 Profile  
 
PostPosted: Wed Feb 27, 2013 12:24 pm 
retrobike rider
retrobike rider

Joined: Thu Apr 17, 2008 1:24 am
Posts: 7562
Location: Manchester
Just remember that caustic soda is used to dissolve flesh!
The black stuff is whatever else was in the aluminium alloy after the aluminium has been dissolved.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 11 posts ]  Go to page 1, 2  Next

All times are UTC [ DST ]


Who is online

Users browsing this forum: CTK, Double-E F, kikideparis, longun, PaintedDesert, Retro junkie, royboy2cv, toomanyframes and 51 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  

About Us

Follow Retrobike

Other cool stuff

All content © 2005-2015 Retrobike unless otherwise stated.
Cookies Policy.
bikedeals - the best bike deals in one place
FatCOGS - Fat Chance Owner's Group

Powered by phpBB® Forum Software © phpBB Group