Caustic Soda to melt stuck seatpost: COMPLETED!! (see p.2)

Apologies for resurrecting a bit of an old post, but did the BB survive the process in the end? I'm about to do this to an old Specialized Hardrock I have as the hacksaw method has failed, I don't have a BB tool and even if I get hold of one, I'm expecting it to be a bit of a sod to remove!

Cheers
 
Love the swearing and the excited tone of voice!!

Wondering wether this method would work on seized bottom bracket cups?? :LOL:
 
Wondering wether this method would work on seized bottom bracket cups??

Steel cups in a steel frame - no.

Steel cups in an aluminium frame - yes, but not the way you want. :D
 
Matt87":1657z61v said:
Apologies for resurrecting a bit of an old post, but did the BB survive the process in the end? I'm about to do this to an old Specialized Hardrock I have as the hacksaw method has failed, I don't have a BB tool and even if I get hold of one, I'm expecting it to be a bit of a sod to remove!

Cheers

You could saw the seat post off, cork the open end, flip the bike over and put the caustic though a bottle bolt hole. once you have thinned the post down a lot the ring the cork is in should come out easy.

I recently removed the remains of a seat post that had been hammered down the tube, I took pictures while I did it and video. I will sort some out if any interest.
 
xerxes":1sdjm0h8 said:
Wondering wether this method would work on seized bottom bracket cups??

Steel cups in a steel frame - no.

Steel cups in an aluminium frame - yes, but not the way you want. :D

Lol.. Can just imagine..

Hello I need this bottom bracket out this frame.

Few weeks later.. Here is your bottom bracket sir...;)
 
integerspin":21xkyr4a said:
Matt87":21xkyr4a said:
Apologies for resurrecting a bit of an old post, but did the BB survive the process in the end? I'm about to do this to an old Specialized Hardrock I have as the hacksaw method has failed, I don't have a BB tool and even if I get hold of one, I'm expecting it to be a bit of a sod to remove!

Cheers

You could saw the seat post off, cork the open end, flip the bike over and put the caustic though a bottle bolt hole. once you have thinned the post down a lot the ring the cork is in should come out easy.

I recently removed the remains of a seat post that had been hammered down the tube, I took pictures while I did it and video. I will sort some out if any interest.
Might be worth a go if I can get a funnel, would have to use something other than a cork to bung the end though I think, there's several slits running down the length of the post from where I sawed it so presumably it would run down these and around the cork. It'd be nice to know if the bb housing was sealed from the seatpost on the bike, then I wouldn't have to worry about taking it out, or trying to pour caustic into the tiny bottle cage bolt hole!

Would definitely be interested in those. How many times did you refresh the caustic soda solution, and over how long?
 
The seat post had been cut off and hammered down the tube, picture one isn't brilliant but you can just make out the top of the old seat post.

The cork is a bit of 19mm silicon hose with an expander in one end. An old head bolt and a few bit's of scrap plus a bit of threaded tapered scrap did the job. The cork just needed tightening by hand to seal, Picture two is clearly the cork.

The funnel is a bit of brake pipe, a scrap of tube and an old syringe. The brake pipe is ground to a taper, wrapped with ptfe tape and screwed into the bottle bolt hole, screwed in gently as it just has to stay in place[no threads were harmed in the ******* of this seat post]. The syringe is taped to the top tube, I just poured the caustic in to the syringe. Picture three and four show the funnel.

I mix caustic by temperature/feel, it doesn't want to be to hot, otherwise it will boil when it meets the ali. Because I videoed some of this I stuck a thermocouple in the caustic, to see how hot I was mixing it[just trying to be flash] about 50º with the caustic in it was about what I usually mix it to. The water had come out of my dehumidifier and was whatever the temperature was a few weeks ago.

I poured 100CC in to the seat tube, I poured it in at about 4pm. The seat tube got hot but stayed touchable, it was still hot a few hours later[still doing something]. It had started cooling down when I went in for dinner at 7pm so I left it overnight. The next day I emptied the tube and scraped the clag out of the tube with a welding rod. Then I re-corked it and filled it with cold water to flush as much of the crap out as I could. Picture five is what it looked like when I drained the seat post, what you see in the seat post is the clag, which scraped out with an old welding rod bent into a loop.

I mixed another 100CC of caustic. This time I mixed it a bit hotter, after measuring the temp I figured I was doing it a bit cold;-) I mixed it and the temp was 70º. I poured it in and it boiled and steamed out of the other bolt hole, damaging one of the stickers;-( Oh well not the end of the world. I poured a bit of cold water in to bring the temp down, only 10 cc or so. It still felt hot a few hours later and I gave it another few hours then drained it. I scraped the clag out of the tube with an tube with my trusty old welding rod and washed it with fresh water. I had some black clag in the lin bin I had drained it into, but no seat post anywhere.

I twisted a welding rod and some rag up, like a bottle brush and with a cordless drill I gave the tube a clean. I poured some lanolin/white-spirit
in the tube to stop it rusting. Picture 6 is the clean seat post

I would have to guess at the amount of caustic used, I would guess less than a few hundred grams. When mixing the caustic I just sprinkle a little in the water and then swirl the water around till the caustic is dissolved. If you chuck in too much it will boil and climb out of the pot, if your holding it it will burn your hand, I know from past experience. So you just sprinkle a little in.
 

Attachments

  • seatpost006.jpg
    seatpost006.jpg
    16.8 KB · Views: 774
  • seatpost005.jpg
    seatpost005.jpg
    25.8 KB · Views: 774
  • seatpost004.jpg
    seatpost004.jpg
    37.9 KB · Views: 777
  • seatpost003.jpg
    seatpost003.jpg
    30.4 KB · Views: 777
  • seatpost002.jpg
    seatpost002.jpg
    29.7 KB · Views: 776
  • seatpost001.jpg
    seatpost001.jpg
    24.7 KB · Views: 774
Cheers for taking the time to post all that, really helpful stuff! I'm thinking that's the way I'll do it, just need to get some bits together to make a similar funnel device, and something to bung the end as the top of the post is such a mess. Wondering if plasticine might be worth a go...?
 
I took the bottom bracket out to do my Richter and it made it all pretty easy.

I'd suggest you change the caustic soda pretty regularly, as it reacts pretty rapidly at first, but soon slows a lot as the concentration of caustic soda decreases.

If I remember correctly I ended up using one 500g container of caustic soda which cost about £1.50.

There's a few more details here:
http://www.retrobike.co.uk/forum/viewto ... 1&start=15
and a video here:
http://youtu.be/-dYnSVVDxrE

I wasn't bothered about the paintwork, but it would have been relatively easy to take more care and do it without any going on the paintwork.
 
I tried it upside down with the tube through the bottlecage hole technique, but after cutting the seatpost couldn't seal it properly so it all just ran through, didn't hang around long enough to melt much.

Best technique I found (shown in the vids on previous page) was just to fill the thing up, didn't have any affect on the BB, though clearly if you've got any aluminium parts on it they'll die of death.

All good fun eh what what?
 
Back
Top