A really really stuck seatpost

Dippydog2
Dippydog2 Posts: 291
edited August 2014 in Workshop
I have tried Sheldon Browns 14 methods (well 13 of them anyway).

Before I take the final step which involves a hacksaw and three weeks of pretending I am in the Shawshank Redemption, can anyone offer other methods?

It's an aluminium post, almost fully inserted into a steel frame. Seemingly immovable, but as I love the frame I want to get the post out. The intention is to strip and repaint the frame so I am open to "stringent" solutions.

Comments

  • Fit an expendable saddle. Hang the bike upside down and bang it down with a hammer
  • mr_evil
    mr_evil Posts: 234
    Since you said you tried 13 methods except the hacksaw, does that mean you already tried using the power of chemistry, and it didn't work?
  • Dippydog2
    Dippydog2 Posts: 291
    Mr Evil wrote:
    Since you said you tried 13 methods except the hacksaw, does that mean you already tried using the power of chemistry, and it didn't work?
    Have to admit I didn't do that one. Think I will try the hacksaw first.
  • DiscoBoy
    DiscoBoy Posts: 905
    Have you tried a blowtorch?
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  • Dippydog2
    Dippydog2 Posts: 291
    DiscoBoy wrote:
    Have you tried a blowtorch?
    Now, but everything I read says it doesn't work as the seat post just expands as well and remains stuck.
  • gethinceri
    gethinceri Posts: 1,575
    They are different metals so won't expand/contract at the same temp.
  • Dippydog2
    Dippydog2 Posts: 291
    Gethinceri wrote:
    They are different metals so won't expand/contract at the same temp.
    And therein lies the problem, allegedly. The aluminium seat post expands faster than the steel seat tube. I did read that heating the seat tube whilst cooling the post with dry ice or something can help, but it's very hard to make it work as they quickly balance each other out.
  • gethinceri
    gethinceri Posts: 1,575
    Hacksaw.
  • Heating it up is worth a try. Heating it up by itself won't free it, since aluminium expands more that steel. But... things heated up cool down again, and the expansion / contraction will mean that the two metals move against each other. That movement might be enough to break the bond, most likely caused by galvanic corrosion, that's making the seatpost stick.
  • t4tomo
    t4tomo Posts: 2,643
    Heating it up is worth a try. Heating it up by itself won't free it, since aluminium expands more that steel. But... things heated up cool down again, and the expansion / contraction will mean that the two metals move against each other. That movement might be enough to break the bond, most likely caused by galvanic corrosion, that's making the seatpost stick.

    ^^this, it's the fact that they expand and contract differently that is the key, not which expands quickest.
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  • Simmo72
    Simmo72 Posts: 262
    What worked for me was spray with wd40 and leave overnight. Then fit an expendable saddle and ram a long steel rod into the rails to get some purchase. Get a friend to hold the bike, or clamp it, then slowly use good old leverage to loosen the seat post, the longer the rod, the easier it will be. I used a weight lifting bar. I tired everything before this and it turned out to be very easy to move on a seatpost that had been stuck in a frame for over 20'years, no damage to post or frame, even the saddle was fine. Best of luck.
  • g00se
    g00se Posts: 2,221
    It's a chemical reaction between the aluminium post and the steel frame (galvanic corrosion). You need to break down the chemical bond between the two.

    Try, Coca-cola, Plusgas or this stuff (which worked wonders for me):

    http://road.cc/content/review/59182-effetto-carbo-move

    If that doesn't work and you then want to use a heat-gun or similar, make sure all the solvent has been cleaned away or evaporated.
  • lapavoni10
    lapavoni10 Posts: 146
    saw the setapost off near the top of the frame...long hacksaw blade with plenty of duck tape at one end (or an open ended hacksaw blade holder). Sit back and saw carefully...keep spraying the saw blade with wd40 as it will make the blade last longer and saw easier. You will be surpised how quick you will go through it...I reckon you will only get through a couple of beers before you are done.
  • rafletcher
    rafletcher Posts: 1,235
    Dippydog2 wrote:
    Mr Evil wrote:
    Since you said you tried 13 methods except the hacksaw, does that mean you already tried using the power of chemistry, and it didn't work?
    Have to admit I didn't do that one. Think I will try the hacksaw first.

    Dissolve out using caustic soda.
  • Dippydog2
    Dippydog2 Posts: 291
    lapavoni10 wrote:
    saw the setapost off near the top of the frame...long hacksaw blade with plenty of duck tape at one end (or an open ended hacksaw blade holder). Sit back and saw carefully...keep spraying the saw blade with wd40 as it will make the blade last longer and saw easier. You will be surpised how quick you will go through it...I reckon you will only get through a couple of beers before you are done.
    Had a go at this one. Cut a wide slot in the post and inserted a very long bar into it. No amount of force would move it at all, so I looked into cutting it out a suggested.

    The problem is that the post is inserted a long way down. Perhaps half the seat tube. I may be exaggerating but there must be 20cm or so of post in there so no way will a hacksaw work. And the side wall is very thick. It was hard work cutting the top off.

    With such a deep insert it may be that dissolving the whole post in Caustic soda is the only way. Watched how to do it on YouTube. Doesn't look like fun.

    A friend has a precision engineering company. Let's see what he comes up with.
  • lapavoni10
    lapavoni10 Posts: 146
    You need to cut two slots opposite each other so when you squash the seatpin it can collapse away Fromm the frame...if that makes sense?
  • on-yer-bike
    on-yer-bike Posts: 2,974
    Have you tried pouring Coca Cola in from the bottom bracket with the frame upside down?
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