Monday, January 21, 2013

That it should come to this

A lovely old 1997 GT Palomar has wandered into my stable, by a somewhat circuitous route (but that's a story for another post) Right now, the issue at hand is more dramatic. Stuck. Aluminium. In. Steel. %&*%$

..and the seatpost and saddle-clamp have parted ways.....

It's a matter of basic arithmetic:

Aluminium seatposts + steel seat tube + H2O + (2013-1997) = Trouble x Plenty x n+1

The saddle clamp has un-inserted itself from the seatpost, so no sideways leverage anymore. Next option is  my array of home made pullers combined with the CO2 shrinkage trick , but I fear it may end up being another equation:

NaOH + H2O + Aluminium  = Aluminium Hydroxide + Hydrogen + unharmed steel seat tube
              60 minutes

Yup. The observant faithful will have noticed that there is no longer a seatpost in the equation. Which is more or less what's supposed to happen.

Let the last resort remained untried. If you have connections with higher beings, please make appeals on my behalf (If George Carlin heard me say that, I'd be in shit)

Source: Sheldon Brown of course

  1. Drastic solution, contributed by Matt Duff: Sodium Hydroxide - AKA Caustic Soda. ONLY FOR AN ALUMINUM SEATPOST IN A STEEL FRAME AS FAR AS I KNOW. It will destroy an aluminum frame. It won't affect steel, and as far as I know it won't affect most plastics.
    DISCLAIMER - don't attempt if you are unsure about anything and always use thick rubber gloves, face mask, overalls, boots. Sodium hydroxide will eat away at the aluminium but it will also eat off your skin faster than anything. [Getting it in the eyes can cause blindness. See precautions here. Have a source of running water, and for good measure, a bucket of water ready, in case of an accident. -- John Allen]
    Saw off the seat post at the top of the tube and bung it up with something plastic. You must do this because othersies, liquid would flow out when the caustic soda eats through the seatpost). Make sure it is liquid tight. Remove bottom bracket. I'd suggest removing anything else off the bike that is aluminium, and covering up any decals you may want to save. Take the bike outside and set upside down on a patch of dirt away from kids and animals.
    Measure out 200g of sodium hydroxide powder into a plastic cup. Fill a 750ml bottle with 500ml of cool water.
    Put on all the safety gear - the mix will get hot, produce fumes, and may splash. Don't let it touch your skin!
    Place the bottle of water into an empty plastic bucket - the bottle may overflow so you want to catch that stuff. Slowly pour the 400g of powder into the 750ml bottle - use a thin wooden stick to stir it. It will get hot - make sure there is no powder left in the bottom of the bottle.
    Using a funnel and a thin hose pour in a small amount of the liquid mix into the frame of the bike through the bottom bracket . Maybe about 100ml at a time - wait about 5 minutes and it will start bubbling and gas coming out. When it starts to slow down pour another 100ml in Continue this so that the liquid is in the bike tube for about 1 hour. [No fire or flame nearby -- caustic soda releases hydrogen gas when it reacts with aluminum. -- John Allen].
    Break the seal on the seatpost hole - warning! lots of liquid will come out. Be covered up and check where it is all going to flow to. Run fresh water through the frame thoroughly to make sure it is all out Clean the area - dilute any that is on the ground with lots and lots of water Throw away any containers and wash tools really really well
    I found I had to do this twice. The second time I had to plug the top tube to stop the liquid flowing down there. [You might tilt the frame so liquid will not run down the top tube -- John Allen] Finally all that was left was a thin sliver of seat post. Hope this is good information. Cheers!
Spoke Divider
"Free at last! Free at last! Thank God almighty, I am free at last!"
--Dr. Martin Luther King, Jr.


  1. Yikes. That sounds nasty.

    Sure, I'll have a chat with God for you, but why do I have the sneaking suspicion you might be inclined to try the aluminium hydroxide anyway, if only for the dramatic effect?

    Could it simply be that I've known enough guys now to recognise a closet chemist when I see one?

  2. Babble, Babble, No, "Higher Beings" were invoked. Don't bring God into this lest we offend ;)

    I think it's actually more of an ego thing (the willingness to go chemical on the seatpost, that is). My CV already has several removed seatpost stories (un-inserted, unstuck, ex-serted ??) by methods various. The sawing one even uses a magnet to catch filings so that you know when you're removing steel frame and not aluminium seatpost...;(

    At the end of the day, how many people do you know with "Chemical seatpost removal specialist" on their CV? Huhhh?

    And hey, look after that leg of yours.