I went one further and put the seatpost into liquid nitrogen whilst the frame was wrapped in hot tea towels - it didn't work. It was incredibly spectacular though, huge clouds of boiling nitrogen!
Local frame builder removed it for a fiver with fire!
Bike needed a respray anyway!
Quick stupid question, why wrap the frame in hot towels. I understand that you want to maximise the temperature difference but wouldn't the liquid nitrogen just freeze the towels too?
That's the problem with seatposts; they either come out or they don't, using any given technique, and (like jam jars...) one effort may have 'loosened it'. So its impossible to know just how seized the seat pin is/was, and therefore be absolutely certain which removal technique works best.
cheers
At the moment I just want the seat posts out, one I'd like to keep but the other I don't care about. Suspect both frames will be repainted/powdercoated depending on what I want.
I've had success with a spray freeze can - used loads of it for 3 applications but eventually it worked with some help from a water pump wrench turning the post.
What you might try, I have seen it work, is: take the BB out, bike upside down clamped at a slight angle from the vertical and (assuming you can see the open end of the tube in the BB) pour Coca Cola down the seat tube ..... it's very corrosive/penetrative and after quite a lot of applications might release the seat post.
The moral of the story is of course anti-seize/copper grease before insertion and repeated applications now and again.
Rob
Dry ice will be colder than freeze spray, I think. Hence the greater contraction, I hope.
About the coca cola thing, the bit is phosphoric acid, so could I just use vinegar or citric acid? Or any limescale remover type stuff.
I did not fit the seat post, the issue is buying frames second hand that need work.
If all else fails, and your frame is worth it, this guy:
http://theseatpostman.com/
Yeah saw him from torslandia, and am wondering how he does it. At the moment the seatposts are removed by magic
Freezing and heating and stuff didn't work for me. I ended up dissolving the seatpost with caustic soda. There's thread on here somewhere!
Tried caustic soda in the past, on a stuck stem on a moulton fork and a stuck seat post and ended up cutting the post and took ages as the post needed four cuts to get the post out.