Originally Posted by
grumpus
I have never tried it, hence the "?", but I can imagine that some seatposts would not react well to that sort of violence. I will however bear it in mind for future use (it might be handy for those situations where the post is not actually stuck but needs a lot of persuasion).
"Actually stuck" is precisely the situation where the air hammer technique works best.
We had to avail ourselves of the pneumatic-hammer method only a few times, but it never failed, and never damaged the bike. That can't be said for some of the methods have been described on Bike Forums when the topic has been broached before, such as using caustic chemicals or clamping the top of the seatpost in a vice with the frame upside down and having two mechanics energetically twisting the frame back and forth.
The top of the seatpost gets battered, of course, but the seatpost almost never survives, regardless of the method used to remove it. The upsides: seatpost comes out, bike is undamaged, job is completed in about 10 seconds.
Edit: if anyone happens to try the air-hammer approach, be sure not to forget to use thick mechanic's gloves to hold the bike up off the ground while the air hammer is doing its stuff, as I mentioned in my earlier post in this thread. Clamping the bike in a stand or otherwise firmly immobilizing it would result in much of the impact from the air hammer being absorbed by the clamping apparatus. (Experienced mechanics reading this understand why that's important.)