UKH

Classic case of steel bike with alu seat post - post now stuck.

Have squirted WD40 down the post (from seat end) to try and loosen it, now that its not freezing will try with boiling water, and maybe the hairdyrer to try and free it.

If that doesn't work will try the clamp, rotate the frame thing - but what then?

Be loathe to try and hacksaw the seat post out (its not a dropper, just a cheap seat post though)

Would the local bike shop be able to offer anything else?

What do other folks do when faced with this problem?

Lots of heat has helped me in the past......then if possible clamp the seat and use the extra leverage of the bike.....worth a trip if you have a good bike shop locally though!!

I once took saddle off, turned bike upside down and dipped seat post into liquid nitrogen to shrink seat post as aluminium shrinks more than steel. That worked. Maybe a mix of ice and salt will do the trick.

Seek the oracle

https://www.sheldonbrown.com/stuck-seatposts.html

Good luck - I've got a steel bike with a stuck steel post to have a go at when I get the time...

https://theseatpostman.com/

Not used them myself but many have, successfully

I wish him all the best in his business, but I cant help wondering what sort of bike techs working out there cant get a seat post out.

I know a few folk who've used the seatpost man, successfully. I think sometimes the post can get almost welded in by galvanic action

Warm the frame below the height of the post stuck inside, so you get the frame expanding more or quicker than the post. If the very first bit of the post was tampered slightly, wd40 or little oil down inside then turn the bike upside down for a while, it won't penetrate far but every little helps. 

Sounds like you're fortunate enough to have only visited decent bike shops...

I used to work in a bike shop when I was at school, to subsidise my BMX habit. Also several friends either own or work in bike shops.

Frame upside down with the seat post well and truly clamped in a big vice, the post will get trashed. Loads of WD or any loosening spray in through the bottom bracket so it runs down the seat tube and soaks into the fused bit. Alternative to bb removal is to take bottle cage bolts out and squirt in through them. Leave for a day or two to soak in. Give it a good twist and a monster pull at the same time, best done while standing on the workbench (!). If no joy try heating the seat tube as hot as you dare and repeat the twist/pull squat lift routine. Still no joy the plumbing freeze kits might work on the seatpost while heating the seat tube (I haven’t tried this but the theory should stack up!).

Tried all that, nothing worked. Eventually decided I'd actually damaged the frame , so...

... bought new bike

Forget WD40, ATF and acetone may work,  for aluminium in steel caustic soda.

Don't heat, or at least let it cool down before trying to remove, as aluminium expands quicker than steel.

1. Secure bike to immovable object. 

2. Attack car jack to seat post. 

3. ???

4. Profit 

I once did this with no discernable movement, so took the bottom bracket out and poured in a load of dry ice. Heat gun on the outside and some more twisting and it came out surprisingly easily. Frame still going strong to this day! 

If pulling it out doesn’t work, then I would squirt the inside of the seat tube liberally with WD. Invert and revert the bike several times to get the WD all around the tube below the stick post.

Hacksaw the seatpost off flush to the tube.

Then using a hammer and chisel( my favourite combo of tools for any DIY task) tap the stuck post down into the tube to sit below the new one.

I'm not recommending this but...

Many, many years ago I faced a similar issue and used some sort of jab-saw to saw (VERY CAREFULLY!) a series of 3 or 4 grooves down the inside of the seat post (having already chopped the top off the seat post, leaving a couple of inches protruding).  I spent ages sawing carefully outwards from the inside of the seat post towards the frame, stopping often and peering down the inside with a torch to check that I hadn't reached the frame yet.  Finally, once I'd sawn as deeply as I dared I took a pair of mole-grips and crushed the protruding section of seat post.  The post folded into itself and away from the frame (bit like the opposite of peeling a banana...).  This gave me enough of a gap between frame and post to soak with easing oil and leave for a couple of days.  Eventually the mole-grips, easing oil and more brute force had the post out.

I wouldn't do it these days (wouldn't have the time!) but 35 years ago it seemed like a good idea...

One of my old bikes had a stuck seat post and my Dad took it to a friend who was an engineer. He took the saddle off, rested the BB on a block and hit the top of the seat post with a hammer. That dislodged it and then it was easy enough to pull it out 

Not the same thing, so maybe not useful, but I had an alu post stuck fast in a carbon frame and used a co2 fire extinguisher on the post, then brute force to the point of fearing I was about to crack the frame. Then BANG, job done.

I went to my local fire station to ask where I could get a co2 extinguisher and they were more than happy to 'test' one of theirs.

Adimittedly, I'm assuming that if you exploit the hearing and cooling difference between alu and steel it will have the same effect?