Seat post fused into seat tube.

[stewie griffin]

Zippy, if this runs to 168+ replies you'll have the official "most replies in Know how forum" title. (might have had it already if some posts hadn't been deleted!)

Good luck.



Just noticed "Jeltz" is the author, sorry Zippy.

 

[psychalist]

Just arrived here and gone through this amazing story (all 14 pages) - my interest - because of a similar predicament and knowing that a few years ago I did all the vice/bench/wrench/heating/cooling tricks to no avail. I then continued to ride my old hack with the seat a bit low - tell tale soreness above the knees on longer rides.

As my old hack is just that and a part time standby, it wasn't that important but it's come time to decide whether it continues in another form or passes on to a new life via recycling. Like Zippy, I don't like being defeated by a mere mechanical, but sense the odds are stacked against me getting the post out. Feeling along the seat tube, I can discern some swelling due to corrosive expansion. I concluded destruction of the post was inevitable but have not tried the sawing down or chemical approaches. This thread has enlightened me to the trials ahead should I decide to go for it. Many thanks to Zippy and all his helpers for the great information.

P.S. I inherited an old road frame and that has a stuck handlebar stem - evidenced by the hammering marks on the underside - why is a simple rebuild never possible? ;-)

 

[Zippy]

err remove the wheels form the frame and put them in sthe shed would stop that happening.

Great tip - the wheels come off then?

Note to psychalist: a couple of tips I would pass on:

1. Check your rear struts before pouring lye down the downtube to see whether they are hollow and drain out toward the end of the struts - caustic soda will find its way through the struts and all over your wheels and derraileur! I would definitely removed the BB and check out where any exit holes are from the down tube and seal them with polythene (caustic doesnt seem to react with this). If the caustic is kept in the down tube and topped up, you should be through the seat post in a focussed weekend.

2. If you do go down the hacksaw blade route, I can recommend a Stanley hacksaw blade which fits into a Stanley knife handle. The blade is tough enough for the job and is thicker and more rigid than a hacksaw blade and you have a positive handle to grip. If your seat post is in by no more than 7 inches, this is a superior tool to a hacksaw blade.

- and if you use caustic soda, wear gloves and goggles - the reaction with aluminium is hot and agressive!

Here's the downtube now it has had the oxides, and odd bits of aluminium that wouldnt chisel off, boiled off in a saturated solution of caustic soda . Just a bit of paint touch up and I'm ready for a new seat post.

 

[jeltz]

Zippy, if this runs to 168+ replies you'll have the official "most replies in Know how forum" title. (might have had it already if some posts hadn't been deleted!)

Good luck.



Just noticed "Jeltz" is the author, sorry Zippy.

Great seeing how Zippy's been getting on but I'm just sitting back watching the monster I created now

 

[rich p]

Great seeing how Zippy's been getting on but I'm just sitting back watching the monster I created now

Troll

 

[psychalist]

Just one other question. Early on in the thread Sheldon's advice of using ammonia was dismissed in favour of caustic soda. Has anyone tried ammonia or is it just not available in the strength needed? Presumably the reaction is different. Any explanations?

Cheers, P

 

[Zippy]

I know I know!!

Ammonia works by breaking down the aluminium oxide between the alu and the steel frame, whereas caustic soda works by literally dissolving the aluminium stem out of the steel downtube.

The thing with caustic is to make sure the down tube is sealed from outlets such as your rear wheel struts and crossbar (once the caustic breaks through the seat tube, the crossbar will be open to the downtube). Take the BB out and pack it tightly with polythene dust sheeting to plug any openings there. With the tube completely sealed off you just keep topping up the strong, saturated, solution of caustic down the tube until the seat tube dissolves or gives up so you can pull it out.

Ammonia didn't work for me as the oxide had sealed the seat post in so tightly it couldnt work down between the two metals. Household ammonia is not strong enough for this game anyway.

If I had this to do again, I would have removed the BB and plugged the downtube as above and just keep tipping in caustic. I hadn't realised much of my lye was draining away from the site through the hollow rear wheel struts. Once I realised this and plugged everywhere up, the solution made short work of what was left.

Final word: goggles, gloves and protect your forearms and feet against splashes. Keep the shower on standby! Good luck!

PS: it is a steel frame and an aluminium seat post isn't it? That is vital , otherwise you'll end up with a clean steel seat post and no aluminium frame!

If both are steel, then its loads of PlusGas, a strong vice and some careful twisting.

 

[psychalist]

Yes old school steel and alu seat post. Thanks for the tips. Obtained caustic soda today. Will wrap up like a SOCO before starting ;-)

 

[Zippy]

 

[weevil]

I'm pretty new here and have just sat and read this thread from start to finish. Or, rather, from the start to here. I can't believe it's really all over.

Zippy, I salute your incredible perseverence. Very, very well done that man!

I'm now minded to have another stab at removing a stubbon crank arm from the Dawes which is languishing in my garden. The only reason it's not gone to the local tip is that I keep forgetting to take it, but now I feel my attempts at removal hav been somewhat half-hearted.

Finally, for anyone with a very tight (but not atomically bonded!) seatpost, how about this as an alternative to the slide hammer and claw hammer: an SDS drill; the sort which allows one to use the hammer action without the chuck spinning to facilitate chiselling/chasing. Plenty of percussive action in one of those beasties.

 

[grumpyoldgit]

I used a drill & an adjustable reamer,took less than an hour