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Re: Stuck seat posts & frame heating discussion

Posted: 21 Mar 2014, 9:13am
by 531colin
"Robbied" method..just one cut is so much better than the advice to "cut the post into strips" and remove the strips....
I "almost" wish I had one to do!
I have made a "reamer" from a flat wood bit and reamed a post out with a drill.....its brutal

Re: Stuck seat posts & frame heating discussion

Posted: 16 Sep 2016, 10:51pm
by timmymk
Hi all

I am new to the cycling scene and I am after some advise.

I have brought a boardman team carbon bike second hand it's in very good condition but only one issue the seat post has seized.

It's a carbon frame and seatpost.

I was going to try pouring hot water over it and spraying freeze spray with a little help with a mallet.

Any other ideas?

Re: Stuck seat posts & frame heating discussion

Posted: 17 Sep 2016, 11:44am
by fastpedaller
I'd not want to use a mallet!

Re: Stuck seat posts & frame heating discussion

Posted: 17 Sep 2016, 12:19pm
by Vetus Ossa
I did exactly as 531colin said in (3) to a REALLY stuck seatpost, worked for me but don't do it inside the house :wink:

Re: Stuck seat posts & frame heating discussion

Posted: 17 Sep 2016, 10:49pm
by timmymk
Vetus Ossa wrote:I did exactly as 531colin said in (3) to a REALLY stuck seatpost, worked for me but don't do it inside the house :wink:


I take it this method is ok to try with a carbon frame? And if I place the bike upside down and put the Ammonia in via the bottle bracket holes it won't cause any issues with the crank?

Cheers
Tim

Re: Stuck seat posts & frame heating discussion

Posted: 18 Sep 2016, 7:15am
by 531colin
timmymk wrote:
Vetus Ossa wrote:I did exactly as 531colin said in (3) to a REALLY stuck seatpost, worked for me but don't do it inside the house :wink:


I take it this method is ok to try with a carbon frame? And if I place the bike upside down and put the Ammonia in via the bottle bracket holes it won't cause any issues with the crank?

Cheers
Tim


NO. DONT put corrosive chemicals in a carbon frame.....I NEVER SAID do it on a CARBON FRAME....
Aluminium and steel corrode together, as I wrote. The products of that corrosion stick seatposts, quill stems, and bottom bracket units in frames and forks. Ammonia dissolves the stuff.....thats all.

I have no idea what is binding your carbon post into your carbon frame, but it isn't alloy/steel corrosion.
(there can be 2 seatpost binder bolts in carbon frames.....)

Re: Stuck seat posts & frame heating discussion

Posted: 18 Sep 2016, 1:43pm
by Vetus Ossa
I was actually referring to steel frames myself of course.

Re: Stuck seat posts & frame heating discussion

Posted: 17 Feb 2017, 3:38pm
by martin biggs
landsurfer wrote:If your seat post is stuck in a steel frame send it, or drop it off to me.
I'll remove it without any damage to the frame tube.
Removed 14 so far using a well practiced cutting system.
The good old "skin knife" process, as used for skin repairs on alloy airframes.
£20 / frame ....

Sorry, this is not a ' while you wait service', normal turnround 4 days. Because it hurts my hands ....


will have to remember your offer next time i get one that is stuck

Re: Stuck seat posts & frame heating discussion

Posted: 17 Feb 2017, 9:29pm
by ukdodger
I had the same a year ago. Even using repeated applications of plusgas, leaving overnight and going at it with a big pair of Steelsons wouldnt budge it. In the end I painstakingly (very) used a hacksaw blade with a handle made by wrapping the end with old rag and sawing it lengthwise inside the seat tube. It took all morning and a very sore hand. Even then it had to be prised off the sides. Now I cut the seat posts shorter in case it happens again.

Re: Stuck seat posts & frame heating discussion

Posted: 18 Jan 2018, 5:07pm
by Badger12
I used household caustic soda (sodium hydroxide) available very cheaply at Wilkinsons and other stores. This solution will only work with an aluminium seat post stuck in a STEEL frame. Remove the bottom bracket, cut off the seat post as much as possible and install a wine cork to seal the end of the remaining seat post. Also bung up the seat stays and down tube with plastic bag material, gaining access through the bottom bracket shell. Invert the frame and pour in a strong solution of the soda via the bottom bracket (I used a small watering can) taking care to avoid spilling it on the paintwork of the frame etc. WARNING: This solution is very dangerous at high strength so avoid splashing it around as it will severely burn your skin/eyes. At high strengths the chemical reaction with the alloy seat post will be very vigorous so only install enough to cover the trapped seat post as you will potentially get splash back up through the bottom bracket.
I experimented with various strengths and in the end went for a very strong solution and each time the reaction ended (a few minutes), I carefully removed the cork, drained off the solution, and repeated the process as the solution will become weak and far less reactive afterwards. You will find that the dissolved aluminium forms a soft metallic sludge each time within the centre of the seat post which you can loosen up with a screwdriver and remove very easily. This must be removed each time before re-bunging and pouring in fresh soda solution.
I applied the soda solution quite a few times and eventually all that was left was a thin sliver of seat post which I could bend with a screw driver and pull out with pliers. The frame paint remained intact and did not require a respray although you will have to experiment with solution strength as the frame can become so hot that the paint will be ruined.
I then rinsed the inner surface of the seat tube with a hosepipe and the job was done.You can see several videos of this method on u-tube. I used this on a steel 653 frame and it definitely works and is relatively easy but you need to take care.

Re: Stuck seat posts & frame heating discussion

Posted: 19 Jan 2018, 12:41am
by Brucey
Nice write-up that. BTW the reaction rate is very much temperature dependant; hotter is faster. The solution heats itself as the Sodium hydroxide dissolves and then again as it reacts with the Aluminium IIRC, but it will go a bit quicker if you use it whilst it is still hot.

One method that may be worth considering is to add warm water to the seat tube and then (using tongs, ideally) to drop the sodium hydroxide down the seat tube in solid form. This avoids handling the strong solution. However I suppose that if the reaction becomes too vigorous then there may be some splashing out of the BB shell.

Another thing that will speed the process is if you drill out the bulk of the seat pin before you start with the caustic soda. You can get rid of half or two-thirds of the problem this way, without much risk to the frame.

cheers

Re: Stuck seat posts & frame heating discussion

Posted: 19 Jan 2018, 3:53pm
by andrew_s
There's also The Seatpost Man, in Chorley
http://theseatpostman.com/

About £70, but will do carbon or Ti that you can't use caustic on, and you may get the post back, which could be of interest if it's an unusual or difficult to replace post like a Nitto S84