Stuck seat post with unusual frame - Successful Update

[fastpedaller]

The best spray I've ever found for releasing things........ Rust dissolving spray (or similar name) from Lidl (surprisingly). I bought it last year and it is REALLY good.

[old_windbag]

Saw this video where machine building extrusions have been used with a puller to draw out the seat pin. Looks good but not sure if it would shift a well seized post...

https://www.youtube.com/watch?v=X-EfsLG8np0

Then there is the seatpostman who charges about £60 IIRC but it's getting a frame to him http://theseatpostman.com/ but worth a look for others in similar situation perhaps especially if you live close to him.

Possibly use a slide hammer after all the penetrating fluids have been applied and allowed to sink in.

Then the fearful last resort( and a respray ) , Caustic Soda( if ali seatpost in steel frame ).

[Cyril Haearn]

Why do seatposts stick? How may one prevent them sticking?

[Brucey]

Why do seatposts stick?

very occasionally it is simply dried grease (with no corrosion) but usually it is corrosion. The problem is that the oxides invariably want to hydrate themselves with as much water as possible; by weight the crud that is sticking everything together is mostly water.

How may one prevent them sticking?

take the thing out and recoat it with something (e.g. copper-ease, grease, waxoyl) regularly enough to prevent corrosion from setting in.

cheers

[Geoff.D]

I'm assuming its an alloy post in a steel frame. I have had some success using a mineral oil release agent in a spray can. Called "Freeway" if I recall. You could try deforming the seat pin at the top of the frame to allow you to add a pool of release agent and allow it to work its way down. A bit of heat sometimes helps later when you come to remove the pin. The final resort is to cut the seat pin off and carefully use a hacksaw. A tip I was given was to cut a slot in a length of wooden broom handle so you could fit a hacksaw blade leaving only a couple of mm proud. This reduces the risk of cutting into the frame tube and gives a convenient handle

BTW I think there is a whole thread devoted to this problem in the too good to loose section of the forum.
viewtopic.php?f=5&t=16716

It's not creating a pool of penetrating oil at the top that's the problem. The pin is at its lowest point and there is a small lip around the inside of the tube to create such a pool. What I really want to do is get oil inside the tube to create a pool there as well. I want to take this "long soak" method as far as I can, before I embark on any drastic methods. I've read the thread you link to, rjb, and recognise the hierarchy of methods.

(BTW there is a propriety hacksaw blade holder, with a handle a bit like a Stanley knife handle. I inherited it from my Dad )

I realise you are talking Tandem here, have you tried clamping the errant post in a vice and using the frame as a lever?
(Or getting a Stilson Wrench on it?)
But before your do, I'd soak it in Plus Gas , despite you percieveing that it's not going to penetrate it is very good at doing just that.
Have a look at Sheldon Brown / Stuck Seatposts too , a plethera of information.

Yes, I've tried both these,"949arnold". The pin has a bonded head, which doglegs to the rear to carry the seat rails and clamp. So it gives something to clamp/vice/stilson onto. I'm loathe to really heave on the frame until I've done the the long term soaking.

Drill through the bottom of the BB shell and then through the top. Won't do any harm at all - the shell bottom often has a hole for fitting derailleur cable guide.

Drill through the bottom of the BB shell and then through the top. Won't do any harm at all - the shell bottom often has a hole for fitting derailleur cable guide.

Have you tried using a slide hammer to get the post out?

I've seen a video of the slide hammer technique, Pete. I don't have immediate access to one, but I might consider it if Plan A comes t nought.


Thanks you all for your suggestions and information. I'll eventually report back on my success (says he with optimism !!)

[bikerwaser]

After having serious issues with one of my seat posts being stuck

I tried hot and cold and various sprays left overnight to seep in but nothing worked.

Then I (carefully ) used a small blow torch on it.

I was concerned about the paint but kept it just right going back over it again and again to build up the heat slowly.

It worked a treat with no paint damage.

[pete75]

Then there is the seatpostman who charges about £60 IIRC but it's getting a frame to him http://theseatpostman.com/ but worth a look for others in similar situation perhaps especially if you live close to him.

Possibly use a slide hammer after all the penetrating fluids have been applied and allowed to sink in.

Then the fearful last resort( and a respray ) , Caustic Soda( if ali seatpost in steel frame ).

It doesn't harm the paintwork at all and is a fairly quick and simple process.

First tried it on a bike I bought for next to nothing because the previous owner had actually split the seat tube trying to get a stuck post out. Thought I'd have a go just to see how the process worked. Shame about the frame as it was a quite nice Orbit Carraway. Anyhow I just blocked the hole from seat tube to BB shell with blue tack along with the frame split , filled it with a caustic solution which I changed a few times and the seat post was gone in about 3 days. No paintwork damage.
Earlier this year I bought a Roberts Roughstuff frame at a fairly low price because it had a stuck seat post. To make matters worse it was a suspension post. Tried Plusgas and then a slide hammer but it it just pulled the suspension part out and left the non suspension post still in the frame. It was thicker than a normal seat post so took 5 days to dissolve with caustic, again with no paint damage.

[Geoff.D]

Earlier this year I bought a Roberts Roughstuff frame at a fairly low price because it had a stuck seat post. To make matters worse it was a suspension post. Tried Plusgas and then a slide hammer but it it just pulled the suspension part out and left the non suspension post still in the frame. It was thicker than a normal seat post so took 5 days to dissolve with caustic, again with no paint damage.

I'm not averse to the caustic soda method, Pete, but it brings me back to my original post ........how best to gain access to the inside of the seat tube?

I was concerned about the paint but kept it just right going back over it again and again to build up the heat slowly.
It worked a treat with no paint damage.

Thanks for this, bikerwaser, I might actually have a go because the paint work is in no great shape anyway

[Cyril Haearn]

Does caustic soda actually dissolve the seatpost, turn it into liquid?

[Brucey]

yes!

cheers

[Brucey]

I'm not averse to the caustic soda method, Pete, but it brings me back to my original post ........how best to gain access to the inside of the seat tube?

you are scrapping the seat pin so just chop the top off; you can keep the level of caustic soda solution at the height you want this way.

I was concerned about the paint but kept it just right going back over it again and again to build up the heat slowly.
It worked a treat with no paint damage.

Thanks for this, bikerwaser, I might actually have a go because the paint work is in no great shape anyway

The paint will start to fail at a temperature of 120-200C depending on the type of paint. Transfers at a temperature less than that. A safe way to heat to a useful temperature is to wrap rags round the seat post, and slowly empty several kettles full of boiling water over them. Like any such technique, it may work if the seat pin is not too badly seized. Not all seat pins are equally seized in by any means, and it is worth trying things that are low-risk first even if they are not guaranteed to remove the seat pin.

cheers

[GuyBoden]

Sometimes, there is a chemical reaction between a Steel frame and an Aluminium seat post over time, so unfortunately "Free It" oil will not move it.

Caustic soda works well with stuck Aluminium seat posts in a steel frame. Takes about a week, if you top up the Caustic Soda at regular intervals. I'd wear rubber gloves and eye protection, it burns skin easily.

[fastpedaller]

OP - any update?

[Geoff.D]

OP - any update?

Well....... "yes" and "no", fastpedaller. Thanks for asking.
On the "yes" side .....I've decided to go down the caustic soda route - cut across the bonded-in saddle clamp, drill down to the seat tube and top up with the caustic soda until it's done (as suggested by Brucey). I've been and bought the stuff.
On the "no" side.....I'm well into my winter project of converting an old town bike into an bike, and just haven't got round to the tandem frame.

I'll post when I've succeeded. Hopefully before Christmas.

[Geoff.D]

SUCCESSFUL UPDATE - notes for anyone interested

It's taken over 6 weeks. I cut off the seat post just above the frame and drilled a 10mm hole into it. The post was of the swan neck variety, with a solid alloy insert (the neck) at the top. Luckily this only went down for about 60mm. But it did mean that the post, at this top section, was a tube with 7.5mm walls.

I mixed the caustic soda at 200% of the the concentration recommended for drains. I found two problems after starting. Firstly, when I filled the caustic soda to the top the effervescence meant that liquid bubbled out over the top. I wasn't unduly worried in terms of the mess, but it meant that overnight the level of the liquid would be down below the thick walled portion. So, the section that need most attention from the caustic soda was getting the least. Secondly, the temperature has been quite low in this neck of the woods, and would surely have slowed the chemical reaction. But, I persevered and was gratified by the black sludge that came out every time I changed the solution. Bit by bit the hole at the top got wider, and as it did so there was less overflow. The wider neck allowed the effervescence to bubble away quietly without upsurge.

Coming back from Xmas in Edinburgh last week, I found the hole was just wide enough to get a hacksaw blade down. I had hoped not to have needed to resort to it, but the walls of the tube were still 5mm thick. Too slow for me. I cut slots in the top section, creating segments. Gave it a couple of nights with caustic soda, and then gently broke the segments away from the walls. I say "gently", but they were still a PITA. Segments snapped of with a bit of waggling and fatigue. Once away, I was down to the thin walled section of the post, which was pretty much dissolved by now.

What have I learned?
Well....caustic soda works, but not easily managed in a narrow necked tube. It's slow. Cutting segments works, but it's crude. And (with hindsight), dropping the swan neck right down because your son has short legs is only a good idea - if you remember to keep the post free.