Seat post fused into seat tube.

[stewie griffin]

I don't know what strength solution your using, I'm in Spain & the caustic soda comes in crystal form in a plastic bag.

I did my seat post about three years ago & can't remember exactly, but I did it within a day, I remember lots of heat being generated, replacing the mix a few times & ending up with a bucket of black scummy liquid.

Is your solution the strongest you can mix? I have no other explination why it would work for me & not for you. Maybe the stuff available here is somehow stronger than you can get?

 

[peanut]

no a slide hammer would attache to the seat post then the hammer part slides along its own piston. Have a google to see a picture. Its the tool that an engineer would use to free your post. They do no damage
http://www.toolspot.co.uk/product/9pc-slide-hammer-set?source=froogle

 

[stewie griffin]

A slide hammer can only apply the opposite force of a normal hammer, it goes without saying that if the post won't move in with a normal hammer it won't move out with a slide hammer either.

 

[Norm]

A slide hammer can only apply the opposite force of a normal hammer, it goes without saying if the post won't move in with a normal hammer it won't move out with a slide hammer either.

Which is true, but could you not use more force as the impact won't be directed onto a welded joint?

 

[Zippy]

A slide hammer can only apply the opposite force of a normal hammer, it goes without saying that if the post won't move in with a normal hammer it won't move out with a slide hammer either.

Yes, exactly. A slide hammer would work against a tight seat post, but in this case the oxide between the aluminium and the steel (CroMo) will not crack. There needs to be a shearing or pairing force between the two.

I think my next plan is to use a hacksaw and I hope there is not too much post down in the frame; can't tell without sawing off the seat post end.

Tune in tomorrow for the next chapter of The Stuck Seat Saga - Chapter 3: "Hacked Off".

 

[Norm]

Tune in tomorrow for the next chapter of The Stuck Seat Saga - Chapter 3: "Hacked Off".

Post pics, please.

 

[peanut]

A slide hammer can only apply the opposite force of a normal hammer, it goes without saying that if the post won't move in with a normal hammer it won't move out with a slide hammer either.

The reason the post wouldn't shift inwards with a hammer blow is because the shock was absorbed by the tyres etc.

I don't understand the resistance here to using the correct tool for the job ?the one that is made for the job and causes the least amount of damage .

What is the point of spending 10-15 hours messing about with something causing damage to the frame and finish when in 10 minutes in an engineering workshop would have it out easily for £5.00 or no charge .

Beats me especially when none of those that argue against trying a slide hammer have ever used one ?

 

[stewie griffin]

Beats me especially when none of those that argue against trying a slide hammer have ever used one ?

I own two, one which I've used professionally for the past 24 years.

Again, if a blow from a "normal" hammer won't knock the post in even a fraction, a slide hammer won't move it in the opposite direction.

 

[Zippy]

its going to cost you an awful lot more than £50.00 to refinish the frame .

I'm cutting through the seat stem not the frame.

As for engineers down here in Cornwall, its like speaking to guys from Barter Town in Mad Max - it would cost me a lot more than £5.00 to have them machine it out "properly" and they'd do it dreckly as well . Probably end up with the seat post drawn cleanly without a scratch and a big bag of bits that used to be my bike. No sir, I'll trust to meself methinks

 

[NickM]

I got round to attacking my friend's stuck seatpin last weekend. In this case, Normfest Super Crack didn't work (not all that Super, then...).

Maybe the stuck seatpin would have submitted to a long, strong lever, but I haven't got one, so AFAIAC it is a lost cause unless sawing it out works.

 

[Zippy]

I think maybe the vice would have worked if I had drilled through the set post and threaded a steel bolt through so the bolt stopped the stem rotating in the vice. Trouble is aluminium lubricates itself with the filings that come off and just rolls in the vice jaws.

I have been funnelling caustic soda through an open drink bottle lug a half pint at a time (downtube slightly downward toward the seat post) and no more than a dribble comes back out - all black, so something is happening. Trouble with this is as the reaction goes, the caustic is dribbling back out and there must be a time when the caustic solution is in the inside of the stem but no longer covering the end of the stem so no longer eating at the oxide which is sticking the two together (if you see what I mean).

I have an idea that if I remove the BB and turn the frame upside down I could pour in a pint of caustic and as the level goes down it will still be covering the stem bottom for much longer.

Think I'll try this before taking a hacksaw blade to it.

 

[Amanda P]

Zippy, I would persist with the caustic for a while before resorting to something more drastic. The sawing solution is going to be really, really tedious if it works at all.

(To free my seat post, I made a slide hammer just for the job (not a particularly nice one, but that's what it was). It didn't work - there's only so much force it can apply, limited by the amount you can accelerate the weight along the slidey bit. You can swing a claw hammer through a longer arc and deliver more force on the end of the seatpin with it - although you are thumping it in the wrong direction).

The seat post will be hollow, and much of the caustic you're pouring in will be filling up the hollow part. Only a tiny bit will permeate into the tiny gap between the seat post and seat tube. The caustic there will quickly be neutralised by the reaction. So changing the solution frequently may help.

You're right, too, that twisting will really help. I drilled a hole Frankenstein-bolt fashion through the end of my seatpost, put a steel rod through and twisted on it.

The rod bent! But at least this way I was able to twist and pull at the same time without using a vice - and if you don't have a vice, you're at a big disadvantage.

I would say bring it over to my workshop and we'll have a go at it there, but Cornwall to York-ish is a long way to ride, especially with no saddle...

 

[Zippy]

I have been funnelling the caustic soda in through a drink bottle lug and keeping the downtube just off paralell so the nasty stuff doesnt end up in my BB. Trouble is as soon as the reaction boils off I think I am left with the caustic inside the hollow seat stem instead of just over the end where it needs to do its business.

My next plan is to remove the BB, sit the frame upside down and completely fill the downtube so the bottom of the stem is covered with a good few inches of NaOH and just burn the b*gger out! Along with twists and taps and yes - Peanut - the frame is valuable to me and no - I don't like to be beaten; well - spanked sometimes but that's a different thread :-)

 

[zacklaws]

I've read quite a bit on this subject quite lately as it seems to be quite common this problem and pops up all over it seems, last night I went to bed and lo and behold, I read about it again.

Knowing that I would not sleep thinking if my bikes where OK, I got dressed went downstairs and checked my old Trek 1.2, which I have not touched the saddle post for about 6 months, and guess what it was stuck solid! Twenty minutes of twisting finally got it moving but I was making that much noise in the shed I would have woke the street up.

This morning I got up and it took 3 hours of twisting and spraying with penetrating oil, just raising it a mm at a time till it finally came. From now on though once a month I will check them and regrease, and will also be very wary if I ever buy a bike off Ebay as it also could have a fused seat post when I receive it.

 

[NickM]

Your real name must be Justin Time!