The Seatpost Man

[kingoffootball]

With them being fused together and metal being such a good conductor of heat, you can't heat/cool one without doing the same to the other.

Marc's method works because aluminium contracts faster with heat than steel, though as he said it can also work where both materials are the same, with the change in diameter breaking the bond between the two.

 

[marc two tone]

Re:

That's the principal, pretty much, the idea is to shrink things, not expand them, that would be adding to the problem (initially) then hoping the seatpost contracts enough to remove it.
Too much physics involved when heating the seatpost and seat tube up.
go simple! you need it smaller(seatpost),so shrink it, not flame it.

Also it's worth noting that extreme heat is required. 100 degree 'c' is nothing, my plastic kettle is still intact after my coffee earlier. you need 180 degs plus for metal to move sufficiently.
And the bond is hundredths of a millimetre thick, so it doesn't take much movement to break the bond.
The extreme cold will break the seal and keep it that way...know what i mean, think terminator 2. demise of T1000.
extreme heat will melt/liquify then cause the element to run around and solidify again(back to square one)...think solder and, terminator again.
cold will pull back things and keep them held back.

The freeze it out method buys you time n all. you can more or less make a sandwich whilst waiting for things to happen. with burn it out method you have to act fast during the expand and contract actions. barely enough time to grab a biscuit out of the tin.

I'm no Alchemist but next time i get a stuck post thrust in my direction...or a seized seatpost i will do a demo. easier and myth dispelling.
P.s although i rave on about the successes of this method, it, like anything has no guarantee for success, just a high success rate with virtually no mess/collateral damage.

 

[itscervo]

Marc's method works because aluminium contracts faster with heat than steel,

Well I never knew that :shock: , just goes to show, you're never to old to learn

 

[videojetman]

I will be looking at using Marc's method soon.

 

[02gf74]

With them being fused together and metal being such a good conductor of heat, you can't heat/cool one without doing the same to the other.

.

I would agree with you if heat travels through metal instantaneously, i kniw it doesnt so cant.

My reasoning for heating up first then cooling from the inside is that there will be bigger temperature difference across the join so a bigger change in diameter.

Since nobody has tried it, nobody can say it is better or worse than no heat.

 

[Uncle Grumpy]

What I'm about to suggest is either sheer genius, or a sure-fire frame crusher.

The first step in getting out a stuck post is to crack the bond.

Now, as for a lubricant, the best is a homebrew mix of 50/50 acetone and automatic transmission fluid. I mixed some up for my father who restores vintage agricultural equipment where rusted bolts are the order of the day.

Do the usual trick of filling the seat tube with the fluid through the bottom bracket shell and leave to soak.

Now here comes my whizz-bang idea.... If you're trying to crack the bond, there's no rule that says you have to pull the post out. What about pushing it back inside the seat tube to crack the bond?

Take a floor jack and set the frame/post and jack up under a frame of some sort (like the bearers and joists under the house, or even make up a steel frame. Put the BB sheel onto the jack and with the head of the seatpost against the top of the frame, give the jack a little press. Not a lot, you don't want to bend the frame.

But the pressure on it might just be enough to get the bond to crack, especially if you've got some penetrating lube in there first.

I wouldn't be putting a heap of pressure into it and killing the frame, but after time, the bit of pressure might get the bond to break and the post can then be pulled out.

Not saying there isn't an element of risk, especially if you're heavy handed, but it's another option, surely?

Obviously not for posts where the wrong size has ben jammed in or where the head of the post is against the top of the seat tube.

Grumps

 

[02gf74]

Pushing, pulling or twisting has to overcome the frictional forces between the two surfaces so I am am guessing it wont make much difference which way you try it.

Shrinking the post method involves not working against the friction and the forces involved i reckon are huge. You only need to look at what happens when water freezes in a confined space, pipes are burst, mountains are crumbled.

 

[jaypee]

Re: stuck seatpost removal

I'm definitely going to try the freeze method. I have three frames with stuck posts to get round to some time - am I likely to need three lots of this plumbers freeze spray or will one do all three?

Also I've been thinking about getting a vice anyway but would a heavy hammer to the top of the post actually be more effective at breaking the bond? Seems like it would to me but I'm no engineer/mechanic.

 

[marc two tone]

Re: stuck seatpost removal

I'm definitely going to try the freeze method. I have three frames with stuck posts to get round to some time - am I likely to need three lots of this plumbers freeze spray or will one do all three?

Also I've been thinking about getting a vice anyway but would a heavy hammer to the top of the post actually be more effective at breaking the bond? Seems like it would to me but I'm no engineer/mechanic.

Don't hammer sh#t (sounds better with american accent). it may break the bond but cause no end of stressing forces around your frame and distort your(needed to salvage) seatpost. crackety crack!

Anyway, 2 cans may do 3 bikes but use more spray where needed, less seatpost material down the tube, less the freeze spray...type of ting.

The whole practice, yes this is proven to work does answer paul's main concern...no harsh forces,fire, flood, disease or corrosive chemicals involved.

ALL...forget swinging from the rafters, industrial fluid, nuclear fission or hocus pocus, too many risks to factor in.

Just trying to keep y'all as safe as

I have no vise either! i have some mega big stilson wrech that i lay on the floor, trap with both feet then, rock the frame back and forth. worked twice now. both posts have had the elbow at the top once the micro-adjust assembly is removed, providing a handy grab point. straight posts may have to nipped up somewhat.

Just a practice note. once the spray is applied, give it a few mins, no rush as it will stay in ice form for a while. but not beyond 5 mins for example.
Give it some! don't tease it. push left and right like you mean it. it can sometimes feel like the seatpost is just twisting. it generally gives after 3-4 left to right shoves.

 

[legrandefromage]

One of my methods is to lay the frame on its side on the grass and jump on the saddle.

Sometimes, theres a loud crack to be heared, sometimes its the seatpost on the move.