Seat post fused into seat tube.

[Amanda P]

good point Norm. Most people don'r realise that the more you do up a vice the more it will squash the seat pin out of round and actually make it tighter in the seat tube.

It is a good point.

However, if the seatpin is the type with the seat clamp cast onto the top, gripping the clamp part would not crush the circular-section part.

But it sounds as if Zipply doesn't have this type of seatpin. I'm guessing it's just an alloy tube that takes a separate seat clamp on its top? Correct, Zippy?

It is alloy, isn't it? Is it dull, alloy-looking metal, or is it coloured? Some alloy seat posts are anodized. Or is it shiny chrome-plated steel?

How much seat post is showing above the frame? If there's lots, crushing the top probably wont' deform the part of the tube near or inside the frame's seat tube. If there isn't much, crushing it will deform (oval-ise) the part inside the seat tube, which will make it harder to get out, so don't crush it!

If it crushes easily, it's thin, soft, drawn alloy, and you may find that, when you twist the frame with the seat post in the vice, you just twist and tear off bits of the seat tube: bad news.

Whacking the seat post down into the frame may seem like going the wrong way, but Peanut's right: it's about cracking the collar of gunk that's gluing the post in place. Once you've cracked that seal, it may move back up more easily than it did before. Or it may not - but it's worth a try, you've little to lose at this point. You can apply a lot of sudden force on the top of the seat post with a lump hammer!

After a soak with caustic, try all the "brute force and ignorance" tricks again - twisting (twisting is important), pulling, hammering down. Once it starts moving, in any direction, even fractionally, you're winning.

 

[Zippy]

Thanks guys. I take your point about not cutting flush - I suppose I was thinking that the aluminium would be burned out by the lye or would need to get down the tube as far as possible if sawing, so wouldnt need leverage (I was aiming to pry the sawn strips away with a screwdriver). Will leave enough to grip with plumbers wrench, hit with hammer etc.

Norm - thanks. No need to be cross - I'm the one who's cross - with me not greasing my tube in the first place!

Right - onto my local vet!

 

[Zippy]

But it sounds as if Zipply doesn't have this type of seatpin. I'm guessing it's just an alloy tube that takes a separate seat clamp on its top? Correct, Zippy?

That's correct Uncle Phil.

It is alloy, isn't it? Is it dull, alloy-looking metal

It is slightly shiny alloy metal (not completely grey dull like scaffold polees but defintely not shiny steel or chromed. Monkey wrench teeth dig grooves into the soft metal and metal dust accts like a dry lubricant in the vice. Must be a good thick stem as it wouldnt crush or deform in the vice.

There's about a nine inches of stem out of the frame so plenty of leverage there. Perhaps need a cheater bar on the monkey wrench for more leverage and I'll try giving it a whack now I know the stem is sacrificed. I am worried about shocking the steel frame though this way and breaking a weld.

 

[Amanda P]

It is alloy then.

Your frame's joints should be substantially stronger than the hold the frame has on the seatpost!

When frames fail, it's usually from cracks adjacent to the joints, or because, in a crash, the tubing bends or breaks somewhere other than at a joint - again, usually next to them. It's quite rare for joints themselves to break, because the additional thickness of the weld added to the tubing makes them the thickest, strongest parts of the frame - as long as the weld or braze is done right.

As long as they are (a weld should be stronger than the tubing itself, as it's the thickest part of a tube), the seat post should give way before the joints do.

It is a steel frame? (I'm sure we've been over that, but it's been a while now...)

 

[Zippy]

It is a steel frame?

It is CroMoly.
I think I'm going to give it a good whack with a heavy claw hammer - I can feel it coming on! That's before and then after I fill the downtube with caustic; having drained it out - I don't fancy hammering a tube full of lye and getting it in the face!

 

[Zippy]

Gave the old seat post a good morning whack with a claw hammer - several good two handed whacks actually - nothing.

So I mixed a good strong brew of caustic soda and funnelled it into the down tube through one of the drink bottle lugs. Bike is pointing vertical with the down tube slightly running down to the saddle end to keep the caustic out of my BB.

Must be doing something 'cos I filled it until the lug was weeping fluid and it keeps draining out (against gravity), so must be reacting with the aluminium seatpost.
----
Well the end of Day One at the "stuck seat post house" and I'm looking at a black puddle of spent caustic soda under the bike where the reacted water has oozed out of the drinking bottle lug. Topped up with more caustic solution and we'll see how it goes tomorrow.


I understand the reaction gives off Hydrogen - isn't that the one that explodes with a sqeaky pop? Fortunately I dont smoke and there's plenty of ventilation!

 

[Zippy]

Sunday morning and the damn stem is just as stubborn as before. Tried whacking down with a claw hammer and twisting with the plumber's wrench. Now I'm prpearing my next pint of caustic - wondering how long it would take to melt this thing out?

Weater's not brill just lately so I may as well take my time and keep pouring. Interesting for anyone following my down this route - when it came to tipping out the old caustic solution from the frame, there was hardly any there. Presumably all used up int he reaction so it may be necessary to keep topping up throught he day to keep the solution over the stem end in the downtube where it will seep slowly between the two metals. Otherwise the caustic is just eating away at the inside of the seat stem; a slow process indeed.

 

[raindog]

This thread is amazing. I've never heard of anything quite like it. I feel for you, really I do. Good luck.

 

[Zippy]

Thanks raindog.

I just noticed how many seplling msitakes I made in the last post. Maybe the caustic soda is eating away at more than my seat post!!

 

[raindog]

As long as it's only your spelling and not summat else.

 

[Norm]

... seplling msitakes ...

I'm surprised the "percussive maintenance" didn't work. Sorry if this is a dumb question but what was the bike on when you smacked it? If it was on it's tyres, the chances are that the rubber took the shock which was intended to free the metals.

 

[Zippy]

Norm - the cycle was on its tyres when I gave it the percussive workout and also with me holding the frame in my hand while tapping down sharply.

To be honest I was worried about rupturing the welds or bucckling the frame if I stack the down tube on wooden blocks and hammer down the downtube.

Makes me want to have another go with the hammer!

 

[Norm]

You'll have to follow your own counsel on this ultimately, Zipster, as it is your frame so only you can decide how hard you want to hit it.

The idea behind the hammer is not to smack it too hard (thus the recommendation to use a claw hammer rather than a lump / sledge hammer) but to "shock" the chemical join apart. This might not need much more than a tap but if it is in your hand or on it's tyres, then that shock wave is dissipating through what is essentially a flexible mount.

However, and I think this is the crux of your concerns, if that seat tube and the frame are fused too well, the join could be as strong as the welds on a 40 year old bike.

Ideally, securely clamp the downtube in a rigid frame, so none of the force is going through a weld. Plan BB, support under the bottom bracket with wooden blocks.

Remember, you aren't trying to force the two apart, you are trying to send a shock through the corroded faces to separate them. It's the same sort of theory as sudden heating / freezing, just get them to move anyhow.

Which makes me wonder about the chances of getting a slide hammer onto it. Has that been suggested yet? That shouldn't put any stress through the frame or the welds, although you'll have to stump up £25-ish for the hammer, or find someone who'll lend you one. If you've written off the seat post, drill a hole through it, push a pin through it then you could hook a slide hammer onto that and give it a yank.

 

[Norm]

Ah, right, sorry, I lost track half-way through this thread.

I hope that no-one would understand my "ideas/suggestions" are nothing more than that.

I'm wondering why HGF doesn't like the slide-hammer though.

 

[Zippy]

However, and I think this is the crux of your concerns, if that seat tube and the frame are fused too well, the join could be as strong as the welds on a 40 year old bike.

I think this is what I have found. I doubt the slide hammer idea would work. Presumably the slide hammer goes between the bolt drilled through the seat post and the frame somewhere?

I tried a good dozen sharp strikes with a claw hammer with the BB on wooden anvil (blocks) and also with a lump hammer to see if I could drive the post down the tube but my pencil line shows it hasn't moved at all.

I think the next and last thing to try now is the hacksaw down the frme tube. I am thinking to cut the saddle square off the stem, cut the seat post down the length towards the frame criss-cross and prise them down (like peeling a banana) so I can get my hand right down to the mouth of the downtube when I am hacksawing and leave them on so I can use them to lever the sealed bits off the frame, cush, pull, chisel between; wahtever it takes.

The most caustic solution is not working though it must be doing something as 2 pints have gone in and only a dribble came out and there's no puddle, just a dribble of jet black (Aluminuium Oxide?) liquid.

Any last ideas before I get the hacksaw out tomorrow?