Amani576

Wow... my first new thread in quite some time.
Anyways.
As some of you may remember, I have an old Burley tandem with a frozen seatpost. I've tried so many ways to un-freeze this thing I don't even know why I care anymore. And my most recent attempt is based on oxalic acid. As all discussions go on the subject, it's said that OA will dissolve aluminum, so I figured why not try.
Well, I mixed a 10% blend (1oz OA to 9oz of water [seat tubes don't hold a lot]) and after a week I mainly have a yellow goo on the inside of it. So... Either I used to strong of a mixture, I need re-mix it/flush it more often, I need to use a heavier mixture, or my efforts are misguided.
Keep in mind I have tried everything short of reaming the tube out, twisting heavily, sawing out the inside, ammonia... I mean, this was my last ditch effort. If this doesn't work I'm gonna have to talk to a machine shop, and if it gets that bad I may just have to re-evaluate with my girlfriend if it's even worth it.
So... Any input?
Thanks all.
-Gene-

wrk101

While OA attacks aluminum, it is more about cosmetic damage. If you want to dissolve it chemically, then you need something strong, like sodium hydroxide. Unfortunately, sodium hydroxide will also attack the paint, so it really is an extreme measure. Personally, I would put a cheap saddle on it, put the saddle into a bench vise, soak it for a few days. I see some mention using ATF and acetone. I have not tried it.

I usually use PB Blaster, but I see a lot of recommendations for Kroil.

Personally, even though I am a chemical engineer, I would not be using sodium hydroxide at home. And destroying the paint would make it even less desirable.

After the last ditch effort above, I would be cutting it out (very carefully).

Typical testimonials of Kroil instead of PB Blaster. You will find discussions on Kroil on many other forums: cars, etc.

https://www.discoweb.org/forums/showthread.php?t=1781

Amani576

See... I've already tried cutting it out. There is no longer a top to the seatpost. I tried and tried and tried the twisting measure. I broke a saddle doing that.
I'm almost 100 positive that I have a clean cut all the way through it, and it's so stuck it won't move. I really don't know what to do. I used an entire can of PB Blaster as well.
And I'd have no problems using something that damages the paint as it's going to the powdercoater when I get this done.
If you suggest not using sodium hydroxide, that's fine. But would it cost less money that having a machine shop ream it out? And how long would you think it would take to dissolve it? And is it dangerous to me if I were to use it?
-Gene-

OH! Okay... Looked it up. If you'd said Lye I would've known immediately.
I have considered using that, but lye scares me. I may not have choice, at this point, though.

southpawboston

i think a machine shop would be able to ream it out for not a lot of money, but have you tried sawing it vertically from the inside? if you were to saw off the exposed section of seat post except for the last 1/2", would what's left below be hollow? if so, then you could insert a hack saw blade down in the hollow section and slowly saw your way through the post wall, vertically. once you've cut through the post, you could crimp the exposed section with a vise-grips, which will have the effect of reducing the seatpost circumference.

toytech

if you only cut a seam in one side, try a matching seam opposite the existing one, you should be able to peel it free with a punch after that.

Amani576

If you'd like a list of what I've tried.
1) When it was discovered - twist the **** out of the saddle attached to the seatpost.
2) Heat
3) More twisting the **** out of the saddle.
4) PB Blaster and twisting
5) Saw it off and start cutting out the inside
6) Try to pry it out
7) More PB blaster and cutting
8) More prying
9) Literally dump ammonia into it (the bottom has no hole)
10) More twisting and cutting
11) More ammonia
12)More prying
13) OA

And here I am. Maybe I moved too quickly into harder stuff, but I really tried other ways, NOTHING worked or happened.
So, realistically, I have 2 options. Lye or have it reamed out. Both are good options that will fix it, but one is likely to be way more expensive than the other.
-Gene-

As far as I can tell I have cut two lines down it. It does not let go. And when I've tried punching or crimping it out, it seems to do damage to the top of the seat tube (The collar area) more than anything.

-holiday76

got a close up pic of what you're working with right now? How much of it is sticking out?

atmdad

Find a machine shop, I can't see it costing more than $10 - $20 for them ream/drill that sucker out. Maybe even check out the local HS metal shop, contact the teacher to see if he wouldn't be interested in making a couple of bucks after school one day.

K. Olsen

This.
Maybe make a 2nd cut opposite side as well.

gaucho777 

My advice:
1. First, queue up Kurt's video.
2. Turn the volume all the way to 11.
3. Put the seatpost in a vice and use your might.
4. Use a crow bar to apply upward force as shown in the photos on page 2 of the link above.
5. Persevere.
6. Repeat steps above as necessary.

rhm

Okay, lye scares you; and it should. It may still be the solution.

I'm thinking as a first step you need to find a place where a little fugitive lye won't a complete and catastrophic disaster. A bath tub, maybe? Next, you need to get some kind of a plug into the tube, below the remains of the post, so the lye doesn't leak through, run away, and cause problems. Then you make a weak lye-water solution and pour a little of it into the tube, and wait. Ideally you use only just barely enough lye to do the job so that by the time you're done, the base has been neutralized by the aluminum it has dissolved.

That said, how about one of you scientist type guys critique my method?

randyjawa 

Trust me, when I suggest that patience is the operative word in a "cut the seat post out" exercise. Caution is also a pretty good word. This is How I Remove a Stuck Steering Stem, a seat post is removed the same way.

You probably have not cut all the way through the post. Also, you might have to make three slots, and at least two will have to be all the way through. Even if there is no top to the seat post, you can still get it out, once the cut is complete.

You might also have to try lifting the top edge of the plug you are creating with two or more slots. Be CAREFUL! Do not damage the thin wall tubing. I use a very small screw driver to lift the edge and then work at it, then sawing again, then lifting, until the piece finally releases. It takes me less than an hour to do this with nothing more than a pair of gloves, a hacksaw blade and my little screwdriver.

Good luck and, honest, you will succeed with patience and caution.

Again, patience. The procedure is fool proof, but you must be cautious and not damage the frame set metal. It can be done. I do it quite often.

Or, you can use my other method. Twist the post so hard that the drive side seat stay breaks free of the seat tube lug Yup and that is why I usually just cut the post out. One destroyed frame set is enough for this good looking old guy.

The damaged frame set - a late sixties Torpado with through the frame cable routing.


Torpado_51_ChromeBlack_Full_Side..jpg Torpado_51_ChromeBlack_Full_SideLeft..jpg

Iowegian

You mean the seat post is still solid at the bottom?

I just used lye for the first time on a stem. Very effective and quite scary. It will bubble, hiss, get hot, etc and dissolve the AL into nothing. Be careful.

Amani576

I think part of the problem is that I've run out of patience.
I've had the frame for a over a year now and it's still stuck. I try about once every week or two for a few minutes to over an hour. I think I'm just gonna have to resort to some harder method (like lye) or have a machine shop do it. I think my will to do it myself is gone after having exhausted to much effort on it for no results.
-Gene-

Amani576

It's a welded tandem, than the bottom bracket shell underneath it is the eccentric. There's no hole from the bottom of the seat tube into the eccentric. So it's just a straight tube I can fill up.
-Gene-

ecsjr

Freeze-Off made by CRC is what I used on the last stuck seat post I had.

After soaking in penetrating oil and all the tugging on an attached seat I could do, I sprayed this stuff on it and the post started moving in 5 minutes. The Freeze-Off seemed to make the parts cold as I sprayed it on, and supposedly that makes the different metals move different amounts. Not sure if that is why it worked, but I was very happy it did.

Bought it at the car parts store. And I have been using it on all my stuck/rusty car parts as well.

Good Luck

nlerner

Well, today I passed on a stuck-seat-post project to another BF-er as I tried all of the methods you did, Gene, plus trying to dissolve it with lye, but now admit defeat. I think the machine-shop solution might be the best option.

Neal

ScottRyder 

Oil of Wintergreen. It works, really.

Scott

sjpitts 

It is my understanding that for an AL seatpost in a steel frame, that heat is the wrong approach. I think AL has twice the coefficient of thermal expansion of steel. If you heat up the seat post, it will expand more than the steel, and make the problem worse.

So I think you are better off trying to cool the seat post. The steel tube will shrink, but the post will shrink more. Buy 2 bucks worth of dry ice, put it in a plastic bag, and wrap it around the seat post. When the seat post is good and cold, then put the seat post in the vice and twist away.

I have broken two seatposts loose that way.

bigbossman 

I see a small flaw in your proposed solutions......

sjpitts 

Thats ok, I am really just an idea guy. I leave the details to others.

gaucho777 

^Apparently, I misunderstood about the top of the seatpost being cut off. So the seatpost is cut off at the frame and there is no more exposed seatpost to grab or put in a vise?

Amani576

About an inch. And it's all chewed up from vise grips.
-Gene-

southpawboston

is there a hole in it? if not, drill down until you reach the hollow section. enlarge the hole until you can fit a saw blade in. then saw away!

gaucho777 

Gotcha. Even with a lye solution, won't it be necessary to still have a secure lock on the post to apply enough outward force? I've never tried lye, so I wouldn't know personally. Maybe it's destined for a machine shop to have it reamed.

Good luck!