Corroded seat post

[ashridge]

Just discovered an exceedingly nice colleague who has lent me his not-often used RC200 F5 while mine comes back from being re-anodised and is rebuilt.

The problem is, in the 9+ years it has languished in his shed the Syncros seat post has well and truly corroded into the frame.

I read on www.sheldonbrown.com/stuck-seatposts.html that ammonia unsticks corroded aluminium in a jiffy. Sounds logical.

Has anyone tried this because I can't get the ammonia down the seat tube around the post, so removed a bottle cage bolt and tried filling the seat tube with the bike upside down. Only managed to flood the shed with ammonia and choke myself!

Any tips gratefully accepted...

 

[SF Klein]

Since the seatpost is toast anyway, what about hacking off the top of it so that you can see straight through into the seat tube area. Then plug any holes in the bottom bracket area and fill the seat tube with ammonia.

 

[bagpipes]

Try removing the bottom bracket and funnel it through the opening at the bottom of the seat tube while the bike is upside down. Be prepared for some to leak through the post and seat clamp.

Don't cut the post just yet as you may be able to use the top end to grip with vice grips once it begins to loosen.

Short of that, you may need to drill it out. I've done it; very time consuming and very tricky but it can be done.

 

[SF Klein]

Agree not to cut the entire top portion off. I was just thinking of a way to make it possible to get the ammonia in there. Good idea about the bottom bracket as long as there's an opening to the seat tube somewhere in there. Also, if the seat post is stuck, I'm guessing the bottom bracket wasn't maintained that often and might also pose problems.

 

[JeRkY]

:!: :!: :!: :!: :!: christ almighty...yes amonia will eat aluminium, no I havnt had any luck with it my self...but please for the love of god remember that the RC200 is also made out of aluminium and you certainly dont want to be tipping amonia into it! The wall thickness of the butted tubes is MUCH thinner than the seat post... :!: :roll: :shock: :twisted:

insert any other smilies that draw attention to this post before you risk your very nice mates, very nice frame.

This method is recomended for alu posts in steel frames, however as mentioned I have never had any luck with it. Last resort is to chop the post shorter then use a pad saw or hack saw blade to caefully cut through the stuck portion of the post in the tube, not easy, takes time and concentration but will work.

 

[magas]

Last resort is to chop the post shorter then use a pad saw or hack saw blade to caefully cut through the stuck portion of the post in the tube, not easy, takes time and concentration but will work.

totally agree

the tool:

Kalloy 30,0 mm seatpost - wallthickness of 2,8 mm :shock:
4 hours of hard work - thanks to the seller who leave that bike out in the rain - night & day :evil:

 

[messiah]

I did the hacksaw trick recently with a carbon seatpost in an Alu frame - about four hours sounds right. I split the seapost while holding the head in a vice and twisting the frame - so I cut it off short and got buzzy.

I scuffed the frame in a few places but cleaned it up okay a new seatpost went in fine.

If I was doing this with something as delicate/lovely/expensive as a Pace frame I would very carefull indeed :shock:

 

[Splatter Paint]

NOOOOO! ammonia in somebody else's aluminium frame!

Assuming you've not done too much damage already, then invert the bike, pour penetrating oil in the bottle cage holes and leave for 24 hours. Lay the bike down flat and then wrap towels around the seat tube and pour on loads and loads of boiling water. With a handy assistant, one use a large ajustable spanner on the seatpost head and the other pulls with all thier might on the saddle, bracing your feet against the frame for something to push against. With luck it'll come out with the twisting and pulling motion. For extra assistance, I think some 'plumbers freeze' on the seatpost will help to keep it cool while the frame heats up. Concieveably you could put an ice pack on the seatpost too.

SP

 

[SF Klein]

Ah, didn't realize it was aluminum inside aluminum. If that's the case, agree with the above (penetrating oil). You could couple that with applying dry ice to the seatpost for a short period of time - to make the seatpost contract a bit just before trying to twist it (or the frame). It won't have any benefit if both the seatpost and the frame get cooled the same amount by the dry ice.

 

[stew-b]

great pictures magas!! they should be put in a sticky post for other people