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stuck seat post thread #99,182: The oversized seat post

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stuck seat post thread #99,182: The oversized seat post

Old 08-03-15, 06:01 PM
  #1  
mrv 
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stuck seat post thread #99,182: The oversized seat post

howdy
Picked up a GUNNAR Rock Hound the other day.
Stuck seat post in the frame. Cut off by the previous owner: https://lh3.googleusercontent.com/8g...s=w693-h923-no

I didn't know to check for a possible bulge in the seat tube until after I picked up the frame. I knew there are a number of ways to remove the post (dissolve, melt, saw), so I thought I would figure it out after I got my hands on it. (I think the expression is READY! SHOOT! AIM! .. whatever)

My question is do I need to worry about frame damage after I get the post out? Of after I melt the post out will the frame likely 'spring back' (if the material was not taken beyond the yield point....).

Anyway - I'm going to go fire up the propane torch and try to melt this thing out of the frame.
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Old 08-04-15, 07:30 AM
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my guess is that it's permanently deformed. But I don't see any bulge in your pic
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Old 08-04-15, 08:54 AM
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Originally Posted by unterhausen View Post
I don't see any bulge in your pic
it's pretty slight. I can feel it. I'll put my calipers on it later today and see what I measure on the O.D.
I was soaking it with penetrating oil, and putting a pipe wrench on the little bit left sticking out - no joy. Once I felt the slight bulge in the tube, I decided to give up on that route.

The flame temp of a propane/air torch is just under 2000C, with aluminum melting at 660C. So I'm thinking I'll go that route

Any idea of the % carbon in Reynolds 853 tubing? I'm curious where I'll be on the iron/carbon phase diagram... approximately.
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Old 08-04-15, 09:24 AM
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You won't melt the post with a propane torch, the heat will diffuse away. Looks like there is little room to hook up a slide hammer. Try slotting the post into section with a hacksaw or reciprocating saw and pry the sections off.
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Old 08-04-15, 11:50 AM
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you'll be at the "fubar" point on the phase diagram. You have to squint to see it in most textbooks, but it's on there.

It's possible that the bulge is actually a transition from a topper to the seat tube itself.

A local builder used to drill seat posts out on his lathe. I think he stopped when he wrapped one around the toolpost. I tried it on my lathe and it didn't work too well, the chips deformed the seat tube. Replacing that tube is on my list.
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Old 08-04-15, 11:57 AM
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plug the post pour in liquid wrench from the BB shell end
[ lots of other chemistry experiments have been posted when others made their stuck seat post inquiries in the Mechanic's forum. ]

DIY tools ? might be able to run a length of all thread through, then put a jam-nut pair on it thru the BB shell . heavy washer that just fits in the seat tube Inside , to catch the bottom edge of the stuck seatpost

then make a slide hammer with some heavy pipe on the part of the all thread still sticking up above ( maybe add some handles welded on the Pipe?)

and bang against a couple more nuts jammed together .

OH [edit] I'm going Im say the water bottle boss protrudes into the seat tube bore..
that has to be gotten around to engage the bottom of the sawn off seat post..


Physical Properties:
if anything freeze the aluminum colder to contract it, and heat the steel frame to expand it .

Last edited by fietsbob; 08-05-15 at 11:34 AM.
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Old 08-04-15, 03:36 PM
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It might be time consuming, but If the seat post is not in too deep, you could try to cut the seat post vertically into 1/3 segments with a hacksaw and pop the pieces out.
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Old 08-04-15, 07:56 PM
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@Brian25 - it's in about 140mm. It's definitely time consuming. It might be the way I go.

@Fiestbob - i'm leaning towards the chemistry experiment. It might be a Caustic Soda Weekend at Der Wiener-Schnitzel Haus!

@unterhausen - ummmm...... can MAPP/air get me in the squinty region ?

@tuz - MAPP won't melt Al either, but it softens it up a bit.

hmmm. ... slide hammer. i'll have to ask around or try the washer thing.
good times.
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Old 08-05-15, 09:21 AM
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I think my lbs uses cola.
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Old 08-05-15, 12:03 PM
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Originally Posted by unterhausen View Post
I think my lbs uses cola.
Pepsi, Coke, or RC? Maybe JOLT would do it? But first, a couple of root beers....
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Old 08-05-15, 02:28 PM
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see "stuck seat post" Ggl: https://www.google.com/search?q=stuc...hrome&ie=UTF-8

Sheldon's page tops the list http://www.sheldonbrown.com/stuck-seatposts.html
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Old 08-05-15, 03:14 PM
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Originally Posted by mrv View Post
Pepsi, Coke, or RC? Maybe JOLT would do it? But first, a couple of root beers....
coke and pepsi both use phosphoric acid as a primary ingredient. I think that's what does it. But it's most commonly used on carbon bikes. I don't think root beer has any effect in this instance, except being delicious
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Old 08-05-15, 03:31 PM
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Originally Posted by fietsbob View Post
see "stuck seat post" Ggl:
- yea.... the original question was do I need to worry about frame damage from an oversized seat post?

Looks like there's maybe 0.5 ~ 1.0mm increase in seat tube diameter due to the seat post. I can feel it and measure it inconsistently, but it's not visible.
I'm down with Sheldon Brown, he's the man! (may he rest in peace!)

The jab saw is an interesting idea. Better than just barely hanging on to a hack saw blade. Looks like Milwaukee makes one that cuts metal.

And yes, @unterhausen, I recommend 'Not Your Dad's Root Beer'. Just.... stop and one.
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Old 08-05-15, 03:46 PM
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I've had to deal with twice in the last year. Chemistry only works if it's a matter of the the aluminum oxidizing to the steel frame. Coke and Ammonia work great but if the seat post is too big, then it won't make a difference. Plus, it can mess up your paint. Do not hammer it, you can damage the frame.
The best thing to do is cut the post using a fractional hack (10 inch) in four places as deep as you can without touching the frame. It takes a while. Pour liquid wrench down the sides and let it sit for a day or two. Then use a vice wrench to twist the post out but avoid gripping the frame.
If this doesn't work, heat the seat post and then cool with ice water immediately. The aluminum heats quicker and cools quicker than that Reynolds steel frame. It should create a gap.
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