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Thread: Unwelding/Fusing a bike seat from the frame

  1. #1
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    Unwelding/Fusing a bike seat from the frame

    Hey guys,

    I have a problem I need help with, as I have next to no experience with metal working. I came across a guy here in New Orleans who is refurbishing vintage bikes. He has a couple from Japan and Germany that (he said) has an an aluminum seat insert fused into the steel frame. That's how they were made as opposed to these days, which normally the seat insert slides in and out of the frame allowing for adjustment. He says he has tried everything including dry ice to get the insert removed from the frame. Unless he can get this doen the frames are useless, but i'd really like to be able to get one up and running. Are there any techniques out there anyone would sugget without hurting the frame? I was thinking maybe using a hole saw drill bit about the diameter of the aluminum, although I was concerned about the dammage not to mention that it would probably take forever!

    let me know guys,

    Thanks,

    - Chad

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    Re: Unwelding/Fusing a bike seat from the frame

    This covers all the bases:

    http://sheldonbrown.com/stuck-seatposts.html

    Slap some anti-seize on whatever post you reinstall.

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    Re: Unwelding/Fusing a bike seat from the frame

    The link that farmall provided looks pretty good. If none of those suggestions work, sadly there's only one final option. A plasma cutter to the frame. Then a good weld back repair job followed by body work and paint.
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    Re: Unwelding/Fusing a bike seat from the frame

    Quote Originally Posted by farmall View Post
    This covers all the bases:

    http://sheldonbrown.com/stuck-seatposts.html

    Slap some anti-seize on whatever post you reinstall.
    Actually I don't think it does......
    I believe he's meaning the seat post are not the adjustable/removable type. If I'm not mistaken, the Alum. seat posts were inserted into a hot steel down tube, steel cools, shrinking and "clamping" the seat post in place. Excess post was trimmed and the seat was mounted to the post. Saves the weight of a camping set-up, all be it a dumb way to go, but very boutique chic for those getting a custom bike made. Modern carbon frames sometimes epoxy the Alum. post in.

    As for the holesaw, your asking for trouble. The Milling machine folks on here would know better than I, but having a big namba-jamba Milling machine, with a clamping fixture, with an annular cutter or boring bar. That is the accurate, have lots of dough to throw at this project method. For the on the cheap but fairly safe way one could try is a die grinder with a long stem bit. Grind away the Al. as close to the steel as you dare and try CAREFULLY prying the rest out. But don't get it too hot as it with damage the paint, if you are trying to preserve it. If not concerned about the paint, with the frame hanging upside down( BB up) use a torch to melt out the Alum..
    Maybe, you might be able to use big twist bits in a hand drill to shave out thin layers of the post. The bits would have to get increase in size by a fraction for each pass. Bits that big are going to be expensive. Don't know if they could be rented.
    Or if your on the dirt poor and pig-headed budget, pop the ipod on and grab a hand file!
    I'd love to see picks of this frame. And to know if I'm right in this case about the post being mounted this way. I've only seen one bike with a seat done this way. Custom touring rig. Japanese tourist riding the West Coast. He happened to stop at our local coffee haunt. Spoke little engrish but our smiling, gesturing and bowing cut the language barrier. This thing would give the snobbiest Frenchman a chubby.
    I'm a recovering bicycle junky. Been clean, and a bit fatter, for years. You could always email one of the Tom's( Brodie or Ritchey), or Cunningham. You don't say where you are, but I've see work from some of the boutique builders in Seattle and they are real top notch folks.
    Bert
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    Re: Unwelding/Fusing a bike seat from the frame

    bert the welder said the easiest rout get a big twist drill of a close fit off of ebay should be less than 20.00 or harbor freight and then cut the aluminum off flush with the steel frame and start drilling. The aluminum is softer and the bit aught to follow the steel tube if you are up to it should be able to do it with a hand drill low RPMs. will not be fun but doable.
    Do not argue with an idiot. He will drag you down to his level and beat you with experience.

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    Re: Unwelding/Fusing a bike seat from the frame

    I've actually chopped them off at about 4"above the frame, & used a sawzall straight down the seat post making a vertical slit on 12:00 & 6:00 positions.

    I'll usually tack a piece of stock to both pieces just so they don't slip downward once cut
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    Re: Unwelding/Fusing a bike seat from the frame

    Strong acid or alkaline liquids usually attack aluminium severely, but are quite a bit less damaging on steel. Might be a route worth investigating.

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    Re: Unwelding/Fusing a bike seat from the frame

    This happens quite often. The folks at Retrobike.co.uk/ have many clever solutions. One of them using diet coke to disolve the seizure. Mention where you were recommended from and you will get lots of help be sure to name the brand of bike if you can.
    Last edited by shovelon; 04-22-2012 at 10:46 AM.
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    Re: Unwelding/Fusing a bike seat from the frame

    Quote Originally Posted by idacal View Post
    bert the welder said the easiest rout get a big twist drill of a close fit off of ebay should be less than 20.00 or harbor freight and then cut the aluminum off flush with the steel frame and start drilling. The aluminum is softer and the bit aught to follow the steel tube if you are up to it should be able to do it with a hand drill low RPMs. will not be fun but doable.
    I did this once with a 1" Silver & Deming drill bit, with a 1/2" shank, in a slow turning hand drill. It really wasn't that difficult, and worked just fine.

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    Re: Unwelding/Fusing a bike seat from the frame

    cut the post off and slit the aluminum from the inside with a hacksaw blade, then pry,twist, and pull till the post comes out

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    Re: Unwelding/Fusing a bike seat from the frame

    I think both the sawzall or hacksaw would work. I'd be tempted to go 12, 3, 6, and 9 o'clock. But don't get to gung-ho with the prying. This ain't gas pipe. Probably pretty thin.
    Still hoping he posts pic's.
    *popcorn......*
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    Re: Unwelding/Fusing a bike seat from the frame

    That's if it's corrosion seized.


    Quote Originally Posted by shovelon View Post
    This happens quite often. The folks at Retrobike.co.uk/ have many clever solutions. One of them using diet coke to disolve the seizure. Mention where you were recommended from and you will get lots of help be sure to name the brand of bike if you can.
    200amp Air Liquide MIG, Hypertherm Plasma, Harris torches, Optrel helmet, Makita angle grinders, Pre-China Delta chop saw and belt sander, Miller leathers, shop made jigs etc, North- welders backpack.

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    Re: Unwelding/Fusing a bike seat from the frame

    Quote Originally Posted by bert the welder View Post
    That's if it's corrosion seized.
    I am thinking it is galvanic corrosion.
    Weld like a "WELDOR", not a wel-"DERR"
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    Re: Unwelding/Fusing a bike seat from the frame

    I would try a pencil grinder and carbide burr , that is if its not too far down in the steel tubing..

    are you sure its not pinned together anywhere?
    Last edited by brucer; 04-26-2012 at 04:08 AM.

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    Re: Unwelding/Fusing a bike seat from the frame

    Hole saw? Nope, not likely.

    Whether the aluminum seatpost is corroded in place or purposely put into the steel frame with a shrinkfit, removal is pretty much the same. Mechanical means or chemical means.

    Strong alkali will dissolve aluminum and not have much effect on the steel, but will strip or damage the paint.

    Mechanical choices using various abrasives or cutters to remove the aluminum will work, don't just go in and try to go too fast and out of control and then end up wrecking the steel frame.

    Pretty much covered in the link above from Sheldon Brown's site.
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    Re: Unwelding/Fusing a bike seat from the frame

    Carbide burr on an extention, the Al is soft and will clog the burr up, clean it up as you go and grind the Al post out of there. Course then ya got the second problem of putting a new one in and holding it in there?

    Bikes are cool, you've got our attention... we like weird stuff like this... ok, now fork over the PICTURES or we'll go away bored
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    Re: Unwelding/Fusing a bike seat from the frame

    Sure, but we are talking on purpose here, I believe.
    I a case of galvanic or corrosion, would the coke penetrate seized seat post ya think? Come to think of it though, it is nasty stuff. Guess if it did, it would be a BB repack.
    Quote Originally Posted by shovelon View Post
    I am thinking it is galvanic corrosion.
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    Re: Unwelding/Fusing a bike seat from the frame

    Papa, I fear he may be a one hit wonder. I really want to see this frame.
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    Re: Unwelding/Fusing a bike seat from the frame

    I wonder are we talking Al/Fe interaction chemically or this a swollen upstem from heat and then install the Al seat pipe... I've never heard of that but who knows... Schwinns for me, the older the better...

    How U been Bert haven''t seen a post in awhile?
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    Re: Unwelding/Fusing a bike seat from the frame

    Let us know if any of the above works. I had the same problem once, two bike shops told me it was a common problem and they have never heard of a way to free up a stuck post.

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    Re: Unwelding/Fusing a bike seat from the frame

    Quote Originally Posted by PapaLion View Post
    I wonder are we talking Al/Fe interaction chemically or this a swollen upstem from heat and then install the Al seat pipe... I've never heard of that but who knows... Schwinns for me, the older the better...
    I'm still banking on my assertion that it's been heat shrunk into the seat tube as a build technique, but I could be wrong in this case.

    Quote Originally Posted by PapaLion View Post
    How U been Bert haven''t seen a post in awhile?
    Hello Papa. Been busy getting summer inventory built and trying to get into a local gift shop that I know would sell very well. This time of year sucks for me more than usual with the season change. I have pretty severe depression and am in "the blackness" a lot so I try to refrain from posting too much as I tend to get in trouble and am more of an a$$hole than I intend to be and just regret it later. Family prob's are compiling the issue too. Oh well, SNAFU.
    All is well with you I hope.
    B
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