Repair splint for stuck seatpost?

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james01
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Joined: 6 Aug 2007, 4:48am

Repair splint for stuck seatpost?

Postby james01 » 26 Mar 2012, 2:13pm

Having dumped a perfectly good frame with a hopelessly stuck seatpost recently has got me thinking. Assuming there's enough post showing above the frame, the post could be cut and joined to a new seatpost by means of a well-engineered clamp-on sleeve. I've tried Googling to no avail, has anyone heard of this fix being applied?

Ian Raleigh

Re: Repair splint for stuck seatpost?

Postby Ian Raleigh » 26 Mar 2012, 2:37pm

Well in my eyes it may bend/snap at the joint so i would be worried out it failing every time i'd be on the bike.

The joint would be so wide and ugly too to take the strain.

Why not remove your chainset/bottom bracket and and seal the seat post end with a strong plaggy bag
and a few elastic bands to form a seal catch bag ! Then pour down the seat tube via' bottom bracket
'original' Coke Cola !! fill the frame tube up with this toxic stuff and leave for a week, Then empty
the tubes - remove the plastic bag, find your electric drill out and drill two holes in the broken seat
post, use a large good quality Allen key which can be placed through the holes then a find yourself
a long enough hollow bar to act as a fulcrum to give you extra leverage, it should come loose.

Coke Cola is well known for eating through any corrosion and it worked for me.

Ian.

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Steve Kish
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Joined: 11 Sep 2010, 9:50pm

Re: Repair splint for stuck seatpost?

Postby Steve Kish » 26 Mar 2012, 2:59pm

Alternatively, a decent machine shop should be able to score the post fron the inside with a few lines that would enable the post to be snapped out in about 4 - 6 pieces, like orange segments.
Old enough to know better but too young to care.

hamster
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Joined: 2 Feb 2007, 12:42pm

Re: Repair splint for stuck seatpost?

Postby hamster » 26 Mar 2012, 4:29pm

Caustic soda dissolves the seatpost completely, alternatively you can saw it out by cutting a slot down its length. It's a nasty tiring job but it works.

LollyKat
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Joined: 28 May 2011, 11:25pm
Location: Scotland

Re: Repair splint for stuck seatpost?

Postby LollyKat » 26 Mar 2012, 5:17pm

hamster wrote:Caustic soda dissolves the seatpost completely,

...assuming a steel frame. Otherwise you'd dissolve the lot! :shock:

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gaz
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Location: Kent, car park of England

Re: Repair splint for stuck seatpost?

Postby gaz » 26 Mar 2012, 5:45pm

james01 wrote:... Assuming there's enough post showing above the frame, the post could be cut and joined to a new seatpost by means of a well-engineered clamp-on sleeve...

The forums very own Mick F has suggested riveting as a solution for converting a threaded steerer to threadless, I'd imagine the same principles would apply here but I've no idea whether or not it would succeed. An internal brace at the join of the old and new posts certainly sounds more aesthetically pleasing.

If you don't fancy the caustic solutions for removing an old post that won't come out sometimes they can be hammered further down, leaving room for the new post on top.
Hand wash only. Do not iron.

Brucey
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Joined: 4 Jan 2012, 6:25pm

Re: Repair splint for stuck seatpost?

Postby Brucey » 26 Mar 2012, 7:00pm

james01 wrote:Having dumped a perfectly good frame with a hopelessly stuck seatpost recently has got me thinking. Assuming there's enough post showing above the frame, the post could be cut and joined to a new seatpost by means of a well-engineered clamp-on sleeve. I've tried Googling to no avail, has anyone heard of this fix being applied?


I've applied various fixes for this;

1) padsaw the old pin (careful now.....) slots on the inside allow the pin to collapse slightly and therefore move. Risk is that the frame is damaged on the inside.

2) the 'big drill'. An Al pin in a steel frame can be machined out. You need a big drill press that will cope with a 1" drill; I used one where I could strap the frame to the side of the machine.

3) mild heat on the outside + force; wrap rags round the frame, tip boiling water over them, swing like a chimp.

4) intense heat (blowtorch...) + force; CTE is against you, but corrosion product dries out and pin may be looser when cold.

5) liquid nitrogen + force; invert frame, add liquid nitrogen to seat tube. After about two minutes the seat pin will be noticably smaller dia than it was before and may come loose with force. Works best with aluminium pin and steel frame.

6) weld onto seat pin remains; heat may break bonds of corrosion, welded additions may give purchase to a sheared pin.


I've also made special seat pins with an adhesively bonded sleeve joint in them. Such joints can, if made well, have a shear strength of about 1 tonne per square inch. Quite a few commercially made seat pins have a bonded or force-fitted joint in the top.

cheers
-------------------------------------------------------------------------------
~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~

Ian Raleigh

Re: Repair splint for stuck seatpost?

Postby Ian Raleigh » 26 Mar 2012, 7:03pm

hamster wrote:Caustic soda dissolves the seatpost completely, alternatively you can saw it out by cutting a slot down its length. It's a nasty tiring job but it works.


and could ruin the paintwork/stickers on the frame if any splash's are not spotted :shock:

hamster
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Joined: 2 Feb 2007, 12:42pm

Re: Repair splint for stuck seatpost?

Postby hamster » 27 Mar 2012, 10:02am

True, but as the alternative is scrapping the frame its all 'last chance saloon' anyway. Repainting is always cheaper than a new frame! :wink:

g00se
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Re: Repair splint for stuck seatpost?

Postby g00se » 27 Mar 2012, 11:07am

If the post is stuck because the frame and post are a mix of aluminium and steel - it will probably be galvanic corrosion. I've read that ammonia is a good agent to soak into the area - rather than something like plusgas which apparently doesn't work in this situation.

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Trigger
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Location: Derby/Notts

Re: Repair splint for stuck seatpost?

Postby Trigger » 27 Mar 2012, 6:24pm

Cut the top of the post off nice and square, then weld a cap over to seal it.

Fill seat tube with gunpowder from bottom bracket, poke a fuse through one of the bottle cage bolt holes, stand well back and FIRE!!!

Preferably you should have thought about where the seat pin was pointing before ignition, I find waiting until next door's cat is crapping in our veg boxes makes best use of the ignition, two birds with one stone and all that.

HTH.

Mike Sales
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Joined: 7 Mar 2009, 3:31pm

Re: Repair splint for stuck seatpost?

Postby Mike Sales » 27 Mar 2012, 6:55pm

Trigger wrote:Cut the top of the post off nice and square, then weld a cap over to seal it.

Fill seat tube with gunpowder from bottom bracket, poke a fuse through one of the bottle cage bolt holes, stand well back and FIRE!!!

Preferably you should have thought about where the seat pin was pointing before ignition, I find waiting until next door's cat is crapping in our veg boxes makes best use of the ignition, two birds with one stone and all that.

HTH.


I must try that. Though of course I never let my own seat posts get stuck so it will have to be someone else's bike.

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Mick F
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Re: Repair splint for stuck seatpost?

Postby Mick F » 27 Mar 2012, 8:18pm

gaz wrote:The forums very own Mick F has suggested riveting as a solution for converting a threaded steerer to threadless.......
Grief!
Fancy you remembering that!
That was YEARS ago! :shock:

I still think the steel tubing of a steerer could be modified easily with a sleeve and rivets. This would save the paintwork on the forks. I did say I was going to experiment with a spare frame I have, but not done it yet.

However, an alu seatpost is a different kettle of fish.
My suggestion would be to drill it so it had thinner walls and hacksaw a slot and bash it into the seat tube if it wouldn't come outwards. Then fit a new seat post.
Mick F. Cornwall