Broken carbon seatpost

[clarion]

Sorry if this has been covered before - I searched but couldn't see anything.  Links to previous threads appreciated.

Butterfly's Specialized S-Works seatpost has broken at the point it emerges from the carbon frame.  We have a spare (!) carbon seatpost, but we need to remove the stub, which is proving difficult.

Anyone any ideas?

Frame is not damaged, just the seatpost, which had a fairly clean break, though it is delaminating inside.

[rafletcher]

Hacksaw blade and care.

[clarion]

I feared that might be the answer.  Unfortunately, I think there is a step in the frame where the post finishes, so the best I can manage is a diagonal slot.  I've already tried cutting down the seat tube slot.

[Polar Bear]

How much post is showing?  Is there enough to get molegrips on and apply some force?   I watched a guy put a bung in the top of a broken post to stop it crushing in the jaws, then clamp the wrench firmly before twisting.

[clarion]

Not enough, I'm afraid.  It is a very clean break   I've tried large molegrips across the tube (I didn't think of a bung, mind - top tip), and small ones on an edge.

[Domestique]

Could you use something like this, or similar to it, to help grip the post and pull it out

http://www.probikekit.com/display.php?code=A0806

Edit, beaten by PB

Wine cork or similar, gaffer tape to make a nearly fit in the seat post. Big screw into wine cork to expand it enough to grip seat post 

[clarion]

I considered using a modded star nut, but I think it might be too narrow compared to a steerer.

[PloddinPedro]

I'm not sure if the respective diameters would suit, but it might be possible to use a metal "star-fangled-nut" of the sort used in aluminium threadless steerers to attach the top cap. If you knocked such a nut into the seat tube, you could than thread in a long metric bolt and you'd have the makings of a rudimentary puller. Spread the seat tube (carefully!) apart at the clamp point and lube the whole with carb release and you may get lucky.

EDIT: crossed with your previous post! How far out are the respective diameters? Could you remove some of the star-nut wings and bend the rest to fit? Once you've got it into the post, it should self-tighten so long as the wings aren't at too much of a "streamlined" angle - ?

[clarion]

... carb release ...

What's that?  Sounds like a useful thing in this case.  I think releasing any bonding would be a good idea.  Metal, I'd just soak it in WD40 to start with.

[JohnP]

I wish I had even a modicum of knowledge of building trades but ... are BIIIGGG expanders bolts (rawlbolt style) available?  Something squishy and rubber might be on the market.  Or make your own?

[PloddinPedro]

... carb release ...

What's that?  Sounds like a useful thing in this case.  I think releasing any bonding would be a good idea.  Metal, I'd just soak it in WD40 to start with.

A spray which loosens carbon components:
http://www.chainreactioncycles.com/Models.aspx?ModelID=27849

You can also get the reverse - stuff which helps them grip: http://www.chainreactioncycles.com/Models.aspx?ModelID=27848

I consider a can of each of these to be a must-have in the toolshed when dealing with carbon bits.

[JohnP]

A small pre dinner glass of Fino and my brain has gone in to overdrive -   Could you fashion something like an umbrella frame on the basis that what goes up a tube down won't come down the tube up.

Maybe a few spokes with a last couple of cms bent back at an acute angle; join them together strong binding wire, poke it down the tube and get the ends to butt up against the end of the seat tube.  Then "simply" pull up on the spokes.  Best not to let go of the spokes in case they rop right down the seat tube.

[JohnP]

Found this elsewhere

Option 1:

Thread: Carbon post stuck in steel frame

damocles 1 wrote:

Okay, I've done this TOO many times...

Cut the post off about 1/2" to 1" above the seat clamp.
Take the hacksaw out of the saw and wrap one end in a towel.
Use this modified blade to cut the post by putting the blade down into the carbon tube.
Make vertical cuts MOST of the way through the post at even intervals around the tube.
-4 or 5 cuts does the trick
Once you've made all of the cuts, take a set a Channel Lock type pliers and crush the seatpost carefully.
The crushing will break the post free and you can pull it out.

This works EVERY TIME!!!!

Specialized carbon seat post broke & stuck [Archive]  - Bike Forums

[rafletcher]

I feared that might be the answer.  Unfortunately, I think there is a step in the frame where the post finishes, so the best I can manage is a diagonal slot.  I've already tried cutting down the seat tube slot.

Even if you can't cut all the way down, several cuts around the circumference for most of the depth will loosen it, hopefully sufficiently to pull it all out.

[PloddinPedro]

Another random thought - if you have an old fashioned quill stem, it might be possible to insert it into the post tube, expand it sufficient to grip (but not too much so as to flex expand the tube and jamit tighter) then twist to turn and withdraw the post tube a bit from the seat tube - ?

[Rhys W]

Is there enough seatpost showing to drill two holes through the top? Then you can insert some kind of rod to gain leverage.

[clarion]

No.  Almost nothing at all above the frame.

[Sergeant Pluck]

1st choice: piece of dowel sized to slide inside snugly-ish + 2-pack epoxy glue / resin. Allow to set, pull on dowel.

2nd choice, but I can't see how the above could fail: are there any small engineering workshops near you, or a garage used to working on older cars? Such places often have sets of Easy-Outs and some of the larger versions would do the job on the inside of a seatpost.

http://www.toolprice.com/product/1225D/Srew-Extractor--Bolt--Stud-Extractor--Bolt-Removal.html

[rogerzilla]

A big tap should grip it without expanding it, and allow it to be pulled out.  This is how you pull the bushes out of a Brompton frame, more or less the same engineering situation (stepped tube so can't drift the bush straight out from behind, and plastic internal surface).  Big taps are horribly expensive though.

Supergluing an extension piece in is another option; it shouldn't be *that* hard to pull out.

[Polar Bear]

This thread has convinced me that soot is not a good bicycle material.   Think I'll stick to metal.

I think that 'quill stem' down the tube idea could be a goer.   If you need something slightly bigger I have a steerer extender for sliding into 1 1/8 ahead steerers.    

[clarion]

We're just trying to recall where a spare quill stem might be living.  I think that's got to be worth a go.

[rafletcher]

I think expanding a smooth stem inside the smooth bore sufficiently to grip may expand the seatpost too snugly in the seat tube - hence the use of taps as suggested by RZ. These grip without expanding.

You could use a small chisel to try and split the seatpost along a hacksaw score, though the weave may hamper this.

[PloddinPedro]

I think expanding a smooth stem inside the smooth bore sufficiently to grip may expand the seatpost too snugly in the seat tube - hence the use of taps as suggested by RZ. These grip without expanding.

You could use a small chisel to try and split the seatpost along a hacksaw score, though the weave may hamper this.

My thoughts about the quill idea were that you could progressively tighten it until the resistence between the quill and the seat post when turning the quill was just higher than the resistance between the post and the seat tube - that's the theory. I did say not to overtighten and jam it all together. If you could get it to the point where it won't turn, a thump on the end of the stem to break the interference fit between the post tube and the seat tube might help loosen it.

[clarion]

I've tried a quill stem.  It just wouldn't fit

I've used a bar end lever and managed to shift the stub a bit, but not far, and it doesn't seem to be yielding.  I'm wary of putting much force into it as it expands as I turn, and I really don't want to damage the frame...

[Hot Flatus]

Rub some grease on it then check yourself into a cryogenic freezer