CliffordK

Ok, my next project will be salvaging this Colnago C-50. It may take me a while to get it done, so have patience.

Anyway, 28.0 seattube shimmed to a 27.2 seatpost using an aluminum sleeve.

Post was cut off before I got it. You can see where the seattube collar clamp went. And the seat post was cut 1/16" to 1/8" above the collar.

The post extends into the seattube about 8", but I assume the sleeve is only about 3" or 4" long.

C-50_Seatpost_Side.jpg
C-50_SeatPost_Back.jpg
C-50_Seatpost_Top.jpg

Ideas?

Obviously I don't want to damage the frame. Oil could be used as long as there is no damage. I could try something like ammonia, but don't want to damage the bottom bracket shell, or any lugs. Molasses is supposed to take oxidation off of steel, but a little less clear about aluminum.

Perhaps the first thing is to tap it with a plastic hammer. If it moves, then pound it down past the shim, and it should all come out. I could probably carefully cut out the rear slot, which would give me about 1" of reduced pressure (out of the approximately 3" to 4" shim).

I could try drilling, but I'm worried about my ability to accurately drill within 0.4mm per side.

Maybe cutting a slot all the way down, but 8" is pretty deep. I would only need to go down the 4" or so, but a blind cut is difficult. Still, 0.4mm is pretty close tolerance.

Maybe a hand reamer to thin the walls first???

Other ideas?

trailangel

Geez. Have you tried upside down in ice water while holding the seat tube with hand to warm it.
Might be just enough to break it free.

CliffordK

I might try it. I have to either pound the post further in, or figure out how to pull it. Somewhere I saw a blind hole puller, I think, but don't have one. Maybe take a washer, trim the edges so it will slide in, then once in, it should flatten out.

Wilfred Laurier

Could you cut a slot in the old seatpost and just use a smaller one?

deacon mark

I would simply cut down the slot as far as I could then work it out. You then would have enough leverage to insert something between the post and shim and then get it to move. I would not be pounding down. Other option is to clamp the whole shim twist it all out using frame for leverage.

CliffordK

I thought about that. It would take about a 7/8" seatpost which is pretty small. But, I'd like to get it out and do it right.

I'll probably start with that. The slot, however, might catch if I try to ream it later.

There isn't much left sticking up to clamp onto. 1/16" to 1/18", and the CF is pretty soft.

FBinNY 

Odds are that the shim is split it's full length. That means cutting the post through is easier and safer if you align your cut with the slot in the shim. Once the post is cut through, you can try to collapse the assembly and free it from the frame.

Otherwise, you can fabricate a sturdy disc with an OD slightly smaller than the post or shim. Drill and tap it in the center to accept the screw head of a slide hammer. Drop it in via the BB, attach the hammer and hammer away after making an offering to St. Jude.

If dropping the disc in via the BB isn't an option, file opposite sides to make a "track" oval, drop it in through the post Tutn the frame over and jiggle until you have it laying flat on the bottom of the post. The rest is the same.

Slash5

Since you have open tubes, I think I'd try a slide hammer first. Easy to try and shouldn't damage anything if it doesn't work.

squirtdad

Probably the hacksaw blade inside the seat post method. you can cut out the carbon seat post first and then see if the shim will come out, then if not then cut the shim aligned by the slot and see if you get more leverage by twisting the cut and pulling. Obviously avoid any cutting in the actual frame

dweenk

Looks like it is CF frame - CF shim - AL post. I would definitely try to make a slide hammer before I started cutting.

IrishBrewer

Have you tried spinning it?

I would spray a bit of penetrating oil on the seat post, let it soak for a while. Then try to grab on to what you can with a channel lock pliers and try to spin/pull it off.

woodcraft

A pipe saver bit might work. There are several brands/designs- available at at hardware & plb. supplys.

Intended to cut PVC.

https://www.cpesupply.com/2329722/Pr...FRBEfgodPOUHtQ

27.2 seatpost is slightly smaller OD than 3/4" pipe,

& the shim gives add'l clearance to the frame.

Andrew R Stewart 

dweenk- The post is carbon as said by the OP. One look at the photo confirms this.


Francis- I thought about your suggestion to align any slitting of the post with the likely slit in the shim. I'll disagree though for this reason. Trying to cut a post without contacting the ID of the seat tube is not an easy job. having a separation (in the shim) between makes this a bit easier to do. So if one were slitting where the shim wasn't also slotted the shim would add some protection to the seat tube. Cut with the saw blade backwards (so the cutting action is on the draw out stroke) for a couple of reasons. One is to better control where the end of the saw blade is when it starts to cut, the other is so that when you see AL (the shim's) chips coming out you know you've cut far enough. Also the few handfuls of posts that I've had to slit usually needed two cuts roughly opposite each other to allow the post to be collapsed then removed. The lack of much protrusion (the post is cut close the top of the seat tube) makes this collapsing down even harder to do.


Once the old post is removed and the shim's ID is exposed using a chemical method to dissolve the shim will further reduce any damage to the carbon frame. Andy.

woodcraft

I did a test with the pipe saver bit, on a cut off scrap of CF seat post. (you do trim your seat posts to save weight, right?)

The bit has guide washers of several sizes to correspond to the ID of various pipe schedules.

It cut slowly but cleanly, leaving a thin shell of the tube OD. I cut down 3/8" or 1/2" in most of a minute.

An extension, a respirator, and some patience would be needed to drill away 8", but it should work pretty well.

fietsbob

with the BB out, perhaps you can use that opening to put something in larger than the ID of the smaller tube..

and bang on that from the underside..

CliffordK

Thanks, woodcraft, I hadn't seen those pipe savers before. But they may well do the trick.

Assuming the shim only goes down a couple of inches, then I wouldn't have to cut to the bottom. The post below the shim should be loose. A little tearing of an undersized cutter may not be bad.

FBinNY & Andrew R Stewart, yes, any cutting should be towards the shim metal, and not towards the slot. Sacrifice the shim (gives me about a 0.4 mm of metal before hitting carbon fiber). Plus seeing silver aluminum would indicate a stopping place for cutting. Also, no seattube hole in the BB, so all work is from the top.

squirtdad, Once the post is free, I'm expecting to be able to peal the shim loose with a pocket knife. And, that should allow anything further down to just fall out (I hope).

ishBrewer, I haven't tried lube. I don't really want to go with a solvent that could damage carbon/plastic, but a light oil might be worth trying. Assuming a gap around the post below the shim, it should be possible to get oil into that gap, then allow it to trickle down to the shim with the frame upside-down. The limit is there is nothing to grab onto. So, I would likely need to make a slide-hammer as suggested in other posts. I actually have some ideas on how to make a pretty sturdy end/guide for a slide hammer that would stay put. But, I'm still hoping it doesn't come to that.

I have been thinking about a hand reamer. But, woodcraft's PVC Pipe Saver (or another guided cutter) may take it. A little more research. I suppose I'm divided between:

Rambit:
https://www.plumbingsupply.com/rambi...aver-tool.html

And Reed
https://www.reedmfgco.com/en/product...tting-reamers/
https://www.reedmfgco.com/en/product...reamers/ppr75/

I have made a custom fly cutter for a previous project, so in theory I could make one like the Reed cutters if sizes are wrong. The Rambit style could also be modified if necessary.

As far as replacement... I'll go with a 28mm post, or I've been considering building up a 27.2 post to 28mm using CF sleeves.
https://composites.sollerpaddles.com,carbon-fiber,carbon,fiber,sleeve,fabric

That should eliminate the problem with corrosion, and allow top to bottom support of the post.

rmfnla

This.

Use a toggle bolt on the end to engage the seat post...

Slash5

I've used a washer that is loose on the slide hammer shaft so that it will tilt. Then grind/file flats on opposite sides so it will slide down the inner diameter while tilted but too large to pull through when flat.

rmfnla

Sounds like a good option...

woodcraft

I think the rambit type is good because cheap, longer shaft, & multiple size guide washers.

xenologer

Is the Inside Diameter of the cut seatpost close enough to say, the size of a Quill Stem?
Use quill to grab it from the inside

xiaoman1 

RESPIRATOR for sure.

unterhausen

my lbs uses coke on carbon/aluminum stuck things. Carbonated drinks are a mild acid, I think Coke is moreso.

joejack951

I'd ride around on that frame with no seat for a while and wait for the remaining carbon seatpost in the frame to assplode. Shouldn't take long based on forum research.