[Krienert]

Seeking some experiance in Carbon Frame repair...

Alright... I no realize 2 months after buying used, that this frame set probably wasnt a good investment. Many articals online are bashing the issue of Aluminium lugs and Carbond tubes bonding.
Its a 1993 Specialized Epic, and I have a sever problem result of a LBS focing a bike seat into place.
After trouble removing, and no help from the shop, Im left with a busted seat tube binder bold.
Now Ive got extensive fiberglassing experiance... but no carbon; although Im assuming its not to far different.
I'll let the photos do the best to describe the details of the break, but in repair; my thought is to completly cut away the aluminum lug at the seams on the vertical back stays, the seat tube, and top tube all flush at the joint.
Then make a foam core and rebuild the area as a newly created carbon lug.

Is this the right or wrong way? And did I make another bad investment?

Thanks, and lightspeed ahead to ya'll

Joe

 

[Monte]

Now Ive got extensive fiberglassing experiance... but no carbon; although Im assuming its not to far different.

No, it's not any different, just different material, the methods are the same.

I'll let the photos do the best to describe the details of the break, but in repair; my thought is to completly cut away the aluminum lug at the seams on the vertical back stays, the seat tube, and top tube all flush at the joint.

My experience with composites is in helping to build a light (less than 300 lb) 15m wingspan sailplane and a couple other human piloted flying things, all mostly out of carbon.

That said, I'd try and split the lug before just cutting it out, leaving the tubes a little longer. It doesn't look like the bond will give you too much grief, the broken piece came off leaving the tube underneath intact.

Then make a foam core and rebuild the area as a newly created carbon lug.

Is this the right or wrong way? And did I make another bad investment?

The only "wrong" way is using bad materials and methods. You don't want to use just a foam plug, at least not for the seat tube, you'd never get it round enough. Either find a new lug and lay up around that, or use a short section of steel or aluminum seat post tubing and lay up around that.

Edit: I had said use a seat post, but just lay up around a piece of seat tube. You'd still use a seat post for alignment. Don't forget the release agent. Use foam to "extend" the top tube and seat stays.

Have you seen this article http://www.instructables.com/id/How-I-built-a-carbon-bike-frame-at-home-and-a-bam/? It has some good pictures.

Somehow you need a new seat post binder/clamp. The easiest way would be to do it like in the Instructables article, using a piece of tubing to extend the seat tube high enough to give you room for a seat post clamp above the joint.

I'd think about maybe cutting the carbon seat tube (I'd still try and leave the others as long as you can) and making the aluminum or steel tube extension go down below the joint a bit, again look at the Instructables article. Leaving the carbon tube as it is makes for a butt joint in a highly loaded area, not sure if there would be a problem. I suppose you could put enough carbon tow around it so there wouldn't be a problem, but if you move that butt joint down a bit the loads will decrease pretty quickly I think.

Edit: Where you put the butt joint between the new seat tube extension and the carbon seat tube is something to think about. I'm not an engineer, just did a fair amount of work on the gliders. It's a road bike, so the loads are lower than on an mtb, so that helps. If you leave it as close to where it is now, the joint will be encased in all the carbon you build the joint up with. If you move it down, you'll have to build up around the joint anyway, now you'd adding more material down lower on the seat tube, making the whole joint bigger than it may need to be. Something to think about.

Make sure you put a layer of fiberglass around anything aluminum before you start your carbon layers, you'll get electrolysis problems if you don't.

Thanks, and lightspeed ahead to ya'll

Joe

Good luck with that. It is repairable if you want to make the repair. Is it worth it? That's up to you.

 

[C Dunlop]

It is a 16 year old carbon frame. Carbon was crap until 4 or 5 years ago. stick it on the wall of the garage. you can get a $100 alloy frame from price point if you need a cheap frame, and it will have geometry that isn't from the early 1990s, and probably ride better too. You can get it powdercoated in any colour you want for about $80 if you want something different.

If you just want to have a go at fixing it up for fun, sure, but materials cost alone (not to mention if you put a $ figure on your time) will make it more worthwhile to get a new frame.

Carbon is not that hard to work with in flat panels (ie cloth, resin and vac bagging). this is a structural joint though, and the tubing is probably already toast to boot, and it is a very tight joint that will be almost impossible to vaccum bag on a home setup.

If you are going to have a go though, this is my advise: Do not cut the remaining alloy off. Cut off the bolt protrusion only on both the remaining allot and the broken off chunk. Exoxy in the broken off chunk of alloy, clean it all up and wrap, exoxy and bag the lot. Then redrill the hole in the back of the seat tube, then find a removable seat tube clamp to fit.

But really, don't even bother, just stick it on the garage wall and get another bike.

 

[Krienert]

Alright, well...

...I got bend outa shape about wasting my money, so I valued a bit more investment to see if it could be salvaged...

$17.58
New seatpost
bout $7.50 -27mm aluminium pipe (4mm wall)
Bonding
-jb 'cold weld compound' wet interior bonding
=filler of aluminim shavings/grit base
=then filler lose chopped up fiberglasse
=followed by high weave fiberglass cloth wrap (x2)
(throught these layers the 'cold weld' acted as both glue and resin for
saturating the glass)

-then lay-jb 'cold weld compound' putty exterior frame
Then $8 for the bonding..
Bolts
M6 1.00 pitch hex bolts (2) $1.00 ea.
M6 washer and nuts (2/4) $1.00 tot.

The bolts were situatied as shown in the photo.
...Oh yea, the inner glueing was from bottom to top of the seatpost,
And I made scores all over the post with holes so the fiberglass would grip...
(carbon was left smooth but lightly sanded(240g) and cleaned with acetone,
then quickly 'stop bathed' the acetone to maintain the carbonds epoxys' integrity)

Im a ways from buildup, but do ya think it'al hold?:skep:

 

[Krienert]

Maybe no responce cus the photos arent so deace' ?

(to help with the visual, the bolts from a top view..
would be radi from 10 to 4; and 8:45 to 2:00 (clock time=degrees via 360*)
It seemed like structural 'encuragement' here was ideal as there was enough remaining
of the lug to get a firm metal bond, (as well to mention the bottom bolt does a smooth pass through both the aluminium lug, and carbon tube (8:45 to 2:00)

All that is just saying the joint has bolts placed to brace the load rather then tear, followed by the extensive bonding.

Im a ways from buildup-teardown- repaint ... so I dont know yet if its structuraly sound.
Any advice, or recommendations?
Big up to evrybody.
Joe

 

[Krienert]

well.... that short detail and the earlyer photos combined helped to show the supports I added.... There unfortunatly wasnt a camera around last night when I cold welded this.

That last phrase helps to back my request for advice, as we know that the best weld is a hot one... to ensure molecular bond for best strength... This re-structuring is a whole different animal, and im only 2 years exp. with the fiberglass process. So any thoughts both bad and good would help.

 

[Rody]

"Im a ways from buildup, but do ya think it'al hold?"

My opinion...a nice exercise, but I'm sure glad it's not gonna be my fiddley bits perched above the repair

Please, ride smooth roads,

rody

 

[Krienert]

thanks man... I feel confident in my repairs...

although I will defintly be on my feet for a while just for saftey...

I love riding out saddle though.. so its all for the better.

any other thoughts?

 

[Krienert]

has anyone else had any experiance with using fiberglass shards as filler in a cold weld style compound? Will it help or hurt in the long run....

(update: just put the seat on top after a full cure... when sitting in a door frame I can push on the top of the doorway forcing all my weight downward onto the seat with feet in the air) = ing complete sturdyness....my concern is high frequency vibrations from the road, but at least I know it can likly bear about 500-600 lbs. (I only weigh 170)
Any ideas welcome!

 

[Monte]

has anyone else had any experiance with using fiberglass shards as filler in a cold weld style compound? Will it help or hurt in the long run....

Makes for a awesome filler, but not an awesome load bearing unit. I'd have put more uni-directional material in there.

You might be alright, just keep an eye on it. I doubt that it would fail catastrophically so you'll probably have some warning if it goes.

 

[herbn]

I wrote up a thing about making a metal insert,but then on second thought i'd just bond a carbon seatpost in place to do a isp thing,after trimming and smoothing over the rough non structural parts. Lastly do a physical lock with a little set screw. You 'd have to really focus on making an alignment jig to definitely get it the right height and straight forward.

 

[C Dunlop]

sketchy sketchy sketchy.

Put it like this: a small impact with no weight behind it will dent a surfboard, 30kg of leverage will pretty much snap it clean. A surfboard is between 1.75 and 2.2 inches of fibreglass. You have (maybe) 0.3 inches of fibreglass. In other words, the fibreglass is really not doing anything structural. The net effect of this repair is therefore the same as if you had just glued and bolted it. IMO it is still a wall hanging. At most use it as a grocery bike.

I would not place my bung hole, nor my wedding vegetables near that repair.

For the sake of any females you are romantically attached to, I hope your repair holds.

If anything, you should have done it with carbon twine and epoxy.

 

[Krienert]

ouch... my fiscal situation would not permit that at the time....
Well, as you put it, it will make a nice wall hanger either way..
"would not place my bung hole, nor my wedding vegetables near that repair. "
well put...

I guess its back to no bike for me again... Everyone out there, place high thanks in having a bike to ride. Im f-ing sick of walking 6 miles to school...

Best up to ya'll
joe

 

[herbn]

I've seen videos where people leave bikes to be stolen that are held together just barely ,i think loose bars and seat,then they video what happens when the theif steals the bike. Why waste a perfectly well built booby trap?

 

[C Dunlop]

if you need a bike to get to school i am sure this would do it.

http://www.pricepoint.com/detail/19...0-Frames/Sette-Reken-Hardtail-Alloy-Frame.htm

if you can afford $20 for the fibreglass you can probably spring $80 for a frame.

 

[2silent]

sketchy sketchy sketchy.

Put it like this: a small impact with no weight behind it will dent a surfboard, 30kg of leverage will pretty much snap it clean. A surfboard is between 1.75 and 2.2 inches of fibreglass. You have (maybe) 0.3 inches of fibreglass. In other words, the fibreglass is really not doing anything structural. The net effect of this repair is therefore the same as if you had just glued and bolted it. IMO it is still a wall hanging. At most use it as a grocery bike.

I would not place my bung hole, nor my wedding vegetables near that repair.

For the sake of any females you are romantically attached to, I hope your repair holds.

If anything, you should have done it with carbon twine and epoxy.

I'm neither an engineer nor a surfer...

aren't surfboards foam with a thin layer of fiberglass over them?

I've extensively made car parts (from bumpers and hoods to fiberglass subwoofer enclosures and dashboards) and can assure you that 2" thick fiberglass laid up correnty is more than is necessary for just about ANYTHING. With a little curve to it (adds strength) you could drive a CAR over a surfboard shaped object that thick.

 

[themanmonkey]

aren't surfboards foam with a thin layer of fiberglass over them?

They are, he has no idea what he's talking about.

To the OP I think herbn's idea of bonding a carbon post in place is a good one.

 

[Krienert]

man...if I had access to carbon fiber tow when I did this I got a feeling I would be so much better off....

Its hard for me to see this frame go to no-ridable...as in visual, its awesome.
The raw carbon has an mysterious iridecens to it....
Plus, im really fond or the organic curves of the fix....

 

[Krienert]

Oh man... I just checked out that frame on price point... then I went over to nashbar...

There are similar frames around that price that all look really nice....

My question is do they ride well? and/or has anyone in this post had experiance with em?

(this question is more or less a acceptance of the other frames death. RIP)

 

[Linnaeus]

sketchy sketchy sketchy.

Put it like this: a small impact with no weight behind it will dent a surfboard, 30kg of leverage will pretty much snap it clean. A surfboard is between 1.75 and 2.2 inches of fibreglass. You have (maybe) 0.3 inches of fibreglass. In other words, the fibreglass is really not doing anything structural. The net effect of this repair is therefore the same as if you had just glued and bolted it. IMO it is still a wall hanging. At most use it as a grocery bike.
...
If anything, you should have done it with carbon twine and epoxy.

This is one of the least informed posts of the year.