Cracked carbon frame

[Chris Jeggo]

Has anyone tried a carbon fibre repair like this on a metal frame? A clubmate of mine suffered a broken seat tube of a 531DB frame, fitted some sort of metal sleeve round it and glued it all together with araldite. It doesn't look pretty, but it's still holding together many decades later. (He's the last of the small spenders.)

[DevonDamo]

Has anyone tried a carbon fibre repair like this on a metal frame? A clubmate of mine suffered a broken seat tube of a 531DB frame, fitted some sort of metal sleeve round it and glued it all together with araldite. It doesn't look pretty, but it's still holding together many decades later. (He's the last of the small spenders.)

Yep - see my posts on page 2 of this thread. I was using fibreglass on an aluminium frame (a folding bike which I'd snapped because I was too tall for it so had the seatpost over-extended.) It worked, but it was a tall order as that part of the frame comes under phenomenal strain with such a long seatpost levering it. I ended up scrapping the bike, which wasn't very good anyway, but I'm reasonably happy that the epoxy had bonded the fibreglass to the aluminium (which I'd degreased and abraded first.) The internet didn't have much to say about whether epoxy would bond to ally, but my experiment seems to answer that - either the epoxy actually bonded, or the tube I created formed such a close-fitting, strong sleeve that it didn't matter that it wasn't stuck.

[Cowsham]

small update,I glued two patches now two days to cure
IMG_20210406_091605.jpg

Well done you've probably turned a scrap carbon frame into a useful bike again. Now to sort the cause of the problem... that bar steward chain.

[gregoryoftours]

Looks good, I don't have any direct experience but it may take more layers.

[Orbearacer]

Besed on my research (youtube) two leyers is enough I hope
After two days looking good, now just wet sandpaper to polish and painting.

[DevonDamo]

That's so pretty that I'd just lacquer it and have it as a "look what I did" talking-point, I'd also double-up on whatever the internet has told you re. layers of carbon. (Not because I know any better than the internet, but because I have no clue about carbon strength so I'd want to take a belt-and braces approach.) I can't imagine it would add much weight, and you could use the extra layers to 'feather' the repair - i.e. have them getting progressively shorter so you don't end up with a square edge to the repair which would be a stress concentration point.

[gregoryoftours]

Wow, what a nice looking job! Really cool that you've gone ahead and done it. It will be very interesting to see how it holds up (I expect that it will). Please keep us updated as time goes on.

[Cowsham]

Two layers is enough -- but I do agree with the repair patina look -- just get a coat of lacquer on -- good talking point and less chance someone would want to steal it.

[Tiberius]

Wow, what a nice looking job! Really cool that you've gone ahead and done it. It will be very interesting to see how it holds up (I expect that it will). Please keep us updated as time goes on.

+1 to that.

OP. I'm really glad that you went ahead with this job and ignored the naysayers - this old dog is happy to learn new tricks.

Though I have zero experience of carbon frames, and therefore nothing to contribute, I have followed this thread with great interest. Hope all goes well with the rebuild and PLEASE report back when it's got a few miles under it's belt.

Oh and, well done.