Bonding metal to CF
The small metal boss on the seat stay that you screw the mud guard into has come loose. Any tips on what I could use to bond it back in place? I am not 100% sure if it is steel or alu, probably the former, bonded into a Carbon frame.
I have tried various super glues and araldite. They SG was rubbish, the araldite did seem to bond it initially but after a few rides it just comes loose again.
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You need a keyed or threaded interface really, for something that is subject to torque in use.
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Is it not a rivnut?
You might find a rubber version which won't need the insertion tool. Unfortunately the ones we keep are too big for bicycles
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Yes, it is essentially a type of rivnut, although a bit flimsier and the depth is only 4-5mm. Agree that some sort of threaded interface would probably be ideal but I am reluctant to try and insert some other kind of nut/thread that could damage the carbon (it is literally going into a drilled hole in the frame, there is no kind of additional material there to protect it).
Rubber rivnut may well be an option to try, I will do some investigation.
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I had a similar problem with a Rivnut for my mudguard mount albeit in an Alu frame. The rear guard front mount attaches to a short cross piece between the two chain stays. The rivnut became loose and rattled. Got my LBS to reset/renew the rivnut but it lasted all of about 3 weeks before it worked loose again. I think leaving it when it was first loose made the hole in the frame bigger and bigger so the rivnut didn't hold.
I repaired it using a rubber lined Stainless P clip aroud the short cross piece. Been sound ever since. Maybe a similar option for you but you'd need a right angle bracket (Meccano set very useful here) to attach guard.
Have you tried Araldite ARA-400010 2-Tubes Steel Epoxy? I've used it to repair metal threads on a car wing mirror and it held for years. You'd need to clean the area really well then poke and wiggle the glue in and around the mounting with toothpicks etc to ensure you get enough gloop in there.
Hope you get it sorted. Nothing worse than extra rattles from mudguards.
Sometimes. Maybe. Possibly.
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Cheers @photonic69 . I had not tried that particular type of Araldite. I think plan of action is to give that a go and see. If no joy then a rubber rivnut and P clip option both sound like they are worth a try, assuming I can get hold of pieces that will fit the frame.
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JB Weld is another very good two part epoxy, I've heard of people repairing engine crankcases with it.
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It'll all be the same stuff more or less. The issue is the surface area of contact is very small and you are trying to get it to resist shear forces.
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You are most likely correct, the Araldite I used originally seemed to have formed a solid bond but the fixing came loose after 3-4 weeks. As you suggest I am sure that is due to the shear forces.
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I got a cheap Rivnut gun from Amazon like this one https://www.amazon.co.uk/POIU-Rivet-Riveter-Threaded-Mandrel/dp/B09ZYLV86B which came with all sizes of rivnuts. Was good enough to repair the Garmin mount on my integrated carbon bars (which also didn't have much room to work with) after it sheered off from going over a cattle grid at full pelt. Have also replaced bottle cage bolts on an alloy frame using the same gun.
The "rubber rivnuts" sound interesting but if you've got enough room for one of them you'd have enough room for an aluminium rivnut which would be a more permanent fix.
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VuDu glue VM100 black is great for metal to carbon should work for m8st materials too .
https://www.easycomposites.co.uk/vm100-black-methyl-methacrylate-adhesive
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