Bonding aluminium to carbon?

[Flood]

So the seat clamp area on my carbon on one 456 has cracked around the tube, its gone about a 1/3rd of the way round. 2nd hand so on one arent warrantying it.

After I'd finished sobbing and since the area isnt really load bearing (its only the top 10mm or so under the clamp where the crack is) i came up with the the idea of bonding a reducer shim into the 30.6mm seat tube and running a 27.2mm seat tube.

The shim is 90mm long and 1.7mm thick aluminium, it'll sit down well below the top tube, so I reckon it'll be stronger than ever, only question is what do i use to bond the shim in there? Guess its an epoxy used to bond the frames apart, would something like this be suitable?

[upsidedownmark]

Bonding alu with epoxy is a bit hit and miss to the best of my knowledge - ideally you need a specialist epoxy/glue for alu, and some fairly careful prep. I'd also advise against mixing carbon with aluminium due to galvanic corrosion (though my experience of that is with boats, and possibly it's less of an issue without salt water.

Can you get a carbon tube to serve the same role? That would be a simpler / safer option IMHO

Alternatively, could you repair externally with wet layup carbon - only problem I could forsee there is with the clamp..

[GnuBee]

http://www.easycomposites.co.uk/Category/Resin--Ge...

ET500 will do the job, the technical people at EasyComposites will give further advice if required.

It's a very common requirement bonding aluminium to carbon fibre.

Not sure about the remark regarding galvanic corrosion - that's the result of different metals rather than metal + plastic.

[Matt_N]

GnuBee said:

http://www.easycomposites.co.uk/Category/Resin--Ge...

ET500 will do the job, the technical people at EasyComposites will give further advice if required.

It's a very common requirement bonding aluminium to carbon fibre.

Not sure about the remark regarding galvanic corrosion - that's the result of different metals rather than metal + plastic.

Carbon fibres are excellent conductors and produce a large galvanic potential with aluminium alloys, it's quite a big issue in the aero industry.

As long as the CF is well sealed and isolated from the aluminium (i.e resin or lacquer when mating a CF bar with an ali stem) then there shouldn't be a problem.

[agentnomad]

Not used this company but was recommend them on the internet on this or another forum site, then when talking about this service at Manchester velodrome on a race night some people had used them and seen the work and reinforced the recommendation.

http://www.fibre-lyte.co.uk/index.html
http://www.fibre-lyte.co.uk

You need to look for the little bike icon and look for frame repairs

Don't know the costs of the repairs but looking at the carbon chain rings for track use they are around the same price of Campagnolo piata chain rings so could be cost effective.

[AndrewEH1]

Within trials there is a single man operation:

http://www.jaf-bikes.co.uk/jaf-repairs

He does carbon wrapping on alu trials frame, which take a lot of force from drops etc

Might be worth giving him a call

[upsidedownmark]

Found the guys at fibre lyte very helpful, and would also highly recommend carbonology(.com) who spent a goodly amount of time on the phone discussing the options and technicalities of a recent repair.

[Flood]

Thanks for all the help chaps, I've not been able to get on the site for a while for some reason.

Good shout on fibre-lyte, they're right round the corner from me and certainly a good bunch.

I found some et500 at work, bonded the collar in and bugger me if it hasnt entirely fixed it, resolved the constantly slipping alu seat post and even saved me a few grammes*!

Should've done this from the outset, one hard ride down and despite my mates predictions, hasnt resulted in a carbon version of 1man1jar (ignorance is bliss). I'll update in future if anyone cares.

• in theory

[neilpass]

Hi I know this is 2 years down the line, but did this repair hold up? I've recently bought a frame which I've since discovered was fitted with the wrong size seatpost and has cracked the carbon just below the crank, as the frame didn't cost me a lot I'm unable to justify the £200-300 prices I've been quoted and was considering epoxying a long 100-120mm 31.6-27.2 shim and getting a suitable seatpost.