Framebuilders - carbon fork - aluminum forkend insert re-glue
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12-14-09, 08:24 AM
hi framebuilders. i'm not one of you, but i'm hoping that some of you who have experience in this area can answer a question for me. i recently got a carbon fork with a loose and wiggley alu forkend insert.
i've emailed the company, as well as one of the reputable carbon repair companies out there, trying to figure out if it can be repaired. i think it can be. a friend pointed me toward 3M brand DP-460 epoxy, and i read this (http://www.sheldonbrown.com/rinard/carbonqa.htm), which gives some good information.
but what i'd really like is for somebody to tell me, "yes, you can do this, this is safe," or, "no, this cannot be done for a really good reason"... and i'm getting pretty eager to hear back definitive info from those whom i've emailed, but i have not yet heard back.
can anybody here chime in?
i'd be more interested in having this professionaly re-done so i can trust it on a road bike, whereas if i do it myself i'd limit the fork's use to more around-town riding.
12-14-09, 09:27 PM
I'm guessing it's uneconomic.
people repair rear dropouts in carbon frames all the time, but forks are far too cheap and failures far more dangerous in the fork dropouts. Trash it.
Don't think there are any people here building with carbon, but who knows who might be lurking.
I'm messing around with carbon but don't have enough knowledge to give out any advice.
Well, beyond saying try to contact the fork's manufacturer and see what they may have to say.
Since it is a manufacturer's defect they may replace the fork for you.
You need to evaluate why the drop is loose. If it took a big impact/etc... you could have damage beyond that which regluing will repair
You say the part is loose. Your first issue would be to get it free so that you can be sure that when replaced it will be fully bonded. You can't use heat, or excess force for obvious reasons. In this case poking glue in there will not likely get the job done. Epoxy is thick enough that it doesn't wick into hairline cracks.
Next issue is to ensure you can achieve a good bond. I would prefer a product like WEST 105, 205/206 since I have used it extensively. I would thicken it with some fillers, like 1 part cabosil and 3 part of something like the 404 filler. You can probably find a small or sample pack of the epoxy. Scrounging up the fillers could be the hard part. You need to etch the aluminum, and throroughly clean the inside of the fork at the bonding site. I would probably sand very lightly, and wash with rubbing alcohol. Stay away from acetone, which has some oils in it.
Next you have to ensure you can align the drop out. A wheel and quick release and some eyeballing. With luck the part is well bonded and fits back in only one place. But it could be the most difficult part of the process.
Finally I would post-cure the epoxy after it has hardened. This involves heating the part for an hour or so to about 170 degree. You can cover the fork with plastic, and put the drop in a pot of hot water, keep adding water or work out a heat setting that will keep the water at 170 ish. It isn't super critical, but you want to keep the heat reasonable. I have a tiny hot-plate for keeping coffe warm, and I just put stuff on that, it is sub 200ish. You can post cure at any point, a week or a month later. The trunks of cars on a hot day can post cure your product.
If you end up stuck with the fork, and decide to go for a new one. Try a repair anyway. It is this kind of experience that gets you the skills you need to work on stuff. Whether to ride it or not is up to your judgment.
Since I have carbon, kevlar, and glass tow around the house, I would probably wrap the carbon tube/drop with some of that to contain the possibility of the end of the tube blowing out on me.
12-16-09, 08:17 AM
Thank you so much for the detailed response.
There is no evidence on the fork of an impact. A bit of googling turned up that this has happened to others of its model, without crashing, so I'm going on the fact that it may have just been slightly defective and debonded over time.
I suppose the first trick will be to try to get the bugger free. Any ideas?
You mention the products that you're familiar with. Do you have any experience with DP-460?
Again, thanks so much for the very detailed response. It is definitely something I can use. I will try the repair, but if I wind up buying a new fork for my road bike this will be a fork for an around-town type of bike, since, if I do the repair on my own, I'd rather not trust my teeth to it on 50mph+ descents.
12-16-09, 09:28 PM
Read on the Framebuilders List where some pros use JB Weld to attach carbon rear triangles to the main frame. I'd give it a go after you check for corrosion and possible cracks in the carbon.
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