Lugged carbon frame fix/glue

[Rockafella]

Hey all.

 

I have an older lugged carbon frame where the glue has come loose on one of the drop-outs and the frame needs to be re-glued on that joint where the alu meets the carbon.

 

does anyone know of someone in cape town area who is good at working with such things? I am not really in the mood to get rid of the frame and the warranty has elapsed. it just needs to be re-glued as there is NO structural damage - only loose glue.

 

regards

 

 

 

[TokenFreak]

Speak to Mark at Mark's Bicycle Workshop down in Bellville. I know they do repairs on carbon frames

[Johan Bornman]

Do it yourself.

1) Go buy some Pratley Quickset epoxy.

2) Centre your brake calliper nicely so that you have even spacing between the left and right pads.

3) Confirm that the brake makes simultaneous contact on the left and right when you pull the lever.

4) keep a large cable tie handy.

5) Remove the drop-out and clean off any loose stuff. Do same inside the hole in the frame.

6) Apply epoxy to the drop-out and replace it.

7) Clamp the wheel in the fork.

8) Apply the brake and keep it in applied with the cable tie.

9) Make coffee, watch TV and return one hour later.

10) File/sand off any squished-out epoxy.

 

11) Go for ride.

 

Edit: I also meant to add that there is no pull-out force on drop-outs of rim-brake bikes. Therefore ultimate strength is not the primary objective. Alignment and a good seal is what you're after. Disk-brake bikes are another story though and there is a pulling force on the drop-out upon braking. But it sounds like your problem is with a rim-brake bike.

Johan Bornman2008-09-01 23:32:39

[HammerHed]

Johan, can you repair chips in a carbon frame with Pratley's Epoxy?

[Johan Bornman]

Johan' date=' can you repair chips in a carbon frame with Pratley's Epoxy? [/quote']

 

You could, and structurally it will be OK, providing the chips didn't compromise the structure in the first place. I guess what I'm saying is that the epoxy wont interact with the resin in the matrix.

 

However, cosmetically it'll be ugly. Epoxy is translucent, milky white or amber and the patch will stick out like a sore thumb. Further, expoxy doesn't polish nicely to a gloss.

 

I would experiment (on someone else's bike of course) first with some fibreglass resin that's available from most paint shops. That stuff is clearer and will dry to a similar finish and polishes nicely.

 

 

[cycleq]

The Quick Set epoxy is not ideal. It is better to use Epidermix 372 or a slow-set epoxy.

[Johan Bornman]

The Quick Set epoxy is not ideal. It is better to use Epidermix 372 or a slow-set epoxy.

 

It'll be nice to know why? I'm not familiar with Epidermix - sounds like it'll glue skin?

[cycleq]

Just relating what I was told by the old man (Bill I). I believe it has to do with the adhesive properties of a slower-setting epoxy on the carbon fibre. The Epidermix is an industrial type epoxy/hardener that comes in tins as opposed to tubes. I'm sure it is no different to the Pratleys compounds but I've used it for years now with good results.

[markStockton]

 

The Quick Set epoxy is not ideal. It is better to use Epidermix 372 or a slow-set epoxy.

 

Listen to cycleg, I have a fair amount of experience with aero space composites and you need a good bonding epoxy for this job. I was going to recommend Epidermix as it is about the best you can buy at a local hardware store.

 

Another tip, clean up both areas before bonding with some medium sandpaper on the bonding surfaces. Also clean with accetone and allow to dry properly before bonding.

 

[markStockton]

 

The Quick Set epoxy is not ideal. It is better to use Epidermix 372 or a slow-set epoxy.

 

It'll be nice to know why? I'm not familiar with Epidermix - sounds like it'll glue skin?

 

Epoxies are formulated differently to achieve different results. However a general rule of thumb is that a slow cure epoxy will provide higher strength than quickset. Also Epidermix  is industrial grade while Pratley is formulated for home use (much lower grade). In fact I can't tell the difference between Epidermix and aero space grade bonding epoxies, it is that good. However be warned it is not cheap.

 

Also epoxies tend to soften when exposed to extreme heat, however the temperature point where this happens with the Epidermix is much, much higher then Pratley. You could have Pratley quickset reach it's turn point on a very hot day if the bike has been in the sun a while. 

 

[Johan Bornman]

Epoxies are formulated differently to achieve different results. However a general rule of thumb is that a slow cure epoxy will provide higher strength than quickset. Also Epidermix  is industrial grade while Pratley is formulated for home use (much lower grade). In fact I can't tell the difference between Epidermix and aero space grade bonding epoxies' date=' it is that good. However be warned it is not cheap.

Also epoxies tend to soften when exposed to extreme heat, however the temperature point where this happens with the Epidermix is much, much higher then Pratley. You could have Pratley quickset reach it's turn point on a very hot day if the bike has been in the sun a while. 
[/quote']

 

Mark, you're scaring us with all this talk of formulations, aerospace, extreme heat and high grade mixes.

 

As I said, the particular application is not challenging at all. A drop-out already has a good mechanical fit inside the fork and just requires a little bit of bonding to hold it there. There are no large stresses placed on the adhesive in that situation that requires something special.

 

Go or the slow-cure if you must, but I can't see why someone should fork out more money for no more benefit. Pratley epoxies are stable up to 100 degree C. That's plenty hot. The only situation I can envisage where a bicycle will reach 100 degrees is if the drop-out is positioned right behind the exhaust pipe when the bike is transported on the back of a car. However, it'll also boil the grease out the hub and probably blister the paint on the fork.

 

Anyone working with household epoxy doing all the sensible things such as ensuring a good mechanical fit, some roughening of glazed surfaces and cleanliness (acetone is good, as you say, and so is some rubbing alcohol or any non-oily, volatile solvent.) will have a successful repair.

 

Had the problem been the BB or downtube lug where stresses are applied with each cycle, then we could have brought out the strong stuff. The higest stress a drop-out will ever experience is when the bike is hung one one of those bike hooks from its front wheel.

 

 

 

[markStockton]

I really doubt the 100deg C claim on Pratley Quickset. I went to the web site to find a data sheet, but low and behold nothing. Personal experience has shown that Pratley's TG (temperature threashold) can be reached at 50 to 60 deg. The epoxy doesn't disolve or anything major, it just softens and becomes rubbery and looses a large amount of it's structural properties.

 

However you do raise a valid point that a drop out has a good mechanical joint already. 

 

BTW - The problem with Pratley Quickset is more prevelant in the clear version, the white is 10 to 20% better. 

 

[Johan Bornman]

I really doubt the 100deg C claim on Pratley Quickset. I went to the web site to find a data sheet' date=' but low and behold nothing. Personal experience has shown that Pratley's TG (temperature threashold) can be reached at 50 to 60 deg. The epoxy doesn't disolve or anything major, it just softens and becomes rubbery and looses a large amount of it's structural properties.

However you do raise a valid point that a drop out has a good mechanical joint already. 

BTW - The problem with Pratley Quickset is more prevelant in the clear version, the white is 10 to 20% better. 
[/quote']

 

I just e-mailed the national sales manager regarding data sheets. It peeves me when these basic things are not on a website.  At lleast the paint companies have a call centre for that type of thing.

 

Their instruction brochure says 100 degrees but they don't explain what happens in the run-up to 100 degrees. I'll go with your personal experience here since I've not had the opportunity to fix something hot.

 

So, lets update the OP then.

 

1) Go for slow set, time is not of the essence.

2) Confirm that the drop-out has a good fit in the fork.

3) Clean off loose stuff inside the fork and on the drop-out.

4) Abrade the surfaces a little bit if you can.

5) Use acetone or alcohol to clean off any greasy residue. Avoid nail polish remover as this is acetone with oily stuff mixed in to keep your hands nice and smooth. Get pure acetone from your hardware shop.

6) Make sure the set is done with the wheel in place, properly aligned and clamped by the brake.

7) To make sure the expoxy flows into all the necessary cavities, keep the little tubes in your underpants for 10 minutes prior to the operation. That should bring the expoxy up to about 30 degrees at which it flows nicely.

8) Mix it like crazy just before applying since that makes it less viscous for a few seconds and it will flow better. The stuff is thixiotropic, which means it flows better whilst agitated.

9) Wait overnight before riding.

 

Any other steps guys?

 

 

 

 

[cycleq]

Is this a fork dropout or a stay dropout? If it is a stay dropout and one of the stay joints has failed, prudence would dictate removing the whole dropout and rebonding both stay joints for the sake of safety. But this would involve the application of heat to the aluminium dropout to loosen the fixed joint!!!!! Not a job I'd recommend to a beginner. Also, if it is a stay joint, getting the dropout clear of the loose stay to do the prep will be a nightmare short of removing the whole dropout. Back to the heating torch!!!

Perhaps the op can give more info?

[Icycling]

As indicated above probably the hardest part of the job is cleaning and preparing the surfaces. If the lug is completely lose than it not so dificult, but if is still attcahed to part of the frame it becomes quite difficult.

[markStockton]

 

 

Any other steps guys?

 

Most epoxies benefit from what is called a post cure. What you do is slowly heat the part up over an extended period of time and let it cool gradually. It re-alligns the molecules in the matrix to make a stronger bond (or something).

 

As I don't have an autoclave I simply take the part (if large), at least 12 hours after initial cure and loosly wrap it in a black garbage bag. Place it in the garden where it will see sun almost the whole day. If the part is small I post cure it in the oven on warmer function over night.

 

JB, nice trick on warming the tubes, but remember if using a quickset it reduces the pot life or working time considerably. However it does make a stronger bond.

 

You can also heat the part immediatly after assembly with a hair dryer. This also helps the epoxy flow better.