Cracked carbon frame

[Cowsham]

I'd buy this
https://www.ebay.co.uk/itm/Carbon-Fibre ... SwZb5bSQmy

then find a bit of wooden dowl about 15mm dia

https://www.amazon.co.uk/dp/B07KWC4DV3/ ... UTF8&psc=1

Or maybe a bit of 15mm copper plumbing pipe to simulate the stay.

Then practice putting the wrap and resin on.

There's a technique I developed myself using a square of a plastic from a shopping bag ( the slightly heavier type but not the heaviest weave type ones just a plain plastic one.)

I start stippling on the resin and once it's all well wet I wrap the plastic bag over the repair to get a smoother finish to the job and then peel away the bag once the resin gets to the gel stage. If you leave it till it goes fully hard the bag is there to stay.

People will think tesco has started making bikes

This means the bond is stronger and the finish smoother so there's less rubbing down to do and if you need to put more layers on that's easier too.

[KM2]

I agree with Jamesh
You are not dealing with a catastrophic failure of one main tube, such as a fork column or down tube.
If you are going to consign it to the bin, just try it. Skills learned etc etc

[DevonDamo]

That's what I'd do -- done plenty of fibre glass repairs on stuff but never worked with carbon fibre mats before -- is it the same resin ?

As I understand it, you use the same resins with carbon fibre as you've used with fibreglass, i.e. polyester or epoxy. (Obviously, epoxy is by far the better option although more expensive.) Like you, I've got a lot of experience with fibreglass - both for repairs as well as manufacturing. I took a bit of a gamble with repairing alloy bike frames and an alloy casting on suspension forks because I couldn't find a straight answer on whether epoxy/glass would stick to alloy - it did. Fibreglass can give you just as strong a repair as carbon, providing you put in extra wraps as appropriate. In the case of the OP's frame repair, there's tonnes of space available, so I'd happily repair that myself with fibreglass - however, I'm probably a bit less concerned about my bike's weight and appearance than your average carbon road-bike owner, so I guess using carbon would be most people's first choice - maybe even using vacuum-bagging to maximise adhesion, minimise the size of the repair bulge and give it a sleeker finish?

(There are a few engineers in our mountain biking group, all of whom were prophesying doom when I showed up with the above-mentioned repaired suspension fork. That was a year ago, and since then they've watched me progressively break every other bit of the bike whilst my massively over-engineered fork repair stays as good as new.)

[fastpedaller]

The repair highlighted 3 above looks to be ok. I'm experienced with GRP, but not carbon..... I'll add my 2'penorth anyway
After abrading the surface of the tube I'd clean it with acetone. I'd not bother with the filler unless it was so big that the fabric wouldn't bridge it. A small hole could be initially filled using as small a patch as possible ie only just bigger than the hole, pre-wetted with the resin - carefully place in position and leave it to dry. The next day start the layup as described by the guy in the article. As he said after the event, smallest wrap first, leading to larger. It needs to be epoxy resin for Carbon (not polyester). The other thing I'd do is just use some more epoxy resin instead of the clearcoat - just brush it on and after it's fully dried you can polish it with wet & dry paper then cutting compound. As others have said, I'd also not chance a repair of this type on a main-triangle tube or fork. Also, I'd avoid it if the repair was to the chainstay and seatstay on the same side, but in this case it looks to be doable.

[gregoryoftours]

(There are a few engineers in our mountain biking group, all of whom were prophesying doom when I showed up with the above-mentioned repaired suspension fork. That was a year ago, and since then they've watched me progressively break every other bit of the bike whilst my massively over-engineered fork repair stays as good as new.)

Would you mind posting some photos of your fork repair? I'm really interested.

[DevonDamo]

Would you mind posting some photos of your fork repair? I'm really interested.

I suspect I'm going to regret posting a photo of possibly the ugliest repair anyone's ever inflicted on their bike. The repair is because that arch, which connects the lower legs together had completely snapped when I went down a steep drop and landed heavily on my front wheel. I decided to try repairing it because the cheapest replacement parts I could find second-hand (at the start of the first lockdown) were £300 - more than I paid for the bike. You're looking at around 10 wraps of heavyweight fibreglass tape and I just left it as-is after having removed the cling-film and gaffa tape I'd wound it in. That was a year ago, and since then I've been using this cross-country bike, with only 100mm of fork travel to do downhill trails on which everyone else seems to be using at least enduro bikes with 160mm of travel. I've been over the same drop which broke the arch in the first place many times since and the ugly repair is still going strong...

[JohnW]

As far as I can see, that's a very straightforward fibreglass or carbon repair. Because of its location, you can easily sleeve the broken section, and there would be no limitation on how long you wish the sleeve to be or how thick you want to lay it up. I.e. you can choose how strong you want it to be.

That's what I'd do -- done plenty of fibre glass repairs on stuff but never worked with carbon fibre mats before -- is it the same resin ?

I don't believe it is the same resin - but the issue is as much the stresses as the material - if not more.
It's the fibres that take the load, not the resin.
As for a sleeve - it would have to be a perfect fit, and tight enough but not too tight.
Tight enough to avoid 'gobble'developing, but not so tight as to create new stresses.
I submit that GRP and carbon are different.

[DevonDamo]

I don't believe it is the same resin - but the issue is as much the stresses as the material - if not more.
It's the fibres that take the load, not the resin.
As for a sleeve - it would have to be a perfect fit, and tight enough but not too tight.
Tight enough to avoid 'gobble'developing, but not so tight as to create new stresses.
I submit that GRP and carbon are different.

I'm getting my information on the same epoxy resin being used for both carbon and fibreglass from the side of my West System 105 epoxy containers - where are you getting yours from?

Doing this repair wouldn't involve 'fitting' anything. The term 'sleeve' is just shorthand for describing what's posted in the various descriptions and video above - i.e. externally wrapping a broken part. Once wrapped, it's a perfect fit, and you can't make it too tight because you're just wrapping wet material around something and waiting for it to dry. The drying process isn't evaporative - it's a chemical cure - so there's no shrinkage.

I'm glad you've submitted that GRP and carbon are different - at least that's something we can agree on. In answer to my earlier question: what was your reason for suggesting that the OP's frame wasn't repairable?

[[XAP]Bob]

Classic, chain stock in the derailleur wheel after the whole mechanism turned clockwise and hit the rear triangle, breaking out of the hook, of course

So it's a known cause, with a single point of failure on the carbon.

I can't think of a better case for a repair job. It won't look as elegant, but there is no reason it can't be made even stronger than before fairly easily.

Of course the bigger question is whether the mech is ever likely to take a new direction in life again - do you know what caused that?

[Jamesh]

I don't believe it is the same resin - but the issue is as much the stresses as the material - if not more.
It's the fibres that take the load, not the resin.
As for a sleeve - it would have to be a perfect fit, and tight enough but not too tight.
Tight enough to avoid 'gobble'developing, but not so tight as to create new stresses.
I submit that GRP and carbon are different.

I'm getting my information on the same epoxy resin being used for both carbon and fibreglass from the side of my West System 105 epoxy containers - where are you getting yours from?

Doing this repair wouldn't involve 'fitting' anything. The term 'sleeve' is just shorthand for describing what's posted in the various descriptions and video above - i.e. externally wrapping a broken part. Once wrapped, it's a perfect fit, and you can't make it too tight because you're just wrapping wet material around something and waiting for it to dry. The drying process isn't evaporative - it's a chemical cure - so there's no shrinkage.

I'm glad you've submitted that GRP and carbon are different - at least that's something we can agree on. In answer to my earlier question: what was your reason for suggesting that the OP's frame wasn't repairable?

Fiberglass and Carbon fibre are different cloths one cheaper and weaker the other expensive and stronger.

Polyester and epoxy are different resins again one weaker and cheaper than the other.

You wouldn't ever use polyester with carbon fibre but you sometimes use epoxy with fiberglass espically where you are bonding it to wood. Polyester isn't a very good glue to anything apart from fiberglass and itself.

West is the original make of epoxy a bit like araldite.

I'm a bit rusty on composites!

Cheers James

[alexnharvey]

Get it repaired or sell/give it to someone who would be willing to pay to have it done it can do it themselves. If you use the professionals it should be an invisible repair.

While you can use polyester with carbon and other more exotic fibres, epoxy is typically used. I think you will get a better bond too. The important thing for strength and lightweight is squeezing excess resin and air from the matrix. One DIY method is to use perforated tape or films which are wrapped around the repair with sure to absorb the excess on the outside. Vacuum bags are another way and I imagine you can use inflatable kits to apply pressure too.

[Orbearacer]

Many thanks to everyone who mentally supported me that I can do it myself, especially because I got a quote from Surrey for around 300f.
I will try to fix it, it's not rocket science, which I knew from the beginning, but I just needed to make sure, thank you for the tips and remember to replace the wobbly pulley wheel in the derailleur because it's the whole thing because of it.

[Orbearacer]

Many thanks to everyone who mentally supported me that I can do it myself, especially because I got a quote from Surrey for around 300 pounds without painting.
I will try to fix it, it's not rocket science, which I knew from the beginning, but I just needed to make sure, thank you for the tips and remember to replace the wobbly pulley wheel in the derailleur because it's the whole thing because of it.

[hamster]

It will be epoxy not polyester resin. If you've done some GRP using SP or WEST resins then it's the same. A lot of carbon fabrication uses pre-preg and vac bagging. If you are familiar with what I've written then it's similar. But it's a lot more involved than (say) glassing up a rust hole in a car.

[Lookrider]

Try the lads at CARBON REINCARNATION
there in the Lancashire area ...miles from London I know...its a mere scratch to them lads
Check pics if there repairs online and speak to them
Very unhelpful members saying throw it in tbe bin and buy steel
The poster asked for help nothing else