Carbon Ninja

Love the blurb trying to explain the lack of the brain. Lo It"s still there guys, but just the most fundamental part, the inertia valve, is gone! I guess the brain idea is still there with the high threshold to activation curve but the on/off nature will be softened and that has to be a good thing?

My thing is that classified asks you to run a smaller cassette (11-40) to achieve their slightly increased overall ratio difference. But just think how incredibly different these wide-range derailleurs are from the two-by derailleurs of the previous generation. From unsprung b-knuckle pivots to the incredibly long arcs between the b-knuckle and p-knuckle, to horizontal parallelograms, derailleurs have compromised many shift-assisting features in order to manage that super wide delta. Now, with the two-speed hub, surely we will end up using derailleurs that are not optimised for the smaller cassettes needed by Classified? Certainly, the old derailleurs on the smaller cassettes shifted a lot better than the 1 by 12 stuff.

We can custom make for you if you need. Info@carboncraft.co.za

I'll get to answering all the other great questions and comments in a bit. Got kids to pick up. Thank you.

You've motivated me to look again at getting personal liability cover.

I agree on the idea of establishing a regulatory body wholeheartedly. For interest I find that about half of my repair quotes are accepted by insurance. I assume that 50% f people who take on their insurers on the replace or repair issue are successful. I recently had my company name dragged through the mud by a local cyclist in her dogged pursuit of a new frame. In the end it was escalated all the way to the insurance ombud, who ruled in the insurers favour and the bike was eventually repaired. It was a deeply unpleasant experience for me.

In the context of 16 days of activism against violence against women and children, and in the context of all those victims of date rape, and in the interests of general decency and sensitivity toward women and your fellow human beings, I suggest that you offer an apology, not to me (I couldn't care less what you think of me), but to those on this forum who might have read this and been offended. I also think a comment like this should be handled by the forum moderator. It's next level inappropriate.

And, (I think this is really important), we keep an environmentally dirty bike on the road instead of landfill. Carbon fibre is very dirty to produce. It's mostly made from pitch, dirty, oily tar, at huge energy costs. The epoxy resin is full of carcinogens and nasty chemicals... Processing the carbon takes a 700kPa pressurised 120 degree oven! It's much greener to keep it on the road and not waste all of that effort than to scrap it and make another bike from scratch.

I have fabricated replacement head tubes before and bonded these onto the top and down tubes ????????

Wow, my quotations a year ago or so were in the order of R5k/month. I guess the insurers went safe on an industry they did not fully understand? Anyway, as much as you call BS, I am unable to afford it at present.

Never took any offence! ????????

This is possible, simple calculations can be made with composites but the accuracy is not great. What is really needed is an FEA based simulation with a laminate modeler where the directional properties of each layer of reinforcing fabric is modeled along with predicted loads and constraints. This is more of a design tool than a maintenance /repair tool and as such is out of reach of the modestly remunerated... I think a single seat is over R100k/year. Still, it can be done. There is a design code in aerospace called black aluminium. A quasi isotropic laminate of carbon fibre of equivalent thickness to the aluminium more than double the factor of safety of the original part. This was state of the art in the 80's! I think you're right about heuristics and I do think that this approach is prevalent in our tiny carbon repair industry (with some exceptions). It's not present at Carbon Craft though. We learned our craft academically.

I don't have a good answer other than to invite you to engage with me personally, and perhaps to visit my facility to see for yourself what I do. This and check with the public on how well my work is rated?

Absolutely Doc (may I call you Doc)? My father in law is a neurosurgeon, so I know all about both the utterly compelling and reasonable act of collecting multiple professional opinions, but I also see how his 14 years of study and 25 years of experience is questioned by laymen with Google. It makes no sense and is silly. As for professional indemnity, you're absolutely right but as Bogus mentions, it's unaffordable unless you're a private practice medic. That fact alone keeps me well and truly motivated to do the best and safest work that I can. If I could afford it, I would have it.

We build jigs as needed, we have a 3D printer to assist as well as a cnc mill and manual lathe. I agree 100% with you, doing the job properly is absolutely necessary to avoid dangerous and/or annoying comebacks. Your second point I answered in another post.

I can't answer 2, but I can have a go at 1. Bikes use more, thinner laminates as they increase in quality. When I am repairing, the process of removing the cracked and delaminated carbon allows me a pretty good view of how the manufacturer designed the laminate. Then, within the limitations of the material available to me, I emulate as far as possible the original layup. I do this to minimise the creation of stress raisers that will crack the frame layer and to keep the frame strength and stiffness the same. For this reason I keep stock of a variety of carbon facrics in various areal masses and weaves. I keep plain, twill, satin, ud and biaxial fabrics in stock. I keep some of them in high strength carbon, some in standard modulus, high modulus and some UHM fibre too. I also keep various epoxy systems that are utilised appropriately. Your specific question on Bianchi CV - a single and outermost laminate of a 163gsm carbon/aramid balanced plain weave over the structural ud HM fibre is what I usually do, and as far as I am concerned this is what Bianchi do too.

I can well understand how you might be incredulous, and I am glad that you acknowledge that you are a layman. This is where trust in the expertise that I have (and you don't) is required. Fortunately no one forces you to ride a repaired frame, if you can't get your head around it then you must simply opt for another solution. As for the science, there's plenty but I'll make an attempt to summarise : CFRP or carbon fibre reinforced plastic comes essentially in two versions, thermoplastic and thermoset. Bikes are made with thermoset resin and this is imminently repairable because it is imminently bondable. New frames are made in multiple pieces that are glued together, typically stays are glued via lugs to the one piece front triangle. The join is then "taped" to make it one piece. In a job like the one that is the subject of this thread, I would emulate this process by creating an internal lug that joins the two halves of the head tube together, then I would tape the two halves. (Taping is just a term for wrapping carbon fabric on a closed surface, it's not taping like sellotape)! I have a big that maintains alignment and the lug that I make is largely geometrically conformal with the internal surfaces of the original head tube. In this way a repair adds only 10s of grams to the original mass, rather than hundreds. Appropriatly selected reinforcing carbon fabric and epoxy matrix then merge the two halves of the head tube via an appropriate consolidation and fibre volume fraction maintaining process. I use VI mostly, sometimes vacuum bagging. You won't find insulation tape in this workshop, no "Pap en Lap" as my colleague Anton calls it! My methods are all derived from repair method standard best practice from the civilian aerospace industry. These manuals are published by Boeing, Airbus and so on for technicians to make repairs to their planes which are increasingly composite intensive. Oh, and lastly, I've had the quality of my laminates tested independently. I did this to ensure a low void and high fibre volume fraction laminate a was being repeatably achieved by my repair methodology. Lastly, I forgot to add, the analogy with orthopedic science is not totally valid, medicine is not an exact science where composites are, pretty much. There are many variables and unknown unknowns in the world of medicine, but luckily in this arena, its far more exacting.

Absolutely, that's just good practice. All I'm saying is that, (and maybe I should just speak for myself since I agree that there is, some fly by night work out there), is that I am qualified to make the determination. As laymen, you have an opinion but that it might be misinformed. We as repairers shouldn't be disparaged by the public because their insurers aren't playing ball.

I can only speak for myself. I hold a Bachelors degree in mechanical engineering and five years of post graduate specialisation in composite processing, prototyping, process development and repair. There is some really poor work going on that is proudly posted on social media (locally and internationally). Some of you may know that I got into some legal hot water recently calling out some poor workmanship on a public platform. (OK, shouldn't have done it like that but I feel I have a responsibility). I fully agree with the suggestion that we be accredited and graded and quality checked by an external auditing body.

Insurers don't involve me with the client, in fact I often don't ever know who the client is. On the odd occasion that the insurer does involve me directly in client discussions, you're exactly right, it's not fair and always unpleasant. The owner often thinks that I'm working with insurance against him, which is patently not the case.

In this specific case, the way that I would repair it would result in stiffness and strength being the same as or slightly more than the original, aesthetics would be restored to original quality and the mass of the frame would increase by 50g or so. So by that metric, no, the owner is no longer in the same position by 1 of four factors.

I'll be honest, I don't fully understand your question. The way I see it is that Carbon Craft is a service provider and my job is to repair carbon fibre. It doesn't matter who the client is, provided that I treat every job in the same manner. That insurance utilises my services too is incidental. (Out of interest I looked at my books now, insurance makes up less than 2% of my turnover). If I have not answered your question adequately please clarify for me? Thank you!

The thing is, and I say this most respectfully, is that what I've read here amounts mostly to unqualified and inexpert opinion. I submit, again respectfully, that in order to make a determination on the suitability of a frame for structural repair you should be adequately qualified in the field of composite repairs. As laymen we deal unquestioningly with doctors diagnosing and treating our health, because they're specialists. If a qualified composite repair specialist says something can be repaired safely, then surely they deserve that same courtesy? Obviously I say all of this without considering the context of what-you-pay-for versus what-you-get in terms of insurance. That's a completely different topic. I, as a carbon repair specialist am approached by insurance to provide quotations on repair costs and this I do honestly and fairly. My company has however been victimised by irate insured cyclists a few times, as they pursue their goal of having their bike replaced instead of repaired. I can tell you, it's not fun...