Fear of carbon

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MikeF
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Re: Fear of carbon

Post by MikeF »

The OP is concerned about carbon forks with an aluminium frame. She didn't say she's concerned about the frame. I haven't a carbon anything bike, as I too have concerns.
"It takes a genius to spot the obvious" - my old physics master.
I don't peddle bikes.
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[XAP]Bob
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Re: Fear of carbon

Post by [XAP]Bob »

hamster wrote:
[XAP]Bob wrote:
NATURAL ANKLING wrote:Hi,
Worryingly however, the boat’s designer Adrian Thompson said getting the balance between strength and lightness was tricky: “Simply, a boat that is impossible to break will never win” he said.[/i]"


Of course it could - particularly if the weather was such that the competition all failed...


Bombproof boats are called cruising yachts. When you see how fast a racing boat goes by comparison you see Thompson's point. It's an unhappy owner who will be told his boat will only win in the 1% eventuality of a hurricane wiping out the entire fleet. However, to finish first, first you have to finish. So it has to be just strong enough. The winning Whitbread boats in the 1994-5 race all suffered severe delamination...but still won. Nowadays it's not a problem as the material specifications and scantlings are better understood.

If you've never seen a foiling Moth then you ought to. Desperately fragile, but 30kts from an 11 footer is impressive. Racing offshore in the past there was one desperately slow 33 footer, which one day suddenly picked up her skirts and shot past the majority of the fleet downwind. Shortly after she rolled over, the burst of speed was the aftermath of the keel falling off. :D

Bben in an RS400 on the plane, been oit watching my brother race 49ers with the olympic team.

My point was exactly that - racing isn't all there is to cycling, so that 1% isn't too relevant.
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fastpedaller
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Re: Fear of carbon

Post by fastpedaller »

beardy wrote:
Now that CF bikes are out there in large numbers what happens to them is what material scientists will be looking at, just as the rest of us are. I have seen enough old and high mileage carbon fibre forks out there that I am no longer worried and will not replace mine at five years as I originally thought I might when I bought the bike.


That wouldn't seem unreasonable......... If CF breaks in a sudden and non-progressive way, It's probably logical to say that it doesn't show a gradual deterioration ie. it isn't time dependant. The limiting factor is the shearing stress. If that level of stress is reached under 'normal' conditions, which have been met or passed previously, would it seem reasonable to say that deep scratches/stone chips or other damage are the key to why the material fails? either by creating a stress raiser by their very nature, or the means by which moisture is able to enter the laminate?
pete75
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Re: Fear of carbon

Post by pete75 »

Brucey wrote:the engineers at Ferrari have knowledge of and control over their manufacturing processes. Car chassis design is interesting because it is mostly driven by stiffness rather than strength. When the strength and energy absorbing properties are most important, you are having a crash, and it only needs to be strong once.... After that it goes in the bin, which is how it should be.

People persistently refer to 'it' as if 'it' is always the same stuff. It ISN'T; no more than Cr Mo is the same as 753 is the same as gas pipe, or good welds are the same as bad ones. You can buy some right crap.

Barone's crash is quite telling because he and his team obviously spent some time planning his record attempt, and thought that they knew what they were doing. It is a perfect example of how things can go wrong despite careful planning. Had Barone's team taken style tips from other bikes meant for that kind of use he should have wound up looking at MX bikes. They are almost invariably still made of welded metal tubes, they still use wire spoked wheels. I can only assume that MXers are not taken in by the hype, for as we all know CF MX bikes would be 'so much better' because CF is always 'perfectly strong'.... :roll:

cheers


Most carbon frames seem to be made of Toray T700/T800 type of CF so it usually is the smae stuff.
A bike made out of any type of material which is made badly will fail not just carbon fibre. No material is always perfectly strong but you seem to imply that CF never can be and will always fail. Your arguments might have a bit more merit if you could come up with some failure rates for carbon cycle frames/forks which haven't been crashed or mistreated. I suspect it is low.

BTW YOU may buy some right crap most of us here tend to avoid it.

If by MX bike you mean what is usually called a scrambles bike then of course any bicycle modelled on a motorbike will be stronger than one designed as a bicycle.
'Give me my bike, a bit of sunshine - and a stop-off for a lunchtime pint - and I'm a happy man.' - Reg Baker
tim-b
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Re: Fear of carbon

Post by tim-b »

Hi

Rule 1) It all breaks if you mistreat it enough / over stress it enough / design or manufacture it badly enough

All materials can break suddenly and without warning. I accept that steel is sometimes better in this regard, so let's manufacture every bicycle component from steel. A front tyre blowing out, or handlebars breaking can be particularly nasty. Steel tyres anyone? Or is that going back in time to velocipedes and a retrograde step in the development of the bicycle

Of my last four bikes three have CF forks (number four is an MTB with a suspension fork). All four have alu handlebars (I've had steel Cinelli bars and stem in the past) and all have tyres with a rubber tread

I understand rule 1, and I'm happy

Regards
tim-b
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maxcherry
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Re: Fear of carbon

Post by maxcherry »

MikeF wrote:The OP is concerned about carbon forks with an aluminium frame. She didn't say she's concerned about the frame. I haven't a carbon anything bike, as I too have concerns.



Sorry my fault. It was a general question about carbon bikes as well as the fork as some bikes
Come with carbon forks.

I sincerely apologise for starting this thread :(
Honestly chaps, I'm a female!
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easyroller
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Re: Fear of carbon

Post by easyroller »

maxcherry wrote:I sincerely apologise for starting this thread :(


Don't apologise. ;) It makes for interesting reading!

A thread about this new fangled carbon voodoo on CTC forum always brings about heated debate...
maxcherry
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Re: Fear of carbon

Post by maxcherry »

easyroller wrote:
maxcherry wrote:I sincerely apologise for starting this thread :(


Don't apologise. ;) It makes for interesting reading!

A thread about this new fangled carbon voodoo on CTC forum always brings about heated debate...



Thank you :)
Honestly chaps, I'm a female!
Brucey
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Re: Fear of carbon

Post by Brucey »

just to set aside some of the fanciful nonsense I am reading;

To be the 'same stuff' or 'strong enough' you must use;

- the exact same fibre types
- the same resin
- the right lay up
- the right processing

Most designs use sections that are bonded to one another or to metal parts. Here you must use;

- the right preparation of parts for bonding
- the correct materials for bonding
- the right bonding conditions

All stages in the manufacturing process (even simple stuff like materials supply and storage) are critically important to ensure that you have a quality product and ideally everything needs to be monitored during processing e.g. by manufacturing control testpieces, some of which destructively examined and some of which are retained.

All the above needs to be carried out to manufacture a design that is competently thought out in the first place, using materials that are chosen correctly in the first place.

If you look at other products that absolutely must not break in service then arguably something like a prop for an aeroplane is comparable; it contains a similar proportion of metal and CF, and has similar constraints surrounding the layup, processing, bonding etc. For commercial aircraft, such props cost a lot more than even a good quality CF bike frame does, even though the lay up and processing steps are mostly a good deal simpler. You can buy smaller props for model aircraft etc and they are a lot cheaper; cheaper per lb of product. The difference is in the materials specification and the QA in manufacturing.

If you think that a 'made to the lowest cost' CF frame (which is the bulk of those sold, although they may not be badged as such...) is made with the highest levels of QA in place then you would be mistaken. Other complex products (TV sets etc) can be tested as they roll off the production line (and if they fail later it doesn't kill anyone, it just costs a little money), but with a CF bike frame there isn't that much you can do when it comes out of the end of the process, which is why the in-process QA is important. NDT of complex structures is both difficult and relatively pricey, so AFAICT bike frames are not routinely X-rayed (unlike every jar of jam you buy in the supermarket... :roll: ) and even if they were, it wouldn't tell you that much until they had seen some service, because many disbonds won't be apparent before then.

The designs and materials used are very often simply not intended to withstand the conditions that a typical rider will inflict on them in a British winter; a very common problem is that (in good part due to corrosion) the aluminium parts come disbonded from the CF parts and this causes the frame/fork to fail in service.

Riders who buy good quality equipment (with a decent warranty), change their bike regularly and do very simple stuff, like actually use mudguards, and/or wash it after it has been out in the salty crud, or inspect the parts from time to time are at significantly less risk of having trouble or from coming to grief as a result of it. But that is not the same thing as having a perfectly reliable material. Indeed I've even seen riders who say that they prefer CF bikes because they don't have to clean them; they couldn't be further from the truth.

With other materials the signs of impending failure are often a little more apparent. This is true of both in-service failures and those arising from manufacturing problems. For example look at the Orange fork recall that has been posted elsewhere on this forum; you just need a tape measure to see if your fork is affected; it is a basic manufacturing cock-up. By contrast when CF forks are recalled (which it seems is quite often, and at vast expense... at least one CF fork manufacturer has gone bust through this...) then you ultimately just have a serial number on the fork to go by if there is a batch problem; you usually just can't tell if the fork is sound or not before it actually breaks.

Now I use CF parts myself so I'm not saying 'they are all bad' or anything. I think it can be a fantastic material when used in the right way. But I do question people's rationale when choosing it (indeed any really lightweight material for say, daily use) and when I see people assume that it is all the same (regardless of origin or cost) and that it will survive any amount of neglect and abuse then I worry, and for very good reason. And when I see people assume that one CF product will be the same as another just because the fibres were made by the same company, it just makes me laugh; it is a bit like saying that a top chef's cod provençal must be the same thing as a fish finger because it is 'the same fish from the same sea'.

I could write a book on this stuff and it wouldn't alter many people's views on this topic for the reasons I previously described. So I'll go back to my simple advice;

Caveat Emptor.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
mig
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Re: Fear of carbon

Post by mig »

would it now be the case that CF is the cheapest material to use to mass produce frames?
Brucey
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Re: Fear of carbon

Post by Brucey »

it might be close to that, which is why the pressure to reduce costs in other manufacturing steps is so intense.

Unfortunately CF layups for 3-D parts are complex and potentially time consuming to do well, so the highest quality and lowest labour costs are (probably quite rightly) considered to be 100% incompatible with one another. Perhaps automation will be the answer, but I don't think it is widely used as yet.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
reohn2
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Re: Fear of carbon

Post by reohn2 »

My non technical cynicism goes along the same lines as Brucey's.I've heard people say the similar things about their CF bikes namely that they won't rust or be affected by inclement weather and they're riding without mudguards in such inclement weather(why anyone would do is anyone's guess but that's for another thread).
I'll state my opinion as before, CF is strong but it's strength is affected by everyday use ie;impact damage and deep scratches,etc.
In the everyday rough and tumble of life what would certainly result in a ding or a paint scratch at worse to a metal(alu,steel,Ti)frame or fork,could ruin a CF frame or fork and it's that,that makes CF unsuitable for bicycles in anything but a Sunday best situation IMO.
All references to pro racing is like comparing a ordinary car to a F1 racing car in theat such machines are developed and used with a single purpose in mind,to win a race whilst promoting a manufacturers brand name end of.
Also if anyone thinks when they buy a bike of the same make/model that the pros are riding they're deluded.

If people wish to use CF that's their choice,mine is to err on the safe side.
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mig
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Re: Fear of carbon

Post by mig »

so close to the cheapest to manufacture , maybe the most sought after by many & most advertised by the racing scene.

therefore what else are producers going to make, shops going to buy and sell to riders. if they are chipping away at costs by using less fibre, more resin, thinner.....lighter...blah blah then buyer beware indeed.
Brucey
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Re: Fear of carbon

Post by Brucey »

ironically it is the popularity of air travel and other global economic factors that will affect the cost of CF materials down the line. CF is probably pretty cheap right now (unlike a few years ago) because there is likely to be an overproduction of CF (or at least excess capacity) at present. The other big users are other 'sports equipment' and the new generation of CF airframes. When CF airframes were first built there wasn't enough capacity for a while but there is now, I believe.

If it isn't an Olympic year, the economy is a bit iffy, and people are put off international air travel (crashes, terrorism, Ebola, etc) then I'd guess that CF is not in such high demand and will be cheap for a while.

cheers
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~~~~~~~~~~~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~
pete75
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Re: Fear of carbon

Post by pete75 »

Brucey wrote:.

Now I use CF parts myself so I'm not saying 'they are all bad' or anything. I think it can be a fantastic material when used in the right way. But I do question people's rationale when choosing it (indeed any really lightweight material for say, daily use) and when I see people assume that it is all the same (regardless of origin or cost) and that it will survive any amount of neglect and abuse then I worry, and for very good reason. And when I see people assume that one CF product will be the same as another just because the fibres were made by the same company, it just makes me laugh; it is a bit like saying that a top chef's cod provençal must be the same thing as a fish finger because it is 'the same fish from the same sea'.

I could write a book on this stuff and it wouldn't alter many people's views on this topic for the reasons I previously described. So I'll go back to my simple advice;

Caveat Emptor.

cheers

You've certainly given the impression that you think CF is all bad in previous posts - that's why I thought your views were wrong.
'Give me my bike, a bit of sunshine - and a stop-off for a lunchtime pint - and I'm a happy man.' - Reg Baker
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