Does it make any sense? Obviously you can build them strong enough, but once you've done that, are there still any weight advantages? And will they be as durable (long lasting) as other more common materials?
read a couple of years ago about a GT one being stronger than alu one by quite a margin, no weight savings from memory just extra stiffness, don't know if I'd bother being a common man and all but a racer maybe
I am currently studying composite fatigue - Carbon fibre has AMAZING fatigue resistance, far better than any metal (Although when it goes there is no warning)
This coupled with the fact that most engineers don't fully trust composite materials and hugely over design what they are doing (Note: GROSS GENERALISATION) I would suggest that any composite structure properly designed will outlast its metallic equivalent.
That said out of plane loading (blunt face impacts) can POSSIBLY cause serious problems leaving fractures that can only be detected by serious bits of kit.
Sorry if I bored anyone!
It's actually pretty impressive the lengths the top teams will go through to loose weight; Ti bolts, roadie saddles are just the start of it, and when Steve Peat won the world Champs last year by fractions of a second, you can understand why. Given that carbon makes a lot of sense, durability isn't really an issue, if it fails as you cross the line, perfect...
Haha... Maybe if you've got a team of people and monies behind you, but if you're after the top of the range to last forever then it's as good a route to go down as any metallic structure (Assuming the layup has been designed right)
One of the comics has a feature on Steve Peat's bike. 3 Ti brake disc bolts per wheel, no dust seals or grease on any of the bearings, just oil.
I would echo drdomrob, awesome in fatigue, I don't think the impact thing is a problem, the kind of impact to damage a carbon frame would damage a steel or aluminium alloy frame too. All power to them.
toys19... not entirely true, when CF gets hit perpendicular to the fibre alignment interlamina cracks can develop due to matrix failure. Although these are similar to the sort of cracks you get in metallic structures, the way they cause failure is completely different.
That said, if the layup has been designed right then it should easily survive such an impact and cause no real weakening of the structure. The problem is that the damage can't often be seen on the impact outer surface, but comes up as rippling on the back face, or inside the frame in this case. This makes it difficult/impossible to monitor. As long as there are no similar impacts where these delaminations occur you'll necver know there is a problem, however if another one does occur in the same place you may end up with a significant hole in the frame (Trek I believe now have a metallic strip protecting the frame... Wonder why!)
Metallic structures however, show a nice big dent which can be monitored easily. Or may have no impact on the integrity of the structure at all.
I'd guess the big advantage is being able to put material and strength exactly where you want it, tuned flex/stiffness and all that.
"tron - Member
One of the comics has a feature on Steve Peat's bike. 3 Ti brake disc bolts per wheel, no dust seals or grease on any of the bearings, just oil. "
I think that was just the world champs spec for Canberra, probably not the same spec for all the WC courses.
i'd ask martinxyz, he clearly is an expert in the field judging by his comment [url= http://www.singletrackworld.com/?p=10186 ]here[/url].
to be fair, if a company makes them, i'm sure they will be just as strong/good as an equivalent alu frame. these people are out there to make money and by making fragile frames that break all the time they won't do that.
Wasn't there a video kicking around a couple of years ago when the Ransom was first launched.
It showed a carbon and an alu frame being bashed together, until the alu one failed. Obviously not assuming the cf frame was undamaged, but still impressive to watch, bit like the stan's demo vid.
I think carbon is really coming of age. Either that or companies have cottoned on to the fact you can sell them for exorbitant sums of money. (not that I'm a cynic) Probably a bit of both.
if this forum is to be believed, that hasn't stopped commencal and lapierre.these people are out there to make money and by making fragile frames that break all the time they won't do that.
One of the comics has a feature on Steve Peat's bike. 3 Ti brake disc bolts per wheel, no dust seals or grease on any of the bearings, just oil.
Actually a lot of the top guys do only run 3 rotor bolts all the time, not just at the World Champs.
There's a thing on Bike Radar about it too, he ran 160/140 rotors, amusing when people think 180 fronts are essential on 5" travel bikes, and stripped all the paint off the rims and hubs. Apparently all the work they did meant the bike was so much faster Steve had to change all his braking points and stuff, crazy!
The thing is with composites (and this is true around every composite using industry) is not to use the materials as a black metal, if the fibres are aligned int he appropriate directions they are literally unbelievable materials! Just need some brave and clever composites engineers to build up a fully optimised frame for race use which can then be beefed up a bit for Joe "I break everything" Public......
To be honest I bet fibre glass would be a perfectly good substitute for metallic frames, IF it was built in the appropriate way. Weight saving potential wouldn't be there though.
CF is STUPID expensive still, mostly because our french and american friends (Airbus and Boeing) have bought nearly all of it for their new planes. Thats the main reason for the high cost.
I didn;t break my Giant carbon frame, but my mate broke his alloy one - so based upon the usually STW generalisation...
I'd say that's a good enough correlation!
http://aluminium.matter.org.uk/content/html/eng/default.asp?catid=89&pageid=2144417038
The stiffness to weight ratio of titanium, aluminium and steel are much the same.
The reason for the development of CFRP (carbon fibre reinforced plastic) is that it can offer a higher stiffness to weight ratio.
CFRP was originally developed by RAE Farnborough 40 years ago.
The problem of comparing different materials, even metal to plastics eg CFRP, is that tensile strength can be misleading.
Steel is similarly strong in commpression and tension.
CFRP is relatively poor in compression, but good in tension and very stiff.
A CFRP frame and a steel frame can be made the same weight and the CFRP frame can be stiffer.
A CFRP frame can be made as stiff as a steel frame and lighter, but the strength (resistace to compression and work of fracture) will not be so good.
There have been other attempts to make materials that have higher stiffness to weight ratios than steel etc such as Metal Matix Composites but they can create further problems.
http://www.theengineer.co.uk/video/mechanical-failure-causes-f1-wheel-loss/1001801.article
Boron fibres had their own problems as well.
Id love to rely on composites more, but I just don't trust them, primarily for their interface with areas that require metallic inserts. I've had two sets of carbon cranks, both failed by delamination at the bonded joint. I've no doubt whatsoever of the strength and ability of the material if designed right, but it seems to me that people who should be good at designing with it still have the odd problem. Great flat sheets, fine, but complex parts im not so sure. Get an F1 chassis designer on the job and I'll buy the parts THEY design!
having spent 15 years in F1 much of it in r and d including crash testing i have seem some massive cockups ,,, must say most were due to human influence I.e wrong glue or wrong surface prep prior to glueing , etc.
and this stuff was made in clean rooms with guys in funny hats shoes and dust suits, with the strictest QC . not sure the bike world can have the same Quality control
i have also seen bikes that have had dropouts bonded into swinging arms with fresh air ,,
DrDomRob - Member
CF is STUPID expensive still, mostly because our french and american friends (Airbus and Boeing) have bought nearly all of it for their new planes. Thats the main reason for the high cost.
I was under the impression it was mostly as a result of the explosion in the wind industry worldwide & that boeing & airbus have just accentuated the problem more so than causing it.
frank - The wind industry up until recently were almost exclusively using Glass FRP. (This observation is based on the number of academic articles produced by the industry which were studying fatigue - If you are really interested here is a good place to start! http://www.coe.montana.edu/composites/)
The wind energy industry doesn't give a rats about weight (Generalisation - what I mean is expense is a bigger driver than lightweight + strong), put enough material in and it'll be strong enough.
However aeroplanes have to fly as efficiently as possible. Hence the use of Carbon fibre in MASSIVE quantities (The dream liner is almost completely carbon fibre).
PERSONALLY I believe the blame for the high cost can be planted straight on their doorstep. But that is just my opinion.
Practical answer 1: Carbon can be as strong as you like. Windsurfing stuff is all carbon (masts, fins, battens, boards) and these take a hell of a pounding. Most masts and fins are grooved and chipped but last for years.
Practical answer 2: Carbon has a faster reflex than aluminium. It springs back quicker after a deflection so feels zingier.
Real answer: It's carbon. Carbon is sexy and more expensive. The manufacturers want you to Neeeed it. You Neeeeed it.
Quite probably apocryphal, but I heard that there's enough carbon fibre in one A380 to sustain the bicycle, hockey and baseball industry for a year.
>Practical answer 2: Carbon has a faster reflex than aluminium. It
>springs back quicker after a deflection so feels zingier.
"reflex" - is that a mechanical property? surely it's a function of youngs modulus, section, etc?
my only concern with carbon fibre Dh frames is that it takes the sport another small step away from people who aren't minted.
yes, i know you can still buy good 'cheap' bikes, but some people will feel intimidated, that their 2 year old bighit / stinky isn't good enough to race on, so they won't.
and that'll be a shame.
we need MORE old cheap shonky bikes at races!
A380 has a lot, but the dreamliner is where it's at!
frank - The wind industry up until recently were almost exclusively using Glass FRP. (This observation is based on the number of academic articles produced by the industry which were studying fatigue - If you are really interested here is a good place to start! http://www.coe.montana.edu/composites/)The wind energy industry doesn't give a rats about weight (Generalisation - what I mean is expense is a bigger driver than lightweight + strong), put enough material in and it'll be strong enough.
I don't think this is still current - Vestas on it own used more carbon fibres than Boeing last year, according to a presentation I saw by them the other day.
Fair enough.
I could well be wrong.
Quite probably apocryphal, but I heard that there's enough carbon fibre in one A380 to sustain the bicycle, hockey and baseball industry for a year.
A380 empty weight = 276,800kg
So let's say that half of the plane's weight is structural and carbon fibre (eg taking out all the engine, electronics, furniture, etc - in reality, I suspect that less than half is actually CF)
So that'd be 140,000 kg of CF
let's say that the average CF frame is 1kg , that's 140,000 CF bike frames (ignoring the hockey and baseball industries).
Anyone know how many CF bike frames are made per year?
That doesn't sound like very many, but I suspect it's not as straight forward as that, as you've got to consider resin mixes etc, I suspect that 1kg of carbon as used by Airbus is enough to make more than 1kg of carbon bike parts, if that makes sense!
Seats from a Qantas A380:
[img] 
[/img]
Edit: that appears to be something like 3k, for the seats, even if it's only superficial, presumably they're using 1k if not better for the fuselage. What are most bike frames under the cosmetic layer? 12k?
Oh, I know it's massively simplified but it was really just to get a ROM number to see if it sounded vaguely reasonable.
"reflex" - is that a mechanical property? surely it's a function of youngs modulus, section, etc?
Sure, you can make an unresponsive carbon component but the best carbon frame will have a faster reflex than the best aluminium one
ahwiles - Member
my only concern with carbon fibre Dh frames is that it takes the sport another small step away from people who aren't minted.yes, i know you can still buy good 'cheap' bikes, but some people will feel intimidated, that their 2 year old bighit / stinky isn't good enough to race on, so they won't.
and that'll be a shame.
we need MORE old cheap shonky bikes at races!
To be honest the gulf in funding between various riders at most races is quite apparent, the fact that some will rock up on a shiney new £2.5K frame every season while others do quite nicely on their aging stinky isn't really a factor, take the Session 88, when it came out people were falling over themselves to buy it, 6 months later they were all whinging that they'd bought a 2 grand collection of coke cans full of dents, all the kona's were still rolling with zero complaints...
DH isn't a poor mans sport really, it can be done on a budget if your aim is to have fun, but to be competative you should really be looking to take advantage of any new technical developments, considering a growing number of serious privateers now view a DH frame as a single season investment, the longevity of a Composite DH frame might be less of a consideration than it's weight, plus it's fair to say that more "traditional" DH frames constructed from Aluminium only have a finite life especially when used for racing...
look at it this way with the likes of on-one offering lower cost composite HTs it's only a matter of time before a similar price war happens in the DH sphere...
DH isn't a poor mans sport really, it can be done on a budget if your aim is to have fun, but to be competative you should really be looking to take advantage of any new technical developments
That applies to virtually any discipline of cycling! There aren't that many sports where you won't gain a significant competitive advantage by spending a reasonable amount on kit. Even running seriously will require a lot of shoes!
"reflex" - is that a mechanical property? surely it's a function of youngs modulus, section, etc?
Brant, Indeed. I once read a Gary Fisher interview where he stated that Aluminium had a higher coefficient of damping than steel, hence aluminium had a harsher ride. Made me chuckle.
Don't forget that there is only 1 place in the whole UK that can recycle carbon fibre.
So don't buy on a whim
I don't know the exact composition of the A380's layup (Not even the end customers know that - which is scary really when you think about who will be responsible for repair and maintenance. Bolted aluminium/Titanium reinforcement plates anyone?!), but I would have thought they would be using UD layups in various layers rather than woven mats.
You'll be doing bloody well if you aren't the designer and manage to find out the layup/material specs for the construction! Unsurprisingly these companies are very secretive about such things.
Get an F1 chassis designer on the job and I'll buy the parts THEY design!
[img] 
[/img]
😯
That's the result of pushing the materials to their limits and beyond.
but I would have thought they would be using UD layups in various layers rather than woven mats
Yes, but in places as insignificant as the seats they're still using 3k or similar by the looks of it, which was what I meant, ie they're going to be using shed loads!
sorry, I misunderstood what you were asking. So yes, they are using several shed loads!
Just so I can sift which posters above to give creedance too, can you all please revisit this thread and state your credentials backing up your opinion - e.g. what your doctorate is in, who among you is an F1 engineer?
I don't know why, sometimes I get the sneaking suspicion anyone can post an opinion on the net........
This is a serious request, call it research.
here you go waderider , i agree with you, there is a lot of heresay written here,
no formal qualifications,
15 years in F1 R and D Benetton Arrows and williams
5 years ohlins race service british/world superbike/gp
2 years designer for Marin/whyte
10 worldwide patents as inventor/co inventor in suspension design/air shocks and a combination bicycle bump shock and tyre
still designing bikes and stuff for a number of companies
now working at my local high school as a design and technology technician
DH isn't a poor mans sport really, it can be done on a budget if
your aim is to have fun, but to be competative you should really be looking to take advantage of any new technical developments, considering a growing number of serious privateers now view a DH frame as a single season investment, the longevity of a Composite DH frame might be less of a consideration than it's weight, plus it's fair to say that more "traditional" DH frames constructed from Aluminium only have a finite life especially when used for racing...
I'd disagree that you need a new frame/bike every year to be competitive Ben Reid used to ride a skip circa 06(?) [img] 
[/img]
(Image Plucked straight from google)
He did the World cups on it and Didn't do too badly on it. (Probably why he can do well on the Norco...)
Iain
BUT Ben Reid and his father did a LOT of work to that old frame, cutting seat and chainstays, welding a bit extra in and re-heat treating it to lengthen it. New linkage plates for travel settings and as the old ones broke. Welding plate after plate over cracks as they appeared.
He liked the geometry and is very picky about his bike, but it is fair to say they nursed it through a few seasons racing.
True it wasn't a run of the mill production frame but the point I was making was is you don't need a new frame each season, once you have something that you are confidant on there isn't really any reason to change, the bike makes up a very small part of the overall package in relation to the rider.
Iain