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zunkus
09-01-09, 10:02 AM
(http://motorcycle.advertserve.com/advertpro/servlet/click/zone?zid=19&pid=0&lookup=true&position=1)
In keeping with its heritage, Ducati has been racing a steel trellis frame in MotoGP. Competitors have been racing stiff, aluminum frames. Next year, Ducati will race the Desmosedici GP9 with a carbon fibre frame. Arguably, it goes from the oldest frame design to the most modern in the paddock.


The benefits will be far greater stiffness and predictability from the chassis. Undoubtedly, this will make Nicky Hayden's transition from Honda to Ducati easier, because Hayden was accustomed to a stiffer, aluminum chassis at Honda. Will the GP9 put Casey Stoner back on top next year? Maybe the new carbon fibre chassis is the missing link to Stoner's second World title.


What about road bikes? Does it make sense to have CF frames for road use or are they similar to steel and can shatter from road induced vibrations thus making them less safer than conventional ones? I know it's more expensive to manufacture as it requires hand labour, but if price was not an issue do the benefits outway the drawbacks if there are any?

jambo
09-01-09, 10:13 AM
I'm not sure it's quite that simple. You can make a steel frame every bit as stiff as an aluminium one, it's just that for the same design, it tends to work out heavier. You don't actually want a completely stiff frame either. Flex in the frame and swing arm make up an increasingly important part of absorbing bumps at big lean angles. At 45 degrees of lean, a 10mm bump requires 20mm of suspension travel to absorb it, so a bit of flex helps the suspension out a lot, provided it's controlled and predictable.

Overly stiff frames have caused problems in the past, the Cagiva 500cc GP bikes of the 90's were massively stiff, and the riders claimed there was very little feel for grip because of it. When Honda was racing the SP1, they actually removed 2 of the 8 engine mounting bolts to introduce some flex in the frame, and the SP2's frame was designed to flex more.

There's a company down the road from me called carbontek (http://www.carbontek.com) that used to make a Ducati 916 Frame entirely from carbon. God knows what it cost or if it was any better though, nowadays they seem to just make fairing panels and the like.

Jambo

zunkus
09-01-09, 11:01 AM
When Honda was racing the SP1, they actually removed 2 of the 8 engine mounting bolts to introduce some flex in the frame, and the SP2's frame was designed to flex more.Jambo

Ah that was from Colin Edward's time in WSB, yeah I remember. Totally agree with what you're saying and the fact that Ducati are jumping from one extreme to another baffles me a bit.

Ceri JC
09-01-09, 11:51 AM
Ah that was from Colin Edward's time in WSB, yeah I remember. Totally agree with what you're saying and the fact that Ducati are jumping from one extreme to another baffles me a bit.

Perhaps the logic works along the same lines as the Italians' typical long gap between updates (compared to the shorter one of the Japanese). If you want to maximise the time between updates, you need to make something really cutting edge when it's introduced. So, the old frame was now so dated it needed replacing and they replaced it with something that'd not need replacing itself for a long time? Maybe fifteen years from now we'll be having a similar discussion about why Ducati are still running an old fashioned carbon frame when everyone else has moved onto Adamantium ones. ;)

xXBADGERXx
09-01-09, 02:42 PM
Doesn`t Carbon have a Work life that wouldn`t make it worthwhile using on the street , and once you prang it , it can go either way to be ok or downright Cuffed

SoulKiss
09-01-09, 02:48 PM
Ducati are still running an old fashioned carbon frame when everyone else has moved onto Adamantium ones. ;)

Of course then Ducati will move to Unobtanium

jambo
09-01-09, 02:49 PM
Doesn`t Carbon have a Work life that wouldn`t make it worthwhile using on the street , and once you prang it , it can go either way to be ok or downright Cuffed

Carbon fibre's plenty strong enough to be used in wheels, chassis of very high end cars, and, as it turns out a motorcycle frame if you feel the need.

But if you prang it, the chances are Maidstone Motoliner aren't going to be able to see it back to being OK :mrgreen: Guess if you're in MotoGP it's less likely this is going to be important.

Jambo

Ceri JC
09-01-09, 03:08 PM
Carbon fibre's plenty strong enough to be used in wheels, chassis of very high end cars, and, as it turns out a motorcycle frame if you feel the need.

But if you prang it, the chances are Maidstone Motoliner aren't going to be able to see it back to being OK :mrgreen: Guess if you're in MotoGP it's less likely this is going to be important.

Jambo

I was under the impression that lots of carbon fibre wheels had recommended "shelf lifes" in terms of mileage of typical road use. Sometimes as low as 10-15K miles. Fine for track bikes, not so good if you ride big distances and I imagine this number drop significantly if you're bumping the bike over kerbs etc. with any regularity.

northwind
09-01-09, 05:11 PM
Carbon'd probably have a limited lifespan, unless it was totalyl overbuilt which would defeat the purpose, but the average posey expensive bike doesn't do all that many miles anyway so it probably wouldn't be such a big concern...

Ceri JC
09-01-09, 05:27 PM
Carbon'd probably have a limited lifespan, unless it was totalyl overbuilt which would defeat the purpose, but the average posey expensive bike doesn't do all that many miles anyway so it probably wouldn't be such a big concern...

Indeed. I can't see many people dispatching/commuting long distance on a carbon framed special. :)

zunkus
09-01-09, 05:33 PM
With what is mentioned here and from more research through the web it seems that CF for the road does not make much sense for three main reasons.
1. It's almost impossible to repair.
2. Has a much more limited lifespan when compared with traditional alternatives.
3. Very expensive.

The pro's for CF are stiffness and light weight. Stiffness is needed to a certain degree as as explained by a fellow racer, you do need some flex when banked over in bumpy turns. Second pro seems to be light weight but by how much? How much would a bike frame be lighter than an aluminium one? Maybe we could look at wheels for comparison.

MattCollins
09-01-09, 05:42 PM
...But if you prang it, the chances are Maidstone Motoliner aren't going to be able to see it back to being OK...

The same is likely to apply to an aluminium or steel frame. Chances are that the loads required to cause a catastrophic failure in a carbon structure would have turned a metal structure into a mangled mess of scrap. Carbon is amazingly resilient, but unfortunately gets a bad rap from the layman because of its ultimate failure mode - ie the so called "shattering" instead of buckling and folding as is seen in metals. The technology in the resin systems has come a long way in the last 40 years.

Cheers

Daimo
09-01-09, 06:18 PM
Never made it into production for various reasons.

http://www.benelliforum.com/gallery/albums/lloydbenton/Pictures_2005_262.sized.jpg

yorkie_chris
09-01-09, 06:24 PM
The same is likely to apply to an aluminium or steel frame. Chances are that the loads required to cause a catastrophic failure in a carbon structure would have turned a metal structure into a mangled mess of scrap.

Depends how overbuilt it is. If you are talking about for the same weight then I'm not sure...

To get flex in a frame then the carbon will have to be working at a fair chunk of it's maximum working stress, how will this affect it? Does carbon fatigue like a metal or what? What is failure mode when it does go?

xXBADGERXx
09-01-09, 06:30 PM
I think Carbon wheels fair much better than a frame due to the nature of their build in all fairness . It`s the long beams of a frame that come into question in prangs . Some of the carbon fibre mountain bike frames don`t have a very long life and they are mainly XC frames rather than out and out downhill frames . And as somebody else stated a while back in this thread , they can be TOO stiff . I seem to remember Eddie Lawson having a whinge or was it John Kocinksi when they were on the Cagiva 500 back in the early 90`s .

northwind
09-01-09, 08:37 PM
Yeah, but that's mainly bad design, carbon's come a long way now- you can make a very directional weave that'll flex like whippy steel, and of course it's used a lot in fishing rods and bows. Early carbon fibre in automotive use always went for rigidity.

squirrel_hunter
09-01-09, 09:34 PM
Carbon'd probably have a limited lifespan

From what I understand its lifespan comes mainly from the glue used to bond it, the glue is sensitive over time to UV light. There are ways to mitigate this risk buy using specifically formulated resins or I would imagine hiding it from light - paint it.

1. It's almost impossible to repair.


It is possible to repair CF, the principles of Glass Fibre repair are transferable. However I think the application of the CF would relate a lot to this, I would imagine that a fairing could be quite easily repaired, a wheel not so much.

However this all comes from what I have read, I'm yet to work with CF or GRP.

zsv650
09-01-09, 09:35 PM
cf on the road probably only any good for a boast to your mates on the road isnt it.

MattCollins
10-01-09, 08:40 AM
Depends how overbuilt it is. If you are talking about for the same weight then I'm not sure...

To get flex in a frame then the carbon will have to be working at a fair chunk of it's maximum working stress, how will this affect it? Does carbon fatigue like a metal or what? What is failure mode when it does go?

I was thinking of similarly designed structures.
The requirement for flex is also based on the assumption that the earlier experiences/problems have not been resolved.
Fatigue... <big snip> ...Carbon is a mature technology.

Similar discussions took place when the first aluminium frames started appearing (showing my age) and we all know what an unmitigated disaster they have been... :p:p

Cheers

MattCollins
10-01-09, 08:52 AM
Squirrell_hunter,

There will be no repairing of damaged CF frames. For that matter, repairing an ally frame is a fools errand. Insure it, break it, replace it.

Glue? This is not some cheap wet layup or chopped glass structure that we are talking about. It is a critical structure. Any interruption to the continuity of the fibres or resin system and it becomes a throw away.

Cheers

northwind
10-01-09, 12:57 PM
Not true at all that, if you get a full break then sure, it's probably junk (though could be rebuilt over the break) but a crack will usually leave the fibres intact, and that can be repaired- just look to mountain bikes for real world proof, you can re-saturate the break and then simply "bandage" it, it's not even uncommon never mind impossible. Bike frames might be lighter but they have a much higher stress/mass ratio than a road or race motorbike frame.

yorkie_chris
10-01-09, 02:57 PM
Depends though, that will change the ratio in that area which won't do it any favours.

How pronounced is the difference between carbon and alloy in terms of strength/mass?

MattCollins
10-01-09, 03:25 PM
Not true at all that.... you can re-saturate the break and then simply "bandage" it, it's not even uncommon never mind impossible....

What! Are we even talking about the same stuff? You might get away with that on a MTB that rarely exceeds 35mph, but not on a 180mph MC. As I said, fools errand.

....

MattCollins
10-01-09, 04:15 PM
How pronounced is the difference between carbon and alloy in terms of strength/mass?

Roughly 1.5-2.5:1... lots of variables.

Cheers

northwind
10-01-09, 04:37 PM
What! Are we even talking about the same stuff? You might get away with that on a MTB that rarely exceeds 35mph, but not on a 180mph MC. As I said, fools errand.

....

What has top speed got to do with it :confused: Precisely nothing at all. As I said, a downhill mtb frame is more stressed than a road motorbike frame.

yorkie_chris
10-01-09, 04:39 PM
How do you know? They haven't built one yet, and to get as light as they can the thing will be as close to critical stress as possible.

Fall off at 35mph and it'll hurt... 180mph be a bit more serious though.

northwind
10-01-09, 04:51 PM
What I mean is, a mtb frame is more stressed than a motorbike frame regardless of material, because of the huge hits it has to take and the low volumes and small cross-sections, yet can still be repaired despite that higher stress. Carbon fishing rods are under gigantic flex stress compared to either, and can be repaired too. Motorbike frames really aren't under a huge amount of stress except when they're crashing.

A 35mph crash is less bad than a 180mph crash but a motorbike frame isn't really very stressed at 180mph, unless you hit something solid, at which point you've already crashed ;)

squirrel_hunter
10-01-09, 09:01 PM
Glue? This is not some cheap wet layup or chopped glass structure that we are talking about. It is a critical structure. Any interruption to the continuity of the fibres or resin system and it becomes a throw away.


I only know of wet layup and prepreg CF techniques, in what way would the manufacture process differ for this type of application?

Red Herring
10-01-09, 09:31 PM
I seem to remember reading somewhere that it was far more likely to find a carbon road frame than a race one. The reason given was that race frames are always being tweaked and modified and it was much harder to do this with carbon than ally, you basically had to build a completely new frame each time. On road bikes they get the prototype frame right and then they can mass produce loads the same that never need to be changed.

yorkie_chris
10-01-09, 09:33 PM
You'd need lots of metal inserts to make a carbon frame work, can't really see it being possible to put a bearing into carbon. That would mean not much weight penalty to use adjustable headstock or what have you.

Tim in Belgium
11-01-09, 04:51 PM
Some carbon fibre pic wh0ring, apologies in advance:

http://inlinethumb62.webshots.com/24125/2759365660084392296S600x600Q85.jpg (http://good-times.webshots.com/photo/2759365660084392296ppzRfO)

http://inlinethumb13.webshots.com/43084/2114037620084392296S600x600Q85.jpg (http://good-times.webshots.com/photo/2114037620084392296kjUBwV)

http://inlinethumb27.webshots.com/25626/2730683330084392296S600x600Q85.jpg (http://good-times.webshots.com/photo/2730683330084392296gsgRtZ)

http://inlinethumb33.webshots.com/23200/2957014920084392296S600x600Q85.jpg (http://good-times.webshots.com/photo/2957014920084392296pOzNvi)

:D

zsv650
11-01-09, 04:55 PM
looks like carbon wrap.

SoulKiss
11-01-09, 05:22 PM
carbon wrap.

Is that code using the 1st letter of the 1st word and the last 3 of the second?

:)

zsv650
11-01-09, 05:24 PM
Is that code using the 1st letter of the 1st word and the last 3 of the second?

:)
no that would be rude ;):D

Tim in Belgium
11-01-09, 05:25 PM
It's chinese to be fair ;)

punyXpress
11-01-09, 10:10 PM
Nice bike, Tim.
But when are you going to do something about the chicken strips? :confused:

Ceri JC
12-01-09, 10:02 AM
What has top speed got to do with it :confused: Precisely nothing at all. As I said, a downhill mtb frame is more stressed than a road motorbike frame.

As YC says, I think he's refering more to the consequences of your frame suddenly snapping at 180, rather than 35.

the_lone_wolf
12-01-09, 10:16 AM
At 45 degrees of lean, a 10mm bump requires 20mm of suspension travel to absorb it



14mm



;)

SoulKiss
12-01-09, 10:22 AM
14mm



;)

14.142135624mm actually

the_lone_wolf
12-01-09, 10:35 AM
14.142135624mm actually
the 0.14 would fall within the error given by the tyre deflection differing where the bike is upright or leant over. don't quote unnecessary decimal places boy:p

northwind
12-01-09, 07:49 PM
As YC says, I think he's refering more to the consequences of your frame suddenly snapping at 180, rather than 35.

Yep, but since you're frame's under barely more stress at 180mph than it is in the garage, not an issue. Unless you're road racing of course in which case... Well, you're mad, so you might get a carbon fibre frame anyway :mrgreen:

MattCollins
12-01-09, 09:35 PM
Yep, but since you're frame's under barely more stress at 180mph than it is in the garage, not an issue...

:confused: Gone for a couple of days and all of the laws of physics have flown the coop.

I won't argue with you... but I will ask that you please explain that statement.

...

northwind
12-01-09, 10:10 PM
What extra high stresses do you believe it's under? What will cause a sudden critical failure?

MattCollins
13-01-09, 01:34 PM
Answers a question with a question.... I guess that you don't have the faintest idea and compose your response to divert attention from that.

How about...
engine torque of a lump at full song? Something is restraining that engine and the first stop is the frame.
....vibration induced by road surfaces, aerodynamics, and all of those unequalised rotating masses?
....the sometimes conflicting gyroscopic effects of the two largest rotating masses - even travelling in an (almost) straight line in the real world?
...suspension loads or are you riding around on billiard tables?
...the asymmetrical load paths of the drive train which conspire to twist the frame?
...the aerodynamic loads which ultimately are passed back through the frame to the rear wheel?

I could go on...

Loads will be transmitted through the stiffest path. In a normal composite structure that would be through the fibres. With a compromised and repaired structure the bandage can easily become the stiffest local part, but without the continuity of fibre the "glue" line between the patch and part becomes a critical path.

........

zunkus
13-01-09, 01:56 PM
Easy guys! From a layman's point of view and I must admit I'm not an authority on the subject, you guys are comparing two frames which have some things in common and some other major differences in mostly weight and torque stresses.

The bicycle frame is majorly supporting the rider's weight and the torque force applied by said rider's pedaling. The road's uneven surface is introducing additional stresses to the bike's frame.

The motorcycle on the other hand has the same problems as the mountain bike but with additional weight and torque from an engine producing a bit more power than a cyclist. SO similar forces but much multiplied on a motorcycle.

My mind is telling me that maybe a material may be quite a good candidate for a lighter less stressed mountain bike but maybe cannot be directly compared with a motorcycle having much more weight and stresses.

Grinch
13-01-09, 02:02 PM
Just look at the geekyness of this thread and people have the gall to quote us computer tech's as geeks... wow.

zunkus
13-01-09, 02:15 PM
I notice that geeks marry the most beautiful girls pal!

MattCollins
13-01-09, 02:25 PM
Zunkus,

I have stayed away from the MTB/MC frame comparison. My only objection is to the whole notion that carbon frames would be repairable in the manner described.

Going back to your original post, I don't think that we will be seeing "shattered" frames if/when we see these things on the road. One just has to look at what F1 does to their monocoque chassis' should be a fair indication of the state of carbon construction - bits go flying everywhere but the chassis remains intact. Boeing and Airbus are both using carbon in more and more critical structures - these aircraft are repeatedly subjected to high loads (but well known loads) and will be expected to put in 1,000,000 service hours. Bits falling off aircraft have taken aircraft down so it would be unacceptable having carbon components failing in service.

Cheers

yorkie_chris
13-01-09, 02:28 PM
The bit I wonder about is interfacing with metal mechanical bits. How do they do that? Just set a bit of metal into it?

MattCollins
13-01-09, 02:31 PM
Just look at the geekyness of this thread and people have the gall to quote us computer tech's as geeks... wow.

Coding/compiling as I read the forum... got a gorgeous lady too. :)

Cheers

Ceri JC
13-01-09, 02:33 PM
Say, engine mounts. How would they go in? Would you put metal parts into the carbon that the engine would actually screw into.

MattCollins
13-01-09, 02:35 PM
The bit I wonder about is interfacing with metal mechanical bits. How do they do that? Just set a bit of metal into it?

That is what is done. There are a few different methods... The trick is to not crush the laminate when the bolt is tightened. We have all probably seen metal inserts moulded into various plastic parts - same deal.

Cheers

zunkus
13-01-09, 02:56 PM
Coding/compiling as I read the forum... got a gorgeous lady too. :)

Cheers

There you go Grinch :)

northwind
13-01-09, 06:17 PM
Answers a question with a question.... I guess that you don't have the faintest idea and compose your response to divert attention from that.

How about...
engine torque of a lump at full song? Something is restraining that engine and the first stop is the frame.
....vibration induced by road surfaces, aerodynamics, and all of those unequalised rotating masses?
....the sometimes conflicting gyroscopic effects of the two largest rotating masses - even travelling in an (almost) straight line in the real world?
...suspension loads or are you riding around on billiard tables?
...the asymmetrical load paths of the drive train which conspire to twist the frame?
...the aerodynamic loads which ultimately are passed back through the frame to the rear wheel?


All of which are trivial compared to the forces of braking or heavy bump absorption :rolleyes: I answered your question with a question because up til this point all you'd done is knock every post I'd made without actually discussing it. Now, you've tried to actually defend your argument and come up with exactly nothing. Well done. Bike frames are often under more stress than you describe, if there was going to be a failure point it would not occur at high cruising speed. But all of this is based on your belief that carbon fibre can't be repaired- you're still choosing to ignore the fact that it can be and regularily is. Fishing rods (under huge stress for their tiny cross-section) and yacht masts (under more constant and considerably higher strain than a motorbike frame, and suffering constant drastic loading and unloading) are two simple cases where the repairability of c/f has been completely proven in the real world, which you seem to be ignoring. And of course mountain bikes, as discussed in depth. By comparison a motorbike frame has an easy life.

MattCollins
13-01-09, 06:39 PM
All of which are trivial compared to the forces of braking or heavy bump absorption :rolleyes:

Duh! My response was in relation to this...

Yep, but since you're frame's under barely more stress at 180mph than it is in the garage, not an issue. Unless you're road racing of course in which case... Well, you're mad, so you might get a carbon fibre frame anyway :mrgreen:

Straight line was a fair assumption.

A failed fishing rod or mast is not going to put you down the road, even if one of them presents its own hazards.

As far as the rest goes... believe what you will.

....

northwind
13-01-09, 06:52 PM
No, but a failed mast might strand you in the middle of the sea, or break your spine if it falls on you. Or a failed fishing rod might, er, have your eye out. Hmm. Not going to convince anyone of the dangers of a snapping rod am I? :mrgreen:

It's a bit of a silly argument tbh, shall we stop wasting each other's time? We're not going to convince anyone but ourselves.

zunkus
14-01-09, 11:53 AM
And to honest I can't see what the argument is all about because you're mostly saying the same thing. One thing is uncertain, can CF frames be repaired cleanly? I think it depends on the type of CF because there seems to be varied types of this as well and not a standard one. The cloth can be of different fibre length for instance as in fibreglass. Secondly maybe because of aesthetics, in the case of expensive road bikes, the client would prefer to change rather then repair. If the CF is anything near a fibreglass repair I'm guessing that you don't just 'glue' the broken part together but also bandage the joint together with more CF which is not nice. Aluminum and metal however gives you the option to weld and then clean up the mess afterwards. Again I must stress that I've not experience in CF but have done my fair share in fibreglass so have somee idea of processes there. So I'm basing my input on fibreglass but am curious as to new processes involved with CF.