I have a hobby interest in carbon fiber use in bicycle frames. The aims are similar: lightest weight possible, optimal strength in certain planes.

The lightest bike frames do not place the cosmetic CF weave on top of the structural CF -they either use nothing or paint. The top weave layer is cosmetic and adds no strength, it's just there for looks.
The CF that provides strength is uni-directional and just looks matt black.

So why does F1 use top weaves in all CF parts? Wouldn't they want the best strength/weight ratio?

They don't... Many parts such as chassis are painted. Others are moulded to aero shapes so the outer surface is against the mould surface and you do see the weave, but it's not cosmetic and a closeup view would show lots of kinks and ripples and overlaps in the layup. True cosmetic layups don't exhibit these.

Regards, Ian

Bicycles, due to the UCI's 6.8 kg minimum weight rule for road racers, needn't worry too much about weight in design and construction. Even the bikes riders use in the TdF are now pretty distant from composite state of the art, as there's no real incentive to improve them. For many years racing bicycles were truly close to state of the art in materials and design but those days appear to be over and as the state of composite tech continues to advance they will become progressively further from it so I wouldn't be looking too seriously at current bicycle practice there.

As F1 cars, unlike bicycles, can usefully profit from ballasting, they will benefit from measures to reduce mass even in the presence of minimum weight regulations.

Probably the vacuum process minimizes plastic reinforcement exposing more fiber.

Most bike parts are pure compression-tension parts...and don't suffer a lot of torsional forces.

Race cars suffer a bit more of torsion.

I'd suspect that the 0-90 weaves on the outer skin of the cars are structural no purely cosmetic.

This is way off for bicycle design. Many teams use CF part weight savings to run other heavier parts in the drive train. Many bike teams run ballast for the 6.9kg rule. New safety tested regs have made other critical parts heavier.
Frames are down to 800g. Cranks have torsional stress.

Bike wheels made of CF will always be faster if lighter, due to rotational inertia.

From another thread:



That weave is visible on all parts -it has no strength properties and is only cosmetic.

My best guess is that while bike designers watch grams, F1 cars are already quite light with a CF part. The are likely just buying pre-impreg CF with the weave top coat. It looks cool.

Ballast on a racing bicycle? Where is it mounted and what are they trying to achieve by mounting it there?

Can you show us a pic of this uni-directional CF? I can't say I've ever noticed anything other than the style of pre-preg above on racing cars.

The stuff we use looks like black horsehair. it's called graphite tow. Nasty stuff to handle.


Why this thread is illustrated with a device for heating wheels I'll never know, perhaps they needed to save weight on the workshop equipment, but that doesn't seem likely. (Yes, i am taking the mickey).

I disagree that bike frames don't see torsion, when you stand on one pedal and pull up on the opposite handlebar that is a fair old torsion for a planar structure, in fact I have seen competitive bike racers chuck frames when they fail the knee test, stand by the bike, hold the handlebar and push against the saddle stem with your knee.

That is not a picture of a part from a car, that's a wheel warmer so find another example. There's no critical need to save weight on that piece with the duckbill.

Ahhh, but consider this angle.

You have to carry that stuff around with you in trucks or ship it very expensively by air. I wonder if there's a point where making everything out of CF is cheaper than shipping a 'normal weight' version around the world 17 times a year.

Maybe it's something Bernie demands since they pay for most of the overseas transport costs

2010: The year of the CF hospitality soup bowl

Ever thought that it is 2 layers of uni-directional woven at 90 deg (or some other angle) to each other.
What makes you think pre-preg has a cosmetic 'top coat' ?

I know F1 designers and team principals would not be thinking about the cosmetics of carbon components

Now you are very far from the truth. Racecars are generally made using several types of carbon fibre in different places, such as ultra high modulus and super high tensile fibres but also different weave types (mainly woven and unidirectional) and weights. The carbon fibre is pre-cut and pre-impregnated with resin and cured in an autoclave for maximum stiffness and strength.

I would think that stiffness is more of an design issue than strength for most components and many of them also have complex shapes. Due to the latter woven fibres are often required.

http://www.youtube.com/watch?v=dA5IoUFYIHk...player_embedded
http://www.youtube.com/watch?v=tCvqQruNMaU...feature=related



I think it's also much due to availibility. The racing teams have the equipment needed to made carbon fibre parts so using a cheaper grade of carbon fibre thay can be made for a quite low cost (low cost for a custom made, low volume part that is), and still be lightweight which surely is an advantage when they need to be transported around the world to different races.

Sorry, but I feel you're a bit misguided if you think that the outer layer of carbon in that photo represents a cosmetic only layer that offers no structural properties!

There have been a number of promotional TV pseudo-documentaries in recent years (Discovery with Toyota and Eurosport with Williams) that show the layup process in detail. I recall a Toyota rear wing endplate in particular, all the parts were cut out of woven sheet, with the weave alternated in 45degree layers. The guy from the team was very proud of his computerised cutter and showed off the pattern very clearly.

Teams do not layup UD carbon in sheets, that would be a right pain to consolidate properly. UD comes in strips / tows / 'bootlaces' as Greg states. Most F1 components are not loaded in ways that require a lot of UD. I suspect a bicycle frame is a lot different to most F1 components, and therefore the layup is a lot different too, assuming the designer knows what he's doing.

Regards, Ian

Aerodynamics are much more important on bike stuff, which is why they nearly all race deep section wheels. Rotational inertia is tiny because omega is low and changes in omega are even lower. There will be those who run shallow section wheels when there are big climbs, but I believe that's more an issue of tradition rather than mathematics.

As far as I know, it's to come in 'just at' weight. Most often it's stuck in the seat tube.

Yes the TDF at least has rules about the traditional 'look' of the bikes.

Surely the common visible bit is the side against the mould and thus the first layer on and the epoxy the "gel" coat. For most applications the other side is rough and porous. In the small amount of CF work I have done, it is hard to stop the outer layup away from the mould being porous without lots of extra, therefore heavy, epoxy. Btw, I don't have an autoclave. Used to, but it went to the scrap about 40 years ago. Oh for 20/20 foresight.

FWIW...

This new product is being made in my city, it's called PPS and it's 80% everything that CF is at 1/3 the price ...
http://www.chinapps.com/en/index.asp

In about 1 week I will be introduced to a fibre that comes from an African cactus that is apparently as good as your typical fibreglass fibre but at 1/6 the price.

The stiffness (modulus) of the PPS stuff is only about 1/5 of aluminium. I've used a similar product, Ultem 60, as a replacement for aluminumium when strength is more important than stiffness. The flowability of the resin drops markedly as you increase the glass content, and surface finish suffers as well. On the other hand for complex high volume parts it is much cheaper than machining them.

Looking at it for multibladed (30 per rotor) wind turbine blades.

I want to extrude them from aluminium but not my choice.

I love extruded aluminium. $2000 for a custom die and away you go.

..the use of CF on sundry pit equipment comes from the store of time-expired pre-preg left over at the teams, and is a way of making light items, as mentioned above, for all air transport races. One could say they shouldnt time-expire if efficient sourcing and procurement, but no team clag-shop chappie is going to get caught without material for that surprise item the D.O. comes up with...

Unidirectional CF is usualy wraped in weave as an outer covering as less prone to damage...

Unidirectional CF...

I agree with you Greg. I hold a USFC Category 3 racing license in the US and I spend as much as 12,000 miles a year on my bike. I will add that CF handle bars and stems flex a lot during sprints - post race videos show an amazing amount of movement. Only a few years ago CF fixed as many problems as it created when used in bicycle frames...really dead feel was one of the most common comments after a test ride. Colnago for some reason or other produced the C50 with really good feel. My personal worry about CF in a bike frame is its character at its yield point...I've seen some frames just tear apart - obviously not in normal operation.

Uni-directional is only used in a small proportion of carbon products, because it only provides strength in one direction. With structural components you want strength in multiple directions, stiffness, and balanced stresses throughout.