Carbon Fibre Wheels Anyone?

[Runako]

So, in the past there has been some debate about the usefulness, expense, fragility etc of any material other than steel as a substitute when making a wheel.

Well I follow the Koenigsegg feature on drive and I simply marvel at the technology these guys are using and stuff they produce. Its not a bike, but wheels are wheels and their latest Carbon Fibre wheels just seem incredible.

Here's the video on how they're made (kind of) and addressing some of the common arguments against the use of this material:

PGGiuaQwcd8&list=WLxiZ9PiXyAC1uboloj-ZL_w

Forget the argument of expense, I would LOVE to have some made for my bike! :D Discuss!!!

[Grant66]

CF has too many other issues to be considered useful for mass produced vehicles.

Having worked for the last few years on an aircraft programme which uses CF for structural components; I would be hesitant to want to have wheels made from it on my vehicle. The use of CF on an aircraft wing cost/benefit is negligible, on a vehicle its just a gimmick.

The layup process is critical, as is the temperature and pressure in the autoclave. Get these wrong, which change dependent on the resin or carbon used and you have minor defects which are very difficult to assess in terms of both fatigue and stress. These minor defects lead to cracking and splitting and are likely to affect the structural integrity before becoming visible. If your only making a handful of these wheels a year, then you can NDT each one to look for these manufacturing defects, this wouldn't be feasible for mass production.

Damage repairs also produce 'issues' and where a simple blending of metalic is possible, with CF it isn't if you break the fiber strands. Yes, you can fill with resin, but you can't be sure of the integrity of the repair without further expensive testing.

Weight saving can be achieved with super plastic forming or additive layer manufacture using metal, which although won't give you the CF look will remove the through life maintenance issues.

So to sum up, if you can afford a half mill for a car, you can afford the additional maintenance cost these wheels will cause. If you can't stick with metal.

[Runako]

I understand its not really a mass produced option, but surely if you watch the video it shows the potential is there to improve this process for all vehicles? The post was to use Koenigsegg's own example, so lets assume they got the measurements and autoclave process right. Therefore, he is essentially saying there is a structural and performance benefit.

40% weight savings on a critical unsprung part of the car which is most prone to centrifugal force seems like a pretty good benefit to me. This is not really directly comparable with a plane wing in that context.

I did also say, cost aside - as this is clearly the biggest obstacle to mass market. In fact, lets turn that around. If they could be manufactured for half the cost of cast wheels, who wouldn't choose the CF option? Break it, buy another!

Its a fair point to use super plastic forming as a counterargument but where is this in mass made motorcycles? I'm more intrigued by his arguments that they are actually more durable than forged alloy and significantly lighter & more balanced. Cost is always going to be the biggest factor as its not easy to make or replace. But 40% weight saving on a motorcycle is just such a good number :-D

[Spank86]

Forget the argument of expense,
Well once you forget that there really IS no argument.

[Runako]

Well once you forget that there really IS no argument.

How useful is this to the discussion? "CF cost a lot of money!" Yes. Should we stop building things because its costly? No. Should we keep trying to innovate? Yes. Can innovation bring the cost down? Yes. They've made 20 sets of wheels. Not much at all. But really, the intention is to look at the other criticisms of using CF to consider whether - cost aside - it can ever become the de-facto material for parts of vehicles like the wheel.

[Spank86]

How useful is this to the discussion? "CF cost a lot of money!" Yes. Should we stop building things because its costly? No. Should we keep trying to innovate? Yes. Can innovation bring the cost down? Yes. They've made 20 sets of wheels. Not much at all. But really, the intention is to look at the other criticisms of using CF to consider whether - cost aside - it can ever become the de-facto material for parts of vehicles like the wheel.

What I'm saying is that apart from weight there is no argument against a wheel which is lighter and stronger than current technology, unless of course youre feeling lazy and want to wait for one made out of carbon nanotubes (or graphene, seems like they wanna make everything out of graphene sometimes.


I'm more intrigued by his arguments that they are actually more durable than forged alloy ...
I'd say that's a statement that could be more or less true depending on how you want to measure durability.

[Runako]

I'd say that's a statement that could be more or less true depending on how you want to measure durability.

Did you watch the video all the way through? I am no engineer but he gives examples. Believe or not, up to you. But why is it any less believable than what Toyota tells you? (2.9 million vehicles recalled in 2014)

Well once you forget that there really IS no argument.

What I'm saying is that apart from weight there is no argument against a wheel which is lighter and stronger than current technology, unless of course youre feeling lazy and want to wait for one made out of carbon nanotubes (or graphene, seems like they wanna make everything out of graphene sometimes.

Ah, apologies.

[Spank86]

the intention is to look at the other criticisms of using CF to consider whether - cost aside - it can ever become the de-facto material for parts of vehicles like the wheel.

I suppose you could make the argument that CF is simply unsuitable for mass production but then the same has been said for a lot of things and time and money normally prove that theory false.

If it provides sufficient benefit then someone will work out a way to mass produce it.

Did you watch the video all the way through? I am no engineer but he gives examples. Believe or not, up to you. But why is it any less believable than what Toyota tells you? (2.9 million vehicles recalled in 2014)


I don't disagree with what he's saying, He's the expert but what he's saying is that that the wheels either fine, or in bits.

I've hit a curb hard enough to put an inch deep dent in a steel wheel and driven the car home (with rather a lot of vibration), Now he may argue that that's not an example of durability but the car was still drivable (at quite some speed). It's clearly a good material for a sports focused vehicle where weight is the main consideration (although interestingly that's truer at lower speeds [not necessarily the same as low speeds]), I'm not however sure that even if it became available for all vehicles it would be good for all of them. Certainly I don't think it would be so suitable for the offroad market and possibly not for your average suburban runabout.

It's all very well saying if it suffers complete collapse you just get another one (money no object) but wheel replacement "costs" more than simply cash.


All that said I'd definitely love to know what motorcycle racing teams think about the possibilities, a car is one thing but in terms of bike racing this sounds like ti has the potential to be as big (or bigger) than the move away from spoked wheels.

[Grant66]

so lets assume they got the measurements and autoclave process right. Therefore, he is essentially saying there is a structural and performance benefit.

CF is no stronger, no lighter and no more resistant to damage than metalic. The benefit in aircraft construction is its fatigue resistance, its not as susceptible to bending moments causing material instability.

40% weight savings on a critical unsprung part of the car which is most prone to centrifugal force seems like a pretty good benefit to me. This is not really directly comparable with a plane wing in that context.

Aside from there being no such thing as centrifugal force, the wheel will be subject to vibration and impact (small defects in the road surface) forces. CF needs to layered to absorb the impacted forces to minimise the likelihood of layer separation.

If they could be manufactured for half the cost of cast wheels, who wouldn't choose the CF option? Break it, buy another!

But your cast wheel will show visible cracking before breaking, without routine NDT testing the first indication of CF wheels failing will be as your sliding along the road on you brake discs.

Its a fair point to use super plastic forming as a counterargument but where is this in mass made motorcycles?

Addictive Layer Manufacturing when perfected will surpass CF, we're already making small parts for use on test aircraft,
This process can produce repeatable identical complex parts, can be automated and uses a material that doesn't have any of the negatives that CF has. It has the potential to be cheaper than making complex machined parts, but will never be used to make wheels for expensive cars as it won't look bling.

[Spank86]

Aside from there being no such thing as centrifugal force

http://imgs.xkcd.com/comics/centrifugal_force.png

CF is no stronger, no lighter and no more resistant to damage than metalic. The benefit in aircraft construction is its fatigue resistance, its not as susceptible to bending moments causing material instability.


Doesn't it have a better tensile strength (for it's wight) than Titanium?

[Matt-EUC]

http://imgs.xkcd.com/comics/centrifugal_force.png



Doesn't it have a better tensile strength (for it's wight) than Titanium?


I agree with everything you just posted.

Also, CF; lighter, stronger and sexier. (For its weight)

[PyroUK]

To answer the title.

YES.
just yes.

If I could afford it I'd have everything made of CF.

Plates, cutlery, bike, bed, doors, lid, desk. Bloody everything.

But only because it looks nice. There is almost no practical reason to have everything made of it other than that for me.

Maybe if I had a tonne of free time and a track car/bike it would be worth it for the technical benefits but as I don't I just want it for the shiny.

As such all arguments about cost/ fragility etc are wasted. It's like pretty much anything high end, it's shiny and I want it.

:-D

[Runako]

CF is no stronger, no lighter and no more resistant to damage than metalic. The benefit in aircraft construction is its fatigue resistance, its not as susceptible to bending moments causing material instability.

I thought it was supposed to be stronger by weight?

Aside from there being no such thing as centrifugal force, the wheel will be subject to vibration and impact (small defects in the road surface) forces. CF needs to layered to absorb the impacted forces to minimise the likelihood of layer separation.

Sorry I'm lost on the whole centrifugal force thing? You're going to have to educate me. What Mr Koenigsegg seems to be implying is that their curing process is very good, good enough to make their wheel a stronger option in comparison.

But your cast wheel will show visible cracking before breaking, without routine NDT testing the first indication of CF wheels failing will be as your sliding along the road on you brake discs.

If you say that I should check my wheels for cracks from time to time, I will admit that I hardly ever do unless I feel something is wrong with the bike.

Addictive Layer Manufacturing when perfected will surpass CF, we're already making small parts for use on test aircraft,
This process can produce repeatable identical complex parts, can be automated and uses a material that doesn't have any of the negatives that CF has. It has the potential to be cheaper than making complex machined parts, but will never be used to make wheels for expensive cars as it won't look bling.

Who cares about bling when you can get performance? With the power to weight ratio of a bike, any significant saving in unsprung weight means a more easily translatable performance increase. So why not? Anyway, this is the first I've heard of it, and I imagine it isn't common for the same reason CF is - because its expensive!

[Spank86]

Sorry I'm lost on the whole centrifugal force thing?
technically (using a static frame of reference) the force is centripetal, that's not a force pushing outwards (since that's the direction of motion anyway and objects in motion stay in motion requiring no force) but a force pushing inwards.

Take a bucket of water, if you spin it in a circle there is a forward force and then the bucket (and it's connection to you provides an inwards force preventing the water from flying off into the distance, there is no force directly away from the bucket.

If there was then you'd get very wet (of course from the point of view of the water it's a very different situation).

[Matt-EUC]

Spin a rope around with a ball on the end. The restriction is the string not a bucket. Same effect happens.

[PyroUK]

A ball is not a bucket.

I am now enlightened

[Teejayexc]

Take a bucket of water, if you spin it in a circle there is a forward force and then the bucket (and it's connection to you provides an inwards force preventing the water from flying off into the distance, there is no force directly away from the bucket.



Bollox, the bottom of the bucket is the only thing keeping the water from buggering off!

[Matt-EUC]

A ball is not a bucket.

I am now enlightened


Water is also, not a rope.

[Grant66]

At any moment in time the water in the bucket (and the bucket itself) wants to travel in a straight line (newton: unless acted on by an outside force). The outside force is applied by the rope pulling it away from the straight line.
Centrifugal is used as a way of suggesting the water is being forced towards outward, when in reality its centripetal pulling the container away from its intended course.
Why don't they teach this properly in schools?

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[Grant66]

Back to the topic :

CF isn't great at heat dissipation, not a problem for motorbikes, but cars would need better disks and pads. This only ads to the cost.

So if cost is not a limiting factor CF wheels are great. Back in the real world it is a factor and magnesium alloy(as used in formula 1 cars) is a lot more practical but mass production will always be aluminium due to cost.

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[yorkie_chris]

Dunno why the argument, it's inertia that's important in this case not centrifugal/petal force.

On a wheel you're having to use power to accelerate it's rotation as well as accelerate it forward down the road. Double whammy of weight reduction.
On some part of driveline or flywheel weight reduction here makes a massive difference in lower gears.

On a bike there's also the effect of a lighter wheel being more flickable. But good luck noticing that unless the front is loads lighter.

There are also benefits to it being unsprung weight reduction, this moves more and more road bumps from the tyre doing the work to the shock doing the work. Far more controlled, improvements in roadholding and tyre life.

[Runako]

CF isn't great at heat dissipation, not a problem for motorbikes, but cars would need better disks and pads. This only ads to the cost.

The video addresses exactly this point in explaining that they have a proprietary method to address this. The conclusion is that it is better at resisting extreme temperature which he says was a bigger challenge than surviving "curbing" or potholes. Also F1 teams are not necessarily at the cutting edge of all technology when it comes to cars. Porsche is a good example of that.

I've heard all the CF "no no" arguments. Point in this post is that he seemingly addresses some of these in his video - apart from costs. So is repeating the same argument about brittleness or heat susceptibility justified? (Genuine question here, not a criticism for stating it)

Could it be that their process is an evolution of CF manufacturing? Or is it all still wishful thinking?

[Spank86]

Spin a rope around with a ball on the end. The restriction is the string not a bucket. Same effect happens.

I tend to feel the water example is superior because the expectation would be the water falling out of the bucket.

Bollox, the bottom of the bucket is the only thing keeping the water from buggering off!

Exactly. Thats what i said.

The bottom of the bucket exerts an inwards force on the water.

Centrifugal force is an outwards force that would be pushing the water towards the bottom of the bucket, the waters already moving in that direction so no force is necessary.