Carbon Fibre wheels

[Nebhotep]

Searching didn't yeald any answers so I decided to start a thread...
So,
Riding a bicycle there is the percetion that lighter wheels feel faster.The fact that there is less rotational mass seems to help accelerate better.This got me thinking about F1.
My point is has anyone tried making such wheels and is there an advantage?

[scarbs]

Carbon fibre wheel are easily available for motorcycles, they seem durable although bikes don’t to clash their wheels each other or armco! the reduction in mass benefits acceleration and unsprung weight. I see no reason why carbon car wheels couldn’t be manufactured. They are of course banned in most forms of motorsport and motorcycling.

[RacingManiac]

They are however, getting incredibly popular in Formula SAE/Formula Student, where such rules don't usually apply...The weight saving is tremendous considering most these cars now are in the 350-450lb range without driver. A typical 3 piece machined+spunned commercially available alloy wheel weighs 8-12lb each(13" x 7") in on these cars(some with custom design may be lighter). The carbon version are 2-4lb. Layout also varies in that some uses carbon rim, machined alloy center, or some team uses fully carbon wheel...

An article here on the FSAE trend...

http://www.fstotal.com/teamwork/suspens ... ecent-hype

[Nebhotep]

I don't want to be contradictory here but they do make flexible carbon fibre wings so by combining whatever parameters in CF manufacturing they could make wheels that withstand both low and high frequency bumps, plus carbon fibre has an absorbing nature.They are probably banned because I can't find another reason why they're not made.

[wesley123]

I believe that they are actually used in formula 1, im very sure that mclaren uses Carbon rims.

[scarbs]

I believe that they are actually used in formula 1, im very sure that mclaren uses Carbon rims.

I can assure you no F1 team uses carbon rims, they are banned. The carbon you see might be the wheel fairings which are added to the wheel for aerodynamic reasons, not for structural reasons.

[Carlos]

They do make some carbon fiber rims for road cars. There's the Dymag wheel ($2500.00 ea?) with a spoked magnesium centre and the Japanese WEDS wheel weighing in at 2.76 kgs.

Dymag Wheel

WEDS Wheel

Durability may be an issue, or the price may be ...
They certainly look pretty and what's more important than cute

[Jersey Tom]

I know of at least one FSAE/FStudent team with very trick looking super light carbon wheels, where its a weight penalty. The thing doesn't hold air worth --- so they have to run a tube.

People make too big of a deal about rotational weight. Or at least, too much based on handwaving.

Run the numbers. Depending on the part, often the linear / translation energy element is much more significant than rotation.

[Steven]

Just to clear things up about CF wheels in F1, here's an excerpt of the current Formula One regulations:

12.3 Wheel material :
All wheels must be made from an homogeneous metallic material.

And for that matter, all wheels currently used in F1 are made of magnesium alloy.

[jddh1]

a couple of yrs back when i was in college, we looked at carbon rims for our SAE car, but decided it was cheaper and faster to manufacture Mg ones. So I got to work on making Mg alloy rims. We did not want to buy our rims and manufacturing the CF version would've taken away from other work with the car.
But that was the only reason. We could not find anything against having CF rims. Our calculations did not give us any idea that the loads would've been too much.

In cycling (another passion of mine) you must have CF rims if you want to have a half chance at winning anything at any level. The wheels' weight is a large % of the total bicycle weight, whereas in cars that % is much less. So it's not as integral as with bicycles to have CF rims.

[F1_eng]

Jersey Tom, I don't see any logic to your view on rotational weight.

The weight of the wheel is very important. They have to be accelerated in every possible axis, unlike most parts. They are also often the furthest signifacant mass from the centre of gravity, meaning they contribute hugely to the rotational interia of the car.

Masses of components and their relative positions is often overlooked when designing cars.
Spend the budget on lightening appropriate components. For example it's not unusual to see ballast held on with titanium fasteners. Another is a poor car which has an expensive carbon seat (more or less at the centre of gravity) that is then ballasted.Since the seat is on the centre of gravity, its not contributing to the inertia so you could have a heavier seat and use less ballast, much cheaper for people on a budget.

This type of debate is interesting as its not always desirable to have the lowest rotational inertia, the DI is also an important consideration.

[Jersey Tom]

Jersey Tom, I don't see any logic to your view on rotational weight.

The weight of the wheel is very important. They have to be accelerated in every possible axis, unlike most parts. They are also often the furthest signifacant mass from the centre of gravity, meaning they contribute hugely to the rotational interia of the car.

Masses of components and their relative positions is often overlooked when designing cars.
Spend the budget on lightening appropriate components. For example it's not unusual to see ballast held on with titanium fasteners. Another is a poor car which has an expensive carbon seat (more or less at the centre of gravity) that is then ballasted.Since the seat is on the centre of gravity, its not contributing to the inertia so you could have a heavier seat and use less ballast, much cheaper for people on a budget.

This type of debate is interesting as its not always desirable to have the lowest rotational inertia, the DI is also an important consideration.

I realize the significance of weight savings. I'm saying that in terms of the total power you're "freeing up" by going to a less dense material with similar geometry.. the component of that total power savings that's purely linear can be much larger than the rotational power.

Certainly the case with hubs, from what I remember. I'd have to check with wheels again.

Likewise the fascination with unsprung mass. Yea it's generally accepted that it's important. Proof is nice though. I doubt you'd find anyone anywhere in any organization that could truly quantify the effect of load variation of varying amplitudes and frequencies on grip.. at real racing speeds. As far as I'm aware there's no test machine that can quite do that yet on a rolling tire at appropriate loads and speeds.

[riff_raff]

While composites have many benefits over metals, with regards to stiffness, weight, etc. Metals have one significant advantage over composites with regards to one physical characteristic: elongation.

Elongation is the characteristic that determines how much a material will "stretch" before fracturing. Metals like magnesium have excellent elongation rates, carbon composites don't. So for a part, like a wheel, that regularly gets impacted against curbs, you want a wheel material that will bend instead of breaking. A material like magnesium, and not like carbon fiber composite.

Regards,
Terry

[F1_eng]

Tom, I am strugling to see what your point is.
What do you mean by "power that you're freeing up"?

The fact that the wheels take a force to accelerate it rotationally means that the available force to accelerate the vehicle is reduced.
The F1 team that I work for certainly can quantify the effect of varying vertical force on available latteral force, any team that has the resources to analyse this and doesn't would be foolish. Afraid I can't give anymore detail.

riff_raff, elongation is an important material property but not one that is hugely influencial in single seater racing wheel design. You need to consider the damping characterstics of the tyres and how much of the loading is transfered in to the rim. If carbon rims were legal, for sure they would get used in Formula 1.

[Jersey Tom]

Tom, I am strugling to see what your point is.
What do you mean by "power that you're freeing up"?

Takes a certain amount of power to accelerate a given amount of inertia at a given rate. Lower the inertia, and you're reducing that power requirement. It's like getting extra free engine power to make the car accelerate faster.

My point is, for a lot of parts (ex: hub), the linear inertia can be much more significant than rotational.

Yes, you take any small gain you can.. but people make a big deal out of the fact it's rotating when on a relative order of magnitude comparison, it's not as big as some would indicate.

The F1 team that I work for certainly can quantify the effect of varying vertical force on available latteral force, any team that has the resources to analyse this and doesn't would be foolish. Afraid I can't give anymore detail.

I just highly doubt this. A 7-post rig will not really give you the answer. They're great tools for sure, and a team probably won't be competitive without one, but it's only half the puzzle. (Plus the tires don't rotate and may or may not be at the right temperature)

I'm talking about measuring dynamic tire forces and quantifying relaxation lengths in multiple directions. I don't know of a test machine on earth that can quite pull this off at real race speeds and loads.