interesting break-vent thing idea

[CdocZ]

ok, i was thinking awhile back, when i was basically designing a pagani zonda design inspired muscle car engined dream car of mine, when i thought of this idea. but first, so i dont feel like an idiot if it turns out it doesnt work too well, is it good to keep carbon fiber brakes cold until they need to be used? and when they are needed, they obviously need to be warm (especially carbon fiber) answer the question, its a rather nice little idea.....if i think i know brakes, which i dont really know them too well

[KnifeEdge_2K1]

you cant make brakes outta carbon fibre

its carbon ceramic or carbon composite

[CdocZ]

ok, well, w/e they are, answer the question for those then

[Sweeney921]

what's the question? there's no question in that first post.

[CdocZ]

oh, well, brakes in general, more specifically the carbon w/e brakes, some serious car guy i know said they need to get really hot when they are in use. but......when they are not in use, is it best if they are cold? and if so, why.

[sutton4481]

Carbon ceramic and carbon composite brakes on racing cars have to be warm to work best, but can't get too hot, otherwise they lose efficieny. This is why you see F1 drivers braking hard on the warmup lap, to warm up the brakes and tires. You usually dont see these kinds of brakes on road cars though because in a road car you don't exactly get a warmup lap. :-)

[Egg Nog]

Composite brakes need to be hot in order to function. It wouldn't make a difference in speed - they work if you're going fast or slow, depending on temperature.

Thanks for bringing this up :) - I never really put any thought to brakes/cooling with this type of system.

[KnifeEdge_2K1]

like the engine, brakes work best when they're at they're operatng tempreature, with ceramic and carbon brakes this tempreature is relatively high, and if you brake too hard and there's insufficent cooling the brakes and pads can actually catch on fire

[DodgeNitroBIRM]

you cant make brakes outta carbon fibre

its carbon ceramic or carbon composite

Actually, according to "Brake Systems: OEM & Racing Brake Technology" by Mike Mavrigian and Larry Carley, you can.

"Carbon fiber rotors offer light weight, but they are limited in their use. Currently, the only applications I'm aware of is in Formula 1 in Europe and in Top Fuel and Funny Car drag race applications in the U.S. (on rear brakes only). The cost is very prohibitive, at close to $1000 per wheel for a rotor and pads. There are a few interesting and unique aspects to carbon fiber rotors worth noting. First of all, you must use carbon fiber brake pads in conjunction with carbon fiber brake rotors. Nothing else will work properly. Just as the task of any pad and rotor combination is to transfer pad material to the rotor, in an attempt to 'normalize' the frictional properties between the two materials by creating a pad material-to-pad material contact when the pads rub against the rotors, carbon fiber-against-carbon fiber is what makes this system work.
"Since carbon fiber is so darned hard, it's difficult to transfer a conventional pad material to a carbon fiber rotor. As a result, the use of a carbon fiber pad against a carbon fiber rotor will create the frictional properties needed to stop the car. However (and this is something that newcomers to carbon fiber may not realize initially), carbon fiber systems only work when hot. The characteristics are such that a cold rotor and pad combination may not be able to produce enough frictional coefficients, largely because they cool so darned fast. Braking performance can be very erratic, from front to rear and even wheel to wheel. Drastic temperature variations (temperature rises and drops quickly) can produce braking results that change every time the pedal is depressed. You can usually tell if a Formula 1 car is equipped with carbon fiber rotors by watching the wheel locations. Similar to the apperance of titanium rotors in use, when the brakes are applied and peak temperature is reached, the rotros can glow very quickly, almost like the flash of a strobe. Once the pedal is released, they again cool very quickly."

Brake Systems: OEM & Racing Brake Technology
Pg. 136, "Carbon Fiber Rotors"
By Mike Mavrigian & Larry Carley
Produced by HPBooks

[SPHFerrari]

interesting...

[CdocZ]

ok, so what i see from this, is that carbon fiber brakes need to be hot for them to be effective, but cold so they dont explode or anything. basically, my idea, works best with for example, a saleen s7, or any car with scoops that are near the front or right in front of the back wheels (lead air into or around the brakes). the actual idea, is to have a little system that when you apply the brake, it closes the vents that lead air into the brake area for however long you hold it down. this way, the brakes will be as nice and cold as possible until needed, and when they are, there will be no airflow to cool them down when they are needed, especially useful for carbon fiber brakes as they have, as was said earlier, a high most-effecient operating temp. hell, it could be built out of wood this system

[KnifeEdge_2K1]

... how would you go by constructing a carbon fibre rotor?

the weave would be so complicated, and due to it's desgin you cant utilize 100% of the surface

[Matra et Alpine]

ok, so what i see from this, is that carbon fiber brakes need to be hot for them to be effective, but cold so they dont explode or anything. basically, my idea, works best with for example, a saleen s7, or any car with scoops that are near the front or right in front of the back wheels (lead air into or around the brakes). the actual idea, is to have a little system that when you apply the brake, it closes the vents that lead air into the brake area for however long you hold it down. this way, the brakes will be as nice and cold as possible until needed, and when they are, there will be no airflow to cool them down when they are needed, especially useful for carbon fiber brakes as they have, as was said earlier, a high most-effecient operating temp. hell, it could be built out of wood this system
you don't want the brakes getting cold.
You need to keep them at minimum operating temp and NTO let them get above max operating temp regardless of the medium the rotor and pads are made of.
The idea of the vents works in the opposite way, keep the vent closed to keep the rotors 'warm' and OPEN them when breaking and then leave them open for a wee while after breaking to bring rotor down to 'minimum' temp.
BUT does the extra weight and complexity worth it ?
Also you ned to watch about cooling and heating things aggresively as it adds stresses to the component and can lead to failure.
With the reasonably wide operating range of CF and of competition pads it's easy to keep them in the bets operating range once you've got them up to temp. With comp pads in the Bagheera I used to brake early into a corner still on throttle JUST to add some heat before I went pushing them to slow it down. Others didnt' like me for it as my brake lights would come on at odd times as I 'worked' to keep the pads warm :) They reckoned I was doing it to put them off !!!

[CdocZ]

so....now the broked down version of what you just said?

[Alastor]

so....now the broked down version of what you just said?

The ideal brake cooling system will keep the brakes at the best (single) temperature all the time, regardless of whether or not the brakes are in use.


There is an optimal temperature at which braking force is maximized. It is undesirable to have the brakes below optimal temperature before braking begins because during initial braking maximum braking force will not be applied. Therefore, the theoretical minimum stopping distance is not going to be reached. The same is true if the temperature increases above optimal.

Also, from the driver’s perspective the brakes are not going to be performing the same from initial braking to end of braking. It may feel like a non-linear response to the driver which is hard to control.

A certain amount of variation is allowable and this depends on materials, application, etc. Ceramic rotors tend to operate at higher temperatures than do metallic alloys. Excessive increase in temperature not only reduces the effective coefficient of the material but also reduces wear resistance. In racing applications the idea is to get the maximum braking force from the braking system which may involve operating above the most reliable operating temperature.

[Matra et Alpine]

... how would you go by constructing a carbon fibre rotor?

the weave would be so complicated, and due to it's desgin you cant utilize 100% of the surface
It's not mat, it's dust VERY small particles of carbon in a ceramic base ( usually ). it can also be done as a carbon/ceramic coating and some comapnies are producing carbon MAT pads whiich they claim give better bite and wear resistance.

BUT if you keep the weight down you don't NEED big brakes and don't generate lots of heat and struggle to dissipiate it :) Chapman called it "designing in lightness" :)

[RacingManiac]

... how would you go by constructing a carbon fibre rotor?

the weave would be so complicated, and due to it's desgin you cant utilize 100% of the surface


Its not made of CFRP, which is what we usually referred to as "carbon fibre". CFRP stands for Carbon Fibre Reinforced Polymer. As in Carbon Fibre embedded in polymer matrix. On a brake application carbon fibre is used by embedded in a carbon matrix. Which is why in F1 they call them Carbon-Carbon brake. Each disc can take ages to make(quoted figure is 3 weeks per disc), as they have to be baked at some temperature for that long to get the desired property out of it...

[CdocZ]

matra? is there anything you DONT know about cars? ive never seen you not know something

[KELSA]

Carbon brakes are good for track use, not for road.

[Matra et Alpine]

matra? is there anything you DONT know about cars? ive never seen you not know something
pretty much I've tried everything in cars over my 30+ years in life, competition and road use ( and all the attendant SELF repair, upgrade and maintenance - I'm not rich :) )
I looked into CF discs for a kit track car for a mate and decided it was pointless as we'd never get the bloody things up to temperatire :)

PS: Don't tell Slicks or it will ruin our friendship but I've even played on the drag strip :) See attached :)