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#1
11-30-2004, 06:16 PM
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interesting break-vent thing idea
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
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We put them [elected officials] in office to represent our communities, to represent OUR "ideal vision" of how things should be, and to serve us, honorably, not as a leader, but as a servant! 
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#2
11-30-2004, 06:51 PM
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you cant make brakes outta carbon fibre
its carbon ceramic or carbon composite
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#3
11-30-2004, 06:53 PM
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ok, well, w/e they are, answer the question for those then
__________________
We put them [elected officials] in office to represent our communities, to represent OUR "ideal vision" of how things should be, and to serve us, honorably, not as a leader, but as a servant!
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#4
11-30-2004, 07:09 PM
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what's the question? there's no question in that first post.
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#5
11-30-2004, 07:38 PM
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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.
__________________
We put them [elected officials] in office to represent our communities, to represent OUR "ideal vision" of how things should be, and to serve us, honorably, not as a leader, but as a servant!
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#6
11-30-2004, 08:01 PM
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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. :-)
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"It's the only car I've ever driven that'll spin the wheels at 200 mph." -Mark Donohue, talking about the Penske 917/30 twin-turbo Porsche Can-Am car.
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#7
11-30-2004, 08:08 PM
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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.
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#8
11-30-2004, 08:19 PM
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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
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#9
11-30-2004, 10:33 PM
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Quote:
"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
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"You know what these trees and old people have in common? They're both going in the ground soon!" - Bam Margera "The day the New York Times defines what Country Music is will be the day I shave my legs with a butter knife." - John Rich, of the country band Big and Rich I'll be 15 on Feb. 18th, so buy me a drink! (Hint: Don't look at it as the decimal number. <smirks>)
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#10
12-01-2004, 02:06 PM
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interesting...
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[url]www.spenserheaps.smugmug.com[/url]
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#11
12-01-2004, 02:34 PM
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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
__________________
We put them [elected officials] in office to represent our communities, to represent OUR "ideal vision" of how things should be, and to serve us, honorably, not as a leader, but as a servant!
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#12
12-01-2004, 02:44 PM
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... 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
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#13
12-01-2004, 03:10 PM
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Quote:
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 !!!
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David Leslie 1953-2008
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#14
12-01-2004, 03:12 PM
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so....now the broked down version of what you just said?
__________________
We put them [elected officials] in office to represent our communities, to represent OUR "ideal vision" of how things should be, and to serve us, honorably, not as a leader, but as a servant!
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#15
12-01-2004, 03:37 PM
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Quote:
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.
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