h a l f b a k e r yI think, therefore I am thinking.
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On most cars, the wheels are designed to circulate air over the brakes to ensure that they are cooled down between stops. This is necessary to avoid having the brakes overheat during start-and-stop driving conditions.
Unfortunately, circulating air over the brakes takes energy, and this energy
imposes a certain cost in fuel economy.
I would suggest as an alternative including a thermal sensor in the brakes and designing the wheel or hubcap so that air only circulated over them when they were hot enough to benefit from it. In stop-and-go driving conditions, the vents would be open and there would thus be no fuel economy benefit. In highway driving, though, where the brakes may go completely unused for an hour on end, there would be no need for the air circulation and the vents would close, reducing drag.
BTW, a similar concept might be workable for the radiator, but since many cars already have thermally-controlled fans I don't know that adding thermally-controlled vents would improve anything there.
Not a cooler hubcap
http://www.entrepre...96486----1-,00.html
College sports fans will buy just about anything with their favorite team's logo on it. [thumbwax, Oct 18 2002, last modified Oct 21 2004]
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sounds extremely cheap to design, build and fit. where do I get some? |
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I cannot remember the last time I saw a car with hubcaps. |
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Do you golf? 95% of the OEM hubcaps made for golf carts whirldwide are made by Cycle Country. Hubcaps are less hubcap *looking* than they used to be - no more of that squished aluminum soccerball look... |
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Any idea as to whether or not the additional equipment would offset the fuel savings? |
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[phoenix]: If I knew that would I be posting on halfbakery? >:*3 |
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I understand the concept here but I'm not sure how big of a problem this really is. None of my cars' wheels appear to me to have any mechanism for forcibly circulating air across the brakes. For my edification, got any links that might illustrate this functionality on an ordinary car? |
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No, I don't golf [TW], and am wondering how useful these brake coolers would be on a golf cart. They don't see freeway speeds much. |
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Define "ordinary," [half]. |
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Not explicitly designed for high performance and therefore in need of high braking capacity. Just a run-of-the-mill production car. |
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I know of several cars that were built with ducting to cool brakes. And I have seen hubcaps that appear that they might draw air across the wheels, but none of my cars (all with alloy wheels either aftermarket or stock) have this feature. |
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I was just curious to see how pervasive this functionality really is. (My cars aren't exactly ordinary run-of-the-mill or state of the art.) |
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Since we're on the subject, I've often wondered if it wouldn't be possible to create a(n automobile) rim whose structural members formed a series of air foils. Then you'd have four little fans pulling or pushing air over each brake. Probably not enough rotational velocity to make much difference though. |
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My 91 Cavalier Z-24 had aluminum wheels that directed air across the front rotors. These were stock equipment. |
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You've identified the situation in which brakes overheat. Why then does a car require a sensor for heat, when a sensor for stop and go driving would be more practical? |
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Perhaps some bi-metal flaps would work as a totally passive system. But they would have to be mounted on the brake disk to sense the heat.
There may also be funny noises as the flaps open and close. Perhaps they need snap-action like the thermostate switches in some old refrigerators. |
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Why does it need a sensor at all? The flaps can be spring loaded into the normally-open position and cleverly designed to close under the action of centripetal acceleration and/or airflow at speed. |
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BTW, in the UK at least, hubcaps are now called wheeltrims. |
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This is like the vents on the new Lamborghini Murciélago. There are two variable geometry intakes on the sides of the car that are wide open at high RPM, low speed to give lots of air to the engine, but closed at hugh speed for better streamlining. Like thise little pop-up spoilers you see when the %&#$ers with Porsche 911s pass you on the highway. |
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I'd laugh when, after coasting down a long hill trailing your brakes, your hubcaps balloon like parachutes and make a bid for freedom. |
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good idea but not nesesary for every day cars |
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