Quote:
Originally Posted by Maxim
I've thought about this too, but I don't think that the typical speed of a rotating wheel would provide any meaningful aero. If the wheels were shaped so severely as to create meaningful suction, they would also be creating a whole lot of resistance to rotation as well.
Plus, it would require rims to come in sets of "left" and "right." If you take the same rim and put it on the other side of the car....it's spinning in the opposite direction...so one side of the car would be sucking air UNDER the car while the other sucked it OUT. That would negate any aerodynamic benefits, and if the wheels were designed to create enough airflow to make a difference in brake cooling, it would also generate a distinct "pull" to one side at high speeds.
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The thing is I've seen on the internet "active brake cooling" devices that are just small ducts with tiny fans. A wheel is rather large, even if it's not shaped ideally for pushing air, it is one big fan. I think at 60mph your wheels are spinning around 1000rpm or so (this might be completely wrong btw, I haven't bothered to think about it), which is actually pretty good. A 120mm low speed case fan spinning at 1200rpm pushes a pretty good amount of air. If you use the whole rim as a fan (albeit a not so ideally shaped fan) you can likely provide more cooling than a typical duct.
The actual power it takes to do this is pretty small, on the order of 10s or hundreds of watts most likely. Think a cooling fan for your house (do people in America even use them? lol). The really fat ones are like 300W, but they spin rather fast and have crazy huge blades. Also remember that most rims aren't very aerodynamic anyways and have some sort of loss to aerodynamic drag via spinning anyways. We could go further, use a centrifugal type blower fan and a housing that threads through the hub, and use it to directly enhance airflow around the side of the car but that would be rather complicated and mostly pointless.
And you don't need left and right wheels, they all blow outward.