10 replies to this topic

[Wedge]

Does anyone know how effective of a diffuser is at low speeds? I'm talking from 0 - 120 km/h. Thanks

[desmo]

Aero effects are generally a square of velocity, so diffusers and other aero devices will have relatively little effect at those speeds. Translation: Aero kits for road cars driven sanely are 90%+ for looks.

[RJL]

Originally posted by desmo
Aero kits for road cars driven sanely are 90%+ for looks.

Yep, and they do look rediculous don't they? I've often wondered why the manufacturers don't take the money wasted on those silly "wings" (which just get in the way when you're looking in the rear view mirror) and spend it INSIDE the car where it could actually benefit the driver?

[Wedge]

Your close Desmo, I was more thinking of seeing if I could somehow strap one on to a Formula SAE car.

[desmo]

Well I suppose it couldn't hurt if you didn't have to compromise the other aspects of the design. From what I've seen of SAE cars, big-ass wings would probably give a better result at those speeds.

[imaginesix]

Any rule against a fan-car in FSAE? Then the downforce is dependant on the effectiveness of the fan (meaning it can be significant at low speeds). It may also allow you to reduce frontal area (by dispensing with the cooling ducts) with some careful forethought.
Speaking of FSAE rules, where can someone get a look at the rulebook? Anything available on the 'net?

[random]

There was a fairly good look at "the" F1 fan car during the recent Speedvision coverage of the Goodwood hill climb.

Apparantly Bernie still owns the car and paid to have it fully restored to factory fresh spec. The twin rear fans were actually used to cool the motor, not just to suck the car to the ground (which they also did very well).

[Froilan_G]

No that was the story they told the FISA and the rest of the teams. For sure the car was equipped with the fans to produce more downforce. Unfortunately, the rest of the teams and the ruling body didn't buy the cooling story.

[Ben]

Sucker cars are banned in FSAE/Student. I believe Cornell (Who won this year's American event) built one about 8 years ago and the rules panel banned them for subsequent competitions.

The rules are available in pdf format on sae.org,

http://www.sae.org/s...s/fsaerules.pdf

As far as diffusers go, I agree with desmo. The only aero devices that have ever noticably affected the performance of an SAE car were the barndoor wings Cal Poly Pomona used to come 3rd overall in the States and win Formula Student outright in 2000.

Ben

[random]

Originally posted by Froilan_G
No that was the story they told the FISA and the rest of the teams. For sure the car was equipped with the fans to produce more downforce. Unfortunately, the rest of the teams and the ruling body didn't buy the cooling story.

I had always heard what you mentioned, that the fans were purely for downforce and the cooling angle was a sham. But the interview I saw with the head restoration tech said otherwise.

Apparantly the engine would have shortly expired if not for that fan. The designers weren't dumb and knew the scruteneers would quickly have scuttled the car if the fan were purely an aero device. That it also sucked the car to the ground is a given, but it did serve a legitimate purpose as well.

In any case, the rules were a LOT more wide open back then which spurred some true innovation. Today of course the teams spend a lot more money, but on changes so minute that only the technically savy even notice.

[imaginesix]

Originally posted by Ben
The rules are available in pdf format on sae.org,

http://www.sae.org/s...s/fsaerules.pdf
[/B]

Thx again Ben