333pg333

[QUOTE=JackOlsen;11414121]That's an interesting idea. In the case of my home track, though, there is a 130-mph corner where I'd want the wing helping me and a 130-mph straight where I'd benefit from it generating less lift and drag.

QUOTE]


From my communications with a few well known Aero guys small changes can make big differences. Certainly 10o A.o.A. is a big difference on average. e.g. I've been advised to modify the front of my fender vents to a more acute angle.





Something else occurred to me re the budget level attempted Jack. Currently we are going to work on something with my car where we regulate boost based on G loading. This will all be done via the Motec system but I wonder if you couldn't figure out someway of having the simple resistance / piston which is also governed by a 'float' of sorts? Or even a simple G meter that triggers an open/close lock or activator. Dunno...just thinking out loud.

kurt M

I know of a car that was using active aero in CR many years ago and the car was notably faster than any other near its power to weight ratio. Large rear wing with large end plates and enough movement to go from near stall to almost no AOA. with straight line killing AOA cranked in under braking and the turns it was passing other cars at will.

flink

http://ucrtoday.ucr.edu/23119

JackOlsen

The programming on that one seems a little odd.

stownsen914

The OG Racing 911? Never saw it, but I heard it raced with a setup like that before PCA outlawed it.

JackOlsen

Well, the time wasting has begun.

JackOlsen

Moving the front on a rear pivot turned out to be unworkable with a pedal and cable control. So V2 is going to have motors doing the work, with the wing pivoting at a more sensible point, relative to the center of the downforce.

BHunt 72T

Kurt, I remember the car as well. BL owned it while DC did the driving. I still remember being down in turn 1 and watching that thing go from flat to nearly upright at about the 300 marker. So simple too if I remember; it was just a lever inside the car he would pull next to the shifter. Awesome contraption. I think they outlawed it after a couple of races.

mark kibort

if you are talking cal speedway, then yes, its nice to think about the top speed gains.
However, even at Willow springs. 130mph, that wing of yours is probably near 300lbs of downforce at 10 degrees, so the drag is probably in the 30lb range. 30lbs, at 100mph, or 4th gear, with a 3 or 4:1 gear ratio reduction, is only 5-10lbs of torque at the engine. you are not going to get that much top speed difference with your target speed only having 5-10lbs of torque (at the engine) advantage, and much less (its a squared factor) at the slower speeds.

I measured the actual force on the stock GT3 cup car wing at 120mph, and it was 275llbs at an angle of attack of near 10 degrees. at 120mph with this wing, around 3-5ft-lbs of torque loss with NO wing, so one has to think that if only changing the angle of attack to 0 , gives you 100lbs of downforce, but you still have drag because the wing is still in the air flow, so maybe 10lbs of drag, 2-3lbs of engine torque gained. I think there are other things you could work on to get this benefit, without any of the downside risk.

flink

yup. All my experiements with drag reduction have been a great disappointment.

How did you do this?

JackOlsen

I'm still skeptical. But now the control is wired into a button on the steering wheel. There's also an 'in motion' indicator light so when I release the button I know the relay is sending the wing back to the safer position. I've also got a red decal on the underside of the wing which is only visible in the rear-view when the wing is in the low-drag position.

333pg333

Might be the angle of the camera but it really looks odd how it drops backwards to me Jack? Looks like it's going into whatever is the reverse of a stall position where the front of the vane is higher than the rear? I've not seen a wing run at that attack before so I don't know what it would do but I'd be doing a bit more research before running at high speed in that config. What A.o.A. is the wing at in the starting position? Also, and it may be seemingly insignificant but the end plates moving about like that would have some effect too. I know it's just a budget experiment but I'd hate to see you rotate off the track due to a big change in loading.

bmwtye

Not sure whatever happened with the aeromotion development of the GT3rs wing, but this was the last thing I saw of it. Shame not more came out of it:

winders

I think this experiment is a waste of time because the speeds aren't high enough to make the difference significant. Even at venue like the Big Track at Willow Springs. Heck, one of the areas where you are carrying a lot of speed is a turn so you need the wing in it's high downforce position anyway.

The air flow coming on to the wing is not parallel to the ground. The shape of the 911 has the air coming onto the wing roughly parallel to the rear window angle. Well, probably a bit in between the ground angle and the rear window angle. In other words, the low drag setting would have the leading edge of the wing higher than the trailing edge relative to the ground. I don't see how the end plates moving with the wing would have any effect since their job is to keep the air from spilling off to the side of the wing. If anything, it is better that the end plates move with the wing.

JackOlsen

Yes. The incoming air moving over the back half of my car is at an angle of about 10°, which is less than the 17°-19° of the (old) fastback shape, but also a long way from parallel to the ground. I tested it with wool tufts suspended from wires.

So if I run a 0° angle of attack relative to the road surface, I'm actually running the wing at 10°. I'm planning on running a slightly more agressive AOA (than usual) with this set-up, because the overall drag trade-off should be reduced. But then, drag isn't the only factor in setting a wing. Fore-aft balance and how it changes the car's handling is more important. So I'll be ready to go back to the original angle if the car is pushing through the high-speed corners.

Odd as it might look, the wing is still generating downforce at an AOA of 0° or even into negative AOA numbers. Regarding turn 8 (a 130-mph sweeper), I expect to go through it with the wing in the low-drag (and low downforce) position, assuming all this nonsense works. I frequently run at Willow with no aero bolted on (just the ducktail), and I am still flat on the gas through 8 without the wing in place. With the wing in its rocked-back, low-drag position, it will still be pressing down on the car in addition to the amount the ducktail spoils.

Lift force, drag force, and aerodynamic moment all scale with the square of speed. And the power required to overcome drag scales with the cube of speed. So I think there's probably some value to looking at whether reducing drag will help on the two portions of Willow that are 100-133mph -- which is about half the track. That said, I'm still skeptical that it's going to make a significant difference on a car that's as much as an aero nightmare as my widebody early 911 with all of its home-made aero pieces and what-not.

Still, it's interesting to take a look at something like this. Because so few sanctioning groups permit active aero, it's one of the few aspects of racing a 911 that hasn't already been tested and worked out to death.