Car modification - will it be allowed on track?

[SinglemaltWSKY]

OK,

Looking to add to our ever evolving and strange project car. I want to experiment with active aero on the car (because it's fun, that's why).

We are fabricating all of the wing components ourselves, not worried there. However the actuation for the moving parts of the wing assembly would be handled be pressurized air. If the compressed air tank (small), is in the trunk and totally separated from the driver, would we have any issues with safety personelle not allowing this in a track event.

The modification would be for larger solo 1 stuff. CTMP, Centrillia airfield etc.

Any advice is appreciated.

Cheers,
Jonas

[Navigator]

Jonas are you comfortable running an aero device controlled by air that could change mid corner or at speeds in excess of 230 kph without warning? How do you plan on running them, manual activation or auto? I would seriously consider what you are trying to achieve and decide first through data logging and a "fixed position" trial at many heights if it makes a difference. Also I am not sure how much time you have spent on the big tracks with your current car but my feeling is any real benefit may not be realized due to driver inconstancy. Play safe.

Personally for autocross maybe.... for track I would not do it. Others may have a different view.

[SinglemaltWSKY]

Good points. As for the "what we are trying to achieve" question.....it's just for fun. The whole project is a "because we can" idea.

My father is an engineer and is working on the design. He's confident that it would not cause instability in the car and has actually crunched the numbers on airfoil shape/size as well a material strength and on how much additional braking force we could generate at various speeds.

The wing will be default fixed and only move when the system is armed. Actuation of the system would be handled by a G-load sensor and relays.
The wing would only have 2 positions: Normal locked, and full brake (the wing would tilt to near vertical)

It's a 10 inch by 54 inch wing with an S1223 section thickened to maybe 15%. We get over 300 pounds downforce at 200 kph with not too much drag and quite a bit of brake assist at speeds over about 100 kph. At lower speeds it would be less/not effective obviously.

With pneumatics we need two 40 mm bore by 100 mm stoke cylinders running at 45 psi, one or two directional solenoid valves to run them, an air tank, and a small electric pump. We have found a load sensor that is adjustable from 0.2 to 2G and will easily run a relay circuit for the air valves.

The air pistons are only about 2.2 inches square so they could live in the vertical wing struts if the struts are, say, 2.75 inches wide.

For a 10 inch deep by a 54 inch wide wing, using a high lift S1223 airfoil, the downforce at 100 kph is 77 pounds and the power to push it down the road is 2 horsepower. It takes about 12 hp to push the bare E36 down the road, as a point of reference, with only aero forces considered.

At 200 kph the values go up to 308 pounds downforce and 13 horsepower more to push it. It takes 105 hp to push the E36 bare through the air - aero only.

At 100 kph the wing up braking force is 40 pound. At 200 kph the wing up braking force is about 160 pounds, or the equivalent of 54 hp trying to push the car backwards to slow down.

Put more simply, at 200 kph flipping the wing up will increase total car aero braking forces by 50%.

[Navigator]

Wow, you guys really have put a lot of thought into it. I love the "outside the box" ideas but I will still say try it on slower tracks first. :-) Now as to if its allowed in Time Attack you will have to wait for SteveD or Scott to chime in.

[SinglemaltWSKY]

Yeah - our philosophy is "where's the fun in not trying?".

Worse case, we will have a home built fixed wing and only activate the moving parts when we're out for fun runs. The whole car is an experiment.

I have a brother-in-law who has his masters in aeronautical engineering, he's going to help us make sure it is a stable design at high speeds.