Double O 86

Doesn't that already happen when you hit the brakes? The front of the car tips forward, and the front splitter is now slightly angled down.

I'm not mocking; I genuinely want to learn about aerodynamics.

Dlaitini

When braking, you are already transferring a lot of weight to the front wheels.

The brakes and the rubber can only do so much. You only want more angle of attack on the rear wing, to put more pressure on the rear wheels so the rear brakes can do more to help you decelerate faster. Not the fronts


If you did suddenly get more down force on the front wheels, now you are aerodynamically unstable and the rear will become the front and then you will be going for a ride anyway.. backwards through the grass

ThePass

iTrader: (3)

Yeah think motorcycles - depending too much on the front brake only hurts stopping distance. Applying more rear brake to the mix keeps the bike more level with less dive and stops you faster.

Your front tires are already doing everything they can, I expect your benefit is going to be like Dlaitini said - get more pressure on the rears to reduce the forward pitch under braking, you can move the bias a little rearward as a result, and get better stopping distances.

-Ryan

Keith@FM

iTrader: (1)

With the DRS setup, you have the option of running more wing angle. This will give you faster speeds through the corners (other than 8, apparently) without the associated drag penalty on the straights. It'll be interesting to see how this actually works in reality.

Most of the active wings in the Can-Am days were DRS instead of air brakes, whereas we tend to see them used as air brakes on hypercars like the Veyron and McLaren street cars.

Mr. Wob

iTrader: (2)

Keith/Others:

What would this do in a spoiler setup? Something like the Blackbird Lexan spoiler. Set at a medium angle and then activated to go near 90 degree lets say. I don't grasp the intricacies of aero when it comes to the anticipated differences between a wing and spoiler with an active setup.

ecc3189

It would accomplish the same thing in creating a lot of drag to slow the car down. I plan on doing this down the road sometime with a wiper motor mounted in the trunk connected to mechanical linkage out of the back and up to the spoiler.

-Evan

linkless

I should have a wing soon and will probably play with this quite a bit. I'm thinking that using a gyro/accelerometer in the control circuit to optimize the traction. Under braking I'd think you want large movements while in corner loads you will want more subtle loading to keep the car balanced. The gyro portion could detect if the car is starting to rotate abruptly and throw more rear traction in.

humming

iTrader: (2)

Just finished reading the whole thread. Neat stuff! I designed an active system for a formula mazda car, but we never got to test it due to a few erm... complications. You can actually get a really nice controller developed using just acceleration. As the car sees braking or turning the wing adds in angle, as those go away, so does the angle. The faster your actuators, the more smoothly you can match what you are doing with the steering and brakes, and the more natural and smooth it will feel. In the controller I developed speed mostly served as a sort of filter. Gyro is an interesting idea, but it's hard to implement without steering angle as well. I wanted to make some sort of easy release so that if the car got backwards the front brackets on the wing would pop off and let the wing flutter. Might damage the wing, but it would help prevent your rear from lifting. GPS would be awesome, but I've always been skeptical that the refresh rates might be too slow for it to be realistic. It might be a thing where you record a static lap, or with a generic tune, and record the GPS, and then go edit it in the pits to say "I want more AOA here, less here, ALL of it here" etc. The real problem is we are only talking about inputs, not feedback. Throw as many inputs as you want at the thing, you aren't getting the best you can get unless you are providing feedback. It's hugely important to safety as well. There are lots of potential ways to do it, but I never got far enough to experiment with those.

Jack Olsen

I'm still working on this. I'll be testing for a second time next week. But one thing I wanted to improve on was the warning light, which currently only lets me know when the Miata headlamp motors are moving the wing. I needed the indicator to remain on as a warning when the wing was in the low-drag position, so I added a magnetic non-contact switch like they use in home security systems. I'm basically spinning a magnet around, and when wing is in the low-drag position, the magnet trips a switch which I wired into the same warning light. So now the warning light is on both when the wing is moving, and also when it's at rest in the less safe (low drag) position.

rharris19

iTrader: (41)

While our ChumpCar setup isn't quite as elegant as the setups shown by Jack and Keith, it functions very well on track. It is wired up to a single motor in the middle under the trunk lid with a rod attaching it on a pivot close to 3/4 of the way toward the rear of the wing.

I was hesitant to have this setup as it would go into a 24 hour race completely untested. We wired it up with a single motor due to a combination of things and had no idea if only one motor could stand up to that abuse for 24 hours straight.

The motor was on actuated on the brake light signal, but had a switch in the dash that we could use to turn it off if it caused any issue. I will try to get a picture of the motor under the truck when I get a chance. The front wing mounts were some concern for us as they are aluminum and didn't know how they would hold up to something rotating on them for 24 hours, but only developed a marginal slack. They will be replaced with a better design.

We would have designed this with better components, but we have a budget constraint with this series that doesn't allow it.

I can honestly say that this worked better than I could have imagined. On the practice day, the weather was sunny and 72, and we could feel some decent straight line hard braking stability with slowing assistance. It never seemed to upset the car when resetting either, even when having to hit the brakes mid turn due to someone going off several times in front of us.


The vast majority of the race, 20 out of 24 hours, had a mix of showers and pouring rain. When we started the race we started it with the wing on knowing that it helped in the dry, so that must make it even better in the wet. It made the car so much more stable in the rain under braking than we expected. We could brake into a turn at about 90% of what we could in the dry with out a wing. We tried a couple laps of the car without the wing turned on, for the sake of experimenting, and went right back to having to early brake to keep the car for going through the turn. It was turned back on and never turned off.


I am happy to say the single motor made it through the race without issue and seems to be functioning just as it did before the race.

I will get a video of it working, but here are some pictures of the setup with a few next to a COT wing.

BTW, the "Pole Position" is not us being cocky. It is from a while back when we would try to theme our car and we painted it every race to resemble a NAMCO game.

Braineack

iTrader: (62)

I think I took a video of it too...


Active Wing by The Braineack, on Flickr

Failure

Just some quick napkin math with the CoT wing profile: the difference between 5* AoA (minimum drag) and 12* AoA (maximum down force) at 100 MPH is about 5 lbf. The difference between 12* AoA and 90* is about 210 lbf. DRS on this airfoil would reduce downforce with next to no drag reduction benefit.

Also according to my napkin math, it would take around 57 horsepower to overcome the additional drag of the wing at 90* AoA and 100 MPH. Now, how to calculate how much braking force is available from the tires? Work backward from stopping distances?

Jack Olsen

100 mph is about the slowest speed I'd be using it at. Does the news get any better at 130?

ThePass

iTrader: (3)

Keep in mind that in Jack's case at least, the wing is not a COT airfoil (The COT is a particularly low-drag design originally intended for aircraft, later adopted by NASCAR for a very high-speed automotive application) and many of the automotive-intended airfoil designs have higher lift/drag ratios.

-Ryan

Braineack

iTrader: (62)

here:

cyotani

iTrader: (8)

Why are you guys electing to go with a brake triggered "air brake" type set up rather than the typical straight line high speed drag reduction type set up?

Braineack

iTrader: (62)

how would you trigger it?

cyotani

iTrader: (8)

if it's for simplicity sake it makes sense to me. I'm just wondering if there's a performance reason for the decision.


you could use wheel speed and steering angle or accelerator data to find the straight away conditions that would benefit from the reduced drag. This would involve a micro controller tho and requires fine tuning of the actuating conditions but isn't terrible complicated.

ex: use a few if conditions:

if: speed > 50 and if steering angle < x degrees and if TPS = 100% then actuate DRS.

the TPS signal should bring the wing out of the DRS state as soon as you lift off throttle going into a braking zone. Once again, requires a fast actuator and fine tuning to not upset the balance of the car.

rharris19

iTrader: (41)

The first reason is that I didn't want to have the natural state of the wing in a high drag position in case something failed and it stayed there.

Second, for us to take advantage of the wing at a higher angle in the turns, we would need a much better front aero setup than what we have or the car would have pushed.

Most importantly, I wanted to make it a passive system that didn't require the driver to think about one more thing during his 2 hour stint.

I suspected that, at the speeds we were at, we wouldn't get a whole lot out of a low drag system anyway. The air brake was our main curiosity to test functionality and reliability. It met and exceeded our expectations on both. We are still looking at a low drag setup that can be integrated fairly easily into our current if for nothing other than to play around with for grins.

In the video above, it seems as thought there is an initial delay in response from the wing, but that is because I had to switch it on to show the guys it could be turned on and off.

rharris19

iTrader: (41)

Even if we wanted to set it up this way, we couldn't as the system to actively control it would cost enough to be prohibitive to ChumpCar's rules.