Active aero!

So, I found myself at loose ends and decided to have a little fun.

I've been reading a lot of Can-Am books and followed a McLaren MP4-12C around the track a few months ago - so I had to try this. Not legal in almost every race class, although it is legit in Targa Newfoundland Open class. Really, it's just fun to play with.

McLaren!
http://www.youtube.com/watch?v=qRrUgo_FyWQ&feature=player_embedded#t=34

The initial plan was to use a SPAL linear actuator with a cool three-position controller. I'd have a low drag setting (triggered by a momentary button on the steering wheel), normal (the default) and high drag (triggered by the brake lights). Unfortunately, the speed of the SPAL part was just too slow, 1/2" per second. I could speed that up with linkages, but it was less than ideal. I've since found that there's a different version of the same actuator that runs about four times faster, so I may investigate that in the future.

Warren V had been playing with headlight motors and thought they'd make good actuators for an active wing. They're strong, fast, repeatable and cheap. They also have internal logic that's easy to control. 12V on one wire makes them go up, 12V on another makes them go down. The motors spin at 50 rpm, and with the standard levers that means about 6.5" per second of stroke. You can change this by changing the length of the levers.

The goal here was to build a proof of concept without cutting up the car. I took an extra set of mounts and attached the motors to the sides in a convenient place, then triggered them with a SPDT relay attached to the brake lights. There's an override switch in the cockpit that turns off the active wing. The wing takes 0.6 seconds to change position, although it's effectively faster on retraction because of the way I have the various linkages clocked.

First test around the neighborhood. http://www.youtube.com/watch?v=7VHDfn_rHAk

First test at the track. Max velocity was about 123 mph here, the whole thing seems to be holding up nicely.
http://www.youtube.com/watch?v=gK5wDfDK2Lk

It's ridiculously fun watching the wing flip around back there. The car just feels solid and stable, as if the brakes are more powerful. They seem less prone to lockup as well, although it's possible that I'm not braking as hard and relying on the aero to scrub off speed instead.

Just thought you'd find this entertaining like I did.

Wow, I am speechless!

All right, you win the GRM internet award of the day, or possibly week, month, whatever.

Any plans to tuck the actuator away with some linkage? Seems like it would be sort of disturbing the airflow around the wing like that.

That is pretty cool.

very entertaining

Where is that "coolest thing I have seen all day" award?

Hmm I better start hoarding pop-up light motors, it's not like they're making any more of them

You should be able to get more braking overall now from aero drag alone, even assuming grip were unchanged, the aero drag adds to your braking without going through the tires (so the more drag/harder to lock up question is just two sides of the same coin)...touching the brakes just lightly enough to activate the wing will let you slow down while on the lateral edges of your traction circle, something to try next time you go into a corner too fast.

Actually here's an idea, what about a more F1-style setup? You have plenty of power to make up for the drag, you could set the normal & braking wing position for max downforce (and add more to the front with dive planes/canards to balance it), use the "DRS" on the straights and turn harder. You might want to wire it F1-style so that if you're entering a corner without braking, you can press the "DRS" button a second time to return the wing to the normal position.

Well, that'll be illegal in scca.........

My pants are quite messy after watching this.

I second the motion for GRM award of the week/month/year as stated above!!

*Adds new item to "wish list"

Yamaha, let's not even start thinking about what the SCCA would have to say about this car...

I'd still like to get the DRS/cornering/airbrake combo working. I need a couple of different linear actuators for that. Warren has suggested a short delay circuit on the return logic so the wing won't "flap" if I have to get back on the brakes again, but I'm not sure how important that is after the test last weekend. The way the headlight motors work is that they have to go through a full cycle every time, so if the wing is on the way back to resting position it has to go all the way before it will drop back down to braking.

The actuators are up high because it was the easiest place to put them - I didn't want to make any permanent changes to the car for this test. They're certainly not in an ideal place from an airflow perspective.

If I can get my Traqmate working, I'll see how much deceleration I get at 75 mph from the airbrake deployment alone. I have no doubt that the drag is slowing the car.

Just for fun, here's a low angle shot from this weekend, with the GoPro in danger of being sucked into the intake. Turn up the noise!
http://youtu.be/CbKBsQku9QY

What is the difference in uses between the low drag set up and the normal position?

The problem with using a wing as an air brake is that when you go from a downforce-producing to a purely air-braking state, you'll get a little boost of downforce and then it will suddenly cut out as the wing stalls and becomes an air brake...not a good thing to happen on corner entry when you might already be braking at the limit. This is why the MP4-12C's air brake is a dedicated control surface.

Isn't modern technology fun...
Pushrods and bellcranks will get you a lot of torque out of even small motors. If you get really silly, you could look into stepper motors, and get nearly infinite actuation based on whatever you want, say maybe brake pressure, steering angle, speed, throttle, lateral acceleration. you could even make it asymmetric, so yet get air brakes on the inside or outside of the car, depending on what you want.
Go even more nuts and start to tie it into active skid controls and traction controls. Tie it into the cooling system to control the inlet area or control the intake length on a variable intake system.
Of course the 'not legal in nearly every series' is the catch. Open class cars have so much room to improve. I expect to see something like this at the next UTCC or 2013$ challenge.

That's what people tell me, the problems I will have. Unfortunately, nobody told me or my car so the problems don't seem to manifest themselves.

Remember, when the wing goes to air brake position, I'm nailing the brakes. It's triggered by the brake lights. So the little boost of downforce is completely overwhelmed by the big weight transfer to the front wheels. It takes 0.6 seconds to go to airbrake position, and it happens only on brake application. If I'm on the limit on corner entry and I hit the brakes, it's going to get exciting regardless of what happens with the wing.

fritzsch, the low drag setup would be for straight line speed. Just like F1 DRS.

Another reason you don't need to be too concerned with the ultimate loss of downforce as you go to the brakes is that the wing is creating a lot of drag at the top of the car which has the effect of adding to the rear downforce by way of torque. It is likely the increase in drag is going to offset the downforce loss. The downforce on most wings in stall drops off significantly, but it still makes some, just not efficiently. That downforce level is typically pretty constant once you are in the stall region.

The worst case would be if you were right on the very edge of the stall in normal condition. The wing may remain in a slightly stalled state after the braking deployment. Most motor sports don't run the wings that close to stall, so it is not likely to be a problem.

Keith just won the internet. I'm speechless.

Awesome

Absolutely awesome!

In reply to Keith Tanner:

For generation 2, maybe look into the (big) servo and stepper motors that the large-scale R/C planes use.

I am just being a smartass Keith.... I was dq'd for having the hatch come open on my ti.......I did run .5 seconds quicker with it up though.....

You didn't happen to disable for a few laps for comparison? That would be some great data to have.

Hmmmm... very cute

the Tanner Tueey (apologies to Jim Hall and his 2E)

ok, here is something I my say to add into this. If you can tie this to speed, you can limit its use below, say 50. Then the times when it will work least it can stay in spot.

That's very, very cool.

Very.

Smart phones have accelerometers, right? So we need an app for that. Negative acceleration gives max flap. Lateral gives a little flap, for traction or controlling understeer. Acceleration equals no flap.