Keith@FM

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Update: I was at the track last weekend with the wing running. And the Traqmate pooped out again. Argh. I got lap times out of it but there was a massive amount of noise in every other piece of info including speed. I think an internal accelerometer is badly messed up based on the G readings. Obviously this will need to be addressed.

However, I continued the seat of pants testing, as I can easily enable/disable the wing. In a 135-80 mph braking zone, the car felt much more stable with the active wing engaged. The current setup triggered by the brake lights does indeed show everyone that you just brushed the brakes, I think a pressure switch would be an improvement.

The second generation with the three position linear actuators has not yet happened. I've been doing some mental designing, but I've been too busy working on other things to tear into the wing.

Ryan_G

iTrader: (8)

This sounds awesome. I want a video of it in action once you get it all set up.

Jack Olsen

Thank you for documenting this. I'm working on something related -- a wing that can move into a lower-drag position for long straights. My first thought was to use a pedal and a set of cables to move the wing. As this video shows, it's easy to move the thing when it's sitting still. But I learned that at speed my 72" wing becomes much more difficult to move. My cables either flexed or stretched, but above 50 mph it became just about un-moveable.


Now, while I'm not convinced the pop-up headlight motors can generate more force than my foot, I can move the motors much closer to the wing and lose all of the transmission problems that have come with my cables.

But before I make the leap and buy the motors, I thought I'd ask for input here. Would one of these motors be enough to move a wing generating 350# or so of downforce? Would two? I only need to move it about an inch (up) in order to reduce the angle of attack and elminate some of my straight-line drag.

Thanks in advance for any advice from anyone. I'm glad I found this thread.

Keith@FM

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I'm a little star-struck here. Jack Olsen!

If you only have to move an inch or so, I think you'll have lots of mechanical leverage to flip that wing up. I've not measured the amount of torque in the motors, but the two on mine don't have any hesitation flipping up a wing with a 58" span and 11" chord at 130+ mph. They're pretty relentless. You're not trying to move all 350 lbs, you're just pivoting it. If you put your pivot near the center of pressure, it won't take as much power to change the angle of the wing. I didn't do that with mine, but it's part of the next generation design.

SchmoozerJoe

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Let's not feed the ego, ok?

triple88a

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You gotta change it so it gets more leverage however move the center point so the load gets loaded on the hinge. Move the Pivot point to the center of the wing and then move the leverage to either the front or back.

Jack Olsen

Thanks. I think I can work it so the rear mount gets (effectively) moved closer to the center, and then I'll make the front move up and down. If this actually helps my lap times, I can fabricate new uprights. But until I see the benefit, I'm going to cobble it together.

Does anyone know the weight of those Miata assemblies?

Keith@FM

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BTW, the location of the center of aerodynamic pressure is about 1/4 of the way back from the leading edge of the wing, not the center.

I'd guesstimate the weight of the motors at about 1.5-2 lbs. About the same as a wiper motor.

Jack Olsen

I picked up a pair of them today. Now I'm going to put some thought into how to bridge the wing and the uprights in a way that moves the rear mounting point forward.

I'm willing to bet I've got the only Porsche that's (now) sporting parts from both an early Miata and also a mid-90s Lincoln Continental.

Jack Olsen

A little bit of progress with my DRS version of Keith's idea.


I don't have the carbon fiber or Heim end pieces yet, but I cut a couple of pieces of L stock and attached a motorcycle battery. Here's some video:


There is an 18° net change in the angle of the rear wing when the motors move it.

carnut169

It's the downforce that allows you to get the most out of your brakes.. I think Jack's approach makes more sense and is closer to what we see in F1- reduced drag on straights, consistent DF otherwise.

I like the idea of a button (KISS) to reduce drag. Could maybe even use a sway bar adjuster (like linked below) and a push/ pull cable.
https://www.pegasusautoracing.com/pr...asp?RecID=2992


I'm thinking back to my FC days and feel I could stop faster with the massive downforce my wings produced than the aero drag they'd have in a stalled position, and as other have mentioned touching the brakes to settle the car before a high speed kink... I'd hate to muck around with downforce there.

Jack Olsen

Thanks. The thing that's important to me is that there's no way to accidentally leave my wing in the low-downforce position. So I think a momentary-on button is the best way to go. If something suddenly happens and a car swings out in front of me, I don't want to have to remember anything. As soon as my hand moves away from the button, the system is remembering to put the wing back, not me.

It's why I do want to borrow the one idea from Keith -- which is also using the brake lead to send the wing back to high-downforce. That way, even if I were to get confused and keep my finger on the button, the brake circuit will automatically move the wing back to its safest setting.

I've just got to figure out how to wire everything into a relay now.

Keith@FM

iTrader: (1)

(quote from Carnut should be here but won't show up. Drag vs downforce)


Well, we don't agree there. I'm basically throwing a parachute out the back, the same thing that McLaren does with the MP4 and that Mercedes does with the SLR. Of course, the amount of drag is related to the square of the speed of the car, this thing isn't going to be effective in autocross but it's very different at 135 mph.

It's not just drag, but stability. The center of pressure goes waaay back and stabilizes the car - this is quite noticeable on track with the wing engaged. It was this McLaren that prompted me to try this, I was following one around at the track. His wing behaves pretty much the same way mine does. I've been told the flickering brake lights are related to the stability control activating, BTW. The McLaren shows up at 33 seconds.


I agree that brushing the brakes will momentarily cut the downforce in the rear for 1.2 seconds as the wing cycles. A good solution to that (which I think was brought up here) is a pressure trigger in the brake lines, so a light brush - mostly for driver confidence - won't do much. Heavy braking, you'd want the air brake to deploy anyhow. In practice, the car does not seem to unsettle with with brushing the brakes before a sweeper, I was playing with this on turn 4 (the turn just before the long straight in the video) a couple of weeks ago.

F1 does what F1 is allowed to do by a restrictive ruleset, so they're not a good analogy. F1 DRS is video game passing physics - and I've read that an F1 car will decelerate at 1g simply from drag along when you release the throttle, so they're obviously very draggy cars and may not benefit from even more drag. As I noted in my first post, the next generation of this will have three positions including DRS on a momentary switch.

It's fun to see the different implementations. Sounds like Jack's been playing with cable activation on his already.

carnut169

I wasn't saying you were wrong, only relating my experience in Formula Continental. I ran with some Formula Fords- same chassis, no wings- and I could EASILY outbrake them esp at the end of the long straights simply bc I could stand on my brakes at speed (bc of wings). I could even feel a difference by adjusting the wings for more downforce- data showed that the advantages in cornering and braking were consumed by drag on the straights.
That said, I never tried an air brake and its apples and oranges.

The best thing you could do for downforce (IMHO) is to make the bottom as flat as possible and install a proper diffuser. Great downforce, no more drag.

The true test will be a 100-0 with the airbrake vs 100-0 with the fixed rear wing, both with threshold braking.

...and then compare laptimes with and without.

Keith@FM

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I've played with the idea of a diffuser. A flat bottom is problematic, this car generates pretty spectacular amounts of exhaust heat. Melting the asphalt backing on Cool-It heat shielding levels of heat.

Once I manage to beat some sense into my Traqmate, I'll try to come up with some good tests. The real test is laptimes, more so than a 100-0 test. The next track day (short track, top speed of 75-ish) has lap timing so I'll see if I can check anything there. It's not ideal with the low speeds and short sessions though, but one of the biggest braking points is on a curve so it should really show the difference between downforce vs drag.

Jack Olsen

The cables are gone. The way I had it rigged was safe, but not friendly to the force a pair of cables could transmit. So now I've gone electric.

Keith@FM

iTrader: (1)

Like Dylan

Jack Olsen

Wired to the steering wheel. I used the horn circuit as a trigger. When I don't have the wing on the back, the horn works instead.


More testing to come.

Ben

iTrader: (33)

Neat

I still have active wing controller on my to-do list. It's item 15411642+65
Brake line pressure will be one of the inputs.

FatKao

It might be worth having a light that turns on when it returns to the down force position. Just in case something binds, or a wire gets disconnected while it's in the low drag position. The inverse would work as well, light is on whenever it's not fully in the down force position. The failure mode of 'light is burnt out' is a little bit better in the former though.