HeresJohnny - first of all, bravo, for trying some active aero.
I do see some theoretical problems with that though - usually from what I've seen air brakes are done with spoilers, not so often with actual airfoils. Coming into a braking zone and having the airfoil drastically change angles as you transition onto the brakes could do some very funky things to your grip balance - you might get a sudden increase in rear downforce as the angle increases, taking weight off your front tires momentarily, and then all rear grip will go away a moment later as the wing passes its stall angle. This would be much worse in higher speed braking zones - there are several tracks around here that have 130 mph to 50-70 mph braking areas. If this is intended for autocross, it might work better as the wing won't be creating massive downforce at those speeds, so the change in downforce as the wing moves will be less severe..

Just thinking out loud here.
-Ryan

 

Could you revise your design to only actuate the second element of the wing? I'd expect that to make it less susceptible to the issues that Ryan voiced.


I've put some thought into active aero and have what I think would be a decent design for an active spoiler/air brake. It'd resemble any other comically large auto-x spoiler when raised and lay flat against the trunk lid with a few inches of overhang off the back when lowered. If somebody wants my CAD files, parts list, and control logic, I'd be glad to share. I mean, it's an untested design and my files aren't complete but it'd make a good starting point. It's something that I eventually would like to make however I need to get my car running first.

For example, this is the assembly that bolts to the inside of the trunk lid and forces the base of the spoiler back to raise it up. If my math is right, this will push the spoiler though it's full range of motion in under a second.

 

Flip the end plates out?

Pulling them back in would require some force though.

Another reason for keeping the end plates huge

 

It's a good idea. But would take a ton of force on the mounts. The boot skin may not be strong enough. I wanted to do something similar. What motor/solenoid did you use?

 

Yeah.. needs 1/4" steel uprights for that..

 

What I was thinking of awhile ago was to put a speed brake that would be like the factory trunk spoilers (or like Lightyears car with the ABS plastic around the back of the car) , then under braking it would pop up being 4"-6" taller to catch more air. That way it wouldn't disturb the air going to the rear wing as much.

Kinda like this

 

Is the effective braking from air resistance greater or lesser than the mechanical force of the brakes and rear tires firmly planted?

If the downforce increased in the rear, would that lift weight off the front?

If the stall angle of the rear airfoil is exceeded and the downforce indeed goes away, does the rear end get light? In a very high speed corner where trail braking is occurring, a reduction in downforce could make the rear end catastrophically loose.

I think a smaller angle change might be very effective on a fast track, but as stated before, the large change would likely be effective at lower speeds such as an autocross.

But don't get it twisted, I'm very impressed with the design and the work you put into this. I would love to experiment with it.

 

Jeremy Clarkson said that the Veyron's air brake produces more braking power than a normal car

 

My idea was to have 3 positions. Base setting would be at aoa that you require. And run low angle for straights, and high angle for brakes. Could have a switch under acc, and brake to trigger. Or buttons on steering wheel. But was only going to change a few degrees each way. Flipping up all the way will make a huge difference. Be interesting to see how you go.

 

^^ Yes! It will take time to determine what is most effective and how much is too much in terms of stall on the wing and the potentially dangerous adjustments to the car's attitude but we all applaud you breaking new ground. Please keep us updated. It may warrant its own thread if you end up with bunch of testing and design revisions.

 

Used a power seat motor from a BMW, was the right speed and really strong

 

I'm sure you're right, I started with just the top wing flipping but go carried away

 

I started out with just the top wing moving but more on the DRS lines, then went the air brake route

 

It's been a concern, they are stainless steel and there are 1/4" plates on the underside where it bolts through.
I'm thinking the boot skin may deform, we will soon see.

 

Well are you trying to slow down faster or increase the downforce? For example a parachute doesnt cause downforce but will stop you a lot faster than a spoiler would.

 

*

 

The plan was to put the momentary switch under the brake pedal which would be closed off during hard braking. Although I was surprised how little the peddle arm actually moves when applying the brake so finding the right location will be tricky. Had also considered maybe taking a signal from the tachometer so it only allowed the air brake to operate above/ below a predetermined speed. But at the moment it's little steps at a time and see where it takes me TBH.
Thing is I'm not racing as such just doing track days but I like the challenge and testing bit nearly as much as the sideways action.

 

Are your spats/canards/whatever they are called in front of the tires vertical or do they have any slant to them?

 

I have only thumbed through various CCRs but my hunch is active aero would immediately put you into unlimited classes if it is allowed at all. This is probably more a project for the track day warriors many of us are.

 

Hey, Redline Time Attack allows active aero in Modified. You have to keep your dash and glove box because they are supposed to be "street cars", but active aero/DRS/etc. is all totally acceptable.