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stafford1500
stafford1500 GRM+ Memberand Dork
7/7/19 6:16 p.m.

In reply to Adrian_Thompson :

I have heard that the Brabbhams had an interesting response when you revved the engine in the garage or pits. The car would pull down and slowly recover as the engine revs came back down. Either way using existing hardware to do another job is the hallmark of creativity in motorsports. Always make sure every part does at least two jobs.

Also anytime you get a rule written against whatever you are doing, you have made it in motorsports (Stampie, looking at you for this one...)

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/8/19 8:20 a.m.
stafford1500 said:

I recall Keith Tanner setup a DRS style wing for one of his cars. Simple and effective.

Actually, it wasn't DRS, it was an air brake. When I hit the brake pedal, the wing flipped up and stalled out. Loads of extra drag and (if I understand this right) the center of aero pressure moved way back. This not only slowed the car, but added stability. I got the idea after following a McLaren MP4-12C around a complex of corners and saw the factory aero dancing around.

I'm not convinced DRS does much on a car that isn't running massive aero with the drag that goes with it. Guys build it because it's an F1 thing, but that's funky reasoning.  IIRC F1 cars will decelerate at close to 1g from drag alone, so reducing drag at nearly 200 mph is really effective. On my Miata (a modified street car with an engine that more than 4 times as powerful as the stock one), I can pull my aero through the air well enough but I need help stopping. 

One big problem with my setup is that I lose visibility out of the rear window when it engages. 

Lemons still allows some active aero. The most clever I've heard of is an ironing board that was "activated" by a bowling ball in the trunk. Hit the brake, ball goes forward, "wing" goes into high AOA. Accelerate, ball goes back, wing flattens out. I don't believe it was raced for obvious reasons but I love the concept.

Johnny_at_NineLives
Johnny_at_NineLives GRM+ Memberand New Reader
7/8/19 9:04 a.m.
Keith Tanner said:
stafford1500 said:

I recall Keith Tanner setup a DRS style wing for one of his cars. Simple and effective.

...i 'm not convinced DRS does much on a car that isn't running massive aero with the drag that goes with it....

 

Yes and No, 

 

On a single element wing Yes having a DRS won't do much. As you can see on our CFD chart here of the wings we make. @ 140 mph there is a 22Lbs of drag swing at 140 mph. your average sports car like a Corvette makes around 400lbs of drag at a similar speed.  add the drag from the cart to the 400lbs base, we get the following. Going from 417 too 439lbs of drag is only a 5% swing.  in our experience, the stopwatch will like that, but drivers will only notice about a 7% change. You, as a driver,  not being convinced does correlates to our findings.  

Where the big change is on Dual elements.  like ours pictured above. the main wing is set at 0 AOA and you adjust the second element for downforce. now our chart doesn't show drag with the second element open but it would only add a few lbs anyway. knowing that, we can use the chart as an example of what might happen. since we are talking about hypotheticals anyway it won't hurt. @140 mph if you opened the second element you could change your drag from 63 too 17 lbs of drag. That would take the corvette drag from 463 lbs of drag to 417 a 11% reduction. Frankly speaking, anything we see that's over 10% change is a really big deal. So a driver would definitely notice that. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/8/19 10:14 a.m.

Thus my comment about massive aero. DRS would let you stack a lot more wing on the car for the times you need it, but you'd have to design for it from the start. Multi-element wings are still pretty unusual in the converted street car arena.

It would be interesting to see on the stopwatch which would be more useful, 10% less drag on the straight or a whole bunch more drag under braking. My Traqmate unfortunately committed suicide when I put my air brake on so I don't have data, but I know that my confidence level was a lot higher under braking with the airbrake engaged.

Robbie
Robbie GRM+ Memberand UltimaDork
7/8/19 10:27 a.m.

60 lbs of drag using f=ma means about .02 g of braking, right?

Edit, assuming a 3000lb Corvette.

pinchvalve
pinchvalve MegaDork
7/8/19 10:37 a.m.

Smokey Yunik built a 7:8 scale version of a Chevelle for NASCAR.  In truth, Smokey moved the body of the car backward three inches for better weight distribution, raised the floor and smoothed out the underside of the car for better aerodynamics, and made the bumpers and fenders flush with the rest of the body.  It looked stock and it won, and people have called it a 7:8 scale, even though it was just clever manipulation. 

I think you could take a 2-Series and swap over a lot of M3 parts and do the same thing. What?  It's a stock M3? Does it look smaller?  I don't think so.  

egnorant
egnorant SuperDork
2/12/20 5:56 p.m.

I see these devices that increase traction or reduce drag...but...are there designs in use to improve on other forces? Using air to counter body roll or aid in steering perhaps? I notice the dirt track racers with the huge roof/wing with the huge side panels to do whatever they do.

 

I was thinking about something that would react to steering to add force towards the inside of the curve or or even help twist the car to aid steering direction. Or am I just being silly?

 

Bruce

R56fanatic
R56fanatic New Reader
2/13/20 12:56 a.m.

Like an airplane rudder?  LOL that would be funny to see but I think the drag penalty would be pretty high.  Lamborghini has their active aero system where the computer can stall one side or the other of the rear wing to shift the downforce durig cornering.

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
2/13/20 2:05 a.m.

In reply to egnorant :

one thing dirt track racers have in their benefit is, they're only turning one direction.  And they have 'very large elements'.

On a more track-focused point... I think there was a GTR at OneLap in 2009 or 2011 (?) that had the "Aeromotions S2.Dynamic" wing.. I don't think they were much faster than Leh Keen in the other GTR, and then it was moot when the motor on the active wing car went pop!

Off hand, there's a couple of issues with this.  The first is, the system control the actuators needs to be smart enough to tell 'what the driver is doing', because if you in a slide, you don't want the aero to upset the car chasing your inputs.

Fortunately, though, most of these systems are only on a single element device.  So, the change in downforce for one side vs. the other side will be relatively low.  And that's before you account for the fact that the effect will be reduced futher, since the downforce is summed over the half span, and (due to 3D effects) is biased towards the center... so the "moment effect" of the differential is pretty low.  There's a reason aircraft, mostly, have their roll-control devices (predominantly ailerons) out at the tips of the wings.

Robbie
Robbie GRM+ Memberand MegaDork
2/13/20 11:37 a.m.
egnorant said:

I see these devices that increase traction or reduce drag...but...are there designs in use to improve on other forces? Using air to counter body roll or aid in steering perhaps? I notice the dirt track racers with the huge roof/wing with the huge side panels to do whatever they do.

 

I was thinking about something that would react to steering to add force towards the inside of the curve or or even help twist the car to aid steering direction. Or am I just being silly?

 

Bruce

Check out some time attack cars. I was watching a video a while back about the front wing on an unlimited time attack build.

At the outside edges (just in front of the wheels) they rotated their wing elements about 45degrees inward. If you think about the airflow there, the air is hitting the front of the car and then rushing around the side. So really they are just aligning the wing to the prevailing air direction. 

But! What ends up happening is that when you turn, the inside of the car rolls up - increasing the angle of attack on that inner wing, which increases the downforce and drag on that inside side - nice!!

stafford1500
stafford1500 GRM+ Memberand Dork
2/17/20 2:20 p.m.
Robbie said:
egnorant said:

I see these devices that increase traction or reduce drag...but...are there designs in use to improve on other forces? Using air to counter body roll or aid in steering perhaps? I notice the dirt track racers with the huge roof/wing with the huge side panels to do whatever they do.

 

I was thinking about something that would react to steering to add force towards the inside of the curve or or even help twist the car to aid steering direction. Or am I just being silly?

 

Bruce

Check out some time attack cars. I was watching a video a while back about the front wing on an unlimited time attack build.

At the outside edges (just in front of the wheels) they rotated their wing elements about 45degrees inward. If you think about the airflow there, the air is hitting the front of the car and then rushing around the side. So really they are just aligning the wing to the prevailing air direction. 

But! What ends up happening is that when you turn, the inside of the car rolls up - increasing the angle of attack on that inner wing, which increases the downforce and drag on that inside side - nice!!

You could also tie into a power steering system and control the angle of attack via hydraulics (or mechanical or electrical). That paired with yaw generating devices (like a rudder) could create some very effective steering responses. Slow speeds would still start to get back to no effect since you need some airspeed for aero to work properly.

That speed impact gets ignored too often.

noddaz
noddaz GRM+ Memberand SuperDork
2/19/20 5:14 p.m.

Didn't NASCAR teams have rear spoilers that flexed at speed to reduce drag?  And NASCAR countered that by testing the rear spoiler by hanging a weight on it to test deflection?  (I am not making this up!)

Robbie
Robbie GRM+ Memberand MegaDork
2/19/20 9:52 p.m.

In reply to noddaz :

Not only bendy ones... They also used hidden actuators, in fact I think they used the trunk motors that first showed up in Lincoln soft close trunks.

NOT A TA
NOT A TA SuperDork
2/19/20 10:25 p.m.
Robbie said:
egnorant said:

I see these devices that increase traction or reduce drag...but...are there designs in use to improve on other forces? Using air to counter body roll or aid in steering perhaps? I notice the dirt track racers with the huge roof/wing with the huge side panels to do whatever they do.

 

I was thinking about something that would react to steering to add force towards the inside of the curve or or even help twist the car to aid steering direction. Or am I just being silly?

 

Bruce

Check out some time attack cars. I was watching a video a while back about the front wing on an unlimited time attack build.

At the outside edges (just in front of the wheels) they rotated their wing elements about 45degrees inward. If you think about the airflow there, the air is hitting the front of the car and then rushing around the side. So really they are just aligning the wing to the prevailing air direction. 

But! What ends up happening is that when you turn, the inside of the car rolls up - increasing the angle of attack on that inner wing, which increases the downforce and drag on that inside side - nice!!

I believe that's Andrew Brilliant's "infinity wing" design.

stafford1500
stafford1500 GRM+ Memberand Dork
2/20/20 12:02 p.m.
noddaz said:

Didn't NASCAR teams have rear spoilers that flexed at speed to reduce drag?  And NASCAR countered that by testing the rear spoiler by hanging a weight on it to test deflection?  (I am not making this up!)

There was a time when the spoiler defelction test was conducted at each event. That was when the manufacturers each had different shapes and the angles could be adjusted. The spoilers are spec parts now and the attachment is the same for everyone, so no need to do that test anymore, we all have the same parts.

noddaz
noddaz GRM+ Memberand SuperDork
2/28/20 6:23 p.m.

A question about spoilers on the edge of a deck lid.  If there is a gap (1/2 inch?) between the deck lid and the lower edge of the spoiler what is the effect of the air bleed off under the spoiler?

sleepyhead the buffalo
sleepyhead the buffalo Mod Squad
2/29/20 1:24 a.m.
noddaz said:

A question about spoilers on the edge of a deck lid.  If there is a gap (1/2 inch?) between the deck lid and the lower edge of the spoiler what is the effect of the air bleed off under the spoiler?

so, I've been looking at this pretty slowly over the last month... in 2D, with Javafoil... on a miata profile.

so, I've got enough experience to say "it depends"... although "what is the effect of the air bleed off under the spoiler"... is kind of wrong way to look at it.

If downforce is the goal, then the point of placing a spoiler/wing near a trunk with a gap is to get higher speed flow onto the bottom side of the spoiler/wing.  Doing that means you can usually run to a higher angle on the wing without stalling the flow (compared to the same section in free air), and then get more downforce from the element.  theoretically.

depending on a bunch of things.... one knock-on effect is that you're putting a low pressure zone in range of 'activating' pulling air out from under the car's bumper.  This can mean more downforce... although, with javafoil... and my input parameters, it seems like it's over-predicting the 'ground effect' downforce of a miata.  So, when I add the gapped spoiler, it changes things enough that javafoil starts predicting an overall loss of downforce... despite the region of low pressure growing under the idealized miata-car-section-shape.

all of that stuff above is very sensitive to: the shape of the rear window/trunk, gap above the trunk, where the 'nose' of the foil is 'longitudinally' compared to the trunk, and the shape of the foil section (both nose radius, and overal thickness and camber).  And cars being what they are, unless you make a complex shaped spoiler-wing thing, you're going to push to optimize one area and 'just deal' with some inefficiency elsewhere... from a 'distance from the centerline' perspective.

All those caveats aside.  My 'number-crunching and not real-world tested' experience so far indicates that 1/2" is too little a gap, most likely.  You probably want to have 1" of gap, minimum.

If you can, you probably want a mount that allows you to change the gap of the spoiler from 1 to 3 inches, while also allowing a range of angles from 5 to 30deg.  And, in order for this to work, you'll want a section with a 'reasonably rounded nose' profile... aluminum/plexi sheet need not apply.

standard statement:  caveat emptor, caveat lector, ymmv, iirc, etc.

chada75
chada75 HalfDork
1/20/21 5:57 p.m.

When I was little, I studied aero for airplanes. Dad's friend raced 4 cylinder late model. He let me build a "Ford probe" that had the right side flushed flat with the wheels, a side glass, and a sail panel on the right rear. The body was banned after the first race.

The Super Modifieds run a hydraulic-powered top wing that lays flat on the straight and rises during braking. Its not banned, however.

Speaking of Supers, a team ran one in the early 80's at the Moody Mile in NY with the World of Outlaws. They had to run a wing and ran the smallest wing they could on top. The WoO mandated a wing size afterwards.

 

JaxRhapsody
JaxRhapsody New Reader
7/4/21 9:49 p.m.

In reply to R56fanatic :

In my several sketchbooks and loose paper; I have a few sketches of sports cars and muscle cars that have wings like a 69 Daytona, where the supports are also rudders.

Apexcarver
Apexcarver UltimaDork
7/7/21 10:08 a.m.

A part of me loves imagining what a no-holds barred series would be like...  right up intil G forces killed the driver. Who knows, we might see a series of robot driven racecars that let things lose. 

 

 

Another fun area of discussion could be unintended hazards from aero regulations. 

 

 

84FSP
84FSP UltraDork
7/7/21 9:16 p.m.
ShawnG said:

The F-Duct in the McLaren cars...

I am flat amazed some iteration of this is not on street cars.  All the benefits and none of the costs of downforce.

Adrian_Thompson (Forum Supporter)
Adrian_Thompson (Forum Supporter) MegaDork
7/8/21 8:44 a.m.
84FSP said:
ShawnG said:

The F-Duct in the McLaren cars...

I am flat amazed some iteration of this is not on street cars.  All the benefits and none of the costs of downforce.

It is, it's just that instead of using the drivers hand to change airflow to stall the wing, road cars use sensors and motors to change the angle/height of rear wings.  That is explicitly disallowed in F1 (movable aerodynamic devices) so they needed a 'legal' loophole to archive the same effect.  Can you imagine the NVH implications of an air tube directed through the cabin with freaking big hole for the driver to to cover with their hand?

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/18/21 9:14 a.m.
stafford1500 said:

One way that has been used to overcome these restrictors is a mechanism that physically opens a bypass when the engine is running (a rally team in Europe). That was the reason some series went to the extreme of verifying the engine would stall if they plugged the inlet restrictors.

If you are thinking of what I think you may be thinking of (the TTE cheat), there was no bypass.  The restrictor is bolted to the turbo inlet and must be no more than 50mm from the compressor blades.  What there was, was an ingenius bit of machining and some springs that allowed someone to spring the restrictor 5mm forward and hold it in place with the hose clamp that attaches the inlet ducting to the turbo.  There was also some room through the mechanism for air to travel, but most of the benefit was from moving the restrictor further from the turbo.  The key to the cheat was that removing the hose clamp for inspection access would cause the restrictor to snap back.

Ever since then the restrictors have a maximum OUTSIDE diameter at the choke point, too.

 

Now.  Throttle response is key, and the rules say that all air entering the engine must pass through the restrictor.  Ford, on one generation of the WRC Focus, had a large air tank mounted in the bumper that would store turbo compressor output, and it would be released into the engine on initial acceleration.  Not only does this eliminate lag when you're just feeding the engine from a 30-40psi air tank, but it allows a momentary bit of more power than could ordinarily be allowed with a 32mm restrictor.  (Might still have been 34)  All of the air entering the engine did pass through the restrictor, just not all at the same time.

ShawnG
ShawnG UltimaDork
7/18/21 12:25 p.m.
Apexcarver said:

A part of me loves imagining what a no-holds barred series would be like...  right up intil G forces killed the driver.

I thought that's what Can-Am was supposed to be? 

Pete. (l33t FS)
Pete. (l33t FS) MegaDork
7/18/21 1:36 p.m.
ShawnG said:
Apexcarver said:

A part of me loves imagining what a no-holds barred series would be like...  right up intil G forces killed the driver.

I thought that's what Can-Am was supposed to be? 

https://en.m.wikipedia.org/wiki/Firestone_Firehawk_600

 

As it turns out, running flat out on a banked oval with lots of downforce will enable high enough sustained cornering forces (5 G sustained for 14 to 18 seconds per 23 second lap) that our squishy meat-computers stop working correctly.

Not technically the forces directly killing the driver, but confusion/loss of consciousness could certainly lead to a fatal collision.

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