Interesting moveable wing...

[rudypoochris]

"Nothing new under the sun.........."

 

April 1968. Nissan R381 sports car. Split-element, hydraulically-actuated rear 'stabiliser' wing, reactive to speed, cornering forces and braking.

 

Raced. Won. Banned.........

 

In this case is the idea that the wing is more of an air brake than a down force generator?

 

If the idea is to brake on the inside to generate a moment, then I can understand the purpose of such a piece, but why not make it independent of the wing. Hmmm.

[HS30-H]

In this case is the idea that the wing is more of an air brake than a down force generator?

 

No, it was designed as an active rear wing / 'stabiliser' to do more than one job. It wasn't like the air brake on the 1955 Mercedes Benz 300SLR; That was an air brake and nothing else.

 

Looks to me as though the 'Aeromotions' active wing is aiming at something very similar to the 1967/68 Nissan design, but the method of control is different. The Nissan design did not have a 'computer' as such, but it did have a set of sensors to control the hydraulics. It increased wing angle of attack in braking below certain speeds, decreased it in straight line acceleration after a certain attained speed, and actuated different angles of attack for left and right elements according to speed and cornering forces.

 

The mounts for the Nissan design were attached to the uprights/hub castings, so downforce was not acting on the chassis through the springs and dampers - unlike some other early attempts at wings in F1 for example - and this would of course increase unsprung weight.

 

The Nissan design is not very widely known, so I wonder whether the 'Aeromotions' team know about it............?

[johnc]

Chaparral 2E wing wasn't active though, was it?

 

Yes it was. There was a pedal to the left of the clutch that the driver pushed on to change the angle of attack.

[Daeron]

I still don't see this as beneficial. I could be wrong though. Why not let the ARB do the ARB's job and then just go for max down force? Why throw away down force that otherwise would cause the outside tire to generate more traction?

 

That's what I'm thinking too. If you're running really stiff springs, and you should if you're going to make a lot of downforce, then there won't be that much roll, so you can have the whole wing working and get twice the downforce that you would from this thing.

 

"...any transfer of load from one tire of a pair to the other reduces the total tractive capacity of the pair."

-Carroll Smith

 

So, isn't that why, in a turn, the inside wheel would be receiving more downforce?? You have more of the vehicle's weight on the outside rear tire (especially once you start accelerating) so the need for downforce applied to that corner would be less than the need for the downforce on the other corner...

 

Interesting piece though. It is neat to see these things coming to fruition. Oh, and thanks, Alan, for two more pictures added to my "zcar" subdirectory

[rudypoochris]

Well hypothetically if you had 500lbs of force on the right and the left rear tires static lets say. You take it into a corner at maybe it becomes 350lbs on the inside and 650lbs on the outside. With the addition of a single piece wing, say 450lbs inside and 750lbs outside. With this split wing you obtain only the benefit on the inside tire... So 450lbs and 650lbs. Which is better then? The 450lbs inside and 750lbs outside or the 450lbs inside and 650lbs outside? My intuition would say the former. I also realize that it would probably be more like 475lbs inside and 625lbs outside, but for simplicities sake...

[HS30-H]

Yes it was. There was a pedal to the left of the clutch that the driver pushed on to change the angle of attack.

 

By 'active' I meant a little bit more than driver adjustable. I meant active in the sense that it changes automatically according to conditions - outside direct control of the driver........

 

Jim Hall would probably have heard about the May brothers of Germany, who took part in the 1956 Nurburgring sports car race in a modified Porsche 550 Spyder. The car featured a mid-mounted wing, with angle of attack adjustable by the driver through the use of a cockpit-mounted lever:

[JMortensen]

"...any transfer of load from one tire of a pair to the other reduces the total tractive capacity of the pair."

-Carroll Smith

 

So, isn't that why, in a turn, the inside wheel would be receiving more downforce?? You have more of the vehicle's weight on the outside rear tire (especially once you start accelerating) so the need for downforce applied to that corner would be less than the need for the downforce on the other corner...

The way I'm reading it the question here can be restated: "Don't you want downforce on the inside tire to counter weight transfer?" I think the answer isn't necessarily yes. The reason for downforce is independent of the reason why it is advantageous to have less body roll.

 

The more downforce you have the more traction the tires have, and the idea behind a wing is to give vertical pressure without the weight penalty. As a relatively extreme example, if you have a 2000 lb car with 3000 lbs of downforce, when you go around a corner the car still acts (centrifugally) like a 2000 lb car, but has the vertical pressure on the tires of a car that weighs 5000 lbs, which gives the traction advantage. The amount of weight transfer might be insignificant when compared to the total downforce available, making the weight transfer less important to the total available traction than the downforce.

 

To give another example, back in the early 70's they used to attach the wing to the hubs of the car directly so that the body of the car itself could be suspended independently of the downforce. This isolated the chassis from the pressure of the wings and so the cars didn't need to be sprung stiffly. The chassis could roll, but the tires were stuck to the pavement. If the wing were attached to the chassis they would have driven around most of the track on the bumpstops. Again, getting the downforce on the wheels was more important than reducing the roll.

 

When I first saw this wing in action I was thinking that this would be an attempt to keep the inside tire from unloading and spinning on corner exit, which seems to be what you are thinking as well. But if the downforce is high enough, you really don't need to isolate one side or the other to get that traction benefit. And if the total downforce is very low you might be losing more than is gained by cutting the wing size in half.

 

I think this would work well on a softly sprung chassis at relatively high speeds and low downforce levels. If the downforce levels are higher (maybe amounting to more downforce from the wing than there is weight transfer), then it seems to me that isolating one or the other tire is losing potential downforce to gain an effect that may not be necessary.

 

I would suspect that the amount of traction gained on the inside tire alone and the effect of adding traction to just that inside tire would be less beneficial than running a full wing, and getting more traction to BOTH wheels. That is obviously a hunch, but I'm going to stick with it until I see some proof that I'm wrong.

[Flexicoker]

Jon is right, force and mass are independent. If you ignore drag for a moment, more downforce is better. always. laying down the wing and getting less downfroce on the outside is doing nothing beneficial. Think about it this way... if you sit on the left side of the car, does right side lift up? You're going to get the anti-lift benefit for the inside tire regardless of how much downforce you're putting on the outside, unless for some reason the wings are mounted outside the wheelbase.

[JMortensen]

[disclaimer]I'm not an engineer. This is a SWAG.[/disclaimer]

 

I thought maybe there was a way that I could prove my point about this, so I dug out the book that the weight transfer quote comes from, Tune To Win.

 

There is a formula for figuring out weight transfer in the book on p. 36. It is overly simplified to be sure, but it states: lateral load transfer = lat acceleration (g forces) x weight x cg height / track width. The example used is the rear end of a Can Am car, and it breaks down like this. 1.4 x 1080 x 13 / 60 = 328 lbs. That means that 328 lbs moves from one side to the other, and assuming a perfect symmetry, the inside tire reduces to 212 lbs and the outside tire increases to 868 lbs. You can use fig 5 on p.18 to figure out the resultant cornering force, and it works out to 1400 lbs. Who knows what tire they're using to produce the graph in fig 5, but I'm guessing (hoping) that the basic shape of the graph is still useful 30 years later...

 

So my attempt to use this info is as follows. The downforce added by the wing should be independent of the formula, so I just added it to the corner weights and checked them against figure 5 for the following approximations:

 

If you have a wing that produces 150 lbs downforce, and that downforce is spread evenly between the two tires, you get weights of 287 and 963, and a resultant cornering force of 1550 lbs. Add the 75 only to the inside corner and you get roughly 1460 lbs. So having the pressure on both sides does look better. Use a more effective wing and the results are more dramatic. Say for instance that you have a wing that produces 1000 lbs of downforce. Your inside gets loaded to 712 and outside becomes 1368, and the resultant cornering force is 2298 lbs of cornering force. Use the inside 1/2 of the wing and you get only 1990 lbs.

 

While it is true that adding force to the inside corner makes a larger difference than adding force to the outside corner, I think it's pretty clear from this calculation that adding downforce to both makes more available cornering force. It may be conceivable that the drag that comes with the downforce is enough of a hindrance to make an adjustable wing more suitable, but even then it looks like a single adjustable wing makes more sense than a side to side adjustable.

[tube80z]

In thinking about this some more I wonder if the wing is more about yaw moments rather than downforce. I could see that helping to make the car more stable in turns.

 

Cary

[Daeron]

Jon,

 

Your answers, as usual, are appreciated and incredibly insightful.. the best counter I can come up with is to say that IF this double element wing seems to have an impact over a similarly sized single element wing with comparable total impact, then the first place I would look to see where that difference was felt would be the varied downforce on the inside corner. Something of a lame-duck argument, but call it a restatement of my earlier point.

 

The only question I have left is to ask if there is any way that the increased downforce on the inside corner could be a detriment. Would it not also help to curb body roll? (is that what the post above me is concerned with? the phrase "yaw moments" is not one I am fully familiar with.)

 

Once again, thanks for the description.. one of these days I really have to put down the fiction I read and get into some chassis tuning technical works. My brother has one or two, and those (along with the standard L-engine rebuild.mod books by honsowetz and company) have been on my required reading list for too long.

[JMortensen]

...the best counter I can come up with is to say that IF this double element wing seems to have an impact over a similarly sized single element wing with comparable total impact, then the first place I would look to see where that difference was felt would be the varied downforce on the inside corner.

This is basically what Cary is talking about with the yaw moments idea. Yaw moment is a fancy term for how much force is trying to swing the ass end around in a turn.

 

My argument there is that it still appears as though there is more total cornering force available when the WHOLE wing is used, and one would assume that this increase in grip would reduce the tendency of the car to yaw without needing to differentiate one side from the other. Again, it is true that affecting the inside tire makes a bigger difference to available grip than the outside tire (based on the quote in my sig), but more total available grip should outperform in every situation, and more grip would equal less yaw in every situation, unless I'm missing something.

 

It also seems that the old Nissan version from the 60's would do a better job differentiating side to side since that wing was attached directly to the hub, where the one in question attaches to a sprung chassis. I'm not sold on the old version either, but I think it has a better potential to have a real effect on yaw than the new one.

 

If the idea were to prevent yaw aerodynamically, it seems like a rudder would be a better device to perform that task. Since cars have tires, and they are powerful yaw dampers in and of themselves, adding a rudder to a car seems redundant.

[Gollum]

Seems like it might be useful for say, a street car that also endures severe track conditions.

 

It's ability to increase downforce under only certain conditions is nice, but any adjustable wing could do that, so why the split?

 

To me it seems like it's more of an anti-roll device than anything else. As stated, more total grip is better than less on the more desired side. Though if you're running soft suspension with mild sway bars (or none at all) with an open rear diff... This seems like it might have a pretty nice effect.

 

But for a purpose built racer it doesn't seem very logical to me.

 

Anyone have an educated guess as too how much it will be able to afftect front tire traction? I wonder if it might help reduce understeer on corner exit, or create it? We know that if we just add a big wing to the back of a Z it lifts the front up quite a bit, so will adding downforce on the inside rear lift the inside front? If so that could be BAD. Adding more downforce overall just seems simpler and more beneficial.

[91_4x4runner]

Doesn't NASCAR have something similar on the top of their cars for high speed turns? I think I saw something on the History channel about them. Just a big plate on the rear part of the cabin (above the rear window) that comes up on turns...

[JMortensen]

Doesn't NASCAR have something similar on the top of their cars for high speed turns? I think I saw something on the History channel about them. Just a big plate on the rear part of the cabin (above the rear window) that comes up on turns...

NASCAR has airbrakes that pop up when a car spins all the way around. I think they're supposed to prevent the cars from flying as well. They don't have any active aero for going faster though.

[jt1]

So far as split wing versus one piece, the tires are going to be a big factor in deciding which is faster. If the outside tire can handle the additional load without overheating, the advantage may go to the solid wing. If the outside tire can't handle this extra load and heat, then the split wing loading the inside tire could be the faster setup.

 

Rather than a split wing, what if you could shift the solid wing laterally? Then you would get the total downforce, but be able to shift it to the side of the car you desired.

 

John

[johnc]

You guys are assuming the split wing distributes vertical loads discreetly side-to-side. It doesn't. Total vertical load is distributed primarily through BOTH vertical supports. At most, one support might see 25% of the total load and the other might see 75% of the total but I would very surprised to see that much of a difference. Plus, the supports appear to be spaced about 24 to 30" apart and centered on the car, further diminishing side-to-side bias.

 

The benefit, IMHO, comes more from yaw control and drag reductions then variances in side-to-side vertical loading of the vehicle.

[JMortensen]

You guys are assuming the split wing distributes vertical loads discreetly side-to-side. It doesn't. Total vertical load is distributed primarily through BOTH vertical supports. At most, one support might see 25% of the total load and the other might see 75% of the total but I would very surprised to see that much of a difference. Plus, the supports appear to be spaced about 24 to 30" apart and centered on the car, further diminishing side-to-side bias.

 

The benefit, IMHO, comes more from yaw control and drag reductions then variances in side-to-side vertical loading of the vehicle.

Good point John.

[Daeron]

Let's not forget the incredible value of this piece in one aspect:

 

 

It shows us how little we really KNOW for certain about how much, and in which ways, it can make an impact... and I am imagining that even the people who invented it have not yet fully charted its effects. Its also led to a lot of introspection and stimulated alot of thought here alone thus far.

 

Humble pie, anyone?

[Flexicoker]

The NASCAR deal isn't a brake, its more of a pressure relief device:

 

http://entertainment.howstuffworks.com/nascar-safety2.htm