Delta wing car concept

[PhillipM]

Given the same overall tyre contact patch area, the same total weight, the same tyre grip coefficient, equally good camber control, tyre sizes set such as to match the vertical load distribution under braking (whatever that is, be it front or rear biased), etc, etc, the total grip will be the same, and that means the potential brake performance will be the same. To make the car more stable you have to "give up" some of that potential braking performance by biasing the brakes forward of optimum setting.....

I agree with everything machin has put here, and just need to add, if you lock a rear wheel at any point, you'll soon find out it's a whole lot less stable with that big pendulum of weight swinging around on the way into a corner.... 4

Might be why they've gone so narrow at the front, to try to make the car understeer/neutral on turn in if it gets a little flighty

[Scania]

what's the different between wing car & if I remove SR3's wing & redesign the floor if there are enough space?

[machin]

what's the different between wing car & if I remove SR3's wing & redesign the floor if there are enough space?

If you take a Radical SR3, throw away its spaceframe chassis, fibreglas body, wing and engine, build instead a carbon monocoque with full ground effects and install the Deltawing's engine and gearbox..... there would be very little difference.

Being serious though... not a lot, and that's the point:-

The performance differentiator between Deltawing and today's Le Mans cars is the weight and the ground effect, so if you take an SR3 (which is already very lightweight) and redesigned it to fully utilise ground effect and have the same engine/transmission as Deltawing, I think the calculations in my previous posts show it would be quicker than Deltawing because of the inherent advantages of a conventional rectangular car with something like 45:55 weight distribution compared to a Delta shaped car with 27.5:72.5 weight distribution.....

[machin]

if you lock a rear wheel at any point, you'll soon find out it's a whole lot less stable with that big pendulum of weight swinging around on the way into a corner.... 4

Might be why they've gone so narrow at the front, to try to make the car understeer/neutral on turn in if it gets a little flighty

Good point!

[Jersey Tom]

And how would a narrow front lead to under-steer?

[machin]

And how would a narrow front lead to under-steer?

Understeer is caused by a relative lack of front grip, right?

There's two issues with the Deltawing which may mean it understeers... the narrow front track means that for a given overturning moment dealt with by the front tyres there needs to be more load transfer from the inside tyre to the outside to resist that moment (since the anti-overturning moment arm, the track width, is lower)... that loads up the outside tyre and reduces its grip....

The fact that the tyre is also narrower than a typical car means it has a double whammy... the load per unit area is higher, and therefore for a given tyre compound the grip coefficient goes down.....

Now the question is... does the rear tyre lose grip first or the front... the rear is bad because it takes the bulk of the static mass and takes the majority of the load transfer... but at least it has a wide track and wide tyres... the front is bad because it has a narrow track and narrow tyres.... whether it understeers or oversteers depends on how these, and other factors (like roll resistance, suspension geometry, etc) stack up -you can't tell by looking at its shape to know which way it'll go.... (but as PhilipM said possibly why they went for real narrow front tyres -to make sure it understeers) -Or the alternative view; you could argue that they went for overly large rear tyres (As JT, you pouinted out earlier, again to make sure it understeers).

So you can't tell if it'll understeer or oversteer, just from the shape... but you can see a Delta-shaped car is bad for cornering performance.... here's a simple way to look at it-narrow track results in higher load transfer, and that loads up the outside tyres, and causes a lack of grip, agree?

Well the Deltawing's average track is far less than a rectangular car's... therefore for a given cornering G-force the average load transfer will be higher... and cornering performance (all else being equal) will be lower....

[GSpeedR]

And how would a narrow front lead to under-steer?

Understeer is caused by a relative lack of front grip, right?

There's two issues with the Deltawing which may mean it understeers... the narrow front track means that for a given overturning moment dealt with by the front tyres there needs to be more load transfer from the inside tyre to the outside to resist that moment (since the anti-overturning moment arm, the track width, is lower)... that loads up the outside tyre and reduces its grip....

I don't really agree with this one. In the front-view, the overturning moment is reacted by loads paths in parallel (front axle and rear axle), and thus the smaller front track results in less moment reacted...meaning less weight transfer of the front axle. For example, tricycles resist 100% of the overturning moment with the paired axle; or taken the other direction a vehicle with an infinitely long rear track will react 100% of the overturning moment and also lift the inside tire instantaneously. There's a chassis connecting these axles together so load transfer cannot be analyzed independently.

There's a reason why the tires are able to be so narrow on the front: 1.) static CG position which you mention below; 2.) the relatively narrow front track.

The fact that the tyre is also narrower than a typical car means it has a double whammy... the load per unit area is higher, and therefore for a given tyre compound the grip coefficient goes down.....

Now the question is... does the rear tyre lose grip first or the front... the rear is bad because it takes the bulk of the static mass and takes the majority of the load transfer... but at least it has a wide track and wide tyres... the front is bad because it has a narrow track and narrow tyres.... whether it understeers or oversteers depends on how these, and other factors (like roll resistance, suspension geometry, etc) stack up -you can't tell by looking at its shape to know which way it'll go.... (but as PhilipM said possibly why they went for real narrow front tyres -to make sure it understeers) -Or the alternative view; you could argue that they went for overly large rear tyres (As JT, you pouinted out earlier, again to make sure it understeers).

I believe that there are significant suspension geometry issues that are now present with the lessened packaging and perhaps reduced ability for downforce (not my area of expertise to I won't comment).

So you can't tell if it'll understeer or oversteer, just from the shape... but you can see a Delta-shaped car is bad for cornering performance.... here's a simple way to look at it-narrow track results in higher load transfer, and that loads up the outside tyres, and causes a lack of grip, agree?

Well the Deltawing's average track is far less than a rectangular car's... therefore for a given cornering G-force the average load transfer will be higher... and cornering performance (all else being equal) will be lower....

I disagree with the first paragraph for the reasons explained above, but I agree with the second paragraph. I tend to side with most people here in that this is a very contrived product that probably will work but it is likely inferior to more traditional chassis designs with similar power/weight and tires.

[Jersey Tom]

+1 to GSR. Can't think of the front suspension by itself, and the rear suspension by itself.

There's an overturning moment from the inertia of the vehicle, which is reacted by the front and rear suspensions simultaneously. Very narrow front track in relation to rear will want to bias a very large share of the load transfer distribution to the rear.

[machin]

In the front-view, the overturning moment is reacted by loads paths in parallel (front axle and rear axle), and thus the smaller front track results in less moment reacted

I agree, which is why I quantified my statement with the underlined section (coloured red here):-

the narrow front track means that for a given overturning moment dealt with by the front tyres there needs to be more load transfer from the inside tyre to the outside to resist that moment

My main point was that you can't take these things in isolation... for example your statement:-

a vehicle with an infinitely long rear track will react 100% of the overturning moment [at the rear]

....Would not be true if the rear track also had zero roll resistance, and the front had a even just a little bit of roll resistance (since zero x infinite is still zero)... so as I said originally, you can't tell by the shape whether it'll understeer, or oversteer, you need to know quantifiable specifications for all the other parameters.

But as you agree... the fundamental thing is the average track is lower than a rectangular car, and that's a bad thing.

[GSpeedR]

In the front-view, the overturning moment is reacted by loads paths in parallel (front axle and rear axle), and thus the smaller front track results in less moment reacted

I agree, which is why I quantified my statement with the underlined section (coloured red here):-

the narrow front track means that for a given overturning moment dealt with by the front tyres there needs to be more load transfer from the inside tyre to the outside to resist that moment

My main point was that you can't take these things in isolation... for example your statement:-

a vehicle with an infinitely long rear track will react 100% of the overturning moment [at the rear]

I guess that I would claim that making that assumption (underlined and highlighted in red) isn't reasonable to make if the discussion is about understeer/oversteer aka full vehicle balance. For an axle in isolation, I agree that it is true, and if we are talking about average track widths then again I'll side with it.

....Would not be true if the rear track also had zero roll resistance, and the front had a even just a little bit of roll resistance (since zero x infinite is still zero)... so as I said originally, you can't tell by the shape whether it'll understeer, or oversteer, you need to know quantifiable specifications for all the other parameters.

But as you agree... the fundamental thing is the average track is lower than a rectangular car, and that's a bad thing.

I usually try to avoid things like 0*infinity. I had assumed that we were still shortening front track width and holding all other parameters equal, but if not then one can't conclude anything regarding balance.

[Jersey Tom]

Not to mention there's a pretty substantial limit to how crazy you can get with spring and bar rates for ride / mechanical grip requirements.

[machin]

I usually try to avoid things like 0*infinity

I agree that zero roll resistance is pretty unlikely , but I also think a track width of infinity is pushing things a bit too!

....and holding all other parameters equal

You're right, lets hold all things equal and put some numbers to the problem... equal spring stiffness, tyre size, cg height, etc etc, and just have different track width front to rear:-

If the front track is half the rear track (lets say rear is 2m and front is 1m), and everything else equal the rear would take 66% of the cornerng moment and the front 33% of the moment. Assuming the over-turning moment is 100kNm (I'm just using an "easy" number!) the front would take just 33.3kNm and the rear 66.6kNm.

So, taking the front first; 33.3kNm, divided by 1m track width requires 33.3kN on the outer wheel to resist the moment. (i.e to stop the car rolling over).

Taking the rear, 66.6kNm divided by a track width of 2m requires an identical 33.3kN to resist it (and again stop the car rolling over)...

....so the narrower front on its own actually doesn't tell you anything about whether the car will oversteer or understeer.... if everything else were equal...

Don't you agree?

But, just to reiterate the point we've already agreed on, for other readers: The average narrower track means a delta-shaped car will have more force transfer during cornering than a rectangular car which has equal front and rear tracks (and equal to the delta-shaped cars rear track).

[Jersey Tom]

Revisit your assumptions and math.

Sprung mass will have a given roll displacement. Wider rear track means a greater resultant vertical displacement of the LR and RR compared to the LF and RF. With equal wheel rates on all four corners, the rear tires thereby see more load trasnfer.

[bill shoe]

Crap JT!!, you are conspicuously avoiding seeing the forest for the trees. Machin has done logical analysis that shows how the DW advantage lies in its non-conformity with current rules rather than its narrow front track. Then you argue with him about detail nuances of vehicle dynamics modeling.

You recently posted something to the effect of "I like to use the simplest thing that gets the job done accurately". Machin has done that.

I really like having your vehicle dynamics modeling perspective on this forum, but damn!! When you eat an Eggo waffle in the morning do you call the 1-800 number to tell Kellogs they are not modelling the roll stiffness distribution of the waffle correctly? Just eat the damn waffle.

[Jersey Tom]

This is not nuance - it is fairly fundamental and a key gripe of mine regarding the DW design. And while yes, I am a fan of simple yet reasonably accurate solutions, machin's assumption was wholly flawed. An important thing to point out.

While indeed one cannot say for certain how the vehicle will behave, IMO the DW group have made a problem much more involved than it need be.

Incidentally the high load transfer across the rear may make for interesting differential and powertrain requirements.