## Delta wing car concept

Please discuss here all your remarks and pose your questions about all racing series, except Formula One. Both technical and other questions about GP2, Touring cars, IRL, LMS, ...
machin wrote:No doubt there is of course some point where there is a flip where one design starts outweigh the other...

So the question is: which side of the switch-over point does the le Mans circuit lie?

Why do you think you can´t get all three wheels to the working point? That they become unused potential with a trike design... Is there any law for that?
In my sim model this isn´t the case (better said, i can´t see this). But as I said, we are far away from really understanding how to setup the car.
P.S.

Joined: 23 Oct 2011
Location: Germany

P.S. wrote:
machin wrote:No doubt there is of course some point where there is a flip where one design starts outweigh the other...

So the question is: which side of the switch-over point does the le Mans circuit lie?

Why do you think you can´t get all three wheels to the working point? That they become unused potential with a trike design... Is there any law for that?
In my sim model this isn´t the case (better said, i can´t see this). But as I said, we are far away from really understanding how to setup the car.

You can changing the rules to favour the odd design. Given the same dimensional restrictions the delta wing will be aways in disadvantage.
rjsa

Joined: 2 Mar 2007

P.S. wrote:Why do you think you can´t get all three wheels to the working point? That they become unused potential with a trike design... Is there any law for that?

As the RE article I quoted before says; Its all about load transfer; the problem is that a Delta or Trike shaped vehicle has a small "support base" in the combined braking/turning scenario. A small "support base" for a given mass, cg height and acceleration means more load transfer... more load transfer means that the tyres are not loaded equally and that means they're not used as efficiently...

The image below shows what I mean; notice the blue line is longer for the rectangular car (this dimension is equivalent to the track width dimension when calculating pure lateral load transfer, but in this case its a combination of longitudinal and lateral).

Last edited by machin on Thu Mar 08, 2012 11:22 pm, edited 2 times in total.
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machin

Joined: 25 Nov 2008

machin wrote:... more load transfer means that the tyres are not loaded equally and that means they're not used as efficiently...

Okay, I think I got it! Thanks for the fine drawing.
But when you talking about load transfer, I see that at the deltawing the front-tires are almost free of load transfer - in case of braking/turning scenario!?
Of course I see the higher load transfer at the rear => disadvantage.
So you haven´t conviced me with this higher mechanical grip level argument.

And you are saying "for a given mass". Thats not fair

To be more accurate with your picture, I think you have to upgrade it to 3D. And then you need an estimation on the tire size. Then we know how balanced or unbalanced the tire loads are (neglecting the camber).
This becomes all very complicated to me and I´m not able to cope... And if I don´t understand, you can not convince me
P.S.

Joined: 23 Oct 2011
Location: Germany

P.S. wrote:I see that at the deltawing the front-tires are almost free of load transfer - in case of braking/turning scenario!?

In the lateral case the fronts will be subjected to little load transfer as you say... but in longitudinal and any combination of longitudinal and lateral there will be load transfer to the fronts.... the load total transfer is simply a function of the "support base" width, the cg height, the mass and the acceleration involved.

E.g, if two cars have the same wheelbase, mass, and cg height then for a given pure longitudinal acceleration/deceleration the load transfer is the same (the track width doesn't matter here)...

In a combination of longitudinal/lateral accelertion then its that blue line distance I've marked which is used to calculate the total load transfer, as opposed to just the wheelbase (pure longitudinal) or track width (pure lateral) -because the acceleration force is acting at an angle.

Its this narrow "Support base width" in the combined longitudinal/lateral case that hurts three-wheelers so much.....

And you are saying "for a given mass". Thats not fair

Last edited by machin on Thu Mar 08, 2012 10:00 pm, edited 1 time in total.
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machin

Joined: 25 Nov 2008

An extreme example in operation (Deltawing won't roll over, but it will be affected by the same forces and the same lack of support base width in the combined long/lat accerlation case -i.e. braking and turning in)

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machin

Joined: 25 Nov 2008

machin wrote:An extreme example in operation (Deltawing won't roll over, but it will be affected by the same forces and the same lack of support base width in the combined long/lat accerlation case -i.e. braking and turning in)

robin is a front engine car on single front wheel....
Scania

Joined: 26 Nov 2008

machin wrote:1. more load transfer means that the tyres are not loaded equally and that means they're not used as efficiently...

2. In the lateral case the fronts will be subjected to little load transfer ...

Is it just me, or do you see also that this doesn´t match together?

To be honest this becomes too much hypothetic to me. Maybe we have to conclude, we are believing in different things
P.S.

Joined: 23 Oct 2011
Location: Germany

I'm talking about load transfer when the car undertakes some sort of maneuver:

in a pure lateral acceleration (no increase or decrease of vehicle speed) there is very little load transfer at the front -its mainly across the rears.

in a pure longitudinal acceleration all the load transfer is from the rears to the fronts.

in a combined long and lat case the load transfer comes off the rear inside wheel and over to the two fronts and some to the outside rear. Its this case I'm talking about.

Scania, I did say it was an extreme example

yes, the c of g on a robin reliant is further forward and yes the Delta wing has a small track width at the front, but look at my diagram above... the Deltawing layout is still closer to a robin reliant layout than it is a rectangular layout.... it will have less overturning resistance in the combined long/lat case simply by virtue of its smaller base width in this case (blue line length).... less overturning resistance means more load transfer and that is what all circuit racers are trying to avoid when they try everything they can to reduce CG height....
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machin

Joined: 25 Nov 2008

machin wrote:.... less overturning resistance means more load transfer ....
Really?

I think you should not ignore my hint. You can not neglecting that.

I made a rough account based on your drawing, but with a trike, to get it more clear.
I tried to calculate the load difference for each wheel with just 1G lateral acceleration (same CG hight (1meter)). I came up with:

Trike: Front =0%, RearLeft +90%, RearRight, -|90|% => Average is 60% loaddif.
Rectangular: FL=70%, RL=70%, FR=-|70|%, RR=-|70|% => Average is 70% loaddif.

I´m not saying I know it all. But I think you have done it too easy with your estimation.
P.S.

Joined: 23 Oct 2011
Location: Germany

that's the pure lateral case... not the combined lateral-longitudinal case that I'm talking about.....???

In any case, we get different results even for the pure lateral case... here are my calcs... maybe you could check them and look for a mistake?:- (the track width is taken as 2m in each case, and cg height as 0.5m)

Essentially because the weight, track width and cg height are the same the load transfer is the same, but because all the load transfer on the Trike is across the rear then the % increase per wheel is higher than the rectangular car where the load increase is shared across the front and rear..... Or can you spot a mistake
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machin

Joined: 25 Nov 2008

so they said there are no stress on the chassic during turning
Scania

Joined: 26 Nov 2008

Scania wrote:so they said there are no stress on the chassic during turning

Can u explain a bit more?
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machin

Joined: 25 Nov 2008

Again, thanks for the drawings. Really nice!

You calculated it in a different way than I did. But in fact you came to the very same values in proportion. And I have to say that my average tire load calculation is a bit crap because I assumed the same basic load for each. But I want to show that we comparing apples with oranges.

And then I say we are just talking on a very small bit. Aero and weight... a huge huge topic where it is absolutly hopeless to say: "It is that way".

So I´m tired of trying too find "hot or not" arguments. I just have the feeling that the deltawing has its potential.

Cheers
P.S.

Joined: 23 Oct 2011
Location: Germany

fair enough.... and I do agree the Delta shape does have its place; on the right track (with a lack of corners) I agree it has more potential than a rectangular car....

Oooo, for anyone else following this thread (because I didn't explain this above) its the fact that the Trike/Delta shape sees a bigger increase in load on its outside rear than the rectangular car (66% vs 50%) that suggests that, all else being equal, this layout will fundamentally exhibit more oversteer than the rectangular car, and therefore a lower cornering capability.
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