Delta wing car concept

[P.S.]

I don't think you're going to necessarily get any remotely realistic results from trying to simulate this thing in rFactor.

Do you have any idea how rFactor is working? Its a serious question! Because it is builded up from basic automotive physiks. For example CarMaker is based on the same stuff. And that programm is specific made for car developement.

[Jersey Tom]

Yes, I am familiar with the workings of rFactor.

Here's the biggest thing: the tire model isn't at all relevant. Huge amount of the handling of that vehicle topology is going to be a function of tire load and sideslip sensitivities, which are not going to be appropriately captured.

That and aero, and none of us have an aero map for the thing.

[countersteer]

It is of course very different to a usual car, so you can not work with spring rate and stabilisators like you did learn in the past.

This got me to thinking... Just exactly how do you tune the chassis on this thing? Especially during a long stint. Even on an oval, Indy cars have weight jackers and adjustable roll bars that the drivers are constantly playing with, even during the course of a single lap during qualifying.

For the sake of argument... Let's say I take the car and put it on a big skid pad. Let's say I get it perfect from the start. The car goes out and hits the limit perfectly. No understeer, no oversteer. After a bit, the tires start to degrade, or the drop in fuel load shifts the COG. Or... you change the diameter of the skid pad and the aero pressure point moves.

How do you change it to compensate? Bowlby has stated that it really won't transfer roll stiffness front to rear so we can't play with anti-roll bars to speak of.

To compensate for an oversteering car, we would normally transfer roll stiffness to the front, but the effect in this context would be minimal and, it appears to me would only unload the inside front tire and degrade the outside front tire quickly. And if it oversteers and you have zero roll stiffness at the front, then what do you do? A change to the roll stiffness at the rear would have no effect.

Is this what the article in Racecar Engineering was referring to?

And this is in a steady state condition. How do you set this thing up for for the variety of corners and speeds it will see at LeMans? It would appear that this thing would have a very very narrow window of balance and would be an absolute beast to drive.

I'm a big fan of the concept, but I can't get past this.

I know a LOT of you guys have a lot better understanding of this than I. I look forward to the commentary.

Regards...

[Lurk]

does it got LMP1 performance & safety standed?

No idea for safety and between GT1 and GT2 concerning performance...

[P.S.]

Yes, I am familiar with the workings of rFactor.

Here's the biggest thing: the tire model isn't at all relevant. Huge amount of the handling of that vehicle topology is going to be a function of tire load and sideslip sensitivities, which are not going to be appropriately captured.

That and aero, and none of us have an aero map for the thing.

Here I think different.
To get the basic understanding of what is the difference between a usual race car with four wheels and the deltawing (or a trike), the tire model in rFactor is more than enough. But it is up to the user, to interpret the results. I am very satisfied with it.

According to the deltawing homepage, most important data for the aero identification were already given. Balance is around 80% to the rear, thats btw very usual to put the centre of downforce slightly back shifted to the centre of gravity. C_d round about 0,24 and lift/drag about 5. Especially L/D is pretty high and one of the reasons why the deltawing should have such a performance.The variations to all this data caused by groundeffect is much more complicated. But here you can take an approach with data from other groundeffect cars. Even the lift/yaw angle forces can be taken from aeronautic books (if you have access to those) because there are some basic rules for them. Here too, this I think was absolutely adequate to what I am looking for.

But I´m not writing here to convince anybody that the deltawing is awesome. I´m just loving this out of the box design. And I tried to analyze it...

[Jersey Tom]

Yes, I am familiar with the workings of rFactor.

Here's the biggest thing: the tire model isn't at all relevant. Huge amount of the handling of that vehicle topology is going to be a function of tire load and sideslip sensitivities, which are not going to be appropriately captured.

That and aero, and none of us have an aero map for the thing.

Here I think different.
To get the basic understanding of what is the difference between a usual race car with four wheels and the deltawing (or a trike), the tire model in rFactor is more than enough.

And what is the basis for this belief?

[machin]

To get the basic understanding of what is the difference between a usual race car with four wheels and the deltawing (or a trike), the tire model in rFactor is more than enough. But it is up to the user, to interpret the results. I am very satisfied with it.

P.S, I'm totally with you on this one; in the 10 years since I left Uni I have been developing my own simulation software to predict car lap times for the main reason of deciding what modifications I should make to my own competition car, and also to try and improve my performance by understanding how fast the car should go if driven correctly (so a driver aid really).

In that time I've recorded data from many different types of cars, driven by myself and my competitors... from road-going sportscars to purpose built racecars... and do you know what I have found? When considering professionally designed and built cars you can make a very accurate prediction of its performance just by knowing the fundamentals; mass, track widths, wheelbase, tyre sizes, cg position, power curve, gear ratios, rotating inertia etc. I'm talking lap time predictions which compare to the real cars within 2 or 3%. What I'm saying is that it becomes clear that there is a performance limit which is determined by the fundamentals -the better designed, set-up and driven the car is the closer it gets to the limit determined by those fundamentals. Of course, if the car hasn't been designed by a professional, isn't set-up properly and/or isn't driven by an experienced driver then the performance doesn't match the predictions... as you would expect.

We know of course that the Deltawing has been designed by a professional team. We know it will be set-up by a professional team, and we know that it will be driven by professional drivers... so that means I think, as you P.S do, that it is possible to predict with a high enough level of accuracy the relative benefits of the Deltawing versus a regular car, just by considering the fundamentals of those designs.

My own predictions using the fundamental data provided by the Deltawing press releases concur that it should meet its 3:45 target Le Mans lap time. I don't believe it'll be a failure. What I believe is that a rectangular car, given equal performance breaks such as the lower weight and ground effects tunnels would be quicker - not a lot quicker, but sufficiently quicker that in an equal fight the Deltawing would soon become just a curious footnote in history.

[Tim.Wright]

As a number of people have alluded to before, you can account for different mass distributions by adjusting the tyres sizes front rear to have more or less (theoretically) whatever balance you want. The delta wing obviously is taking this to the extreme with a massive rear mass disribution. It could theoretically be made to work with very very special tyres, and they do have at least custom tyres from Michelin.

so any simulation is going to need a pretty special tyre model for these pretty special tyres. I think R factor is going to really let you down there.

Tim

[Jersey Tom]

When considering professionally designed and built cars you can make a very accurate prediction of its performance just by knowing the fundamentals; mass, track widths, wheelbase, tyre sizes, cg position, power curve, gear ratios, rotating inertia etc. I'm talking lap time predictions which compare to the real cars within 2 or 3%.

Erm, sorry, but going to have to throw the BS flag out on this one here. I've seen on professionally prepared and driven cars, a tire tread formulation change drop lap times by 5%+. That's already outside of the 2-3% claim. Hell, with a full ADAMS model and $100,000 worth of tire data you could be off 5% or more in absolute lap times. There can be a change in lap times on the order you're speaking just based on ambient weather conditions, or how the track changes over several hours.

Now sure, you may have a few cases where by pure chance your predictions are within that margin with no a priori knowledge of things. I'd say that's the rare exception rather than the rule.

All that said, lap times are another. Predicting handling is an entirely different story. I will say right now that there's no way in hell you're going to come close to even guessing the initial turn-in of the thing without having ballpark figures for the front and rear cornering coefficients. That's simple undergrad-level vehicle dynamics.

So no, rFactor is not going to cut it for cobbling some crap together and saying you have a good feel for how it's going to drive.

[Kittredge305]

DeltaWing to race at Le Mans 24h 2012

[Pierce89]

Everybody here is worried about the car understeering, but in Racecar Engineering, a vehicle dynamics engineer(don't remember the name) was more worried about the fact that VIRTUALLY all of the roll resistance having to come from the rear, and the oversteer that could result. An oversteer tendency could be quite sketchy in a car with a rear weight dist. of 72.5%. That's a whole lot of rear mass to conrol in a car that might already have an oversteering tendency.

[P.S.]

My own predictions using the fundamental data provided by the Deltawing press releases concur that it should meet its 3:45 target Le Mans lap time. I don't believe it'll be a failure. What I believe is that a rectangular car, given equal performance breaks such as the lower weight and ground effects tunnels would be quicker - not a lot quicker, but sufficiently quicker that in an equal fight the Deltawing would soon become just a curious footnote in history.

Hey machin, thanks for your detailed conclusen. Here we come together
I don´t have any race car experience like you have and my basic understanding of simulations are learnt while simulating aircrafts, or beeing involved in such projects. But it is all quite similar, expect from the tire stuff. Last year I was my first times on a racetrack (passenger, Nordschleife). I became addicted...

You believe that a rectangular car will bring not less the performance than the deltawing... But I do. You are saying a car with same power/weight, lift/drag, etc. will bring better performance. No veto from me. But I believe the deltawing design will always being lighter in comparison. And better aero performance too. Every additional wheel on the street is a massive pain for fluid, I just had to discover again while optimizing my first underbody.
So there is nothing to argue about, we coming down to just feelings.

[FW17]

Everybody here is worried about the car understeering, but in Racecar Engineering, a vehicle dynamics engineer(don't remember the name) was more worried about the fact that VIRTUALLY all of the roll resistance having to come from the rear, and the oversteer that could result. An oversteer tendency could be quite sketchy in a car with a rear weight dist. of 72.5%. That's a whole lot of rear mass to conrol in a car that might already have an oversteering tendency.

The test driver mentioned that the car oversteered during the run.

Cant wait for their run on 17 March

[Jersey Tom]

Everybody here is worried about the car understeering, but in Racecar Engineering, a vehicle dynamics engineer(don't remember the name) was more worried about the fact that VIRTUALLY all of the roll resistance having to come from the rear, and the oversteer that could result.

I think you'll find that this has been brought up a couple times in the thread, and yes - it is a valid concern... as is the rear axle load distribution on corner exit and L/R drive torque biasing.

Ordinarily if you had a car topology like that, it would oversteer all over the place. Given the immense difference in tires, it's really hard to say though. Really goes back to my previous feeling of - they've over complicated this. Why add extra challenge rather than just finding a good, easily workable solution?

[machin]

I believe the deltawing design will always being lighter in comparison. And better aero performance too. Every additional wheel on the street is a massive pain for fluid, I just had to discover again while optimizing my first underbody.

No doubt there is of course some point where there is a flip where one design starts outweigh the other...

For a purely straight line acceleration run a delta-shaped car is going to be better (I'm thinking dragsters, Thrust SSC etc as good examples of this), but at the opposite end of the scale there's cars that are designed for getting round tight and twisty corners (wide-arch rally cars and go-karts come to mind here). I agree there is a natural weight advantage of the Delta-wing layout, although personally I think its small, and this will of course skew the switch over point between whether Delta or Rectangular will give the faster lap times for a given course in favour of the Delta shape -slightly!

So the question is: which side of the switch-over point does the le Mans circuit lie? Personally I think it's on the side of the rectangular car, but as I say- not a significant advantage, but sufficient that the best solution for Le Mans is rectangular.

For a banked oval Circuit? I suspect it might just be in favour of the Delta layout (I'm not interested in Oval racing, so I've never simulated it), its an interesting proposal.