Delta wing car concept

[machin]

JT... Sprung mass would not have a constant roll angle displacement if u change track width though would it?

Fundamentally to work out force transfer you take moments about the inside wheel; mass x gravity x cg height x g.force = track width x force transfer. If it didn't the car would roll over. This is true whether the car has suspension or not.

If cg height, g.force, gravity and mass stay constant, but track width is increased the force has to come down, otherwise the car would roll over INTO the corner wouldn't it?!

If we put numbers to the problem we can see the effect on roll angle;

If the overturning moment were 3000Nm (500kg, 0.3m C.g height, 2g ish cornering), and track width 2m then the force transfer is 1500N. If wheel rate were 50N/mm, then the outside wheel would displace 'up' 30mm and the inside 'down' by 30mm. Using simple trig we use inv.tan (0.06/2metres) and find roll angle is 1.7degrees.

If we now double the track width we half the force transfer (see my first equation). If wheel rate is the same then each wheel displaces vertically by 15mm. Inv.tan(0.03/4metres) = 0.4degrees.

So you can see, roll wouldn't stay the same...

[Jersey Tom]

The average track width isn't what I'm getting at.. it is the relative width of the rear and front, and the effect that has on load transfer distribution.

The front and rear end of the car will not be at different roll angles relative to each other - any chassis compliance out of the picture. That being the case, you can work through and see that the load transfer carried by the outside front and outside rear tires is not identical, as you had worked out previously.

[machin]

JT, I think u missed something;

lets keep all things equal

I don't think you have equal roll resistance in your stated case do you? If the roll resistance were equal then the same roll angle front and rear would mean the same force transfer wouldn't it?

And that's my point... You can play with other parameters such as anti rollbars to get either understeer or oversteer... Whether the front track is equal or half the width doesn't matter... (A tricycle is a different case because you can't have any roll resistance at the single wheel end).

[Jersey Tom]

You said equal spring (wheel rate) stiffness earlier.. I worked on that premise.

[machin]

Was it me or you who specifically said "wheel rate" first?

Either way, I now see that its wrong to assume that... its fairly safe to assume that the team will optimise the rollbars to achieve the best load transfer distribution, don't you think?

And that leads me back to my original statement:-

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 which way it'll go

i.e. you need to make assumptions or know the specifications of the other parts to know whether it'll understeer or oversteer.

Either way, we've got side-tracked a bit; we're both in agreement with the fundamental disadvantage of the Deltawing -a lower average track means a higher total force transfer, and that's bad.

[machin]

JT, I think I see where you're coming from:-

If we start with a rectangular car and reduce the front track width, then in order to maintain the balance, then, as you've inferred, you’re going to need to increase the front anti-rollbar stiffness (assuming the rear bar was already set as soft as practicable to achieve good camber control)… but doing that is going to mean that the front wheels are less able to absorb a single wheel bump, i.e generate less grip when subjected to single wheel bumps which the front wheels encounter...

Would you agree therefore we could summarise the “real world” Deltawing options as:-

1, Equal single wheel ride stiffness as a rectangular car, but oversteer (your point)
2, Balanced handling, but reduced single wheel bump control compared to a rectangular car (kind of my point, although I didn't realise/highlight the downside before)

(all else being equal)? Either way the Deltawing has to make some compromise compared to a rectangular car... and that's why a rectangular car, if allowed the same ground effects and light weight, would be better.....

[GSpeedR]

machin, keep in mind that roll stiffness is proportional to track width squared (tw^2), while load transfer across an axle is inversely proportional to track width (to the 1st power).

The basic premise is (in terms of displacements):

K_roll = Moment / Roll [Nm/deg]

Moment = (tw/2)*(F_out - F_in) [Nm]

Roll = invtan((d_out - d_in)/tw) [deg]; where d_out is outside wheel displacement

For smallish angles, you can remove the invtan; if not then solve with a simulation.

Load transfer distribution will depend on the relative ratio of your roll stiffnesses; a smaller track width will result in a lower roll stiffness, and thus less of the overall roll moment is reacted by that axle. It is true that a smaller span (track width) results in more load transfer for an axle for a given roll moment, but this effect is overpowered by the fact that less roll moment is reacted (t^2 versus t). It seems that you saw this in your simulated comparison a couple pages ago: you lessened front track width and saw more load transfer on the rear tires.

In fact, you will not correctly determine the total vehicle load transfer using average track width...it is proportional to the average square track width ratio, (tw_f^2 + tw_r^2)/(2*tw_avg).

[GSpeedR]

It looks like everybody has come to an agreement on front and rear roll angles, but things can get a little confusing if we use ground fixed inertial axes. However, for body-fixed axes, a rigid sprung mass must absolutely have equal front and rear roll angles; there is only one roll angle. That's a necessity of rigid body analysis: there's no internal relative motion, meaning displacements and angles are universal for that body.

I've found a lot of engineers will neglect to include tire deflection when calculating roll angles, which results in a chassis with a lot of virtual "twist". This happens at the track with suspension potentiometers which measure body-hub displacement as well.

[bill shoe]

http://auto-racing.speedtv.com/article/ ... -issues/P1

This is frustrating. The 2012 Indycar has almost no legacy parts. The chassis, engine, transmission, etc. are all clean-sheet-of-paper parts. And the car, on a basic level, is too ass-heavy. And also too heavy overall.

This car was spec'd by a relatively non-technical committee which then gave the design specs (wish list?) to--> Dallara (chassis), Chevy/Honda/Judd (engine), and Xtrac (transmission). It seems there was no clear responsibility or authority for fundamental design attributes such as weight or weight distribution.

Another way to look at this situation is that IndyCar will have the Delta Wing weight distribution, but not the Delta Wing f/r tire distribution.

This also makes F1 organizations like Red Bull look more impressive for their ability to coordinate large numbers of people to achieve effective overall designs.

[Jersey Tom]

So the car isn’t going as fast as we wanted or expected and we’re trying to identify why the theoretical world doesn’t match real world at the race track.

The theoretical world doesn't match reality?! What a shocker!!

[cossie]

http://auto-racing.speedtv.com/article/ ... -issues/P1

This is frustrating. The 2012 Indycar has almost no legacy parts. The chassis, engine, transmission, etc. are all clean-sheet-of-paper parts. And the car, on a basic level, is too ass-heavy. And also too heavy overall.

This car was spec'd by a relatively non-technical committee which then gave the design specs (wish list?) to--> Dallara (chassis), Chevy/Honda/Judd (engine), and Xtrac (transmission). It seems there was no clear responsibility or authority for fundamental design attributes such as weight or weight distribution.

Another way to look at this situation is that IndyCar will have the Delta Wing weight distribution, but not the Delta Wing f/r tire distribution.

This also makes F1 organizations like Red Bull look more impressive for their ability to coordinate large numbers of people to achieve effective overall designs.

this is how screwed up the Moronic( Iconic) committe was , All daqllarra did was propoase a buisness plan, Lola Swift and BAT proposed a chassis paln and now they wonder why they are having problems

from Speed Robin Miller

It was way too cold to do any running Thursday at the Indianapolis Motor Speedway but Tony Kanaan still spent a few hours driving the new Indy car at the world’s most famous race track.

Of course TK was at the Dallara factory in Italy on the IndyCar simulator – trying to help the longtime manufacturer work out some problems with the DW12 chassis.

The immediate concern is the disappointing performance of the Dallara at the Speedway last week, where Dario Franchitti and Kanaan tested for two days.

And, while the top speeds were only between 208-216 mph for either the Honda or Chevy-powered drivers, it was more a product of the car’s handling than a question of power.

“The focus of concern is with weight distribution,” said Will Phillips, vice president of technology for the IZOD IndyCar Series and the midwife of the first new car in a decade for this series.

“The car is too good on entry and suffers understeer on [corner] exit and it’s the same complaint from Dario and Tony that Dan [Wheldon] gave us after the first test.

“So the car isn’t going as fast as we wanted or expected and we’re trying to identify why the theoretical world doesn’t match real world at the race track. At very high speeds, we have disparity in the data.”

[aleks_ader]

[youtube]http://www.youtube.com/watch?v=F2fRI6p8 ... r_embedded[/youtube]

Nice pic gallery:More pic on this link:

http://www.highcroftracing.com/gallerie ... g-assault/

[Scania]

Can u expand on the question a bit?

If you mean, will the "wingcar" have worse aerodynamics than Deltawing.. my thoughts are that it wouldn't... The picture below shows a comparison on the left of the profiles of the two cars....

Black near the centre of the car
Red in line with the rear wheels
Blue between those

The comparison on the right shows a section through the two cars at the centreline of the rear wheels (in dark grey), and the front tyres projected on that (in light grey). On the Deltawing the wide rear tyres create more blockage of the flow and the front tyres disturb some of the flow in the ground effect area...

On a rectangular car with narrower rear tyres the blockage is a lot less, and also I would guess the flow is cleaner as the front tyres don't get in the way...



To my mind, I would guess that the lower blockage caused by the narrower rear tyres, the fact that the rear tyres are in the wake of the front tyres and the extra length of the "between wheel" region (blue in profile view) on the Wingcar would mean that it has lower form drag, but, due to the larger plan form area, also a slightly higher skin friction drag.... adding up (only guessing here) to (slightly) lower overall drag than the Deltawing....

Both shapes are quite simple, so I'd be interested if anyone could make some simple models and do some cfd?

I had re-read your "Wingcar" concept, I still don't think it is better then DW

ya, If you can have same weight, same downforce, same drag, it will be a same thing with Deltawing, but:

yes, bigger diffuser will get more downforce, however, a rectangler close wheel car means more area on the upper side, it means more lift force.
More lift force + more down force = nothing but more drag.

and then, we know we are making a ground effect car, a huge floor area means it will get enough area to let turbulence go under the floor when you following the other and easy to fly the car.

[machin]

What we need is someone who can do some cfd on the two simple shapes... I've given my reasons why I think a rectangular car is better... but some cfd would lay the matter to rest.

The biggest downside to the Delta wing is of course the inherent disadvantages of a delta shaped car compared to a rectangular shaped car in terms of cornering capability. I believe that the only way a Delta wing can be competitive is if the rectangular cars are hampered by, for example, a much higher weight.... oooo, like the case will be at Le Mans this year!

If the Deltawing is so good I implore the team behind it to compete in the british sprint championship where both types of cars could compete without unfair advantages given one way or the other, just a nice open rule book.....

[cossie]

http://auto-racing.speedtv.com/article/ ... -issues/P1

This is frustrating. The 2012 Indycar has almost no legacy parts. The chassis, engine, transmission, etc. are all clean-sheet-of-paper parts. And the car, on a basic level, is too ass-heavy. And also too heavy overall.

This car was spec'd by a relatively non-technical committee which then gave the design specs (wish list?) to--> Dallara (chassis), Chevy/Honda/Judd (engine), and Xtrac (transmission). It seems there was no clear responsibility or authority for fundamental design attributes such as weight or weight distribution.

Another way to look at this situation is that IndyCar will have the Delta Wing weight distribution, but not the Delta Wing f/r tire distribution.

This also makes F1 organizations like Red Bull look more impressive for their ability to coordinate large numbers of people to achieve effective overall designs.

You can thank FTG, the great Brian Barnhart for this cluster f### IMS and moronic commitee. AOW is circling the drain and ready to be flushed down a toliet [-o< [-o<