Time Attack

[miqi23]

In terms of downforce generation on their own, absolutely. How about with regards to conditioning the wake? I'm not even saying it works in every case, as the wheelwell and bodywork for each car is not the same. But to blindly say that it is frivolous and cannot work, when there are several very successful championship winning/contending cars employing it, is fairly amusing.

From the conditioning the wake point of view, I agree with you - may be previous posters thought you were talking about the object behind the wheel working on its own right, that is what I perceived as well. Yes, you can get benefits from having stuff behind a rotating wheel if done right.

[aussiegman]

Wings, foils, canards etc behind a rotating wheel perform three basic tasks:
1: flow conditioning
2: directing flow &
3: downforce generation (either from he element itself or by increasing flow to other elements)

We had extra elements in the front and rear guards and it certainly seemed to straighten up the flow however it gave us some other unexpected effects we didn't like so we took them out (especially in the rear).

We have some more CFD and experimenting to do, however in the front guards straightening the flow and directing it to the desire area for the most benefit is not as simple as you'd think. If we even do a rear mounted radiator then we know exactly how to get max flow to that area of the rear quarter panels!!

In the rear, it upset the aero balance by giving more rear downforce which lifted the front. I expect some of that is simply aero load on the shaped elements and more effective streamlining of the rear flow that drove the diffuser harder. Until we get more front / centre downforce we don't need more rear pressure and the wing has already been lowered and angle changed to reduce drag and downforce.

[MadMatt]

I never denied the use of wings behind rear wheels, what has to be seen is the picture I posted which clearly showed a concept that would never work in our world. Funny how people read what they want, heh! Funny also how I used wings behind a Pikes Peak car that I designed and CFD tested (see early entries in my blog, link in my signature), but yet I fail to see the meaning of that aero device.

And again, saying that because McLaren or whatever put it on the car doesn't mean it will win/work/is the way to follow. EVERY TEAM made/makes mistakes, and what works on a car (or engineers think it works), might not work on another, or not work at all. Judging something because someone put it on the car with a polished badge on it WILL NOT MAKE IT WORK. We are engineers, not artists (I feel like I am repeating myself).

While I agree that some winglets on the side of a tapering rear end will help produce a bit of downforce (who wouldn't?), the aim is more likely to help filling the wake behind the car.

Look at this Osella FA30 hillclimb machine (I am following hillclimb far longer than I can remember):





There you see an efficient way of using them. The back is tapering very much to allow for the winglets to be used. But you will never see any wing behind the wheel as the picture I posted (which is dead now).

[aussiegman]

Hey Matt, I was actually agreeing with you that flow conditioning and wake management is primarily the use...

[MadMatt]

Hey Matt, I was actually agreeing with you that flow conditioning and wake management is primarily the use...

I know, I was more posting this for my friend that unlike his name, is diverging with what I'm saying.

[wesley123]

Tilton posted a new image of their Evo for this year. Looks even more crazy than before.

[NoDivergence]

Don't see how the example of that Astra is so divergent from the other examples posted here. Care to explain? Like has been said before, every car is different, how are you so sure that it doesn't work for that car?

And yes, for the Tilton, more is better. As is seen in the new setup shown above.

As you have neglected to note prior, the teams that you are putting down have DATALOGGED the heck out of their aero components. They have already been proven to work on the track.

[MadMatt]

I'm surprised that after lots of useless and ridiculous posts, NoDivergence didn't care to say who won this year's World time attack challenge.

[wesley123]

I personally didn't think it needed to be said who would win.

Interestingly enough, this will be the last win for Tilton's Evo as they'll move on to something different in, what I believe was said, 24 months

[Cold Fussion]

How much faster can time attack realistically go? They're already pushing 1000+ hp with huge amounts of aero while being 7-8 seconds faster then a v8 supercar. The Tilton car looks like a handful from the onboards and they are probably rapidly approaching the limit of how much grip they can generate without a slick tyre.



Looking at the speedo the car appears to have quite a lot of drag (look at how slowly it accelerates from 250 onwards, it doesn't sound like it's gearing limited), so advancements in the coming years could venture towards aero efficiency?

[VerleneDP]

Very impressive! Great Work. thanks for your great sharing

[MadMatt]

From the onboard shot we could do an estimation of the G-forces in few of the corners if someone's got the corner radii?

[MadMatt]

I'm abroad so haven't got access to some proper tools, but I did a quick calculation:

Radius of the first corner 166.5m. Speed at apex 225km/h. This gives a lateral acceleration of 2.4g, interesting! As Cold Fussion said, the drag is immense but the downforce is quite significant, and they have the engine power to go fast anyway so they don't care that much.

If we assume car weight is 1150Kg it gives a lateral force of 27kN. Then its a matter of estimating the friction coefficient of the tyres to get the downforce needed to get around that corner at that speed. I've done calculations using few different coefficient numbers:

- 1: 27kN
- 1.25: 21.6kN
- 1.5: 18kN
- 2: 13.5kN

They have to use Advan A050 tyres in soft or medium, so the argument that they are not on slicks is not really true, since these tyres are really really soft and sticky!

I would say the friction coefficient is in the region of 1.5, so that's roughly about 20kN of downforce.

Now if we take a wetted area of 8.65m^2 (7.8m^2 for factory Evo) and a speed of 225km/h, with 20kN of force, it gives me a CL of 0.97!

Hard to calculate the drag from the data we have, but obviously it will be in the region of 0.5 probably, which gives a L/D ratio of around 2, which is good!

Again these are rough calculations done on my laptop while on holiday so pardon me if I am not 100% precise, feel free to comment and argue!

[wesley123]

A great article on the RP Porsche 968 that ran in this years WTAC, probably more extreme than the Scorch S15 and Evo's that dominated WTAC the past few years.

http://www.worldtimeattack.com/index.ph ... 8-porsche/

[Facts Only]

They have to use Advan A050 tyres in soft or medium, so the argument that they are not on slicks is not really true, since these tyres are really really soft and stick!

Those Advans aren't a patch on proper slicks, I've driven on the Advans and proper Michelin S310 slicks and the Advans were much closer to road tyres than the slicks.