Rule Interpretation - Double deck diffusers

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SpookTheHamster
0
Joined: 26 Aug 2005, 12:27

Re: Rule Interpretation - Double deck diffusers

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There are no loopholes, only loopslots.

wesley123
204
Joined: 23 Feb 2008, 17:55

Re: Rule Interpretation - Double deck diffusers

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Why dontt he teams make the DDD's full with? with a second plane over the full lenght
"Bite my shiny metal ass" - Bender

feni_remmen
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Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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The reference plane is the bottom part of the car that all the measurements are referenced off. In the old days, this was done off the ground. The step plane sits 50mm (5cm) above this. If there is a step plane immediately above (vertically) the reference plane you have to have a solid panel between these planes... But, if for some reason the step plane isn't needed there (like a wishbone is the next visible thing when looking from below then it seems you don't need to have a solid body in this vertical transition... (this make some sense as it has nothing to attach to (as the step plane is gone!).

I may have this wrong as I've not paid too much attention to this, but this is what i think is happening.

feni_remmen
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Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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wesley123 wrote:Why dontt he teams make the DDD's full with? with a second plane over the full lenght

It is important to recognise why they are interested in these extra layers. The second and third layers allow them to process the extra air drawn from under the car. Multi layers are useful on their own, but they would have too much drag. The diffuser is powerful because it is working with ground to produce the low pressure area below the car. The second layer, if it is taking clean air from above the step plane would be transfering its pressure between the wheels and while it would have an effect, it would be drag intensive for the gain. A good equivilant of this solution is the concept of having a flat bottom covering (from underneath) a full ground effects undertray. In this case it doesn't produce a more effective low pressure area under the car. It causes a pressure difference above the step, on insde the car, which just produces drag...

feni_remmen
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Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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kNt wrote:if you have an unsprung part below the step planeholes above it are permitted.

Are there any regulations restricting unsprung parts of the cars to some area?

If not, one could get rid of the step plane alltogether, fit a large wishbone with sideskirts to the reference plane and the rear wheel (or even to the frontwheel ?) and effectively have a lotus double-floor car. It can't have a wingprofile incorporated but that can be dealt with the diffuser.

I mean I always thought since double-floor cars are illegal also suspension parts below the step plane are illegal. But now it appear such unsprung parts are used to hide the holes in the floor that feed the double-deckers.
The wishbone needs to be above the step plane from an engineering perspective. It is not practical or useful down that low (in the 50mm between the planes). The loophole is that if the sprung part of the car is allowed to be visible from below. (for example if you can see inside of the top of the car from bolow the car, you need to have one of the two planes hiding it from view... But if you see the wishbone below then that means you can't see what may be above it... So the diffuser area forward of the axle line (or the top of the car or anything else in there) may be "invisible"!

feni_remmen
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Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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Guys,
I've got a graphic showing an undertray. I've no idea how to insert it into the forum. Thought i was smarter than this...

Anyway, it shows the planes and how they relate to each other. Roughly where the slots are. I did this to try to show the two planes and where you would draw some of the air through.

Any tips on posting graphics would be great...

Thanks,
feni.

Giblet
5
Joined: 19 Mar 2007, 01:47
Location: Canada

Re: Rule Interpretation - Double deck diffusers

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You need to set up an account with an image hosting service, and post the links to those images using the Img button above the message editing window

Imageshack is a free limited hosting service. Allows 7 shots for free I think.
Before I do anything I ask myself “Would an idiot do that?” And if the answer is yes, I do not do that thing. - Dwight Schrute

feni_remmen
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Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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timbo wrote:
feni_remmen wrote: If this hole is ahead of the axle line, it does really open a Pandora's box. I think the debate is about to extend to "what is an appropriate to be considered as a sprung part of the car?" I answer to the question about venting isn't a major worry as you would still need to hide the unsprung part of the car, unless it is something like the RB5 had on the weekend.
Thanks!
So it may appear as if teams would make a very wide wishbone it is possible to create a wide, forward placed hole to feed upper deck of the diffuser.
I wonder would it really drive designers to create something awkward?
Pandora box... quite may be!
Timbo,
Wishbones are reasonably regulated. They closed these down about ten years ago when some teams started thinking about full covered triangles with wingshapes... Tyrrell had some corkers back then. Rule 10.3 in the regs relates to this, but there is still some room to move. Plus there are 2 wishbones,plus driveshafts and trackrods, all should be considered "unsprung" and all can be used to hide the car from below...

feni_remmen
3
Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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Astro1 wrote:
Image

If the start of their main diffuser is the minimum rearward position at rear wheel line, and the 3rd deck of Toyota's diffuser starts before that, it seems logical the non DD teams may be annoyed.

1. First opening - seems to be part vertical and part horizontal? It looks like they are taking air out from under the floor, using the gap between the outside sidepod floor level and the central lower floor level of the tub, engine area etc. (??)
2. Second opening - again seems to be part vertical and part horizontal?
3. How is this continous!? Seems like a break in the line to me?
4. What's going on with these scultped bits of the floor?

Astro,
This is a great photo as it shows the rear leg of the lower rear wishbone and the hole it is being used to "create"! The wishbone is the CF part crossing the picture, just above the word RW centreline and the number 1. It crosses from the endplate on the left, all the way to the third diffuser chamber, then then meets the gearbox on the right. The white box extends further forward under that part. I think. I may be missing something, but that is what i see there.

feni_remmen
3
Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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Giblet wrote:You need to set up an account with an image hosting service, and post the links to those images using the Img button above the message editing window

Imageshack is a free limited hosting service. Allows 7 shots for free I think.
OK, that sounds harder than i'd hoped. I've no idea how to set up an account with an image hosting service.
Thanks.

feni_remmen
3
Joined: 26 Mar 2009, 15:43

Re: Rule Interpretation - Double deck diffusers

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feni_remmen wrote:
timbo wrote:
feni_remmen wrote: If this hole is ahead of the axle line, it does really open a Pandora's box. I think the debate is about to extend to "what is an appropriate to be considered as a sprung part of the car?" I answer to the question about venting isn't a major worry as you would still need to hide the unsprung part of the car, unless it is something like the RB5 had on the weekend.
Thanks!
So it may appear as if teams would make a very wide wishbone it is possible to create a wide, forward placed hole to feed upper deck of the diffuser.
I wonder would it really drive designers to create something awkward?
Pandora box... quite may be!
Timbo,
Wishbones are reasonably regulated. They closed these down about ten years ago when some teams started thinking about full covered triangles with wingshapes... Tyrrell had some corkers back then. Rule 10.3 in the regs relates to this, but there is still some room to move. Plus there are 2 wishbones,plus driveshafts and trackrods, all should be considered "unsprung" and all can be used to hide the car from below...
Sorry, but i am dumb. The top wishbones and driveshafts would be useless for this situation! Idiot!

Gecko
4
Joined: 05 Sep 2006, 20:40

Re: Rule Interpretation - Double deck diffusers

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feni_remmen wrote:
Astro1 wrote:
Image

If the start of their main diffuser is the minimum rearward position at rear wheel line, and the 3rd deck of Toyota's diffuser starts before that, it seems logical the non DD teams may be annoyed.

1. First opening - seems to be part vertical and part horizontal? It looks like they are taking air out from under the floor, using the gap between the outside sidepod floor level and the central lower floor level of the tub, engine area etc. (??)
2. Second opening - again seems to be part vertical and part horizontal?
3. How is this continous!? Seems like a break in the line to me?
4. What's going on with these scultped bits of the floor?

Astro,
This is a great photo as it shows the rear leg of the lower rear wishbone and the hole it is being used to "create"! The wishbone is the CF part crossing the picture, just above the word RW centreline and the number 1. It crosses from the endplate on the left, all the way to the third diffuser chamber, then then meets the gearbox on the right. The white box extends further forward under that part. I think. I may be missing something, but that is what i see there.
That is indeed a lovely picture. It shows that the team is using both loopholes in the regulations, namely the discontinuity and lack of transition that is allowed at the rear wheel centerline, which allows for the vertical opening labeled as 3 in the picture, and the loophole which allows a suspension member to form a part of the deck of the diffuser (opening 1).

That said, while the design of hole 3 looks "proper", there must be doubts as to how well the suspension member can seal the upper side of the deck, as well as how good is the quality of flow acutally with the suspension member in the channel.

I also don't think that the loophole as used to form the opening 1 in the picture necesarily requires a suspension member to be present. One could simply just open up the floor ever so barely such that there can be a horizontal gap between the reference and step planes close to the hole, which then allows for the two planes to not be joined by a transition, and then one would continue the upper deck of the diffuser above the reference plane at the level of the step plane. There will be a small horizontal gap between the step plane and the deck through which the unwanted air would want to enter from above, but this can be offset somewhat by placing a gurney flap around the hole. Is there a "hole" in this interpretation?

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ISLAMATRON
0
Joined: 01 Oct 2008, 18:29

Re: Rule Interpretation - Double deck diffusers

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Imagehttp://img8.imageshack.us/img8/6640/diapoa696.jpg
better pic for this discussion... click for super hi-res

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Metar
0
Joined: 23 Jan 2008, 11:35

Re: Rule Interpretation - Double deck diffusers

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I've highlighted the points of interest: Green is the wishbone, yellow is the outline of the holes:

Image

kNt
kNt
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Joined: 22 Jan 2008, 17:32

Re: Rule Interpretation - Double deck diffusers

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@femi: you don't need an account, just go to imageshack.us and upload your grafic, you even get bbcode to post it here.

I read the rules on suspensions, so basically with clever suspension design you can create to hole that are covered by the rear wishbones.
I don't see the wishbone that is covering the rearword yellow hole in the picture, how is it legal?

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