13 replies to this topic

[MatsNorway]

Does anyone have some good info about diffusers?

The old diffusers run in the 80s and 90s and such had a lot more angle at the end of it. Now is that a obsolete design today or is it something else, like rules. since todays F1 cars run a much more smooth looking diffuser.

Red bull diffuser. Note how the exaust system vents the upperside.


the 90s Jaguar silk cut diffuser is smooth mostly i think because of gearboxes and such.


And a F1 1/10 scale diffuser



I anyone has a good picture of the f1 85-90s diffusers please post them.

The greater the angle the lower the pressure at low speeds? then again it might stall at high speeds isnt it so?

[DaveW]

I think you will find that the Jag had (has) a pair of full venturi tunnels.

[MatsNorway]

I think you will find that the Jag had (has) a pair of full venturi tunnels.

oh.

that sounds right. but its the same aero prinsiples i think.

[Goran Malmberg]

Many factors come into play in a diffussor. Because of this, I can not say anything with certainty to your
question.
From my own experience, I have concluded that the wing has a large influence on how much one may be
permitted to expand the diffusser. Mainly the location of the lower wing, and the wing on an F1 is subject to
severe limitations.
Goran

[MatsNorway]

Many factors come into play in a diffussor. Because of this, I can not say anything with certainty to your
question.
From my own experience, I have concluded that the wing has a large influence on how much one may be
permitted to expand the diffusser. Mainly the location of the lower wing, and the wing on an F1 is subject to
severe limitations.
Goran

Takk Goran.

But im not sure i quite understand, do you need to ventilate the uppside of the diffusers?

How would the diffuser in our mind look like if the car was like this:

Edited by MatsNorway, 02 May 2010 - 17:41.

[MatsNorway]

What you guys think about diffusers on RC cars?

Will it work on such a small vehicle?

[mmmcurry]

What you guys think about diffusers on RC cars?

Will it work on such a small vehicle?

I can't say that I ever noticed any difference with the rear wing. To be fair though I seem to remember that the dampers on opposite corners were empty and I never noticed a difference in handling, so who knows.

Steve.

[gruntguru]

What you guys think about diffusers on RC cars? Will it work on such a small vehicle?

Size is not the problem, it's speed. If you scale down to 1/10th scale, the mass should be about 1/1000th (1/10 cubed) so you need 1/1000th the DF. Scaled wing area will be 1/100th (1/10 squared) so you can go a bit slower and still get your DF/1000. DF varies as the square of speed so speed at 1/3.16 (sq root 1/10) of the fullsize car will give equivalent DF. (could be errors in this seat-of-pants analysis so please check)

[MatsNorway]

Size is not the problem, it's speed. If you scale down to 1/10th scale, the mass should be about 1/1000th (1/10 cubed) so you need 1/1000th the DF. Scaled wing area will be 1/100th (1/10 squared) so you can go a bit slower and still get your DF/1000. DF varies as the square of speed so speed at 1/3.16 (sq root 1/10) of the fullsize car will give equivalent DF. (could be errors in this seat-of-pants analysis so please check)

Aaaah! we had a discussion one a holiday about that. scale speed, scale weight and what that would translate to in full scale numbers.

Some say that the speeds the rc cars travel would translate to 1000km/h. That might be correct but then if you just scale the weight up you get 13kg and power output at (my car) 5kw.

lets see with your input.

1300grams = 1300kg wich sounds right and has been logical for me without a good argument.

Now is that speed statement correct? 1000km/h if it was full scale. if power also is * (multiply?) 1000 giving me 500 *1000= 500Kw if thats the case i have doubt in full scale speeds being 1000Km/h

Edited by MatsNorway, 03 May 2010 - 06:20.

[gruntguru]

Now is that speed statement correct? 1000km/h if it was full scale. if power also is * (multiply?) 1000 giving me 500 *1000= 500Kw if thats the case i have doubt in full scale speeds being 1000Km/h

Nothing in my post about scaling speed, except to say that the 1/10th scale car would need to travel at 1/3.16th the speed to achieve equivalent DF (ie cornering G's). So if an F1 car corners at 4g @ 300 kph, the 1/10th scale model would achieve 4g at 300/3.16 = 95 kph. Aero drag power (assuming Cd same) would be Cd x A/100 x (V/3.16)^3 = 1/3155 th of the F1 drag power. So if the F1 terminal velocity was 300 kph @ 700 hp the model would need 700/3155 = 0.22 hp to go 95 kph.

[MatsNorway]

Hehe.

there is competition legal motors that has 1800 Watts burst and 1400watts "constant"

Diffuser btw will be around 25cm^2 distributed over 3 "wings"

Rough sketch made in a day.

Main difference from this one is that the side wings will be longer but narrower.

There is no "gills" to adjust the center diffuser on the next model. it will just have a joint down at the motor and a link arm on the middle.

Edited by MatsNorway, 03 May 2010 - 12:55.

[ralt12]

Well---Here is a bit of late '80's tech. First a picture of Tyrrell 017 with its rear diffuser:
(exhaust exiting through the floor)


Then some experimentation on the part of Tyrrell with the 018/019's, using two very different designs; at least 5 major variations from one to the other:
(exhaust exiting above the floor)




Strakes for both are different as well.

[MatsNorway]

Thanks!

I wonder if todays cars also angle the side entry of the diffuser to suck inn air from the sides. That J bend in the beginning looks like it would create some vortex or at least turbulence.

If the vortex upper side spins away from the main diffuser it could help keeping the pressure low in the middle. At first i believed it would spin the other way but because the diffuser angels up before that "J" turn it would possibly generate low pressure making the vortex go upp into the diffuser and spinn that way so it does not fill the middle diffuser with air so easily.

[ralt12]

This really is a demonstration of how the diffuser elements evolve over a two-year period. The 017 is entirely different, as it should be, designed by Brian Lisle; but the 018 was Postlewaite's dramatically new effort, taking the marque from mid-to-low pack to close to the front, even scoring a podium in '89, and really culminating with the electrifying duel between Senna and Alesi in Phoenix 1990. The first 018 floor was on the car for 1989, and the second one didn't appear until 1990--it's possible it might be a 019-only unit, though the bodywork (engine covers, sidepods, internal ducting) are the same.