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Author: Subject: Body design getting there...
Doug68

posted on 26/10/12 at 12:18 PM Reply With Quote
Body design getting there...

Hi All,

Not posted here in some time, below is nearly where I'm at with the body design on my car at the moment.
I've been stuffing about with CFD for some months now and feel like I'm nearly getting there in getting reasonable results.
At the moment though all I feel I can say with certainty is it has some drag and makes some down force the aim being to make a bit more down force with a bit less drag.

In the picture, the surfaces are pressure red being the high pressure blue being the low pressure and green being atmospheric.
The streamlines show velocity black being slowest white being fastest and magenta being close to the reference speed of the simulation.

Streamlines
Streamlines


[Edited on 26/10/12 by Doug68]





Doug. 1TG
Sports Car Builders WA

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MRLuke

posted on 26/10/12 at 12:53 PM Reply With Quote
From a complete laypersons view, it looks like you are making much more downforce at the front than at the back?

Looks really good though, dont see very many people at all doing this.

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blakep82

posted on 26/10/12 at 12:59 PM Reply With Quote
quote:
Originally posted by MRLuke
From a complete laypersons view, it looks like you are making much more downforce at the front than at the back?

Looks really good though, dont see very many people at all doing this.


my thoughts too, loads of down force on the front, and negative pressure (ie lift?) across the rest of the body?
not something i know anything about, but it doesn't seem 'right' to me? surely you don't really want anything less than atmospheric on the rest of the body?





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Doug68

posted on 26/10/12 at 01:14 PM Reply With Quote
If you look at most of the front body its a shade of blue, meaning the pressure on it is -Ve a lot of this this is caused paradoxically by the wing at the front, this offsets most of the effect of the wing itself.

At the rear you can't see from this angle the effect the Gurney flap is having. but there is a decent area of high pressure in front of that.

I've not really got into looking at balance issues yet, I think that'll be in the fiddle farting once the major design is done.
At some point I'll get together some pictures to show whats going on at the back of the car.

Cheers.





Doug. 1TG
Sports Car Builders WA

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designer

posted on 26/10/12 at 02:51 PM Reply With Quote
Good stuff, what does the back look like?
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GRRR

posted on 26/10/12 at 02:56 PM Reply With Quote
What software did you use to create the body model?
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Doug68

posted on 27/10/12 at 11:10 AM Reply With Quote
Here's a couple of pictures showing the back end of it.
The software I do the 3D design in is Solid Edge. Its not the easiest for doing surface models, but it's what the rest of the car was designed in from a mech cad point of view.

Description
Description


Description
Description






Doug. 1TG
Sports Car Builders WA

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dickie b

posted on 12/11/12 at 09:54 PM Reply With Quote
Had to comment - I love the design and the front 'wing' is pretty unique, though have seen this on a supercar from years back.

Google 'Yamaha OX-99' - a great looking design IMHO

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designer

posted on 12/11/12 at 10:17 PM Reply With Quote
quote:

'Yamaha OX-99' - a great looking design IMHO



Agree, gorgeous car. Thinking about drawing a modern version myself.

Bottom of page here:

http://www.shedworks.eu/projects.html

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dickie b

posted on 12/11/12 at 10:34 PM Reply With Quote
Would love to see a replica made of it - The OX-99 design goes about things in such an unusual way (fighter jet 'cockpit', side hinged canopy , inline central seating etc) - and quite dinky in supercar terms.

Have mused over whether an SDR Storm chassis could be used to base a replica on : bin off the two 'shoulder' seats though but central seat remaining. Roll bar would need work too.

Or - find an old single seater chassis and use that (or that Furore thing?)


happy thoughts anyway !

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designer

posted on 13/11/12 at 12:22 AM Reply With Quote
The seats in the OX-99 were staggered, not in line.
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dickie b

posted on 13/11/12 at 07:36 AM Reply With Quote
Aha - to be honest didn't initially realise there was a second seat there at all.. until a bit of internet picture searching threw up a picture of the second set of harnesses on a small bucket seat behind the main chair. An 'auxiliary' seat as Yamaha described it.

makes sense now it being staggered as you mentioned : wondered where the legroom would of come from otherwise.

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Doug68

posted on 26/11/12 at 01:00 PM Reply With Quote
Here's a video I've done, the design has moved on a bit.

http://youtu.be/_dv23Prbwx8

The spoiler at the rear has increase to 4" from 1" in height to balance the down force.

According to the CFD this shape is allegedly making 476lb of down force with 571lb of drag at 150mph
This gives a CD of about 0.54.
If the numbers turn out to be even vaguely correct then I'll be happy.





Doug. 1TG
Sports Car Builders WA

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designer

posted on 26/11/12 at 01:08 PM Reply With Quote
quote:

The spoiler at the rear has increase to 4" from 1" in height to balance the down force.



Gone from 1" to 4" I presume?

Did you think about reducing the front downforce instead of increasing the rear?

Good work, you certainly have some impressive stuff to play with!

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Doug68

posted on 27/11/12 at 11:28 AM Reply With Quote
Reduce down force are you mad?

Seriously though its a simulation so the numbers are probably off by an amount, so I just do the best I can with it and if in real life it turns out to be too much then it should be easy enough to turn it down a bit.





Doug. 1TG
Sports Car Builders WA

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AllWeatherDan

posted on 27/11/12 at 12:09 PM Reply With Quote
Looks great!

Keep up the good work!





There is no such thing as a stupid question.

Just the ones I ask!

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MRLuke

posted on 27/11/12 at 08:57 PM Reply With Quote
Did you try a rear wing as opposed to a gurney flap? Just wondering if it might offer a bit less drag for the same downforce?

Looks great

[Edited on 27/11/12 by MRLuke]

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Doug68

posted on 28/11/12 at 04:18 AM Reply With Quote
The wing V flap thing is something to look into, the flap though effectively has no frontal area though as it is still lower than the top of the rear wheel arches, which means it does not show up in the CD calc (even though obviously it does create drag).
This would not be the case with a wing.

I've tried wings on the rear and to a certain extent the shape of the engine cover is like it is to give space for a wing to work without having to be too tall. The wing I've been using though generates a lot of force even at low angles of attack, so then the balance goes too far to the rear. I may go back an try with a smaller arrangement though.

To be honest I'd feel like a donkey driving a car on the street with a monster wing on it, hence I avoided it at the rear for the street set up, at the front it doesn't really stick out like a Carlos Fandango add on, so I don't mind it.

I do intend to have a go at what a track set up would look like with reduced ride height, wing, diffuser, splitter and so on, but that's more work for the future.
Looking at the pictures you can see the high pressure on the ground in front of the car, which with a splitter there would be pushing on that for example.





Doug. 1TG
Sports Car Builders WA

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