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Old 11-15-2014, 01:04 PM   #1
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Default Wind tunnel R&D

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Old 11-15-2014, 01:31 PM   #2
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Cutting the back out of the shell is not legal. I'd use the windtunnel to create a legal shell that works (I don't think any of the current shells have been in a windtunnel).
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Old 11-15-2014, 02:35 PM   #3
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I'd love to see some actual aero numbers on RC bodies, that would be pretty neat.
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Old 11-15-2014, 02:52 PM   #4
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I'd love to see some actual aero numbers on RC bodies, that would be pretty neat.
I've seen some calculated numbers (not actual tests) that were pretty surprising. Aero is definitely a major factor.
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Old 11-15-2014, 06:29 PM   #5
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what aboutsome type of defuser at the rear... like the high end sports cars use...
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Old 11-15-2014, 06:39 PM   #6
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what aboutsome type of defuser at the rear... like the high end sports cars use...
Some run this on GT12 cars, around here:

http://www.kamtec.co.uk/index.php?pa...mart&Itemid=53
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Old 11-15-2014, 07:31 PM   #7
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lets see your wind tunnel. do you have the air straightened out? theres a certain way to make a correct wind tunnel. lets see yours.
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Old 11-15-2014, 08:29 PM   #8
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When Bolink went out of business, they put their wind tunnel on eBay. It looked similar to the full size wind tunnels. It had a metal table and box area where the body was tested with card board that wrapped around the top to keep the air moving. It looked like a large 0 laid on its side. Back in the day Bolink would include a wind tunnel sheet with their 1/12 bodies to compare the bodies and also included spoiler and wing data. I wish I would have saved a picture of their design.

I raced for years at the Major Taylor Velodrome in Indy. One year I found an older dodge body that had about an inch longer rear deck lid. I could run my spoiler flat while everyone else had to run 45 degrees or so. A long deck lid = natural downforce with less drag than a spoiler. Won a lot of races running that car until they outlawed it. This was at speeds around 50 mph. Aero matters especially as the speed increases.
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Old 11-16-2014, 03:50 PM   #9
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lets see your wind tunnel. do you have the air straightened out? theres a certain way to make a correct wind tunnel. lets see yours.
http://www.windtunnel.polimi.it/cirive/cirive.htm
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Old 11-16-2014, 07:08 PM   #10
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Link doesn't work
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Old 11-16-2014, 08:03 PM   #11
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Does for me
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Old 11-16-2014, 08:05 PM   #12
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does for me but i cant read italian.
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Old 11-16-2014, 08:40 PM   #13
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Down-force increases exponentially with speed. So the faster you go the smaller the spoiler you need to run to generate the same down-force. Now you will need more grip or down-force in order to corner at those faster speeds.

In my personal experience Iv'e felt how body design and spoilers play a large effect in car handling. I ran a Protoform R9 and the car would constantly whip its rear end around and have far too much steering. I switched to a Mazdaspeed 6 and with the same setup the car was instantly on rails. On a very large outdoor asphalt track I had my rear wing break off one mounting pylon and become inline with the car. Even at the "slower" stock 17.5 speeds it sent the rear end all over the place causing me to lose a couple seconds per lap.

As far as actually testing RC cars in real wind tunnels it would be incredibly difficult to get perfect airflow over the length of the car. Most universities only have wind tunnels hardly large enough for an RC car to sit in(and they take up large buildings)- so homemade ones probably can't yield accurate numbers, if you could even measure them. But I would love to see it done/make one myself!

If you were to actually create a wind tunnel, its best to pull the air over the car. I.e. you have a fan behind the car sucking a vacuum over the car. Its more accurate and precise than pushing air over the car (fan blowing onto it).

If you really want concrete numbers I'd say your best bet would be to create the bodies in Solidworks, autoCAD, NX etc and analyze them through the computers. While this only yields theoretical data it would probably be the best way to compare multiple bodies equally.
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Old 11-17-2014, 08:38 AM   #14
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Originally Posted by coolair View Post
what aboutsome type of defuser at the rear... like the high end sports cars use...
A Gurney flap would be a simpler and more beneficial device to explore, as it can potentially increase rear downforce without sacrificing drag. For a standard 1/10th scale touring car, a proportional Gurney flap on the rear wing would be quite small, maybe only 2mm or so.

The main purpose of a rear diffuser is to aid in airflow under the chassis to escape in a more efficient manner, thus increasing the low pressure flow under the car. However, in order for a rear diffuser to most effective, more of the underside of the chassis would need to be 'sealed' up, negating some of the disruptive air flow.
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Old 11-17-2014, 03:35 PM   #15
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Originally Posted by J.Filipow View Post
A Gurney flap would be a simpler and more beneficial device to explore, as it can potentially increase rear downforce without sacrificing drag. For a standard 1/10th scale touring car, a proportional Gurney flap on the rear wing would be quite small, maybe only 2mm or so.

The main purpose of a rear diffuser is to aid in airflow under the chassis to escape in a more efficient manner, thus increasing the low pressure flow under the car. However, in order for a rear diffuser to most effective, more of the underside of the chassis would need to be 'sealed' up, negating some of the disruptive air flow.
Yep and I'm so glad to see you call it by its proper name.
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