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Old 12-29-2016, 01:50 PM   #46
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That's the downside of trying to use the underbody for downforce. Variations in ground clearance start to matter radically. IIRC, the effects go up to the square of distance.

on the bright side, we're starting off really, really, close to the ground.
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Old 12-29-2016, 02:14 PM   #47
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Nice advices here!

But also extremely difficult to convert to 1/10. Even Colin Chapman failed to build working skirts in F1 1979
I really have to think about how to make skirts work on carpet and not getting stuck in the carpet or the car sides.
Rake is on my list for tomorrow.

Also nice would be a double chassis, like an undertray fixed on the hubs to maintain a stable clearance.

Oh man these ideas have a huge potential to empty my purse
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Old 12-29-2016, 02:23 PM   #48
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This is a useful link: http://www.thirdgen.org/forums/suspe...elly-pans.html

The goal is to get air moving fast under the body. Wing shapes work. But what seems to work best is kind of an inverse NACA duct? It takes air from the flat, and squeezes it up and vertically.

That said, rake and any sort of air control is probally miles ahead of what we have now. :-)

The used to sell ducts that would attach to the back of on road pan cars for this.
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Old 12-29-2016, 04:15 PM   #49
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You're onto something with the double chassis, the Lotus 88 had just that (and that's the reason it was banned).
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Old 12-29-2016, 09:41 PM   #50
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Quote:
Originally Posted by Nerobro View Post
The goal is to get air moving fast under the body. Wing shapes work. But what seems to work best is kind of an inverse NACA duct? It takes air from the flat, and squeezes it up and vertically.
Yes, I agree very much with the inverse NACA duct. I think what it does is creates a vacuum effect by forcing the entering air to travel faster over a longer distance, much like an upside down airfoil.

Somebody needs to build a wind tunnel with force transducers and scales already or this can be debated forever.
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Old 12-30-2016, 06:09 AM   #51
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A diffuser is basically a very intricate NACA duct
Sorry about not having English voice-over, should be self explained though.
+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


And this:
http://www.racecar-engineering.com/t...-aerodynamics/
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Old 12-30-2016, 10:05 AM   #52
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Finished my undertray test some hours ago. I am not happy, but not sad either.

The positive first: You definitly feel the difference. The balance changed adding grip to the rear. So the diffuser did his work. I am not sure with the rest. The car definitely felt like it was pulled down on the straight and entered the fast corner more controlled. I also didn't need to brake as strong into this corner.

Now the negative:
The fastest laptime was very close to my todays best without undertray, but the consistency was very bad. Very few laps were within one tenth in succession. Most differed around two tenth. Without undertray I was within one tenth for 5-10 laps before a bad lap came and these laps were within the same tenth of my todays fastest. So the tight infield makes the car difficult to drive because it behaves unexpected.
Then the undertray needs a lot more ride height to prevent or at least reduce scrub. 2mm isn't enough, so the cars cog is rised significantly.

Indoor on high grip ETS-carpet I don't think a 1/10 tc chassis will benefit.

Lets end with a good thing: The undertray was tough enough to withstand a (small) crash and all abuse I gave it on track.
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Old 12-30-2016, 12:34 PM   #53
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How stupid am I!
@wtcc, do not run shocks! The track might be smooth enough to warrant it and the aero would work much better dead serious. Thank you for sharing your work.
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Old 12-31-2016, 11:54 AM   #54
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Ever since I started racing RC I had thought of making a small wind tunnel and use digital scales.

I don't think it would take too much to put the chassis and body on a 4-scale setup and turn on the wind and see the numbers.

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Old 01-01-2017, 12:14 AM   #55
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A wind tunnel for 1/10 scale cars would be very, very, large indeed. the working section of a 1/10 scale car tunnel would be at least three feet on a side.
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Old 01-01-2017, 11:56 AM   #56
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Indeed, if not mistaken I would need a 12m length wind tunnel, that tunnel on the pic would suffice to Mini-z cars/1/18th though.
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Old 01-01-2017, 12:09 PM   #57
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[QUOTE=wtcc;14782996]Nice advices here!

But also extremely difficult to convert to 1/10. Even Colin Chapman failed to build working skirts in F1 1979
I really have to think about how to make skirts work on carpet and not getting stuck in the carpet or the car sides.
Rake is on my list for tomorrow.

Chapman did not fail. He succeeded exceedingly. Lotus type 79 "ground effects" car, for example. Outlawed by FIA because too much corner speed. Ironically all drivers that drove it felt safer considering so much more grip. Enter the 1500 turbos, 1800hp 1100kgs, more died during this era, ground effects + the turbo monsters would have leap frogged lap speeds 30 years!
The aero skirts worked very well, aluminum sheets in a verticAL channel with Teflon (I would assume) runners. Google Venturi effect.
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Old 01-01-2017, 03:47 PM   #58
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I have a doubt about the rear wings. I see that some have cutting markings on it nerad the middle. Does enyine open those areas on your rear wings?
Is there any effect?
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Old 01-01-2017, 06:14 PM   #59
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Quote:
Originally Posted by roosterreagan View Post
Chapman did not fail. He succeeded exceedingly. Lotus type 79 "ground effects" car, for example. Outlawed by FIA because too much corner speed. Ironically all drivers that drove it felt safer considering so much more grip. Enter the 1500 turbos, 1800hp 1100kgs, more died during this era, ground effects + the turbo monsters would have leap frogged lap speeds 30 years!
The aero skirts worked very well, aluminum sheets in a verticAL channel with Teflon (I would assume) runners. Google Venturi effect.
Ground effects were banned in '83 if not mistaken, season after Gilles V. death (during qualifying). There was the next step in G.E. Lotus 88 that was a double chassis and the why it was banned. The problem with G.E. is that it depends totally on the skirts being as close as possible to ground, losing the downforce if that condition is broken even the slightest, didn't help the cars were death traps...
In RC road racing we can keep the skirts as close to ground as possible because there isn't a driver inside to be motion sick or affected by stiff wheel rates.
Correction: 700kg.

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I have a doubt about the rear wings. I see that some have cutting markings on it nerad the middle. Does enyine open those areas on your rear wings?
Is there any effect?
I've been thinking about doing that, should provide less drag.
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Old 01-01-2017, 09:20 PM   #60
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Quote:
Originally Posted by ic-racer View Post
Ever since I started racing RC I had thought of making a small wind tunnel and use digital scales.

I don't think it would take too much to put the chassis and body on a 4-scale setup and turn on the wind and see the numbers.

A long time ago I worked on an rc dyno - with a 5 HP 3-phase 240 motor connected to a fan. Air speed was about 60mph, so it was great for testing for velodrome racing. You probably don't need 4 scales, but you do need 3. Front wheels, rear wheels and one for drag. You can use a pulley connected to a weight and the car. The weight will sit on a scale. When the air goes over the body it will push on the car and lift the weight on the scale. The difference between starting weight and ending weight is the amount of drag. It is easy to get downforce; but hard to do it without getting more drag.
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