RC10Talk - The Net's Largest Vintage R/C Community

This all comes down to the speed of the track you are on. Drag is not a linear force. An object going 40mph has more than twice the drag force as an object going 20mph. The exact reason that a 100HP car can do 80mph and it takes a sleek 500+hp car to do 200mph. In no wind there is not much difference between a box van and a race car at 5mph but at 100mph it is drastic. Boats are a good example because water is of course a more dense fluid than air. Many boats can do 50mph but you need substantial horsepower to go 80mph on water. So on a tight course the bodys effect might be negligable but a fast course it could make a big difference.
They say that an F1 car could race upside down due to more downforce than the car weighs. If the average R/C car is say 5lbs, it is very possible to achieve more than 5lbs of downforce. With the brushless motors and Lipos it is not hard to get these things up to 60mph. In scale that is 600mph and the weight is 500lbs.
I had taken some HD video of my B4 with a 5700kv motor and did high speed runs. Some with the wing on and some with it off to see what the difference would be. In slow motion the rear end was squatted about 1/2 inch more with the wing than without the wing and I don't have the wing shims set to a very aggressive angle.

Wind tunnel tests are the only way to know with any certainty. So, does anyone have access to a 1/10th scale wind tunnel?

For me cab forward bodies are ugly, they can be faster than "old school" bodies, but they are uglier. I have asked my self a question why? The first thing that come to mind is that I have used to see offroad cars where the cab is close to rear shock tower. But after some time I realized that imagine if there is a driver inside in offroad car. In cab rear bodies the driver could be a Barbie size, approximate 1:10 from real human size, except those two things that Barbie has a little bigger than real women. But in cab forward bodies Barbie size driver is way too big, the driver inside the cab forward body could only be about size of thumb or something. This makes those cab forward bodies to look somehow unreal.

For aerodynamics, I feel that cab forward helps. Everybody could drive a real car 50km/h (approximately 30miles/h), open the window and put your hand outside. You could easily feel how different positions affect the feeling that You get.

Jirka

Coelacanth wrote:There's a very simple way to test this, and until this test is done, I'll remain unconvinced and skeptical. Until one limits the variables as much as possible, everything is just conjecture.

Take ONE car. Mount what appears to be a sleek, aerodynamic body on it. Have ONE driver do 100 laps and get an average lap time.

Take the SAME car. Mount the ass-ugly cab-forward body on it. Have the SAME driver do 100 laps and get the average lap time. Everything the same EXCEPT the body.

Compare results. It's that simple. As long as you eliminate as many variables as possible, the experiment becomes increasingly valid. Has anyone done such an experiment?

This is what we did on the truck shell, although we ran 10 min "mains" because of tire degradation and or compounds wearing off. We made no adjustments to the truck running the high flow shell and went to the new one. And out of my driving impressions and lap times I also felt where the truck could be improved suspension wise, to take more advantage of that shell-

Also one big thing in 2wd off road that has not really been mentioned is "scrubbing" speed in the air in order to be able to approach jumps very aggressively and still downside the corosponding jump- the cab forward shells do react in a much more low flying attitude in the air in part because of a fairly flat top of the shell, allowing you to get nose down ( think of your fastest laps on Nintendo Excite Bike ) right off the jump face and get more resistance to slow the vehicle in the air-

ROH73 wrote:Wind tunnel tests are the only way to know with any certainty. So, does anyone have access to a 1/10th scale wind tunnel?

Or even better, one of those water tanks with a slow current and line of dye like I've seen used on various science shows to test fluid dynamics...air is a fluid, after all.

I think the bodies are hideous. I won't get one. I drive so bad I'll never realize any benefits from those bodies if any exist.

Now I wish that I had bought BoLink's back when they sold it on eBay. I think it was pickup only though due to size.

An R/C wind tunnel could probably be made using air ducts. That might even of been what BoLink's was made from. I can't specifically remember.

i was going to build one once using an electric leaf blower, a varaic (variable a/c isolation transformer), 4 scales and some kind of enclosure. when i moved into my small house i was limited on space so i never went through with it.

Another argument for "aerodynamic" benefits on a 1/10 scale buggy....

I bet if this dude had one of these ridiculous body's he'd of gone at least .3 mph faster....


http://www.youtube.com/watch?v=h8Bz3INEm2I&feature=related

You can decide not to believe that any of this stuff works, but they don't make these bodies because they get bored down at Proline headquarters. I think these bodies are ugly and stupid, but they would not be made and used if they didn't make a difference on some level. If you crashing 3 times a lap, no it doesn't matter, but very good amateur and pro drivers obviously have found an improvement on the track. As it was alluded to above, it's not windtunnel downforce testing that makes the difference, the on track feel and changes in handling are what these guys are after.