Anyone tried this?

I'm building a car you guys might like using exactly what your talking about. Mine however should decrease drag while allowing a certain amount of tunable wind steering. It might make its debut at nationals. Hope it's not a turd.

 

SWEET!!!

The fact that a builder of your caliber is working on harnessing this force validates for me that it is worth further exploration.

I look forward to seeing it.

Best of luck!

 

This made me crack up! /images/boards/smilies/rofl.gif

That's what I always hope!

 

Kinser can back me up on this, but both of us have been around awhile. Builders come and go, some hang for awhile some are just a flash. But it is interesting to see as the cycle turns, that what is perceived as new ideas now has been touched upon in the past. It may not be exactly the same but overall concepts and ideas seem to come up time and time again. Maybe that slight twist or tweak today could take what was thought to be a dud idea of the past to the new speed gain of today. We shall see.

Good Luck.

 

+1

 

Acmes "Airfoil" had a similar setup in 2009.

The way I see it is these similar ideas over time just go to show that great minds think alike.

 

Little tweaks can make something that was unworkable stellar. Do you remember which month that was? I thought it was a Pure Stock. Is that the way you remember it?

 

May 2009 super mods. His was car #1 and really was a thing of beauty. The only reason I remember all the details is because I had a dog in that fight, a Royal Ranger outlaw that actually surprised me by going sub 2.9( Parabola, car #9).

[video]https://www.youtube.com/watch?v=nb59_VEZGf4[/video]

 

Right on. Which month was it that he had the special aero pure stock?

 

Might have been during my hiatus as I don't seem to recall even remembering it. I'll do some sleuthing around though...

*UPDATE* Found it- April 2009 Pure Stock.

 

After thinking about this more, I'm envisioning a small short strake on the top middle, where the angle could be adjusted easily. Someone with a track could figure this out fairly quickly. The earlier comment by Laserman, got me thinking that it may be a negligible amount of drag compared to wheels and other features, if you could run the DFW straight it may overcome it as he stated. The importance stressed for alignment of the rear should still apply to the front wheel...??

I'm slow but I get it eventually! lol

 

This rake seems a bit of overkill but visually speaking this somewhat fits the bill of what I am envisioning in my mind based on your description.

 

OK, WOW...I was going to try to calculate something on this, from the drag stuff I did earlier...I messed up the units on the numbers I did on this....after I said to be careful on the units! I had the air density in lb/ft^3 and everything else in inches and ounces...yikes! Turns out the drag forces are actually lower...like .0X ounces in air for a car body only at 12 mph. Going to edit my previous post with the corrections.

Dang, sorry guys, may still be a little to gain on the body, not sure how this would equate to times.


So now that I fixed the unit conversions, I also ran the numbers for the front wheel:

[table][tr][td]item[/td][td]dimensions[/td][td]Drag Coeff[/td][td]wind speed[/td][td]drag force[/td][/tr][tr][td]body[/td][td]1.75" x .28"[/td][td]0.15[/td][td]12 mph [/td][td].236 oz[/td][/tr][tr][td]single wheel[/td][td]1.170" x .34"[/td][td]0.55[/td][td]12 mph [/td][td].085 oz[/td][/tr][/table]
EDIT: adjusted these drag number again on 5/22

Obviously, double the wheel number for the other front wheel, not sure on the back wheels since the air is probably messed up by the time it gets there. Guessing the whole car probably has around 0.6 oz of drag resistance at this speed??

In the couple races I've watched on the livestream, seems like there are more cars with fenders only on rear wheels, didn't see any with fender on front only I don't believe. Wondering what the thought process is on this set up??

 

Fully exposed rotating wheels create an enormous amount of drag, especially when they're in contact with the ground. Pull a wheelie (figA) and drag diminishes, good news for stunt riders.

Some interesting cartoons for wheels on and off the ground....

 

That is a vortex generator on a air plane. Haha beat y'all to it. It's made for slow flight in aircraft. I have the angles and air movement calculation on it for a aircraft. It can b done. For pinewood cars.

 

That pic came from a site on motorcycle fuel ecomomy talking about drag...it is only a cartoon and who knows where it originally came from... /images/boards/smilies/wink.gif. It was just to show a wheel on the ground vs in space.

So thinking about this more from an improvement perspective, I read on here somewhere that tracks run slower at seal level than at higher altitude. This would be related to air density, and it is a very small factor in the drag equation. This would say that very small changes can have a significant effect on times if density/humidity can change times...

 

That's very true about air density. Today it was 700 feet air density. Two days about its 2100 ft. Same airport it is temp that effects that. So if a room was 66 degrees and then another room was 78 degrees. Density would b higher in the 78 degree room. Which means thinner air in the 78 room

 

Density would be higher in the 66 degree room, wouldn't it?

 

My research suggests that the Cd of a wheel is much higher than .55. Although, that is the number usually documented, it assumes speeds of ~60mph or more. At low speeds (e.g. 12MPH), the Cd of a wheel/cylinder is ~1.5 - basically the same as a flat surface!

 

LB, I could run some basic numbers with different coeeficients. Havent had time to really look into the DC's in great detail yet. I did see where a rotating wheel has less drag than a stationary wheel though. The DC is basically a linear relationship in the equation, so twice the coeff is twice the drag force. The velocity plays the largest role as its a squared term, as expected, the force grows exponentially with velocity increase. Also I just ran at 12 mph as a guess, could be higher at 15 or so?

BR, I would agree the higher the temp, the lower the density, I would expect changes with weather trends also, high/low pressure fronts, humidity, etc. With that said, the only thing we can do is reduce the drag coefficient and everyone races in the same conditions.

On a brighter note, the slower your car runs, the less drag force it will see!! LOL!