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john.d.moore
10-25-2006, 08:48 AM
On Modern Marvels show last night "Indy cars traveling over 200 mph produce so much downforce that they are capable of traveling upside down on a ceiling without falling back to earth."

Yikes!

Hmmm...at what point does downforce become drag?

John
'01 Triple Black M Coupe
368/368

gpalmer
10-25-2006, 08:51 AM
..... for Physics. Had to calculate the speed a Formula 1 car had to travel in order to do that."If a gentlemen opens a car door for his girlfriend, then either the car is new, or the girlfriend is." Anon.

arfboo
10-25-2006, 11:15 AM
because they have all these aero tricks to improve downforce while keeping the drag to a minimum.

However it is interesting to note that on an f1 car simple letting off the gas at speed will result in slowing force of -1g!


<a href="http://axisofoversteer.blogspot.com"><img src="http://homepage.mac.com/booboo/.Pictures/axis.gif"height="100"width="100" alt="http://axisofoversteer.blogspot.com"></a>

PaulR
10-25-2006, 01:17 PM
Drag force related to cube of velocity.
So, over 100mph, things get pretty important.
Lots of HP helps!

Note: drag is related to frontal area, not necessarily wing itself.

'dp' was doing some calcs on his new beast.
<IMG SRC=http://mydrive.roadfly.com/photos/pic.php?u=73302r2fUS&i=2642><FONT FACE="Comic Sans MS" COLOR=Gray SIZE=+1>PaulR</FONT>
<FONT COLOR=Black>'CCA Memb #8743
'99 M-Coupe - Silver/Black
'85 325e
'96 VFR750F</FONT>

macc2440
10-25-2006, 01:57 PM

PaulR
10-25-2006, 02:00 PM
a certain Swede couldn't even keep it on a normal surface at that speed.
<IMG SRC=http://mydrive.roadfly.com/photos/pic.php?u=73302r2fUS&i=2642><FONT FACE="Comic Sans MS" COLOR=Gray SIZE=+1>PaulR</FONT>
<FONT COLOR=Black>'CCA Memb #8743
'99 M-Coupe - Silver/Black
'85 325e
'96 VFR750F</FONT>

rdodge
10-25-2006, 05:17 PM
while inverted? A 1000 lb car + 1200 lbs of downforce would have 2200 lbs of contact force on level ground, but only 200 lbs while inverted. Would that be enough to keep it moving at that speed? There woud be other problems as well, like directional stability. Maybe some rudder airfoils with steering input would help. Oil and cooling fluid flow could be a problem also.

mlobo
10-25-2006, 08:10 PM
It would be starved of fuel pretty quick. No flop tubes in the fuel tank. Then you'd get to see how an Indy car looks when it's dropped on its top at 200 mph.


Kevin 368s #19

http://forums1.roadfly.com/preferences/showsigimage.php?img=45881

Gregor
10-26-2006, 01:33 PM
Hmmm. When they calculate downforce is it the total force on the tires, which would be the aerodynamic force plus gravitational constant. If so, when inverted, you would have to subtract the weight of the car from its downforce.


On the upside, M Coupe felt solid as a rock at 150mph indicated on the banks at Pocono. Not bad for a shoe.

Gregor

gpalmer
10-26-2006, 01:38 PM
...... and my career led me in the direction of other equations. I believe the exam question was vastly simplified, the British exam system went through this phase of trying to make questions applicable to real life rather than just have you perform calculations. Hence, physics questions about cars driving on the ceiling inside a tunnel.

All that education, and I pretty much use about 10 equations all the time. ;-)"If a gentlemen opens a car door for his girlfriend, then either the car is new, or the girlfriend is." Anon.

bdougr
10-26-2006, 02:05 PM
BDOUGR Photos (http://www.sportscarimage.com)

<img src='http://home.pacbell.net/bdougr/logo1sm.gif'>

bdougr
10-26-2006, 02:06 PM
good point on the fuel
BDOUGR Photos (http://www.sportscarimage.com)

<img src='http://home.pacbell.net/bdougr/logo1sm.gif'>

danchadwick
10-26-2006, 02:13 PM
Given that they can fly upside down for extended periods of time.

I heard a story about a guy learning to do barrel rolls, but forgot about the case of oil in the back seat. Fell to the roof, as the story goes, along with all the dirt in the carpet, coins on the floor, etc. Apparently not an expertly executed roll? Could have been someone was BS'ing me, too.

rdodge
10-26-2006, 03:00 PM
issues associated with running an engine inverted. Or any other attitude for that matter.

The story about the case of oil is totaly plausable. During my flight training 20 years ago I found lots of strange stuff in the planes. Particularly after doing acrobatic manouvers. Dirt, change, condom (unused thankfully) just to name a few.

gpalmer
10-26-2006, 03:03 PM
...... with joining the mile high club, they have to take it one step further and the turn the plane upside down too. ;-)"If a gentlemen opens a car door for his girlfriend, then either the car is new, or the girlfriend is." Anon.

Gregor
10-26-2006, 04:32 PM
I have a cartoon on my desk for "Particle Wave Baseball." It shows the pitch, the ball leaves the pitchers hand like a particle, then you see a wave form squiggle (I know they don't actually squiggle), and then the pitcher declares, "Strike, Probably".

All I know is that for every doubling of the distance I have 6dB of loss. :->


Gregor

mlobo
10-26-2006, 08:04 PM
mlobo=nitpicker.

Many aerobatic planes have a time limit on their inverted flight. Generally, this is due to their fuel system. The engine is fed its fuel not directly from the main tanks, but from a header tank, which can supply fuel at negative g. It's limited in capacity, thus the time limit. The main fuel tanks will not supply fuel to the header tank at negative g, so you'll soon have no power if you exceed the time limit and run the header tank dry.


Kevin 368s #19

http://forums1.roadfly.com/preferences/showsigimage.php?img=45881

john.d.moore
10-27-2006, 10:50 AM
In the same show, I saw several dragsters apparently flexing upward at the midpoint of the chassis - about 1/3 of the way down the track. At that point the show was focusing on the effects of the front wing pinning the wheels to the ground. I assume that, with the front and rear wings pinning the chassis at the ends and the engine driving the chassis forward, the chassis was "jammed" in the middle and had to flex upward.

John

John
'01 Triple Black M Coupe
368/368

gpalmer
10-27-2006, 12:03 PM
I spend my days using all these complex formulae and then add 10% to the answer, just in case! ;-) I guess at least I am not a structural engineer, where I would calculate a floor loading, then multiply by 7 just in case. I always given them stick.

As engineers go, jokes are few and far between, but the best inter-discipline jab I heard was...... "Mechanical engineers build weapons, civil engineers build targets." Nice."If a gentlemen opens a car door for his girlfriend, then either the car is new, or the girlfriend is." Anon.

PaulR
10-27-2006, 02:28 PM
<IMG SRC=http://mydrive.roadfly.com/photos/pic.php?u=73302r2fUS&i=2642><FONT FACE="Comic Sans MS" COLOR=Gray SIZE=+1>PaulR</FONT>
<FONT COLOR=Black>'CCA Memb #8743
'99 M-Coupe - Silver/Black
'85 325e
'96 VFR750F</FONT>

Kaptain
10-30-2006, 03:01 AM
and that's a 2004 model. the 2005 S7 Twin Turbo has less drag and more downforce than the 04 model.

Kaptain
10-30-2006, 03:06 AM
I'm not sure about the current IRL car, but the current Lola in Champ Car makes its downforce from its wings while the new, and less expensive Panoz DP01 makes its downforce from its underbody which will make for closer racing next year.

http://www.champcarworldseries.com/oneof/2006/chassis/

http://www.champcarworldseries.com/content/photos/2006/By800/20060729P_0028.jpg


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