rec.autos.simulators

"Really?", "LOL", and "Bye" simply don't carry enough meaning
for me to figure out what you don't like about my post.

-----------------------------

Your statement here, which Ruud(?) disgreed with, is very loosely
correct in terms of effect, but is about as helpful (and accurate)
as saying that a road car with four passengers plus luggage has
"less braking" than one with just a driver.

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<frowns> Please re-read my paragraph, word by word.  Especially
"steady-state", and my use of "torque" vs "deceleration".

You agreed with

so I don't see your problem with the above, which is the same thing
stated the other way around.

-----------------------------

Again, this was an entirely valid and truthful statement.  In a
1200g (about 2.5 lbs) car, the motor (running to about 20 000 rpm
at 40 mph outdoors) forms a significant part of the total inertia.
Increasing the gearing by 50% (which happens when going from indoor
to outdoor tracks) makes a noticeable difference, which illustrates
my point:

which you then agreed with.

-----------------------------

Again: *what is wrong with my statement?*  The total torque applied
by the engine to the clutch can be positive, in which case the car
accelerates; or negative, in which case it slows down.  In the latter
case we call it "engine braking".

-----------------------------

Yeeees....

Carry on being this un-moderate, and I won't say goodbye - I'll
just add you to my killfile and get on with participating in
discussions here without your interruption.

I'm more than happy to listen to alternative viewpoints and see
if I learn something which adds to my knowledge, but you aren't
going to "convince me" of /anything/ by laughing hysterically in
response to my posts - since I then don't know /what/ you're trying
to convince me of.

Jonny

Weird, drag sounds like friction by definition. But perhaps that's why
it's mostly turbulent and thus proportional to the square.

Ruud van Gaal
Free car sim: http://www.racer.nl/
Pencil art  : http://www.marketgraph.nl/gallery/

The first velocity comes in from mass flow across the wing:
The faster you fly the more air mass you are effecting per second.

The second velocity term arrives because the overall lift
effect of the wing on the airflow is deflecting some
of it downward. So the force is proportional to the
downwash velocity component which is proportional to
the airspeed. (So for a particular shape that rotates
the velocity a particular angle downward, the lift force
is proportional to airspeed squared)

The above might be one way to motivate the correctness of
aerodynamic forces being proportional to velocity squared.
(Without mentioning vorticity once, mostly ;)

The usual way is straight "dimensional analysis".
It is pretty clear the force is proportional to area,
both experimentally and philosophically.
This means that the rest of the equation has to have the
units of force/area. Since this part is also proportional
to density, the remaining part pretty much has to be
velocity squared because it has to have units of
length squared per time squared.

(If you rotate a wing on the end of a stick perpendicular
to a rotating shaft and measure the forces you can get
approximately linear force with speed.
But that is mostly because you spin up the air in the
test area as you do this kind of test.)

--
Matthew V. Jessick         Motorsims

Vehicle Dynamics Engineer  (972)910-8866 Ext.125, Fax: (972)910-8216