pitot tubes on race cars

[Rocket Science Racing]

> Date:	Thu, 22 Jul 2004 12:40:04 -0400
> From:	Brett Dikeman <brett at cloud9.net>

> Out of curiosity, anyone know why a number of the prototype ALMS cars
sported pitot tubes?
> I've seen the same thing on pictures of F1 cars.
> Sorta visible here if you click on the image for the larger version:
> http://frank.mercea.net/zoph/photo.php?album_id=20&_off=8
> (right in front of the headrest hump)
> Oh, and much better visibility here:
> http://frank.mercea.net/photos/cars/CRW_4399.jpg

Yup, there it is. Check out www.piresearch.com. They are THE GUYS for pro
level data acquisition. You'll have to register with them (no big deal) to
see the product data sheets. Interesting stuff, actually. Here's an excerpt
from their pitot tube product data sheet:

"A pitot-static tube is a device which enables the measurement of the
dynamic pressure of a fluid in motion, such as the air flow around a moving
vehicle. Dynamic pressure can be thought of as the frontal pressure seen by
the car due to its motion through the air. The aerodynamic performance of
the a vehicle is proportional to the dynamic pressure and so its measurement
is important in understanding variations in a vehicle's performance around
the track.

A pitot-static tube has two ports; static pressure and total pressure. The
difference between these two pressures is the dynamic pressure. Connecting a
differential pressure transducer across the two ports will therefore measure
the dynamic pressure directly."

> Neither seems terribly useful in a racecar with four perfectly good wheels
to measure speed from(and an accelerometer to tell when
> there's wheelslip, for example).  If you need an artificial horizon gyro
in a racecar, you're doing something wrong :-)

VERY useful, see above.

I have an AIM Sports Mychron 3+ data acquisition unit on my roadrace
motorcycle. Not exactly a PI system, but I can't imagine racing without it.

> "They that give up essential liberty to obtain temporary
> safety deserve neither liberty nor safety." - Ben Franklin

Nice sig!

Scott
98.5A41.8Tqm