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lowbridescape 06-30-2008 07:03 PM

Air speed indicator
 
I'm thinking of putting an airspeed indicator on the car. My Ford Escape brick is way wind sensitive. Knowing what the relative wind speed was would be more valuable to me than knowing my ground speed. It would also provide an indication of advantage when following (I'm not calling it drafting) a truck. Any idea how to do that?

almightybmw 07-01-2008 03:16 AM

hobby stores and gadget stores have wind meters air meters whatever you want to call them for about $30. I've seen one at Radio Shack before and Home Depot. hmm. would be a fun way to measure the air speed under your car and above it to determine your approximate "lift." Could also put it in the front and measure the pressure. Huh. I now have another toy I'd like to play with on my car....

dosco 07-01-2008 05:19 AM

High powered model rocketry guys have built (and now commercially market) on-board electronics packages that read barometric pressure, mach number, etc.

Perhaps you could adapt one of those for use on your car.

Why do you see this as more advantageous than your speedometer?

theholycow 07-01-2008 05:48 AM

I love this idea for testing the effectiveness of various drafting strategies. :thumbup:

GasSavers_RoadWarrior 07-01-2008 06:13 AM

Pitot tube?

I remember it was quite intriguing when I tied the MADD ribbon to my hood ornament and had a crosswind and turbulence indicator (Oldskool biplane pilots used to do something similar) sometimes coming up behind a truck it would stand up vertical.

flapdoodle 07-01-2008 07:07 AM

A technique for small sailboats to indicate apparent wind (combined velocity of the boat, and real wind) is a length of yarn atop the mast (about 10-12" long). A piece of tape and 4" of yarn on the hood should do for a car.

dosco 07-01-2008 08:34 AM

Quote:

Originally Posted by flapdoodle (Post 109024)
A technique for small sailboats to indicate apparent wind (combined velocity of the boat, and real wind) is a length of yarn atop the mast (about 10-12" long). A piece of tape and 4" of yarn on the hood should do for a car.

Windex for the larger boats.

lowbridescape 07-01-2008 06:38 PM

"Why do you see this as more advantageous than your speedometer?"

Because the Escape is an aerodynamic brick and is way sensitive to wind speed. Speedometer won't tell me wind speed. I suspect it will live or die based on aero mods and avoiding headwinds.

"A technique for small sailboats to indicate apparent wind (combined velocity of the boat, and real wind) is a length of yarn atop the mast (about 10-12" long)."

The F-4 Phantom II had a piece of yarn and tape on the nose forward of the windshield. Simple works. 'Course it also had a pitot tube the size of a harpoon.

I'm thinking I could put the pitot tube in a hole in the bumper/grill that is at the very front of the car and should be a stagnation point. It doesn't need to read exactly. I'm not concerned with stalling, crashing and burning. A car doesn't have to deal with angle of attack variations either, so a simple calibration should eliminate much of the position error. I don't really want to put a pedestrian skewer on the front because the pedestrian most likely to walk into it would be me...and I hate to see my own blood.

basjoos 07-02-2008 03:10 AM

This subject was discussed and tested in an earlier thread

https://www.gassavers.org/showthread....airspeed+pitot

GasSavers_RoadWarrior 07-02-2008 06:36 AM

Just wondering if an aneroid barometer is sensitive enough to register airspeed pressure changes from a pitot tube. You'd either seal the barometer casing and lead the tube in through a hole or put it in a sealed perspex box. You'd probably need to zero it every day/trip though and it would be altitude sensitive... unless you unsealed the bellows/diaphragm thing.

I remember making a simple barometer with a big tin can, a rubber membrane and a straw. Membrane deflects, straw amplifies movement...

I guess MAP sensors aren't gonna be near sensitive enough, you'd be looking for readings across less than about 5% of their range.


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