Air Data

quote:

Originally posted by UFO-LOW:
So if I read that right, you're at 41,000 ft. altitude, 204 kts IAS, 544 kts ground speed, and 0.7 mach. Does your mach number compensate for altitude? What was the wind, if you remember?

That is correct

I don't specifically remember tailwind but it was over a 100. Long time ago.

https://www.nxp.com/docs/en/data-sheet/MPXV7002.pdf

It's kind of irrelevant. Data loging will essentially create that map for me and I won't have to guess if it's accurate.

quote:

Originally posted by comp2:
I think once the initial data is taken, I'll move the sensors back where they are spaced about the same but one is inside the duct. and the others just behind the lip of the duct. This would help understand how much the air speeds up over the duct and how much air is actually going in.

My duct for now is going into the engine bay so the air in the bay will influence the flow too.

My testing was going into a sealed air box from one of the side scoops. It would have been nice to had air speed, but we used pressure, which was positive up to 120 mph. I would have taken the car up to 140 mph, but there was some traffic on the road which prevented me from doing that. The speed is accurate because I have an electronic speedometer and it matches the speed when checked against a GPS.

You may find that your air speed will be less than the air speed on the side of the car when you have the side scoop exposed to all of the air from the engine bay.

I built a circuit dedicated for the project. I went from an over sized 18f4550 PIC to an 18f2520. It's a cheaper processor more appropriate for the project.

The next board the GPS will be on the board instead of an added board.

Next I'm going to 3d print a half case with LCD mount. It will have switch mounts so I can start and stop the recording process.

The SD card buffers are a challenge to solder. Their suppose to be oven flowed but hand soldering works. The resistors on the SD card board are even a lot smaller.

The circuit if functioning quite well now. Turn on and GPS initializes. When the data starts to flow the SD card is initialized. A txt file is created an opened.

Bottom right button starts and stops the data logging. Left button stops the data logging, closes the file and opens a new file for data logging.

The top button stops the data logging, closes the file and stops the program.

The circuit is a bit of a mess. I had to add another board to interface the components so I am redesigning the board to clean it up. I have some other applications for this circuit so it's worth the expense of new boards. It's about $135 to get 4 boards made so the more things I can set them up for the better.

Nice work!

I know there is a lot of interest your data.

Rocky

I've still got work to do but I wanted to see what the data would look like. The weather broke a a little today so I threw it in the truck. To be fair, I still need to do a few things (besides the new circuit). I need to mount it on the front of the truck so I can calibrate all sensors so I can make the sensor range the same.

The truck is going to be nothing like the Pantera. The truck has a rain deflector at the window and elephant ear mirrors so I expected a bit of a turbulent airflow.



Notice the high tech plastic bucket.





Here is the data with some corrections:






That's a little confusing so I reversed it and zeroed it in the spreadsheet before re-charting it. This makes a little more sense:



The actual value is irrelevant. What the air is doing and how it compares is relevant. Sensor 1 is 1" from the window. Each is spaced 1". Sensor 5 is 5" from window. Speed is 0-75mph.

What I can surmise is the air is quite turbulent along the side of the truck. I would not call this a laminar flow.

To make a little more sense of the jumbled data I looked at #1 and #5:



Here's the rest for comparison:

http://www.rc-tech.net/cars2/p...ransam/air/Data3.png

http://www.rc-tech.net/cars2/p...ransam/air/Data4.png

Sensor #4 and #5 almost mimic each other and #5 almost seems slightly less erratic....slightly:

Critical things for a good test will include a drive on a non windy day and with no cars around to influence the air.

If the air was mores stable, there is something else one could surmise:



If sensor #1 was smoother and averaged around "20" (Vertical number) at 70mph then you can compare that value corresponded to about 40mph using sensor #1.

cool...
would you mind sharing the raw data (speadsheet?)

I threw it in the directory the photos are in.

I built an updated circuit. It's a lot more clean:

OK...for the Layman...what the Hell does all the squiggly lines mean? lol

Ill exlain more later but its airspeed graphed to gps speed.

Nice work on the development of the instrumentation, and the electronics.

Very impressive.

I can barely keep my '74 vintage vehicle electronics running - you are building the kind of instrumentation used by aerospace corporations as a hobby!

Keep us posted!

Rocky

Waiting on spring weather.

While waiting for better weather I adapted the same circuit for another project. This circuit is a visual cruise control. The buttons set the speed. The lights light up or go out to indicate how close you are to your target speed. White lights on the left indicate speed up. Red lights on the right indicate indicate slow down.

The idea is, instead of constantly looking at the speedometer, you have a light indicator in the field of view; perhaps on a visor.

Just something I am playing with. One thing that suprised me was how much the cruse control in my truck floated speed. I thought it was pretty good at holding a steady speed. On a highway I think it does but on a road with minor dips it was fluctuating +/- 2mph.

Perhaps set it to reflect as heads up display on windshield. Cool idea. You are extremely talented. Wish I was that smart!

What I am doing is not as hard as it seems. If you like that sort of thing this is a great place to start. It's open source and easy to workwith:

https://learn.sparkfun.com/tut...s/what-is-an-arduino