Simple rocket motor test stand

bdureau

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Hi all
I first did a test stand about 10 years ago using a dataQ but I have never been fully satisfied with the result
I done a new one in the last few weeks which seams a bit more promising
It is using an stm32f103c8t6 board and an HX711 board so it is quite cheap to make. I am using an 24LC512 to store the thrustcurve and some bluetooth or telemetry to do telemetry.
Recording is triggered when firing the motor. It can record 41 measures per seconds. And can be calibrated using the application to use different load cells
test stand can be configured using an Android device and do things such reading thruscurve or flashing board firmware
application is in English and French
code can be found on my github
IMG_20210710_215200.jpg IMG_20210711_112115.jpg IMG_20210711_113007_1.jpg Screenshot_20210711-111557.png
 

bdureau

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Just an update on my test stand progress. I have made a PCB.
  • Use any gauge sensor, it calibrate itself using a known weight
  • Trigger recording from your launch controler
  • Can record from 10 to 40 measures per second
  • Can record up to 25 thrust curves
  • Ability to set the recording time
  • Telemetry
  • Multi languages, so far can do French and English but can be translated in other languages
  • Graphical front end using an Android device
  • Connect to Android using bluetooth or 3DR module to do long range telemetry
  • Ability to export to a csv file or a RASP file

IMG_20211108_080145.jpg

The recording now gets triggered from my wireless launch controler
IMG_20211108_074433.jpg
It can record thrustcurves
Screenshot_20211107-230543.png
Plot them

Screenshot_20211107-231919.png

and can export them to CSV or RASP
Screenshot_20211107-231927.png
 

bdureau

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I have done a version 2 of the board so that we can start measuring the casing pressure.
I have bought a 1000 PSI pressure sensor and so far tested it with my bike pump.

P_20220205_150443.jpg

And a friend of mine is doing special casing plugs in order to test that with our Trucore compatible hardware
img_2155.jpg

Should have some good results soon

I have also added the ability to share measurements using whatsapp
 

bdureau

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Thanks. So far it works very well for measuring the thrust, we did fire more than 50 motors however I did one test to measure the pressure inside the casing and I am not sure a 1000 psi sensor was the right choice. I am looking at other pressure sensors so any advice would be welcome.
 

bdureau

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I have tested the motor internal pressure measure on a small 1 grain motor and it works really well.
I am really pleased with the result. Complete setup including the teststand metal bar+ the electronic is around 100 euros
IMG_20220402_182038_309.jpg
In blue you have the casing pressure in PSI and in red the thrust. I have been using an old grain with barium nitrate which is why the performances are not that good. By default the pressure is in PSI but it can be converted to Kpascal or bar.
For the thurst it can be newton, kg or pound
IMG-20220402-WA0001.jpg
And it can ba shared on social media such as whatsapp or emailed etc ...
whatsappScreenshot_20220403-093712.png
 

rAUM

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I have tested the motor internal pressure measure on a small 1 grain motor and it works really well.
I am really pleased with the result. Complete setup including the teststand metal bar+ the electronic is around 100 euros
View attachment 512522
In blue you have the casing pressure in PSI and in red the thrust. I have been using an old grain with barium nitrate which is why the performances are not that good. By default the pressure is in PSI but it can be converted to Kpascal or bar.
For the thurst it can be newton, kg or pound
View attachment 512523
And it can ba shared on social media such as whatsapp or emailed etc ...
View attachment 512521
Looks great how can I buy it?
 

Handeman

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Thanks. So far it works very well for measuring the thrust, we did fire more than 50 motors however I did one test to measure the pressure inside the casing and I am not sure a 1000 psi sensor was the right choice. I am looking at other pressure sensors so any advice would be welcome.
Our test stand uses a 2000 psi sensor, IIRC. Might be 1500. We don't bother with the load cell or thrust curves. All you need to characterize the propellant is the chamber pressure. That is why we use nozzles with no expansion cones. We still get accurate pressure readings but the thrust is much lower so it's easier on the test stand. We test with single 75mm grains so the characterization is more accurate from 54mm to 98 mm. Once you have three or more burns and the characterization, you can put the a & n in Burnsim and it will tell you what the pressures and thrust curves will be for various grain sizes and nozzles.
 

bdureau

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Thanks for the advice. I thought you had to do properlant bun at different pressure to do the characterization?
 
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