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How can I measure the thrust of my engine?

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nickrulercreator

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I am making an R-candy engine, and I was wondering if there's some electronic or thrust-measuring system I can use to find out the power of the motor. It doesn't matter how basic it is, I just want an approximate measurement. Thanks.
 

prfesser

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I am making an R-candy engine, and I was wondering if there's some electronic or thrust-measuring system I can use to find out the power of the motor. It doesn't matter how basic it is, I just want an approximate measurement. Thanks.
For static tests a decent-quality thrust stand is neither difficult to build nor terribly expensive. Load cell from Aerocon, $30. Build a strain gage amplifier using Burr-Brown INA125 chip, about $20 in parts. DATAQ DI-1100 starter kit for data acquisition, $59; includes software. Hardware for the thrust stand, free if you have a good scrap box :). Laptop computer required. I have the author's permission to post the wiring diagram he drew for the INA125. ;-)

Best,
Terry
https://www.compositepropellantbook.com/

INA125 diagram.jpg
 

jderimig

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For a cheap thrust stand you can use a bathroom scale (mechanical) and cheap Keychain video camera to record and playback the readings.



and a cheap keyc
 

EeebeeE

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For a cheap thrust stand you can use a bathroom scale (mechanical) and cheap Keychain video camera to record and playback the readings.



and a cheap keyc
I would suggest a camcorder that can record at 60 FPS. Perform the static test with the nozzle pointed up and sitting on the scale. A mechanical scale is actually a little better than a digital scale if you know it is calibrated correctly. Record the burn at 60 FPS so that you can see both the scale and the motor burn. When you ignite the motor it is going to push down on the scale and show weight. Play back the video frame by frame and record the scale setting at each frame. If the motor burns for 2 seconds you should hypothetically have 120 data points. These can be plotted on a curve. Measure from the instant the motor starts burning to the instant it stops. From this you should be able to calculate average N/S, total NS (avg. NS x thrust duration), peak thrust, and initial thrust.

If you do not think your motor is going to generate more than about 10 psi, then use a kitchen scale which is more accurate but cannot measure as high of weight. I have one that goes up to 11 pounds (5 kg).

This is old school, but it works amazingly well.
 

jderimig

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. A mechanical scale is actually a little better than a digital scale if you know it is calibrated correctly.
Gotta be a mechanical scale with a dial. Electronic displays are too slow, my bathroom scale doesn't show my weight for at least 2 seconds after I step on it.
 

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