Building a small Thrust Test stand: Suggestions

[shockie]

I've attached a couple diagrams of my T-T stand I'm building.

I need help on determining the type of metal to use on the L shaped part, 1/2" or 3/4" thick?

the shim thickness and material type

I was going to attach the vertical and horizontal pieces by 4 screws at the L intersection

The loadcellupright .jpg is from aerocon systems and I was going to orientate it horizontally instead of vertically.

I will be using this:

https://www.amazon.com/gp/product/B...d_p=edaba0ee-c2fe-4124-9f5d-b31d6b1bfbee&th=1
with an Arduino Uno.

based upon a combination of these:

https://create.arduino.cc/projecthub/nmrsthrust/model-rocket-motor-test-stand-8cd2e7
https://www.instructables.com/Arduino-Scale-With-5kg-Load-Cell-and-HX711-Amplifi/
https://docplayer.net/99364898-Ardu...nd-nick-cinquino-and-len-johnson-10-2015.html

Mine is going to include the pushbutton relay igniter from the 3rd url.

I plan to attach the T-T stand to a launcher bottom


I will only initially be testing 1/4A-A Estes engines .

This is just a 1st iteration....

So what metal should it be made out of?

Steel? Aluminum? specify please and the shim too.

TIA

EDIT added load cell pdf

Can anybody comment of the specs of this loadcell? or is there a guise online that can explain the terms and if they are good or not?

TD

 

[shockie]

I've decided to go with T6061-T6 aluminum (actually T6061-651) and the L will be made from 3/4" instead of 1/2" . the shim the same material....will try with 1/32 then 1/16" ....

I have email out about the pricing of the Forsentek load cells.

 

[prfesser]

The specs for the load cell should tell the maximum deflection of the beam under load; it shouldn't be very large, a few thousanths of an inch maybe. Make shims about that thickness.

FWIW heavy-duty aluminum foil is about 0.001" thick, and soda-can aluminum is about 0.005" thick. I used both to shim the headstock of a lathe.

 

[Voyager1]

I've been using an Arduino-based thrust measurement system for some years . It is based around a Uno, an LCD shield, 10 kg load cell and HX711 load cell amplifier. The test stand is just 25 mm Aluminium square section with a sealed case to house the electronics. When testing, I just throw a Nomex blanket over the case to protect it from any exhaust and ejected ash.

I also have a setup using the SparkFun OpenScale load cell module. Check out https://www.sparkfun.com/products/13261

 

[shockie]

I've been using an Arduino-based thrust measurement system for some years . It is based around a Uno, an LCD shield, 10 kg load cell and HX711 load cell amplifier. The test stand is just 25 mm Aluminium square section with a sealed case to house the electronics. When testing, I just throw a Nomex blanket over the case to protect it from any exhaust and ejected ash.

I also have a setup using the SparkFun OpenScale load cell module. Check out https://www.sparkfun.com/products/13261

Thanks for that. Nice design. How many samples per sec do you get?

 

[shockie]

The specs for the load cell should tell the maximum deflection of the beam under load; it shouldn't be very large, a few thousanths of an inch maybe. Make shims about that thickness.

FWIW heavy-duty aluminum foil is about 0.001" thick, and soda-can aluminum is about 0.005" thick. I used both to shim the headstock of a lathe.

Is that:

Full Scale Deflection is the mechanical deflection produced by the load sensor when maximum (full scale) load is applied.

So if it says maximum
load is 200% of fs and maximun safe load is 150% of fs....if fs is 1kg then ultimate load would be 2kg and safe woukd be 1.5kg?

 

[Voyager1]

Thanks for that. Nice design. How many samples per sec do you get?

I have the sample rate of the HX711 board set at 80 sps. You might notice that the LCD shows about 160 Hz. That's because I'm over sampling by a factor of about x2 because in this instance the Arduino is in free-run mode. The overall sample rate is still only 80 sps.
I have the load displayed on the LCD as grams, but the serial output is in Newtons for plotting thrust vs time.

 

[Ralph M Bohm]

I've been using an Arduino-based thrust measurement system for some years . It is based around a Uno, an LCD shield, 10 kg load cell and HX711 load cell amplifier. The test stand is just 25 mm Aluminium square section with a sealed case to house the electronics. When testing, I just throw a Nomex blanket over the case to protect it from any exhaust and ejected ash.

I also have a setup using the SparkFun OpenScale load cell module. Check out https://www.sparkfun.com/products/13261

Hello Voyager1,

That looks like a very nice build, indeed! Very clean! In planning my own motor thrust test stand, I am planning on something I will attach to a portable launch pad to resemble the Apollo-era Pad 39B (or 39A) and that way, I may build it to have the thrust exhaust downwards into a flame trench.

May I ask you where you sourced some of the components? I actually have load cells and the associated HX-711s (those can be had off of Ali Express, for example), but I am not familiar with that display which is really cool looking Could you furnish the part number or source for that item?

 

[Voyager1]

Thanks.
The LCD module is a standard shield available for fitting onto the Arduino Uno that I’m using in the test stand. It can be sourced from a number of places that sell Arduino modules, e.g., eBay or vendors such as DFRobot at
https://wiki.dfrobot.com/Arduino_LCD_KeyPad_Shield__SKU__DFR0009_

 

[prfesser]

Is that:

Full Scale Deflection is the mechanical deflection produced by the load sensor when maximum (full scale) load is applied.

So if it says maximum
load is 200% of fs and maximun safe load is 150% of fs....if fs is 1kg then ultimate load would be 2kg and safe woukd be 1.5kg?

That sounds about right.

FWIW the newest DATAQ starter kit (DI-1100) is capable of 40,000 measurements per second when using one input channel, with 12 bit precision (+ or - 0.02%), 20,000 Hz for two inputs. At $59 plus shipping it's a bargain...though it requires a computer with a USB port (it's powered from that port). I usually run at either 200 Hz or 1000 Hz; the latter is convenient because each measurement takes 0.001 second. The included free software means "no programming" and it is fully adequate for motor tests. It will port the results to Excel with a simple command.

Best -- Terry