Instrumenting the thrust stand
Being that I intend to be use this thrust stand to completely profile my rocket motors, I have been spending a lot of effort building the microcontrollers, software and data acquisition modules. In a sense, I feel like I am playing catch up for all of the work I didn't do on my first motor.
Since there are no moving parts in a pressure-fed liquid rocket motor, there are only a few places you can collect valuable data and even then you must interpolate it into something meaningful. One module in particular affords a lot of insight into the performance characteristics of the motors and that is the mass flow rates for the fuel and oxidizer.
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| Mounting rail for the load cell |
I fashioned a bracket out of a 1 ft length of 2 inch wide 1/8 steel flat bar. I welded it to a 1.5" c-channel that is welded to the top of the frame.
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| Back of the mounting bracket |
I wanted the load cell hanging from the mounting bracket and bolted to the top of the skate so I welded a pad onto the top of the bracket.
Next the skate is made of a 1ft piece of 4 inch 1/8" steel flatbar with 2 1/2" square tubes holding a piece of 1/4" steel flat bar that is threaded for the m4 bolts that fit my v-groove bearings.
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| Skate the the tank is mounted to |
Once assembled the grooves in the skate bearings slide over the 2" flat bar mount to provide a sturdy linear bearing.
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| Linear bearing |
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| Load cell mounts |
The load cell is mounted between the two tabs seen in the picture above.
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| Load cell mounted |
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| Closer picture of the load cell |
I zip tied the tank on until I figure out a better way to hold the 2ft long tank against the skate.
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| Holding the tank that I made back in Ohio. |
Now that I see the concept works, I am making another taller one that will have a universal mount to allow me to hold a variety including CO2, N2O and flight ready tanks.
You did really good job, I wish I could do half of what you have done. Thank you for sharing your work with us nad keep posting more such posts
ReplyDeleteMy daughter (15) and I have been working on something similar. We're planning our first upgrade. Check out https://maiatomars.wordpress.com
ReplyDeleteWe started with measuring Estes C6-3 engines just to get her through a project for school. We are now planning what's needed for other rocket engine types. I think when she finally finishes her presentation video, we'll work towards a GoFundMe since we need a better A/D and our load sensor is only 10kg, so we'll need a 100kg version. I'm also estimating we'll need to buy about 50-100KG of steel and if she wants to work with liquid fuels, they can be quite expensive here. The good news is, we have full access to a massive scale, modern machine shop... did you get the NI600 to work with the load cell?