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BuiltFromTrash

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Since I can't post my EX project here (It is at Rocketry Center though), I will post development of my live test stands. I also invite anyone else to post about their live or static test stand, homebuilt or not.

More to come...

IMG_20161010_192626.jpg
(Loadcell attached to anchor plate, 1" thick milled steel. Also, input voltage adjustment resistors.)
 

Handeman

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Are you going to add a pressure sensor to read the chamber pressure too?
 

BuiltFromTrash

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I have thought about it, I want to eventually but I can't right now. I would need to buy one, mount it, make a custom closure, to name a few. Maybe in the future after everything else is work. I will update this thread over the weekend when I have more time.
 

NateLowrie

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I have thought about it, I want to eventually but I can't right now. I would need to buy one, mount it, make a custom closure, to name a few. Maybe in the future after everything else is work. I will update this thread over the weekend when I have more time.
You will definitely need the pressure data to get an accurate characterization that will derive the a and n numbers for your propellants.

What are you using to hold the motor? I also see a custom circuit. Will that interface to a laptop?
 

BuiltFromTrash

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Not concerned with propellant characterization yet. Just motor char. I am still building the mounting systems, thinking about 3D printing the motor mount. Yes it interfaces to a laptop using the arduino serial connection interpreted and saved using Processing.
 

ksaves2

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Since I can't post my EX project here (It is at Rocketry Center though), I will post development of my live test stands. I also invite anyone else to post about their live or static test stand, homebuilt or not.

More to come...

View attachment 303164
(Loadcell attached to anchor plate, 1" thick milled steel. Also, input voltage adjustment resistors.)
Am not a moderator but have you tried to make a request for access to the Research forum?

I don't think a moderator would have issue with a hardware discussion out in the open along with data reduction. Perhaps one can comment.

Formulas are a no-no on the open side of course. I mean if someone says I've done this or that with thermite and burned off my fingertips but did not post the specific recipe that did it, it would past muster.

I think I posted a pic of my burned ear from an augmented igniter test some time ago but not the recipe that did it. Since no formulations posted,
it was not censored for public consumption. Yeah, I still have the ear and yeah it was when I was younger and stupid. Kurt
 

BuiltFromTrash

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Thanks, I am aware of this. No specific construction details or formulation details will be posted in this thread. Pictures of the engine mounted to the test stand may be posted though. If this will be an issue, please let me know as I will either not post, or will pull offending pictures.

As for the Research section, I do not think I will be allowed as I am not a member of any association or club. More info on this issue is welcome as I am not sure of the rules regarding Research access.
 

Handeman

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As for the Research section, I do not think I will be allowed as I am not a member of any association or club. More info on this issue is welcome as I am not sure of the rules regarding Research access.
I haven't looked at the rule for access for quite some time since I've had access for year. I think the primary reason for restricting access is because of ITAR laws. If they also restrict it because of association membership, I would push back on that one. The only reason you need to be level 2 to fly research motors at Tripoli launches is because of the Tripoli insurance. It has nothing to do with any legal restrictions on making your own motors. Anyone can make and fly their own motors legally. They just aren't allowed to fly them at a Tripoli sanctioned and insured launch unless they are a Level 2 Tripoli member.
 

BuiltFromTrash

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If you could post the rules in this thread, I would appreciate it. I would love to have access.
 

BuiltFromTrash

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Thank you for that link. I do not have a cert. or membership, so I will not be able to join unless a concession is made.

As far as the project is concerned, I have everything breadborded together. Something is not working right as I am getting barely any reading out of the loadcell. Also the description for the ADC is screwy as it says everywhere it is a 12 bit ADC, but one bit is a sign bit so you only get +- 1024 resolution. I guess I should have payed a little more attention. Obviously this feature not very helpful as my loadcell does not pull negative voltages. So I may be back to square one.

Gain is set to 2.048v
Input voltage is 4.096v
Differential mode is being used
50kg loadcell for Aerocon systems
Adafruit ADS 1015 12 bit ADC
Arduino Mega
The loadcell is mounted with one side slightly raised a couple thousandths of an inch for clearance and overload prevention.
 

ksaves2

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Look at Aerocon again. You might need an amplifier of some type. It amplifies the loadcell output to the DataQ unit my group used. I have to qualify in that we abandoned testing as we couldn't figure out data reduction. We're talking about
characterization not just simply thrust/time curve. Had some test casings with pressure taps. Kurt
 

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