# Simple Rocket Motor Test Stand?

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#### christheman200

##### Member
Would the use of an Arduino make this system a bit less complicated? This is my preferred method as I have a good deal of experience with them.
And, I don't see why not, but I will ask anyway; can the motor can be pointed straight down on top of the load cell (with proper support of course)? Is it just as simple as that? This seems like a dumb question to me, but I want to make sure.

#### daveyfire

##### Piled Higher and Deeper
Would the use of an Arduino make this system a bit less complicated? This is my preferred method as I have a good deal of experience with them.
And, I don't see why not, but I will ask anyway; can the motor can be pointed straight down on top of the load cell (with proper support of course)? Is it just as simple as that? This seems like a dumb question to me, but I want to make sure.
Yes, absolutely, wow I can't believe I didn't think of that. (I spend my day bathed in NI and AD DAQ equipment, I think it's something subconscious.) All you need is something to do A/D and record the data. You can certainly fire the motor into the load cell but you're going to have to make an approximation for the propellant mass flowrate through the nozzle and the ensuing weight loss. If your propellant mass is small compared to the thrust, you can probably ignore it.

#### christheman200

##### Member
First, please correct me if I'm wrong, but I believe that the Arduino is capable of analog to digital with it's analog ports.
The propellant mass should be around 5kg, however if the motor under-performs, tests could be done with 20+kgs. How is testing performed without having to make an approximation for the weight loss over time? I'm imaging a system where the motor is on it's side, and one where the fuel is stored off of the stand.

#### daveyfire

##### Piled Higher and Deeper
Yes, exactly, an Arduino is definitely capable of doing A/D and is a great low-cost option for it. We are in agreement! Sorry for wording it poorly.

For more complex stands, the chamber is usually mounted to a load cell independent of the tankage and then coupled using flex lines to minimize the thrust transmission into the feed system. This, of course, leads to all sorts of interesting acoustic instabilities as the whole thing shakes around during testing.

#### christheman200

##### Member
It seems much easier to model the weight difference over time and subtract it than to set up a flex line system.
I found a good resource here on creating a sensor from a bathroom scale https://www.nerdkits.com/videos/weighscale/
It's designed to plug right into an arduino or similar.