How did you graph your motor's performance, dagabu?

[cecil]

dagabu,

 

I'm very new here, but I thought I saw that among your skills are great graphics on tools (and the ability to make them) and for plotting your rocket motors' performances, as seen below:

 

 

What I'd love to know is how you gather your data, a stress detector? What interface do you use between your sensors and your computer to plot out the points? Really hard to find information on this topic.

 

cecil

[nater]

He uses the ACME test stand. Peret designed the software and paired up the electronics, using a load cell to capture the force from a motor. Dag designed the enclosure and was assembling them.

 

It is a great piece of equipment to help tune rocket motors and drivers. Other solutions required a laptop in close proximity to the motor. With all the electronics mounted inside the stand and memory to save the results, they made just what was needed.

 

Peret wrote the software which plots those graphs. It will also allow the user to predict the height a motor and heading can reach and the time to apogee. This is very useful when planning the right delay time to ensure your shell reaches a safe height.

[Peret]

ACME test rig manual, with pictures

[cecil]

He uses the ACME test stand. Peret designed the software and paired up the electronics, using a load cell to capture the force from a motor. Dag designed the enclosure and was assembling them.

 

It is a great piece of equipment to help tune rocket motors and drivers. Other solutions required a laptop in close proximity to the motor. With all the electronics mounted inside the stand and memory to save the results, they made just what was needed.

 

Peret wrote the software which plots those graphs. It will also allow the user to predict the height a motor and heading can reach and the time to apogee. This is very useful when planning the right delay time to ensure your shell reaches a safe height.

 

Well, I'm impressed and depressed. What I want is possible but I don't have three brains to master such prodigious work. Really though, I congratulate all of you who worked and are working on the project. The only approximation (at least in claims) I've found on the web is here: http://aeroconsystems.com/cart/electronics/data-acquisition-package-03/

 

Have a read and tell me what you guys think.

 

cecil

[cecil]

ACME test rig manual, with pictures

 

Peret,

 

Fascinating reading. So you intend to market this device. How do we learn about that?

 

cecil

 

P.S. How does one send a private message in this forum?

[dagabu]

Yes, Peret sells them, you can PM by clicking on the persons name or icon. The ACME is ready to go out of the box, the aerocon system is parts only, you still have to assemble it, make a housing, acquire the software, calibrate the system, on and on...

 

Peret's is plug and play, no need to transfer the data and make graphs in Excel.

[Oinikis]

If you want to do it for cheap, make a dynamometer, and using a camera (a better one) film the scale. Then check each frame, and you will be able to make a graph, from time/thrust dots collected. If you do it on a squared paper (like maths paper) you will be able to calculate total impulse. It is not as accurate, but it give quite an idea about performance, capability, and grain geometry progression of your motors (I found out this way that my BATES grain do not burn correctly in my motor). If can get commercial and accruate dynamometer, and get you hands on gopro (they can film at 120fps) then you can get some really good data, but even using homemade dynamometer and basic camera you can satisfy your needs.

Edited August 25, 2014 by Oinikis

[BurritoBandito]

Damn Peret. I had no idea that you were so skilled in EE/programming. PM forthcoming.

[Juiceh]

I love my ACME test stand!!!

[cecil]

If you want to do it for cheap, make a dynamometer, and using a camera (a better one) film the scale. Then check each frame, and you will be able to make a graph, from time/thrust dots collected. If you do it on a squared paper (like maths paper) you will be able to calculate total impulse. It is not as accurate, but it give quite an idea about performance, capability, and grain geometry progression of your motors (I found out this way that my BATES grain do not burn correctly in my motor). If can get commercial and accurate dynamometer, and get you hands on gopro (they can film at 120fps) then you can get some really good data, but even using homemade dynamometer and basic camera you can satisfy your needs.

Thank you Oinikis; I will actively investigate this alternative. I've also thought of using a hydraulic scale http://images1.mcmaster.com/Contents/gfx/small/17645tc1s.png?ver=3057027 with a 0-400 psi 41/2" gauge. Filming required, of course.

[Peret]

If you want to do it for cheap, make a dynamometer, and using a camera (a better one) film the scale. Then check each frame, and you will be able to make a graph

I don't know that I'd call that "cheap", but after you've filmed your dynamometer with your GoPro and spent half a day plotting the results frame by frame, tell your sheet of paper the size and weight of your header and ask it how high your rocket will go and how long a delay you need to burst at apogee.

 

[Oinikis]

Well, you get total impulse and weight, and using that you can figure everything out, dV, acceleration, apogee and everything! For instance if you only want to get the time, you can calculate that dV, and divide it by acceleration due to gravity, to get time when it will stop falling upwards, and reaches apogee. Since rockets rarely fly straight up, and drag plays a role, making delay 70% of theoretical time should do the trick By the way I used smartphone to film it up close, and with the scale I made I was satisfied, and only spent like 5 minutes graphing and calculating. I completely agree that getting a normal rig is without a doubt the best solution, but if you can't afford it and do not know how to use it, dyno/camera combo is an option, especially if you live in not so rich country, where you can't afford hundreds of dollars worth of equipment for several small experiments. Do not forget we are not flying into space (yet) and we do not need dead accurate results.

Edited August 26, 2014 by Oinikis

[dagabu]

Hmmmm, the GoPro black is about the same price as the ACME Rocket Test Stand...

 

If you are comfortable doing your testing that way then I say keep on going! To each his/her own, this rig meets all the requirements out of the box, Cecil asked a question and it was answered. You can also tie a rock to a rocket to test the lifting ability, not recommended but you get results instantly. The ACME rig does so elegantly.

[Oinikis]

As I told I used a smartphone to film it, and GoPro might be avaliable from a friend. Dynamometer/camera combo is a start, and later, when bigger stuff will be built, i'll probably get/make a rig.

[DavidF]

The thing I like about the Acme is that I can test different charcoals for my BP. I realize that no two pyros could ever agree on one single test of BP, but testing a nozzleless or end burn rocket on the Acme is close enough for me.

 

I used the Acme to debunk the continuing allegations that balsa charcoal does not produce much gas. I challenged that statement many times, and was never able to ferret out any evidence of any tests on which to base the 'lore'.

 

I used the Acme to quantify my results from experiments to determine the maximum power that could be produced from a rocket fuelled with black powder only. This led me to the conclusion that there was an unexplained reason that hot BP would CATO a rocket while whistle-augmented BP did not. Once I had proven that the CATOs were not related only to power, it was a no-brainer to figure out that the interface between the fuel grain and the inner tube wall was the source of the problem. And that's when I tried waxing the tube.

 

I have several batches of BP awaiting testing with the Acme, that I will use to indirectly analyze my milling times and media for efficiency. After that, I will do a series of either/or tests with the Acme.

For instance: is young willow hotter than old willow? I bet it is. Acme will answer the question.

 

There are so many things a unit such as this can show us. Test results will replace conjecture among us amateur fireworkers.

[Mumbles]

....

 

There are so many things a unit such as this can show us. Test results will replace conjecture among us amateur fireworkers.

 

 

Amen. Data is my favorite way to refute against assumption, speculation, and wild ass guesses.

[Peret]

It's great to see the appliance of science. I'm a bit biased about the Acme, but it's just a tool and the same results can be got in other ways. The Acme just allows you to do it more accurately, more conveniently, and above all more repeatably, than anything I found when I was looking for a tester for my own use. Those were the design criteria. You can't make comparative tests unless you can rely on the measuring method giving exactly repeatable results.

[Maserface]

 

 

Amen. Data is my favorite way to refute against assumption, speculation, and wild ass guesses.

Data is beautiful

[ddewees]

Data is beautiful

To each his own...

 

http://blog.lib.umn.edu/cascw/adoption/Data%20Star%20Trek.jpg

[dagabu]

[Bobosan]

I like Spot, Data's cat.