Static test stand

[n454]

I want to build a static test stand for LPR motors but i don't have a very large budget. Could anyone please advise me on how to build it?

 

[Nytrunner]

Keying in on "Not a large budget": Frame with a spring scale in it. Record the dial readings?

Data acquisition can get costly very fast.

 

[LithosphereRocketry]

If you're OK with fiddling around with Arduino you can get a 100N force-sensitive resistor pad for under $10, along with an Arduino starter kit at around $50-60. Not the most accurate but it works.

 

[Nytrunner]

If you're OK with fiddling around with Arduino you can get a 100N force-sensitive resistor pad for under $10, along with an Arduino starter kit at around $50-60. Not the most accurate but it works.

DIY strain gauge with the resistors?

 

[Charles_McG]

I sell you this spare National Instruments Fieldpoint strain gauge input module?

 

[n454]

I dont want data acquisition just a safe and stable test stand.

 

[aerostadt]

The data acquisition system sounds interesting, but I not familiar with those systems.

About 50 years ago a company called Rocket Development Corp. had a LPR test stand. I bought one and used it for a science project. It consisted of a rotating drum that had wax paper on it. Above the drum was a metal rod that had a spring down the middle and a small wooden arm in front of the spring. On the arm was a clamp to hold an 18 mm BP motor and at the end of the arm was a stylus that that rested against the wax paper on the drum. Everything was painted gray, but the 4" to 6" paper drum looked like maybe it could have been an ice cream container. The drum turned by an electric motor with gears. Knowing the spring constant on the stylus arm and the rotating drum speed one could measure a thrust-time curve.

Here is another TRF thread from several years ago.

https://www.rocketryforum.com/showthread.php?67331-Simple-Rocket-Motor-Test-Stand

 

[LithosphereRocketry]

I dont want data acquisition just a safe and stable test stand.

So just hold-down clamp of sorts?

How much force are you looking at? The simplest answer will be to clamp a motor down to whatever you want to test the safety of and yank on it with a spring scale... Make sure you have plenty of safety margin.

 

[dhbarr]

T-post & rubberized pipe clamps?

 

[Charles_McG]

I take it that 'fires properly' is the only data you're looking for? No max thrust, or average, or burn time?

I think the other question that will help people answer sensibly is 'about what thrust'? If it was an 18mm, I'd probably use a ring stand and a clamp. A K1000 calls for something else.

Edit - wait, you said LPR. Never mind.

 

[Nytrunner]

The absolute cheapest method? Bucket of dirt.

Dampen it so it gets slightly soft, stick the motor in .5", you're done.

 

[n454]

I am actually looking to test fire C6 motors.

 

[n454]

The absolute cheapest method? Bucket of dirt.

Dampen it so it gets slightly soft, stick the motor in .5", you're done.

Is that safe?

 

[n454]

I take it that 'fires properly' is the only data you're looking for? No max thrust, or average, or burn time?

I think the other question that will help people answer sensibly is 'about what thrust'? If it was an 18mm, I'd probably use a ring stand and a clamp. A K1000 calls for something else.

Edit - wait, you said LPR. Never mind.

Yes that is what i am looking to do.

 

[Nytrunner]

Is that safe?

I've only seen it done to E9s to test if the pack is CATO prone, but I'm fairly certain that any Estes black powder motor would be fine in it. Mud/clay has some surprising stickiness. If an E9 won't go anywhere, I can't imagine a C6 being a problem.

That being said, minor investment in a concrete block and pipe straps, hoseclamps, or ductape wouldn't hurt if you wanted to be more comfortable.

Regardless, use the appropriate Launch Controller leads depending on the motor impulse.

 

[n454]

Would this also work with wet snow instead of dirt?

 

[dr wogz]

Dirt is denser than snow, has a much higher melting point, packs together tighter, and has higher friction, and won't potentially soak or extinguish the test subject prior to firing.. I know we have a lot of it (snow) right now, but I'd stick with dirt..

 

[samb]

Is that safe?

No. If you're not collecting data then you're just looking to burn stuff. Just say no.

 

[Nytrunner]

No. If you're not collecting data then you're just looking to burn stuff. Just say no.

Ah, but data has been collected!

CATO: yes/no

 

[dr wogz]

Don't forget as well, that burning a motor pressed into dirt (or snow) with the bushiness end facing up (to see the flame, and to drive itself into the dirt or snow) will pop out of the 'test stand' when the ejection goes.

 

[n454]

Most of the time when i did it with dirt it stayed in the dirt when the charge ejected, once it popped up in the air but only a few inches or so.

 

[n454]

Dirt is denser than snow, has a much higher melting point, packs together tighter, and has higher friction, and won't potentially soak or extinguish the test subject prior to firing.. I know we have a lot of it (snow) right now, but I'd stick with dirt..

Ok thanks i won't try it.

 

[dr wogz]

what exactly are you testing / looking for?

(Seems like a waste of a motor to just burn it in a bucket of dirt..)

 

[n454]

Just looking to watch a motor burn. I like watching static tests.

 

[TRFfan]

Will wet ash also work?

 

[Zeus-cat]

The absolute cheapest method? Bucket of dirt.

Dampen it so it gets slightly soft, stick the motor in .5", you're done.

He's Canadian, so that would be 1.27 cm.

 

[TRFfan]

Actually, i use the imperial scale.

 

[Stan]

A 2x4 and rubber bands