Help needed with ground testing

[Hal8472]

I have a problem with ground testing and could use a little advice.

What I am using is a Mariah 38 fiberglass with perfect flight stratologger. The stratologger is mounted in the breadbox with the appropriate standoff screws. It's a little tight in there but for ease of access I have it center end in the window.

My priority is testing the shotgun ejection so I have the body off (with shotgun tube exposed). The ejection charge is wired into the stratologger in the drogue screws. The nose cone and breadbox cover is in place. The pressure opening is lined up between the vent hole in the nose section and breadbox cover. I have a switch which turns everything on and I hear the normal stratologger startup.

Other topics here have identified using a vacuume over the pressure hole, which I did. It's a strong shop vac and I checked that the vent is sucking air out and lowering the pressure. I held it for a count of thirty and removed but nothing happened.

I must be missing something and could use some pointers.

Thanks
Andrew





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[markkoelsch]

I think you need to look at this in distinct tests.

First, does the altimeter fire your deployment charges? This can be done without the altimeter in the rocket.

Second test is to see if you have an adequate charge(s) to deploy your chutes. As long as the first test is good, the second one could be done without the altimeter using wires and a battery. It is tough to do everything you want to do testing wise with the altimeter is the bay.


Mark Koelsch
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[Handeman]

A shop vac doesn't always pull enough vacuum, especially if there are leaks in the container. If you want to test the size of the ejection charge, connect the wires to a controller like a Estes Electron beam to fire the charges. You don't need to use the altimeter to test charge sizes. You can use a vacuum container with connections through the lid to put the altimeter in, or use the av bay, to provide a vacuum to test for the altimeter and that it will fire the ematches that will be used. I've found that even with COPD I can suck on a tube and get almost 2,000 ft of altitude from a sealed container. Using the controller for charges and a bottle for a vacuum test for the altimeter works very well. It's best if you can do both together as a final check, but not always needed.

 

[Hal8472]

Thanks, this helps.
Doing things separately now.
My ejection charge is sufficient. I need to find a good container for pressure test.


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[DizWolf]

doesnt need to be fancy

[video=youtube_share;kQCWM0doCf4]https://youtu.be/kQCWM0doCf4[/video]

 

[bdureau]

This is how I am testing mine
https://rocket.payload.free.fr/index.php?option=com_content&view=article&id=8&Itemid=6&lang=en

 

[markkoelsch]

Interesting that you are testing the altimeter. I have done it, but only after a deployment failure. In that particular case, it was my first altimeter and brand new. There was a problem- a solder bridge across the battery causing it to power up the circuit, test for charge continuity, but would kill the battery quickly. Let that sit on the pad for a bit, and you have problems.


Mark Koelsch
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