Ground testing

Hello. I plan to perform my first ground test for dual deploy in the near future. My question is, should I pack my rocket exactly like I would for launch or is it ok to leave out the parachutes and reusable wadding since it’s a ground test?

Absolutely, positively do it just like it’ll fly or you’re not really testing anything.

the chute and everything else that goes in the rocket will take up volume. Less volume to pressurize , the less powder it will take. Also will tell you if you have everything packed well, chute wrapped in blanket, shock cord secure and deploys freely. I like to do the "Z" bend and wrap with blue tape to hold in place. You want to make sure nothing will snag on anything. the only thing different I did was to wrap the NC and payload bay with bubble wrap as to not ding them. We have a lot of ice on the ground.

Thanks guys for the feedback. Wish me luck.

Steven88 said:

Thanks guys for the feedback. Wish me luck.

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For the first time I did DD testing, I used an scrap of t-shirt equivalent in size to my packed parachute. The smoking t-shirt let me know that I needed to work on my nomex wrapping technique.

cheers - mark

Steven88 said:

Thanks guys for the feedback. Wish me luck.

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Good luck! You’re improving your chances greatly by doing ground testing.

Steve Shannon said:

Absolutely, positively do it just like it’ll fly or you’re not really testing anything.

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THIS

It’s amazing what a few grams of black powder will do... just don’t get to see it that closely when it’s 3,000’ high

"Train like you fight"

...or fly, in this case.

Make sure you have the motor in the MMT, or at least stuff it with rags. Otherwise, all your pressure goes out the MMT and you get no deployment.

Yes ground test to as close to flying conditions as possible.

I did my Dx3 testing in my backyard with everything in place ready to fly.

The first drouge charge was a little much, full extension on the harness and sheered 1 of the 2 sheer pins holding the nose cone.

I have seen people use a vacuum on the vent band on the ebay to simulate flight.

~John

GalantVR41062 said:

I had used a Estes launch controller with the 2 sets of wires out of the vent hole

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I do the same thing, but I came up with a way to make it simpler. I used to unhook the wires from the altimeter and then shove them through the hole. This not only left open the possibility that I would forget to reconnect them, but was also often frustrating. Sometimes the wires would fall back into the AV bay; sometimes the wires weren't long enough.

I use Doghouse wiring, and it dawned on me one day that if I just order two additional pieces of wire with the connector, I can just disconnect from the alt at the connector, and connect to the extra wire. And since those don't live in the AV bay, they can be as long as I want them to be. Currently they are 12" pieces.

Now everything is simple. If this is not making sense, let me know. It is a real time and frustration saver.

My StratoLoggerCF altimeter manual says to use a shop vac with a piece of foam carved to conform to the ebay static vent hole. I found that one of our swimming pool noodles is just the ticket but it kinda worries me to have my hands on the rocket with the pool noodle pressed tightly against it and then quickly release my pressure and back up before the black powder blows. But that is how the manual says to do it. Maybe using the launch controller wire is wiser

That is a way to test the altimeter, but is not necessary to test the deployment charges. Sure, you can do both at the same time; but that has never seemed appealing to me.

I use one of these to test my altimeter, with a couple of resistors and LEDs that light when the event fires.



Then I don't involve my altimeter at all when testing charges.

Bat-mite said:

That is a way to test the altimeter, but is not necessary to test the deployment charges. Sure, you can do both at the same time; but that has never seemed appealing to me.

I use one of these to test my altimeter, with a couple of resistors and LEDs that light when the event fires.



Then I don't involve my altimeter at all when testing charges.

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That’s my rationale as well. I test the ejection charge separately from the altimeters. In fact, i don’t think I’ve never tested an altimeter with a vacuum. I expect the manufacturers to do that before I buy it. If I ever get around to building my Eggtimer stuff I’ll test it of course.

Steve Shannon said:

That’s my rationale as well. I test the ejection charge separately from the altimeters. In fact, i don’t think I’ve never tested an altimeter with a vacuum. I expect the manufacturers to do that before I buy it. If I ever get around to building my Eggtimer stuff I’ll test it of course.

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Yeah, but if a five minute jar test of my altimeter could catch a glitch that would have wrecked my $2000 rocket, why not? Knowing me, I'd get the one-in-a-billion altimeter that skipped out w/out any QA.

And my kids like to watch the lights go on and off.

Steven88 said:

My StratoLoggerCF altimeter manual says to use a shop vac with a piece of foam carved to conform to the ebay static vent hole. I found that one of our swimming pool noodles is just the ticket but it kinda worries me to have my hands on the rocket with the pool noodle pressed tightly against it and then quickly release my pressure and back up before the black powder blows. But that is how the manual says to do it. Maybe using the launch controller wire is wiser

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Steven88 said:

My StratoLoggerCF altimeter manual says to use a shop vac with a piece of foam carved to conform to the ebay static vent hole. I found that one of our swimming pool noodles is just the ticket but it kinda worries me to have my hands on the rocket with the pool noodle pressed tightly against it and then quickly release my pressure and back up before the black powder blows. But that is how the manual says to do it. Maybe using the launch controller wire is wiser

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That's the way I tested mine in my DX3. Just as the manual says to do it. I actually used a rag and some duct tape on the end of the hose to create a seal against the body tube. It startled me a bit, and I flinched when the charge went off but definitely seems safe enough. The main charge was 1.9 grams of ffffg to break three 2-56 nylon screws. I backed it off to about 1.7.

Boy you guys sure do get fancy. i just ran my e match wires out the vent hole and touched them to a battery

David Schwantz said:

Boy you guys sure do get fancy. i just ran my e match wires out the vent hole and touched them to a battery

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My e-match wires attach to terminal blocks on the outside of the AV bay, so no go for me.

Mine will for flight. But for testing on the ground I just got real simple. I got terminal blocks from Binder. look good.