Adept test Vacuum Chamber

[thobin]

Just finished my vacuum chamber to give the dual deploy a test and it works great! I can only simulate 750 to 830 feet with it so far. I'm looking for a larger syringe so I can test the higher deployment settings. But for now its cool to see it in action. Its just an old plastic bottle that I had in my shop and the clear tube and the syringe I got from Walmart, battery clip and micro clamps from Radio Shack. And some JB weld to seal the wires and tube. In all I'm into it about 6 bucks. The output comes in at a whopping 8 volts not enough sustained power to light a Estes igniter but plenty to light a Quest q2. Next is some live fire 1oz BP tests.:grin:


TA

 

[Sooner Boomer]

What about using a Mityvac hand vacuum pump? Harbor Freight has them for $35.99 on their web site:
https://www.harborfreight.com/mityvac-vacuum-pump-39522.html
You can pull a fairly good vacuum with one of these, and since you've got a small volume, do it quickly too (just don't *over* do it...).

 

[Quaranta]

... Next is some live fire 1oz BP tests.:grin:

Where should we send flowers? :wink:

 

[thobin]

Where should we send flowers? :wink:

Ok 1.5 grams then. I dont want flowers on my grave site I want a bouquet of rockets. :clap:

TA

 

[Coop]

I made my "vacuum test chamber" out of a kid's plastic cup and a leftover medium nitrile glove. Attach a christmas tree lamp to the outputs, hooked up a battery to the altimeter, stretch the glove over the top. After beep cycle is verified, I pull on the glove, stretching it out. When I can not stretch anymore, the apogee bulb lights. At that point, slowly release tension on the glove, until the main charge lights. There's enough room in the cup for two altimeters, so if running redundant, I can see which lights first, and verify my backup main charge occurs after the primary main charge.


Later!

--Coop

 

[troj]

Er, why on earth do you need or want to test with live charges? Just use christmas tree bulbs, and see if they light. Nothing more is required.

If you really want something to burn, then just hook up Quest Q2G2 igniters, and verify they fire -- leave the BP out of it.

To me, testing with live charges and a setup like that is just another opportunity for something to go very wrong. At the very least, it's putting you close to live charges.

-Kevin

 

[DAllen]

Where should we send flowers? :wink:

No no no...we won't need to send flowers. Just send a seeing eyedog and a gift certificate for the nearest hand surgeon.

 

[5x7]

You should be able to pull over 2000 feet by sucking on the tube.

 

[thobin]

Er, why on earth do you need or want to test with live charges? Just use christmas tree bulbs, and see if they light. Nothing more is required.

Well education for starters, test a few 1/2g to 1.5g ejection charges to see whats happening inside my rocket, not all black powder is created equal. Make sure my new ejection packets light properly. With out losing a rocket and potently having a rocket come in ballistic over a crowd.

To me, testing with live charges and a setup like that is just another opportunity for something to go very wrong. At the very least, it's putting you close to live charges.

Perhaps my 1oz joke was taken to seriously, the :grin: wasn't enough to convince some that I was kidding. Not sure what could go any more wrong than setting this up in a rocket on the field? If my distance from it when the charge fires is the issue then I think the 25 feet of tubing I have for the live fire test will be safe enough. I been doing this long enough and made a few mistakes to have learned to bring my asbestos underwear. My only concern is if I can draw enough air with my syringe. I may have to buy the vac pump, or suck on the end!:grin:

Never the less thanks for the concern for my safety.

TA

 

[troj]

Well education for starters, test a few 1/2g to 1.5g ejection charges to see whats happening inside my rocket, not all black powder is created equal. Make sure my new ejection packets light properly. With out losing a rocket and potently having a rocket come in ballistic over a crowd.




Perhaps my 1oz joke was taken to seriously, the :grin: wasn't enough to convince some that I was kidding. Not sure what could go any more wrong than setting this up in a rocket on the field? If my distance from it when the charge fires is the issue then I think the 25 feet of tubing I have for the live fire test will be safe enough. I been doing this long enough and made a few mistakes to have learned to bring my asbestos underwear. My only concern is if I can draw enough air with my syringe. I may have to buy the vac pump, or suck on the end!:grin:

If you want to test charges, that's fine, but using the altimeter, a vaccum jar, and all that -- just makes you be that much closer, adds a lot of work, etc.

Get yourself an Estes controller. Make your charge, put it in place, and fire it via an Estes (cheap!) igniter, and a controller.

It'll be a lot easier to control when they fire, and know what's going to happen, when you do it that way.

With an altimeter and a vaccum jar, it's a lot of guessing on what the behavior is going to be, and when it's going to fire that second charge.

-Kevin

 

[Nerull]

If you want to test charges, that's fine, but using the altimeter, a vaccum jar, and all that -- just makes you be that much closer, adds a lot of work, etc.

Get yourself an Estes controller. Make your charge, put it in place, and fire it via an Estes (cheap!) igniter, and a controller.

It'll be a lot easier to control when they fire, and know what's going to happen, when you do it that way.

With an altimeter and a vaccum jar, it's a lot of guessing on what the behavior is going to be, and when it's going to fire that second charge.

-Kevin

And if it doesn't fire the second charge, you could have an armed altimeter in flight mode with live charges that you need to go up and disarm.

Test your altimeter to make sure it can fire your charge ignitors, and test your charges to make sure they deploy everything properly. You don't need to do both at the same time.

 

[donperry]

I tested mine with live charges and long wires, of the same gauge that i use in the rocket. If they ignite through the increased resistance of the longer wire then the shorter wire in the live rocket will have no problem.

 

[DAllen]

I completely agree with Kevin. By adding live charges you are adding a variable that just doesn't need to be there in the first place. If you want to test charges, then just test the charges. If you want to see if the alt has the power to fire the ematches then just wire up the ematches.

 

[cerving]

My Dirt Devil pulls enough vacuum in a shoebox-sized plastic container to get to about 3000' with a ground ASL of about 700'. It (and any hand pump) are probably best used for testing your baro altimeter to make sure it's working. The flight profile you get is really interesting because the vacuum is so sudden, Max V ends up being about Mach 3 with the apogee coming in about 2 secs. Descent (when you turn off the vacuum) is almost as sharp. A specialized vacuum pump would probably give you a more realistic flight (I know some of the commercial altimeter manufacturers use one) but the cost is beyond what most of us are willing to spend.

You CAN use a vacuum chamber to test your igniter/battery combo (WITHOUT a BP charge, as is the consensus) but most flight computers have some kind of test mode that's going to be easier to use than doing the whole vacuum test.

 

[thobin]

What I think is neat is the small amount or the lack there of pressure to get a reading. How quickly the air pressure drops as you gain altitude just never really dawns on you till you see it measured out. I honestly thought that the small syringe would not register over 300 feet. You can see the line I drew at 5 ml mark that is the 300 ft main chute deployment. I just used my volt meter to record the event, and ran it a few times to get a good average and it was spot on every time. With the exception of the speed of the beeps that count out the altitude (to fast for my deaf ears to make out) this Adept22 is a nice little unit and the price is right. Although this has now peeked the mad scientist in me and I'm afraid I'm going to need a Raven. What are you going to do?:confused2:

TA

 

[John Beans]

At a recent trade show I held a contest where attendees cupped one of our altimeters in their hands and tried to simulate as close as possible to 1600 meters (it was an Olympics theme) of altitude. That's 5,249 feet, or roughly a mile. Anyhow, it also turns out to be about the limit of what you can suck in that way. The person that won sucked 1,599 meters, but most people weren't close.

It would have been equally hard to ask people to simulate as close to possible to 50 feet. As TA mentioned, that's a *tiny* pressure differential. I just picked one up in the lab and tried to suck as gently as possible, and I got 133 feet.

Folks I've spoken with who designed altimeters as recently as 20 years ago talk about trying to get to within 50 feet of actual pressure using then-available sensors. Today we have great, affordable sensors. If you haven't already, take an AltimeterOne and put it into "Curr" mode, where it displays the current change in altitude from where you started it. You can raise it up slowly and see 1,2,3,4 then lower it down and see 3,2,1,0,-1,-2. The fact that it can discriminate the difference in air pressure between the height of you shoulders and the top of your head is awesome.