$5 Vacuum Chamber (Altimeter tester) from the Grocery Store

Worked with my Estes Altimeter.
Could not get this to work with my JollyLogic AltimeterTwo, which I think has more sophisticated launch detection.

That works. I needed to test an altimeter and talked to Jim Amos ( Missileworks) about it. I used a 2" diameter viewtainer with one end closed, dropped the altimeter into it, and drew the air out with my mouth. Worked like a charm.

markkoelsch said:

That works. I needed to test an altimeter and talked to Jim Amos ( Missileworks) about it. I used a 2" diameter viewtainer with one end closed, dropped the altimeter into it, and drew the air out with my mouth. Worked like a charm.

Click to expand...

I do basically the same thing with a Foodsaver Marinating container and my Foodsaver.

Great idea!

I saw this over the weekend at Toys R Us (on clearance for $10) and was considering it for the same, but didn't pick it up or have time to really look it over:

rharshberger said:

I do basically the same thing with a Foodsaver Marinating container and my Foodsaver.

Click to expand...

What altitude can you get with that set up? I don't have Food Saver brand. Mine is a Nesco vs-02.
I've been doing the shop vac with tiny hose adapter, hooked up to the AV bay technique, but would like something easier & "see thru". Thanks!

TMR said:

What altitude can you get with that set up? I don't have Food Saver brand. Mine is a Nesco vs-02.
I've been doing the shop vac with tiny hose adapter, hooked up to the AV bay technique, but would like something easier & "see thru". Thanks!

Click to expand...

iirc its like 10k'. I use christmas bulbs to simulate ematchs and stick everything inside the container.

If you don't mind laying out the $25, the Adept VCK2 is very nice.

Bat-mite said:

If you don't mind laying out the $25, the Adept VCK2 is very nice.

Click to expand...

Interesting, never knew they made this.

Sabrina said:

Worked with my Estes Altimeter.
Could not get this to work with my JollyLogic AltimeterTwo, which I think has more sophisticated launch detection.

Click to expand...

Definitely; the Altimeter Two will only start recording flight statistics if its onboard accelerometer says it should.

I always use a 1 quart mason jar...
I drilled a hole in the lid for a plastic tube,,
hot glued the tube in place..
Works great...

Teddy

onebadhawk said:

I always use a 1 quart mason jar...
I drilled a hole in the lid for a plastic tube,,
hot glued the tube in place..
Works great...

Teddy

Click to expand...

What do you use for a vacuum source?

I would imagine mouthpower, though a shop-vac would work too.
Rex

Yes Jeff,,
I do use mouth power..
A very interesting point..
I don't understand the technicality to explain this, but,,
I am an Eggtimer fan,,
I've built many Eggtimers..
My normal process is I build one,,
solder very long wire to the 2 pyro outputs and for the battery connection,, permanently jump the switch..
Bring it inside to my desk,, hook it up to the computer,, do the master reset..
Then disconnect it from the computer,, turn it on,, put it in the mason jar,, close lid tightly,,
put tube in my mouth and draw quickly,, again and again,, draw and draw..
I'd always get between a 4000 and 5000 fy flight,, successful,, great,, open jar,, reconnect to computer,,
download the flight,, all looks great,, mount it in the rocket,, fly it,, never a variance,, never a problem..
Then I bought a Marsa 54L...
I tried the same process,, "prove" the Marsa before mounting it on the sled..
It failed every flight..
John D,, the designer said show me the failed flight..
He said look at that line,, not smooth,, not linear,, each and every up and down was the pumping or drawing with my mouth..
The first "down" was read as apogee,, I flew the Marsa and it always worked flawlessly.....

Teddy

Rex,,
That's interesting,,
I didn't think a shop vac would make enough vacuum..
I was getting 4000+ ft flights..
Maybe,,
Worth a try I guess...

I tried the vacuum w/ my stratologger, got to test mach inhibit, apogee detect, and deploy alt. all in one test . the 'apogee' was about 3100'(had Xmas lights hooked up to the pyro channels).
Rex

Wow,,,
Very cool Rex,,
So a shop vac made 3100 ft...
No real reason,, I just didn't think it would..
Maybe because of how hard it is to make 4000 ft with your mouth...
I'd have thought the shop vac would make 1000 ft or something like that..
Very interesting Rex...
Thanks man,,

Teddy

On Mythbusters recently, they showed that a household vacuum cleaner can lift a car off the ground!

Wow,,
Musta been a lota surface area...

Teddy

You got it!

I test my alts using the ziplock vacuum bag with a pickle jar slipped inside. Has worked for eggtimers and an Adept Alts25 so far. The pickle jar prevents the solder joints from poking through the bag. Obviously it only works with tree lights, no ematches.

Plastic cup, nitrile glove stretched over the top. Pull up on glove. Slowly release.


Later!

--Coop

I've used various methods but I found with altimeters that have 'mach detect' (such as the Stratalogger CF) you have to pull the vacuum slowly enough so you don't simulate breaking mach. I bought 3 of the CF's and got very strange results until I figured out that sometimes I pulled the vacuum fast enough that it triggered the mach delay so the light bulbs fired late. Once I figured that out it made testing a lot easier. (Rex mentions the same thing but unless you are familiar with the Stratalogger it may not register.)

So a slow steady draw seems to produce more realistic and reliable results.


Tony.

A typical shop vac suction is rated for ~ -55" of water ~ -4" Hg ~ -2 psi which is equivalent to ~4000 ft. AGL.

The syringe method is simple and works well and predictably if you don't have a leak. The math behind it is quite simple.

You have a vacuum chamber with volume V1 and a pressure P, and a syringe with volume V2 at the same pressure P.

When you start, the volume of the syringe V2 = 0, and after you pull back the syringe, the new volume is V2' and the system has a new pressure P' which is less than P.

P x (V1 + V2) = P' x (V1 + V2') and is a constant as no air is added or removed from the system.

So let's see how it works. The larger Adept tester has a V1 = 500 cc and uses a 60 cc syringe. If we neglect the volume of the tubing and the altimeter, you get these approximate test values.



Bob

Nice, Bob. That is consistent with what I have seen with my Adept tester.

rharshberger said:

iirc its like 10k'. I use christmas bulbs to simulate ematchs and stick everything inside the container.

Click to expand...

Thanks Rich!
Today I tested 2 new Alti's & they are good to go! Only 4 more to test.
Using my "Food Saver", a long - used - food saver bag (custom cut for a long fin project), and alti mounted to sled & inside a 4" dia AV Bay, I turned on alti, slipped entire AV bay inside bag, put bag edges on sealing surface, closed lid & set to VAC only. No need to close up AV bay with nuts/wing nuts or cover any vent holes.
After it looked like all air was removed I shut off VAC & without performing a SEAL function, just waited for air to slowly leak out.
Drogue Xmas light lit within a few seconds, and after about 10 sec's the Main output illuminated followed quickly by the AUX(main backup) xmas light.
Both alti's got about 9K' with descent rates of about 300 fps drogue / 100 fps main & max velocity of about 1700 fps...lol....good enough!
Anyhow...much quicker, cleaner, quieter than the Shop Vac routine. The Shop Vac will only be needed for ground testing.....PIA.

All good suggestions here for the OP! Love the cup & glove idea....

TMR said:

What altitude can you get with that set up? I don't have Food Saver brand. Mine is a Nesco vs-02.
I've been doing the shop vac with tiny hose adapter, hooked up to the AV bay technique, but would like something easier & "see thru". Thanks!

Click to expand...

https://www.nesco.com/files/pdf/vs02_careuse_trilingual_web.pdf is your manual. It says you have a vacuum port so you could use these vacuum canisters https://www.nesco.com/products/Kitc...s/Vacuum-Canisters-for-VS-02R-Model-Set-of-3/ for testing your altimeters.

It might be easier than using a bag and pull a better vacuum (get to higher simulated altitudes).

Bob

Coop said:

Plastic cup, nitrile glove stretched over the top. Pull up on glove. Slowly release.


Later!

--Coop

Click to expand...

I tried this today, worked great. I could only get about 220 feet out of it but that should suffice for testing. Any sane altimeter will fire the main shortly after drogue if the flight never got as high as the main trigger.

Usually I test my altimeters in the air!

bobkrech said:

https://www.nesco.com/files/pdf/vs02_careuse_trilingual_web.pdf is your manual. It says you have a vacuum port so you could use these vacuum canisters https://www.nesco.com/products/Kitc...s/Vacuum-Canisters-for-VS-02R-Model-Set-of-3/ for testing your altimeters.

It might be easier than using a bag and pull a better vacuum (get to higher simulated altitudes).

Bob

Click to expand...

Thanks Bob! I learned a lot here reading your posts!

I will probably pick up a a set of those canisters someday, so thanks for the link! I might even be able to control the "descent rate" better with that hose....maybe pinching it shut, turn off the VAC....slowly release the pinch off.

Wait? "Slowly release the pinch off" ....:blush:

watermelonman said:

I tried this today, worked great. I could only get about 220 feet out of it but that should suffice for testing. Any sane altimeter will fire the main shortly after drogue if the flight never got as high as the main trigger.

Usually I test my altimeters in the air!

Click to expand...

Cool!

Yes, my MW alti's fire all 3 outputs even if reaching hundreds of feet lower than what the Main & Aux channels are set to. I guess they all do this, thankfully.