VACUME CHAMBER

[SCOTT EVANS]

Well, my vacuum pump really sucks after all. In a good way. It turned out that one of its fittings was loose, so once I fixed that, it really pulled it down hard. It inverted the lid of the rubbermaid container I was playing with at about 36,000 feet equivalent which opened the edge seal. Then I tried it again with a spacer to keep the lid from getting too deformed, and it ended up shattering the rubber-edged, see-thru lid. Yikes! Just before it went, the mechanical pressure gage on the pump was reading 21″ of mercury, which (since we only have about 24″ of Hg to start with) means it had about 60kft equivalent.

The larger altitude chamber I’ve been using for the calibrations will clearly need to be beefed up. It’s about a foot on a side, with 3/4″ plywood walls and a see-through lid. But 10 psi * 144 sq inches = 1400 lbs. Hmmm.

Adrian

Id loan you my altimeter to check it, But you would break it! 🙁 It wasnt design for the Stratosphere!

[AdrianParticipant]

I’d especially break it if my chamber implodes. 🙄 But it looks like you were doing just fine testing your altimeter in your own chamber.

[Warren B. MusselmanModerator]

A decent absolute pressure gauge and relief valve on your vacuum pump can adjust things to a pretty fine degree if you’ve got the right relief valve. You can easily, as I’m sure you know, compute the pressure altitude from the difference between off and full on and at whatever relief valve setting. Not what I would call a calibrated altitude, but definitely a viable number – especially if you cross-check with GPS or something.

[Author]

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