How to simulate water pressure at depth

Hummm we call that a mirage... "witch water". Ya mean if I chase it far enough it gets wet?

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

Damit. And I need some help in carting stuff off, as I lost the warehouse. They are going to bulldoze it to make room for an empty lot. Sigh..and Ive got till the first of Aug to clear out my stuff.

There is at least one fixerupper Boyer Shultz surface grinder in there with your name on it, free of charge. (actually two or more..but Im sure someone can make it over)

Gunner

"Pax Americana is a philosophy. Hardly an empire. Making sure other people play nice and dont kill each other (and us) off in job lots is hardly empire building, particularly when you give them self determination under "play nice" rules.

Think of it as having your older brother knock the shit out of you for torturing the cat." Gunner

[...]

Dunno if this is appropriate to what you're doing, but waterproof watches are tested with vacuum. They suspend the watch in a small container full of water then draw a vacuum and look for bubbles. Has the benefit of keeping the innards dry if there's a failure. Of course, that's backwards from what you're doing, and only puts out a single atmosphere at best, but they certify watches to 100M or so doing it.

Suckage, that's twice in a year.

I'd love some steel and other metal tidbits, and a mini mill/mini lathe, but I don't have room for much else. My 2-car shop (well, shop with attached home) is mostly designated for wooddorking rather than metalheading. the table saw, carving bench, lumber rack, assembly table, bandsaw, planer, dust collector, bench, clamp rack, air compressor, tool box, fridge (fire safe for flammables) and belt sander/drillpress/mortiser bench pretty much take up the space.

Since the cheaparse Chiwanese 14" cutoff saw from Ebay fried itself in

5 minutes, I could use a small metalcutting (4x6?) bandsaw, though. And a sweet little HF TIG unit. ;)

Some other time, I guess. Darn.

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I think the final answer is a 2-1/2 gallon pressure paint tank from Harbor Freight because:

1) It has a good size opening 2) Can take the pressure (80psi) 3) Affordable ($80 US) 4) AND they have a store a one mile away from my house :)

Again, thanks for the suggestions.

I work with underwater vehicles all the time (We do R&D on sonar systems) and the way we check for leaks is to draw a vacuum inside the vehicle and let it sit as long as possible and see if the reading changes. The less obvious advantage of this is that we can back fill with dry nitrogen and not have to worry about condensation when the vehicle hits the cold water. We do have a fancy pressure test facility that tests for structural integrity, but most of our shells are rated for at least 1200 feet. You might be surprised how little aluminum it takes in a properly designed shell to be rated for 1200 feet. I would think that as long as you design your hull to hold pressure and are just worried about the o-rings and other seals the vacuum test might work.

-Kris

snipped-for-privacy@hotmail.com wrote:

So -- get 70+ feet of pipe large enough to hold your parts, and one cap. Assemble, stand it on end, brace it form the sides, and fill it with water. Instant small but deep lake. :-)

Enjoy, DoN.

Don't forget the 70 foot ladder. And don't step on the top! It's dangerous.

Peter

Heh.. probably want to take some lunch with you though.

Interesting that it doesn't require warm weather for a mirage- I'll see them here in the winter on real cold days, just takes a little sun on the asphalt.

John

The traditional approach is to take a 16" surplus naval shell and make it into a pressure vessel. Doc Edgerton used one to develop all the underwater cameras for Cousteau. He got a good deal on the shells after WWII and his company then sold them for others to use. They have an 8" left hand threaded plug in the back end, and will handle pressures as high as the ocean can deliver. I used his setup for my thesis work on underwater radio.

Doug White

Sorry for the delayed reply but I haven't kept up with the newsgroups lately. I had some thoughts of building a tethered or radio control submarine camera setup. The thought I had was to fill the submarine with air pressure equal to or greater than the water pressure. One way would be to build it to handle pressure (PVC pipe?) and air it up to a little more pressure than it needs, perhaps 35 - 50 psi in your case. Another idea would be to have an air tank inside and a pressure sensor. If the external water pressure was greater than the inside pressure, crack a valve to let some air pressure inside the submarine. Good luck!

I don't think that air would work well. The gas should probably be dry nitrogen to prevent fogging of lenses and condensation on internal parts.

The cases of fish sonars and other equipment is often purged with nitrogen to eliminate the air moisture.

WB .................