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From: Jody Everett <jodyev@in*.co*>
To: "Cost effective home improvement" <freeattic@co*.ci*.uf*.ed*>
Subject: chamber test/Halcyon- report(long)
Date: Thu, 29 May 1997 09:54:24 -0400
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Thought you guys might like reading this.
Jody
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>Date: Wed, 28 May 1997 23:13:23 -0400 (EDT)
>From: Jeffrey A Charlston <charlja@gw*.ci*.gw*.ed*>
>To: Scuba diving discussion list <SCUBA-L@BR*.BR*.ED*>
>cc: dc-scuba@hi*.co*
>Subject: chamber test/Halcyon- report(long)
>Sender: owner-dc-scuba@hi*.co*
>Reply-To: Jeffrey A Charlston <charlja@gw*.ci*.gw*.ed*>
>Content-Length: 4279
>
>My buddy and I were lucky enough to get a chance to volunteer as test
>divers for the Halcyon at the Undersea Research Foundation, Ft. Eustis,
>Virginia yesterday. It was a day of many firsts- first mixed gas
>experience, first chamber dive, and first encounter with a rebreather. So
>here's a few details:
>
>The unit is very impressive. As part of a very thorough testing process,
>the Halcyon's designer is spending the week putting it through chamber
>runs and collecting performance data. On both runs the unit maintained
>extremely consistent PO2 levels at a given depth- on the second run
>variation approached the detectible limit, well below half of a percent.
>This in spite of some initial problems setting up the test; the unit had
>been damaged by the baggage gorillas and had to be patched up well enough
>to make dry runs (a lexan housing had been cracked, but the rest of the
>assembly was fine; so I'd call it pretty robust). The initial run had
>some gas supply problems- the chamber's 1st stage delivery wasn't
>providing sufficient intermediate pressure on the O2 used in part of the
>profile. At an intermediate of only 80psi instead of the 135 designed,
>breathing was labored but not impossibly so. Dry mounting the system also
>required some adjustment- the belows/counterlung is weighted to offset the
>pressure gradient between the diver's lungs and the bag in the water,
>making it sensitive to attitude changes on the surface.
>
>The tests: in a small chamber, maybe 4 feet tall and six long, an
>exercise bike had been set up. The divers were asked to maintain a
>constant 8 mph on the bike through the profile. I "dove" to 99 feet for
>19 minutes, 4 min. at 33 feet, 2.5 min at 10 feet all on EAN32 then
>switched to 100% 02 for 4 minutes. Using the same mixes, my female buddy-
>they're testing with both sexes and making a point to do so- did 33
>ft/10.5 minutes, 66ft/9.5, 10ft/4min, then switched to 02 for 7min 55 sec.
>
>Impressions of the Halcyon: It breathed comfortably at surface level and
>shallow depths, a little more effort to exhale than an open circuit but
>not too bad. The air quickly becomes warm and moist, a nice change. The
>Halcyon adjusts the mix mechanicaly with each breathing cycle, producing
>an odd result that takes getting used to. There's still the familiar hiss
>with inhalation that we're used to, BUT- it comes at the end or
>after the inhalation, and of course varies in length/volume. At first, I
>found myself inhaling harder to "crack" the valve... you adapt quickly but
>it still sounds odd. NB: the noise is less than open circuit even at
>peak flow. The joy of the unit is that it gets EASIER TO BREATHE AT
>DEPTH- at 99 feet it was effortless. I'm told that pattern continues with
>descent... a treat for deep divers.
>
>Chamber testing- dry is not an option! To begin with, set the scene:
>diver bent over bicycle, back against chamber ceiling, eyes three inches
>from bike speedometer, nose clamp in place, on rebreather. Drop to 99
>feet- it's loud, and it gets HOT from the compression. Sweat soon raises
>humidity to 100 percent, obscures vision, your basic sauna. The guage
>that keeps bumping into your nose becomes very difficult to read. On
>ascent, Charle's Law exacts a further toll- the temperature drops from
>@100F to what was probably COLD, but it felt good about then. And all
>that exhaled moisture and evaporated sweat forms a blinding fog. Makes
>for a good workout.
>
>Overall an interesting day. Learned a bit about the R&D side of diving.
>And fell in love with the Halcyon. The thing just set new records with
>WKPP and they're still perfecting it. Unlike the Atlantis, this machine
>will take a diver deep and bring him/her/it back home safe, without
>electricity. If you haven't tried a chamber dive, do- it's an interesting
>experience. And for the record, I volunteered for this and am not
>affiliated with the Halcyon in any way (unfortunately- I want one!)
>
>Safe Diving,
>Jeff
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