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antique diver
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Double 27's - Valves down

Mon Jul 08, 2019 12:24 am

These were firefighting SCBA's (singles) in an earlier life, ca. 1960's. I acquired several from a fire department a few years ago, and finally go around to putting two together in a somewhat unusual configuration (compared to today's norm).

Shown beside 38's for size comparison, they are virtually the same length, but only about 5.25" in diameter, maybe slightly more. Weight as shown and full of air, 28#. I think these will be fun to dive with.
27s and 38s.jpg
27s on back.jpg
The thing I like about valves down is the ability to keep track of approximate remaining pressure without a pressure gauge by using the "cascade" method. If beginning with 2200 psi, and only open the starboard tank valve, I can breathe that tank down to point of increasing breathing effort, then open the port valve to let them equalize. They would each then have a little over 1100 psi each. Closing port valve and repeating the procedure will result in each tank having over 550 psi. Depending upon depth and other conditions I can begin ascent at that point or once again turn off the port valve, saving that half of the air supply for ascent when the starboard side gets low. Perfect for the easy diving that I will use these for.
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antique diver
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Re: Double 27's - Valves down

Mon Jul 08, 2019 5:02 pm

I did the volume calculations based on measured water volume one of these cylinders held, and it was pretty close to my original calculation based on estimated internal dimensions.

Looks like each cylinder holds about 24.78 cubic feet at the rated 2015 psi, and with a 10% overfill to 2216 psi the volume is about 27.26 cubic ft.

Haven't put them in the water yet to check buoyancy characteristics, but expecting the regulator end will be a little light. Hopefully I can take them diving this week.
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SurfLung
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Re: Double 27's - Valves down

Mon Jul 08, 2019 5:46 pm

VERY nice! Man, that's a comfortable looking rig. I'm fascinated by the connections you made to mate the original valves and create that thin vertical tube to position a double hose regulator just right. :)
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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antique diver
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Re: Double 27's - Valves down

Mon Jul 08, 2019 6:39 pm

Thanks Eben.
I was able to lower the regulator mounting about an inch today without cutting tubing, just using a shorter Scuba block. The tubing connection makes it easy to change the outlet type in the field from Scuba yoke to DIN or CGA-346 as seen here (which allows attaching my Aviation Oxygen reg).

This is one double's rig that this vintage guy can still don over the head, Mike Nelson style. And these aren't even Balsa wood.
27s intrchngbl outlets.jpg

Here's how the tubing is firmly and safely supported by going through Delrin blocks at the band connections.
27s plumbing.jpg
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ScubaLawyer
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Re: Double 27's - Valves down

Mon Jul 08, 2019 8:34 pm

Way too F'n cool Bill !

Your ingenuity never ceases to amaze me. You have given me the incentive to get back to a few of my projects.

Your California dive buddy, (currently camping in Arizona at the North Rim of the Grand Canyon after spending a few days camping and hiking in Zion National Park in Utah). M
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

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antique diver
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Re: Double 27's - Valves down

Tue Jul 09, 2019 9:01 am

ScubaLawyer wrote:
Mon Jul 08, 2019 8:34 pm
Way too F'n cool Bill !

Your ingenuity never ceases to amaze me. You have given me the incentive to get back to a few of my projects.

Your California dive buddy, (currently camping in Arizona at the North Rim of the Grand Canyon after spending a few days camping and hiking in Zion National Park in Utah). M
Thanks "M"! (that sounds rather James Bond-ish) 8)
Glad you like it. I enjoy making stuff that's a little out of the ordinary.

I would also love to be camping right now in those beautiful places you are visiting. Have a great time! :D
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rhwestfall
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Re: Double 27's - Valves down

Fri Jul 12, 2019 3:02 pm

ingenious!
Bob

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antique diver
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Re: Double 27's - Valves down

Fri Jul 12, 2019 4:32 pm

Thanks Bob.
How's that cool compressor rig you put together working out?
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rhwestfall
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Re: Double 27's - Valves down

Mon Jul 15, 2019 8:57 am

Air test last night, and being shipped out today! Thanks for the link to the alternative testing company. See how they perform.
Bob

No Longer Awaiting my Kraken.....

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antique diver
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Re: Double 27's - Valves down

Mon Jul 15, 2019 9:24 am

rhwestfall wrote:
Mon Jul 15, 2019 8:57 am
Air test last night, and being shipped out today! Thanks for the link to the alternative testing company. See how they perform.
I just took two air samples last week using their setup, and waiting to hear back. It was a very simple process compared to all the other companies we have used. Took only 3 minutes plus about 10 minutes to set up and fill out the paperwork.

Were you able to deal direct with the lab or did you have to go through a dealer?
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rhwestfall
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Re: Double 27's - Valves down

Mon Jul 15, 2019 10:18 am

Directly with them. They were very user friendly. I explained that it was a privately owned compressor for non-commercial use, and it didn't bring up any flags like others have.

Sample kit was also very easy to utilize.
Bob

No Longer Awaiting my Kraken.....

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antique diver
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Re: Double 27's - Valves down

Fri Jul 19, 2019 9:39 am

My diminutive 27's got christened at Wheeler-Branch lake this past Tuesday. Vintage diver Milton joined me for his first open water dives since the 1970's, and he did great, looking like he had been diving all the time. It's good to finally have someone local that appreciates the fun and simplicity of vintage style diving, and I expect to be going more often now.

The concern I had about them being a little positive at the butts (which were now inverted and at my upper back) was unwarranted. The 27's were very well balanced in the water, and a real pleasure to use. The light weight and short length makes them easy to handle out of the water too, and having more air than a longer single 53 is a plus in such a light package. To me the most fun was being able to easily access the valves to "decant" (as they say down under) from the left tank when the right one got noticeably low on air. Starting the dive with 2200 psi and decanting once when breathing only from the right tank gave me an equalized pressure of just over 1100 psi, and on the second decant I ended up with over 550, etc. A great way to keep track of the air supply and still be diving vintage without having to resort to diving with a pressure gauge.
The older I get the better I was.

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ScubaLawyer
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Re: Double 27's - Valves down

Fri Jul 19, 2019 7:17 pm

antique diver wrote:
Tue Jul 09, 2019 9:01 am
ScubaLawyer wrote:
Mon Jul 08, 2019 8:34 pm
Way too F'n cool Bill !

Your ingenuity never ceases to amaze me. You have given me the incentive to get back to a few of my projects.

Your California dive buddy, (currently camping in Arizona at the North Rim of the Grand Canyon after spending a few days camping and hiking in Zion National Park in Utah). M
Thanks "M"! (that sounds rather James Bond-ish) 8)
Glad you like it. I enjoy making stuff that's a little out of the ordinary.

I would also love to be camping right now in those beautiful places you are visiting. Have a great time! :D
Not that it's diving related at all, but here are a few photos I took in Zion and Grand Canyon a few weeks ago. M

Image
Image
Image
Image
"The diver who collects specimens of underwater life has fun and becomes a keen underwater observer. .. seek slow-moving or attached organisms such as corals, starfish, or shelled creatures." (Golden Guide to Scuba Diving, 1968) :D

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antique diver
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Re: Double 27's - Valves down

Fri Jul 19, 2019 7:30 pm

That's beautiful scenery; thanks for the photos. Lot prettier than where I was. I think I need a scenic camping trip this fall.
The older I get the better I was.

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lakediver
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Re: Double 27's - Valves down

Fri Jul 19, 2019 11:21 pm

Beautiful images, is that the North Rim of the Grand Canyon? In regards to the valves down configuration on a scuba set, early Scuba units like the Scott Hydropak, Desco Dolphin and Ted Eldreds Porpoise used this and the more modern AGA Divators likewise. Did the primary use of double hose regulators keep this in the sidelines or even more practically how to store the cylinders?

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