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Discussion of diving methods and equipment available prior to the development of BCDs beyond the horse collar. This forum is dedicated to the pre-1970 diving.
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ScubaLawyer
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First Name: Mark
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My Trieste actually breathes wonderfully now

Wed Sep 02, 2020 8:13 pm

Well, it took a year’s worth of ‘spiramentin and the knowledge of those far more technically savvy then me, but I finally got my Trieste to breathe well.

Most folks will tell you, me included, that a stock Trieste most often breathes like you are sitting at the bottom of the pool sucking air through a garden hose. It took a longer-than-normal custom made lever from Phil, and a 2nd Stage body drilled and equipped with adjustable venturi set screws courtesy of Bill T. of Texas, to make my Trieste extremely easy breathing.

I’ve gotten my stock Trieste down to 1.5" H2O cracking pressure (at 150 psi IP) but the venturi effect is non-existent and sustained cracking is 3+ inches of H2O. With Phil’s longer lever I got cracking pressure down to .7" H2O but the sustained cracking pressure didn’t change. Enter Bill T. with the concept of drilling two holes in the 2nd Stage body and putting tiny set screws that will move up and down to adjust the venturi.

Today I installed Phil’s lever and Bill’s modified 2nd and cracking pressure is still .7" but the venturi now kicks in (after about 4 or 5 one-half turns of the set screw outward from the closed position) immediately with a sustained effortless flow. I checked the venturi on each ½ turn of the set screw outward. At first the venturi was too powerful and it sucked the diaphragm down and held it there in freeflow mode. I finally found the sweet-spot and the reg now breathes fantastic. Very powerful venturi actually. Put a dab of locktite in each hole. Can’t wait to try it out in the ocean!

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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rhwestfall
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Re: My Trieste actually breathes wonderfully now

Thu Sep 03, 2020 6:56 am

Nice! COVID back burnered my Trieste project. One of those levers.... hmm..
Bob

No Longer Awaiting my Kraken.....

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Greg Barlow
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Re: My Trieste actually breathes wonderfully now

Thu Sep 03, 2020 8:11 am

Mark, that is a very interesting concept, and I am anxious to hear a dive report.

Greg
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SurfLung
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First Name: Eben
Location: Alexandria, MN
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Re: My Trieste actually breathes wonderfully now

Thu Sep 03, 2020 9:40 am

Neat project! I've been hearing of the different techniques to make the Trieste work well... And now my mind is on the lookout for an available Trieste to buy and fix up myself. I've heard various different approaches to the diaphragm. What did you do with the diaphragm on this one?
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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ScubaLawyer
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Joined: Thu Apr 08, 2010 11:25 am
First Name: Mark
Location: Laguna Beach, CA

Re: My Trieste actually breathes wonderfully now

Thu Sep 03, 2020 12:56 pm

SurfLung wrote:
Thu Sep 03, 2020 9:40 am
What did you do with the diaphragm on this one?
I bought a new silcone diaphragm from this guy named Rob at The Scuba Museum. :)
"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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ScubaLawyer
Master Diver
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Joined: Thu Apr 08, 2010 11:25 am
First Name: Mark
Location: Laguna Beach, CA

Re: My Trieste actually breathes wonderfully now

Thu Sep 03, 2020 12:57 pm

Completed my Modified Trieste rebuild. Sounds like a sports car engine when the venturi kicks in. :)

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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Vancetp
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Joined: Tue Oct 04, 2016 7:26 pm
First Name: Phillip
Location: Belmont CA

Re: My Trieste actually breathes wonderfully now

Thu Sep 03, 2020 8:14 pm

That lever is a PITA to make. I've been fooling around with levers lately, and have gone from this:

ImageIMG_4769 by Vancetp, on Flickr

To this:

ImageIMG_5400 by Vancetp, on Flickr

To this:

ImageTriestereprosm1 by Vancetp, on Flickr

The Trieste type bend at the diaphragm end isn't easy, but the double bend at the body end is no joke to make. I think it is a good thing, because it raises the whole lever upward and lessens the needed lever bend up to meet the diaphragm. It also helps to keep the other second stage parts from interfering with the diaphragm. I'm working on an easier method of making them. Lots to do.....

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Herman
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Re: My Trieste actually breathes wonderfully now

Fri Sep 04, 2020 6:40 am

Phillip, you are getting really good at levers, nice job.
Herman

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Vancetp
Master Diver
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Joined: Tue Oct 04, 2016 7:26 pm
First Name: Phillip
Location: Belmont CA

Re: My Trieste actually breathes wonderfully now

Sat Sep 05, 2020 11:55 am

Thanks, Herman! Don't mean to hijack this thread, but I thought people might be interested. I'm thinking about incorporating the set screw idea in my second stages, as well.

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SurfLung
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First Name: Eben
Location: Alexandria, MN
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Re: My Trieste actually breathes wonderfully now

Thu Sep 10, 2020 10:03 am

Contributing is NOT hijacking! Thanks Mark, Bill, Vance, SwimJim, and everyone else for sharing so much good information on the Trieste. You got the old FEVER going in me again and I've been shopping around until I finally bought Allan's Trieste II that he posted for sale on this forum. This one was tuned up and upgraded (hoses etc.) by Greg Barlow awhile back. Allan never dove it though. So, I'm excited to check it out. I never was interested in the Trieste because I had heard it was a hard breather... And I like regulators I can DIVE with.

THIS THREAD... Is very encouraging and I'm looking forward to getting my new Trieste tuned up to good diving condition!
SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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