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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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SurfLung
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Trieste Update

Thu Feb 04, 2021 10:34 am

The SAGA of my Trieste...
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- Last Fall I bought a Trieste from Simonbeans and reported on it in this forum. I dove it twice... Once down to 20 ft in the lake out front and once down to about 120 ft in Fortune Pond. I found that it breathed surprisingly nice... Which surprised me considering all I had heard about the Trieste being a hard breather due to it's small and dome shaped diaphragm.
- Well, I couldn't leave well enough alone and wanted to try out the Scuba Museum's large diaphragm Trieste cans. This required me to take my Trieste apart and transfer the guts to the larger cans. And in the process, I discovered that my Trieste had been fitted with a very sensitive, handmade silicone diaphragm. No wonder it breathed so nice! BUT... The previous installation had rolled one edge under causing it to crease and become un-useable for re-installation. Not to mention, it was just barely sealed on that edge and I'm considering myself lucky it didn't let go when I was diving it. Bill said the Trieste diaphragms were notoriously hard to position during installation... A fact I would experience personally, later.
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- I sent this photo to AntiqueDiver and asked if he recognized it. Bill was making diaphragms for the Trieste several years back. He used a nylon stocking for reinforcement, a large fender washer, and liquid silicone. He said it looked like one of his. Allan apparently made some of the same design so it might have been his, too. It's kind of fun to know the history of this reg includes three of my vintage diving friends, Allan, Greg, and Bill.
- So I ordered a new Trieste diaphragm from the Scuba Museum and in the meantime tried installing the guts in the large cans with a large silicone diaphragm. This I dove a couple of weeks ago in 12 feet of water at the local pool (its winter here). Breathing ease was excellent. I tried it swimming hard and it fed me plenty of air... AS much as I needed. BUT, I didn't like the idea that I couldn't put a Trieste label on it (none of the stick-on labels say Trieste). AND ANYWAY, I wanted to keep my Trieste as original as possible. So I planned to take the guts back out and reassemble it. The new diaphragm arrived. It's soft and the dome shape isn't as pronounced as expected. I had high hopes for it.
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- Next, I spent two evenings trying to install the new diaphragm in the original Trieste cans. No matter what I did, it would end up either misaligned or would pop loose with a hard inhale. At this point, I'm pretty sure the band clamp isn't squeezing it tight enough. And it's screwed as tight as it will go. I'm beginning to think the handmade diaphragm might have been secured with liquid silicone... glued in place.
- About this time I remembered that Allan sells replacement regulator labels and he has them for the Treste. They're a little larger in diameter than the label recess in ScubaMuseum's cans. But it occurred to me that I might glue one of these labels over the label recess with silicone sealant. The sealant will fill the label recess behind the label with good enough rigidity. And that appears to have worked quite nicely.
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- Nothing is broken or modified (yet) in the original Trieste cans configuration so I can still restore it when I want. I'm going to think on solutions for my diaphragm installation issues... Ask around, get advice, suggestions, etc. Maybe even make my own diaphragm. Meanwhile, I am very happy with how the large plastic can conversion has turned out. Here are some more photos:
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SurfLung
The Freedom and Simplicity of Vintage Equipment and
Vintage Diving Technique are Why I Got Back Into Diving.

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simonbeans
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Re: Trieste Update

Thu Feb 04, 2021 1:12 pm

The story of the Trieste is rather long and convoluted. Many of us feel the smaller, dome shaped diaphragm was the reason for the lack of interest in it over the years. As most everybody knows, the Trieste used essentially the same 1st stage as the Titan series of single hose regulators. On the body of the first stage of the single hose was a plastic threaded plug that once removed could take the second stage of the Trieste. (Smart engineering move?) Thus a smart young vintage diver started playing with designs of a second stage to make the Titan into a double hose regulator. Possibly this idea was noticed by another diving semi-genius and a second stage was developed. Seems the main issue with producing a second stage to fit the Titan body was the threads. Did Voit-Swimaster at the time use a common thread? Oh no. So it took another diving mastermind/machinist to make the second stage based on the genius design with the ideas of the young vintage diver. Following along? So now a double hose with the associated ports of the Titan/Trieste was made, but alas, no cans to put it in. The stage bodies would fit into the USD double hose cans so that was a problem sort of solved. Along came a diver/supplier who had reproduced a plastic can for the Jet-Airs, or Mistrals or other Voit regulators that used them. By having the yoke side can cut to the dimensions of the now Titan/Trieste body, a new regulator could be had and Wa-La, it was.
About this time I was really into having all sorts of regulators so with the help of the aforementioned souls, I acquired all the components to make up a Titan/Trieste/Whatever. Instead of using the plastic bodies (I am cheap) I had a Nemrod Snark III body which fit the T/T guts and it now could have a name. Back to the genius, who dubbed it the PEGASUS.
Here it is:
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I dove it once on one of the Sand Dog events. It has sat on a shelf ever since.
Check out my website: www.vintagescubastuff.com

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antique diver
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Re: Trieste Update

Thu Feb 04, 2021 4:20 pm

Thanks, Allan, for the photo of Trieste body in the Nemrod cans. Now I know what I can do with some of my extra bodies and cans like that. :)
Never thought about using that old gutted Nemrod with an extra Titan body as a fun new wildcat rig. Luckily I never throw any obscure old stuff out.
The older I get the better I was.

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ScubaLawyer
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Re: Trieste Update

Fri Feb 05, 2021 10:59 am

Very cool Allan! It was fun to mentally fill in the "genius" and "semi-genius" names as I read through your post.

Mark
"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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Herman
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Re: Trieste Update

Fri Feb 05, 2021 11:21 am

The threads in the Voit are a fairly common, 5/8-24 the real pain in the rear was the USD regs.
There is another fairly common 5/8 thread that is used a lot in the gun industry 5/8-28 and at first glance that is what it appeared to be and one would have assumed USD would have use a common thread. Problem was, it just didn't seem to fit correctly. With only a few threads on the second stage and not too many more in the body, accurately measuring them was difficult at best, To make matters worse, there was a much less common but still a standard thread of 5/8-27. Being off 1 TPI is not much and it takes a number of threads engaged before the error adds up enough that parts start to bind which is what appeared to be happening when second stages with more threads were used. It took a lot of examples and high power magnification to finally decide the threads were in fact the less common 5/8-27 in USD regs.
Herman

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SurfLung
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Re: Trieste Update

Fri Feb 05, 2021 11:28 am

What Goes Around Comes Around...
- It's always fun to get some of the original Vintage guys to talk about what kind of stuff they did in the early days. I remember some kind of contest here at VDH where I sent in my ideas for a label design for the Pegasus... I never knew what a Titan/Trieste hybrid was. I think I used a Pegasus horse graphic from an old Texaco gas station advertisement. Anyway, I must have got into VDH just after all of the major enthusiasm happened.
- I got an email this morning from Phil Yeater who offered me one of his Super Trick Titan II mods... So I can use it in my plastic cans and restore my Trieste to it's original cans and diaphragm. I'll do some photos, dive review, and write-up on that when I get it all set up. Phil's got some neat ideas.
- Okay now back to the original, small, dome shaped, reproduction diaphragm and my problems getting it installed properly and securely. I am thinking if I secure it to the top can with double sided tape, it will leave the bottom side clean for a good seal and also keep it aligned while the band clamp is being installed and tightened. What do you guys think of this idea?
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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: Trieste Update

Fri Feb 05, 2021 11:52 am

SurfLung wrote:
Fri Feb 05, 2021 11:28 am
What Goes Around Comes Around...
....
- Okay now back to the original, small, dome shaped, reproduction diaphragm and my problems getting it installed properly and securely. I am thinking if I secure it to the top can with double sided tape, it will leave the bottom side clean for a good seal and also keep it aligned while the band clamp is being installed and tightened. What do you guys think of this idea?
Keeping the diaphragm aligned during assembly is a frustrating issue with the Trieste, but it can be done by holding the cans very firmly in place and inspecting it all during the clamp installation... haha, easier said than done, as all you Trieste owners know! This is the main reason that I don't open my Trieste very often. Gotta be a better way.

The tape idea sounds like it might help, and it also made me think of another way to experiment with. I think I'll try using a thin coating of silicone sealant to either can rim (or to one rim of diaphragm) and stick the diaphragm in place on that one can until it cures. Then, still being diligent to hold the cans firmly together, install the stubborn clamp. First I'll experiment a bit with it on a scrap diaphragm to see if removing the silicone from the rubber and the metal is reasonably easy on a later opening.

I'm also thinking of making a simple press or clamp with which to hold the cans snugly together while applying the band clamp. I haven't thought that out yet, but I think that may be an easier way to achieve results than just holding the cans by hand.

What I would really prefer is to have a two-piece band clamp like that found on the good-ole Scubapro second stages. :D
The older I get the better I was.

James
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Re: Trieste Update

Fri Feb 05, 2021 3:08 pm

antique diver wrote:
Fri Feb 05, 2021 11:52 am
What I would really prefer is to have a two-piece band clamp like that found on the good-ole Scubapro second stages. :D
I've made a clamp just like that for my Most of A Scuba (HW Scuba that was missing parts).... works a treat. I'm still ironing out problems with my 3d printer, but once it's up I could adjust the design to suit the Trieste for you. Shoot me a message and I'll get measurements from you to model it up.

Respectfully,

James

edit to add:

Image

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antique diver
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Re: Trieste Update

Fri Feb 05, 2021 3:46 pm

James wrote:
Fri Feb 05, 2021 3:08 pm
antique diver wrote:
Fri Feb 05, 2021 11:52 am
What I would really prefer is to have a two-piece band clamp like that found on the good-ole Scubapro second stages. :D
I've made a clamp just like that for my Most of A Scuba (HW Scuba that was missing parts).... works a treat. I'm still ironing out problems with my 3d printer, but once it's up I could adjust the design to suit the Trieste for you. Shoot me a message and I'll get measurements from you to model it up.

Respectfully,

James

edit to add:

Image
I know next to nothing about 3D printing, but you must feel like the end result is tough enough to handle the stress of being clamped snugly about the cans. Ever have any problems with that?
The older I get the better I was.

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antique diver
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Re: Trieste Update

Fri Feb 05, 2021 4:00 pm

James, thanks for the interest. I just sent you an email.

Another thought that I just had is I may try making 6 or 7 small individual clamps placed around the T's cans in the same manner as the old USD crimps are done. This would use something like Delrin with small SS machine screws to tighten them down, but it may not look so good. :? I like your idea better.
The older I get the better I was.

James
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Re: Trieste Update

Fri Feb 05, 2021 5:02 pm

Bill,

Email answered... and, somewhat ironically, I have a RAM currently held together with seven individual clamps held together with screws. I stole the idea from an old ad for metal ones, and printed a set! I posted the files for them on Thingiverse; https://www.thingiverse.com/thing:4475977/files

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ScubaLawyer
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Re: Trieste Update

Fri Feb 05, 2021 9:36 pm

I finally figured out that if you, (1) put the bottom Trieste can in a vice (with appropriate padding), (2) place the band clamp over the lip of the bottom can so it is below the level of the lip all the way around, (3) place your diaphragm on, (4) place your top (exhaust) can on top of that so it makes a good seal, (5) press down on the top can with both thumbs to hold the diaphragm in place, then (6) pull the band clamp up and over the two can lips with your remaining fingers on each hand, it falls into place quite readily. Took me some practice but I can do it easily now. All other methods I tried made me drink heavily and cuss out the diaphragm as if it was its fault. :)
"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: Trieste Update

Sat Feb 06, 2021 1:16 am

ScubaLawyer wrote:
Fri Feb 05, 2021 9:36 pm
I finally figured out that if you, (1) put the bottom Trieste can in a vice (with appropriate padding), (2) place the band clamp over the lip of the bottom can so it is below the level of the lip all the way around, (3) place your diaphragm on, (4) place your top (exhaust) can on top of that so it makes a good seal, (5) press down on the top can with both thumbs to hold the diaphragm in place, then (6) pull the band clamp up and over the two can lips with your remaining fingers on each hand, it falls into place quite readily. Took me some practice but I can do it easily now. All other methods I tried made me drink heavily and cuss out the diaphragm as if it was its fault. :)
Good procedure. Trying to hold the reg in one hand and install clamp with the other detracts from my happiness. For those without a vise, I suggest attaching reg to a tank.
The older I get the better I was.

swimjim
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Re: Trieste Update

Sat Feb 06, 2021 11:33 am

I do mine on the tank valve. That way it's a two handed process. You can easily put the intake end of a hose set on it and check the seal and function when everything is tightened up.

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Vancetp
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Re: Trieste Update

Sat Feb 06, 2021 1:54 pm

I use the ring on the underside method for MR12s, too. It might be the only way for the models with the thick plastic cover. Also, you can clamp the boxes together with a small woodworking clamp.

Image (Yep, that's a Titan II in the Trieste boxes.)

Some of you have already seen this. I also made second stages for the Titan IIs, and set one up in USD single stage boxes. One advantage to making the second stage body is aligning the jet with the intake horn. A Trieste in full size boxes doesn't line up well.

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I started out using FX boxes but didn't like two things: can't use a DBE, and there's no easy way to keep the first stage from rotating in the box. If the box turns even a little, performance is degraded a lot.

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