Update on my Trieste

[surflung]

The SAGA of my Trieste...

- Last Fall I bought a Trieste from Simonbeans and reported on it in the forums. 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.

- 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.

- 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.

- 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:

[vance]

Nice! Thanks for posting your projects. I like the label on the FX cans a lot.

I just got a pair of orphan Trieste boxes, and installed one of my Titan II conversions in them.







I used a reproduction diaphragm, and had a real hard time getting the thing in straight. If it's off by a little, it will suck right out of the boxes. This doesn't make me real confident in the regulator.

I found it easiest to use a clamp to hold the boxes in alignment while wrangling the ring clamp on. I also do this with HW Scubas and other boxes that don't lock in place.

[vance]

One thing to be aware of with Triestes mounted in FX boxes is that the second stage jet is not aligned well with the intake horn due to the difference in the circumference of the original and the FX boxes. This will affect performance.

Another thing to be aware of, is that the first stage is not held in position by any kind of pin or key in the top box. No matter how tight the ring nut is tightened, the box can rotate on the first stage due to handling, etc. When, not if, this happens, performance will be affected due to misalignment.

I made my Titan second stages with a jet that aligns with the intake horn on full size boxes. This makes a big difference. Unfortunately, the benefit can be canceled with an accidental rotation.

I am ruminating about a key system for the Trieste/Titan II/Dacor Olympic first stages. It isn't an easy fix, because the sealing surface, where the key/pin needs to be, is very thin.

However, until some solution is found, marking the box and the first stage to indicate alignment is a good idea. This needs to be checked before each entry into the water!

[SeaRat]

Feb 4, 2021 16:39:35 GMT -8 vance said:

O
...Another thing to be aware of, is that the first stage is not held in position by any kind of pin or key in the top box. No matter how tight the ring nut is tightened, the box can rotate on the first stage due to handling, etc. When, not if, this happens, performance will be affected due to misalignment...

I have not had this problem, but then again I have never removed the top box from the first stage either. The alignment problem I've seen for the original box is that the Allen head screw doesn't hold the nozzle exactly in the right orientation. The grove in the nozzle is larger than it needs to be, as it allows a small deviation of the nozzle so that it is not pointed directly down the intake hose. This is extremely important, as the nozzle itself doesn't have the normal amount of air going down the intake anyway (too much back into the box). This makes for a rather weak Venturi, unless modified (mine is modified, with one of the side holes slightly enlarged, but the rear, large hole completely blocked. This gives a powerful venturi, which requires either a baffle plate, or the VDH DSV mouthpiece.

IMG_1456 by John Ratliff, on Flickr
My Trieste II with the DSV mouthpiece.

Trieste II Mouthpiece by John Ratliff, on Flickr
My curved mouthpiece with a Healthways Gold Label baffle plate glued into it (the diameter at the center is the same and the baffle plate).

John

[vance]

I wasn't completely clear on what I said about this. Sorry!

This is what I meant:

The Trieste body in FX BOXES is not properly aligned to the intake horn, and there's no key tab in the FX box to keep the first stage in position. The Trieste, in its original boxes, is aligned perfectly.

The Trieste and the Titan II (which are identical except for labels) have a single tab cutout on the first stage, and a corresponding tab on the Trieste box for alignment.

[SeaRat]

Feb 4, 2021 18:29:29 GMT -8 vance said:

I wasn't completely clear on what I said about this. Sorry!

This is what I meant:

The Trieste body in FX BOXES is not properly aligned to the intake horn, and there's no key tab in the FX box to keep the first stage in position. The Trieste, in its original boxes, is aligned perfectly.

The Trieste and the Titan II (which are identical except for labels) have a single tab cutout on the first stage, and a corresponding tab on the Trieste box for alignment.

It wasn't your writing; it was my reading.

John

[surflung]

Feb 4, 2021 11:22:41 GMT -8 vance said:

...I used a reproduction diaphragm, and had a real hard time getting the thing in straight. If it's off by a little, it will suck right out of the boxes. This doesn't make me real confident in the regulator.

I found it easiest to use a clamp to hold the boxes in alignment while wrangling the ring clamp on. I also do this with HW Scubas and other boxes that don't lock in place.

I tried using a clamp too, but didn't have much luck. I thought up something new to try: Use double stick tape to secure the dome side to the top can. This leaves the bottom side clean to make a seal with the bottom can. I'll let you know if it works.

[surflung]

The Ultimate Solution...
- My original Trieste had one of the thin silicone duckbills in it and it was actually folded in half... Which may or may not have given some resistance to exhaling. I replaced this with the new molded silicone duckbill from The Scuba Museum.

- Then, I finally noticed that the new silicone diaphragm is a little smaller in diameter so that the ridge on it's circumference doesn't grab the groove on the can. So I went back to the original handmade diaphragm and I could see the folded under part was correctable by trimming off excess silicone sealant. I was able to secure it full width and all the way around the circumference to the top can with Loctite Ultra Gel... It's a super glue that works with rubber. I had to do a little at a time but got the whole thing totally secured so it wasn't going anywhere.

This is the original Bill Tucker ultra sensitive hand made diaphragm. You can see the new duckbill thru the diaphragm.

- With the diaphragm secure, it was easy to line up the top and bottom cans and fit the band clamp nice and tight.
- I put my thumb over the nozzle and sucked like heck on the inhale horn. It sucked down the diaphragm hard and held tightly without slipping, leaking, or sucking loose. Put the hoses on her and tried to hard suck it some more to see if I could get the diaphragm to suck loose or even leak. Nothing. We took it to the pool yesterday and dove it for about an hour. Works great. So my Trieste is restored to original cans and working great.

But the story doesn't end here... Phil has made me up a Titan conversion to put in my blue plastic cans. I'm looking forward to putting that together and I'll post the story here for those who might be interested

[vance]

Feb 8, 2021 9:16:51 GMT -8 surflung said:

The Ultimate Solution...
.....Then, I finally noticed that the new silicone diaphragm is a little smaller in diameter so that the ridge on it's circumference doesn't grab the groove on the can.

I noticed the same thing. I don't think the repro diaphragm works very well. It might be a carbon copy of the OEM diaphragm, but it needs improvement. It is slightly too small, and it doesn't have the big bead that fits into the box's groove.

I wonder if one could go to school on Bill T. (We're not worthy....), and add a bit of rim with a bead to the repro diaphragm using flowable silicone and the boxes for a mold? Will the stuff stick to the repro part well enough? 

I'm considering Bill T's work and thinking a Dacor diaphragm could be made with the nylon material and flowable silicone. I'll probably try one sooner or later.

If I can make diaphragms that work well (or somebody else does, hint, hint...), I would feel it is worth modding the Dacor R-3 with an improved second stage. I'm still thinking about it, but reluctant if there're no diaphragms.

Where's all the experimenters/makers out there? DACOR DIAPHRAGMS!!!  

[james1979]

Feb 8, 2021 16:11:39 GMT -8 vance said:

Feb 8, 2021 9:16:51 GMT -8 surflung said:

The Ultimate Solution...
.....Then, I finally noticed that the new silicone diaphragm is a little smaller in diameter so that the ridge on it's circumference doesn't grab the groove on the can.

I noticed the same thing. I don't think the repro diaphragm works very well. It might be a carbon copy of the OEM diaphragm, but it needs improvement. It is slightly too small, and it doesn't have the big bead that fits into the box's groove.

I wonder if one could go to school on Bill T. (We're not worthy....), and add a bit of rim with a bead to the repro diaphragm using flowable silicone and the boxes for a mold? Will the stuff stick to the repro part well enough? 

I'm considering Bill T's work and thinking a Dacor diaphragm could be made with the nylon material and flowable silicone. I'll probably try one sooner or later.

If I can make diaphragms that work well (or somebody else does, hint, hint...), I would feel it is worth modding the Dacor R-3 with an improved second stage. I'm still thinking about it, but reluctant if there're no diaphragms.

Where's all the experimenters/makers out there? DACOR DIAPHRAGMS!!!  

I hate to admit that I've been thinking about that..... I have the silicone, means to make a form...... I've thought of using a printed TPU lip embedded in the silicone as a sealing surface.

Dammit! lol.... send me a drawing with key measurements, or an unusable Dacor Diaphragm to measure, and I'll take a crack at it

Respectfully,

James

[vance]

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