Vancetp
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First Name: Phillip
Location: Belmont CA

Conshelf Conversion to Double Hose

Tue Apr 21, 2020 2:22 pm

I've been working on another DH conversion for a while now. It has gone through some revisions and has required more custom machining than I wanted due to the changes. I thought maybe this would be entertaining for some of you while we are hunkered down. The whole sordid story is chronicled on another site, but I'm going to spare you lot from all the agonizing with this condensed version.

I have always thought that using a single hose first stage for a DH conversion would work pretty well. I ended up using a Conshelf VI first stage for a couple of reasons, but the main one is that I have several left over from my experiments with making a balanced single stage valve out of the Conshelf guts and a Healthways Scuba valve body. But that's another adventure.

There are several issues to deal with in this conversion:

A top can must be found and irrevocably modified.
There needs to be a way to connect the first stage body to the can.
There needs to be a remote second stage.
There needs to be a way to supply LP air to the second stage.
There needs to be a lever system that will work with a DH diaphragm.
There should be a way to multiply the Conshelf's single LP port.

I found an orphan Mistral top can that is fairly funky to cut up. To attach the 1st stage to the can, I machined the HP diaphragm retainer/IP adjuster and threaded it to accept a large retaining nut. It is installed with a rubber gasket like the Mistral valve.

ImageIMG_4877 by Vancetp, on Flickr

I used a modded single hose second stage body that has an integral and adjustable LP hard seat/orifice out of an old Sportsways second stage. I also made a soft seat/lever retainer out of brass and made a stainless lever, much like my Dacor conversion uses. The idea was to supply LP air to the second stage via a short tube. I actually accomplished this, and it worked.

ImageIMG_4898 by Vancetp, on Flickr

ImageIMG_5181 by Vancetp, on Flickr

ImageIMG_5192 by Vancetp, on Flickr

There are several reasons why I didn't like this much, mostly due to the difficulty in bending a brass tube in a sharp U bend and the kludgy look of the too long tube I came up with as a first attempt. I might have been able to get the short tube I wanted with a few tries, but I don't like the connectors either.

The next version is much cleaner.

[ImageIMG_5287 by Vancetp, on Flickr

Because I had already cut the top can for the second stage, I had to make a longer through-bolt for the splitter. I also had to machine the second stage body.

I still need to do some fiddling, but it does work well. The proximity of the second stage jet to the intake horn makes for good venturi action, which will probably need to be tamed a bit.

ImageIMG_5183 by Vancetp, on Flickr

No 50 Fathoms were harmed in this conversion! I only borrowed the bottom can for testing.

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antique diver
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Re: Conshelf Conversion to Double Hose

Tue Apr 21, 2020 3:52 pm

What a cool conversion! I'm impressed at your ingenuity.
I'll bet it beats the heck out of the USD's big failure of their new "Mistral" a few years back.
The older I get the better I was.

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Vintagediver
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Re: Conshelf Conversion to Double Hose

Tue Apr 21, 2020 3:56 pm

Phil, that's an interesting project you have going there, and now we know why you're called "Dr. Frankenreg"! :lol: Thanks for the interesting post.
Terry
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Vancetp
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First Name: Phillip
Location: Belmont CA

Re: Conshelf Conversion to Double Hose

Tue Apr 21, 2020 5:55 pm

antique diver wrote:
Tue Apr 21, 2020 3:52 pm
I'll bet it beats the heck out of the USD's big failure of their new "Mistral" a few years back.
I think it probably does easily. I have neither used one nor seen one of the new Mistrals in the flesh, but I've heard they are dogs. This conversion was not really inspired by that regulator, though. It was more influenced by my Soviet AVM-3 which is a second stage double hose regulator that runs off a remote first stage. That one is much more akin to a single hose setup with the first stage mounted pretty far away and connected by a long run of tubing.

That's another project: a chest mounted AVM-3 connected to a tank mounted first stage via a rubber LP hose. Ought to be fun. All I really need for that is a standard to metric adapter for the hose connection at the second stage, and a harness.

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ScubaLawyer
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Re: Conshelf Conversion to Double Hose

Tue Apr 21, 2020 6:24 pm

And here I thought I was hot s**t for being able to change out the o-ring on my '58 Mistral. :)

Good job Phil.
!
"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: Conshelf Conversion to Double Hose

Tue Apr 21, 2020 7:18 pm

ScubaLawyer wrote:
Tue Apr 21, 2020 6:24 pm
And here I thought I was hot s**t for being able to change out the o-ring on my '58 Mistral. :)

Good job Phil.
!
Well Mark, don't sell yourself short. You have to be pretty good just to change those Mistral orings without damaging them or hurting yourself. :?
The older I get the better I was.

swimjim
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Re: Conshelf Conversion to Double Hose

Tue Apr 21, 2020 7:47 pm

Original Mistral o ring change out = major league PIA. Ha. I dove the "new" Mistral. Not impressed. The original could blow it away performance wise. Not even close. Phil can build better double hosers than the new Mistrals. He has and I can testify to that... at least in shallow water. Mid may I'll be in upper Michigan taking the Dacor Olympic 2020 down past 100 feet. I have confidence that it will be a winner. I'll have a pony if not. Lol

Vancetp
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First Name: Phillip
Location: Belmont CA

Re: Conshelf Conversion to Double Hose

Tue Apr 21, 2020 8:24 pm

I'm looking forward to your test of the Olympic 2020. Please post any (good or bad, really!) review of the Dacor mod. If it doesn't perform, I'll need to revise. Don't know why it wouldn't be good at this point. There's nothing new about the second stage, and others like it work fine.

This Conshelf mod can pump out a lot of air, and has pretty aggressive venturi action. It is so much that it needs a DSV mouthpiece with an air deflector or some other method of throttling to keep air from rushing past the mp into the exhaust hose. The DSV works well, and no changes will be needed with one. With a standard USD mp, freeflow can be induced by a deep quick pull. I might have to drill one or two small holes opposite the big jets to tame it with the stock mp. But, for my kind of diving, I'll stick with the DSV and its deflector and open/close feature for surface swims.

Vancetp
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First Name: Phillip
Location: Belmont CA

Re: Conshelf Conversion to Double Hose

Sat Apr 25, 2020 1:24 pm

Thanks for the kind comments. This conversion was fun to make and I thought it would satisfy the whim to shoehorn a single hose 1st stage regulator into double hose cans.

But NO! Now I'm considering doing this with a piston type first stage.

It looks like there is at least one major difficulty with it though. The main reason this suggests itself is that a piston regulator bonnet could be easily modified to be the can retainer. But, the big problem with that is, most piston type first stages have a pretty long bonnet that would interfere with the diaphragm. I'd need to find a balanced first stage with multiple ports that has a short bonnet.

Any suggestions?

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captain
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Re: Conshelf Conversion to Double Hose

Sun Apr 26, 2020 10:20 am

Kind of hard to tell for sure in the picture but it appears the contact points of the 2nd stage lever are not inline with the center line of the diaphragm. if so it may have some effect on performance.
Captain

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antique diver
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Re: Conshelf Conversion to Double Hose

Sun Apr 26, 2020 2:15 pm

captain wrote:
Sun Apr 26, 2020 10:20 am
Kind of hard to tell for sure in the picture but it appears the contact points of the 2nd stage lever are not inline with the center line of the diaphragm. if so it may have some effect on performance.
I think it's the angle of view. I'm going to try lowering my desk chair. :?
The older I get the better I was.

Vancetp
Master Diver
Posts: 307
Joined: Tue Oct 04, 2016 7:26 pm
First Name: Phillip
Location: Belmont CA

Re: Conshelf Conversion to Double Hose

Mon Apr 27, 2020 10:52 pm

captain wrote:
Sun Apr 26, 2020 10:20 am
Kind of hard to tell for sure in the picture but it appears the contact points of the 2nd stage lever are not inline with the center line of the diaphragm. if so it may have some effect on performance.
Actually, you are correct. I have not yet made the lever for this regulator, which needs a somewhat longer lever arm. The pictured lever is for another conversion regulator, which has a second stage that is closer to the first stage than this one. I will post a pic of the new one, which is laid out, but not yet cut out because I can't find my hacksaw!

It's probably in the freezer with my shoes.... Or somewhere.

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