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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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stefeyme
Lung Diver
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Joined: Sat Jul 18, 2015 3:52 am
First Name: Stephane
Location: Valencia Spain
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US Divers Royal Mistral: chronicle of a death foretold

Sun Sep 02, 2018 7:20 am

Hi everyone, this is my last post about USD Royal Mistral.

I hope you'll like it!

https://vintagescubadiving.com/us-diver ... -foretold/

Cheers!
US DIVERS ROYAL MISTRAL #1715 - 00137.jpg
US DIVERS ROYAL MISTRAL #1715 - 00133.jpg
US DIVERS ROYAL MISTRAL #1715 - 00113.jpg
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luis
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First Name: Luis
Location: Maine

Re: US Divers Royal Mistral: chronicle of a death foretold

Sun Sep 02, 2018 7:57 am

Very nice pictures. I can't wait to read the article.

I like the sub-title: Royal Mistral: another case of "Better is the Enemy of Good Enough"

Well actually it is going to have to wait, I am going diving.
Luis

Buceador con escafandra autónoma clásica.

jrltenn
Master Diver
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Joined: Sat May 10, 2014 10:11 pm
First Name: Joshua
Location: Jonesborough TN

Re: US Divers Royal Mistral: chronicle of a death foretold

Sun Sep 02, 2018 9:47 am

Thank you. I enjoyed that article very much.

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antique diver
Master Diver
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Joined: Sun Dec 10, 2006 12:50 pm
First Name: Bill
Location: North-Central Texas

Re: US Divers Royal Mistral: chronicle of a death foretold

Sun Sep 02, 2018 11:50 am

Stephane, that was a very interesting and informative article. Nicely illustrated too. Thanks!
The older I get the better I was.

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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: US Divers Royal Mistral: chronicle of a death foretold

Sun Sep 02, 2018 11:57 am

Great write-up ! Thanks for preserving DH history. 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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Drado
Master Diver
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Joined: Mon Feb 07, 2011 6:11 am
First Name: Eduardo
Location: Manila, Philippines

Re: US Divers Royal Mistral: chronicle of a death foretold

Sun Sep 02, 2018 7:48 pm

Great read! Thanks!
_______________________________
Ed

swimjim
Master Diver
Posts: 1582
Joined: Thu Mar 23, 2006 12:28 am
First Name: Jim
Location: Belgium WI

Re: US Divers Royal Mistral: chronicle of a death foretold

Mon Sep 03, 2018 9:22 am

Nice write up! Thank you for your efforts! :D

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luis
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Re: US Divers Royal Mistral: chronicle of a death foretold

Mon Sep 03, 2018 1:26 pm

Hi Stephane
The Sleeve
This spare part is meant to guide the poppet perfectly straight onto the disc of the retainer to provide sealing.

The purpose of the sleeve is to provide a mechanical support to the balancing chamber (not a guide). The balancing chamber has to be mechanically supported for it to work.

The pressure thrust (force) on the back surface of the balancing chamber has to be transferred to the structure. Otherwise, (if the balancing chamber was floating) the tank pressure “force” would press on the back of the seat through the spring.

If the sleeve was not there (if it was not installed) the regulator would seem to work OK, but it would not be balanced. The tank pressure would act on the back of the seat via the now floating balancing chamber and it would increase the spring force on the back of the seat.

The RAM, Conshelf, etc. doesn’t need this sleeve because the first stage body is machined with the same step (perimeter shelf) built right into the body. In essence the sleeve is just machined right into the body.

Mechanically locking the balancing chamber is extremely important if you want the regulator to be balanced.


BTW, the cone is self aligning. That conical seat will try to align itself into the orifice. Adding any kind of a guide to a conical seat can be very counterproductive. The guide would have to be perfectly concentric with the orifice. A conical seal like this cannot tolerate any misalignment.


Conical poppet seats like this one have been tried by Poseidon and Mares, with some success , or at least partial success. I used to service a lot of Poseidon Cyklon 300 first stages back in the 70’s and they were OK. Sometimes the seal was very reliable, but at times, I have had to replace a number of soft seals to get one to work.


The conical poppet on a soft orifice seat seems like a good idea, but in my experience, it is not very forgiving and therefore I found that it’s reliability is hard to reproduce, it is not consistent.
Luis

Buceador con escafandra autónoma clásica.

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stefeyme
Lung Diver
Posts: 59
Joined: Sat Jul 18, 2015 3:52 am
First Name: Stephane
Location: Valencia Spain
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Re: US Divers Royal Mistral: chronicle of a death foretold

Tue Sep 04, 2018 10:56 am

luis wrote:
Mon Sep 03, 2018 1:26 pm
Hi Stephane
The Sleeve
This spare part is meant to guide the poppet perfectly straight onto the disc of the retainer to provide sealing.

The purpose of the sleeve is to provide a mechanical support to the balancing chamber (not a guide). The balancing chamber has to be mechanically supported for it to work.

The pressure thrust (force) on the back surface of the balancing chamber has to be transferred to the structure. Otherwise, (if the balancing chamber was floating) the tank pressure “force” would press on the back of the seat through the spring.

If the sleeve was not there (if it was not installed) the regulator would seem to work OK, but it would not be balanced. The tank pressure would act on the back of the seat via the now floating balancing chamber and it would increase the spring force on the back of the seat.

The RAM, Conshelf, etc. doesn’t need this sleeve because the first stage body is machined with the same step (perimeter shelf) built right into the body. In essence the sleeve is just machined right into the body.

Mechanically locking the balancing chamber is extremely important if you want the regulator to be balanced.


BTW, the cone is self aligning. That conical seat will try to align itself into the orifice. Adding any kind of a guide to a conical seat can be very counterproductive. The guide would have to be perfectly concentric with the orifice. A conical seal like this cannot tolerate any misalignment.


Conical poppet seats like this one have been tried by Poseidon and Mares, with some success , or at least partial success. I used to service a lot of Poseidon Cyklon 300 first stages back in the 70’s and they were OK. Sometimes the seal was very reliable, but at times, I have had to replace a number of soft seals to get one to work.


The conical poppet on a soft orifice seat seems like a good idea, but in my experience, it is not very forgiving and therefore I found that it’s reliability is hard to reproduce, it is not consistent.
Thanks Luis for your feedback! I really appreciate it. I'll change my post to reflect that.
Many thanks again
Cheers!

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