High pressure tanks with older regs

[DA Aquamaster]

Buy an old Conshelf XII off E-bay and use the yoke off it. The Mistral, RAM and Conshelf XII all use a similar looking yoke retainer nut with the same external diameter around which went unthreaded yokes with the same internal diameter. The heavier 4000 psi rated Conshelf 12 yoke should fit just fine on the RAM nozzle.

 

[Luis H]

Buy an old Conshelf XII off E-bay and use the yoke off it. The Mistral, RAM and Conshelf XII all use a similar looking yoke retainer nut with the same external diameter around which went unthreaded yokes with the same internal diameter. The heavier 4000 psi rated Conshelf 12 yoke should fit just fine on the RAM nozzle.

The Mistral, the Conshelf and the Phoenix RAM all share the same threads were the yoke or the yoke nut threads on to. The thread size is 13/16" - 20 UNEF (about 0.78" OD x 20tpi). They can all use the modern Conshelf threaded yoke or the yoke with the nut from the Mistral or a few other regulators (even the yoke nut from the Titan). The barrel OD on all this yoke nuts is about 0.937 inches.

On the other hand, the OD on the RAM nozzle 1st stage body is about 0.87 inches. The yoke on the RAM is not at all compatible with the Mistral or the other regulators mentioned. And a Mistral yoke has way too much play in a RAM 1st stage nozzle.

We have tried interchanging yokes and the yoke ID is not close. Bryan had yokes made specifically for the Mistral and he had NOS RAM yokes (the Titan yoke would have looked funny in a Mistral and it wouldn't have been long enough for a banjo fitting).

The 1973 heavy yoke RAM is so desirable and valuable because no other of the shelf yoke will fit a RAM. The closest heavy yoke is a threaded inside yoke like the Conshelf and then have it machined for a RAM. Dan at VSS did something similar using some threaded DACOR yokes and had them machined.

 

[Nemrod]

And I love my NOS heavy yoke RAM. N

 

[WD8CDH]

The Mistral, the Conshelf and the Phoenix RAM all share the same threads were the yoke or the yoke nut threads on to. The thread size is 13/16" - 20 UNEF (about 0.78" OD x 20tpi). They can all use the modern Conshelf threaded yoke or the yoke with the nut from the Mistral or a few other regulators (even the yoke nut from the Titan). The barrel OD on all this yoke nuts is about 0.937 inches.

On the other hand, the OD on the RAM nozzle 1st stage body is about 0.87 inches. The yoke on the RAM is not at all compatible with the Mistral or the other regulators mentioned. And a Mistral yoke has way too much play in a RAM 1st stage nozzle.

We have tried interchanging yokes and the yoke ID is not close. Bryan had yokes made specifically for the Mistral and he had NOS RAM yokes (the Titan yoke would have looked funny in a Mistral and it wouldn't have been long enough for a banjo fitting).

The 1973 heavy yoke RAM is so desirable and valuable because no other of the shelf yoke will fit a RAM. The closest heavy yoke is a threaded inside yoke like the Conshelf and then have it machined for a RAM. Dan at VSS did something similar using some threaded DACOR yokes and had them machined.

Hi Luis,

By Mistral, do you mean the new Mistral (Titan first stage)? I am fairly sure that the vintage USD Mistral body thread is 3/4" (probably 3/4x 20) and the hole in the inhalation can is only 25/32, too small to accept a 13/16 threaded body. And with the nut, it is still smaller that the DA or RAM first stage. The center hole in the Vintage Mistral yoke is too small to put a 2 stage nozzle through and the center hole of the DA or RAM yoke is too sloppy on a vintage USD Mistral. So there are at least two different hole sizes in the vintage unthreaded USD yokes.

Luis, if you have a vintage USD Mistral body around, could you measure the body thread and yoke nut OD for me?

For threaded yokes, so far, I have only seen 13/16 x 20 on USD regulators.


Do I have this correct for un-threaded yokes?

The MODERN yoke nut OD is about 0.937 inches.

The DA and RAM nozzle OD is about .87 inches.

vintage USD Mistral yoke nut OD is somewhat less than .87 inches.

 

[WD8CDH]

I am looking at investing in some new tanks and I wonder if the Conshelf series SH regs can take 3500psi pressures?

Which model Conshelf do you have? (XIV, 21, 30, SE......?) Most made in the last at least 30 years can handle 3500 psi.

One thing that makes a very big differance in stress and strain on the yoke is the valve. Older valves and most DIN inserts use a fat #112 o-ring. Most newer K only valves use the smaller, thinner #014 o-ring. The larger surface area of the fat o-ring exerts more pressure on the yoke. The smaller o-ring at 3000psi puts less stress on the yoke than the large o-ring at 2475psi.

 

[Luis H]

Whenever I talk about the New Mistral I always call it the New Mistral. I am referring about the vintage Mistral.

I have measured it many times including yesterday. I can thread a Conshelf yoke into a vintage Mistral and it is a perfect fit.

The Titan Yoke nut will also fit the Vintage Mistral perfectly.

Do I have this correct for un-threaded yokes?

The MODERN yoke nut OD is about 0.937 inches.

The DA and RAM nozzle OD is about .87 inches.

vintage USD Mistral yoke nut OD is somewhat less than .87 inches.

The first two statements are correct.
The last statement is not, the vintage Mistral can use a modern yoke.

I have measured it many times including yesterday. I can thread a Conshelf yoke into a vintage Mistral and it is a perfect fit.

The Titan Yoke nut will also fit the Vintage Mistral perfectly.


Keep in mind that all this designs are driven by the same tank valve standards. The O-ring size ID is 1/2". All regulators have to start with that dimension and build out from their. The difference comes if they are using a yoke nut (vintage Mistral, Titan, some Conshelf, etc.) or a removable yoke adapter or nozzle (RAM).

The Scubapro Mk-5 and the newer flow through piston regulators all have a removable yoke adapter. I will have to check and see if their yoke fits a RAM. It is very likely to be very close.

 

[jbrians]

Which model Conshelf do you have? (XIV, 21, 30, SE......?) Most made in the last at least 30 years can handle 3500 psi.

One thing that makes a very big differance in stress and strain on the yoke is the valve. Older valves and most DIN inserts use a fat #112 o-ring. Most newer K only valves use the smaller, thinner #014 o-ring. The larger surface area of the fat o-ring exerts more pressure on the yoke. The smaller o-ring at 3000psi puts less stress on the yoke than the large o-ring at 2475psi.

My regs include 3 DAAM, 1 RAM (heavy yoke) and 1 Phoenix/DA. I have picked up 2 Conshelf 21S in order to dive with a newer crowd who won't let me play unless I have an oct/BCD and the rest of the PoliticallyCorrect, PADI approved gear. I figured it wasn't worth fighting if I was going on an organised trip. Who wants to be left on the dock because the Boat operator/DM is ignorant of all of the ways to skin a cat?

If I was to rephrase the question, I would like to get 2 tanks the same that will allow me to play with the modern crowd who are using high capacity tanks to get the last minute of bottom time but also be able to dive in a minimalist fashion with my older favourite gear without having weight/bouyancy issues. For example, I wouldn't want to be trying to use a HP 130 diving without a BC in a 3mm wetsuit.

Getting fills at some of the LDS can be tricky as some have it in for any old tank including 72's and none of them are open to negotiation while standing at the fill station. Buying a new tank was one option that was offered me in order to get air. Fortunately, the AL80 was very easy to sell after that weekend. (I have an older style plastic back pack that easily adjusts between a 6.9 and up to an 8 inch tank).


the LP95's look like a possible choice.

 

[WD8CDH]

Hi Luis,
Thanks for the thread measurements. Have you had a chance to compare the yoke hole diameter differences. I am referring to the statement about incompatibility from here:

Single Stage Long Yoke [Single Stage Yoke] - $40.00 : Vintage Double Hose!, Your online source for all things related to vintage diving

If they truly are different, then which one has the same diameter hole as a modern unthreaded yoke?

 

[WD8CDH]

My regs include 3 DAAM, 1 RAM (heavy yoke) and 1 Phoenix/DA. I have picked up 2 Conshelf 21S in order to dive with a newer crowd who won't let me play unless I have an oct/BCD and the rest of the PoliticallyCorrect, PADI approved gear. I figured it wasn't worth fighting if I was going on an organised trip. Who wants to be left on the dock because the Boat operator/DM is ignorant of all of the ways to skin a cat?

If I was to rephrase the question, I would like to get 2 tanks the same that will allow me to play with the modern crowd who are using high capacity tanks to get the last minute of bottom time but also be able to dive in a minimalist fashion with my older favourite gear without having weight/buoyancy issues. For example, I wouldn't want to be trying to use a HP 130 diving without a BC in a 3mm wetsuit.

Getting fills at some of the LDS can be tricky as some have it in for any old tank including 72's and none of them are open to negotiation while standing at the fill station. Buying a new tank was one option that was offered me in order to get air. Fortunately, the AL80 was very easy to sell after that weekend. (I have an older style plastic back pack that easily adjusts between a 6.9 and up to an 8 inch tank).


the LP95's look like a possible choice.

Personally, I don't think any 8" tank looks vintage. The length of the HP 120 also looks wrong to me for the vintage style. I think the HP100 looks closest to vintage 72 tanks, have reasonable buoyancy and give you reasonable capacity without a "cave fill". Most LP tanks won't have any better buoyancy characteristics. Double HP65s or HP80s look somewhat like double vintage 44s and with a vintage two post Sherwood manifold will satisfy the redundant air supply if needed.

Your Conshelf 21s, Phoenix, of course and heavy yoke RAM will probably handle HP tanks with no problem on any valve but your DAAMs would probably be served better with small o-ring valves.

I have used the Conshelf XIV extensively on Sherwood small o-ring valves at 4,500psi with no problems. 3442psi is just a walk in the park.

 

[jbrians]

Personally, I don't think any 8" tank looks vintage. The length of the HP 120 also looks wrong to me for the vintage style. I think the HP100 looks closest to vintage 72 tanks, have reasonable buoyancy and give you reasonable capacity without a "cave fill". Most LP tanks won't have any better buoyancy characteristics. Double HP65s or HP80s look somewhat like double vintage 44s and with a vintage two post Sherwood manifold will satisfy the redundant air supply if needed.

Your Conshelf 21s, Phoenix, of course and heavy yoke RAM will probably handle HP tanks with no problem on any valve but your DAAMs would probably be served better with small o-ring valves.

I have used the Conshelf XIV extensively on Sherwood small o-ring valves at 4,500psi with no problems. 3442psi is just a walk in the park.

Which makes me think of something else... A short fill, of say 3000psi or less, would only give me about 85cu/ft. My SAC rate is nothing to brag about...unless it's first out wins!
I appreciate the thought going into the replies too, btw.