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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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Bryan
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Re: USD Royal Mistral (again)

Mon Jan 18, 2016 6:26 pm

slonda828 wrote:I know we can figure something out together. My main concern is can we get enough seats working without having to hand make each one? I'm sick of hand making seats and stuff. I did that with the tilt valve regulators and the original calypso and whatnot.


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If it is indeed the seat that is the issue and Herman can replicate one with a good material ID and Durometer then reproduction of a seat that can be milled is easy to do and should be affordable. One that requires casting or molding is most likely out of the question.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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Ron
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Re: USD Royal Mistral (again)

Mon Jan 18, 2016 6:30 pm

Good to know. We could also mill a bushing that duplicates the original seat but uses a common commercial seating surface like something from Trident as well. What ever keeps it easy and cheap.


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luis
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Re: USD Royal Mistral (again)

Mon Jan 18, 2016 9:28 pm

The seat could possibly be machined out of a solid piece of synthetic material (Nylon, Delrin, or maybe Teflon), similar to the Poseidon Cyklon 300 seats. They were solid Nylon or Teflon (I believe Nylon).

The only major difference (and this is not a trivial difference) is that this seat has to support the pressure thrust transmitted by the sleeve. The pressure thrust is caused by the pressure differential in the balancing chamber. The pressure area is small, but the pressure differential is very high (tank pressure to IP differential).

I can easily calculate the maximum pressure thrust and determine if a fully synthetic seat can handle it, but it will probably be next weekend before I can get to it. The calculation is very easy, but I need to collect several dimensions and material properties (for the synthetic seat).

It would be very easy to machine a seat out of a solid piece of Nylon or Delrin, but I will strongly suggest not trying it without first confirming if it is structurally sound. This is not a candidate for a trial and error approach.
Luis

Buceador con escafandra autónoma clásica.

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Ron
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Re: USD Royal Mistral (again)

Tue Jan 19, 2016 12:51 am

Well, however I can help I will. I can do measurements, test dive prototypes, etc. If it were cheap enough to make it affordable for everyone to have as many as they would like, that would be a bonus too. The original mistral seat is a great example of that. Bryan makes those affordable enough that I put a new one in every service, where as I initially was sanding down seats on a piece of glass and doing other craziness to get stuff to work. Even if only a handful of people want this, it would be nice to share.

Luis, if you need anything from me just let me know.
The impossible missions are the only ones which succeed. -JYC

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Bryan
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Re: USD Royal Mistral (again)

Wed Jan 20, 2016 2:53 pm

Luis talked about this with Herman and then with me so we have the ball rolling. Let's see what Luis comes up with when he has the opportunity to put the pencil to it.

I can't help but think there is some other factor that caused so many of them to leak.....And I've never seen anything explaining why they were only made for two years.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

swimjim
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Re: USD Royal Mistral (again)

Wed Jan 20, 2016 9:11 pm

Royal Mistral's are like hens teeth. It would be really cool to resurrect them. On the other hand, if there was a way to convert a USD Mistral to a Royal...... Even with machining that would be tre' cool . This has been the most interesting thread to me in a very long time! :D

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Ron
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Re: USD Royal Mistral (again)

Thu Jan 21, 2016 12:34 am

I'm going to rant for a moment:

This is the core of what makes this place great. We really have a conflux of great ideas and highly skilled people here. It's what, literally, made SCUBA happen. People with new ideas and engineers with skills, in equal partnerships, are what have gotten us where we are with respect to this little community. Hell, last year a small group of engineers, machinists, and divers got a regulator made from scratch. I don't know... I do complicated things for a job and this place still impresses me. I don't say that because I assist Bryan with the site either. I've been here for 8 years, and despite how much of a struggle it has been I wouldn't trade it. I still get out of work for the weekend and enjoy diving vintage gear, even if the water is 52 degrees here.
The impossible missions are the only ones which succeed. -JYC

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Herman
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Re: USD Royal Mistral (again)

Thu Jan 21, 2016 8:23 am

I have been quietly keeping up with this but talking with Luis and doing some investigation in the background. Where I got it I have no idea but I have a RM hard seat which got me to wondering how I could make and test seat ideas and materials, I don' t have a RM and will not likely get one . And how to do you test the seat in a RM, since there are 3 leak points and no way other than listening to see if it's sealing.....then there is balancing...is it really balancing or not. Measuring lever pressure is the only way I can see to measure if and by how much it's balancing. Then it hit me, I have a couple of Cyclone first stages which use the replaceable orifice, why not make the soft seat to fit them? The basic design will be the same, just the diameter of the orifice itself is different. Installed in the cyclone I can monitor IP which will give me a good way to test for sealing and balance. I have made a few prototypes and am getting some interesting results. I have a NOS set of seats on the way so I can look at how the original ones were done. At least on the hard seat I have, I have found one possible problem with the sealing, The stem measures 0.118 in vs the 0.122 in on the stem of the "standard" USD soft seat. While 0.004 is not a lot, it is enough to possibly cause problems. I will be interested to see how the other one I have coming compares. I have had issues with the balance chamber leaking on my test prototypes so there may be something there. Changing the oring helped for now but I am still wondering about it.
More to come as I make and test prototypes......I will say now that I have NO intentions of making or selling them, I don't want to make or sell parts but I will be happy to give Bryan whatever I come up with if he chooses to explore it farther.
Herman

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Bryan
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Re: USD Royal Mistral (again)

Thu Jan 21, 2016 12:56 pm

Well said Ron, thank you. No one person built VDH...The community did :)

Herman, we should make those seats with all the profit we have made from the USD 2nd stage port plugs Image

Keep up the great posts and projects gang!

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Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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Ron
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Re: USD Royal Mistral (again)

Thu Jan 21, 2016 3:14 pm

Remember the single hose kits I made years ago? People loved them, but would complain about the cost. I made a dollar off of each one during a time period where I was in grad school and living off of like 12 grand a year.

It's pretty much always a labor of love right? It's like all that insane cash I made off of teaching the vintage diving course lol.


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Robohips77
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Re: USD Royal Mistral (again)

Fri Jan 22, 2016 5:51 pm

slonda828 wrote:Like so:

Image


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Well now I need to go back and review my Royal Mistral. I had problems putting it back together in this order. Is everyone sure that this the correct order of parts? Is there only an o ring in this crown block or does it have the Teflon split ring also? Thanks everyone. Ron this is an extremely good thread.
First dives? 1967 and I never lost the fever.

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Herman
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Re: USD Royal Mistral (again)

Fri Jan 22, 2016 8:30 pm

That is the order, you are missing an oring on the soft seat.
Herman

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Ron
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Re: USD Royal Mistral (again)

Fri Jan 22, 2016 9:18 pm

I took the oring off to clean the seat. It's a -12.


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Ron
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Re: USD Royal Mistral (again)

Sat Jan 23, 2016 10:32 pm

Here are more seat specs:

Image

Image

Image

Image


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Ron
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USD Royal Mistral (again)

Sat Jan 23, 2016 10:34 pm

So...my RM works. I'm not a fancy guy, so I just cleaned it up, used a polishing cloth on the poppet and seat, put some viton o-rings in it, and tested it.

Mine does not leak enough to produce a sound, or cause a bubble in a bowl of water when pressurized and submerged.

The balance chamber takes a -06 o-ring like a RAM, and the body takes a -06 o-ring like a DW mistral.

Image


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