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Post by antique diver on Oct 14, 2021 11:24:15 GMT -8
I have heard from others how well their Mistrals performed, but have never been able to coax mine into meeting my expectations in spite of the silicone diaphragm and many tuning attempts. A new try at it on the bench this week, and still not satisfied with the air flow, so I decided to attempt a boost to the venturi configuration. I knew from other regulator hot-rod projects that very slight changes in orifice sizes could make a considerable difference in breathing performance. I didn't want to be permanently changing critical orifice sizes on the limited number of jets that I had, so wanted to come up with something adjustable. First steps included extending the threads on the jet all the way past the side bypass holes, using a 5/16"x24 die. Then taking a straight piece of 3/8" SS tubing (with 0.049" wall thickness) I cut matching female threads about 3/8" into tube end. Used a Dremel cutting wheel to slice off a thin bit of the tube (about 5/32"). Here's the results...  (Ignore the barbed end of the jet which was for a whole different project) This makes it easy to begin fine tuning the orifice that controls volume of air going into the cans, which affects the velocity and volume of air going directly into hose.  After fine tuning to desired performance (with no bypass flow out the exhaust) a small drop of removable Loctite keeps the adjustment "nut" in place. That's important since slight changes in positioning could make performance go either way, potentially creating an uncontrollable free flow if the orifices were reduced in size during use.  Another reg to test in the water asap. |
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Post by vance on Oct 14, 2021 11:56:32 GMT -8
Very clever. I will definitely go to school on you for this mod. I won't use it on Mistrals, though. Funny that yours doesn't perform well. All my Mistrals have been great breathers!
Since you're using an O-P barb there, I'm wondering if your valve is an O-P as well? They have 2 small holes in the top of the valve, where the Mistrals have only one. That could account for less performance.
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Post by surflung on Oct 14, 2021 13:07:40 GMT -8
I've been looking at these pictures and trying to remember what my original Mistral nozzle looks like. It has a couple of secondary ports to reduce the power of the venturi when inhaling and stop the Venturi when exhaling. So you are basically fine-tuning the secondary ports to increase the strength of the Venturi?
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Post by antique diver on Oct 14, 2021 14:05:23 GMT -8
Very clever. I will definitely go to school on you for this mod. I won't use it on Mistrals, though. Funny that yours doesn't perform well. All my Mistrals have been great breathers! Since you're using an O-P barb there, I'm wondering if your valve is an O-P as well? They have 2 small holes in the top of the valve, where the Mistrals have only one. That could account for less performance. I keep hearing that they are great breathers. This one seems that way now on the test stand, and I'm optimistic. The barbed jet you see was actually born as a Mistral jet that I modified for use in an experimental Over-Pressure project. I didn't want to modify the original one from this reg, so substituted this. The barbs are serving no function here, and I would have cut them down to smooth tube except I was waiting to see what you had to say!  That's a good point you made about the valve, but certain is original to this really nice Mistral. I have had it for 15+ years, but I just never enjoyed using it before. I hope this trick works out well during actual diving. Hoping for next week to get this wet and also finally the Spaco. |
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Post by antique diver on Oct 14, 2021 14:10:52 GMT -8
... So you are basically fine-tuning the secondary ports to increase the strength of the Venturi? |
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Post by vance on Oct 14, 2021 14:19:34 GMT -8
Bryan has repro Mistral venturi nozzles on his site for a great price ($10?). I have a couple that I bought to replace JetAir nozzles. I just bought another one! vintagedoublehose.com/store/#!/Venturi-Nozzle-single-stage/p/8417349/category=1964151 |
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Post by luis on Oct 14, 2021 17:20:46 GMT -8
Very nice work Bill. If you use a Nyloc nut, you will not lose the adjustment, but you can change it a will. I used reproduction Mistral nozzle bodies and had them modified. Notice that I blocked the original bleed ports with the clear tubing. No “functional” vintage parts were sacrificed on these projects. The pictures below are from two different "balanced demand valve" single stage regulators. It was what I called the Unicorn project. Note on name selection: Unicorn for single stage versus the Pegasus project for my old two stage Voit Titan conversions. Unicorns are cool, but winged horses are even more cool.  The first image is from the Unicorn II (2nd generation). It has HP ports, etc.
Theses are from the Unicorn I
Someday I should get back to this project. I have new lever design and an adjustable cracking effort design that I would like to incorporate...
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Post by luis on Oct 14, 2021 17:34:00 GMT -8
Here are a couple of pictures of the venturi nozzle without the Nyloc nut.
  And here are two different Unicorn II that I dove for a while.   This was a fun project... I should get back into it... I just need to retire from my full time job. |
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Post by antique diver on Oct 14, 2021 17:34:48 GMT -8
Luis, I see what you did... nice job. I previously tried plastic tubing over the original side vents, but the air just blew past it with a wild screeching sound. I see your new placement of the vents, and I didn't think of that. I had also tried soldering the original holes shut and drilling smaller holes into the solder, but it was tedious and time consuming finding just the right size hole, as you must already know. I would have used a Nylock nut but there was only room for the SS tubing where the original vents are. No extra room like the housing you have. I thought about turning one down but then I would have been faced with a difficult item to turn and adjust so I went the easy route with the tubing. Just lucky that the dimensions worked out for threading the inside of it. I like your idea, and I may still try a Nylock machined down to a suitable round item to fit in the small space available. Thanks for the input... always good to hear from you! |
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Post by vance on Oct 14, 2021 17:35:03 GMT -8
The nylock nut is a good idea! They do get loose after some turning in and out.
I've made a single stage balanced valve using Healthways valve bodies and levers. The HW levers are easier to adjust than the USD version. I have not done a mod for the venturi adjustment yet, but it's coming!
Eventually, a set of ports would be the way to go!
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Post by luis on Oct 14, 2021 18:11:40 GMT -8
Hi Bill, Yes, whenever possible I like to add the ability to make some features adjustable. It allows to compensate for tolerances. Like you discovered, the venturi flow can be be affected by very small variations... and it will also be affected by the change in air density with change in depth. So you may have to adjust some more. I didn't have my DSV with the flow diverter back when I did this project... I actually have an even newer flow diverter that I have been working on. I can really play with some very aggressive venturi flow with my latest mouthpiece. Yes, my personal Argonauts are taking full advantage of some serious venturi flow. The other part of the projects is the adjustable cracking effort. Here are some pictures of some of the load testing I did on the pressurized valves.
I took data on both non-balanced and balanced demand valves. The load data I took was directly on the valve and on the components of the compound levers. And I took the data as a function of tank pressure, from 3000 psi down to 100 psi in increments of 100 psi. I have all the data on Excel spread sheets with very nice plotted graphs showing a very nice pattern. That is the information I used for analysis and calculations... That is what engineers do for fun... Note: the LP block that you see on the pictures was just their as a consistent hard surface to push against. The weight on the scale is accounted for.    |
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Post by nikeajax on Oct 15, 2021 8:40:35 GMT -8
Nice robots Luis  JB |
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Post by SeaRat on Oct 15, 2021 11:41:49 GMT -8
Very clever. I will definitely go to school on you for this mod. I won't use it on Mistrals, though. Funny that yours doesn't perform well. All my Mistrals have been great breathers! Since you're using an O-P barb there, I'm wondering if your valve is an O-P as well? They have 2 small holes in the top of the valve, where the Mistrals have only one. That could account for less performance. I keep hearing that they are great breathers. This one seems that way now on the test stand, and I'm optimistic. The barbed jet you see was actually born as a Mistral jet that I modified for use in an experimental Over-Pressure project. I didn't want to modify the original one from this reg, so substituted this. The barbs are serving no function here, and I would have cut them down to smooth tube except I was waiting to see what you had to say! That's a good point you made about the valve, but certain is original to this really nice Mistral. I have had it for 15+ years, but I just never enjoyed using it before. I hope this trick works out well during actual diving. Hoping for next week to get this wet and also finally the Spaco. Okay, I've got to hear more about this experimental Over-Pressure project. Did you actually build an Overpressure Breathing regulator with the hose-within-a-hose concept? I'm curious, as I have an Overpressure Breathing regulator, which is one I've been using for decades now, and it'll beat any Mistral or Gold Label Scuba regulator out there. I put longer hoses on it, but kept the metal mouthpiece and hose-within-a-hose Venturi concept.  IMG_1256 by John Ratliff, on Flickr Here is my Overpressure Breathing regulator, set up on twin 52s. Note the longer hoses, which can be used without compromise as the Venturi from the hose-within-a-hose concept doesn't really care how long the inner hose is. John |
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Post by antique diver on Oct 15, 2021 16:31:32 GMT -8
I keep hearing that they are great breathers. This one seems that way now on the test stand, and I'm optimistic. The barbed jet you see was actually born as a Mistral jet that I modified for use in an experimental Over-Pressure project. I didn't want to modify the original one from this reg, so substituted this. The barbs are serving no function here, and I would have cut them down to smooth tube except I was waiting to see what you had to say! That's a good point you made about the valve, but certain is original to this really nice Mistral. I have had it for 15+ years, but I just never enjoyed using it before. I hope this trick works out well during actual diving. Hoping for next week to get this wet and also finally the Spaco. Okay, I've got to hear more about this experimental Over-Pressure project. Did you actually build an Overpressure Breathing regulator with the hose-within-a-hose concept? I'm curious, as I have an Overpressure Breathing regulator, which is one I've been using for decades now, and it'll beat any Mistral or Gold Label Scuba regulator out there. I put longer hoses on it, but kept the metal mouthpiece and hose-within-a-hose Venturi concept. IMG_1256 by John Ratliff, on Flickr Here is my Overpressure Breathing regulator, set up on twin 52s. Note the longer hoses, which can be used without compromise as the Venturi from the hose-within-a-hose concept doesn't really care how long the inner hose is. John My Overpressure was acquired years ago in pieces in a big box-o-junk of other stuff in same disarray. There were no regular hoses, and the inner hose was missing, but the working parts and original mouthpiece (less the valves)were there. I tried to recreate it, and experimented with different jets but it never breathed right, and I lost interest after a while. It is a nice looking specimen and I will probably just convert it to Mistral status. The box eventually yielded other regulators as well, but were in parts scattered and scrambled throughout the container in no order whatsoever. Ended up having all the original parts for a beautiful un-dented non-mag once I had it powder coated, an Aquamaster of good condition and plenty of good to have parts. |
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Post by vance on Oct 15, 2021 16:53:04 GMT -8
I love it when a box o' junk yields cool stuff. It's rare.
I never liked the O-P rush of air. It is like the MR-12. Too forward. Gack!
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