|
Post by SeaRat on Oct 15, 2021 17:39:24 GMT -8
Here are a couple more photos of my Overpressure Breathing regulator: IMG_1254 by John Ratliff, on Flickr IMG_1235 by John Ratliff, on Flickr IMG_1181 by John Ratliff, on Flickr As you can see, mine now features a longer yoke, with a banjo fitting for a SPG. As you can see, with the longer hoses, the OB regulator is a very easy one to use. I replaced the non-return valve in the mouthpiece too, but innovating a bit. But it has only one, in the inhalation side, and no exhalation non-return valve. To get us back to the "Supercharge a Mistral" theme, here's a quote from Fred Roberts in Basic Scuba: Now, let's talk about the Mistral, and supercharging it. John
|
|
|
Post by antique diver on Oct 23, 2021 17:57:24 GMT -8
I made a dive with the Mistral this week, and found a mild but noticeable improvement in the venturi action. I will adjust it to be a little more aggressive before next trip, but I didn't try to re-adjust in the field since I had other regulators to dive and we got a late start in the day. I didn't get around to making a dive with the Spaco before the weather sent me home. While I am pleased with the venturi adjustment modification, I still find the initial cracking effort before the venturi becomes effective to be disappointing compared to the way I have set my RAM and Trieste. I have the latest silicone diaphragm, and the levers are set as high as I could without causing air leak at low tank pressure. I'm open to suggestions about getting below 1" on initial effort, as I find that objectionable when compared to the other above mentioned regs. Since there is no IP to adjust I can only think of trying a weaker spring, but suspect that I can't go far with that before the HP seat doesn't seat as well. Won't know until I try it. Maybe the original spring is off specification. Suggestions welcome!
|
|
|
Post by SeaRat on Oct 23, 2021 18:45:34 GMT -8
I made a dive with the Mistral this week, and found a mild but noticeable improvement in the venturi action. I will adjust it to be a little more aggressive before next trip, but I didn't try to re-adjust in the field since I had other regulators to dive and we got a late start in the day. I didn't get around to making a dive with the Spaco before the weather sent me home. While I am pleased with the venturi adjustment modification, I still find the initial cracking effort before the venturi becomes effective to be disappointing compared to the way I have set my RAM and Trieste. I have the latest silicone diaphragm, and the levers are set as high as I could without causing air leak at low tank pressure. I'm open to suggestions about getting below 1" on initial effort, as I find that objectionable when compared to the other above mentioned regs. Since there is no IP to adjust I can only think of trying a weaker spring, but suspect that I can't go far with that before the HP seat doesn't seat as well. Won't know until I try it. Maybe the original spring is off specification. Suggestions welcome! Antiquediver, I think you have a fundamental misunderstanding of the single stage regulator. Also, it appears that you did not use it for the full length of the tank, as you are talking about the cracking resistance as if it is steady throughout the dive—it is not. It gets better as the dive progresses and the cylinder pressure decreases. You will not get any difference in the cracking effort by changing out the spring, as that isn’t what is driving it. What is driving it is the 2250 psig in the tank itself. The levers are compound to overcome the full tank pressure. Now, take that regulator and put it an a 500 psig tank, and measure the cracking effort. It will be substantially reduced, to the point that it is better than your Trieste or Aquamaster. I always waited for the last part of the dive with my Mistral/Scuba/Scuba Delux/Scuba Gold Label, as that is where these regulators really shine. Now, you’ve probably heard of a few attempts at a “balanced” Mistral by folks here. If they succeed in making a composite regulator, using the balancing machanism of a USD Conshelf, fur instance, you will get a single stage regulator which has a cracking effort that is independent of the tank pressure. The original U.S. Divers Company Royal Mistral was such a regulator, but it had a very short life, and is one of the very highly desirable as a collectible. It is quite different from the La Spiro Royal Mistral, which is unbalanced and essentially a Mistral dressed up. John
|
|
|
Post by antique diver on Oct 23, 2021 19:35:31 GMT -8
Thanks John, Before the trip I ran tests on the bench where my supply pressure to the regulator is fully adjustable. I tested it at 2200, 1500, 1000 and 500 psi.... but I failed to make a written record of the change in associated "cracking efforts" at each, so I was unable to be more accurate in my statement due to me forgetting the figures. Basically, I was diving it at beginning pressure of 2300 down to 1000 psi at the end of dive. Of course there was some decreasing change in breathing effort, but not to the point that I was satisfied. I was in a slow easy dive mode which kept my air demands low, but when I tested with heavier breaths during the dive there was of course a noted improvement due to the venturi "kicking in". No doubt I am just spoiled by my balanced regulators. I appreciate your reminder that the Mistral is best used when starting with half a tank of air.
|
|
|
Post by SeaRat on Oct 24, 2021 14:15:31 GMT -8
I have used the Mistral for decades, and never once tried starting it off at half a tank. Rather, I would simply enjoy it when I got to that point.
I’m looking at your orifice, and have a question; is the orifice simply a straight tube of the same diameter throughout? If so, it doesn’t really mimic the Mistral orifice. As I recall, the Mistral orifice has a tube which, at its end, narrows to a smaller diameter. This in effect increases the velocity down the intake hose. It is illustrated in Basic Scuba, by Fred Roberts.
John
|
|
|
Post by vance on Oct 24, 2021 15:03:38 GMT -8
As I understand it so far, Bill's venturi is an OEM Mistral, modded to a hose barb.
|
|
|
Post by antique diver on Oct 24, 2021 18:06:26 GMT -8
I have used the Mistral for decades, and never once tried starting it off at half a tank. Rather, I would simply enjoy it when I got to that point. I’m looking at your orifice, and have a question; is the orifice simply a straight tube of the same diameter throughout? If so, it doesn’t really mimic the Mistral orifice. As I recall, the Mistral orifice has a tube which, at its end, narrows to a smaller diameter. This in effect increases the velocity down the intake hose. It is illustrated in Basic Scuba, by Fred Roberts. John It is one of several I got from VDH to experiment with some years back and modified while experimenting with it on the Over-Pressure reg. I can put the original and will give it a try, but the venturi isn't the issue. It's working great now, but now the cracking effort is my irritation, and not sure the original jet can make much or any difference there. But I will be trying that within a few days. My next step is to properly record all my breathing tests at various tank pressures, so I can keep better track of the results of any changes I make. I'll post any improvements that show up. Thanks for taking an interest, and I always like to hear suggestions.
|
|
|
Post by antique diver on Oct 24, 2021 18:32:40 GMT -8
Well, maybe part of the problem is that I have gotten spoiled to easier breathing regulators. Back in the late 50's and 60's I didn't really think much about "easy breathing", but was just thrilled to be able to breathe at all underwater. Haha...Cousteau once actually wrote something in an early instruction blurb something to the effect that you needed to practice to develop your "suction muscles" to become more comfortable breathing underwater. If I can just find little pamphlet (I know it's here somewhere) I'll post the actual quote. So maybe I'm just out of practice and my muscles have weakened with age and lack of use.
|
|
|
Post by SeaRat on Oct 26, 2021 9:37:39 GMT -8
I have been thinking about the high cracking resistance again, and I went out to the garage and put two regulators on full tanks to breathe off them. The regulators were my Overpressure Breathing regulator, and my Hybrid Gold Label regulator. And I did not recognize much of a cracking effort on these two regulators, even on a full tank. So what could cause a high cracking resistance? I've got some ideas.
--Lever height. I have my levers set to the highest level they can be without causing a flow when the case is closed. Typically this is about 1/4 inch above the level of the bottom box's seating area. If it is lower than that, the diaphragm has to travel some distance to engage the levers.
--A diaphragm which has a "set." If the diaphragm is old, and has taken a "set," then you need to overcome the "set" in the material to start the diaphragm's travel down. I've seen this with my original Trieste II diaphragm, which has a built-in "set." I had to make a new diaphragm myself to overcome that "set."
--In the mouthpiece we typically have mushroom non-return valves. If the intake mushroom "sticks," that must be overcome to start the breathing cycle. To check, take this mushroom valve out, and try it without the mushroom non-return in the mouthpiece. The intake non-return is not actually needed for diving, and only keeps water out of the intake hose if you allow water into the mouthpiece. So try it without this mushroom, and if that is the problem and you want a mushroom there, get a silicone one, and make sure that it is dry. Do not silicone it either, as the silicone can also cause it to "stick" to the wagonwheel.
Well, that's what I was thinking. Try looking at these three areas and then report back on the results.
John
|
|
|
Post by antique diver on Oct 26, 2021 14:56:24 GMT -8
I have been thinking about the high cracking resistance again, and I went out to the garage and put two regulators on full tanks to breathe off them. The regulators were my Overpressure Breathing regulator, and my Hybrid Gold Label regulator. And I did not recognize much of a cracking effort on these two regulators, even on a full tank. So what could cause a high cracking resistance? I've got some ideas. --Lever height. I have my levers set to the highest level they can be without causing a flow when the case is closed. Typically this is about 1/4 inch above the level of the bottom box's seating area. If it is lower than that, the diaphragm has to travel some distance to engage the levers. --A diaphragm which has a "set." If the diaphragm is old, and has taken a "set," then you need to overcome the "set" in the material to start the diaphragm's travel down. I've seen this with my original Trieste II diaphragm, which has a built-in "set." I had to make a new diaphragm myself to overcome that "set." --In the mouthpiece we typically have mushroom non-return valves. If the intake mushroom "sticks," that must be overcome to start the breathing cycle. To check, take this mushroom valve out, and try it without the mushroom non-return in the mouthpiece. The intake non-return is not actually needed for diving, and only keeps water out of the intake hose if you allow water into the mouthpiece. So try it without this mushroom, and if that is the problem and you want a mushroom there, get a silicone one, and make sure that it is dry. Do not silicone it either, as the silicone can also cause it to "stick" to the wagonwheel. Well, that's what I was thinking. Try looking at these three areas and then report back on the results. John All good suggestions, some of which I had already corrected on the bench before going diving, and also one that I need to check on: Lever height: it is set to absolute maximum without causing air seep/flow when the band clamp is tightened down. Diaphragm: It is silicone, and I believe it is the softest version from VDH. Strange things happen with diaphragms sometimes, and I will be trying an older but good condition rubber one for comparison. Mushroom valves: I haven't taken it out of this one yet to see results, but I have removed it from other regs in the past with good results. I substitute a bare plastic sleeve with no "spokes" (actually a wagonwheel with spokes all removed) just to get optimum performance. Probably would help this one as well, and I'll be trying that. I also will be trying the original venturi tube as well. I has a slightly smaller end orifice and slightly larger side openings, so I'm not too optimistic about this being a fix for cracking effort.... but I'll never know if I don't try. (Sometimes I learn that I'm not as smart as I would like to be ) Thanks, and I'll post results within a few days.
|
|
|
Post by antique diver on Nov 3, 2021 7:20:52 GMT -8
RATS... I just spent 30 minutes writing up dives and adjustments to the Mistral, and accidentally erased it. Not doing it again, so here's the quick but incomplete version. Took the "supercharged" Mistral diving and the increased venturi effect worked to my satisfaction. Smooth and easy. As expected, the initial inhalation effort with 2000 psi in tank was not improved because my normal breathing is slow and light - not enough to initiate the venturi. Would have been better if I was swimming harder and breathing enough volume to kick it in. Of course as the tank pressure dropped the reg performed better, and by the time I was down to 1000 it was much improved and comfortable to dive with. Back on the workbench I tried a variety of diaphragms with no great satisfaction. Then removed the original type encapsulated inlet filter, replacing it with a modern one only half as thick. This resulted in slightly dropping the spring tension, making reductions in inhalation of 0.2 to 0.4". Did not result in air seep at 500 psi, so I guess I'll call that an improvement. Restored to original jet to keep it stock, and Mistral is back in the display case looking pretty. I'm tired of tinkering with it.
|
|
|
Post by vance on Nov 4, 2021 15:00:02 GMT -8
I tried to thread the stainless steel tubing I used for my Healthways GL type valve cap so's I could do this kind of adjuster nut.
Fail! Stuff is hard as diamonds. I couldn't get the die started. I suppose annealing is the cure?
|
|
|
Post by vance on Nov 4, 2021 15:36:03 GMT -8
..... removed the original type encapsulated inlet filter, replacing it with a modern one only half as thick. This resulted in slightly dropping the spring tension, making reductions in inhalation of 0.2 to 0.4". Did not result in air seep at 500 psi, so I guess I'll call that an improvement. What was the starting point for the 02"-.04" reduction? I have mentioned my experiences with lowering spring pressure in single stage valves before, in one or more of the Misuba and Healthways threads. The upshot is that you can adjust cracking by subbing springs of various tensions, or by some other means, like using a thinner filter (fine screen + coarse) or removing material somewhere. In HW DH regs, if you don't want to mess with springs, you could leave out the reserve plate to gain a few thousandths of slack. Or, more slack can be gained by cutting (lowering) the soft seat's spring seat ledge in a lathe. You could do it with a drillpress or hand drill, but you'd better be careful! I haven't given much thought to the Mistral, since I thought it perfect as is. Huh. Maybe take out some brass from inside the soft seat bore under the spring? It's a long and arduous path.
|
|
|
Post by antique diver on Nov 4, 2021 20:49:30 GMT -8
I tried to thread the stainless steel tubing I used for my Healthways GL type valve cap so's I could do this kind of adjuster nut. Fail! Stuff is hard as diamonds. I couldn't get the die started. I suppose annealing is the cure? You might try that to soften it a bit, which won't affect the end product. I began with a 3 or 4" piece of tubing so I could clamp 1" of an end firmly in my vise to the point of flattening that part out quite a bit so it wouldn't turn as I ran the tap in the open end. Then cut the threaded end of tube off to desired length.
|
|
|
Post by antique diver on Nov 4, 2021 21:04:39 GMT -8
..... removed the original type encapsulated inlet filter, replacing it with a modern one only half as thick. This resulted in slightly dropping the spring tension, making reductions in inhalation of 0.2 to 0.4". Did not result in air seep at 500 psi, so I guess I'll call that an improvement. What was the starting point for the 02"-.04" reduction? I have mentioned my experiences with lowering spring pressure in single stage valves before, in one or more of the Misuba and Healthways threads. The upshot is that you can adjust cracking by subbing springs of various tensions, or by some other means, like using a thinner filter (fine screen + coarse) or removing material somewhere. In HW DH regs, if you don't want to mess with springs, you could leave out the reserve plate to gain a few thousandths of slack. Or, more slack can be gained by cutting (lowering) the soft seat's spring seat ledge in a lathe. You could do it with a drillpress or hand drill, but you'd better be careful! I haven't given much thought to the Mistral, since I thought it perfect as is. Huh. Maybe take out some brass from inside the soft seat bore under the spring? It's a long and arduous path. The supply pressure was at about 2200 psi, and cracking point was at 1.6" before changing to the thinner filter. Next time I tinker with the Mistral I will try cutting the bore depth a bit deeper on the Unimat Lathe. That's assuming there is enough metal there to safely remove without compromising the soft seating material. I have a bunch of those so it won't be a disaster if I wreck one.
|
|