|
Post by vance on Jun 5, 2024 16:20:20 GMT -8
|
|
|
Post by jeffinmichigan on Jun 5, 2024 17:42:22 GMT -8
Hello all I was told that I should post a build review of the Overpressure I have been diving this year.
Last year I was gifted a tank, regulator and harness setup. It was found clearing an uncle's estate by someone who knew of my interest in double hose diving.
The regulator was in good shape. Internals were iffy. The bite mouthpiece was degraded to a sticky mess and was instantly thrown out.(not original to the regulator) The one way flap valve was stiff, and got the silicone grease treatment. The original duckbill was in good working order. The inner hose was a goner, dry cracked and flaking to the reinforcement fiber layer. The diaphragm was also toast, stiff cracked grey rubber with a brass plate riveted to it. Hoses were in decent condition, they were removed and stored away.
The basic design is essentially a Mistral with an extra pilot port in the mechanism and a hose replaces the Venturi nozzle. The fitting on the end of the hose was the priority for getting this working. To get it I cut the compression collar holding the hose on. Underneath was an approximately 1/8" hose barb.(1/4"ID hose) The replacement hose was sourced from the local pneumatic/hydraulic supply store. They recommend two ear pinch clips for mounting the hose. I picked up a 1/4" hose barb fitting while I was there. This had the barb cut off and silver soldered over 1/8" barb, and trimmed to just longer than the smaller inner fitting. This did not modify the airway.!. (in hindsight a Mistral nozzle with the hose band clamped over the ports would work, if the orifice matched)
The fitting was threaded in and it's orientation marked and noted. The fitting removed, is now fit with the ears of the pinch clips parallel to the can. I fed the hose through the exhaust horn before inserting the mechanism into the can. Be aware that this method increased the diameter of the hose over the original compression fitting. I accommodated for this with a thicker gasket between the can and the mechanism. My choice was cork (cut your own) gasket sheet, the original gasket was my template. This does take up some room on the body/mechanism indexing dowel. I cut the hose to match the 1" hose loops positioning of the mouthpiece.
The one way valve was dove a few times and then retired. I was able to remove it in one piece although the retainer tabs look a little bit chewed up. In order to make a new flap I used the original as the template and then put holes where the retainer tabs had been. Long story short I "riveted" the silicone sheet replacement flap to the one way valve body. This mouthpiece only has a one-way valve in the inhalation hose.
That pretty well covers it let me know if you have any questions. I'll keep an eye on this for a few days and then from time to time. Jeff
|
|
|
Post by vance on Jun 6, 2024 7:22:29 GMT -8
|
|
|
Post by vance on Jun 6, 2024 7:25:44 GMT -8
|
|
|
Post by vance on Jun 6, 2024 7:27:42 GMT -8
Here's the duckbill attached to the removeable horn: IMG_3082 by Vancetp, on Flickr
|
|
|
Post by artc on Jun 6, 2024 16:21:59 GMT -8
Hi Jeff, two questions. When you silver soldered the Barb, did you use a MAPP torch or oxygen acetylcholine? Also, could you expand your thoughts on how a Mistral nozzle with a hose band clamping the ports shut could be fabricated to work on a DX Overpressure? I think it could be a viable alternative solution. Thanks.
|
|
|
Post by vance on Jun 6, 2024 16:32:50 GMT -8
The barb on an O-P screws into the valve body, just like a Mistral venturi tube. However, it doesn't need the side drillings. If you could slip a hose over a Mistral tube, it would close them. The only thing you'd need to know is what is the jet drilling on an O-P barb.
|
|
|
Post by SeaRat on Jun 6, 2024 18:54:25 GMT -8
The barb on an O-P screws into the valve body, just like a Mistral venturi tube. However, it doesn't need the side drillings. If you could slip a hose over a Mistral tube, it would close them. The only thing you'd need to know is what is the jet drilling on an O-P barb. The only note of caution is that the Mistral orifice was precisely designed to shoot air down the intake horn and through the one-inch open corrugated hose to the large mouthpiece. Check the opening against the opening of the DX, which may have been slightly larger. The Mistral orifice may give a bit more push to air than the original DX orifice to the inner hose. One other thing; the mouthpiece opening consists of three drilled holes pointed down the mouthpiece. I’ve always thought that a better solution would be a slot, much like the Scubapro 109’s, instead of those three holes. The three holes, if there is water inside, shoot a spray into the mouth, whereas a slot might be a bit better and not aerosolize the water. Also, for ice diving, the three holes shot tiny ice particles into the mouth, and that apparently hurt in the back of the that, according to Fred Roberts in Basic Scuba. Johtn
|
|
|
Post by artc on Jun 6, 2024 18:59:50 GMT -8
Thanks Phil, I’d like to try the hose over the Mistral nozzle idea. To make it work, the nozzle would need to be screwed into the body first and then the hose pushed over the hex and port holes. After that is done, what would be the best way o clamp the hose down on the nozzle? John (Sea Rat), how did you secure the hose to body?
|
|
|
Post by SeaRat on Jun 6, 2024 21:33:53 GMT -8
Thanks Phil, I’d like to try the hose over the Mistral nozzle idea. To make it work, the nozzle would need to be screwed into the body first and then the hose pushed over the hex and port holes. After that is done, what would be the best way o clamp the hose down on the nozzle? John (Sea Rat), how did you secure the hose to body? I use zip ties. Nothing fancy. The inner hose does not require a pressure fittings, as it is an open system. There might be a slight increase in pressure in the hose upon inhalaation, but it is very small. John
|
|
|
Post by artc on Jun 7, 2024 7:44:39 GMT -8
Sorry for beating a dead horse, but I keep thinking about how to best recreate a new safe hose connection for the DX. How about purchasing new green oxygen 1/4 inch ID hose with an appropriate size ferrule and crimp it to the original fitting to the body mechanism? Obviously, the fitting would have to be prepared by removing the old ferrule and hose around the barb first. A Dremel tool could easily perform this task. It would essentially be recreating the hose to original specs using both new and old parts.
|
|
|
Post by jeffinmichigan on Jun 7, 2024 8:27:44 GMT -8
Artc I used Mapp gas, though it was on the cusp of melting the 1/4" brass fitting when the solder flowed nicely. For the using a Mistral nozzle comment, the mechanism has a second hole prior to the hose on a DX. This will somehow effect the pressure feeding into the nozzle I am unfamiliar with the Mistral yet and do not know if it's orifice is the same size as the DX hose orifice.(small diameter for the DX) as pointed out by Vance the hose would then be clamped over the ports on the side of the Mistral nozzle.
If you have access to a replacement farrow and ability to swaged it or have it swaged I would recommend it beyond my method or my thoughts wondering to Mistral nozzles.
SeaRat, I was uncertain of pressure levels within the mechanism. I had presumed that it could be high being a single stage. Also the center hole in the mouth piece is fully drilled through the pipette. Haven't seen this mentioned before. Jeff
|
|
|
Post by vance on Jun 7, 2024 8:29:40 GMT -8
Sure, that would also be true to OEM.
I have an original barb fitting with the ferrule still on it, if anyone's interested. I also have a couple of repro Mistral fittings that could be modified into a barb. The side holes are a problem, but could be filled with JBWeld.
|
|
|
Post by vance on Jun 7, 2024 8:45:29 GMT -8
I had forgotten that the center hole in the mouthpiece tube goes through. This would indicate to me that the holes are calibrated as well, and cutting a slot would not work.
|
|
|
Post by vance on Jun 7, 2024 8:49:29 GMT -8
Thanks Phil, I’d like to try the hose over the Mistral nozzle idea. To make it work, the nozzle would need to be screwed into the body first and then the hose pushed over the hex and port holes. After that is done, what would be the best way o clamp the hose down on the nozzle? John (Sea Rat), how did you secure the hose to body? Our resident genius Bill T made a small threaded sleeve that fit over the holes in the Mistral venturi, which made it adjustable. The holes can be partially to fully blocked to decrease/increase the venturi. He mentioned that plastic or rubber tubing isn't strong enough to keep screeching blowby from happening. Here's the link to his thread. vintagescuba.proboards.com/thread/5650/supercharge-mistralIt appears that our other resident genius Luis had done something like this also.
|
|