YankDownUnder
Pro Diver
Broxton 'green label' Aqua Lung and 1954 USD Rene triple 44s.
Posts: 162
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Post by YankDownUnder on Apr 19, 2005 15:57:58 GMT -8
There are two very interesting vintage rebreathers on Ebay at the moment and two similar ones went off without a single bid. The minimum prices make them a steal. I had to pay twice as much for mine. The Cressi-Sub ARO-57B sport rebreather became popular in Europe in the late 50s. It is a manually operated, closed circuit, oxygen pendulum rebreather. The other is a very rare Super ARO used by the Italian Navy. Both cost less than a good BCD or modern regulator. There is a tear down of the ARO-57B on www.nobubblediving.com. The one pictured is the one I bought. It works great. It replaced the one I foolishly sold, when I was 21, and spent 35 years trying to replace. www.therebreathersite.nl is the most exstensive site you will find on rebreathers of all types. Most of it is in English, but some is in Dutch. O2 rebreathers do not require PPO2 gauges. Just don't exceed 30 feet of sea water and do not overbreathe the scubberby excessive work. Otherwise you go into convulsions and drown. The US Navy Diving Manual Ch 4. should be closely studied if this kind of vintage diving interests you. Make sure that you flush the system at least three times before decending and once underwater after 15 minutes. If you do not, you will end up with pure nitrogen in the counterlung, as your body metabolizes the oxyen in the air and the CO2 is scrubbed out. The first symptom of this is death. The best way to test one of these rigs is to sit on the couch and breathe from it, while watching "Silent Enemy" with Laurence Harvey fighting Italian frogmen. He is using a Davis Submarine Escape Apparatus and the "Italians" have Avon UBAs. If you pass out there, you know you have a problem and drowning is a bad way to find that out. Change your Sofnolime or DragerSorb before every dive and make sure you do your loop tests too. If you are not prepared to learn about O2 rebreathers before diving one, have your widow contact me and I'll bid on your vintage gear.
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Post by John C Ratliff on Apr 19, 2005 16:02:10 GMT -8
If you guys look at the photos, you will see that he clamped the top of the tube with what looks like a SS flat bar with rounded ends. Serving a duel roll of giving him a place to attach webbing and serve to isolate the inhale side from the exhale side. So the only way to be able to inhale the gas from the exhale side is after it pases through the scrubber. Bill Thanks Bill, Just looking at it, I could not be sure that the two sides were separated. John
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Post by cstmwrks on Apr 19, 2005 18:16:14 GMT -8
Not that I'm out to be mean or anything, but this post is just to shoot some bullet holes in the comments left by YankDownUnder. 1# on the "do not exceed depth", I do not have my table data in front of me, but depth limits are very general. Based on Navy data collected from many lost lives, at 20 feet one "may" be good for 45 minutes. At 30 feet I recall the time drops to about 10. Hi work loads and stress ( combat ) reduce time even more. Slow gentle fish watching can increase the tolerance. So the 30' limit is kinda meaningless. What you can do for 30 minutes at 10 feet may kill you in five minutes at 30'. 2# even after three well done purges, your still not breathing pure 02... not even in your dreams. As for the 15 minute flush at depth, well its not a bad idea by any means. One does off gas nitrogen back into the loop, but this may amount to all of a liter of N and it takes more than 15 minutes to work out of the divers blood stream.
TEST QUESTION: how do you "run" you 02 rebreather so at least every two minutes you get feedback from your rig that lets you know all is working as it should be? There is one correct answer that covers all the bases.
Bill
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Post by John C Ratliff on Apr 19, 2005 20:33:20 GMT -8
I see the above post is talking about limits on O2 breathing. It is interesting to me that there are a lot of different opinions on this, and perhaps one does have to look at the table data. But I just wrote a book review about the book by Dr. Hans Hass, We Came From the Sea. I suggest you go and look at what he wrote about using oxygen rebreathers toward the end of my review in the following post: vintagescuba.proboards2.com/index.cgi?board=general&action=display&n=1&thread=1111975890Dr. Hass has probably more experience using oxygen rebreathers than anyone alive. They had one fatality, and one other near miss. The fatality involved apparently having nitrogen in the breathing bag, and the near miss was when a soda-lime canister got contaminated with sea water while they were observing sharks. I do know that when I went through the U.S. Navy School for Underwater Swimmers in Key West, Florida in 1967 that we were all tested for oxygen tolerance. We were placed in a chamber, and breathed pure oxygen for I believe 30 minutes (it's been a long time ago) at about 60 feet (three atmospheres absolute, I believe). This and the experiences of both Cousteau (who nearly died twice with oxygen poisoning trying us develop an oxygen rebreather at about 40 feet depth) and Hans Hass show that there are differences in individual tolerances to oxygen under pressure. Probably the best way is to get into a chamber and undergo an oxygen tolerance test. SeaRat
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Post by SeaRat on Apr 19, 2005 21:36:07 GMT -8
After thinking about this just a bit longer, I would go with cstmwks remarks, and get instruction based upon the newest tables, and the most recent research. I am no expert in rebreathers, and don't think I will ever begin either. I liked the last words of Hans Hass I put in the book review above when he recommended that divers stick with compressed air. Rebreathers have killed a lot of people, and almost killed Jacques Yves Cousteau; in fact, if it were not for this experience, he never would have co-invented the compressed air scuba, the Aqualung.
John
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YankDownUnder
Pro Diver
Broxton 'green label' Aqua Lung and 1954 USD Rene triple 44s.
Posts: 162
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Post by YankDownUnder on Apr 20, 2005 1:17:05 GMT -8
US Navy Diving Manual Volume 4, Tables show:
O2 Exposure Limits for Continuous Dives;
25 fsw=240 min 30 fsw=80 min 35 fsw=25 min 40 fsw=15 min 50 fsw=10min
Single Depth Oxygen Excursion Limits
21-40 fsw =15 min 41-50 fsw =5 min
(Don't trust my figures, use the Manual. It changes! Even the NOAA manual recommends you follow Navy tables. Navy divers are tested for individual tolerances.)
Looking at those numbers shows that time drops off rapidly with minor changes in depth that most of us could not maintain. I know I can't. Only a 5 foot difference (30 to 35, reduces exposure time from 80 to 24 minutes.)
I own 6 rebreathers and began diving with oxygen in 1961. Looking back on my early experiances, I should be dead. (Some people think I am.) I understand why I survived. One stupid thing offset another, I was lucky. I dive a Drager LAR, a Cressi ARO-57, a C-96, a CDBA and the others are mixed gas, but O2 capable. One of my best rebreathers was the Russian IDA-64, but I sold that while cutting shipping weight to move to Australia last November...... I am not an expert, by any stretch of the imagination.
Hans Hass was an expert and would leave some air in his Drager and to get greater depth. It can work, but may not. The technique is shaky at best. The diver allows his bouyancy to cue him as to when to add oxygen. When you start to sink, you have used up O2 and need to add. You trim yourself with O2 like a sport diver does with a BCD. He was diving without a suit. Suits compress and introduce another factor. It still was very dangerous and he was very experianced.
My PPO2 gauge never shows 100% (1.00 at surface) as there is always some nitrogen in the scrubber and counterlung that is not flushed. That is a good thing.
Most of my O2 diving is under piers and in shallow water, with flat bottoms, at about 8 meters (24 fsw). That's what most of the diving is like near my home. If you want to dive O2, dive with an air bailout and some one who doesn't want to bid on your estate. At a minimum, take a Nitrox course and a Drager Dolphin course, so you know what is in a rebreather or should be there, and go from there.
I only point these things out because I would hate to see anyone hurt and it can happen. After all, this is supposed to fun.
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Post by seakrakken on Apr 20, 2005 2:05:17 GMT -8
Sorry for not replying to all the great questions and comments by everyone sooner. I was away for a couple of days. Bill is right. The inner tube is divided into two by a clamp which also acts as an attachment point for the strap. I am aware of the inherent risks involved with rebreathers. My self imposed Max Depth will be 20'. Which is considered a safe depth for O2. I will have regular scuba gear on as well, when I do sea trials. The comment about residual N2 in the loop is a valid concern. It has been demonstrated that even after purging the circuit 3 times it is possible to still have as much as 50% N2 present. Some of the materials on the subject I've read indicate a need to purge 5 times. I have had a lot of satisfaction building a rebreather but, that does not mean I'm an expert in the subject matter. To that end seeking training is a very good idea. I don't want to win any Darwin Awards
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Post by cstmwrks on Apr 20, 2005 5:50:07 GMT -8
Like it or not, diving a rebreather is taking on a new level of risk management. No way around it. Like it or not, taking a famed chamber test for 02 tolerance sounds good ... but all it means is you tolerated that test under what ever physical condition you were in at that time. It does NOT MEAN BUTT SQUAT about what you may be able to do the next day or a week later. Take our very, ahh shall we say 'safe' bubble blowing on air. We got countless more hours of dive data, computers strapped to your bunns and guess what? we still have wennie divers doing wennie "safe" dive profiles getting bent. There is more at play in diving physiology than any of us understand. 02 tolerance may be less understood than deco issues. Most of what is going on is in the brain, and I think we know how messed up that area is in most of us!
Have fun, dive safe, and all that good rot!
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Post by cstmwrks on Apr 22, 2005 10:08:46 GMT -8
Kind of on the same line of thinking, I notice a few posts about how an early rebreather almost killed cousteau on both attempts at his using it. Cousteau has super hero status in the diving world and I notice that folks take the adatude that something SOOO dangerous as to have nearly killed our hero twice is much to evil for us common people. Cruel fact of the matter was Cousteaus ignorance that almost killed him. Almost any rube can survive a dive on OC and live to tell the tail. A rebreather is just unforgiving of ignorance. One stupid slip up and you die. Knowledge is what keeps rebreather divers alive, not the rebreather per say. Bill
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Post by seakrakken on Apr 22, 2005 11:59:53 GMT -8
I agree Bill. I believe Cousteau also mentions he went to 80' that time. Later on the Calypso Divers used rebreathers on an occassional basis when the need existed. An example of this was when they were trying to get closer to the Manitees in Florida.
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Post by cstmwrks on Apr 23, 2005 3:10:03 GMT -8
Wonder how things may have gone had Cousteau hooked up with Haas? Haas had a much better understanding of physioligy of diving than Cousteau did. I have no idea when the first polarographic 02 sensor was developed but had those two got togeather with the working knowledge of those sensors it could have but rebreathers a half century ahead in development.
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Post by SeaRat on Apr 23, 2005 8:40:43 GMT -8
This is where I got the information on Cousteau and oxygen rebreathers. I see from ads that Jean-Michael Cousteau is using a rebreather now, and that Aqualung is selling them too. It would have been very interesting if Cousteau and Hans Hass could have gotten together, but during the war, a lot of things were not possible. Seakrakken, does the motercycle inner tube mentioned above sound familiar?
John
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Post by cstmwrks on Apr 24, 2005 11:02:19 GMT -8
Any chance that early BC'c might have been made with motorcycle tubes? Or did the May West pretty well rule from the start?
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Post by WIlliam Bonney on Apr 24, 2005 11:35:55 GMT -8
cstmwks
Around 1974 I was taking an divermasters class and met the "Great" Tommy Thompson from USD. I approached him about a inflatable unit that attached to the harness straps and was inflated off the tank. My prototype was made of inner tubes from an on 26 inch bycycle innertube. It ran from just below the armpit on the shoulder harness and followed the harnes across the back, attached to the tank backpac the over and down the other harness shoulder strap. It was attached with straps made from peices of rubber innertube similar to how a dive knife scabbard was attached to ones leg. It didn't have a overpressure valve like they do today.
He (Thompson) didn't show a bit of interest. Guess he figured I was too young, inexperienced (only been diving about 7 years then and I suppose Marine dive training didn't count sence he was Navy) to know what I was talking about.
Anyway, took the "idea" to a INVENTION COMPANY..dirty word to me now........only to have it stymied. Never did get my drawings back. About three years later USD came out with their first jacket type BC and then Scuba Pro with their's. Neither were based on expanding innertube technology but used two peices of fabric sewed and sealed together like the Maywest was built, however, the basic idea was very close to mine. ScubaPro even had a chart that showed the ring of air around the armpit/shoulder area One of them, don't remember which, said the idea was carried around by a commerical airline pilot for about two years before they got ahold of it.
Who's to say other wise?
But to answer your question, yeah, there once was one innertube BC in existence. Mine.............don't know of any others................
Billy
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Post by cstmwrks on Apr 25, 2005 5:48:07 GMT -8
For what its worth, my Aunt is in publishing on a joint venture with Harper Collins. Childrens learing books. They do not like to hear or receive ideas from the public either. With good reason, they spend lots of time and money in research and development. Lots of folks are full of good ideas like yours. But it may well be so close to a product that they themselves are truely developing on there own that they will not want to know any details to avoid patent issues, intellectual property issues and so on.
Bill
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