Why no poor man's rebreather?

[Sbiriguda]

I will bump this thread...
The rebreather technology is quite old, I would say it dates back to early 1930 and for sure they were commonly used in the WW2
So what does make them this expensive?
Presumably the electronics involved in safety checks (hoxygen levels, O2 levels, etc.), that didn't exist in the old rebreathers from the past
Now a naive question...the problem in a rebreather is not the gear but the diver...
Wouldn't it be easier and cheaper to put some sensors on the diver's body instead? Human body has reactions that should be a clear sign that something will go wrong (uncontrolled movements, body temperature, heart beat rate and so on). Combining several measures it should be easier to predict possible risks for the diver

 

[Sbiriguda]

I will also share this link
Another design of DIY rebreather
This is an "ARO - Autorespiratore ad ossigeno" type
Autorespiratore a ossigeno - Wikipedia

 

[AJ]

Now a naive question...the problem in a rebreather is not the gear but the diver...
Wouldn't it be easier and cheaper to put some sensors on the diver's body instead? Human body has reactions that should be a clear sign that something will go wrong (uncontrolled movements, body temperature, heart beat rate and so on). Combining several measures it should be easier to predict possible risks for the diver

Why search for a solution in technology when the problem is the diver himself? As far as i'am concerned too many divers rely on equipment instead of building skills already. Let's not make things worse. Rebreather diving means complex diving and requires a lot of awareness. If you can't or don't want to develop this awareness, don't dive breathers. I know it may sound harsh, but a breather is nog for every diver.

 

[Bob DBF]

The rebreather technology is quite old, I would say it dates back to early 1930 and for sure they were commonly used in the WW2

A quick look on Wikipedia:
The first basic rebreather based on carbon dioxide absorption was patented in France in 1808 by Sieur[7] Pierre-Marie Touboulic [fr] from Brest, a mechanic in Napoleon's Imperial Navy. This early rebreather design worked with an oxygen reservoir, the oxygen being delivered progressively by the diver and circulating in a closed circuit through a sponge soaked in limewater.[8] Touboulic called his invention Ichtioandre (Greek for 'fish-man').[9][citation needed] There is no evidence of a prototype having been manufactured.

A prototype rebreather was built in 1849 by Pierre Aimable De Saint Simon Sicard,[10] and in 1853 by Professor T. Schwann in Belgium.[11] It had a large back mounted oxygen tank with working pressure of about 13.3 bar, and two scrubbers containing sponges soaked in a caustic soda solution.

Modern rebreathersEdit

Henry Fleuss, inventor of the rebreather.
The first commercially practical closed-circuit scuba was designed and built by the diving engineer Henry Fleuss in 1878, while working for Siebe Gorman in London.[12][13] His self-contained breathing apparatus consisted of a rubber mask connected to a breathing bag, with (estimated) 50–60% O2 supplied from a copper tank and CO2 scrubbed by rope yarn soaked in a solution of caustic potash; the system giving a duration of about three hours.[13][14] Fleuss tested his device in 1879 by spending an hour submerged in a water tank, then one week later by diving to a depth of 5.5 m in open water, upon which occasion he was slightly injured when his assistants abruptly pulled him to the surface.

There was documentation of inventors working with the concept well before the first patent. It's not a new technology.



Bob

 

[Stoo]

Apart from all the expensive bits that go into a rebreather, I suspect that the biggest reason no company has built a cheap rebreather is that companies aren't in business to make cheap stuff. They're in business to make a profit, even if it's a modest one. The exceptions would include the Walmarts of the world where they sell cheaper stuff, but they can do that by moving huge volume through a very streamlined supply chain and by beating up suppliers.

So basically if a company is making money selling an expensive rebreather, there really isn't much reason to try to produce a cheap version, especially in what is a very tiny market.

 

[Sbiriguda]

So basically if a company is making money selling an expensive rebreather, there really isn't much reason to try to produce a cheap version, especially in what is a very tiny market.

That's true, still I don't really understand why there should be a tiny market for rebreathers while the "usual" diving with regs is becoming quite big and it experiences for sure a price decrease.
Perhaps rebreather diving is not for recreational dives. If you just want to dive one hour and then go home diving with tanks and regs is probably easier. So since most people actually do recreational dives there is no advantage to use a rebreather and therefore no incentive for the industry to try mass production and to cut the prices

 

[Stoo]

That's true, still I don't really understand why there should be a tiny market for rebreathers while the "usual" diving with regs is becoming quite big and it experiences for sure a price decrease.

To be clear, I don't dive a RB, even though I dive a fair bit (150 dives a year) mostly on medium-depth "techreational" dives. But I have lots of (mostly younger) friends who do dive them. We have had many conversations about them. Currently, and to put it in a nutshell, there simply is no advantage to the vast majority of divers to use a rebreather. They are complex, maintenance-heavy, sophisticated machines. They require a source of pure O2 delivered at high pressure. They're heavy (compared to a single tank). Most people terminate dives because they're cold or at the deco limit, whatever that might be.

And someone may well prove me wrong, but I am under the impression that the overall diving market size is actually shrinking. Many divers are older and younger people aren't entering the sport like they used to.

The real advantage of a rebreather is for use on tri-mix dives. The gas savings will pay for the machine in no time. And the VAST majority of divers will never be within a days' walk of a trimix dive.

And finally, and perhaps most importantly, SCUBA is pretty much idiot-proof. You turn the tank on, stick the sucky thing in your face and go diving. There's nothing to it. I have always maintained that I can teach someone everything they need to know to dive in about 10 minutes. Not every dive, but for most warm water dives, it really is dirt simple. Look at the diving demographic... literally anyone can SCUBA dive.

On the other hand, a rebreather is a complex machine that can kill the operator with no warning if it's not operated properly. We see it all the time. The recent fatality of Andy Phillips may ultimately turn out to be another example of this.

In my home base of Tobermory, most serious accidents (i.e. the ones where someone ends up dead) are almost exclusively one of two types in recent years... death WHILE diving from some medical issue or death on a breather.

I love the concept of a rebreather, and if I was 20 years younger I MIGHT be diving one, but likely not. They are a serious tool for serious diving.

They simply don't make sense for recreational diving IMHO.

Regardless of the price.

 

[stuartv]

I think some of the responses here somewhat miss the point.

I mean, yes, diving a CCR - in their various current incarnations - is serious business and requires a MUCH larger commitment from the diver, in terms of time, money, and training, than does OC scuba.

I think the real question is, why is there not, this many years after rebreathers were originally conceived, a rebreather (probably semi-closed circuit) that is just as stupid simple and stone reliable as OC?

Imagine a device that you wear on your back, that is no heavier than an AL80, that takes a cartridge for a scrubber and a small cylinder of Nitrox. It's all purely mechanical. The design ensures that the diver always has good breathing gas - as long as the scrubber cartridge is not exhausted and not manufactured with any defects, and the "regulator device" is working correctly.

The Hollis Explorer seems like it was a step in this direction, but maybe it went too far with all its electronics? Could it have been done as a purely mechanical device? It wouldn't give the user the feedback that the electronics support. But, if the device itself were comparable in simplicity and reliability to OC, would it really need to give the user all the feedback?

No advantage for recreational divers? Well, what about the advantage of, in essence, having no real concern over running out of gas? As long as the diver starts with a reasonably full cylinder and stays reasonably close to their NDL - both of which being responsibilities that the OC diver has, too.

The major "cons" to this concept seem to me to be:

- developing the tech to support it so that it really is comparable in reliability to OC diving.

- buoyancy is definitely harder to master on anything with counterlungs. At least, it seems that way to me. I would definitely be interested in seeing some kind of comparative analysis of buoyancy control between brand new divers on OC and brand new divers that start on CC. Both have to manage BCD volume. One has to manage lung volume. The other has to manage loop volume. Is one really inherently more difficult than the other? Or are they the same only different? My intuition is that OC is always going to be a little easier. Lung volume is self-correcting on depth changes (as long as you don't hold your breath), where loop volume is not.

 

[Stoo]

No advantage for recreational divers? Well, what about the advantage of, in essence, having no real concern over running out of gas?

I didn't miss the point of the original post.

As for the big advantage you mention and I quoted... That can be accomplished with a $149 SPG and a little self-discipline. And as shocking as this might be, RBs run out of gas too. In addition, they have sorb that expires. To make matters worse, on a RB these "failures" aren't always even apparent to the diver. I was diving with someone last year who discovered that cold water had a huge effect on sorb life. We briefly separated, and when I came back, her camera system was lying on the deck of the wreck we were on. She had dinner-plate eyes and a stunned look on her face. I stuck her bailout in her mouth and all was fine, but she could have died right there and not even noticed it. Her sorb "should have" had another hour's life in it.

At least when you run out of gas on SCUBA, it's pretty bloody obvious! My point is that even the simplest so-called "advantage" is more complex.

As fr the dirt simple aspect, I suspect you could ask the same question of almost any piece of technology. Why isn't there a cheap Space Shuttle? Or a $375 MacBook? Or a $12,000 car. (Oh right, we had the Lada. Need I continue? )

Because in making it "cheap" you need to drop many of the things that make it work, or be safe.

Guys I know that dive RBs have as many as five sensors, each monitored by a separate controller, often a Shearwater. I'm no engineer, but I assume that there are five of these for good reason. My observations would suggest that having a single failure is quite common. I guess a manufacturer could same $4000 and have a RB with one sensor, but I don't think anyone would want it.

Many of the "cheaper" arguments could apply to SCUBA gear as well. When I started diving in 1974, Octopus regs didn't exist. There were several double fatalities in Tobermory around that time, when buddy breathing failed. We had tiny "life vests" and buoyancy control was largely done through weight-belt adjustments and brute force. Two simple examples, but the development of Octopus seconds and actual BCDs made diving safer... and more expensive.

 

[stuartv]

I didn't miss the point of the original post.

As for the big advantage you mention and I quoted, really? That can be accomplished with a $149 SPG.

I have an SPG on my OC gear. Running out of gas is still ALWAYS a concern. That's why I have an SPG and I monitor it.

When I dive my CCR, it's just not. From reading the posts in the Rebreather subforum, there are experienced CCR divers who don't ever look at their CCR SPGs during a dive. THAT is when there is no real concern about running out of gas.

The other concerns you mentioned seem, by and large, to be concerns for CCRs, which is why I specifically mentioned that the device I was trying to describe might have to be an SCR. I have 5 sensors in my CCR. But, if I were on an SCR that, by the way it works, guarantees me to always have breathable gas in the loop (barring the possibility of CO2 contamination) do I really NEED to have ANY O2 sensors?

I'm not saying I don't. I'm asking the question. I only know a little about SCR, but I thought part of the deal is that it constantly injects Nitrox (at least, for ones like the Explorer) to ensure your loop is breathable. Maybe it does that by monitoring O2 sensors and only injecting when necessary. But, could you not make one with a Constant Mass Flow setup (like the rEvo CCR) that, while it may be less efficient than monitoring and on-demand injection, would ensure a breathable loop at all times AND still extend the gas supply by many times (with no need to monitor the O2)?