Doing Tech+Cave on a RB?

[webhead]

To this I say...

Its not error proofing as much as its designing a system which stays on the road by itself. Can't cross the double yellow or the white shoulder lines.

But if you say left it goes that way. You do control all the various manipulations to get the ppO2 to rise or use off-board gas as a SCR whatever. But then there are some inherent rules of the road which limit your abilities. Tough - its for your own good.

In the new stealth fighter (F22 I think its called) the plane can pull an enormous turn, 20gs whatever. But the onboard computer limits the turn capability to make sure the pilot doesn't pass out in the process.

There seems to be a general attitude that most divers want to control their own RB using the info provided. But if you foolishly tell it to pull 20gs and pass out (e.g. by using the dilutant button when you should be using the O2 button on a mCCR is wheer I think this happened) That's a design flaw IMO.

Your example may be backwards. The only place I can think of where adding dil instead of O2 is bad is if you are on the surface and diving a trimix of 18/xx or less. Adding O2 when you meant to add dil can be very bad at depth. Either way, good point of what people have done to try and hurt themselves.

So here's what has happend in the last several years along those lines of development. Electronics have become dive smart - auto on. Electronics have added HUDs, buzzers and vibrating components to "inform" the diver of issues. But the haven't gotten here w/out controversy. Do you like a car that constantly beeps because you don't have your seatbelt on? (not a recommendation or an endorsement to not use a seatbelt in a car - always drive responsibly ) This goes on and on for nearly every part of any rebreather. You get the idea.

So how do you keep someone w/ their finger on the button... the O2 MAV from going hyperoxic? Have the computer monitor PO2 and inject dil when PO2 goes past 1.6? How is the diver suppose to keep from blowing to the surface w/ all that added buoyancy? Not a slam, just giving you a flavor of the stuff that gets "discussed" in the RB cyber world.

The Cis seems to be an exception to this information but not that much computer control concept. The Kiss being one unit on the other end of the spectrum (as far as I can tell).

Am I way off base here? We can talk about internal fault correction next

It's been a while since I've touched the Cis on a table or talked to the owner, who was my RB instructor, so I can't list all it's shortcomings. Most everyone will agree that it was ahead of its time but those that know it will also say that the manual for it and the training was more like learning to fly intruments than take private pilot lessons. For non aviation folks, the difference between learning to drive an automatic car and a motorcycle. It was far from automatic. Any Cis gurus, feel free to flame me here.

Several are working on CO2 monitors and at least one manufacturer has a O2 injection if the loop PO2 falls below .19.

Not sure I understand what you are saying? My electronics injects O2 if the PO2 falls below the setpoint that I configure (i.e. .4 or 1.2) and non of them allow me to set the PO2 below 0.21. Most make you have something higher than 0.3. Not a slam but sounds like you are talking about adding a setpoint controller to a mCCR (mechanical). Trying to automate a dil flush for high CO2 has other issues other than just making a functional CO2 sensor system.

But deciding HOW to do something is part of the problem. Some makers and divers would say to inject O2 but others may say to inject diluent. Some say you need a wet switch and others say no. Look at all the debate we have just here on what needs to be fixed and what is right. We're getting there. Maybe if we can get one these Yahoo or Google founders to bring money and their type of innovation to the business.

 

[webhead]

For me, I would love to have a fully automatic and idiot proof RB. But not at the expense of being a diving crash test dummy, adding 10 lbs of gear, removing my recovery options or adding $1000's to the price.

When they get to rev v2.5, I'll using it w/out concern. But v1.0 makes me think of things like the initial release of every major version of Windows.

Keep the gear small and light enough so I can travel w/ it - chances are, in 5 - 10 years, you'll be limited to 30 lbs of checked baggage and be charged $1 a lb over that in each direction.

Some of the things you want to fix might interfere w/ what I might do to address an issue today. If I go to OC and abort a dive, will you be able to tell the computer that so it won't be adding gases to the loop and screwing w/ my buoyancy? Are you going to have electric valves on the tanks so I can't shut off my O2 when a solenoid sticks open?

And can I get that 2 weeks after ordering it for less than the price of a car?

If you can answer yes, then do you need an investor in that company?

 

[trob09]

To some extent yes, except there are more and more 'rain sensing' windshield wipers, daytime running lights, and breathalyzer interlock like devices.

But RB divers seem to shun the concept of the RB itself prohibiting a ppO2 of 2.5 Or a WOB (heat?) sensor which triggers a loop flush.

Is that because the technology hasn't been reliable enough to really trust to "drive" for you? I.e. your brain is the only fault free peice of equipment you take on the dive?

So how does the rebreather prevent a PO2 of 2.5? What happens if the diver isn't prepared for a loop flush? It just pumped several cubic feet of gas into the loop and now you're positively bouyant, trying to dump the loop, your drysuit and your BC all at the same time - no thanks.

I wouldn't want that any more than I'd want my car to decide I'm going too fast & slam on the brakes.

Here's my philosophy - I am the weakest link in the dive. I consider myself a weaker than average diver who monitors the crap out of my unit and obsessively checks the unit pre-dive (and post dive). If my unit gets to a PO2 of 2.5 I've failed. That's more than double what I run as a bottom PO2. If it gets there (or below .5) without me seeing that and taking corrective action, that's my fault. To me that's the same as if I ran into a tree while driving because I stopped looking at the road and took my hands off the wheel for 5 minutes while driving down the highway.

Put another way, if an open circuit diver runs out of gas on the bottom because the didn't know their consumption rate, didn't know how much gas they started the dive with and didn't check their SPG during the dive, is it the diver's fault or is it the tank, regulator and SPG's fault for not taking them to the surface when their gas got low?

 

[trob09]

Not sure I understand what you are saying? My electronics injects O2 if the PO2 falls below the setpoint that I configure (i.e. .4 or 1.2) and non of them allow me to set the PO2 below 0.21. Most make you have something higher than 0.3. Not a slam but sounds like you are talking about adding a setpoint controller to a mCCR (mechanical). Trying to automate a dil flush for high CO2 has other issues other than just making a functional CO2 sensor system.

Sorry, perhaps I wasn't being clear. I was responding to a comment that units can be turned off on the surface and allow a diver to pass out due to a falling PO2. The HammerHead will not allow this to happen. Even in OC mode (i.e. Solenoid disabled), it will inject O2 if the PO2 falls below .19. Of course it will also inject O2 to maintain the setpoint selected in CCR mode.

 

[webhead]

This is exactly what I was wondering (although I really didn't know how to ask) - how they did gas injection, thanks

The mechanics of the closed loop gases is that you generate about the same volume of CO2 as O2 you metabolise. The scrubber is a chemical reaction that removes CO2 from the gas. This is where the volume decrease comes from. So if you are swimming along and it is getting harder to take a full breath, you are descending, getting water in the loop or not getting O2 injected. The opposite is true. You start becoming buoyant/have excess gas in the loop, you are getting gas added somewhere - usually a leak. Could be dil or O2 but a quick look at the PO2 gauge should tell you which it is.

The ADV adds dil when the loop volume is too low. The computer adds O2 (on an eCCR) when the PO2 drops below the setpoint. The diver usually has MAVs where they can add either manually.

 

[webhead]

Sorry, perhaps I wasn't being clear. I was responding to a comment that units can be turned off on the surface and allow a diver to pass out due to a falling PO2. The HammerHead will not allow this to happen. Even in OC mode (i.e. Solenoid disabled), it will inject O2 if the PO2 falls below .19. Of course it will also inject O2 to maintain the setpoint selected in CCR mode.

Gotcha. I am aware of electronics that could be turned off in the water. But remember that all units can be shut off in other ways - no O2 because of out of gas or tank valve closed. If you learn to dive a SCR, you probably were taught (on the Dolphin, I know you were) to turn the tank off on the surface. You do that to the O2 tank on a CCR and you better hope the volume diminishes enough before the PO2 drops or you're likely to take a nap. All electronics run on batteries which can be a "hard off" for any computer.

But fact is that people have had accidents because PO2 was not being maintained either thru computer failure - electronics or battery or O2 supply failure - valve closed, tank empty or wrong gas in tank.

The difference between OC and CC is that if any of those were true for OC, you'd know it pretty quickly. On CC, you might be breathing a hypoxia gas for a while before you realize the problem. Now how do we prevent any of those from happening other than proper training and diligent diving?

 

[rjack321]

Without body recovery (sorry to be morbid) there is no way to determine the cause of the fatality. By extension, there is no way to determine if better engineering was needed or if it would have prevented this accident.

You're right. Sure seems like there was ppO2 drop, like gas not on?

 

[trob09]

Gotcha. I am aware of electronics that could be turned off in the water. But remember that all units can be shut off in other ways - no O2 because of out of gas or tank valve closed. If you learn to dive a SCR, you probably were taught (on the Dolphin, I know you were) to turn the tank off on the surface. You do that to the O2 tank on a CCR and you better hope the volume diminishes enough before the PO2 drops or you're likely to take a nap. All electronics run on batteries which can be a "hard off" for any computer.

But fact is that people have had accidents because PO2 was not being maintained either thru computer failure - electronics or battery or O2 supply failure - valve closed, tank empty or wrong gas in tank.

The difference between OC and CC is that if any of those were true for OC, you'd know it pretty quickly. On CC, you might be breathing a hypoxia gas for a while before you realize the problem. Now how do we prevent any of those from happening other than proper training and diligent diving?

I'm with you and agree with the comments. Again, I was just pointing out that there is at least one manufacturer who is trying to build in a low PO2 safety even when the electronics are "off". Of course that won't overcome a lack of O2 (turned off or empty), solenoid stuck closed or total loss of electronics - each of which has it's own remedy.

I still maintain that I'm the best monitor and I need to keep reminding myself that I am the monitor. Richard Pyle said it best, complacency kills. For me, adding greater and greater levels of complexity is most likely going to move me closer and closer to complacency, because hey - this thing dives itself, right?.

 

[trob09]

You're right. Sure seems like there was ppO2 drop, like gas not on?

Hard to say. Without trying to sound like a rebreather apologist, there could be medical issues that drove the incident, or there could be other equipment issues unrelated to PO2.

Without examining the body or the rebreather, it is impossible to say with any credibility what the cause is. Any guess at what it might be is just that - a guess.

 

[rjack321]

Thank you for the learning experience and comparisons to my known universe (e.g. cars, planes, etc.)

So I'm sitting here a GUE Tech1 diver. Normoxic trimix + 1 deco gas. Gauge + ratio deco planning on the fly. About as anti-potted-computer-monitored-injector as you can get.

I don't have a ton of dives this way but the thought process makes sense to me. My brain likes linear functions of time and depth with gas proportions remaining constant. I have no need or reason to return to using my old Vyper in computer mode. Or get a VR3 for that matter.

I also have very limited desire to get Tech2 to only then try an RB80. (I don't think there are any intro RB80 classes out there )

So which units are:
a) constant gas parameters (you're on 32% the whole dive, not you run a ppO2 of 1.2 the whole dive)
b) compatible with mental deco planning on the fly??