Hybrid Rebreathers

**Dave Sutton** · 22nd April 2008, 13:53

Bruce and others: Been reading with inerest, and not commenting, as Mike has taken the charge and is doing a bang-up job of it.

Now that the discussion has gone to the predicatble level of where we'll all talk about reliability of electronics for another 1000 posts without any real result...

, let me offer my ideas.

Starting this summer, I'll be diving a hybrid rEvo: The system can be configured in 2 very different ways in about 5 minutes, no tools needed. And while configured in the "Mode A" way, it can be used in two TOTALLY different ways. Let me first articulate how it can be configured, and then how I plan to exploit it to my advantage (I hope).

Configuration "Mode A": Blocked First Stage feeding both solenoid and orifice.

Configuration "Mode B": Unblocked First Stage feeding solenoid only, Orifice Blocked off (no flow).

Simple, eh" Remove the first stage cap and then install an orifice plug to go from "A" to "B" and reverse the work to go back.

OK.. how to use it?

Mode A is the "normal" one for anything shallower than about 240 feet. Guess what? This represents about 90% of what I do. So, how to use it there?

I think the thing is to CHOOSE ONE WAY and then just let the other system run in parallel and essentially ignore it.

If you believe than a mCCR is the way to go, run the setpoint at 0.5, forget that the controller exists (save for doing deco calcs) and fly the unit as a true mCCR. If the solenoid fails... so what. You NEVER expected it to fire anyhow and are not relying on it. It'll sit there, transparent, just latent and waiting.

If you believe that a eCCR is the way to go, set the setpoint up to 1.2 and let the solenoid do it's work. Monitor the system like any other eCCR and forget that the orifice even exists. It'll be there, transparent, just humming along.

And if you want to change "philosophies mid-dive? Go for it. You just need to be able to ACCURATELY switch your brain from one mode to the other WITH NO ERRORS. I think, really, that the ONLY way to be able to do this is to have substantial habit pattern experience with BOTH eCCR and mCCR systems PREVIOUSLY (likely on other units, or this particular unit configured as an either/or system).

Why am I doing this myself? Simple: I'm teaching the unit and need to be able to teach BOTH methods of use to my students. It does not make sense to modify the unit to an either/or rig every time the situation changes. Would I deliberately ADD this sort of system to a rig that was not fitted with it 'out f the box"? Probably not. I'm quite happy with *either* a mCCR or an eCCR and really don't see the "need" for both. Now, with that said: I think that the hybrid system that I have (2 rEvodreams, one orifice, one solenoid, and a Shearwater cntroller) absolutely ROCKS from an "expedition reliability standpoint". If/when any of the 'lekkies goes tits-up, I can still continue my trip with the rig by just changing my BRAIN over to the other mode. I can dive it as a mCCR using any ONE of the three 'lekkies boxes. That's pretty darned reliable.

+++++++++++

"Mode B" is how I'll configure the rig for deep diving. it becomes a pure eCCR for that work. Not a lot to discuss there: It's just a Shearwater controlled eCCR with dual rEvodreams/HUD's for monitoring. Still pretty darned capable from a monitoring reliability standpoint.

Anything else I'm missing? Bruce? Mike?

Dave

.

OceanOpportunity · 22nd April 2008, 14:29

phew! thanks for some backup Dave!

Your explanation, I believe, is what folks need to take home as the value/benefit of a 'hybrid' system. That being that there is the option to dive with either Mode A or B as you have described it, depending on the mission at hand.

I feel like the term 'hybrid' implies that both Modes should be used synergistically, and this is being considered by many as a value-add of the system. Folks thinking/diving this way, IMO, is a step in a direction away from personal reliability/responsibility into relying on a system which raises more questions than answers at this point...but why beat a dead horse on this rant

, likewise on the systems reliability issue.

My underlying point, as an instructor, is that the diver should appreciate the patterns of recognition I described for either mode. These take little to no effort and with time become second nature while diving a ccr. WHen there is a recognized disruptance in this pattern, the 'oh shit' alarm should go off and then back to the manual add button with more frequency, which is then the most reliable system. The psychlogical, not to mention physical, 'oh shit' alarm goes off well in advance of dire straits. At that point I'd rather be in control myself than depend on yet another system, which as I've pointed out, may or may not be working.

Ben Field · 22nd April 2008, 14:44

Quote: (Originally Posted by Dave Sutton)

Configuration "Mode A": Blocked First Stage feeding both solenoid and orifice.

<snip>

Mode A is the "normal" one for anything shallower than about 240 feet.

Just to confirm- the rEvo solenoid can happily run at 9-10bar or more? (Assuming you need 9bar or greater IP (lots of people at 11-12.5bar) to dive orifice equpied MCCR to 240ft just to keep the flow moving?)

While I cannot complain about having two different modes available I think the goal should be to make a safe system- in my mind the safest approach is to have a unit appear to run exactly as a MCCR with the solenoid and software waiting and watching in parachute/watchdog mode to start beeping/buzzing first then firing secondly should the unit for whatever reason fail to dive with MCCR parameters.

To me the ability to alter the unit to run as pure ECCR would be of no interest, better to fix the inherent shortcoming of MCCR (depth ability- higher IP, smaller orifice, if that is what you desire to run ECCR for), also task loading (get a decent HUD) hands free operation (set IP correctly or fit a SNOG

) than to fall back on electronics for the sake of it.

Of course this assumes that the "MCCR paranoia" is what makes them inherently more closely watched, so far apparently safer... not that I wish to reignite that debate

BEN

bgpartri · 22nd April 2008, 14:57

At this point, I'm leaning towards diving the system with both active.

First, though, I have a slightly different take on why people are apparently safer on mCCR. With no other evidence than talking to lots of divers, I find that mCCR divers seem to understand what's going on with their systems better. Why? Because they have to. I see eCCR divers with fairly significant misconceptions even after a year of diving.

So my take is that the manual nature of the unit cause the diver to create a "clear mental model" of the system early in their career. This serves them well when problems occur.

At this point, if I were to put another family member on a rebreather, I would want them to do a year on an mCCR. I like the idea of starting off with mCCR, then adding eCCR later if you want.

As far as diving, I would propably dive it as eCCR and use the orifice to delay onset of o2 problems. The orifice drives when you are at a steady depth and relaxed. As your exertion increases, the solenoid kicks in.

I don't see any need to change the first stage. I just leave it blocked. Of course, our diving is almost all 250 or less.

But I think this is an evolving area, and there's still lot's to learn.

Bruce

paulraymaekers · 22nd April 2008, 15:24

Quote: (Originally Posted by Ben Field)

Just to confirm- the rEvo solenoid can happily run at 9-10bar or more? (Assuming you need 9bar or greater IP (lots of people at 11-12.5bar) to dive orifice equpied MCCR to 240ft just to keep the flow moving?)

hello Ben, the rEvo solenoid runs happily till 17 bar :-)

regards

paul

**Gill Envy** · 22nd April 2008, 15:57

Quote: (Originally Posted by PnL)

Mike,

Is there any evidence to suggest that the solenoid would not fire in "parachute" mode when you need it? I've never had a solenoid on my rig so I'm curious to what the failure rate of eCCR's are such that this is a real concern during a dive, especially if you are doing your predives and the solenoid is firing properly.

Having experienced a solenoid fail mid dive on my wife's unit before going mCCR, it's like asking how can you trust a parachute that may not open or a safety net that may not be there when you need it. If you can't trust it enough to use it all the time, why trust it to be working at some random time in the future. The chances are small, but I don't care what anyone says, they fail open and closed and in my wife's case, intermittently... it started working spontaniously again too

!

I'm with Michael on this one, consisten pattern is key to good reaction time. In the end the convenience of auto inject just did not measure up to the inconvenience and dangers they can cause when they fail unexpectedly.

g

HayCol · 22nd April 2008, 18:59

Hi all and thank for an interesting thread.

Quote: (Originally Posted by Gill Envy)

I'm with Michael on this one, consisten pattern is key to good reaction time.
g

Would using an orifice for basic flow and a solenoid to make up the difference increase the reaction time available to the diver in the event of the an electronic failure?

I know how long an MCCR loop takes to decay (between O2 additions) and how long that gives the diver to correct the situation. How much reaction time does the diver get to deal with the O2 decay in the loop when an eCCR fails? (I've never dived eCCR but my guess is, not long. Please correct me if I'm wrong.)

In this configuration would the diver have longer to spot that the loop O2 was decaying owing to eCCR failure and if the orifice blocked the solenoid would inject more often?

Colin.

Hanssing · 22nd April 2008, 21:02

Quote: (Originally Posted by Ben Field)

Of course this assumes that the "MCCR paranoia" is what makes them inherently more closely watched, so far apparently safer... not that I wish to reignite that debate

I'm not diving in hybrid and I dont think I will..... yet
But I think the mCCR mentality should be able to keep up, if you run the eCCR setpoint as low as 0.5.

My half assed reasons for thinking so include:

The shearwater has a nice downloadable PPO-curve. If nothing else how can you not wish to keep that constant when you see it ofr you self. So you get a very good postdive analysis of you performance.
You will inherit a deco-hit for not keeping the correct PPO and though you'll probably not die anymore you still have direct incentive to keep you on your toes. Ie. as a diver a poor mCCR pilot will still get "punished".

If I ever we're to dive hybrid mode, I'd leave the setpoint at 0.5'ish, knowing that if the muck hits the fan I will have a backup for my busy hands, and allso an extra safeguard when at the surface, where I cannot allways read the HUDs (running O2-mode).

Just my "2 øre"

Nicolai

Stephane · 22nd April 2008, 21:09

Hi all,

Why not using the electronic ? Why should not use best of both worlds?

**Gill Envy** · 22nd April 2008, 21:13

Quote: (Originally Posted by Stephane)

Hi all,

Why not using the electronic ? Why should not use best of both worlds?

I think one of the keys to diving mCCR that makes you pay more attention is diving knowing you don't have a safety net. I'm concerned that having a safety net may inadvertently dilute that mindset.

22nd April 2008, 13:53	#21 (permalink)
Dave Sutton Living on Animal Farm Current Rebreather/s: Sport Kiss MK 15.X rEvo Other CCR Azimuth Home Build Other Rebreather/s: Classic Kiss rEvo Other CCR Azimuth Home Build Join Date: Jun 2006 Location: Narragansett, Rhode Island and Hackettstown, New Jersey Posts: 2,463	Re: Hybrid Rebreathers Bruce and others: Been reading with inerest, and not commenting, as Mike has taken the charge and is doing a bang-up job of it. Now that the discussion has gone to the predicatble level of where we'll all talk about reliability of electronics for another 1000 posts without any real result... , let me offer my ideas. Starting this summer, I'll be diving a hybrid rEvo: The system can be configured in 2 very different ways in about 5 minutes, no tools needed. And while configured in the "Mode A" way, it can be used in two TOTALLY different ways. Let me first articulate how it can be configured, and then how I plan to exploit it to my advantage (I hope). Configuration "Mode A": Blocked First Stage feeding both solenoid and orifice. Configuration "Mode B": Unblocked First Stage feeding solenoid only, Orifice Blocked off (no flow). Simple, eh" Remove the first stage cap and then install an orifice plug to go from "A" to "B" and reverse the work to go back. OK.. how to use it? Mode A is the "normal" one for anything shallower than about 240 feet. Guess what? This represents about 90% of what I do. So, how to use it there? I think the thing is to CHOOSE ONE WAY and then just let the other system run in parallel and essentially ignore it. If you believe than a mCCR is the way to go, run the setpoint at 0.5, forget that the controller exists (save for doing deco calcs) and fly the unit as a true mCCR. If the solenoid fails... so what. You NEVER expected it to fire anyhow and are not relying on it. It'll sit there, transparent, just latent and waiting. If you believe that a eCCR is the way to go, set the setpoint up to 1.2 and let the solenoid do it's work. Monitor the system like any other eCCR and forget that the orifice even exists. It'll be there, transparent, just humming along. And if you want to change "philosophies mid-dive? Go for it. You just need to be able to ACCURATELY switch your brain from one mode to the other WITH NO ERRORS. I think, really, that the ONLY way to be able to do this is to have substantial habit pattern experience with BOTH eCCR and mCCR systems PREVIOUSLY (likely on other units, or this particular unit configured as an either/or system). Why am I doing this myself? Simple: I'm teaching the unit and need to be able to teach BOTH methods of use to my students. It does not make sense to modify the unit to an either/or rig every time the situation changes. Would I deliberately ADD this sort of system to a rig that was not fitted with it 'out f the box"? Probably not. I'm quite happy with either a mCCR or an eCCR and really don't see the "need" for both. Now, with that said: I think that the hybrid system that I have (2 rEvodreams, one orifice, one solenoid, and a Shearwater cntroller) absolutely ROCKS from an "expedition reliability standpoint". If/when any of the 'lekkies goes tits-up, I can still continue my trip with the rig by just changing my BRAIN over to the other mode. I can dive it as a mCCR using any ONE of the three 'lekkies boxes. That's pretty darned reliable. +++++++++++ "Mode B" is how I'll configure the rig for deep diving. it becomes a pure eCCR for that work. Not a lot to discuss there: It's just a Shearwater controlled eCCR with dual rEvodreams/HUD's for monitoring. Still pretty darned capable from a monitoring reliability standpoint. Anything else I'm missing? Bruce? Mike? Dave . __________________ . "All animals are equal, but some animals are more equal than others" Professional Small Boy: Never Successfully Cubicled.
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22nd April 2008, 14:29	#22 (permalink)
OceanOpportunity for a world of water Current Rebreather/s: Other CCR Dolphin Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Other CCR Dolphin Home Build Join Date: Nov 2006 Location: Providence, RI USA Posts: 465	Re: Hybrid Rebreathers phew! thanks for some backup Dave! Your explanation, I believe, is what folks need to take home as the value/benefit of a 'hybrid' system. That being that there is the option to dive with either Mode A or B as you have described it, depending on the mission at hand. I feel like the term 'hybrid' implies that both Modes should be used synergistically, and this is being considered by many as a value-add of the system. Folks thinking/diving this way, IMO, is a step in a direction away from personal reliability/responsibility into relying on a system which raises more questions than answers at this point...but why beat a dead horse on this rant, likewise on the systems reliability issue. My underlying point, as an instructor, is that the diver should appreciate the patterns of recognition I described for either mode. These take little to no effort and with time become second nature while diving a ccr. WHen there is a recognized disruptance in this pattern, the 'oh shit' alarm should go off and then back to the manual add button with more frequency, which is then the most reliable system. The psychlogical, not to mention physical, 'oh shit' alarm goes off well in advance of dire straits. At that point I'd rather be in control myself than depend on yet another system, which as I've pointed out, may or may not be working. __________________ Michael Lombardi Oceans of Opportunity www.oceanopportunity.com Elected Director, Society for Human Performance in Extreme Environments MN'07, The Explorers Club Project Manager, Diving a Dream
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22nd April 2008, 14:44	#23 (permalink)
Ben Field CK+Shearwater Current Rebreather/s: Classic Kiss Other Rebreather/s: Sport Kiss Join Date: Aug 2005 Location: London, England Posts: 1,451	Re: Hybrid Rebreathers Quote: (Originally Posted by Dave Sutton) Configuration "Mode A": Blocked First Stage feeding both solenoid and orifice. <snip> Mode A is the "normal" one for anything shallower than about 240 feet. Just to confirm- the rEvo solenoid can happily run at 9-10bar or more? (Assuming you need 9bar or greater IP (lots of people at 11-12.5bar) to dive orifice equpied MCCR to 240ft just to keep the flow moving?) While I cannot complain about having two different modes available I think the goal should be to make a safe system- in my mind the safest approach is to have a unit appear to run exactly as a MCCR with the solenoid and software waiting and watching in parachute/watchdog mode to start beeping/buzzing first then firing secondly should the unit for whatever reason fail to dive with MCCR parameters. To me the ability to alter the unit to run as pure ECCR would be of no interest, better to fix the inherent shortcoming of MCCR (depth ability- higher IP, smaller orifice, if that is what you desire to run ECCR for), also task loading (get a decent HUD) hands free operation (set IP correctly or fit a SNOG ) than to fall back on electronics for the sake of it. Of course this assumes that the "MCCR paranoia" is what makes them inherently more closely watched, so far apparently safer... not that I wish to reignite that debate BEN __________________ www.hugsac.org.uk Beware Fridge Suck
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22nd April 2008, 14:57	#24 (permalink)
bgpartri Rebreather Zealot Current Rebreather/s: Megalodon Other Rebreather/s: Inspiration Classic Sport Kiss Classic Kiss Titan Join Date: Apr 2005 Location: Vancouver, Canada Posts: 373	Re: Hybrid Rebreathers At this point, I'm leaning towards diving the system with both active. First, though, I have a slightly different take on why people are apparently safer on mCCR. With no other evidence than talking to lots of divers, I find that mCCR divers seem to understand what's going on with their systems better. Why? Because they have to. I see eCCR divers with fairly significant misconceptions even after a year of diving. So my take is that the manual nature of the unit cause the diver to create a "clear mental model" of the system early in their career. This serves them well when problems occur. At this point, if I were to put another family member on a rebreather, I would want them to do a year on an mCCR. I like the idea of starting off with mCCR, then adding eCCR later if you want. As far as diving, I would propably dive it as eCCR and use the orifice to delay onset of o2 problems. The orifice drives when you are at a steady depth and relaxed. As your exertion increases, the solenoid kicks in. I don't see any need to change the first stage. I just leave it blocked. Of course, our diving is almost all 250 or less. But I think this is an evolving area, and there's still lot's to learn. Bruce __________________ http://www.rebreather.ca Good judgement comes from experience, and experience comes from bad judgement.
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22nd April 2008, 15:24	#25 (permalink)
paulraymaekers rEvo's daddy Current Rebreather/s: rEvo Other CCR Home Build Other Rebreather/s: rEvo Other CCR Home Build Join Date: May 2005 Location: belgium Posts: 1,349	Re: Hybrid Rebreathers Quote: (Originally Posted by Ben Field) Just to confirm- the rEvo solenoid can happily run at 9-10bar or more? (Assuming you need 9bar or greater IP (lots of people at 11-12.5bar) to dive orifice equpied MCCR to 240ft just to keep the flow moving?) hello Ben, the rEvo solenoid runs happily till 17 bar :-) regards paul __________________ www.rEvo-rebreathers.com .... the earth is flat, Elvis is alive, and radial scrubbers give longer dwell time than axials...
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22nd April 2008, 15:57	#26 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,226	Re: Hybrid Rebreathers Quote: (Originally Posted by PnL) Mike, Is there any evidence to suggest that the solenoid would not fire in "parachute" mode when you need it? I've never had a solenoid on my rig so I'm curious to what the failure rate of eCCR's are such that this is a real concern during a dive, especially if you are doing your predives and the solenoid is firing properly. Having experienced a solenoid fail mid dive on my wife's unit before going mCCR, it's like asking how can you trust a parachute that may not open or a safety net that may not be there when you need it. If you can't trust it enough to use it all the time, why trust it to be working at some random time in the future. The chances are small, but I don't care what anyone says, they fail open and closed and in my wife's case, intermittently... it started working spontaniously again too! I'm with Michael on this one, consisten pattern is key to good reaction time. In the end the convenience of auto inject just did not measure up to the inconvenience and dangers they can cause when they fail unexpectedly. g __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°> Last edited by Gill Envy : 22nd April 2008 at 16:13.
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22nd April 2008, 18:59	#27 (permalink)
HayCol New Member Current Rebreather/s: Home Build Other Rebreather/s: Home Build Join Date: Oct 2007 Location: Coventry UK Posts: 5	Re: Hybrid Rebreathers Hi all and thank for an interesting thread. Quote: (Originally Posted by Gill Envy) I'm with Michael on this one, consisten pattern is key to good reaction time. g Would using an orifice for basic flow and a solenoid to make up the difference increase the reaction time available to the diver in the event of the an electronic failure? I know how long an MCCR loop takes to decay (between O2 additions) and how long that gives the diver to correct the situation. How much reaction time does the diver get to deal with the O2 decay in the loop when an eCCR fails? (I've never dived eCCR but my guess is, not long. Please correct me if I'm wrong.) In this configuration would the diver have longer to spot that the loop O2 was decaying owing to eCCR failure and if the orifice blocked the solenoid would inject more often? Colin.
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22nd April 2008, 21:02	#28 (permalink)
Hanssing flap-flop ..... flap-flop Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Nov 2005 Location: Denmark Posts: 330	Re: Hybrid Rebreathers Quote: (Originally Posted by Ben Field) Of course this assumes that the "MCCR paranoia" is what makes them inherently more closely watched, so far apparently safer... not that I wish to reignite that debate I'm not diving in hybrid and I dont think I will..... yet But I think the mCCR mentality should be able to keep up, if you run the eCCR setpoint as low as 0.5. My half assed reasons for thinking so include: The shearwater has a nice downloadable PPO-curve. If nothing else how can you not wish to keep that constant when you see it ofr you self. So you get a very good postdive analysis of you performance. You will inherit a deco-hit for not keeping the correct PPO and though you'll probably not die anymore you still have direct incentive to keep you on your toes. Ie. as a diver a poor mCCR pilot will still get "punished". If I ever we're to dive hybrid mode, I'd leave the setpoint at 0.5'ish, knowing that if the muck hits the fan I will have a backup for my busy hands, and allso an extra safeguard when at the surface, where I cannot allways read the HUDs (running O2-mode). Just my "2 øre" Nicolai __________________ Woohooo - I can change my rEvo! Its going to be bitchin' tricked out piece of gear
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22nd April 2008, 21:09	#29 (permalink)
Stephane Hey! Ho! Let's go! Current Rebreather/s: rEvo Other Rebreather/s: rEvo Join Date: Nov 2005 Location: Nantes - France Posts: 708	Re: Hybrid Rebreathers Hi all, Why not using the electronic ? Why should not use best of both worlds? __________________ Stéphane Hammer-rEvo powered!
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22nd April 2008, 21:13	#30 (permalink)
Gill Envy Shearwater Copis Diver Current Rebreather/s: Other CCR Other Rebreather/s: Evolution Other CCR Join Date: Nov 2005 Location: seattle Posts: 1,226	Re: Hybrid Rebreathers Quote: (Originally Posted by Stephane) Hi all, Why not using the electronic ? Why should not use best of both worlds? I think one of the keys to diving mCCR that makes you pay more attention is diving knowing you don't have a safety net. I'm concerned that having a safety net may inadvertently dilute that mindset. __________________ Gill Envy ...Because I wasn't born with gills! ><(°>><(°>><(°>><(°>><(°>><(°>><(°>><(°>
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