Wow! Meg design - dont know if I like this

**UWSojourner** · 29th April 2007, 19:39

Quote: (Originally Posted by Gilles)

Fellow meggies, please let us not get into denial.

I think you're confusing disagreement as to the level of risk with denial.

Yes, there is some level of risk, but in my opinion its very small. I haven't heard of any issues during a dive surrounding this "problem" - you'd think someone on Rebreather World would have posted an incident if an actual problem developed. As for me, I'd rather see design efforts focused elsewhere. Disagreement is not denial.

RonMicjan · 30th April 2007, 01:37

Sometimes folks just like to chime in on an issue whether they know anything about it or not. Sometimes design is a matter of form following function and things just work out with no other reason than they fit there.

Some of the things suggested in this thread are just plain silly, not mikes original post, cause that has been asked and answered. A rare failure of a cell could cause a bypass, but the diver would be alerted cause the display would show a value change and subsequent voting out of that particular sensor causing the prudent diver to end the dive asap. If one could get enough gas to bypass through the cell, w/o the cell's value changing (hard to imagine as the Koh would have leaked out) then the prudent diver would notice a rise in Co2 (from hypercapnic symptoms) and bailout, of course the prudent diver would have enough bailout to return to the surface after such an incident. If a diver did get enough water in the can to cause a hydralic lock, then the prudent diver would bailout, not try to suck with enough effort to damage a cell. If it aint working, try something else (bailout). The cells are threaded into a solid housing, if the cell housing failed, the portion threaded would still tend to hold the sensor together, along with the rubber cap on the top, only a small part of the gas would bypass the scrubber, most likely causing a headache after the dive, rather than some catestrophic failure like a missing scrubber. you may expect a few percent of the gas leaking through the failed sensor, while the vast majority would still make it through the scrubber and the next time around that small percent would get scrubbed and another small volume would get bypassed.

As kevin said, it aint happened yet, with 400 megs out there, I think it would have come up by now if it was a real issue. A real issue is how to get divers to actually DO the checkoff lists in a comprehensive manner, rather than just a glancing over. I mean, its only your life right?

As for testing during multi days of diving, heres my take. If you have taken it apart, test it during reassembly. During the days diving, I rarely take the head off, so I cant have mucked it up. At the end of the day, I lift off the head, power down, remove canister for repack or just set to dry, wring can moisture pads, pop the sensor carriage apart, take out the moisture pad and let the whole thing dry out, next morning, it all goes back together, and I do a pos neg ON THE CARRIAGE, then replace head and pos neg THE WHOLE SYSTEM. Run through a valve check, O2 manual, ADV, MGB (if I am using it), set the SP up, listen for injection and sensor swings, do a reverse O2 flush to bring up the PO2 in the loop and listen for the soleniod to Stop firing, check batt levels and done. About 3 minutes, longer if I repack the canister or fill cylinders, then I add in analyze and mark cylinders. This few minutes of tests verify that the entire machine is operational. Every couple days of diving, the whole unit comes apart, gets rinsed and disinfected and then the checklist comes back out for a full assembly.

This whole thread just reminds me of my favorite CCR adage. whether its a minor problem or full blown failure or even fatality "Its always diver error" Feel free to quote me on this. even it it ends up my dead ar$e.

Failure of the CCR from:
poor maintainence = diver error
not following the checklist = diver error
not fixing a problem after finding it = diver error
not changing scrubber = diver error
not analyzing gasses or swapping cylinders = diver error
not replacing batteries = diver error

After any failure of the machine, even due to a manufacturing failure, electronics failure, scrubber failure, O2 supply failure, shark eating loop, whatever
Not properly executing a bailout = diver error
not carrying enough bailout gas or improper gas contents or labeling = diver error
going to the wrong gas at depth = diver error

Ok some of these could be attributed to poor instruction, not being taught the proper assembly or bailout procedures, but this comes right back to Leon's insistance that all would be instructors come to him for the instructors course.

If one has been trained properly, then the prudent diver (heres that hypothetical feller again) can handle ANY CCR failure that comes up. Its when folks try to work around established protocall and training that problems creep in.

sorry for the long winded reply... now, on with the regularly scheduled posting

dantheman · 30th April 2007, 03:30

Quote: (Originally Posted by RonMicjan)

. . . shark eating loop, . . .

Is this something that CE certification would help with?

--dan

rdmmdr · 30th April 2007, 04:42

Ron

to say that everything that has ever gone wrong with a rebreather is the users fault, is a one sided and extremely limited approach to the problems. Ford recalls a million vehicles because 15 had a problem that no one got hurt in. To have a possible design flaw discussed in the open is the best way to ensure our security and longevity. I have yet to hear about a recall from any of the rebreather manufactures, yet we all know that they have had problems. When will someone stand-up and say i will not dive this piece of S**t until they "?" are willing to stand behind it and fix it. And not just mine but everyones out there. Or where all of you instructors required to sign nds for every manufacturer you instruct for?

Any instructor in the us. that teaches on a unit can be considered an agent of that company. any company or agent that doe's not report an incident that could have caused an injury or injury with the consumer product safety division can be charge with a felony. If there is a death involved they can be charged with with manslaughter, if this was the first occasion. If there had been a previous death they can be charged with murder 2.

If you sell it stand behind it.

rick

Gilles · 30th April 2007, 12:23

Quote: (Originally Posted by RonMicjan)

Sometimes folks just like to chime in on an issue whether they know anything about it or not. Sometimes design is a matter of form following function and things just work out with no other reason than they fit there.

The logic in the above paragraph escapes me

. It doesn't seem a huge technical hurdle, to design a sensor cartridge whose integrity doesn't need to be dependant upon a non-ISC component. Currently, it's a little like repairing a condom with an off the shelf patch, and then blowing it up to check that it's ok before using it.

Quote: (Originally Posted by UWSojourner)

I think you're confusing disagreement as to the level of risk with denial.

The meaning of this escapes me as well

. For one, the above described issue is not a fault. I make the appropriate distinction between a fault and a design weakness. The former is a FU and the latter is something adequate that can be made better.

Do you deny that the sensor cartridge could be made better? I'm a little concerned that the Meg toughness is only as good as that of the installed sensors. Perhaps if ISC made sensors...

Drmike · 30th April 2007, 13:36

Quote: (Originally Posted by RonMicjan)

A rare failure of a cell could cause a bypass, but the diver would be alerted cause the display would show a value change

No he wouldnt. The cell continues to function normally. When my cells fell apart (still waiting to hear back from teleydbne to see if it was a bad batch) on each occasion Boris (and bob) did not detect any changes - why would they?. If the cell falls apart then theres a hole thrui to the inale side so the ppo2 both sides of the hole (inhale and exhale sides) will be the same so it wouldnt show up. The cell facepate serves no function other than has the threaded boss to screw in the cell. The cell functons fine without it the membrane is not part of the faceplate.

Quote:

The cells are threaded into a solid housing, if the cell housing failed, the portion threaded would still tend to hold the sensor together, along with the rubber cap on the top, only a small part of the gas would bypass the scrubber, most likely causing a headache after the dive, rather than some catestrophic failure like a missing scrubber. you may expect a few percent of the gas leaking through the failed sensor, while the vast majority would still make it through the scrubber and the next time around that small percent would get scrubbed and another small volume would get bypassed.

Once again you seem very sure of your data. Have you tested how much of a bypass you would get and the effect? I havent tested it - which is why Im not making definative statements.

Quote:

As kevin said, it aint happened yet, with 400 megs out there, I think it would have come up by now if it was a real issue. ?

For you to believe its not a real issue you have to believe that 1) a cell couldnt fall apart (so you must conclude Im a liar of a lunatic) and/or 2) if it does fall apart the bypass will be insignificant - and that we just dont know - yet but based on my experience with a crappy fitted o-ring on my inspiration it doesnt take much of a bypass to have bad results

Quote:

.

This whole thread just reminds me of my favorite CCR adage. whether its a minor problem or full blown failure or even fatality "Its always diver error" Feel free to quote me on this. even it it ends up my dead ar$e.

the seriousness of the end result of a problem caused by diver error can me mitigated by good design. that is the point.

The fact is there is a potential risk if a cell falls apart that you can get bypass. We know it CAN happen (cells fall apart) as its happened to me. Just because it hasnt killed anyone yet and just because its not been seen by others that doesnt mean it couldnt happen. The risk is death. I would have thought that reason enough to take this quite seriously.

But hey I dont dive a Meg, but I have friends that do I. Based on my experience with cells falling apart I personally wouldnt dive a Meg now unless there was a way to ensure the cell couldnt fall apart in use, (such as previously mentioned) or that some tests proved that even if the cell fell apart the bypass was negligable. Personally I think thats a sensible approach

Skipbreather · 30th April 2007, 15:38

Hi Mike-

Regardless of where folks come down on this one I, for one, appreciate thoughtful input. Informed civil discussion of fact is always a good thing.

I was doing some mental gymnastics to see if I could piece together a simple test rig to put some numbers on the face of things when it occurred to me that I’d best be certain we’re on the same page as to the nature of the failure under consideration.

To the point: Your chief concern is with a cell that disintegrates INTERNALLY with the bypassing gas then finding a path through the hole in the back side of the cell where the Molex connector attaches, correct? Or are you talking about a failure where the actual plastic body of the cell comes apart?

Best,
Ken

RonMicjan · 30th April 2007, 16:32

Quote: (Originally Posted by rdmmdr)

Ron

to say that everything that has ever gone wrong with a rebreather is the users fault, is a one sided and extremely limited approach to the problems.
rick

oh fer crying out loud, thats not what I said, RTFP

I truly see why folks get fed up with forums and just bailout to go diving.

in the event of an accident or fatality, there is "almost" no situation that could not have been prevented, or mitigated during the incident by proper diver involvement. There, is that better.

Im not saying things dont go gunnysack, exactly the opposite, they are continually falling apart, but the diver is the link. If the diver maintains the gear, does proper skills drills, follows established procedures, the chances of "incidents" diminishes drastically and the chances of injury or fatality fall to negligible.

Mike, maybe I misunderstood what you described as the failure, if so, I apoligise, you said the sensor fell apart, this, I assumed included a leakage of the electrolyte, which would cause the sensor to not output a signal.

attached pics should show that even if the sensor was empty of parts, the resulting bypass path is tiny, the rubber cap, and threaded end would hold the body together if that is the suggested failure.

RonMicjan · 30th April 2007, 16:42

Quote: (Originally Posted by Drmike;112362
Once again you seem very sure of your data. Have you tested how much of a bypass you would get and the effect? I havent tested it - which is why Im not making definative statements.

For you to believe its not a real issue you have to believe that 1) a cell couldnt fall apart (so you must conclude Im a liar of a lunatic) and/or 2) if it does fall apart the bypass will be insignificant - and that we just dont know - yet but based on my experience with a crappy fitted o-ring on my inspiration it doesnt take much of a bypass to have bad results the seriousness of the end result of a problem caused by diver error can me mitigated by good design. that is the point.

The fact is there is a potential risk if a cell falls apart that you can get bypass. We know it CAN happen (cells fall apart) as its happened to me. Just because it hasnt killed anyone yet and just because its not been seen by others that doesnt mean it couldnt happen. The risk is death. I would have thought that reason enough to take this quite seriously.

But hey I dont dive a Meg, but I have friends that do I. Based on my experience with cells falling apart I [U)

personally[/u] wouldnt dive a Meg now unless there was a way to ensure the cell couldnt fall apart in use, (such as previously mentioned) or that some tests proved that even if the cell fell apart the bypass was negligable. Personally I think thats a sensible approach

havent tested it, but look at the pics above, how much gas bypass could get through that tiny hole?
Mike ole buddy, please dont put words in my mouth, Liar, never, lunatic maybe

been called similar myself. can you send me pics of the failed sensor, pm or email as I have tried to PM you but your box is full, so can you email me ron@tmishop.com I think you may have valid points, but I also think I have answered your points and the design is fine, in fact I may just tear the internals from an old sensor and put it in the rig and try it out for some empiracal testing.

**UWSojourner** · 30th April 2007, 16:51

Quote: (Originally Posted by Gilles)

Quote: (Originally Posted by UWSojourner)

(Originally Posted by UWSojourner)
I think you're confusing disagreement as to the level of risk with denial.

The meaning of this escapes me as well

.

In a prior post, you had implied that those on the other side of this argument were in denial. The statement means you are inappropriately equating disagreement with denial.

Quote: (Originally Posted by Gilles)

Do you deny that the sensor cartridge could be made better? I'm a little concerned that the Meg toughness is only as good as that of the installed sensors.

No, Gilles, everything can be made better. That's not the question. The question is whether there is an incremental benefit of a redesign and whether risk is truly reduced. In my opinion (not yours, not Mike's) this potential-might-happen problem is a very low risk event. No proof, just that no Meg diver has reported an issue with it in all the dives completed to date. It's not what I worry about when I'm on a Meg in the water. And I'll stack my paranoid-credentials against anyone on this forum. Is it possible - yes. Is it probable - no, it is a very low risk event in my opinion.

Quote: (Originally Posted by Gilles)

I'm a little concerned that the Meg toughness is only as good as that of the installed sensors. Perhaps if ISC made sensors...

What toughness is necessary? The sensors just sit there. They block a hole. As long as they don't spontaneously self-destruct mid-dive, they fulfill their job of sitting there. And evidently, at least to date, they do that (sit there) pretty consistently and well.

Do I care if someone finds a way to move the sensors to the post-scrubber gas path? No, go for it. Its just that this particular issue, for me, is pretty far down on my list of things I'd want addressed.

29th April 2007, 19:39	#61 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Gilles) Fellow meggies, please let us not get into denial. I think you're confusing disagreement as to the level of risk with denial. Yes, there is some level of risk, but in my opinion its very small. I haven't heard of any issues during a dive surrounding this "problem" - you'd think someone on Rebreather World would have posted an incident if an actual problem developed. As for me, I'd rather see design efforts focused elsewhere. Disagreement is not denial.
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30th April 2007, 01:37	#62 (permalink)
RonMicjan Cap Ron scourge of the NW Current Rebreather/s: Megalodon Dolphin Home Build Other Rebreather/s: Sport Kiss Classic Kiss Dolphin Home Build Join Date: Feb 2005 Location: Cape Disapointment, The Graveyard of the Pacific Posts: 1,083	Re: Wow! Meg design - dont know if I like this Sometimes folks just like to chime in on an issue whether they know anything about it or not. Sometimes design is a matter of form following function and things just work out with no other reason than they fit there. Some of the things suggested in this thread are just plain silly, not mikes original post, cause that has been asked and answered. A rare failure of a cell could cause a bypass, but the diver would be alerted cause the display would show a value change and subsequent voting out of that particular sensor causing the prudent diver to end the dive asap. If one could get enough gas to bypass through the cell, w/o the cell's value changing (hard to imagine as the Koh would have leaked out) then the prudent diver would notice a rise in Co2 (from hypercapnic symptoms) and bailout, of course the prudent diver would have enough bailout to return to the surface after such an incident. If a diver did get enough water in the can to cause a hydralic lock, then the prudent diver would bailout, not try to suck with enough effort to damage a cell. If it aint working, try something else (bailout). The cells are threaded into a solid housing, if the cell housing failed, the portion threaded would still tend to hold the sensor together, along with the rubber cap on the top, only a small part of the gas would bypass the scrubber, most likely causing a headache after the dive, rather than some catestrophic failure like a missing scrubber. you may expect a few percent of the gas leaking through the failed sensor, while the vast majority would still make it through the scrubber and the next time around that small percent would get scrubbed and another small volume would get bypassed. As kevin said, it aint happened yet, with 400 megs out there, I think it would have come up by now if it was a real issue. A real issue is how to get divers to actually DO the checkoff lists in a comprehensive manner, rather than just a glancing over. I mean, its only your life right? As for testing during multi days of diving, heres my take. If you have taken it apart, test it during reassembly. During the days diving, I rarely take the head off, so I cant have mucked it up. At the end of the day, I lift off the head, power down, remove canister for repack or just set to dry, wring can moisture pads, pop the sensor carriage apart, take out the moisture pad and let the whole thing dry out, next morning, it all goes back together, and I do a pos neg ON THE CARRIAGE, then replace head and pos neg THE WHOLE SYSTEM. Run through a valve check, O2 manual, ADV, MGB (if I am using it), set the SP up, listen for injection and sensor swings, do a reverse O2 flush to bring up the PO2 in the loop and listen for the soleniod to Stop firing, check batt levels and done. About 3 minutes, longer if I repack the canister or fill cylinders, then I add in analyze and mark cylinders. This few minutes of tests verify that the entire machine is operational. Every couple days of diving, the whole unit comes apart, gets rinsed and disinfected and then the checklist comes back out for a full assembly. This whole thread just reminds me of my favorite CCR adage. whether its a minor problem or full blown failure or even fatality "Its always diver error" Feel free to quote me on this. even it it ends up my dead ar$e. Failure of the CCR from: poor maintainence = diver error not following the checklist = diver error not fixing a problem after finding it = diver error not changing scrubber = diver error not analyzing gasses or swapping cylinders = diver error not replacing batteries = diver error After any failure of the machine, even due to a manufacturing failure, electronics failure, scrubber failure, O2 supply failure, shark eating loop, whatever Not properly executing a bailout = diver error not carrying enough bailout gas or improper gas contents or labeling = diver error going to the wrong gas at depth = diver error Ok some of these could be attributed to poor instruction, not being taught the proper assembly or bailout procedures, but this comes right back to Leon's insistance that all would be instructors come to him for the instructors course. If one has been trained properly, then the prudent diver (heres that hypothetical feller again) can handle ANY CCR failure that comes up. Its when folks try to work around established protocall and training that problems creep in. sorry for the long winded reply... now, on with the regularly scheduled posting __________________ Ron "Life is pain princess, anyone who tells you different, is selling something", The Dread Pirate Wesley. www.tmishop.com Diving bits etc.
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30th April 2007, 03:30	#63 (permalink)
dantheman Emoticonoclast Current Rebreather/s: Sport Kiss rEvo Other Rebreather/s: Classic Kiss rEvo Join Date: May 2005 Location: NorthEast USA Posts: 393	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by RonMicjan) . . . shark eating loop, . . . Is this something that CE certification would help with? --dan
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30th April 2007, 04:42	#64 (permalink)
rdmmdr designer of death Current Rebreather/s: Other CCR Other Rebreather/s: Other CCR Join Date: Mar 2006 Location: kerman,california Posts: 372	Re: Wow! Meg design - dont know if I like this Ron to say that everything that has ever gone wrong with a rebreather is the users fault, is a one sided and extremely limited approach to the problems. Ford recalls a million vehicles because 15 had a problem that no one got hurt in. To have a possible design flaw discussed in the open is the best way to ensure our security and longevity. I have yet to hear about a recall from any of the rebreather manufactures, yet we all know that they have had problems. When will someone stand-up and say i will not dive this piece of S**t until they "?" are willing to stand behind it and fix it. And not just mine but everyones out there. Or where all of you instructors required to sign nds for every manufacturer you instruct for? Any instructor in the us. that teaches on a unit can be considered an agent of that company. any company or agent that doe's not report an incident that could have caused an injury or injury with the consumer product safety division can be charge with a felony. If there is a death involved they can be charged with with manslaughter, if this was the first occasion. If there had been a previous death they can be charged with murder 2. If you sell it stand behind it. rick
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30th April 2007, 12:23	#65 (permalink)
Gilles Worship the feminine Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Sep 2005 Location: Den Haag (Netherlands) Posts: 762	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by RonMicjan) Sometimes folks just like to chime in on an issue whether they know anything about it or not. Sometimes design is a matter of form following function and things just work out with no other reason than they fit there. The logic in the above paragraph escapes me . It doesn't seem a huge technical hurdle, to design a sensor cartridge whose integrity doesn't need to be dependant upon a non-ISC component. Currently, it's a little like repairing a condom with an off the shelf patch, and then blowing it up to check that it's ok before using it. Quote: (Originally Posted by UWSojourner) I think you're confusing disagreement as to the level of risk with denial. The meaning of this escapes me as well . For one, the above described issue is not a fault. I make the appropriate distinction between a fault and a design weakness. The former is a FU and the latter is something adequate that can be made better. Do you deny that the sensor cartridge could be made better? I'm a little concerned that the Meg toughness is only as good as that of the installed sensors. Perhaps if ISC made sensors... __________________ Gilles http://www.dirrebreather.com Last edited by Gilles : 30th April 2007 at 12:28.
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30th April 2007, 13:36	#66 (permalink)
Drmike Custom Title Allowed! Current Rebreather/s: MK 15.X Ouroboros Other CCR Home Build Other Rebreather/s: Inspiration Classic Other CCR Home Build Join Date: Feb 2005 Posts: 3,165	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by RonMicjan) A rare failure of a cell could cause a bypass, but the diver would be alerted cause the display would show a value change No he wouldnt. The cell continues to function normally. When my cells fell apart (still waiting to hear back from teleydbne to see if it was a bad batch) on each occasion Boris (and bob) did not detect any changes - why would they?. If the cell falls apart then theres a hole thrui to the inale side so the ppo2 both sides of the hole (inhale and exhale sides) will be the same so it wouldnt show up. The cell facepate serves no function other than has the threaded boss to screw in the cell. The cell functons fine without it the membrane is not part of the faceplate. Quote: The cells are threaded into a solid housing, if the cell housing failed, the portion threaded would still tend to hold the sensor together, along with the rubber cap on the top, only a small part of the gas would bypass the scrubber, most likely causing a headache after the dive, rather than some catestrophic failure like a missing scrubber. you may expect a few percent of the gas leaking through the failed sensor, while the vast majority would still make it through the scrubber and the next time around that small percent would get scrubbed and another small volume would get bypassed. Once again you seem very sure of your data. Have you tested how much of a bypass you would get and the effect? I havent tested it - which is why Im not making definative statements. Quote: As kevin said, it aint happened yet, with 400 megs out there, I think it would have come up by now if it was a real issue. ? For you to believe its not a real issue you have to believe that 1) a cell couldnt fall apart (so you must conclude Im a liar of a lunatic) and/or 2) if it does fall apart the bypass will be insignificant - and that we just dont know - yet but based on my experience with a crappy fitted o-ring on my inspiration it doesnt take much of a bypass to have bad results Quote: . This whole thread just reminds me of my favorite CCR adage. whether its a minor problem or full blown failure or even fatality "Its always diver error" Feel free to quote me on this. even it it ends up my dead ar$e. the seriousness of the end result of a problem caused by diver error can me mitigated by good design. that is the point. The fact is there is a potential risk if a cell falls apart that you can get bypass. We know it CAN happen (cells fall apart) as its happened to me. Just because it hasnt killed anyone yet and just because its not been seen by others that doesnt mean it couldnt happen. The risk is death. I would have thought that reason enough to take this quite seriously. But hey I dont dive a Meg, but I have friends that do I. Based on my experience with cells falling apart I personally wouldnt dive a Meg now unless there was a way to ensure the cell couldnt fall apart in use, (such as previously mentioned) or that some tests proved that even if the cell fell apart the bypass was negligable. Personally I think thats a sensible approach __________________ Cave diving is a sport Wreck diving is a sport Diving in general is a sport 'Rebreather diving' is not a sport its the delusional obsession with a highly dangerous and often inappropriate piece of equipment Last edited by Drmike : 30th April 2007 at 13:44.
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30th April 2007, 15:38	#67 (permalink)
Skipbreather Reads the fine print Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet MK 15.X Home Build Join Date: Mar 2005 Location: Chicago, Illinois, USA Posts: 544	Re: Wow! Meg design - dont know if I like this Hi Mike- Regardless of where folks come down on this one I, for one, appreciate thoughtful input. Informed civil discussion of fact is always a good thing. I was doing some mental gymnastics to see if I could piece together a simple test rig to put some numbers on the face of things when it occurred to me that I’d best be certain we’re on the same page as to the nature of the failure under consideration. To the point: Your chief concern is with a cell that disintegrates INTERNALLY with the bypassing gas then finding a path through the hole in the back side of the cell where the Molex connector attaches, correct? Or are you talking about a failure where the actual plastic body of the cell comes apart? Best, Ken __________________ "Entropy RULES! Enjoy the interim."
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30th April 2007, 16:42	#69 (permalink)
RonMicjan Cap Ron scourge of the NW Current Rebreather/s: Megalodon Dolphin Home Build Other Rebreather/s: Sport Kiss Classic Kiss Dolphin Home Build Join Date: Feb 2005 Location: Cape Disapointment, The Graveyard of the Pacific Posts: 1,083	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Drmike;112362 Once again you seem very sure of your data. Have you tested how much of a bypass you would get and the effect? I havent tested it - which is why Im not making definative statements. For you to believe its not a real issue you have to believe that 1) a cell couldnt fall apart (so you must conclude Im a liar of a lunatic) and/or 2) if it does fall apart the bypass will be insignificant - and that we just dont know - yet but based on my experience with a crappy fitted o-ring on my inspiration it doesnt take much of a bypass to have bad results the seriousness of the end result of a problem caused by diver error can me mitigated by good design. that is the point. The fact is there is a potential risk if a cell falls apart that you can get bypass. We know it CAN happen (cells fall apart) as its happened to me. Just because it hasnt killed anyone yet and just because its not been seen by others that doesnt mean it couldnt happen. The risk is death. I would have thought that reason enough to take this quite seriously. But hey I dont dive a Meg, but I have friends that do I. Based on my experience with cells falling apart I [U) personally[/u] wouldnt dive a Meg now unless there was a way to ensure the cell couldnt fall apart in use, (such as previously mentioned) or that some tests proved that even if the cell fell apart the bypass was negligable. Personally I think thats a sensible approach havent tested it, but look at the pics above, how much gas bypass could get through that tiny hole? Mike ole buddy, please dont put words in my mouth, Liar, never, lunatic maybe been called similar myself. can you send me pics of the failed sensor, pm or email as I have tried to PM you but your box is full, so can you email me ron@tmishop.com I think you may have valid points, but I also think I have answered your points and the design is fine, in fact I may just tear the internals from an old sensor and put it in the rig and try it out for some empiracal testing. __________________ Ron "Life is pain princess, anyone who tells you different, is selling something", The Dread Pirate Wesley. www.tmishop.com Diving bits etc.
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30th April 2007, 16:51	#70 (permalink)
UWSojourner Pacific Northwest Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Location: Portland Oregon Posts: 556	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Gilles) Quote: (Originally Posted by UWSojourner) (Originally Posted by UWSojourner) I think you're confusing disagreement as to the level of risk with denial. The meaning of this escapes me as well . In a prior post, you had implied that those on the other side of this argument were in denial. The statement means you are inappropriately equating disagreement with denial. Quote: (Originally Posted by Gilles) Do you deny that the sensor cartridge could be made better? I'm a little concerned that the Meg toughness is only as good as that of the installed sensors. No, Gilles, everything can be made better. That's not the question. The question is whether there is an incremental benefit of a redesign and whether risk is truly reduced. In my opinion (not yours, not Mike's) this potential-might-happen problem is a very low risk event. No proof, just that no Meg diver has reported an issue with it in all the dives completed to date. It's not what I worry about when I'm on a Meg in the water. And I'll stack my paranoid-credentials against anyone on this forum. Is it possible - yes. Is it probable - no, it is a very low risk event in my opinion. Quote: (Originally Posted by Gilles) I'm a little concerned that the Meg toughness is only as good as that of the installed sensors. Perhaps if ISC made sensors... What toughness is necessary? The sensors just sit there. They block a hole. As long as they don't spontaneously self-destruct mid-dive, they fulfill their job of sitting there. And evidently, at least to date, they do that (sit there) pretty consistently and well. Do I care if someone finds a way to move the sensors to the post-scrubber gas path? No, go for it. Its just that this particular issue, for me, is pretty far down on my list of things I'd want addressed.
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