Wow! Meg design - dont know if I like this

jeff h · 3rd May 2007, 03:54

Quote: (Originally Posted by Drmike)

And judging by the dozen green blobs...

Have some more green. I for one enjoy all of your post and really do appreciate you taking the time to point this out.

-Jeff

SINUS · 3rd May 2007, 06:02

This is an eyes opening thread and a critical one also - it shows that it aint wise to have cells placement shared by both side of the loop Exhale and Inhale.

Most RBs design have there cells (whole) placed in one side of the loop be it in the Exhale or Inhale side. Cant imagined if the meg had a partially disloged cell from the main cell casing that could lead co2 bypass / unscrubbed air to the diver at depth.

Unlikely maybe, but one life lost is too much.

Drmike's sound analysis is spot on!

Cheers

Wei Lan

Drmike · 3rd May 2007, 06:05

Quote: (Originally Posted by UWSojourner)

Someone tell me what constitutes a "design problem".

From the design perspective:

I make my living out of engineering design. I get probably over a dozen drawings a day pass over my desk for review. When I see a part of a design I ask myself is that part necessary? what is its advantages what are its disadvantages.

When I look at the idea of having the sensors between the inhale and exhale side I see possible disadvantages (bypass) I see no benefits, I don't see that its necessary. So to me it adds risk (no matter how small) for no reason. if one of my engineers came to me with that design Id ask him "why are the cells there? why not move them to here? that way theres no need to worry about possible bypass (cell body failure , cell internal leaking, o-ring leaking)"

From a whole system perspective; (incl design, teaching, pre-dive checks)

A less than optimal design can still be safe if the whole 'system' caters for it. In this case if the pre-dive checks can highlight a problem with a leaking/damaged cell and if this is being taught then we are good to go - the 'whole system' is safe. - yay!

But from posts on this thread it would seem that users aren't doing a pre-dive check on the sensor block (assembly check yes but not always pre-dive)

So there is a potential design flaw in the 'whole system' design (unnecessary positioning of sensors giving potential risk of bypass) and in the system (divers aren't doing sensor bypass check prior to each dive) [bare in mind the sensors could fall apart between dives]

Quote:

It's easy to say "obviously design flaw"; its harder to determine if what you claim is supportable. With this issue, I have my doubts.

It is easier to say nothing I agree

. As for doubts, at one stage supporters here were absolutely adamant that sensors cant fall apart and yet now you have three people who have seen sensors fall apart under use. Me and Jerome (without obvious reason) and another user through impact shock. So you have to accept that the cells can fall apart. If you accept that fact then you have to also accept that this in the meg design could lead to bypass. If you accept that fact then you have to accept the fact we need to either determine how much of a bypass risk there is, have protocols in place that can check sensor integrity before every dive - or a simple redesign to eliminate the whole issue.

Sure we don't know how much bypass - nobody said we did - and I made that point earlier. If the degree of potential bypass (from a cell falling away from its faceplate) is negligible then great - but that needs to be determined by the mnf - I doubt it would ever be determined unless some busybody fool writes a thread about it and takes some flak

Do you think after seeing the design and after seeing my cells fall apart I should say nothing? perhaps you need to re read my first post here. Surely you would want your life support system to stand up to full public scrutiny? Such scrutiny is good fro the manf. for the users for everyone if its done properly. The manf could come on here and show why the sensor positioning is not an issue, how the potential for bypass is negligible - great - I hope that's right - I have no axe to grind, they may have good reasons to do it that way. Im just opening up for discussion what I saw as a poor design choice and asking the questions. But as I said at the start - It could all be bollocks. But personally when it comes to life support system design Id rather be on the side of caution.

**trob09** · 3rd May 2007, 13:04

Quote: (Originally Posted by Drmike)

Me and Jerome (without obvious reason)

Mike, first, let me add my name to the list who those who are saying "thanks mate". One needs to consider both the potential for failure as well as the probability for failure. I believe - wherever possible - potential failures should be identified and ideally remedied.

Second, I think we all need to recognize there's no perfect rebreather (yet) and we are each carrying a collection of failure points on our backs. Defensiveness of a unit/brand when a potential failure is identified only serves to slow down design improvements and community survivability. That doesn't mean we shouldn't have healthy discussion on what a potential failure point is, only that we shouldn't shift into auto-defense just because our preferred rebreather is on the examination table.

Lastly, the part I snipped out of your last post I do take a bit of exception to. Dunking and soaking cells in a caustic solution _may be_ obvious reason.

Thanks again.

Tim

Outlaw · 3rd May 2007, 13:58

Quote: (Originally Posted by Drmike)

Really dont know why I bother making drawings nobody looks at or describing failures that I have seen then get people effectively calling me a lair. Why do I waste my time an make the effort? I dont dive a meg. I certainly dont do it so someone can efectively call me a liar.

Heres my last post oin this subject.

look at the picture below pull the cell apart the way i illustrated it here and in several previous posts i wasted my time putting up.

Of course if your cells are correctly glued they wont fall apart easily I would have thought that was f_cking obvious

But if like the ones I had they are not properly glued on the FACEPLATE then they can and will

Think what you want - its your funeral. Ill say no more in this thread

Doc,

i would like to say something to you and i really hope that you take it very seriously. first, i want to thank you personally for all you do. especially for the time you share information with others. Then, i want to know that, i for one, seriously appreciates the information you share on this forum. this thread for me, had me thinking very hard about the whole thing. i must say, it never occured in my mind that such a thing might occur.

i went back to my shed and put the head together, and tried to blow through the hole ( inlet way, the one in the middle of the head) and tried to have my hand firmly on the other end, that connects with the scrubber "housing" (i hope you get what i mean, don't know if the terminology is the best) and i was blowing hard, and i could feel that there is a leak from somewhere which made me wonder where does the air escape from? it should be sealed tight right?

anyway, what i want to say is that you should not put yourself off from the fact that some might call you names, or support the opposite from what you say. it's their right, well not to call you a liar offcourse, but what can you do? i guess you have to take into consideration ( and feel great satisfaction) that others, do benefit, and enrich their knowledge from your postings or sharing information on the forum. besides, this is what is all about. i for one, has beneffited a lot from yours and from others' posts. i consider myself someone who has dealt with scuba diving for a long time, but with rebreathers, even though my aim was always that, i must say i am a newcomer. if there are no guys like you, who share thoughts, opinions or knowledge, then what is going to happen? it deppens of what you want really? do you want to be remembered or thought of as the " guy who brought this or that to my attention aiming to alarm me about a situation" or as " the guy who knows or thinks of some dangerous situation and does not alarm fellow people" ?

i don't know if this has affected people from your recent debate/ argument / fight with Cedric has created a negative vibe about you with others, but if you don't mind saying, i feel that only the diving community has to loose. it's a personal issue i know, just since i felt the need to write all this, then i thought i should let you know.

So, i truly HOPE, that you and Cedric, and others of your standards continue to share data for the sake of making the diving community one with less fatalities/casualties and wish for the best for all of you. For, i wish there was an article, every day since i am as busy as hell, but i still find the time to have a look at the new posts and see what else is there to learn more...

Cheers for your time...

Spyros.

PS. no intention to create havoc or new fights, respects to you, respects to Cedric, respects to all of you...

PS 2. if you feel otherwise, then take me to court.

jdicediver · 3rd May 2007, 15:09

Quote: (Originally Posted by Drmike)

If the degree of potential bypass (from a cell falling away from its faceplate) is negligible then great - but that needs to be determined by the mnf - I doubt it would ever be determined unless some busybody fool writes a thread about it and takes some flak

Do you think after seeing the design and after seeing my cells fall apart I should say nothing? But personally when it comes to life support system design Id rather be on the side of caution.

I do agree with DrMike's analysis and his design concerns, and as I have said in other posts here before, there are many others that know more about this subject than I.

I AM NOT one of the "ostriches" and I refuse to bury my head in the sodalime with others, but I do think the root cause of a failure should be examined, not the design of the unit, unless of course it is determined to be part of the cause for concern.

I too do agree that one incident is too much, and it is up to us (the users) to determine where a problem may occur, and either prompt the manufacturer's to change the design strategy, or come up with a custom correction to the problems encountered.

Steve · 3rd May 2007, 15:34

I am sitting here shaking my head in disbelief at people thinking this thread is worthwhile . For this to be an issue it seems one has to;

flood your unit
not replace damaged sensors (I thought everyone knew to do this, it appears not)
not do your pre dive checks as recommended (idiots )
not understand how the meg works, and
have passion fingers.

If you own a Meg and you can't see this then stop diving now and take up stamp collecting. This thread is embarrassing

I may as well start a thread letting people know that their drysuit might leak if they wash it in toluene. Are you all seriously this ignorant? No wonder diving is called a risky pastime

**trob09** · 3rd May 2007, 15:53

Quote: (Originally Posted by Steve)

I am sitting here shaking my head in disbelief at people thinking this thread is worthwhile . For this to be an issue it seems one has to;

flood your unit
not replace damaged sensors (I thought everyone knew to do this, it appears not)
not do your pre dive checks as recommended (idiots )
not understand how the meg works, and
have passion fingers.

If you own a Meg and you can't see this then stop diving now and take up stamp collecting. This thread is embarrassing

I may as well start a thread letting people know that their drysuit might leak if they wash it in toluene. Are you all seriously this ignorant? No wonder diving is called a risky pastime

Again, difference between "possible" failure and "probable" failure should be considered.

To my knowledge, the meg is the only Rebreather that has the cells acting as a barrier between scrubbed and un-scrubbed gas. Is that a good thing? an OK thing, a bad thing? I think that's a worthy question to discuss. Will it change anything? Maybe, maybe not.

If one does not think it to be a worthy discussion topic, one need not participate....

jdicediver · 3rd May 2007, 16:02

Quote: (Originally Posted by trob09)

Again, difference between "possible" failure and "probable" failure should be considered.

To my knowledge, the meg is the only Rebreather that has the cells acting as a barrier between scrubbed and un-scrubbed gas. Is that a good thing? an OK thing, a bad thing? I think that's a worthy question to discuss. Will it change anything? Maybe, maybe not.

If one does not think it to be a worthy discussion topic, one need not participate....

Hear, hear...

...Listen, listen?

Scubascooby · 3rd May 2007, 16:55

I too was surprised by this design of the Meg when I discovered how the cells are fitted, last year (there is a thread on here somewhere).

The constant fluctuation of pressure between front and back of the cell as the diver breathes and rolls from side to side cannot be advantageous. What would stop this from working the cell loose ?

3rd May 2007, 03:54	#121 (permalink)
jeff h RBW Member Current Rebreather/s: Megalodon Other CCR Home Build Other Rebreather/s: Other CCR Home Build Join Date: Feb 2006 Location: Michigan Posts: 107	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Drmike) And judging by the dozen green blobs... Have some more green. I for one enjoy all of your post and really do appreciate you taking the time to point this out. -Jeff
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3rd May 2007, 06:02	#122 (permalink)
SINUS Rebreather Aficionado Current Rebreather/s: Other SCR Other Rebreather/s: Other SCR Join Date: Apr 2005 Location: 137km from equator Posts: 196	Re: Wow! Meg design - dont know if I like this This is an eyes opening thread and a critical one also - it shows that it aint wise to have cells placement shared by both side of the loop Exhale and Inhale. Most RBs design have there cells (whole) placed in one side of the loop be it in the Exhale or Inhale side. Cant imagined if the meg had a partially disloged cell from the main cell casing that could lead co2 bypass / unscrubbed air to the diver at depth. Unlikely maybe, but one life lost is too much. Drmike's sound analysis is spot on! Cheers Wei Lan __________________ "Silence Is Always Beautiful" Last edited by SINUS : 3rd May 2007 at 07:19.
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3rd May 2007, 06:05	#123 (permalink)
Drmike RBW Member 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: 3,379	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by UWSojourner) Someone tell me what constitutes a "design problem". From the design perspective: I make my living out of engineering design. I get probably over a dozen drawings a day pass over my desk for review. When I see a part of a design I ask myself is that part necessary? what is its advantages what are its disadvantages. When I look at the idea of having the sensors between the inhale and exhale side I see possible disadvantages (bypass) I see no benefits, I don't see that its necessary. So to me it adds risk (no matter how small) for no reason. if one of my engineers came to me with that design Id ask him "why are the cells there? why not move them to here? that way theres no need to worry about possible bypass (cell body failure , cell internal leaking, o-ring leaking)" From a whole system perspective; (incl design, teaching, pre-dive checks) A less than optimal design can still be safe if the whole 'system' caters for it. In this case if the pre-dive checks can highlight a problem with a leaking/damaged cell and if this is being taught then we are good to go - the 'whole system' is safe. - yay! But from posts on this thread it would seem that users aren't doing a pre-dive check on the sensor block (assembly check yes but not always pre-dive) So there is a potential design flaw in the 'whole system' design (unnecessary positioning of sensors giving potential risk of bypass) and in the system (divers aren't doing sensor bypass check prior to each dive) [bare in mind the sensors could fall apart between dives] Quote: It's easy to say "obviously design flaw"; its harder to determine if what you claim is supportable. With this issue, I have my doubts. It is easier to say nothing I agree . As for doubts, at one stage supporters here were absolutely adamant that sensors cant fall apart and yet now you have three people who have seen sensors fall apart under use. Me and Jerome (without obvious reason) and another user through impact shock. So you have to accept that the cells can fall apart. If you accept that fact then you have to also accept that this in the meg design could lead to bypass. If you accept that fact then you have to accept the fact we need to either determine how much of a bypass risk there is, have protocols in place that can check sensor integrity before every dive - or a simple redesign to eliminate the whole issue. Sure we don't know how much bypass - nobody said we did - and I made that point earlier. If the degree of potential bypass (from a cell falling away from its faceplate) is negligible then great - but that needs to be determined by the mnf - I doubt it would ever be determined unless some busybody fool writes a thread about it and takes some flak Do you think after seeing the design and after seeing my cells fall apart I should say nothing? perhaps you need to re read my first post here. Surely you would want your life support system to stand up to full public scrutiny? Such scrutiny is good fro the manf. for the users for everyone if its done properly. The manf could come on here and show why the sensor positioning is not an issue, how the potential for bypass is negligible - great - I hope that's right - I have no axe to grind, they may have good reasons to do it that way. Im just opening up for discussion what I saw as a poor design choice and asking the questions. But as I said at the start - It could all be bollocks. But personally when it comes to life support system design Id rather be on the side of caution. __________________ 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
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3rd May 2007, 13:04	#124 (permalink)
trob09 . Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Posts: 701	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Drmike) Me and Jerome (without obvious reason) Mike, first, let me add my name to the list who those who are saying "thanks mate". One needs to consider both the potential for failure as well as the probability for failure. I believe - wherever possible - potential failures should be identified and ideally remedied. Second, I think we all need to recognize there's no perfect rebreather (yet) and we are each carrying a collection of failure points on our backs. Defensiveness of a unit/brand when a potential failure is identified only serves to slow down design improvements and community survivability. That doesn't mean we shouldn't have healthy discussion on what a potential failure point is, only that we shouldn't shift into auto-defense just because our preferred rebreather is on the examination table. Lastly, the part I snipped out of your last post I do take a bit of exception to. Dunking and soaking cells in a caustic solution _may be_ obvious reason. Thanks again. Tim
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3rd May 2007, 13:58	#125 (permalink)
Outlaw In search of Law breaking Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Aug 2006 Location: Cyprus, Nicosia Posts: 735	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Drmike) Really dont know why I bother making drawings nobody looks at or describing failures that I have seen then get people effectively calling me a lair. Why do I waste my time an make the effort? I dont dive a meg. I certainly dont do it so someone can efectively call me a liar. Heres my last post oin this subject. look at the picture below pull the cell apart the way i illustrated it here and in several previous posts i wasted my time putting up. Of course if your cells are correctly glued they wont fall apart easily I would have thought that was f_cking obvious But if like the ones I had they are not properly glued on the FACEPLATE then they can and will Think what you want - its your funeral. Ill say no more in this thread Doc, i would like to say something to you and i really hope that you take it very seriously. first, i want to thank you personally for all you do. especially for the time you share information with others. Then, i want to know that, i for one, seriously appreciates the information you share on this forum. this thread for me, had me thinking very hard about the whole thing. i must say, it never occured in my mind that such a thing might occur. i went back to my shed and put the head together, and tried to blow through the hole ( inlet way, the one in the middle of the head) and tried to have my hand firmly on the other end, that connects with the scrubber "housing" (i hope you get what i mean, don't know if the terminology is the best) and i was blowing hard, and i could feel that there is a leak from somewhere which made me wonder where does the air escape from? it should be sealed tight right? anyway, what i want to say is that you should not put yourself off from the fact that some might call you names, or support the opposite from what you say. it's their right, well not to call you a liar offcourse, but what can you do? i guess you have to take into consideration ( and feel great satisfaction) that others, do benefit, and enrich their knowledge from your postings or sharing information on the forum. besides, this is what is all about. i for one, has beneffited a lot from yours and from others' posts. i consider myself someone who has dealt with scuba diving for a long time, but with rebreathers, even though my aim was always that, i must say i am a newcomer. if there are no guys like you, who share thoughts, opinions or knowledge, then what is going to happen? it deppens of what you want really? do you want to be remembered or thought of as the " guy who brought this or that to my attention aiming to alarm me about a situation" or as " the guy who knows or thinks of some dangerous situation and does not alarm fellow people" ? i don't know if this has affected people from your recent debate/ argument / fight with Cedric has created a negative vibe about you with others, but if you don't mind saying, i feel that only the diving community has to loose. it's a personal issue i know, just since i felt the need to write all this, then i thought i should let you know. So, i truly HOPE, that you and Cedric, and others of your standards continue to share data for the sake of making the diving community one with less fatalities/casualties and wish for the best for all of you. For, i wish there was an article, every day since i am as busy as hell, but i still find the time to have a look at the new posts and see what else is there to learn more... Cheers for your time... Spyros. PS. no intention to create havoc or new fights, respects to you, respects to Cedric, respects to all of you... PS 2. if you feel otherwise, then take me to court. __________________ CMAS - IANTD - TDI Kamikazi Instrustor Trainer DIRRebreather Team Member ---------------------------- "Once an Outlaw, always an Outlaw"
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3rd May 2007, 15:09	#126 (permalink)
jdicediver John Harcus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Calgary, Alberta Posts: 286	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Drmike) If the degree of potential bypass (from a cell falling away from its faceplate) is negligible then great - but that needs to be determined by the mnf - I doubt it would ever be determined unless some busybody fool writes a thread about it and takes some flak Do you think after seeing the design and after seeing my cells fall apart I should say nothing? But personally when it comes to life support system design Id rather be on the side of caution. I do agree with DrMike's analysis and his design concerns, and as I have said in other posts here before, there are many others that know more about this subject than I. I AM NOT one of the "ostriches" and I refuse to bury my head in the sodalime with others, but I do think the root cause of a failure should be examined, not the design of the unit, unless of course it is determined to be part of the cause for concern. I too do agree that one incident is too much, and it is up to us (the users) to determine where a problem may occur, and either prompt the manufacturer's to change the design strategy, or come up with a custom correction to the problems encountered. __________________ Regards; "Some people shouldn't dive...others shouldn't even get wet".
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3rd May 2007, 15:34	#127 (permalink)
Steve Ladies bring a plate Current Rebreather/s: Megalodon Home Build Other Rebreather/s: Not Bought Yet Inspiration Classic Sport Kiss Classic Kiss MK 15.X Home Build Join Date: Feb 2005 Location: Perth - Australia Posts: 1,133	Re: Wow! Meg design - dont know if I like this I am sitting here shaking my head in disbelief at people thinking this thread is worthwhile . For this to be an issue it seems one has to; flood your unit not replace damaged sensors (I thought everyone knew to do this, it appears not) not do your pre dive checks as recommended (idiots ) not understand how the meg works, and have passion fingers. If you own a Meg and you can't see this then stop diving now and take up stamp collecting. This thread is embarrassing I may as well start a thread letting people know that their drysuit might leak if they wash it in toluene. Are you all seriously this ignorant? No wonder diving is called a risky pastime __________________ WARNING: I contain occasional coarse language, extreme sexual references, nudity, and adult themes, which may offend some people - Usually churchy types.
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3rd May 2007, 15:53	#128 (permalink)
trob09 . Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Feb 2005 Posts: 701	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by Steve) I am sitting here shaking my head in disbelief at people thinking this thread is worthwhile . For this to be an issue it seems one has to; flood your unit not replace damaged sensors (I thought everyone knew to do this, it appears not) not do your pre dive checks as recommended (idiots ) not understand how the meg works, and have passion fingers. If you own a Meg and you can't see this then stop diving now and take up stamp collecting. This thread is embarrassing I may as well start a thread letting people know that their drysuit might leak if they wash it in toluene. Are you all seriously this ignorant? No wonder diving is called a risky pastime Again, difference between "possible" failure and "probable" failure should be considered. To my knowledge, the meg is the only Rebreather that has the cells acting as a barrier between scrubbed and un-scrubbed gas. Is that a good thing? an OK thing, a bad thing? I think that's a worthy question to discuss. Will it change anything? Maybe, maybe not. If one does not think it to be a worthy discussion topic, one need not participate....
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3rd May 2007, 16:02	#129 (permalink)
jdicediver John Harcus Current Rebreather/s: Megalodon Other Rebreather/s: Join Date: Jun 2006 Location: Calgary, Alberta Posts: 286	Re: Wow! Meg design - dont know if I like this Quote: (Originally Posted by trob09) Again, difference between "possible" failure and "probable" failure should be considered. To my knowledge, the meg is the only Rebreather that has the cells acting as a barrier between scrubbed and un-scrubbed gas. Is that a good thing? an OK thing, a bad thing? I think that's a worthy question to discuss. Will it change anything? Maybe, maybe not. If one does not think it to be a worthy discussion topic, one need not participate.... Hear, hear... ...Listen, listen? __________________ Regards; "Some people shouldn't dive...others shouldn't even get wet".
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3rd May 2007, 16:55	#130 (permalink)
Scubascooby Better Off Out of the EU Current Rebreather/s: Classic Kiss Other Rebreather/s: Join Date: Nov 2005 Location: Great Britain Posts: 421	Re: Wow! Meg design - dont know if I like this I too was surprised by this design of the Meg when I discovered how the cells are fitted, last year (there is a thread on here somewhere). The constant fluctuation of pressure between front and back of the cell as the diver breathes and rolls from side to side cannot be advantageous. What would stop this from working the cell loose ? __________________ "dove" is NOT the past tense of "dive" Better off OUT of the EU ! www.hugsac.org.uk
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