Cracks PRISM head

silent running · 23rd November 2005, 04:20

Quote: (Originally Posted by Steve)

Hi Andy,
My apologies I forgot to reply.

The Meg’s head is machined and is made from a copolymer acetyl. I’m not getting what you mean by the fact that the Meg is machined and the Prism is a moulded not being a reasonable comparison. Surely the measure of success is how well they do their job not how they are made.

As I see things the materials selected should be fit for purpose and how that is achieved is irrelevant. What is fit for purpose though? I would say the list of criteria a manufacturer should consider would include such things as; robustness, safety, life span, cost effectiveness, manufacturing repeatability and suitability to a marine environment. Is this fair enough?

I’m not particularly interested in another tiresome debate about why one unit is supposedly better than another but let’s not skirt around the issue here, if we use the list above, the issue of robustness is a real concern due to the well known list of Prism heads that have broken in general use. Boat rides break them, units falling over break them, units falling off benches break them, undoing the scrubber bucket breaks them and I’m sure there are more. Given the list of failures and that the same failures are occurring that happened several years ago, I see no evidence of a professional engineering analysis being conducted. The retired unit I mentioned had been repaired many times. Why is the same material still being used if it is known to fail? Have no lessons being learned?

What is my point? Nothing other than there are materials better suited to make a rebreather head than the one chosen for the Prism in my eyes. I’m not saying the Meg is perfect because clearly it isn’t as we have an example in the current threads of a failure. I’m hoping it is a one off, time will tell.

Now, please tell me some facts about where you live

Hi Steve, thanks for the reply. I wasn't trying to get another big debate going. I just wanted to point out that if the 2 were made differently the comparison is difficult as there are different design considerations at work. I wonder if it is possible to make a molded head as strong as one which is machined. I suspect that it is not and I'm guessing that the potting of the computer and locating it in the head and weight/size considerations made molding necessary. As I said in my post on DiveOZ recently, the material currently used in the Prism heads has been changed, at least 2 times that I know of. The material used today is much harder and more resistant to temperature related expansion/contraction issues as well. And the DSV material has also been made harder. So they definitely have learned from experience. I know many other Prism owners and I don't know of any who had any significant breakage on their units. It sounds like the owner of the retired unit was exceptionally hard on it. Any material can be abused to the breaking point. I'm fine with my unit's level of robustness, especially with the cover. It may not be the toughest ECCR on the market, but it is the lightest, simplest and most efficient.

As for facts about where I live, it's the recently tamed and now slightly lame New York City. Thanks to a booming economy, a decrease in crime in the last 10 years and then an increase in the numbers of hapless visitors, the fun parts of NYC now look a lot like Amsterdam. I much prefered the cheaper, more rundown NYC of 20 years ago, but at least the boom has brought more imigrants which means more and better ethnic restaurants.
The borough of Queens is now the most diverse place on earth per sq mile with over 200 different languages spoken and most of the best food in NYC. Gotta take the good with the bad.-Andy

silent running · 23rd November 2005, 04:49

Quote: (Originally Posted by decoweenie)

Hey, hey, hey! Leave the French out of it!

France is a beautiful country with excellent food, wine, skiing in the Alps and beautiful caves.

So except for the people living there, it couldn't be better...

Let's just narrow it down a little bit more to the male people living there...

"No one should ever marry a French man or an American woman"-Somebody-observant-who-was-not-afraid-to-make-unpopular-generalizations. -Andy

Just kidding, I love France... and French too...

Philippe GERIN · 23rd November 2005, 13:29

Quote: (Originally Posted by silent running)

"No one should ever marry a French man or an American woman"-Somebody-observant-who-was-not-afraid-to-make-unpopular-generalizations. -Andy

Good for me! coz I'm married to a French woman.

Best
Philippe

***caveseeker7*** · 23rd November 2005, 16:18

Quote: (Originally Posted by silent running)

The borough of Queens is now the most diverse place on earth per sq mile with over 200 different languages spoken ...

Any of them English?

Steve, the PRISM had to be molded in order to be accepted by NEDU for testing. Machined rebreather are not considered 'production units' by them. It's as simple as that. Machining is also more expensive if you actually go into production and start manufacturing a certain number of units.

SMI has done quite a bit of engineering and analysis on their rigs, including those that damaged. They have, as Andy pointed out, made significant changes to the materials used over the years.

While it sucks that a rig gets damaged when you hammer into solid objects or drop them off the bench, it can happen. Not always, but chances are there will be damage. Much of the damage you're referring to was on rigs without a cowling. That's akin of taking the 5 mph impact absorbing bumpers of your car, driving into a wall at that speed and bitching about the damage.

IIrc, Dr. Mike managed to tackle a wreck hard enough to crack the lid on his 15.5, one of the toughest CCRs out there. And I doubt it's the only MK that has ever been damaged in non-combat service. Had he been diving without the lid there's a fair chance the dome or even center section would have been damaged. I have, by the way, seen an undiveable center section, a bit broken off when it was dropped.

Don't get me wrong, there are things about the PRISM that can, or probably could be improved. The main critique that I have is that SMI still considers the cowling optional and charges extra for it. In my opinion it shouldn't be, and damage to unprotected rigs seems to prove my point quite well. Then, if the owner decides not to use it for whatever reason, the blame is clearly on him or her. Just as it would be on a Cis, MK, APD or any other unit where the guts are exposed to damage.

dive2dive2000 · 23rd November 2005, 17:01

FYI I dive with a PRISM diver who does not use a cowling, he is going on his 5 yr. He is a very aggressive diver. With that said his kit has not been damaged any more than OC divers who dive as much and are just as aggressive. The difference is the cost of repairs

jont · 25th November 2005, 15:17

Quote: (Originally Posted by abowie)

Nice to see that it happens regularly enough that there is an accepted repair technique.

LOL

You don't know the half of it............

jont · 25th November 2005, 15:20

Quote: (Originally Posted by dive2dive2000)

FYI I dive with a PRISM diver who does not use a cowling, he is going on his 5 yr. He is a very aggressive diver. With that said his kit has not been damaged any more than OC divers who dive as much and are just as aggressive. The difference is the cost of repairs

I know the diver you are talking about, I turned him on to the Prism Rebreather and am part of the reason he bought one (I feel guilty about that). He has had an INNUMERABLE amount of problems with his over the past 5 years.

silent running · 26th November 2005, 04:10

Quote: (Originally Posted by jont)

I know the diver you are talking about, I turned him on to the Prism Rebreather and am part of the reason he bought one (I feel guilty about that). He has had an INNUMERABLE amount of problems with his over the past 5 years.

Hello Jon, I'm guessing the reason you recommended the Prism to him is because you liked the design. Do you really feel that guilty? Feeling guilt about something which is out of your control would seem to be uncalled for. His unit must have been one of the very first, pretty common for problems to crop up with a new unit. INNUMERABLE is a lot more than a lot and certainly an exaggeration. I don't know why you insist on making your points this way, it's a distraction from whatever your point is and probably the main reason you catch so much flack. So if you're going to go down this old road again, it's time to get specific.
Was SMI able to resolve his issues?
Does he still own the unit?
-Andy

Drmike · 26th November 2005, 04:29

Quote: (Originally Posted by caveseeker7)

IIrc, Dr. Mike managed to tackle a wreck hard enough to crack the lid on his 15.5, one of the toughest CCRs out there.

No I didnt - http://www.rebreatherworld.com/7410-post26.html

It was my own head that hit the wreck. Dont know if it got cracked WEEEAOOW WEAAOOW WOOP WOOP WOOP ! but I feel OK

***caveseeker7*** · 26th November 2005, 05:43

Quote: (Originally Posted by Drmike)

No I didnt -

Then try again.

What was all that black tape for in the pics on your website?

And don't try to tell me they're camoed sanitary pads.

23rd November 2005, 04:20	#31 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,834	Re: Cracks PRISM head Quote: (Originally Posted by Steve) Hi Andy, My apologies I forgot to reply. The Meg’s head is machined and is made from a copolymer acetyl. I’m not getting what you mean by the fact that the Meg is machined and the Prism is a moulded not being a reasonable comparison. Surely the measure of success is how well they do their job not how they are made. As I see things the materials selected should be fit for purpose and how that is achieved is irrelevant. What is fit for purpose though? I would say the list of criteria a manufacturer should consider would include such things as; robustness, safety, life span, cost effectiveness, manufacturing repeatability and suitability to a marine environment. Is this fair enough? I’m not particularly interested in another tiresome debate about why one unit is supposedly better than another but let’s not skirt around the issue here, if we use the list above, the issue of robustness is a real concern due to the well known list of Prism heads that have broken in general use. Boat rides break them, units falling over break them, units falling off benches break them, undoing the scrubber bucket breaks them and I’m sure there are more. Given the list of failures and that the same failures are occurring that happened several years ago, I see no evidence of a professional engineering analysis being conducted. The retired unit I mentioned had been repaired many times. Why is the same material still being used if it is known to fail? Have no lessons being learned? What is my point? Nothing other than there are materials better suited to make a rebreather head than the one chosen for the Prism in my eyes. I’m not saying the Meg is perfect because clearly it isn’t as we have an example in the current threads of a failure. I’m hoping it is a one off, time will tell. Now, please tell me some facts about where you live Hi Steve, thanks for the reply. I wasn't trying to get another big debate going. I just wanted to point out that if the 2 were made differently the comparison is difficult as there are different design considerations at work. I wonder if it is possible to make a molded head as strong as one which is machined. I suspect that it is not and I'm guessing that the potting of the computer and locating it in the head and weight/size considerations made molding necessary. As I said in my post on DiveOZ recently, the material currently used in the Prism heads has been changed, at least 2 times that I know of. The material used today is much harder and more resistant to temperature related expansion/contraction issues as well. And the DSV material has also been made harder. So they definitely have learned from experience. I know many other Prism owners and I don't know of any who had any significant breakage on their units. It sounds like the owner of the retired unit was exceptionally hard on it. Any material can be abused to the breaking point. I'm fine with my unit's level of robustness, especially with the cover. It may not be the toughest ECCR on the market, but it is the lightest, simplest and most efficient. As for facts about where I live, it's the recently tamed and now slightly lame New York City. Thanks to a booming economy, a decrease in crime in the last 10 years and then an increase in the numbers of hapless visitors, the fun parts of NYC now look a lot like Amsterdam. I much prefered the cheaper, more rundown NYC of 20 years ago, but at least the boom has brought more imigrants which means more and better ethnic restaurants. The borough of Queens is now the most diverse place on earth per sq mile with over 200 different languages spoken and most of the best food in NYC. Gotta take the good with the bad.-Andy Last edited by silent running : 23rd November 2005 at 04:27.
(Online)

23rd November 2005, 04:49	#32 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,834	Re: Cracks PRISM head Quote: (Originally Posted by decoweenie) Hey, hey, hey! Leave the French out of it! France is a beautiful country with excellent food, wine, skiing in the Alps and beautiful caves. So except for the people living there, it couldn't be better... Let's just narrow it down a little bit more to the male people living there... "No one should ever marry a French man or an American woman"-Somebody-observant-who-was-not-afraid-to-make-unpopular-generalizations. -Andy Just kidding, I love France... and French too...
(Online)

23rd November 2005, 13:29	#33 (permalink)
Philippe GERIN ccr apprentice Current Rebreather/s: Megalodon Classic Kiss Other Rebreather/s: Join Date: May 2005 Location: Strasbourg, France Posts: 637	Re: Cracks PRISM head Quote: (Originally Posted by silent running) "No one should ever marry a French man or an American woman"-Somebody-observant-who-was-not-afraid-to-make-unpopular-generalizations. -Andy Good for me! coz I'm married to a French woman. Best Philippe
(Offline)

23rd November 2005, 16:18	#34 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,462	Re: Cracks PRISM head Quote: (Originally Posted by silent running) The borough of Queens is now the most diverse place on earth per sq mile with over 200 different languages spoken ... Any of them English? Steve, the PRISM had to be molded in order to be accepted by NEDU for testing. Machined rebreather are not considered 'production units' by them. It's as simple as that. Machining is also more expensive if you actually go into production and start manufacturing a certain number of units. SMI has done quite a bit of engineering and analysis on their rigs, including those that damaged. They have, as Andy pointed out, made significant changes to the materials used over the years. While it sucks that a rig gets damaged when you hammer into solid objects or drop them off the bench, it can happen. Not always, but chances are there will be damage. Much of the damage you're referring to was on rigs without a cowling. That's akin of taking the 5 mph impact absorbing bumpers of your car, driving into a wall at that speed and bitching about the damage. IIrc, Dr. Mike managed to tackle a wreck hard enough to crack the lid on his 15.5, one of the toughest CCRs out there. And I doubt it's the only MK that has ever been damaged in non-combat service. Had he been diving without the lid there's a fair chance the dome or even center section would have been damaged. I have, by the way, seen an undiveable center section, a bit broken off when it was dropped. Don't get me wrong, there are things about the PRISM that can, or probably could be improved. The main critique that I have is that SMI still considers the cowling optional and charges extra for it. In my opinion it shouldn't be, and damage to unprotected rigs seems to prove my point quite well. Then, if the owner decides not to use it for whatever reason, the blame is clearly on him or her. Just as it would be on a Cis, MK, APD or any other unit where the guts are exposed to damage. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"
(Offline)

23rd November 2005, 17:01	#35 (permalink)
dive2dive2000 PRISM DIVER & LUVIN IT! Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Feb 2005 Location: Long Island, NY Posts: 788	Re: Cracks PRISM head FYI I dive with a PRISM diver who does not use a cowling, he is going on his 5 yr. He is a very aggressive diver. With that said his kit has not been damaged any more than OC divers who dive as much and are just as aggressive. The difference is the cost of repairs __________________ Safe Diving, Martin
(Offline)

25th November 2005, 15:17	#36 (permalink)
jont Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Megalodon Prism Topaz Join Date: Oct 2005 Location: New York, NY USA Posts: 226	Re: Stress Crack in Meg lid Quote: (Originally Posted by abowie) Nice to see that it happens regularly enough that there is an accepted repair technique. LOL You don't know the half of it............
(Offline)

25th November 2005, 15:20	#37 (permalink)
jont Custom Title Allowed! Current Rebreather/s: Inspiration Classic Other Rebreather/s: Megalodon Prism Topaz Join Date: Oct 2005 Location: New York, NY USA Posts: 226	Re: Cracks PRISM head Quote: (Originally Posted by dive2dive2000) FYI I dive with a PRISM diver who does not use a cowling, he is going on his 5 yr. He is a very aggressive diver. With that said his kit has not been damaged any more than OC divers who dive as much and are just as aggressive. The difference is the cost of repairs I know the diver you are talking about, I turned him on to the Prism Rebreather and am part of the reason he bought one (I feel guilty about that). He has had an INNUMERABLE amount of problems with his over the past 5 years.
(Offline)

26th November 2005, 04:10	#38 (permalink)
silent running Mature mouth breather Current Rebreather/s: Prism Topaz Other Rebreather/s: Join Date: Jun 2005 Location: U.S.A. Brooklyn, New York Posts: 1,834	Re: Cracks PRISM head Quote: (Originally Posted by jont) I know the diver you are talking about, I turned him on to the Prism Rebreather and am part of the reason he bought one (I feel guilty about that). He has had an INNUMERABLE amount of problems with his over the past 5 years. Hello Jon, I'm guessing the reason you recommended the Prism to him is because you liked the design. Do you really feel that guilty? Feeling guilt about something which is out of your control would seem to be uncalled for. His unit must have been one of the very first, pretty common for problems to crop up with a new unit. INNUMERABLE is a lot more than a lot and certainly an exaggeration. I don't know why you insist on making your points this way, it's a distraction from whatever your point is and probably the main reason you catch so much flack. So if you're going to go down this old road again, it's time to get specific. Was SMI able to resolve his issues? Does he still own the unit? -Andy
(Online)

26th November 2005, 04:29	#39 (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: 3,328	Re: Cracks PRISM head Quote: (Originally Posted by caveseeker7) IIrc, Dr. Mike managed to tackle a wreck hard enough to crack the lid on his 15.5, one of the toughest CCRs out there. No I didnt - http://www.rebreatherworld.com/7410-post26.html It was my own head that hit the wreck. Dont know if it got cracked WEEEAOOW WEAAOOW WOOP WOOP WOOP ! but I feel OK __________________ 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 : 26th November 2005 at 04:37.
(Offline)

26th November 2005, 05:43	#40 (permalink)
*caveseeker7* Who loves ya, baby Current Rebreather/s: Sport Kiss Other Rebreather/s: Prism Topaz Join Date: Jan 2005 Location: Too far from Neverland Posts: 5,462	Re: Cracks PRISM head Quote: (Originally Posted by Drmike) No I didnt - Then try again. What was all that black tape for in the pics on your website? And don't try to tell me they're camoed sanitary pads. __________________ Cheers Stefan "Political Correctness is a doctrine, fostered by a delusional, illogical minority, and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a turd by the clean end.!"
(Offline)

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