What do you guys think is the best CCR

[caveseeker7]

Also Leon has done some testing in the UK this winter and rumour has it that the results on the WOB, was far superior to the minimum regulation for the CE and way better than any other rebreather out on the market today.

Great. Get the numbers from Leon and compare them to the ones published years ago for the PRISM.

... the neopren counterlungs and i have noticed that due to the "push" effect from it when it contracts, the WOB is much better than my old cordura lungs.

Only inhalation effort should be better, on exhalation you have to expand whatever space later contracts, correct? Anyway, WOB consists of both inhalation and exhalation effort.

 

[silent running]

Hey Andy, having doved a fwe different rb, not the prism though, i can tell you the Meg has the by far best WOB of any of the units i have tried, which are KISS SP & CL, Inspiration, Cis Lunar, Boris, MK15.5 and now my Meg.
Also Leon has done some testing in the UK this winter and rumour has it that the results on the WOB, was far superior to the minimum regulation for the CE and way better than any other rebreather out on the market today.
Also on my Meg i have purchsed the neopren counterlungs and i have noticed that due to the "push" effect from it when it contracts, the WOB is much better than my old cordura lungs.

just my 2C

/Jonny

Hi Jonny, I don't doubt your experiences with WOB and the afore mentioned CCRs. I wish I would have been able to try all the ones you have. I've tried the CK-highest WOB, Dolphin-better, YBOD, better still. But the Prism was best by leaps. I'd bet that the Meg radial is very good also. It will be good to see the CE WOB test results and compare them with the NEDU WOB criteria tests on the Prism from 2001. It will be interesting, but not much fun as it will likely give me a headache looking at all those numbers and abreviations of weird units of measurement... -Andy

 

[Mverick]

Great. Get the numbers from Leon and compare them to the ones published years ago for the PRISM.


Only inhalation effort should be better, on exhalation you have to expand whatever space later contracts, correct? Anyway, WOB consists of both inhalation and exhalation effort.

I doubt anybody is going to show numbers other then Prism. Nobody has yet. Don't know why. But, if it's like other things. CE numbers don't always tell the whole story. So, you can keep asking for them. But, you won't get them.


Not that it's a big deal.

But, Take a breath. Close you're lips and relax leaving throat open. Do your cheeks get puffy? That's because natural state at rest is without much air in lungs. Inhale takes effort. Exhale goes on it's own.

So reducing the effort to inhale will give you a greater sense of reducing WOB. Is it going to show on a WOB machine? Don't know. Is it going to be realized by the diver. Yes.

Not saying that's how the Neo lungs work. Just, reducing inhale effort is going to be more noticeable then Exhale effort.

Old idea. Pressurize the loop slightly and have a blower circulate air through the loop. Exposing loop air to scrubber more. When you take a breath it's like the Second stage on a Reg. Kind of boosts air into your lungs. When you blow it puts dirty air back into loop to be circulated.

There is already part of this on a unit. But, as usual. It's vaporware. I know of 5 units like it diving already though.

 

[caveseeker7]

The two test regimen I know about, CE and USN, test all kinds of stuff I coudn't care less about. But both require three tests that I consider very important and the results of which I'd like to know: Scrubber durations, setpoint control accuracy and WOB.

Regarding the CL, I was thinking more towards 'exhale into a ballon'. There's a reason they call it blowing up a ballon, it takes effort to stretch the material. And if childhood memories serve me right, that first stretching blow took more effort than the second ... .

Anyway, I think it's reasonable to at least question if the reduction in inhalation effort isn't offset by an increase in exhalation effort. Also consider that CO2 gets vented on exhalation, so having a low effort there is a nice feature on any rebreather.

 

[Mverick]

The two test regimen I know about, CE and USN, test all kinds of stuff I coudn't care less about. But both require three tests that I consider very important and the results of which I'd like to know: Scrubber durations, setpoint control accuracy and WOB.

Regarding the CL, I was thinking more towards 'exhale into a ballon'. There's a reason they call it blowing up a ballon, it takes effort to stretch the material. And if childhood memories serve me right, that first stretching blow took more effort than the second ... .

Anyway, I think it's reasonable to at least question if the reduction in inhalation effort isn't offset by an increase in exhalation effort. Also consider that CO2 gets vented on exhalation, so having a low effort there is a nice feature on any rebreather.

Yes, they test WOB. But, is it a usable test? In, does it test both inhale and exhale and add them? Does it take into account the effort exerted for an inhale to an exhale?

Only way you'll get real tests is an independent study. Trying to figure one from another. Never works.

Think of Dyno machines. Every one reads different. Even from the same manufacturer. So, USN against Meg or YBOD or BORIS. Doesn't mean didly. Unless they run the same machine. Same day. I'll throw a Meg and a IDA71 AND IDA72 in the pot to be tested. Can even get a Radial Meg can, not CIS, for the test. Come up with a Prism and a Ybod and a Boris. Send them to a guy with a machine. If we can find one. And see what happens. Till then. USN and CE tests. Not really a help.

Same still applies. It's harder to suck then it is to blow. LOL... Rather have more resistence on the blowing side then the sucking side. Learned from years of wearing Resperator for 6 out of 8 hours a day. And, your lungs and diaphram get a workout when the cannisters get clogged and they don't have any clean ones. It happened regular.

I'm more then willing to send my machines to someone to test.

USN has some nice dive tables to. I don't follow. Because I ain't 18 in the best shape of my life. What they test and what I follow Isn't usually applicable. WOB tests. I don't trust unless they are same day, same machine.

And, you're not exhaleing into a balloon. It has pressure from the start. And if you do exhale into a balloon. They inhale would be very easy. In fact. Pressurized.

You're not Stretching the Neoprene counter lungs. Otherwise you'd be stretching the Prism lungs. Which, you ain't doing either. They have a little restriction on inflation. But by no means are they being "Stretched like a balloon". LOL

Both Prism and Meg have great WOB. From both parties heard from. Differences I have for which I like have nothing to do with WOB.

Do I need USN tests or CE tests for that. Nope.

 

[Mverick]

The two test regimen I know about, CE and USN, test all kinds of stuff I coudn't care less about. But both require three tests that I consider very important and the results of which I'd like to know: Scrubber durations, setpoint control accuracy and WOB.

Regarding the CL, I was thinking more towards 'exhale into a ballon'. There's a reason they call it blowing up a ballon, it takes effort to stretch the material. And if childhood memories serve me right, that first stretching blow took more effort than the second ... .

Anyway, I think it's reasonable to at least question if the reduction in inhalation effort isn't offset by an increase in exhalation effort. Also consider that CO2 gets vented on exhalation, so having a low effort there is a nice feature on any rebreather.

Oh, in tests at college. YEARS BACK. We did the test of Blowing up balloons. On the Inhale and Exhale side. It was almost impossible to inflate a balloon on the Inhale side. And easy to blow it up. Put it in a sealed jar. Create a vacume in the jar with your mouth sucking on a hose. Inflates the balloon.

 

[padiscubapro]

Hi Jonny, I don't doubt your experiences with WOB and the afore mentioned CCRs. I wish I would have been able to try all the ones you have. I've tried the CK-highest WOB, Dolphin-better, YBOD, better still. But the Prism was best by leaps. I'd bet that the Meg radial is very good also. It will be good to see the CE WOB test results and compare them with the NEDU WOB criteria tests on the Prism from 2001. It will be interesting, but not much fun as it will likely give me a headache looking at all those numbers and abreviations of weird units of measurement... -Andy

I only have some limited experience with a prism, but from what I remember, I think the meg with a axial was slightly better, no hydrostatic issues at all.. My hodgepodge rig using meg neoprene counterlungs and dsv on an Inspiration scrubber seemed better than the meg with cordora lungs so the neoprenelungs on a meg will probably make it even better..

The weakness is probably the Prism's counterlungs.. Since I have used the same lungs (from a UT-240) on my rig (they are more confortable though) and didn;t think the breathed as well as the meg neorprene or even the standard Inspiration counterlungs when the volume was right.. I think the ut-240 type needs a bit more gas in the loop to keep the gas path open (having no t but rather a different input and output connection)


The funny thing is that I know neoprene lungs typically dont do well on breathing machines but everyone who had ever used them feel the opposite.. It probably has to do with the way neoprene lungs form a bubble in water..

But eitherway the all breathe well... each has it quirks to find the best way to dive the rig.. whats optimum on 1 rig isnt on another..

PS.. the Drager breaths way worse than an Inspiration.. It WOB is horrible.. Both Kiss units breathe better than the drager as well, but worse than the prism, meg and inspiration..


On the KISSes you have to optimize your body positioning then they are confortable breathers..

 

[silent running]

Yes, they test WOB. But, is it a usable test? In, does it test both inhale and exhale and add them? Does it take into account the effort exerted for an inhale to an exhale?

Only way you'll get real tests is an independent study. Trying to figure one from another. Both Prism and Meg have great WOB. From both parties heard from. Differences I have for which I like have nothing to do with WOB.

Do I need USN tests or CE tests for that. Nope.

Hi Mverick, the test results are on the SMI site under "news and testing", And yes it appears they test inhale/exhale and combine them. NEDU measured the hydrostatic loads, resistive levels and peak to peak mouth pressures at an RMV of 75 lpm. The tests seem pretty comprehensive and I imagine that the USN has been testing UBAs-dive gear-for a long time, probably longer than anybody else.

As for independance, I don't see why the USN would not be independant on this issue. After all, if their combat swimmers can't perform at their peak during a demanding operation, who would benefit from that?

For me WOB is as big deal as any because it's the one of only 2 factors that we as divers have any control over in the production of CO2, the other being scrubber design. And don't forget, WOB increases with depth, as does stress. So frankly, I want all the help I can get when I find myself in demanding situations... -Andy

 

[silent running]

I only have some limited experience with a prism, but from what I remember, I think the meg with a axial was slightly better, no hydrostatic issues at all.

The funny thing is that I know neoprene lungs typically dont do well on breathing machines but everyone who had ever used them feel the opposite.. It probably has to do with the way neoprene lungs form a bubble in water..

PS.. the Drager breaths way worse than an Inspiration.. It WOB is horrible.. Both Kiss units breathe better than the drager as well, but worse than the prism, meg and inspiration..

On the KISSes you have to optimize your body positioning then they are confortable breathers..

Hi Joe, thanks for the interesting theory about the neoprene CL bubble effect, it makes some sense. Although, as long as one does not allow the cordura CLs to bottom out, the same effect should be achieved, no? Whether it's the inherent bouyancy of the neoprene CLs "bubbling" them out or cordura CLs with the proper loop volume, the airspace would still be there.

But I'm trying to understand how a unit like the Meg axial or Inspo, which both have a gas path that is longer than a similarly designed radial unit, and goes all the way down one's back, could have no hydrostatic issues at all. The longer the path and the farther below the lungs it it goes, it would increase the hydrostatic load, no?

As for the Drager, I think you're right that it breathes worse than the Inspo, as I said too. But I have heard several people tell me that the Inspo does not breathe as well as the MK 15.5, which would make sense if the elbow/pipe return up from the bottom of the scrubber was increasing the hydrostatic base line...

As for the CK, I spent 2 hrs at various depths, loop volumes and body positions and found no comfort. Maybe I missed some trick, but again the CLs run the whole length of the back, down to the butt. While the Drager at least has the CLs higher up on the back, which might explain why I and a few KISS buddies of mine felt the WOB on it was a little better than the CK.

Anyways, testing vs. empirical observation is always an interesting exercise to me. -Andy

 

[padiscubapro]

Hi Joe, thanks for the interesting theory about the neoprene CL bubble effect, it makes some sense. Although, as long as one does not allow the cordura CLs to bottom out, the same effect should be achieved, no? Whether it's the inherent bouyancy of the neoprene CLs "bubbling" them out or cordura CLs with the proper loop volume, the airspace would still be there.

But I'm trying to understand how a unit like the Meg axial or Inspo, which both have a gas path that is longer than a similarly designed radial unit, and goes all the way down one's back, could have no hydrostatic issues at all. The longer the path and the farther below the lungs it it goes, it would increase the hydrostatic load, no?

As for the Drager, I think you're right that it breathes worse than the Inspo, as I said too. But I have heard several people tell me that the Inspo does not breathe as well as the MK 15.5, which would make sense if the elbow/pipe return up from the bottom of the scrubber was increasing the hydrostatic base line...

As for the CK, I spent 2 hrs at various depths, loop volumes and body positions and found no comfort. Maybe I missed some trick, but again the CLs run the whole length of the back, down to the butt. While the Drager at least has the CLs higher up on the back, which might explain why I and a few KISS buddies of mine felt the WOB on it was a little better than the CK.

Anyways, testing vs. empirical observation is always an interesting exercise to me. -Andy

For overall breathing confort on an OTS design the location of the scrubber really has little effect on the overall breathing resistance.. The dead spaces have no effect on the WOB, the path through a scrubber does..

On an OTS design your getting your gas from the inhale counterlung and as long as sufficiend volume is present you arent going to notice any problems taking a breath (remember its at a greater pressure (normally) than your mouth so there should be little effort inhaling).. for what we perceive as easy breathing its the inhale that it important, we really dont notice small changes exhale breathing resistance, but inhale resistance we do feel..

On the KISS units getting the volume of the CL correct and the positioning on your body is critical.. If the unit is too low on your back you will notice problems.. The optimal position on the kiss units is slightly head up..

Believe it or not the BIGGEST contributor to WOB in general is the DSV.. You can have the greatest loop and have a crappy DSV and you will say the breathing stinks.. conversely if you have a reasonable loop but really low resistance through the DSV you will probably think it breaths well assuming you dont have to pull gas through something (not enough volume in "storage"..

If length of gas path was that critical a radial design would actually be a bad thing since that would mean that the furthest points wouldnt be getting the same shot at the gas and the shortest portion of the scrubber would be geting all the work, therby a short duraction, which isnt the case.. The part inside the fixed container is all at the same potential..

The big thing to remember about the meg esespecially is that there is alot of open space for the gas to freely flow to the scrubber opening.. The resistance to flow is going to be much smaller than having to supply the scrubber from a small tube..

The positioning of the CL will effect the WOB, not how far a fixed container like a scrubber goes past the entry point (it would make a difference if the scrubber were compressable).. The positioning of the last/first compressible part is important, not the length of ending position of the Hard part..

With the inspiration the breathing resistance is tied closely to how well a person adjusts where the cl sit on your body.. Most people really dont get anal about getting them in the perfect position by punching extra holes in the fabric that holds the CL..

Designs like the prism and meg allow you to get better positioning on the CLs with very little effort..

Another thing that can effect the WOB on an inspiration is the way the hoses go through the case.. I have seen to many people dive with the hoses partially crushed.. Many of the third party cases allow the full diameter of the hoses to be realized..

I know several people that worked with mk15s and they all say the same thiing the mk15 breaths like a beast compared to the inspiration, and they normally use the insp not the mk15s.. The Mk15s are used when alot of scrubber is needed..