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Thread: A few questions on JJ and rEvo units

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    RBW Member Gl1tchie is an unknown quantity at this point Gl1tchie's Avatar
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    A few questions on JJ and rEvo units

    Hi Rebreather World.

    I have done a fair bit of searching and reading lately about 2 rebreathers that, at the moment, I can not decide between.

    I have read tonnes of forum posts that start out something like:
    "What's better, JJ or rEvo?"

    Usually a few people get on and offer some great pluses and minuses to both units.
    Then someone tells of some mod that they did and then it becomes a flame war on mods and why they are a good idea or a bad idea..

    And then someone will bring up other units that the OP was never asking about.

    I would like to avoid the above if possible please.

    I have a few questions that I would like to ask and have answered directly and specifically. Preferably by people that have dived either or both units.

    For a bit of background:
    I have been diving recreationally since 2000 and recently progressed through TDI Advanced Nitrox and Deco Procedures on twin tanks. I really enjoy deep diving on reefs, simple wreck dives (no major penetration through tight squeezes yet but maybe down the track). I have not ventured in to cave diving and to be honest as yet do not plan to. I do most of my diving over seas on holiday.
    I currently live in Perth, Western Australia. There is a dive shop in Perth that will very shortly be stocking, supporting, and training JJ Rebreathers.
    3.5 hour flight from Marc Crane (rEvo) or Will Goodman (JJ).

    A fair few people say it is a good idea to make a list of pros and cons. I have tried to do so. Below is my list. Please keep in mind, when making this list, I ruled out things that were good or bad on both units. (there is no point in having something like "good WOB" on both sides of the list..) I have also included questions that I would like answering if anyone could provide feedback that would be greatly appreciated.

    Things I like about JJ:

    Perth local buy/training/support (Pretty big plus?)
    I like the manual add buttons just resting over the shoulder - no big block
    Will Goodman

    Things I'm not sure about the JJ:
    Only 3 PO2 cells - No stand alone redundant PO2 monitor

    Questions about JJ:
    Can I buy the N.E.R.D INSTEAD of the wrist mount shearwater? (Already have Petrel (non fischer) for back up)
    What happens if on the off chance 2 cells died at once and voting system chooses the dead ones as the good ones?



    Things I like about the rEvo:

    Can choose N.E.R.D instead of wrist mounted computer (Already have Petrel (non fischer) for back up)
    Up to 5 PO2 cells for complete redundant monitoring
    Dual scrubber system
    RMS - Scrubber monitoring
    Marc Crane

    Things I'm not sure about on the rEvo:
    No Perth local buy/training/support - Although there is non official supporters in Perth

    Questions about the rEvo
    Is the extra cells REALLY that good? (A dead cell on any unit would be abort dive time?)
    If I live in Perth, where do I buy one from?

    Thanks in advance Rebreather World,
    Dan

  2. #2
    RBW Member kaj crucq is an unknown quantity at this point kaj crucq's Avatar
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    Re: A few questions on JJ and rEvo units

    Quote Originally Posted by Gl1tchie  View Original Post
    Hi Rebreather World.

    I have done a fair bit of searching and reading lately about 2 rebreathers that, at the moment, I can not decide between.

    I have read tonnes of forum posts that start out something like:
    "What's better, JJ or rEvo?"

    Usually a few people get on and offer some great pluses and minuses to both units.
    Then someone tells of some mod that they did and then it becomes a flame war on mods and why they are a good idea or a bad idea..

    And then someone will bring up other units that the OP was never asking about.

    I would like to avoid the above if possible please.

    I have a few questions that I would like to ask and have answered directly and specifically. Preferably by people that have dived either or both units.

    For a bit of background:
    I have been diving recreationally since 2000 and recently progressed through TDI Advanced Nitrox and Deco Procedures on twin tanks. I really enjoy deep diving on reefs, simple wreck dives (no major penetration through tight squeezes yet but maybe down the track). I have not ventured in to cave diving and to be honest as yet do not plan to. I do most of my diving over seas on holiday.
    I currently live in Perth, Western Australia. There is a dive shop in Perth that will very shortly be stocking, supporting, and training JJ Rebreathers.
    3.5 hour flight from Marc Crane (rEvo) or Will Goodman (JJ).

    A fair few people say it is a good idea to make a list of pros and cons. I have tried to do so. Below is my list. Please keep in mind, when making this list, I ruled out things that were good or bad on both units. (there is no point in having something like "good WOB" on both sides of the list..) I have also included questions that I would like answering if anyone could provide feedback that would be greatly appreciated.

    Things I like about JJ:

    Perth local buy/training/support (Pretty big plus?)
    I like the manual add buttons just resting over the shoulder - no big block
    Will Goodman

    Things I'm not sure about the JJ:
    Only 3 PO2 cells - No stand alone redundant PO2 monitor

    Questions about JJ:
    Can I buy the N.E.R.D INSTEAD of the wrist mount shearwater? (Already have Petrel (non fischer) for back up)
    What happens if on the off chance 2 cells died at once and voting system chooses the dead ones as the good ones?



    Things I like about the rEvo:

    Can choose N.E.R.D instead of wrist mounted computer (Already have Petrel (non fischer) for back up)
    Up to 5 PO2 cells for complete redundant monitoring
    Dual scrubber system
    RMS - Scrubber monitoring
    Marc Crane

    Things I'm not sure about on the rEvo:
    No Perth local buy/training/support - Although there is non official supporters in Perth

    Questions about the rEvo
    Is the extra cells REALLY that good? (A dead cell on any unit would be abort dive time?)
    If I live in Perth, where do I buy one from?

    Thanks in advance Rebreather World,
    Dan

    Hey Dan,
    I'm doing a rebreather course on the JJ at the moment, so I don't have that much experience yet. But I had to choose between REVO and JJ as well.


    first off all, both rebreathers breath perfect, no doubt about that.


    It is for sure a big plus if you have easy acces in your area (perth) to after sales service for spare parts and maintenance service, not in the last place for face to face information. so that is something you really have to keep in mind.


    3 PO2 cells are enough I think. a lot of rebreathers have only three. in the unlikely event of two dead cells it is still possible to determine the good cell. this you will learn in the course. but during pre dive checks you'll have found out that something is wrong, and diving is not possible.
    remember that 5 O2 cells means that you also have to buy 5 new ones every year. $$$


    it is possible to buy a nerd instead of the standard HUD. but the hard wired wrist controller will be delivered standard. I'm still in doubt what I will do with my HUD. I prefer 2 hard wired wrist computers. 1 controller (standard from JJ) and a stand alone computer for real time PO2 monitoring and deco calculation.


    If you chose for the REVO i would advice to buy the titanium RMS edition. It cost a few dollars more, but then you have the advantage of the dual scrubber.


    the things I didn't like about the REVO are the plastic scrubber covers and the amount of electronica wires in the counterlung itselve. AT the JJ this is more "organized.
    personally i have my thoughts about the dubble "half" scrubber. totally it's the same amount of sorb as in the JJ, but with the REVO it last twice the time(?) why? does the RMS system extend the duration of the scrubber? No, it only reads out the duration of the scrubber.


    as you travel alot the titanium RMS version is a big +. it cut's off a few lbs from your travelweight. I travel alot as well in Europe, but that's always by car, so the weight is not a problem for me.


    continue your research and take your time to try both units and get explained how and why it's designed as it is. and have fun with it.


    greetz Kaj
    Netherlands

  3. #3
    RBW Member colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky's Avatar
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    Re: A few questions on JJ and rEvo units

    Quote Originally Posted by Gl1tchie  View Original Post
    I like the manual add buttons just resting over the shoulder - no big block
    The "big block" is hardly noticeable & most of the time during normal diving you will not use it. I like having everything on one block & of course you can also plumb an off board gas into it if you need to

    Quote Originally Posted by Gl1tchie  View Original Post
    What happens if on the off chance 2 cells died at once and voting system chooses the dead ones as the good ones?
    Before I had a rEvo I dived an AP unit with only 3 cells. If 2 out of 3 go down at the same time then your having a really bad day & should probably stay in bed Not something that happens often & to be fair no difference between the JJ & rEvo , either unit will only read 3 cells for the controller. On the rEvo the extra 2 cells are a totally separate system that has no control over anything & is purely a passive display


    Quote Originally Posted by Gl1tchie  View Original Post
    Can choose N.E.R.D instead of wrist mounted computer (Already have Petrel (non fischer) for back up)
    Up to 5 PO2 cells for complete redundant monitoring
    Yes you can choose N.E.R.D. I have NERD on my new unit but am undecided if I like it. You also have 2 huds ( one from each rEvo Dream ) on your DSV then add the NERD as well I find a lot of clutter plus I am still struggling to get the mount just right to be able to see it . Also in shallow depths with bright sun coming through the water it can make it very very hard to see.
    Yes 5 cells but as mentioned above only 3 for control

    Local support can be a blessing but I live in the UK & my nearest place is actually the factory in Belgium! I have dived a revo II since 2009 until this year when I changed to a Micro FT Titanium . In all that time I think I have lost 2 dives & one of those was user error.

  4. #4
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    Re: A few questions on JJ and rEvo units

    Quote Originally Posted by kaj crucq  View Original Post
    3 PO2 cells are enough I think. a lot of rebreathers have only three. in the unlikely event of two dead cells it is still possible to determine the good cell. this you will learn in the course. but during pre dive checks you'll have found out that something is wrong, and diving is not possible.
    remember that 5 O2 cells means that you also have to buy 5 new ones every year. $$$
    If 2 cells fail would you still continue the dive? Or would you turn it? With 5 cells you would still have 3 good ones.

    I think rEvo still recommend a new cell every 6 months. Not 5 every year. Some choose to get a new cell more often. Every 3 months still only equates to 3 a year.


    If you chose for the REVO i would advice to buy the titanium RMS edition. It cost a few dollars more, but then you have the advantage of the dual scrubber.
    All rEvos have dual scrubbers. even the MK1 mCCRs.

    the things I didn't like about the REVO are the plastic scrubber covers and the amount of electronica wires in the counterlung itselve. AT the JJ this is more "organized.
    personally i have my thoughts about the dubble "half" scrubber. totally it's the same amount of sorb as in the JJ, but with the REVO it last twice the time(?) why? does the RMS system extend the duration of the scrubber? No, it only reads out the duration of the scrubber.

    You are correct, the RMS does not extend your dive time. But the dual scrubber does AND the RMS lets you know the state of the scrubber. So in reality the whole system does give you longer scrubber times.

    I have had a rEvo for 5 years. When my buddy and I got ours they were the 1st and 2nd in NZ. Now there are 3.
    The limited numbers has never been an issue. Any parts needed were only ever a few days away. Most of the issues I have had with it though have been computer issues. Broken cables, peizos depth sensors.
    The only real issue has been lack of instructors.
    mod 1 required a trip to Sydney. Was a real shit instructor with 4 x 30 mnute dives to pass the course.
    Mod2 and 3 was Bali with Marc Crane. 18 hours in water. Great instructor, course and location. Dont look at having to travel there as a con. Its a pro!

    Either of the 2 units will make you a happy diver.

  5. #5
    RBW Member colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky is a name known to all colinicky's Avatar
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    Re: A few questions on JJ and rEvo units

    Quote Originally Posted by kaj crucq  View Original Post
    It is for sure a big plus if you have easy acces in your area (perth) to after sales service for spare parts and maintenance service, not in the last place for face to face information. so that is something you really have to keep in mind.
    Agreed

    Quote Originally Posted by kaj crucq  View Original Post
    3 PO2 cells are enough I think. a lot of rebreathers have only three. in the unlikely event of two dead cells it is still possible to determine the good cell. this you will learn in the course. but during pre dive checks you'll have found out that something is wrong, and diving is not possible.
    Although I would agree 3 cells are enough cells can, do & have gone wrong during a dive. there fore your statement about Pre Dive checks is not strictly true

    Quote Originally Posted by kaj crucq  View Original Post
    remember that 5 O2 cells means that you also have to buy 5 new ones every year. $$$
    Not true. Copied from the rEvo website :-

    *"The*system*rEvo*already*advises*for*some*time,*‘ro tating*sensors’:*the*system*works* as*follows:*as*soon*as*the*youngest*of*all*sensors *in*your*system*(3,*4*or*5)*reaches*the*age*of*6*m onths,*you*replace*the*weakest*(the*one*that*react s*the*slowest*on*PPO2*changes,*or**the*one*that*se ems*to*become*closest*to*current*limiting,*during* the*test*at*6/7meters),*or*if*you*can’t find a ‘weakest’, then the oldest in your system . If of course a*sensor*fails*before*the*youngest gets 6 months old, you replace it, and the latter one becomes the*youngest*at*that*moment."*


    Quote Originally Posted by kaj crucq  View Original Post
    the things I didn't like about the REVO are the plastic scrubber covers and the amount of electronica wires in the counterlung itselve. AT the JJ this is more "organized.
    personally i have my thoughts about the dubble "half" scrubber. totally it's the same amount of sorb as in the JJ, but with the REVO it last twice the time(?) why? does the RMS system extend the duration of the scrubber? No, it only reads out the duration of the scrubber.
    Just for clarity there is only one scrubber cover on a rEvo but I think you were meaning in general ?
    The problem with any scrubber is that for CE testing the conditions are extreme. The normal person would never produce the rates of Co2 CE states but the "Extreme " is what is specified & used to get the duration. Read about the rEvo & the figures quoted do not vary that much BUT the RMS system will read what the scrubber is actually doing & give you a read out accordingly per scrubber canister.
    Now my personal opinion is that the RMS I have is a Scrubber Monitor & NOT a Scrubber EXTENDER

    Quote Originally Posted by kaj crucq  View Original Post
    as you travel alot the titanium RMS version is a big +. it cut's off a few lbs from your travelweight.
    revo micro FT comes as Titanium standard & is the lightest they make

    Most important is to actually try the units for a couple of dives & question everything

    Remember the only stupid question is the one you didn't ask !

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    Re: A few questions on JJ and rEvo units

    I have owned both units. There is a lot to like about the rEvo, but it did not work out for me physically. I will just say that you must be limber to dive a rEvo. The limitation on tank placement resulted in me not being able to reliably reach my cylinder valves. My shoulder mobility is limited after several operations. If you can not reach the middle of your back with each arm, you could have problems with a rEvo. I had a standard size rEvo and could just barely touch my O2 valve if I had a bailout cylinder on my right. I wouldn't have even come close with a mini or micro. I never noticed during try dives or my crossover course because I never had a bailout on that side.

    Just something to consider. Tank placement on the JJ is more "forgiving" for us ancient, decrepit folks. And I like my JJ a lot. But there are some beautiful things about the rEvo that I miss.


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  7. #7
    RBW Member dunny is an unknown quantity at this point dunny's Avatar
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    Re: A few questions on JJ and rEvo units

    Quote Originally Posted by Gl1tchie  View Original Post
    Hi Rebreather World.
    Questions about JJ:
    Can I buy the N.E.R.D INSTEAD of the wrist mount shearwater? (Already have Petrel (non fischer) for back up)
    What happens if on the off chance 2 cells died at once and voting system chooses the dead ones as the good ones?
    No you cannot buy a NERD instead of the controller as it is hardwired. The NERD would be a replacement to the HUD and a monitor only, not a controller. If two cells die at the same time and in the same way they they could get chosen over the one remaining good cell which could prove fatal. Personally this scares me which is why I bought a cell checker and I check for linearity during the dive and at 6m on deco.
    Quote Originally Posted by Gl1tchie  View Original Post
    Questions about the rEvo
    Is the extra cells REALLY that good? (A dead cell on any unit would be abort dive time?)
    If I live in Perth, where do I buy one from?
    I can't comment I've never owned a rEvo, I also can't pick fault with the unit the rMS system is a good idea but I just didn't like it as much as the JJ.

    Hope that helps
    Phil

  8. #8
    RBW Member jamesjooste is an unknown quantity at this point jamesjooste's Avatar
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    Re: A few questions on JJ and rEvo units

    I am from Perth too. I recently did my IANTD rec trimix rEvo user course with Marc Crane in Talumben.

    I love the unit. It has a shortcoming in flood tolerance; but it is robust, i like the enclosed counterlungs (I bash into rocks and wrecks alot diving the way I like to) and the almost constant WOB in any position including face up and inverted.
    I love the Nerd. Know I always know my ppO2 - ITS IN MY FACE!

    I do not have the lowdown on how quickly training on the JJ will be available in Perth. Even if sales are available, the JJ is also a compelling choice. I would consider a cross-over course - you can never have enough breathers, as long as they are JJ or rEvo.

    With respect to the cell failure/abort dive question - it has proven useful to me in the past to know that I have working cells that I can validate and compare, and ignore the wet/failed ones. It may take some time to "abort" a 45+m dive with a deco obligation. Give me 5 cells any day.

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    Re: A few questions on JJ and rEvo units

    Additionally - RMS rocks. It will ensure you have ACTUALLY PLACED the TWO SERIAL scrubbers into the unit, and reduces sorb wastage significantly by giving you a running estimate of the time to next cycle (discarding the sorb in the top scrubber - 1.3kg). I have found that the time that the RMS estimates correlates well with my workload on the unit (yes, i still actually swim/fin - no money left for a scooter!).

  10. #10
    RBW Member Gl1tchie is an unknown quantity at this point Gl1tchie's Avatar
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    Re: A few questions on JJ and rEvo units

    Hi all,

    I really appreciate this feedback. I will reply properly and probably ask a few more questions once back on my pc.

    Thanks for the feedback so far!
    Dan

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