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Thread: Dolphin O2 Sensor Positioning

  1. #1
    RBW Member commachiogroup is an unknown quantity at this point commachiogroup's Avatar
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    Dolphin O2 Sensor Positioning

    Hi,

    I completely new to the homebuild area so looking forward to some superb advice

    So, I'm purchasing a Dolphin SCR to get things started and to get me back into Rebreather's. The project I want to undertake is a CCR conversion at a later stage (once I'm fully happy with the SCR route). This will help give me a greater grounding on the whole mechanics of the system etc.

    In the interim however, I'm looking into putting an 02 sensor in as part of the SCR that can be used going forward as part of the CCR plus the location of the 02 injection.

    Research on this site so far seems to suggest that one of the best places to insert one of the 02 sensors is in the inhale bag after the scrubber whilst the 02 injection goes into the exhale bag.

    Is this correct? Any thoughts and suggestions?

    regards

  2. #2
    An independent diver. bletso is just really nice bletso is just really nice bletso is just really nice bletso is just really nice bletso is just really nice bletso is just really nice bletso is just really nice bletso is just really nice bletso is just really nice bletso's Avatar
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    Re: Dolphin O2 Sensor Positioning

    I placed my O2 injection on the lid of the scrubber. http://www.airheadsscuba.com/bletsop.html

    A second sensor was place next to the first one. It is important to put the sensor in a position facing down whilst in normal dive trim.

    Dale

  3. #3
    Brent - Narked at 90
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    Re: Dolphin O2 Sensor Positioning

    Quote Originally Posted by commachiogroup  View Original Post
    The project I want to undertake is a CCR conversion at a later stage (once I'm fully happy with the SCR route). This will help give me a greater grounding on the whole mechanics of the system etc.
    I wouldnt waste your time and money. Buy a purpose built CCR when your ready.
    Will cost less, be easier to maintain, weigh less and will give you no less insight.
    I went the way you are proposing in the early days, loved every minute of it. But that seems so long ago now and many things have changed, like the availability of cheap second hand units and a wealth of knowledge that just was not so accessable before.
    Have fun with your Dolphin, tinker away but do consider letting her go when the time comes and getting something you will enjoy even more.
    Copying skips understanding. Understanding is how you grow. You have to understand why something works or why something is how it is. When you copy it, you miss that. WWW.NARKEDAT90.COM
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  4. #4
    Darlene Starr - DIY Diva Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen's Avatar
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    Re: Dolphin O2 Sensor Positioning

    Quote Originally Posted by divetheworld  View Original Post
    I wouldnt waste your time and money. Buy a purpose built CCR when your ready.
    Will cost less, be easier to maintain, weigh less and will give you no less insight.
    I went the way you are proposing in the early days, loved every minute of it. But that seems so long ago now and many things have changed, like the availability of cheap second hand units and a wealth of knowledge that just was not so accessable before.
    Have fun with your Dolphin, tinker away but do consider letting her go when the time comes and getting something you will enjoy even more.

    This is really pretty good advice.

    Things have changed a lot in just the last few years as new units have come to market, and reasonably priced pre-owned units are in relative abundance thanks also in part to the worlds economic climate.

    The one thing that throws all that good sense and reason right out the window, of course, is if one is a certifiably addicted DIYer. The DIyer just can't accept the option of not building or modding a unit themselves, even knowing that they'll go longer without having use of the unit, and that it will *not* end up saving them money in the long run anyway.

    If you have a history of being a serious DIYer, Dolphins make great projects.

    If you don't, ... they don't.

    What you learn from an SCR Dolphin doesn't help much, really if at all, after conversion. It's really a different animal, from bouyancy to operation.

    I believe it could be well argued that going from a stock Dolphin (being dived within Drager's guidlines) where the chances of your PO2 getting out of the safe zone are quite small, could easily lead to complacency and therefor minimal monitoring of the PO2 displays, which is about the worst possible mistake you can make diving mCCR.

    As far as PPO2 monitoring, Tecme is your best friend with cell holder houses for three R22D cells in the inhale hose elbow and a variety of display devices from basic Mark Munroe style displays to super deluxe options like Shearwater or rEVOdream.

    My thinking is that the only reason to buy a Dolphin is to convert it ... straight away ... and not piddle about thinking about it for down the road. If you haven't done all your homework and have the conversion plan and the technical ability in place, .... pass on the Dolphin and keep saving for something ready to go.


    Darlene
    Last edited by Scuba_Vixen; 27th August 2009 at 01:46.

  5. #5
    RBW Member Ivan Calcoen is a jewel in the rough Ivan Calcoen is a jewel in the rough Ivan Calcoen is a jewel in the rough Ivan Calcoen is a jewel in the rough Ivan Calcoen is a jewel in the rough Ivan Calcoen is a jewel in the rough Ivan Calcoen is a jewel in the rough Ivan Calcoen's Avatar
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    Re: Dolphin O2 Sensor Positioning

    Well said Darlene, I would go exactly the same path... bought my SCR Dolphin 5 or 6 years ago for 2000 euro incl training....
    At that time, that was big money for me and nowhere near I could buy any other diveable, second hand, RB for that price at that time.
    And the path SCR, (m)CCR ... I would do it again if I had to start over.. the mod to mCCR was DIY (with a lot of info gained here at RBW and Dave Bletso et all..) and I really, really enjoyed that.
    However, I understand that Comachiogroup already bought his SCR Dolphin and asked for the best position for the O2 sensorS , w!ell its at the inhale side as Darlene mentioned. Best is indeed using a sensor holder from TECME, Martin is very helpfull.
    In order not to waste any money, dont buy a single sensor holder, for now, because you WILL convert to CCR and than definately need a 3 sensor holder.
    If u are still in the progress of bying this SCR Dolphin, maybe look around, there are indeed more second hand units available and even a brand new unit with lots of safety features avilable for just over 2000 euro...
    Good luck and keep reading/shooting questions

    safe diving

    Ivan

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    Brent - Narked at 90
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    Re: Dolphin O2 Sensor Positioning

    Wot she said. All of it!!

    ;)
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    RBW Member commachiogroup is an unknown quantity at this point commachiogroup's Avatar
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    Re: Dolphin O2 Sensor Positioning

    Okay......Currently I do not have a CCR rebreather that is 'useful' to any real depth. I have a LAR-VII that can be used to 24m in MOD-B mode (Nitrox). Its a great piece of kit, I love it but not much good recreational when my buddy wants to go a little deeper. All my military training was done 'above' 20m (ish) - we had the odd 'bouce' with very high PP02 but thats beyond scope here

    So, enter the world of the Drager Dolphin (yep.....I love Dragers). Anyway, my current thought processes are to use an SCR to recreational depths. At some stage in the future, however, I WILL want to go down the route of CCR to recreational depths. I have NO need or want to go anywhere else.

    So, from what I can gather from the comment thus far, its probably best for me to continue of the SCR Dolphin path and when I wish to go CCR, simply purchase another unit? In the interim, I'll add a PP02 sensor to the inhale bag just for added safety.

    Still love to hear eveyones thoughts......I get the impression ath a CCR conversion isn't necessarily a 'good' process to go through?

    regards

  8. #8
    Darlene Starr - DIY Diva Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen has a brilliant future Scuba_Vixen's Avatar
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    Re: Dolphin O2 Sensor Positioning

    Actually, I wouldn't continue the SCR path at all. ... When you're ready, just go straight to CCR.

    I guess the real question that begs to be asked at this point, is if all you are interested in is recreational depths with your buddy, what do you even need a rebreather for..... It is not the right tool for the job. Seems way more practical to stay on open circuit while you save for a ready to dive CCR in the future. ... But if your buddy isn't on one too, then you'll be looking for new buddies, or wasting a lot of capability.

    An SCR Dolphin just has so few tangible advantages over OC, (actually, I can't think of any) I don't see the wisdom of spending money on it and you're apparently not a DIY addict, so there's no "labor of love" factor involved.

    It's just my opinion, but I think that the only good process a Dolphin can go thru is conversion.



    Food for thought,


    Darlene


    As an afterthought, I was assuming that your buddy is OC, since that's how it came accross to me.
    If he's on a Dolphin now, I could see reason to going that route.
    Last edited by Scuba_Vixen; 27th August 2009 at 18:17.

  9. #9
    RBW Member commachiogroup is an unknown quantity at this point commachiogroup's Avatar
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    Re: Dolphin O2 Sensor Positioning

    Another interesting point after re-reading some of the messages.

    Many people are under the impression that the Drager Dolphin SCR is a very reliable and 'safe' unit to use as a rebreather - hence its popularity. However, I feel from the previous comments, that it doesn't have that many real advantages. Personally I thinks that is an understatement.

    Surely, putting aside safety which is always or paramount importance, part of the attraction of either an SCR or CCR is increased bottom time, light weight of the unit compares to something of similar bottom time (large twinset) and warm moist breathing air (putting aside other huge benefits of CCR).

    We all realise that CCR is a superior beast......but for those breaching out from OC who wish to learn the fundemantals without the massive complexities and risk of CCR surely SCR is still a valid and safer option?

    Sort of going away from the original thread really.......but still, especially as a teaching instructor, SCR is a valid option in my opinion for new students?

  10. #10
    RBW Member commachiogroup is an unknown quantity at this point commachiogroup's Avatar
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    Re: Dolphin O2 Sensor Positioning

    Oh......and thanks Ivan for getting back to me with regards to Sensor Positioning.

    I'm thinking now about simply using a single sensor just for safety sakes and then, after a period, selling the SCR and purchasing a fully setup CCR rather than the homebuild option.

    I originally thought it was a viable, valuable and sound 'learning experience' but from the comments recieved looks like its not the case.

    Many thanks everyone for your comments
    Safe diving.....

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