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I'll do what I can to address the questions relating to my posts:
On Mon, 4 Jul 1994, A.APPLEYARD wrote:
> On Fri 1 Jul 1994 10:22:45 +22305714 (HST) Richard Pyle
> <deepreef@bi*.bi*.ha*.or*> replied:-
> > Geez - you don't want much, do you :-) My impression is that a unit
> meeting all of your criteria will not exist anytime soon....
>
> Why not? Why so expensive and difficult? Oxygen rebreathers for industry and
> firemen (and later naval frogmen) were inexpensive and mass produced for ages
> before sport diving was much heard of, e.g. the (UK) Siebe Gorman Salvus (neck
> type) (incredibly light and handy, about 40 mins duration), Proto, UBA, SCBA,
> etc etc. Technology seems to have forgotten how to make things simple. To
> make this into an automatic mixture rebreather seems to me to need:-
> * Diluent (air usually) cylinder. This would not add much more to the cost
> than it costs to give the set its oxygen cylinder.
> * Electrically-actuated oxygen and diluent values. Various writers to
> Techdiver (e.g. JOHNCREA@de*.co* on Wed 29 Jun 1994 06:59:03 -0400 (EDT))
> have pointed out these don't need much electricity to run and so only need a
> small battery of the common type.
> * Partial pressure of oxygen (= ppO2) sensor.
> * Depth sensor.
> * Sensor to tell if he is sucking at an empty breathing bag.
> * Some simple electronics (not necessarily a PC-type CPU) to keep the ppO2
> right and to let more gas in if he sucks at an empty bag.
> === Useful would be:-
> * ppO2 readout external connection for a suitable decompression meter to
> read from.
> * Separate aqualung-type pillar valve fed from the air (diluent) cylinder,
> so he can fit an aqualung regulator to it as a baleout if he wants to.
> PLEASE which of those items is so massively expensive or impossible!?!?
The problem isn't in the parts & electronics to build a basic rebreather
so much as it's in ensuring they are RELIABLE. Electronics & sea water
don't like each other very much. In a closed-circuit mixed-gas
rebreather, your life depends much more on those electronics than it does
on a dive computer on open-circuit. When a regulator malfunctions, it's
pretty self-evident. However, when an O2 sensor or solenoid
valve malfunctions, and your breathing mix gets too much or too little
oxygen, you don't know it until you convulse or black out. Breathing seems
normal right up until it's too late. So now you're talking a whole series
of redundant (often triplely-redundant) coponents, and pretty soon you're
talking about a very complex system with two or three sets of everying,
all working with each other. The less you want to rely on for manual
control (i.e. the more you want the thing to do automatically for you),
the more complicated & expensive it will be. These are the realities of
trade-offs, and this doesn't even include things like R&D investment &
HUGE libility exposure on the part of the manufacturer.
> Is there any need to add to the cost by having the set in a box? People have
> used rebreathers with the bag naked from the beginning. With modern very tough
> materials like Kevlar there need not be much risk of the bag getting cut open.
Having the set in a box doesn't add significantly to the cost. The box is
usually just a fiberglas shell to protect the components from being bashed
on the rocks/wreck, etc.
> Richard Pyle described the Cis-Lunar set:
> > ... available for purchase later this year.... capabilities v. cost. 25
> will be built this year, all ...already ... sold. But if it all goes well,
> they'll offer more next year. They have just about all of the criteria you ask
> for, plus way more than you probably want, and cost around $12,000-$15,000.
>
> That is $$$$!! What are the "way more than I probably want" items?
> Please what is Cis-Lunar's postal address for enquiries?
I'd love to ramble on and on about how the Cis-Lunar unit is designed, but
I have signed a non-disclosure agreement with them and I take that sort of
thing very seriously. If you can get your hands on a copy of the latest
aquaCorps ("C2"), which you really should do if you have a serious
interest in rebreathers, there is some information in there.
The "more than you probably want" aspect of this unit is that it was
designed for EXTREME cave penetration, and thus incorporates an enormous
amount of system-reliability design. Some have suggested that it's
over-kill for the majority of divers. As for me, I want that level of
reliability, even though I only do open-water dives. Yess, to me, it's
worth the $$$$$.
The person to contact is:
Richard Nordstrom
Cis-Lunar Development Laboratories
1 Ridgeway Dr.
Chadds Ford, PA 19317
> [OTHER SETS]
>
> > There are a number of other units which fall somewhere in-between.
>
> Any chance of a very brief list of names and prices, and names and addresses
> of their manufacturers / developers?, so people can enquire about them.
Unfortunately, I don't have that information with me. Perhaps others on
the list do?
> Richard Pile wrote:-
> > My advice is to attend tek 95 in San Francisco (January), where the
> horizon on available rebreathers will be much clearer. Aloha, Rich
> Please publish full details on `tek 95', times and dates, how to get there,
> and hotels etc, and likely total cost in money and time. Will any sort of
> Proceedings of `tek 95' be published? I have never been to America. I live in
> Manchester in England.
I don't have all the details with me right now, but I just now got off the
phone with Mike Menduno of aquaCorps. You can now reach aquaCorps at:
aquacorps@sh*.co*
Mike said he'll get on this forum very soon, and all aquaCorps-related
questions can be sent directly to him. It may take him a while, though,
because the whole aquaCorps staff is presently spending all waking hours,
7 days a week, trying to finish up the next issue ("Hard") and get it out,
so he doesn't have much time to sit down & learn the software.
I also asked him to send me an electronic version of the summary of the
rebreather workshop in Key West, which I will post on techdive as soon as
I get it.
Hope this helps.
Aloha,
Rich
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