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This email was sent to techdiver@opal.com a couple of days ago and bounced back
as 'undeliverable'. Maybe this was an error of mine or with the system.
Anyway, I'll try it again. If you've already seen it....Sorry.
On Wed, 26 Oct 1994 12:02:17 +0000 (GMT) Matthew Cobby wrote:
>
>
> On the question of rebreathers, does any one know of a heliox rebreather
> recently released in the UK for about 1500 pounds ? At this kind of
> price it is coming into the reach of non-profesionals, but have they had
> to cut any corners to get this price tag ?
The rebreather that I know of that nearly fits your info is the "Prism"
semi-closed circuit rebreather. This is marketed at 2000 pounds. You have to
provide your own 'wings' BC, 2*cylinders and bail-out regulator. For the 2000
you get a rebreather bag, a CO2 scrubber unit, various hoses, straps and a
mouthpiece plus a 'constant mass' gas flow valve and a built in oxygen ppO2
sensor. It seems a lot of money for not very much, IMHO. 1-day 'taster'
courses are presently being held at several locations. I don't know of any in
Scotland.
I went on a 1-day course. The Prism is very functional and not at all
pretty. This is unimportant, but it has a definate 'Heath-Robinson' feel to
it.
The cylinders are both filled with a breathable N2/O2 or He/O2 mixture, which
can be used for bail-out on open circuit. The constant mass flow valve
continually feeds the bag with mixture, which vents off every so often (less at
depth). You are breathing a constant mix rather than the constant ppO2
breathed on a fully closed circuit rebreather. Dive times of 6 hours are
possible. This is limited by the CO2 scrubber rather than gas availibility, in
spite of the venting. If you wanted to adjust/reduce the ppO2 manually, then
you could do this by turning the flow valve down and keeping a careful watch on
the ppO2 meter. You risk going hypoxic doing this, plus if you have to bail
out
on open circuit then the mix in the cylinders could easily give an O2 hit (!).
You have to dive using square profile deco tables. Your max depth is limited
by
the mix in the cylinders, hence you must have planned the diving BEFORE filling
the cylinders.
The Mk5 Cis-Lunar is the "Rolls-Royce" compared to the "Volkswagon"
Prism, with a similar difference in what you pay and what you get. This is a
fully closed circuit rebreather selling for about 8000 pounds (!). At the NEC
dive show a Mk4 model has head-up display of warning led's, a 3 microprocessor
redundancy, constant ppO2 and an integrated mixed gas computer to work out
decompression times. With this rebreather in principle you can just jump in
and
'see what happens'. The constant ppO2 will keep the mix from being too hypoxic
or hyperoxic and will result in significantly shorter deco times. The computer
will track your times, depths and mix breathed and will sort out your deco
stops. Deco is done automatically on a 1.6 bar ppO2, going down to 1 bar (pure
oxygen) as you near the surface.
1-day taster courses are also presently being held for Cis-Lunar in
Poole, Dorset. I am planning to go on one in Jan '95. The Mk5 is just a
cosmetically improved version of the Mk4. I'm not sure how you bail out of a
fully closed rebreather, other than strapping a 12 litre extra heliox cylinder
to your waist.
Other models soon to appear include the Oceanic/Carmellan Research
closed circuit rebreather and a Japanese (Sea & Sea ?) semi-closed nitrox
rebreather. The Draeger rebreather currently being developed looks like being
'Military only' and hence of no interest to us.
>
> I'm looking for extended dive times and not have any chance of narcosis,
Aren't we all....!
> and heliox is too expensive to use on open-ciruit for more than the odd dive.
Absolutely !
I think all this info is already availible to the techdiver BBS (?),
so,I have only mailed you directly. Is it worth sending a copy of this letter
to techdiver@opal.com do you think ?
>
Regards, Steve M.
*******************************************************************************
* * *
* Dr. S. G. Millard * E-Mail : ec96@li*.ac*.uk*
*
* Department of Civil Engineering, * *
* University of Liverpool, * Tel : 051 794 5224 (UK) *
* PO Box 147, * 44 51 794 5224 *
* Liverpool L69 3BX, * (International) *
* UK. * *
* * Fax : 051 794 5218 (UK) *
* * 44 51 795 5218 *
* * (International) *
* * *
*******************************************************************************
--
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Regards, Steve M.
*******************************************************************************
* * *
* Dr. S. G. Millard * E-Mail : ec96@li*.ac*.uk*
*
* Department of Civil Engineering, * *
* University of Liverpool, * Tel : 051 794 5224 (UK) *
* PO Box 147, * 44 51 794 5224 *
* Liverpool L69 3BX, * (International) *
* UK. * *
* * Fax : 051 794 5218 (UK) *
* * 44 51 795 5218 *
* * (International) *
* * *
*******************************************************************************
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