Modifications and how it all got started
PAGES HAVE BEEN POSTED TO SHOW WHAT I HAVE DONE TO MY REBREATHER ONLY !
If you cant get your head around
your own rebreather, you wont get your head around mine!
If for any reason you copy or Use
any of my ideas for yourself, then you do so at your own risk.
i will not be responsibile
for your actions
no mistake you are messing with life support systems,
GET IT WRONG
AND YOU DIE!
YOU HAVE BEEN WARNED
I brought 2x 5 litre Faber tanks complete with din
My rebreather, only having dived
it standard 3 times, this is what
I used to dive my rebreather
on a 7 litre cylinder and enjoyed it but it was a little too
wide having mounted it sideways
across the back.
However I did get some good
bottom times with this system, but I wasn't happy
with it as it still needed
I dumped the first
stage fitting as it was a pain the a..ss and replaced the
first stage fitting with a
200bar din male. See picture left of tank valve and Din
conversion. If you click on
the picture you can also see the thread sizes for both the
tank valve and din male fitting.
valves and they were much
I added an oxygauge and a
metering valve in series
with the jetting and doubled
my tank duration without a problem.
I found I could run higher
mixes deeper because
I could drop the flow back
with the metering valve on the fly...this worked well but I did have to
watch the bag volume, ie bypass valve as I could spike the mix!
I dived this configuration
for about three months before biting the bullet and designing a modification
for my rebreather to go fully closed.
I found this the best way
to dive, and now wont dive it any other way.
To do this I brought 2x 2.6
litre alloy tanks with din valves 200bar rated.
I designed and built 2x tank
mounts to bolt onto the shell of my Dolphin along with a
proper carry handle on the
back. Watch the original handle as it will in time crack your
shell. This mount has been
so good that I would miss it if I ever took it off.
Below is the tank mounting system
to the shell, I clicked this picture while I was still mounting it.
Next I added 2x Poseidon first
stage regulators with din fittings and o2 cleaned both
for up to 100%. One for dilutant
and the other for 02 and o2 cleaned one of the
tanks and labelled it accordingly.
You can see in the pictures
below the completed tanks mounts and also the Poseidon
first stage regulators.
Here is a photo of the reusable
hose fittings that I used to make up all the fittings.
They disappeared off the market
here in Oz but I was told just the other day that they are available.
I then designed the dilutant addition
by using the
existing bypass valve as it
was already there so
might as well use it....since
taking this photo
I have added Gordon Smiths
the demand valve housing,
and is covered in a separate page.
I found that the spring in
the bypass valve was design
for 16 bar line pressure and
I was using 8.5 bar so it was
replaced with the spring from
the demand valve of a US divers
Con shelf SE regulator and
this worked beautifully, I could open it with ease no matter fast I descended. This
next shot shows the dosing head in place inside the harness and shell.
note see photo above that this has since been changed and
the dosing head now resides between the two hose connections on the back
shell, and has proved to be much better. However I have left this shot
on the page to show how it used to be piped up.
The contents gauge for
the dilutant is over the shoulder and clips to the D ring on right hand
side of the harness.
I also took a feed from the
diluent first stage and brought it over the shoulder and across
to the left hand side and
used an Air2 as a bailout and BC inflation...this is a godsend.
See in the above shot I have dragged
it out and you can see it attached to the Air-2.
I designed the o2 injection
using a Clippard Minimatics MJV-2 two port upstream
valve and o2 cleaned it, put
it in series with the needle valve seen here attached to the body of the
Clipphard bypass valve.
Flow rate at 8.5bar first
stage pressure was 10 litres per minute, this means that it
would take approx one minute
to fully flush the loop if for some reason the valve
jammed open I would have plenty
of time to fly the rig if needed by using the tank valve.
Nice and simple backup ..remember
you have to keep it all simple! Contents gauge is over
the left shoulder and lies
next to the Air2 and is easy to see.
O2 addition is by Gordon's Kiss
method and manual add and I find now after many hours that I can fly
the unit almost without instruments...I would never do this but it is very
predictable and it only takes one or two shots of o2 for every 45 minutes
to keep the ppo2 stable.
Quite often I find I can go
up to one hour without adding any additional O2 to the loop.
Lastly I added 2x oxyguages
to the rig and have them programmed to low setting .35
and high setting 1.4 and I
fly the unit around .9 - 1.0 most of the time.
And that's my system,
I have chosen to supply you with pictures so you can see what
its all about but I'm sure
you wont have any problems understanding how it all works.
Here is a picture of my rebreather
with its shell removed for you to look at.
I might add that since this
photo was taken I have added
Kiss system to the rig and
am now working on more juicy mods which will probably
mean another re-write of this
page. I am now a CCR convert and
will never change the unit back to SCR.
Duration is 10-12 hours so
I can take the rig diving for a weekend and never have
to worry about tank fills
and of course there is "No Mixing".
Two rebreathers have now been
built and they perform exactly the same
with an average gas consumption
of 10bar per hour, meaning it is not uncommon to go
for a days diving with 60
bar of O2, however I do-not encourage this!
I brought a third 3 litre
tank and I use that for Helium plus air for deep dives, this replaces
the air dilutant and
BC inflation is taken from my 5 litre Faber's one on each side
Air bailout on the left and
and a 60 mix for deco on the right.
Funny thing is that I have
been having so much fun with marine life around the inshore reefs where
I live in North Queensland that I have not taken the rig past 30 meters,
100 feet in the imperial measure.
I had ideas of a new shell and have produced an experimental unit but time
and money have beaten be to
Instead I have replaced the
original BC with my old faithful Sea Quest Black Diamond.
Since these photos were taken
I have upgraded the BC to the latest Black Diamond
with what I can only describe
as OUTSTANDING RESULTS.
This is one of the nice things
about this system as you can place any B.C. on the
rebreather using the "A" frame.
To fit it up to the rebreather
shell first I had to make up a frame.
If you look closely you
will see a slot in the centre towards the top of the picture.
This is where the second half
of the frame which is attached to the BC fits into.
Once I had the frame fabricated
it was easy to bolt up to the old holes left from
the original shell. I used
316 grade stainless steel and because I did not have access to a Tig welder
used silver solder and found it to be very strong and easy to weld together.
Once I had a basic frame around
the shell the rest was simple, I made up an "A" frame and mounted this
to the back of my Black Diamond BC.
See picture below
This bolts straight up to
the BC as it already had holes for mounting twin tanks so a simple "A"
frame was no problem to bolt up. I sweated nuts onto the other side of
the "U" bends to make it easier to attach and remove, also the original
tank straps stay in place and don't get in the road so in a few minutes
the BC cant be put back to standard for a normal scuba tank.
This is what the finished
frame looked like see below.
Here is another shot of
the shell and BC mating up together.
As you can see it is just
a matter of tilt and slide into position, then fit and tighten the two
stainless steel dome head bolts to the bottom of the shell these can be
seen better in the picture of the completed frame.
And there it is the rebreather mounted
up to the Sea Quest BC
Below is my dive buddy Frank Feather
modelling the set-up.
Next came the pool testing of the
new configuration which went extremely well finding that
I did not need as much lead weight
as with the original BC.
One of the nice things with the Sea
Quest is it has 50 pounds of lift and a nice weight integration system.
The weight of the stainless
steel frame offsets some of the positive bouenceny of the counter lung and
it was good to see also that when the unit was floated by itself that it sat
vertical, this would make it easy to don in-water should the need arise.
Since these pictures
were taken I have added a little bit of weight to the shell,
to offset the extra chest buoyancy when wearing a wetsuit.
It's tough diving in the tropics;-))
Ok that concludes for the moment
all of the mods that I have done to my rebreather
for the time being ;-)) For more
Go to the Final Dolphin pages to see
what the completed unit now looks like and the final changes that make the
rebreather what it is now.
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