As some of you know I have been working on a Russian IDA 71 rebreather project.
For those uneducated in the '71 check oput Dave Suttons excellent site on RB's http://www.nobubblediving.com/ida-71.htm

My aim is to convert the CCCR (Chemical Closed Circuit Rebreather) into a KISS style mCCR. Below is a pic of the progress so far....


This is close to completion of stage 1 which is a CMF (Constant Mass Flow) O2 rebreather.
It uses pure O2 as the breathing mix so is depth limited to 6 meters.

Left is the 2 Litre O2 tank that feeds the ADV (auto delutant valve) on the black hose. This simply adds more gas if the counter lung (not shown) emptys while inhaling. The green hose feeds the CMF valve and manual add valve (shown below).

Centre is the scrubber canister which holds 1.8 kgs of sofnolime. This square cannister is split in half length ways so the gas travels in the top turns around at the bottom and exits top right.

Right is the BC/drysuit inflator tank. This feeds a gas block (top left) that then splits off to the BC and drysuit inflator hoses. In the future this tank will become the dilutant tank and then also feed the ADV and also I will have an off board dilutant tank that will also plumb into the gas block.
The extreem bottom right is a SPG mounted on the inflator tank and obviosly cant be read while the unit is in use. But there should be more than enough gas in the tank for many dives as a O2 unit.

Below is the Manual add valve and CMF valve will a ball valve as a gas shut off.

Stage 2 will see the addition of PO2 monitoring and offboard dilutant/bail out supply. But that is a long time off yet.

Well I just completed my first IDA 71 pool dive!

To be honest I felt like I was straight out of a Open Water class.
Trim was terrible as I need alot of lead up high to counter the bouyancy from the counter lung.
Bouyancy has really hard. Having 2 seperate bouyancy devices to deal with and one of them (the counter lung) having a slowly changing size is a little tricky especially at 3-4 meters.

Anyway I came away from the 40 minute dive with a small list of improvments I need to make and a desire to get back in ASAP. Perhaps at the next SODS pool night!!!
See you there, I will be the one with no bubbles!!

Congratulations on surviving to tell the tale!

Untill RB's, or anything come to that, has a way to monitor C02 i'm not interested at all.
02 sensors=cheap and relatively reliable. Especially when grouped. C02 sensors=unbelievably expensive and not that reliable-unless your with NASA. I'm waiting untill the technology gets to a point that it can tell me when the C02 has built up and i'm about to die. Untill then they are not for me.

Stumbled across this little beauty whilst at work..




It's a Siebe Gorman "Salvus" we haven't used them since the 50's so a bit before my time... And yes it does make me look like a Gimp..

So am I gonna try and make it into an underwater breather?


HELL NO!!!

Well one year after my first dive on the IDA I finally got my first mixed gas CCR dive done on my IDA 71.

For those of you that dont know the IDA range of rebreathers are Russian Military units. The IDA 71 was designed in 1971.

Yeah yeah, I hear you. But this is not the Lada of rebreathers. Its more like the Mig 25 of rebreathers. These were built at the hight of the cold war and no expense was spared in its design.

Originally designed as a pure O2 Chemical Closed Circuit Rebreather (CCCR from CCCP) it also had the option of an off board 40% nitrox tank for use or depths below 20 meters. There were several types available. A standard unit, an anti magnetic version for mine clearing and also a unit for high altitude parachutists.

Anyway.... I have probably done away with half of the original set up. What is left is the aluminium case, twin parallel scrubber cannisters, counter lung,Over pressure release valve, Auto add valve and many fittings.

Trim has been improved with about 4kgs of lead above and below the counter lung.



The breathing loop consists of a MK15 DSV, rubber hoses from Abyss Rebreathers in Australia, 90 degree brass fittings from Bunnings soldered to the stock IDA connectors.



The counter lung has been modified. Instead of the exhale tubes traveling through the inside of the counter lung I have rerouted it out of the lung.
On the left of the lung I have added a P port that holds 2 O2 sensors that are read by a rEvo dream hand set and HUD.
On the top of the lung is the stock Auto add valve. This is basicly just like a second stage reg and when the lung collapses it adds more air.
Only one scrubber is shown but for dives deeper than 20 meters or for a weekend of diving I will use 2 scrubbers..

The tank on board provides O2. This feeds the O2 valve you can see connected to the green hose. It consists of a CMF (constant mass flow) valve that provides 0.8 litres of O2 per minute plus a manual add valve to add extra O2 when required.

Diluent is supplied off board by what ever sized tank is suitable for the dive. This connects via a quick connect to a delrin manifold that splits the gas off to the ADV, Wing, and drysuit.

The ADV has been modified so it has a button that pushes against the ADV diaphragm to add more diluent when required. Another Manual add valve for diluent much like the O 2 add valve will be added shortly.



My main aim for the set up was to try and keep it as clean as possible. Especially after diving with a couple of other RB divers who seem to have hoses, pipes, displays, valves and wotsits hanging everywhere. So far I am very pleased with the outcome and feels its a well laid out design. But who know, I may soon feel the need for more hoses, pipes and wotsits.





So whats next?
Add a crotch strap to the harness.
Change the DIL set up with addition of a swaglok quick connect and MAV (Manual add valve )
Water trap.
Set it up for twin scrubbers again.
Add a 3rd O2 sensor using another P Port and connect it up to a VR3 computer.
Add a BOV ( Bail Out Valve).
Add a small 1 Litre tank dedicated to wing and drysuit inflation

Good stuff Packie! I've got my first breather dive on Tuesday..

That last pic is quite surreal with those folk standing in the background

rEvo dream with P Port containing 2 O2 sensors and HUD

Apeks DS4 1st stage connected up to CMF and MAV

Dil distribution block.

That looks awesome! I look forward to seeing it in action!