After deciding to go down the route of a sidemount rebreather last weekend I developed the idea a bit further. The ADV did not work especially well so I tried something new. I also added a connection for the oxygen metering valve. One of the problems I hit last week was that the controls were hard to reach on the side of the bag so I built a remote control system for manually adding diluent and O2. The final step is to house the whole system in a caving tackle bag. The picture shows my yellow bag of doom next to someone else's yellow box of death. The bag has a couple of loops which allow it to be clipped on at the waist and shoulder.
	Here is the remote control system. These are push-button valves on the end of a length of LP hose. The valve with the blue button is the manual oxygen addition valve and the other is the combined ADV and manual diluent addition valve. They are tee'd together using Swagelok parts and fed into the counterlung with a Lapp gland. The diluent valve is combined with an ADV. This is a modified Scubapro AIR II. The mouthpiece and exhaust valves have been sealed and the dump valve modified so that air would flow through the corrugated hose rather than the mouthpiece. If the counterlung bottoms out during a breath then the diaphragm on the AIR II flexes on the lever and opens the 2nd stage valve. On my backmounted twinset I replaced the back-up regulator with a large bore Scubapro quick release to connect to the diluent valve.
This shows the rest of the guts of the rebreather and its yellow bag of doom (the fins are not part of it). The grey tube spliced into the corrugated loop hose is to extend the inhale side to compensate for the length of the counterlung in the exhale side.

The tackle sack idea was good but too bulky, I need something narrower. Also the bag seemed to restrict the counterlung in the water, it was far easier (and easier to manage) with the scrubber and counterlung attached on their own with no cover. The dive went well apart from the restricted lung. The ADV functioned as planned and the remote controls worked but they need thought through as to hose routing and where to attach them.

Again, the electronics worked perfectly too. Flushes with both diluent and oxygen underwater gave a displayed ppO2 exactly as predicted. One big problem that I hit was that I did not connect the O2 metering valve because I wanted to run the rebreather manually for testing. What I forgot was that the attachment for it was a drysuit inflation valve that had been modified to be always open. Without the metering valve connected then the counterlung was essentially open to the water. I remembered this during the dive when I started to hear a gurgle. As the dive went on the gurgling got worse so I abandoned the dive because I wasn't sure how the rebreather would react. With the backmount rebreather the lungs acted as water traps but on the sidemounted rebreather I did not have that feature. The scrubber was still functioning but when I removed the p-plug on the bottom about 1/2 a litre of caustic water poured out (I knew it was caustic because every tiny scratch I had on my hand started to burn like fire). Not good. I need to come up with something to get water out of the loop. In this configuration there is nothing to stop any water entering the counterlung to straight to the scrubber, down the exhale pipe and pool in the bottom of it until either it creates a breakthrough channel or starts finding its way up the inhale hose.