I started to be interested in rebreathers when I did an advanced nitrox course in the UK in 1996 and saw the internals of a CIS-Lunar mk4. In 97 I was going to do an Inspiration course with some friends, but couldnt make that due to work restraints. In mid 97 I found the rebreather mailing list and became an avid reader and started to search for all information published on rebreathers. Early Feb 98 I started to build my own rebreather, which took most of the year because of a lack of time, then started trials in the pool of my diving club and finally I am diving my "gas-factory".
The basic concept is that of a dual counter-lung type, front mounted, as found in several rebreathers, in production and pre-production, because of the advantages in breathing characteristics over back mounted counterlung systems. The counterlungs are water bags from MSR research, the 10-l. version, which I cut and glued to create the required dimensions. They have a 2" screw connection that is ideal to connect the "T" adapter to.
The "T" adapter which connects the hoses to the counterlung also functions as a water trap, routing all water that might come into the loop into the counter lung by means of a "bulkhead" mounted in the central connection tube (see the picture)
The scrubber is an axial scrubber containing 2 kg of absorbent, there is an air-insulating layer of 1/2" around the scrubber to keep the temperature of the scrubber bed high to improve efficiency. Under and on top of the scrubber there is a water trap where water can accumulate without impeding the function of the scrubber. The gas comes in from the underside, through the pipe at the side, which improves the scrubber dimensions and provides for a better and simpler construction.
The sensors are mounted in the top of the scrubber, at the exit port for the gas. Next to the sensors are the two housings for the batteries, closed but in a nice warm space. Also the solenoid has found its place here, but that is for a later part of the project. The three sensors are each connected to a digital voltmeter, adjusted (and adjustable) so that they show the pO2 directly. The digital voltmeters fit into a 1 1/4" Perspex tube that functions as the main read-out at the moment. Oxygen and diluent injection is through an inflator on the counterlungs.
The final part of the project is electronic set-point maintenance. The design is there and works on a simulation board (picture). It now needs testing of the control concept and repackaging into a handheld controller of the size of a normal diving computer and a mouthpiece mounted head-up display (the series of LEDs in the center of the board).
-Rob Bakker, Apr 99
Rob is happy to answer any questions via email
Extra note, 8/99: We asked Rob what his rebreather was called. . . He said:
The rig doen't have an official name, in April it was still a test bed. Now I have added a case ( an old Buddy Inspiration case) and wings and since it now looks a lot like an Inspiration I have put the name "Breathing Control Systems" on it to show it is not an Inspiration.