IDA-71 Rebreather CAD

I recommend that no one go into water using an IDA-71 rebreather. This system completely lacks modern safety features and it is very likely that diving with a fully functional, mint condition IDA-71 will get you killed. This article is written merely as an engineering study.


     In my continuing quest to maybe someday fix up my old IDA-71 rebreather (but probably never actually use it, because that probably would be unwise), I've drawn up CAD models (Solidworks, STEP, and STL) for most of its parts which are now available on my GrabCAD page. I'm almost done, as a matter of fact. I've drawn just about everything except the shell, the nitrox connections, the scrubbers, and the soft parts (hoses, counterlung). The main purpose for all of this is so I can get a better idea of how all this stuff fits together and how it all really works. And, since I'm a mechanical design engineer, I'm always looking for opportunities to tear apart and study a complex mechanical system. Almost all parts of the rebreather are made from brass, but they're all anodized (heavily) with what might be nickel. It is not a light piece of equipment and it's not simple.

     The valve assembly on top of the oxygen tank is amazingly complex. There are an unbelievable number of parts inside this thing. I should really draw up a functional/flow diagram. It's an incredibly impressive piece of equipment. Seriously, this is an incredibly dense piece of hardware. Every part of it is adjustable and every time you remove what you think is a solid, single part, you look more closely and see that there are half a dozen more parts inside.

     I'm not exactly sure what we should call this piece. I call it the air add valve, because that's basically what it does. It's a clever little device and again I'm amazed at how much functionality is crammed into such a small object.

     The mouthpiece/flow director is probably the only part of the system that doesn't surprise me with its complexity or size. I guess there's not much you can do to make it smaller. A certain flowrate of air requires a certain size hose.

     I've also drawn up the counterlung vent valves, the pressure gage, and some of the other random hardware. I might never CAD up the nitrox system, because it's ridiculously complex. As in, I haven't even managed to disassemble the entire thing, complex. However, all the drawings shown here are available on github. Currently they're only uploaded as Solidworks drawings. I could eventually convert them to .step files or something similar, but I don't know how useful that would be. Like I said, the main purpose for creating these drawings is for design analysis, and to do meaningful design analysis you need to be able to read dimensions and see the assembly and so on. More to come in the near future.