Mark-15 Rebreather Bailout

Mark Webb-Johnson has worked out a very nice system for mounting utility and bailout gas on his Mark-15. This system is just one of the various systems that people have made up, but it now stands as perhaps the nicest one I've seen to date. Let's take a peek!

For the non-Alpinists among us, carrying sufficient gas for bailout and normal gas switching on a rebreather has posed a problem since we first began using this sort of equipment. Here we see a Mark-15 opened up to show its two internal spheres, as well as a neat system of mounting adequate bailout and suit/wing inflation gas, all on neatly made attachment brackets. Visible are (2) 30 ft/3 cylinders on either side of the rig, as well as a 15 ft/3 cylinder across the ass.

The side mounted 30's are carried on quick-attachment plates made by "Tiger Gear", who makes all sorts of plate systems for mounting this and that on normal cylinders. Mark was able to convince them that they ought to make a mounting foot with a flat contour (as opposed to the cylinder-radius contour normally provided) for mounting on rebreathers. I'd looked at these plates a year ago (Tiger is a local company to me) and had asked about flat backs, but never bugged them long enough to get any. Mark got on their case and got the job done. Nice work!

Here's what the aluminum mounting plates for the cylinders looks like. The components are hard-anodized and are extremely "Aerospace" in design and execution.

The side mounted cylinders can be released by pulling the pin shown and then sliding the cylinder up just a few inches to unlatch it from the backing plate. This is a NEAT system.

The entire goal of offboard gas is to be able to provide the loop with a second type of diluent, and to allow the diver to leverage the offboard gas in a semi-closed mode bailout. The core of the system on a Mark-15 is this selector valve, which has been added by many users. This allows selection of an offboard gas source. The 90 degree stainless-steel elbow has a supply hose attached, and at the other end is a quick-disconnect fitting to allow the rig to be quick-connected to offboard gas sources.

Here's the other end of the offboard hose. Just under the Primary Display (showing "alarm-low PP02", BTW!) is the other end of the offboard supply whip, terminated in a Swagelok QC-4 quick disconnect. This whip is plugged in as needed to any supply cylinder fitted with compatible connections. The QC-4 has become the defacto standard for this application, and if you run across another Mark-15 diver, there's a good chance of compatibility. Kevin Juergenson was the first one to set up rigs like this, and he did well in making the component selections.

The "Ass Mount" was a brain-storming project of my own "Diveshop of Horrors" in conjunction with final design and prototyping from Enrique Alverez, who now fabricates them to order. I originally wanted a utility bottle mount that would carry a suit/wings inflation cylinder, and which would also support the rig in an upright position for racking the rig on the boat and for donning the rig, as well as servicing. After about three trial versions, all which came out too heavy, this is the final design. The end result is a titanium mount that was designed to support the rig at the correct angle to allow the center of gravity to sit properly so the rig would stand up on its own. I think this photo demonstrates this last feature nicely!

Another view of the rig sitting on the ass-mount. Nice, aint it? In this view, the hose with the QC-4 quick-disconnect is clearly shown running over the left shoulder.

That's it for this system. It seems the neat way to do it. Here's some of the comments that Mark made while we were discussing the system:

"I ordered (the mounting plates) from Jeff Back [jback@catskill.net] of TigerGear. He didn't have a specific product code, but I guess you talk to him and tell him it's the same flat-plate pony bottle mount that Mark Webb-Johnson (Pro-Dive HK-USA Ltd, TDI South China, Hong Kong) got. The pony-bottle side of the mount is unchanged. The change was to make the former-main-tank side a flat plate that can be bolted to a flat surface (MK15). Positioning on the MK15 is critical; you need to slant slightly forward (at the top) and back (at the base) in order to clear the manual-add buttons. You should get a rough idea of positioning from my pictures. It's actually a pretty clear area of the MK15 casing (between curves of spheres and center section) so you shouldn't have too much difficulty. I used three (of the four) bolts to hold in place; the fiberglass casing seems plenty strong enough. Very stable in the water."

		For the non-Alpinists among us, carrying sufficient gas for bailout and normal gas switching on a rebreather has posed a problem since we first began using this sort of equipment. Here we see a Mark-15 opened up to show its two internal spheres, as well as a neat system of mounting adequate bailout and suit/wing inflation gas, all on neatly made attachment brackets. Visible are (2) 30 ft/3 cylinders on either side of the rig, as well as a 15 ft/3 cylinder across the ass.
		The side mounted 30's are carried on quick-attachment plates made by "Tiger Gear", who makes all sorts of plate systems for mounting this and that on normal cylinders. Mark was able to convince them that they ought to make a mounting foot with a flat contour (as opposed to the cylinder-radius contour normally provided) for mounting on rebreathers. I'd looked at these plates a year ago (Tiger is a local company to me) and had asked about flat backs, but never bugged them long enough to get any. Mark got on their case and got the job done. Nice work!
		Here's what the aluminum mounting plates for the cylinders looks like. The components are hard-anodized and are extremely "Aerospace" in design and execution.
		The side mounted cylinders can be released by pulling the pin shown and then sliding the cylinder up just a few inches to unlatch it from the backing plate. This is a NEAT system.
		The entire goal of offboard gas is to be able to provide the loop with a second type of diluent, and to allow the diver to leverage the offboard gas in a semi-closed mode bailout. The core of the system on a Mark-15 is this selector valve, which has been added by many users. This allows selection of an offboard gas source. The 90 degree stainless-steel elbow has a supply hose attached, and at the other end is a quick-disconnect fitting to allow the rig to be quick-connected to offboard gas sources.
		Here's the other end of the offboard hose. Just under the Primary Display (showing "alarm-low PP02", BTW!) is the other end of the offboard supply whip, terminated in a Swagelok QC-4 quick disconnect. This whip is plugged in as needed to any supply cylinder fitted with compatible connections. The QC-4 has become the defacto standard for this application, and if you run across another Mark-15 diver, there's a good chance of compatibility. Kevin Juergenson was the first one to set up rigs like this, and he did well in making the component selections.
		The "Ass Mount" was a brain-storming project of my own "Diveshop of Horrors" in conjunction with final design and prototyping from Enrique Alverez, who now fabricates them to order. I originally wanted a utility bottle mount that would carry a suit/wings inflation cylinder, and which would also support the rig in an upright position for racking the rig on the boat and for donning the rig, as well as servicing. After about three trial versions, all which came out too heavy, this is the final design. The end result is a titanium mount that was designed to support the rig at the correct angle to allow the center of gravity to sit properly so the rig would stand up on its own. I think this photo demonstrates this last feature nicely!
		Another view of the rig sitting on the ass-mount. Nice, aint it? In this view, the hose with the QC-4 quick-disconnect is clearly shown running over the left shoulder.