Diver Daves' LAR-V Page

The Draeger LAR-V is one of the most highly regarded pure 02 rebreathers available. Part of this cachet is due to the use of this unit by the US Navy SEAL Teams, as well as the refusal of Draeger to allow their sale to the general public. Irrespective of this, several examples of these rebreathers have found their way (legitimately) into the hands of civil users. A very simple unit, the LAR-5 is merely an updated version of earlier Draeger 02 rebreathers. The follow-on to the LAR-V, the LAR-VII, is almost identical with the added feature of being able to be used with 50% nitrox to extend the depth range. I have found the LAR-V to be a very simple and reliable rig, and have spent many pleasurable hours in the shallows of the rocky coves of the Rhode Island coast watching fish while using this device. Yet another use of the unit has been to support 02 decompression for remote area operations where large quantities of oxygen would need to be carried in for use with open circuit. Well, enough of the talk, on to the rebreather. As always, please email me and I'll be happy to answer any questions that you may have. Thanks!

Here is the rig laid on the bench, showing the cylinder and the shell. The LAR-V is a chest-worn rebreather, and the harness is a simple neck-strap and waist-strap. In use, many divers cross the straps across the back to give a bit more secure attachment. I have dived it both ways, and have little preference. Notice the issue number, 31, painted on the shell. This is common for military units that need to be rapidly identified.

This is the view of the rig as seen by the diver. The pressure gauge is on the top, where it can be seen with little difficulty while in use. The exit of the hoses is from the top, and the short hoses feed a typically excellent Draeger DSV. The manual add valve in on the center of the front of the shell, and can be pushed with ease even with a gloved hand, yet is not susceptible to inadvertent injection, even when crawling on your belly over sand and rocks.

Here the rig is laid on it's shell, with the counterlung facing up. When worn, this counterlung faces the divers' chest, so this is the view when donning the rig. You can see the oxygen cylinder across the bottom, and the first stage regulator at the bottom right. Also visible are the breathing hoses and the DSV. All in all this is an extremely compact and simple unit.

A close-up view of the front of the shell, with the manual addition button in the center of the photo, and the two cutouts for the breathing hoses at bottom left and right. The pressure gauge for the 02 quantity is also visible between the hose cutouts.

Cylinder retention is done with a pair of heavy rubber straps, which are attached to the frame of the unit by the plastic clips shown. The connection of the regulator to the valve does not require any tools, as a rubber handwheel is provided.

Here, I've removed the cylinder and the valve and inlet to the regulator are shown. The inlet connector of different LAR-V versions vary, as different Naval purchasing specifications were complied with the suit individual users needs.

US Navy LAR-V versions use a 3/4 inch diameter connection, actually of the same thread as used on a regular 3/4 inch SCUBA cylinder valve. The steel supply cylinder has metric pipe-threads and you can see the metallic tape on the valve threads into the cylinder to form a seal. Filling adapters for these units are rarer than the units themselves. I have had adapters machined on a custom basis, and may have a spare or two if anyone looking at this ever requires one.

Flipping up the counterlung, the balance of the breathing loop becomes visible. The scrubber is now shown, and you can see that one of the same type of rubber straps that is used to secure the cylinder is also used to secure the scrubber.

The valve and regulator are, of course, typically German in quality. Note the safety wire sealing the cap of the first stage. Also note that the black cylinder in the middle of the photograph is an overpressure relief valve which would prevent a blown line in the event of a failure of the high-pressure seat of the first stage.

For the purpose of analysis, I removed the entire loop as a system. You can see that the scrubber feeds the inlet hose, and the divers exhaust gas is fed into the counterlung. The counterlung is connected to the scrubber, and that's it. The one fitting on the middle of the counterlung is fed by the auto/manual addition valve, to provide the loop with oxygen. This is as simple as a rebreather loop can be made.

All connections on the rig are of either a thread-on, or are the quarter-turn type, so that the component to be installed is merely held 90 degrees in orientation to the hose and then they are rotated into place. This is a very neat system. If there are tow components side-by-side, one of each connector is used. In this way, it becomes impossible to incorrectly assemble any component of the system. Here the quarter-turn connection of the inhale hose is shown in detail.

The military requirements to 'Diver Proof' the system are taken to an extreme. Even the hose connections to the DSV are color-coded to make sure it is assembled correctly.

Looking into the exhale hose, we can see the one-way flapper valve. Red = Bad, so we know that this is the exhaust valve by the Draeger logic of 'Dirty' or 'Bad' gas being 'Red' gas.

Looking into the chassis, we see here the connection of the counterlung to the auto/manual add valve. You can see that it is of the thread-on type. The nearby hose feeding the scrubber from the exhaust hose is the quarter-turn type, for the reasons described above. Looking just above the add valve you can see the bottom of the high-pressure gauge.

Here the counterlung has been removed exposing the workings of the addition valve. You can see the simple tilt-valve mechanism of the regulator, and the back of the diaphragm. This is nothing more than a simple demand SCUBA regulator. Pushing the rubber purge-valve on the front of the rig adds 02 manually. Breathing in against a collapsed counterlung adds 02 automatically. Neat and simple. The two stainless steel lines feeding the addition valve and the high pressure gauge are clearly seen.

Looking into the now removed counterlung, additional details become visible. The fitting shown here is provided with a coiled spring inside to prevent collapse of the inlet area of the connection. This is the connection of the divers inlet breathing hose.

The scrubber is made from fiberglass, and is provided with perforated stainless steel baffles to retain the scrubber material. You can see the spring used on the plate of the removable end of the scrubber to securely hold the scrubber material from shifting. This is an important part of the LAR-V's design, as it was intended to not be vibration sensitive. Conventional scrubbers will 'pack' if subjected to the vibration of shipboard machinery or helicopters, but the LAR-V is essentially immune to this type of problem.

With the scrubber and counterlung removed, all that remains is the shell with the pneumatics system installed. Here, I am beginning to reassemble the unit, having attached the 02 bottle to the bottom.

Here is the stripped rig from the top, with the gauge clearly shown. This is the divers view straight down when wearing the unit. You can see the molded protrusion where the manual add valve purge is located on the front of the rig.

That's about it for this simple and extremely successful rebreather design. Embodying the typically high level of German engineering that we have come to expect from Draeger, this rebreather stands as a superb demonstration of the simplicity of design of a basic pure 02 system.

	Here is the rig laid on the bench, showing the cylinder and the shell. The LAR-V is a chest-worn rebreather, and the harness is a simple neck-strap and waist-strap. In use, many divers cross the straps across the back to give a bit more secure attachment. I have dived it both ways, and have little preference. Notice the issue number, 31, painted on the shell. This is common for military units that need to be rapidly identified.
	This is the view of the rig as seen by the diver. The pressure gauge is on the top, where it can be seen with little difficulty while in use. The exit of the hoses is from the top, and the short hoses feed a typically excellent Draeger DSV. The manual add valve in on the center of the front of the shell, and can be pushed with ease even with a gloved hand, yet is not susceptible to inadvertent injection, even when crawling on your belly over sand and rocks.
	Here the rig is laid on it's shell, with the counterlung facing up. When worn, this counterlung faces the divers' chest, so this is the view when donning the rig. You can see the oxygen cylinder across the bottom, and the first stage regulator at the bottom right. Also visible are the breathing hoses and the DSV. All in all this is an extremely compact and simple unit.
	A close-up view of the front of the shell, with the manual addition button in the center of the photo, and the two cutouts for the breathing hoses at bottom left and right. The pressure gauge for the 02 quantity is also visible between the hose cutouts.
	Cylinder retention is done with a pair of heavy rubber straps, which are attached to the frame of the unit by the plastic clips shown. The connection of the regulator to the valve does not require any tools, as a rubber handwheel is provided.
	Here, I've removed the cylinder and the valve and inlet to the regulator are shown. The inlet connector of different LAR-V versions vary, as different Naval purchasing specifications were complied with the suit individual users needs.
	US Navy LAR-V versions use a 3/4 inch diameter connection, actually of the same thread as used on a regular 3/4 inch SCUBA cylinder valve. The steel supply cylinder has metric pipe-threads and you can see the metallic tape on the valve threads into the cylinder to form a seal. Filling adapters for these units are rarer than the units themselves. I have had adapters machined on a custom basis, and may have a spare or two if anyone looking at this ever requires one.
	Flipping up the counterlung, the balance of the breathing loop becomes visible. The scrubber is now shown, and you can see that one of the same type of rubber straps that is used to secure the cylinder is also used to secure the scrubber.
	The valve and regulator are, of course, typically German in quality. Note the safety wire sealing the cap of the first stage. Also note that the black cylinder in the middle of the photograph is an overpressure relief valve which would prevent a blown line in the event of a failure of the high-pressure seat of the first stage.
	For the purpose of analysis, I removed the entire loop as a system. You can see that the scrubber feeds the inlet hose, and the divers exhaust gas is fed into the counterlung. The counterlung is connected to the scrubber, and that's it. The one fitting on the middle of the counterlung is fed by the auto/manual addition valve, to provide the loop with oxygen. This is as simple as a rebreather loop can be made.
	All connections on the rig are of either a thread-on, or are the quarter-turn type, so that the component to be installed is merely held 90 degrees in orientation to the hose and then they are rotated into place. This is a very neat system. If there are tow components side-by-side, one of each connector is used. In this way, it becomes impossible to incorrectly assemble any component of the system. Here the quarter-turn connection of the inhale hose is shown in detail.
	The military requirements to 'Diver Proof' the system are taken to an extreme. Even the hose connections to the DSV are color-coded to make sure it is assembled correctly.
	Looking into the exhale hose, we can see the one-way flapper valve. Red = Bad, so we know that this is the exhaust valve by the Draeger logic of 'Dirty' or 'Bad' gas being 'Red' gas.
	Looking into the chassis, we see here the connection of the counterlung to the auto/manual add valve. You can see that it is of the thread-on type. The nearby hose feeding the scrubber from the exhaust hose is the quarter-turn type, for the reasons described above. Looking just above the add valve you can see the bottom of the high-pressure gauge.
	Here the counterlung has been removed exposing the workings of the addition valve. You can see the simple tilt-valve mechanism of the regulator, and the back of the diaphragm. This is nothing more than a simple demand SCUBA regulator. Pushing the rubber purge-valve on the front of the rig adds 02 manually. Breathing in against a collapsed counterlung adds 02 automatically. Neat and simple. The two stainless steel lines feeding the addition valve and the high pressure gauge are clearly seen.
	Looking into the now removed counterlung, additional details become visible. The fitting shown here is provided with a coiled spring inside to prevent collapse of the inlet area of the connection. This is the connection of the divers inlet breathing hose.
	The scrubber is made from fiberglass, and is provided with perforated stainless steel baffles to retain the scrubber material. You can see the spring used on the plate of the removable end of the scrubber to securely hold the scrubber material from shifting. This is an important part of the LAR-V's design, as it was intended to not be vibration sensitive. Conventional scrubbers will 'pack' if subjected to the vibration of shipboard machinery or helicopters, but the LAR-V is essentially immune to this type of problem.
	With the scrubber and counterlung removed, all that remains is the shell with the pneumatics system installed. Here, I am beginning to reassemble the unit, having attached the 02 bottle to the bottom.
	Here is the stripped rig from the top, with the gauge clearly shown. This is the divers view straight down when wearing the unit. You can see the molded protrusion where the manual add valve purge is located on the front of the rig.