IDA-55 Teardown

The IDA-57 is a simple and robust 02 rebreather designed in 1955. It is a very close technical sister to the early Draeger rebreathers, and was used in service through the early 1970's. They are fairly rare, having been discarded as replacement equipment became available. I was fortunate enough to obtain a new (undived) example for my collection, and present it without further fanfare for inspection. I'll dive it this spring, as soon as the weather warms up, and have high expectations for it. It will be interesting to compare it to a Draeger LAR-III, which is the oldest Draeger that I have available. It'd be more comparable, I think, to a Draeger Lieutenant Lund, which is the most widely known of the first-generation 02 rebreathers. This rig is certainly represents prewar 02 rebreather design, its postwar date notwithstanding. Without further comment, let's get down to business:

This is the rig laid on the bench, with the front of the rig up. The black fabric is merely a cover over the counterlung, not the actual counterlung itself. The "Chassis", as it is, is simply an assembly of glued rubber pieces, reminding me of the heavy-weight material used to make the commercial-duty Viking drysuits.

Unsnapping the cover and folding it back, we can see the counterlung underneath. This is looking at the top of the rig, the 02 bottle on the right has already been removed. The brass overpressure relief valve is seen at the top right of the photo, which would be at the divers right hip when the rig is donned.

The oxygen bottle is steel, with a working pressure of 200 BAR. It appears to be a 1.5 liter cylinder. The valve outlet is what appears to be 3/4 BSP, a standard European gas connection. It is, in fact, the same exact fitting used to fill the much more recent AKA-60 semiclosed circuit rebreather.

The scrubber is made from aluminum, and loads from the bottom. The exhale side of the DSV is connected directly to the top. On the side you can see the port that connects to the counterlung.

The counterlung is made from rubberized fabric, and has the usual valving (described below) as well as the inhale side of the DSV hose, and the connection (lower right) for attachment to the scrubber.

This is the entire loop, assembled outside the rubberized chassis. This is about as simple as it gets, and makes a great skeleton view of how the basic components of a rebreather are laid out. It looks like one of those line-drawings of "How does a rebreather work" found in the textbooks, doesn't it?

Just another view of the assembled components. This display is going to be an integral feature of any RB show-and-tell that I might ever give, as it really shows the most basic features of a breathing loop without any extras.

The valving on the counterlung is simple, yet elegant. On the extreme right you can see the inlet fitting from the 02 cylinder. The little plunger that I have my finger on is a really neat feature. You push it when the bottle is filled to cock it, and then when the cylinder is almost exhausted it snaps back with a "Clang" to give a one-time signal to the diver that the rig is almost empty of gas. Neat and simple!

On the top of the valve, where it is easy for the diver to reach it, is the manual override button. Pressing this fills the counterlung from the cylinder for manually flushing the loop.

This is the automatic addition valve. It is nothing more that the stock Russian 2-hose regulator body and mechanism, integrated into the counterlung. The Russians are famous for using the same hardware in any application for which it is suited, and this is a perfect example of that philosophy. It sure makes it easy to keep spare parts on-hand!

Once all of the components are removed, here is the 'Chassis' of the rig. This entire assembly is of extremely high quality construction, and took a great deal of thought to design. Little design features abound.

One such design feature is the little anti-abrasion tabs found under the buckles that are near the counterlung. These little details make the difference between a rig that will last forever and one that will wear-out in a short time.

Here you can see how the rig is attached to the chassis. The loops and straps are well shown. In actuality, this set of loops should also have the chassis-cover installed, as the 02 bottle weight is born by it, and not the counterlung. I've removed the cover and then re-threaded the strap through the counterlung loop for clarity of the photograph.

At the top of the rig, the fabric cover is attached by the simple method of using a snap and ring. The snap is on the neck-strap, and the (2) rings are the attachment to the chassis, and the attachment of the front cover-flap. Unsnap the snap and the cover may be lifted for servicing the rig. On the other side you will see two rings: The other side of the neckstrap passes through the ring that secures the other side of the front-flap, and then attaches to the weight-bearing ring. When the strap is loosened, the front flap may be lifted on this side as well. This is a clever, yet simple manner for securing the flap.

This is the view by the diver, looking down at the top of the rig. From the right, you can see the 02 valve, the neck-strap snap, the manual flush button, the inhale DSV hose, the other side of the neck-strap with the twin-rings as noted above, and the scrubber cannister, to which the exhale hose attaches. Clean and simple.

For all of that, the rig came with the most bizarre full-face mask I have ever seen. Twin eye-ports (of untempered glass, no less) are mounted below an exhaust valve flapper just like those in 2-hose regulators. The mouthpiece of the mask threads onto the DSV. Hmmmm....... I would seem to me that one of the Russian designers had some sort of latex fetish, but I'm sure that did not make him a bad person. But, that said, you aint gonna see -ME- wearing this mask. Not even at Halloween. No sir.

With all respect to the former statement, this is actually not a badly designed system. Notice that there are no head-straps. Rather the entire thing is like a hood. Also you can see the mouthpiece that keeps the gas space of the mask interior partially isolated from the loop. The diver equalizes the hood by exhaling through his nose, and the hood is kept from inflating and being lost upon ascent by the exhaust tube. it's all very 1930's, but it apparently would work OK.

That's all folks! This is a neat addition to the shelf, and I think it makes a great teaching tool for introducing the concepts of a rebreather. As I said earlier, I'll dive it in the Spring to see how it dives. I'd guess that it would be comparable to any other well-designed front mounted 02 rig, but we shall see!

	This is the rig laid on the bench, with the front of the rig up. The black fabric is merely a cover over the counterlung, not the actual counterlung itself. The "Chassis", as it is, is simply an assembly of glued rubber pieces, reminding me of the heavy-weight material used to make the commercial-duty Viking drysuits.
	Unsnapping the cover and folding it back, we can see the counterlung underneath. This is looking at the top of the rig, the 02 bottle on the right has already been removed. The brass overpressure relief valve is seen at the top right of the photo, which would be at the divers right hip when the rig is donned.
	The oxygen bottle is steel, with a working pressure of 200 BAR. It appears to be a 1.5 liter cylinder. The valve outlet is what appears to be 3/4 BSP, a standard European gas connection. It is, in fact, the same exact fitting used to fill the much more recent AKA-60 semiclosed circuit rebreather.
	The scrubber is made from aluminum, and loads from the bottom. The exhale side of the DSV is connected directly to the top. On the side you can see the port that connects to the counterlung.
	The counterlung is made from rubberized fabric, and has the usual valving (described below) as well as the inhale side of the DSV hose, and the connection (lower right) for attachment to the scrubber.
	This is the entire loop, assembled outside the rubberized chassis. This is about as simple as it gets, and makes a great skeleton view of how the basic components of a rebreather are laid out. It looks like one of those line-drawings of "How does a rebreather work" found in the textbooks, doesn't it?
	Just another view of the assembled components. This display is going to be an integral feature of any RB show-and-tell that I might ever give, as it really shows the most basic features of a breathing loop without any extras.
	The valving on the counterlung is simple, yet elegant. On the extreme right you can see the inlet fitting from the 02 cylinder. The little plunger that I have my finger on is a really neat feature. You push it when the bottle is filled to cock it, and then when the cylinder is almost exhausted it snaps back with a "Clang" to give a one-time signal to the diver that the rig is almost empty of gas. Neat and simple!
	On the top of the valve, where it is easy for the diver to reach it, is the manual override button. Pressing this fills the counterlung from the cylinder for manually flushing the loop.
	This is the automatic addition valve. It is nothing more that the stock Russian 2-hose regulator body and mechanism, integrated into the counterlung. The Russians are famous for using the same hardware in any application for which it is suited, and this is a perfect example of that philosophy. It sure makes it easy to keep spare parts on-hand!
	Once all of the components are removed, here is the 'Chassis' of the rig. This entire assembly is of extremely high quality construction, and took a great deal of thought to design. Little design features abound.
	One such design feature is the little anti-abrasion tabs found under the buckles that are near the counterlung. These little details make the difference between a rig that will last forever and one that will wear-out in a short time.
	Here you can see how the rig is attached to the chassis. The loops and straps are well shown. In actuality, this set of loops should also have the chassis-cover installed, as the 02 bottle weight is born by it, and not the counterlung. I've removed the cover and then re-threaded the strap through the counterlung loop for clarity of the photograph.
	At the top of the rig, the fabric cover is attached by the simple method of using a snap and ring. The snap is on the neck-strap, and the (2) rings are the attachment to the chassis, and the attachment of the front cover-flap. Unsnap the snap and the cover may be lifted for servicing the rig. On the other side you will see two rings: The other side of the neckstrap passes through the ring that secures the other side of the front-flap, and then attaches to the weight-bearing ring. When the strap is loosened, the front flap may be lifted on this side as well. This is a clever, yet simple manner for securing the flap.
	This is the view by the diver, looking down at the top of the rig. From the right, you can see the 02 valve, the neck-strap snap, the manual flush button, the inhale DSV hose, the other side of the neck-strap with the twin-rings as noted above, and the scrubber cannister, to which the exhale hose attaches. Clean and simple.
	For all of that, the rig came with the most bizarre full-face mask I have ever seen. Twin eye-ports (of untempered glass, no less) are mounted below an exhaust valve flapper just like those in 2-hose regulators. The mouthpiece of the mask threads onto the DSV. Hmmmm....... I would seem to me that one of the Russian designers had some sort of latex fetish, but I'm sure that did not make him a bad person. But, that said, you aint gonna see -ME- wearing this mask. Not even at Halloween. No sir.
	With all respect to the former statement, this is actually not a badly designed system. Notice that there are no head-straps. Rather the entire thing is like a hood. Also you can see the mouthpiece that keeps the gas space of the mask interior partially isolated from the loop. The diver equalizes the hood by exhaling through his nose, and the hood is kept from inflating and being lost upon ascent by the exhaust tube. it's all very 1930's, but it apparently would work OK.