Requested by Tom Rose:
03.15.2007   rev   04.14.2007

Crestline Experimental Dive Unit
The CEDU
 Field Expedient Push-to-Add Valve
Made, and Used in Tahiti

Tom Rose asked me to post some information about the Manual Addition Valves which I had to Improvise for one of my FEOR homebuilt rebreathers.

In Tahiti I found myself with cylinders that I was not able to fill, and unable to obtain small medical oxygen cylinders locally.  Thus I scrambled to find oxygen.  Well, would you believe it that an ACE Hardware store was found on the island, complete with those little red oxygen tanks that I loved so much in the past.  I was set, except that I did not have my little Push-to-Add valve in my bag of tricks.  I did however have an assortment of vinyl tubing with me, and the know how to use it.

I know that the red O2 cylinders have a schrader type valve, and all I needed to do was some way to push on it.  As you can see in the above image, a gas pathway to the breathing loop was made using vinyl tubing and hose clamps.  Various diameter brass rods were obtained, (you don't think that I would use clothes hangers do you).  A smaller diameter rod was heated in a flame and plunged  into the vinyl tubing while being directed toward the schrader valve.  That hot rod melted a path through the two thicknesses of vinyl tubing.  Than a larger diameter rod was inserted into the path just formed.  The tight, interference fit between this rod and the pathway acted as a water tight seal.  This last rod, bent 90 degrees became the handle.  And thus, a Field Expedient Push-to-Add valve was made.  (I think you can figure out how I operated this valve.  If you can't, don't ask.)

It was clumsy, but it did not leak and worked perfectly.  Of course if used often it would eventually loosen up and leak from wear.  But it satisfied its design requirements, and satisfied its Mission: to Dive my FEOR in Tahiti.  (One must always remember these units are very mission specific. What satisfies one mission requirement, may not satisfy another.  Not one tool can be used for every job. although that is exactly how some manufacturers sell their wares.) 

If interested, you can read more of the details concerning my Tahiti rebreather dive from the link below:
http://www.cedu-diver.com/tahiti.htm
 

CEDU Bonus Post:
 

CEDU's Push-to-Add Valve
(As used on various models of the FEOR Standard.)

Push-to-Add valve seen on the FEOR ClearView.

 I first presented the FEOR (Field Expedient Oxygen Rebreather) at the 1999 Rebreather Party. [link follows]

http://home1.gte.net/doctrbob/CEDU005.htm

At that time I used the Oxygen valve as supplied by the manufacturer of it as used for another purpose.  Twisting the existing valve clockwise and anti-clockwise allowed me to add oxygen to the rebreather as I choose.  The only modification to the valve at that time was to drill through the stem with a #47 drill, in order to increase the volume of gas flow through it.

This is pretty much the valve as supplied with the 'kit'.
Turn the black plastic knob CW and CCW(or AW) to start and stop the flow of Oxygen.
(The stem, not shown in the picture, had been drilled through to allow greater gas flow.)

It didn't take to many dives in Southern California with 1/4 inch wetsuits and neoprene gloves to discover that I was not handling this valve arrangement as delicately as it was originally engineered for.  Cold fingers in neoprene gloves decreased the tactile feedback necessary to know when to stop turning the valve.  While turning the valve clockwise to the off position, I have turned the entire valve off the red cylinder.  Not a desirable attribute.  (OK, I am hard on my equipment. But that is what R&D is all about.  Don't you just love it.  I do!)  An improvement, or modification, was in order.  I modified it into a Push-to-Add valve. (Images of it on various units can be seen on the following links.)

http://cedu-diver.com/oxdive4.htm

http://cedu2.tripod.com/feormod.htm

What I did was disassemble the valve, discard the parts I did not need, and kept the parts I did need, and finally make a 'push button' for the valve.

The image below shows the expanded parts that are used in the Puss-to-Add valve modification. (As mentioned, the only part actually made is the black finger plunger which is seen second from the right.)  The drill is shown in this picture to remind you that I drilled out the bore of the stem.  The drill fits the inside diameter of the stem and was allowed to open up the bore at its restriction.

Item fabricated was the plastic plunger, second from the right. (Discarded items not shown.)

I did not show the parts of the valve that I discarded, but they include the black plastic knob, a spring, a plate, and some other long forgotten, rusted items.

Close up of the plunger.

    For informational purposes, the valve houses a schrader like valve within the body. The red Oxygen cylinder also has a schrader like valve at the head.  When the valve is connected, <remember left hand threads>, the pin on the bottom of the valve depresses the schrader valve of the cylinder and the gas flow is stopped by the schrader valve in the valve body.  The twist on/twist off valve compresses a spring which eventually presses upon a diaphragm, which then presses a plunger which presses the schrader valve of the valve body allowing gas to escape down the stem.  I eliminated all the "twist-ie", "spring-ie" parts, and replaced them with a plastic plunger.  Thus, one simply needs to Press the button, to activate the schrader valve within the brass valve body under the diaphragm.

Close up of the valve on the red cylinder. Note valve marked "oxygen" and "left".
                                                          ("left", indicating left hand threads.)

The official CEDU Field Expedient oxygen source.
(Always check the latest MSDS for it's suitability of your intended use.)

The valve in its present configuration works well, and I have used it often. 

The red cylinder is very limited, with only about 31 liters of oxygen there is not much bottom time available.  And if you use it in a pure O2 unit, there is much less useable gas (time) after you fill the entire loop.   But it has it's uses.  It was a great training tank, and was the tank of last resort for me in Tahiti, (see above).   Another thing about that cylinder is that it is made of a metal that rusts very fast in salt water.  By the end of the dive the threads are rusted.  This is a ONE USE ONLY cylinder, not to be refilled under any circumstance. (Trust me on this one.)  Another problem with the cylinders is that I did not have a good way to determine their state of charge.  They come with about 31 liters of gas at just under 500 psi. Without a pressure gauge it was a hit or miss situation as to the starting quantity of gas.  ( I have purchased cylinders that came empty from the store, bummer! )  I have tried to weigh the cylinders, but have found a variation in cylinder to cylinder weight, thus that system proved of limited value, about the most use was to indicate if the tank is empty.

Tom,
Hope this is what you were asking me about.
Smile,
Bob              

NEWS UPDATE:              BET MADE GOOD

On or about 10 April 2007  the following winning prize, a slightly used $20 dollar bill, right out of the pocket of YANKEE REBEL arrived in the mail. (Don't ask me how I can tell.)

    I must thank a number of people for these new found riches.  First I thank Yankee Rebel for demonstrating that he is a man of his word in awarding this prize as stated.  This demonstration of fidelity shows that he is a man of fine character.  It was an honor to have our paths cross.  And I must also thank Tom Rose for informing me about Yankee Rebels offer that was  posted in the Rebreather World website. (I must start reviewing that site.)   Tom has many interests, is abreast and knowledgeable of many different subjects and is generous in sharing things that friends, or even strangers, may find of interest.

Thank you,
    :)  Bob

Disclaimer:  The usual disclaimers regarding information presented here are in place.  These webpages are for my pleasure and your informational entertainment only.  Using rebreathers are dangerous enough, making and diving them are more dangerous, and using and/or modifying equipment in ways it was not designed just about eliminates any deep pocket payments lawyers for your survivors may seek. 
 

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