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Tip: Adapting a Roscoe Pediatric Medical Oxygen Regulator for 2 Place Aviation Use

Guy Prevost

Well Known Member
Before we start, a few important notes.

1. You must clean all of these parts thoroughly with a water based, non flammable cleaner before attaching them to oxygen. The presence of any grease, lubricant, oil, etc can very easily start a fire. As soon as one of these easy to start items begin to burn, the metal (in the presence of pure oxygen) will start to burn too. This is not a fire you want in your cockpit!

2. If you do set yourself on fire using this info, it is not my fault. This is how I built mine. For all you know, I'm a complete moron.

OK. Disclaimers taken care of. I purchased a Roscoe Pediatric regulator and a couple of D sized Aluminum cylinders on Ebay. I looked long and hard for a medical regulator that had an NPT threaded output, but have not been able to find one. If someone does find one, please post the info!

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The Roscoe has a hose barb output that attaches with a metric thread. I don't have a lathe, so I had to kludge my setup together. I removed the hose barb from the regulator and figured out what size metric thread it had.

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I then bought a tap of the same size and a stainless steel metric bolt. I cut the end off of an NPT nipple and drilled and tapped the ID for the metric bolt.

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I then cut the head off of the bolt and drilled a hole through the center. After a thorough cleaning, the bolt was threaded into the nipple with Teflon tape in order to make an adapter.

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I used the rubber gasket that came with the barb fitting and attached the nipple to the regulator.

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The last step was to add a T and a pair of oxygen safe dry break connectors from Mountain High.

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I tested for leaks in a sink full of water.
I make it a point to always turn the bottle off for takeoff and landing. If the regulator and bottle are turned on, I like to always have at least one cannula attached as I don't want to risk a leak at the fittings. If a leak happens around a gasket it can create heat and that can lead to fire. Even though I don't have any leaks, the regulator was not designed to have a valve after it, so I keep a cannula attached if the gas is flowing.
 
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I have the same exact regulator, which I bought on eBay for around $25. Since I have a lathe I cut the barb off the fitting and drilled a hole for a 1/8" NPT thread into the fitting itself. There's enough meat left in the fitting to run a 1/8" bottoming pipe thread tap into it. I was able to thread one of the same CPC fittings I got directly from the manufacturer at a fraction of the cost MH sells them for.
 
how much did you pay for the different materials?

I think I paid about $20 for a pair of new bottles. The regulator was about $25. I bought the cannulas and CPC fittings from Mountain High out of convenience, but I'm sure better deals could be had elsewhere. If I remember right, the cannulas and fittings nearly doubled the cost of the system.

I also bought a transfill system that will let me fill the medical bottles or aviation bottles from a welding cylinder.
 
Guy, thanks for the tip and write-up. (same to you Bob).

For the RV-8(A), where do you fix the bottle so it is reachable in flight?
 
Thanks for the links. I read them a while back. The one thing I saw in the archives that was close to what I'm asking was a picture of a tank mounted horizontally on the back of the RV-8 pilot seat.

I'll have to test the theory. I'm not sure I'm flexible enough to open the valve once flying.

I was hoping Guy could explain his install since he was recommending "turning off the oxygen for take off and landing".

I'll install a dummy mock-up to the back of the seat and see if I can reach it.
 
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Guy, thanks for the tip and write-up. (same to you Bob).

For the RV-8(A), where do you fix the bottle so it is reachable in flight?

I hang mine front the crossbar behind the front seat when dual. When solo, I usually just set it in the passenger footwell. I really should secure it better for the latter case...
 
Same here;
I use a a medical C bottle & Precision PM-168708D regulator which only weighs 7.4 ounces.
It flows .25 to 8 LPM, but has the hose barb off the end. It can't be modified like yours.
I had planned to mount the bottle in the cockpit, and give the back seater their own C bottle & regulator. It's a crude form of redundant safety.
My system is lighter for one user, yours is lighter for 2 users.
Bravo!
 
Guy, Bob, and anyone else who's "rolled your own", I have a few questions.

I have procured a couple of "D" sized bottles I. Good condition. I also scored a Devilbiss pulse Dose regulator for about the same price as the pediatric units you suggested. (I was bidding on both and won auction for the PD4000 first so that's what I end up with.) for now, I'm building a single person system. If / when I deed passenger O2, I'll probably install a duplicate setup.

Now the question. Since all the parts are "used" I am not sure if I am missing any o-rings or gaskets. My regulator has a green rubber gasket but it does not seem to be removable.

Is there an o-ring or gasket between your regulator and the bottle? Is it easy to remove / replace?

BTW - I discussed bottle placement with the builder of my RV-8. Of all the placement options, he liked the "well" in the front baggage compartment. I'm adding a little "boot" and retaining straps in that location to take the "D" bottle standing upright.
 
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question about barb fitting

This question is to Guy and Bob or anybody else that did something similar - I am putting my own system together, and all the parts haven't arrived yet. Maybe the answer will be obvious once I get everything in front of me. Did I mention I have zero experience with o2?

I'm wondering why you went through all the trouble of replacing the barbed fitting coming out of the regulator. Is it just a piece of mind thing, or will it blow off under any kind of pressure? I'm guessing a little pressure builds up in the line when using a downstream pulse demand system of any kind since o2 is still flowing at the regulator. Even the oxysaver style cannula would build a little back pressure since it shuts off flow during the inhale breath. But aren't medical patients using pulse demand devices/cannula's too? If lines were blowing off all the time for patients, I can't imagine the barbed fitting would be the industry standard. What am I missing?

Thanks!
 
For a single user, there is no reason to replace the barb fitting. I wanted the ability to switch between 1 user and 2 users without having free-flowing O2.

This way, O2 flows only when a cannula is attached, since the connectors stop the flow when there is nothing connected.

If you left both cannula attached to a Y fitting with a valve afterwards that would work too. It would just leave more hoses (clutter) around, and the possibility of forgetting to turn on (or off) a valve.
 
I wrap the hoses with safety wire where they're pushed onto barbed fittings, for peace of mind since it could potentially be pulled off in flight. Therefore the quick connectors are necessary to put everything away.

A few weeks ago I used my tank for several hours at 17500. Everything worked perfectly.
 
where do we learn how to use it safely?

I like the idea of flying high, and having an o2 system, but if I have a regulator ice up at 18,000, I think I'm screwed, and that scares the heck out of me!

there seems to be no redundancy, so are they any ex-military guys or other users who can advise?.....
if you blow a hose, or have a failure, what's the procedure? ..emergency descent seems obvious, as you have only a few minutes of clarity, if not consciousness at that altitude ( I'm told). Do you folks who use ox plan for or practice emergency 4000 fpm descents?

(I'd hate to see a perfectly good RV glide to earth, with a couple of 'statistics' sitting inside!)
 
I like the idea of flying high, and having an o2 system, but if I have a regulator ice up at 18,000, I think I'm screwed, and that scares the heck out of me!

there seems to be no redundancy, so are they any ex-military guys or other users who can advise?.....
if you blow a hose, or have a failure, what's the procedure? ..emergency descent seems obvious, as you have only a few minutes of clarity, if not consciousness at that altitude ( I'm told). Do you folks who use ox plan for or practice emergency 4000 fpm descents?

(I'd hate to see a perfectly good RV glide to earth, with a couple of 'statistics' sitting inside!)

One of the things that you can do for peace of mind is to take some high altitude physiological training, including a chamber ride or hypoxia simulation. this will help you to understand and recognize your own personal hypoxia symptoms. the truth is that at 18,000', the average person has a time of Useful Consciousness of 20-30 minutes...you're not talking a short couple of minutes. You can get down from 18,000 to 14,000 pretty quickly in an RV - it doesn't have to be anywhere near red line.

if you are worried about not recognizing your symptoms before something bad happens, you can always use a pulse oxymeter to monitor your saturation levels - check it every couple of minutes if it makes you feel better.

The truth is that while I have tested and flown my RV-8 in the Flight Levels, it is rarely practical to go that high unless you get one of those incredible rip-roaring winter tailwinds. Yes, fuel flow is minuscule at 18,000, but TAS is dropping off pretty quickly at that altitude as well, so you have to win the wind lottery to make it work out. When it does though....whoo-hoo!!

I just did my recurrent chamber training yesterday - we try to do it every three years - and if you are serious about operating up high, it is a very good idea to know your own symptoms - most FSDO's have a way for you to sign up for it (I get it at work), so you might check with them. {edit: Just realized you're in Canada, so the FSDO comment is more for other folks - I am not sure if training is generally available to our neighbors to the north....}
Paul
 
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Time Of Useful Consciousness

I've seen this table in different spots, but everybody's different so it's a general guide but by no means absolute.

http://en.wikipedia.org/wiki/Time_of_useful_consciousness

The table says you have 20-30 minutes of TUC at 18k feet. That means you better be checking your flowmeter every 15 minutes if you're at that altitude. A portable pulse-ox is a good idea too.

I'm not flying with o2 yet, but I plan to have the TUC times somewhere handy along with the flow rates to use at various altitude. I'm interested to hear what others that fly higher than 10k do for this kind of thing. I don't see myself getting that high very often since I fly mostly in the flat lands, but it's nice to have the tool on the "tool belt". I also plan to get to OK City as soon as practicle for a free high altitude chamber ride. Anybody with a medical can do it compliments of the FAA.
 
I put in an Aerox flowmeter just below the oxysaver pendant. I don't think I would do that again because one can easily see the pendant fill up after taking a breath, and a lot of the time you can see it in the reflection on stuff on the panel.
 
For a single user, there is no reason to replace the barb fitting. I wanted the ability to switch between 1 user and 2 users without having free-flowing O2.

This way, O2 flows only when a cannula is attached, since the connectors stop the flow when there is nothing connected.

If you left both cannula attached to a Y fitting with a valve afterwards that would work too. It would just leave more hoses (clutter) around, and the possibility of forgetting to turn on (or off) a valve.

Barb fittings do just fine (single, "Y", etc.). But be careful with the one on the regulator. They will break and then no more oxygen!
 
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