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  #11  
Old 02-17-2012, 11:38 PM
rockwoodrv9 rockwoodrv9 is offline
 
Join Date: Dec 2011
Location: Meridian ID, Aspen CO, Okemos MI
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Default Airtight plane

I don't think I have ever flown in a light plane that was even close to air tight. I don't know anything about these oxygen generators, but I don't believe exhaust nitrogen would be too much of an issue.

My house is at 7200' and we are going skiing tomorrow at Snowmass - summit about 12,000. This oxygen generator appears to be in the same stage of development the re-breathers for scuba diving was a few years ago. With limits of 12,000, that is a little marginal for all but the -12. The one that is good to 15,000, that is getting pretty close to really nice. The ?bottle? is pretty easy and not that expensive now, but I can see a future for this type of a system. We have a couple of the very small, about 15 minute oxygen bottles we keep at the house for when we have guests. Maybe I should bring it with me skiing tomorrow!
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  #12  
Old 02-18-2012, 11:34 AM
johnny stick johnny stick is offline
 
Join Date: Dec 2008
Location: Los Angeles, CA
Posts: 301
Default Not ready for prime time?

I think it is an interesting thing to watch, but all the money in the world (OK in the US) could not build a good one for the F22/F35. And all the money could not finally fix the F22's. If even the military can't get it working, then I will wait a few more years. Bottles for me.
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  #13  
Old 02-18-2012, 11:56 AM
SHIPCHIEF SHIPCHIEF is offline
 
Join Date: Mar 2008
Location: Seattle
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OK, I'm demented;
But I just noticed that the Chinese use Potassium Superoxide rebreathers for their man in space program.
I trained on Navy OBA-4 rebreathers in 1973.
Rebreathers offer some real benefits, like scrubbing CO2, providing O2 and purging nitrogen from the breathing loop.
Here is an interesting article on rebreathers & mountain climbing:
http://www.velocitypress.com/closedcircuit.shtml
Now this is the only good reference I've found, and Chemox is expensive and/or no longer available. My search for KO2 ended with a sales pitch on Chinese space flight.
Bottled O2 for me, but I also found this interesting:
http://www.avoxsys.com/pdf/brochures/Aviox800.pdf
This must be the most expensive O2 you can buy, for such a short duration...and it gets pretty hot too.
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  #14  
Old 02-14-2016, 12:21 PM
MikeS MikeS is offline
 
Join Date: Aug 2006
Posts: 77
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Has anyone bought one of these portable oxygen concentrators and used it yet?

My regulator has been acting up and I'm again looking at the option of buying one of these portable concentrators. The Inogen One G3 seems to be the most highly rated but there are smaller ones, the AirSep Focus, that is even smaller. The Inogen G3 is rated to 15K and the Inogen G2 (larger and not on my short list) is rated to 18K. The Focus, the really tiny one, is rated to 12K.

So the G3 at this point is the best combination of performance and size.

Sure am tempted at this point to give one of them a try. Anybody done it yet?
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  #15  
Old 02-14-2016, 12:35 PM
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Ed_Wischmeyer Ed_Wischmeyer is offline
 
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Location: Savannah, GA
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Hopefully not too off topic, but if you go with a bottle system, portable bottles are much cheaper and easier to refill than built-in systems.
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  #16  
Old 02-14-2016, 01:53 PM
MikeS MikeS is offline
 
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Posts: 77
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I've got a bottle system. Have reglator acting up. Wondering if anyone has tried an oxygen concentrator yet. Name of thread is Oxygen options.
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  #17  
Old 02-14-2016, 02:56 PM
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6S4 Hugo 6S4 Hugo is offline
 
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I use an O₂ Concentrator. As far as "filling the cockpit up with nitrogen":

"The permanent gases whose percentages do not change from day to day are nitrogen, oxygen and argon. Nitrogen accounts for 78% of the atmosphere, oxygen 21% and argon 0.9%. Gases like carbon dioxide, nitrous oxides, methane, and ozone are trace gases that account for about a tenth of one percent of the atmosphere."

"The permanent gases in gas we exhale are 4% to 5% by volume more carbon dioxide and 4% to 5% by volume less oxygen than was inhaled. This expired air typically composed of: 78.04% nitrogen. 13.6% - 16% oxygen."

Doing the math tells me that the increase in cabin Nitrogen is about .04%. Not enough for inert gas asphyxiation in the cockpit I would imagine.

As far as altitudes above 12K feet: The oxygen concentrator can trade volume for concentration. Much like we can trade off speed for altitude you can turn up the flow rates up to 6LPM. Try that with your bottles and see how long they last.

My 2?, FWIW. Mileage figures given are an estimate and your mileage may vary...
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  #18  
Old 02-14-2016, 06:48 PM
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Ironflight Ironflight is offline
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I flew with the O2 Conetrators for a hill for test purposes - loved them! The only reason I didn't;t pick one up was economics. Well, and the fact that I couldn't fit it in the RV-3 cockpit. Yes - they work really well, and you will use O2 al the time, not try to conserve it becasue it is so hard to stuff back in those little bottles.

But - economics. You can fill a bottle a lot of times for the price.
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  #19  
Old 02-15-2016, 07:14 AM
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airguy airguy is offline
 
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Location: Garden City, Tx
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Quote:
Originally Posted by 6S4 Hugo View Post
I use an O₂ Concentrator. As far as "filling the cockpit up with nitrogen":

"The permanent gases whose percentages do not change from day to day are nitrogen, oxygen and argon. Nitrogen accounts for 78% of the atmosphere, oxygen 21% and argon 0.9%. Gases like carbon dioxide, nitrous oxides, methane, and ozone are trace gases that account for about a tenth of one percent of the atmosphere."

"The permanent gases in gas we exhale are 4% to 5% by volume more carbon dioxide and 4% to 5% by volume less oxygen than was inhaled. This expired air typically composed of: 78.04% nitrogen. 13.6% - 16% oxygen."

Doing the math tells me that the increase in cabin Nitrogen is about .04%. Not enough for inert gas asphyxiation in the cockpit I would imagine.

As far as altitudes above 12K feet: The oxygen concentrator can trade volume for concentration. Much like we can trade off speed for altitude you can turn up the flow rates up to 6LPM. Try that with your bottles and see how long they last.

My 2?, FWIW. Mileage figures given are an estimate and your mileage may vary...
That's not the source of nitrogen in question - it's the nitrogen from the concentrator. The concentrator pulls the oxygen out of the air and sends it to the pilot, and rejects the remainder which is almost entirely nitrogen. Since oxygen is 21% of the atmosphere, the concentrator is putting 4 times as much nitrogen into the cockpit as oxygen into the pilot.

I still don't think it's enough to worry about with our leaky cockpits.
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  #20  
Old 02-15-2016, 08:37 AM
bigginsking bigginsking is offline
 
Join Date: Aug 2005
Posts: 36
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I've been experimenting with a "run out" medical concentrator I picked up for $80 for about three years in my spare time. My plane is flying and I hate to do anything that will bring the plane down but this project has let me keep my technical chops going and not touch the plane. I've dumped a ton of time and money in it though.

The military has been using concentrators for years, the term they use is "OBOGS" on board oxygen generation system and many jets have replaced the liquid O2 systems with OBOGS. Even the Marine F-18s have almost completely ditched LOX for OBOGS and the Marines usually have the least funding for upgrades of any of the services. LOX is dangerous stuff, I've heard of at least one F-18 pilot that lost a chunk of his derriere from a leak.

When I got the run out device it was only making about 85% oxygen and the original electronics have interlocks that automatically shut down after a few minutes of not meeting spec (90 or 95%).

So I've removed all the electronics from the original and replaced them with my own that control the major functions that need to be done: running a compressor (BLDC), running a stepper motor that switches out sieve beds, thermal protection, and then dispensing an altitude dependent dose of oxygen when a user inhales. Lots of micro-controller programming...

I've got about 40 hrs flying solo with it, many of those hours are at 16.5k and 17.5k. I always use an oximeter and monitor it very closely. Useful consciousness at 18k is on the order of 20-30 minutes so this isn't like 25k or 35k where you really don't have much time to respond to an emergency.

Recently I have done some testing with two people and it is able to support two people at 17.5k with saturations of 95%. Small sample size though.

I really like the solution, most portable bottles will get you about 5 hrs for 2 people at 17.5k and then you're looking for a filling station. With this set up I don't hesitate to use it even when I'm lower.

I had a flight from San Diego to Jackson Hole last March with a massive headwind, I stayed at 11.5k and used O2 the whole time and didn't feel tired like I normally would after the nearly 6 hr flight. If I was using bottled O2 I wouldn't have wanted to waste it on a flight at 11.5k but with the concentrator its all free so why not?

The other advantage is that it's always ready to go so it's easier to use ad hoc. I've had two flights back from San Francisco to San Diego where a cold front with ice had piled up on the San Gabriel mountains and the only way home was over. It was a non event, no worrying if the bottle was full, if the valve was on, or if it leaked down from leaving the valve on between flights or anything like that. Just turn it on and go.

In all the experimentation I've done on this I'll say that O2 saturations vary widely between people, some people will have 98% at 14.5k with no O2 and others will have 88% at 10k. The one size fits all approach to Oxygen, specifically, you're at this altitude, you get this much, isn't necessarily right:

if you fly over 10k you should get a pulseOx and find out how your own body performs.

Also Pulse Ox's don't seem to vary much by what you pay for them, I've got an expensive Nonin and a cheap one from antisplat and they both generally agree with each other so don't let the cost be an obstacle.

Device specs: Current draw is variable but no higher than 15A at 14.4 volts, weight is on the order of 10 lbs.

Bill Judge
N84WJ, RV-8, 1240 hrs
http://rv-8.blogspot.com/
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