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#11
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Why nitrogen?
"Viperdoc" wrote in message
... ... Need to see the aging data on rubber kept in air versus nitrogen. I've seen it at work, fwiw. Some difference. But, for car tires, I would say there is more hype than benefit. -- Geoff The Sea Hawk at Wow Way d0t Com remove spaces and make the obvious substitutions to reply by mail When immigration is outlawed, only outlaws will immigrate. |
#12
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Why nitrogen?
I don't know whether nitrogen alone versus plain old air would make that
much difference in supporting a fire. As I recall, the heavies have blow out plugs in case of a hot brake, so the plug melts and lets the air (nitrogen) out before the tire blows. On our base they fill the KC-135 tires in a big steel mesh cage- kind of a reminder of what could happen if it let go. Reminds me of the time a line guy in a local airport filled the air bottle for a Vendenyev engine (they use an air start and not an electrical starter) with oxygen rather than compressed air. The resulting fire burned up the whole plane. The initial start-up must have been something to watch- ignition on, engage starter, two blades, .... then kaboom! At least it was in a Wilga, and not an aerobatic plane. It was the aviation equivalent of Darwinism- ridding the world of ugly airplanes. |
#13
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Why nitrogen?
"Viperdoc" wrote in
: I don't know whether nitrogen alone versus plain old air would make that much difference in supporting a fire. As I recall, the heavies have blow out plugs in case of a hot brake, so the plug melts and lets the air (nitrogen) out before the tire blows. That's right. they do, but they can and do catch fire as well. On our base they fill the KC-135 tires in a big steel mesh cage- kind of a reminder of what could happen if it let go. Reminds me of the time a line guy in a local airport filled the air bottle for a Vendenyev engine (they use an air start and not an electrical starter) with oxygen rather than compressed air. The resulting fire burned up the whole plane. The initial start-up must have been something to watch- ignition on, engage starter, two blades, .... then kaboom! wow! At least it was in a Wilga, and not an aerobatic plane. It was the aviation equivalent of Darwinism- ridding the world of ugly airplanes. So, the O2 fueled an already existing fire or caused it? Bertie |
#14
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Why nitrogen?
"Capt. Geoffrey Thorpe" The Sea Hawk @See My Sig.com wrote in
: "Viperdoc" wrote in message ... ... Need to see the aging data on rubber kept in air versus nitrogen. I've seen it at work, fwiw. Some difference. But, for car tires, I would say there is more hype than benefit. Used to put it in the tires of my light plane, mostly because it was free. I flew off grass and reckoned they'd rot before I wore them out anyway, so I might as well get the most bang for the buck out of the tires. Bertie |
#15
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Why nitrogen?
So, the O2 fueled an already existing fire or caused it? I suspect that pumping the oxygen into the system somehow started the fi it probably is a new definition for the term "hot start" |
#16
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Why nitrogen?
On Sep 16, 8:20*am, a wrote:
On Sep 15, 6:09*pm, "Viperdoc" wrote: The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. The legend is that *the oxygen is reacting with the rubber. Even though compressed air has the same fraction of oxygen as does the atmosphere, the fact that it's compressed, it's been argued, increases its reactivity. I can't validate the legend. Thats is not a legend its a fact rubber is very prone to oxidation which is why it contains chemical antioxidants, and the reactivity will be proportional to the concentration , ie pressure of the oxygen. I am not however saying that is the only reason otherwise why dont we put nitrogen in our car tyres. Terry |
#17
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Why nitrogen?
On Sep 16, 8:25*am, a wrote:
On Sep 15, 6:20*pm, a wrote: On Sep 15, 6:09*pm, "Viperdoc" wrote: The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. The legend is that *the oxygen is reacting with the rubber. Even though compressed air has the same fraction of oxygen as does the atmosphere, the fact that it's compressed, it's been argued, increases its reactivity. I can't validate the legend. I got curious, did a quick check. The process also reduces water vapor, and N2 does not migrate through the rubber as fast as does O2, so pressure stays more predictable. So it's more consistent tire pressure, less corrosion.- Hide quoted text - Dont see why it would reduce water vapour, dry air has no more water than dry nitrogen. and migration or porosity is a function of molecular size. There is not much difference between nitrogen MW 28 and Oxygen MW 32. Terry |
#18
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Why nitrogen?
"Viperdoc" wrote
I suspect that pumping the oxygen into the system somehow started the fi it probably is a new definition for the term "hot start" In that engine, the compressed air is injected into the top of the cylinders by an air distributor at about the same time as the spark is fired. (it also has a "shower of sparks" system) This sometimes results in the engine firing (and starting) before it seems like it even turns. In the YAK-52, the compressed air also operates the retractable gear, the flaps and the brakes. Bob Moore |
#19
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Why nitrogen?
On Sep 16, 6:39*pm, terry wrote:
On Sep 16, 8:25*am, a wrote: On Sep 15, 6:20*pm, a wrote: On Sep 15, 6:09*pm, "Viperdoc" wrote: The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. The legend is that *the oxygen is reacting with the rubber. Even though compressed air has the same fraction of oxygen as does the atmosphere, the fact that it's compressed, it's been argued, increases its reactivity. I can't validate the legend. I got curious, did a quick check. The process also reduces water vapor, and N2 does not migrate through the rubber as fast as does O2, so pressure stays more predictable. So it's more consistent tire pressure, less corrosion.- Hide quoted text - Dont see why it would reduce water vapour, dry air has no more water than dry nitrogen. and migration or porosity is a function of molecular size. *There is not much difference between nitrogen MW 28 and Oxygen MW 32. Terry- Hide quoted text - - Show quoted text - OK , I will stand corrected, on the porosity, the proper word was permeation and nitrogen is actuallly a larger molecule than oxygen despite its lower molecular weight. Attached link is a really good explanation ..from an expert. oxygen does permeate 3 to 4 times faster through rubber. I guess leakage through the tire would occur even faster in an aircraft tire at altitude due to the driving force of the pressure differential. But still not convinced if its the primary reason.. I think I am leaning towards the fire risk. Anyways its a very interesting aviation topic. Terry http://www.getnitrogen.org/pdf/graham.pdf |
#20
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Why nitrogen?
a wrote:
On Sep 15, 6:20 pm, a wrote: On Sep 15, 6:09 pm, "Viperdoc" wrote: The thread on brakes raised a question from the past- why nitrogen in the tires of big jets and heavies? Air is around 78% nitrogen anyway, and the coefficient of expansion of the remaining 20% that's oxygen can't make that much difference in volume. Why not just use dry air? I couldn't imagine that dry air or dry nitrogen could make that much difference in corrosion, either. I seem to recall someone giving me the rationale for this a long time ago, but also seem to remember thinking it didn't make that much sense at the time. The legend is that the oxygen is reacting with the rubber. Even though compressed air has the same fraction of oxygen as does the atmosphere, the fact that it's compressed, it's been argued, increases its reactivity. I can't validate the legend. I got curious, did a quick check. The process also reduces water vapor, and N2 does not migrate through the rubber as fast as does O2, so pressure stays more predictable. So it's more consistent tire pressure, less corrosion. We bought a new Toyota and the salesman stated the tires were filled with N2 since the molecule was larger and less corrosive than air which contained O2. Now, how easy is it to find N2 around town. I can take it to the airport where the mechanic has a tank. But, all the years of owning a car, I never seem to really have a problem with tires going down that quick. At the 3K oil changes they top them off anyway. I did buy a small compressor for the hangar, but never really used it that much. I have a couple of bikes that I have to air up before each ride. Those tires really loose pressure. I brought the compressor home. -- Regards, Ross C-172F 180HP KSWI |
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