Why nitrogen?

Peter Dohm wrote:
The only difference that would make nitrogen seen really beneficial to me
would be in the case of an aircraft which is kept hangared and seldom
operated. Then, if the tire threads last a number of years, and the tires
are sheltered from UV radiation, the inert nature of the nitrogen could be
usefull.


In theory, perhaps. In practice, tires oxidize from the outside as well as
the inside. I've noticed that every time I've bought expensive, long-life
tires, they have to be chucked because the sidewalls are rotting, even though
the tread is still good. It's not just air, but pollutants (particularly in
the cities). Ozone, a common urban pollutant, is particularly bad for tires.

John Galban=====N4BQ (PA28-180)

--
Message posted via AviationKB.com
http://www.aviationkb.com/Uwe/Forums...ation/200809/1

On Sep 15, 3:09*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.

I just got new tires for my wife's car. They're usnig Nitrogen too.
They put green caps on the valve steam to show its not air.

-Robert

Everything posted so far leads me to believe that dry air should work just
as well as dry nitrogen.

At least it's about aviation.

Nomen Nescio wrote in
:

-----BEGIN PGP SIGNED MESSAGE-----

From: "Viperdoc"

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?

1) It's AVIATION
2) Nitrogen is more expensive


Asked a grease monkey friend there a few minutes ago.
He says that O2 under pressure is considerably more reactive than it is at
normal atmospheric pressures. So the main reason is to prevent oxidation of
tires and seals. A secondary consideation is detonation in oleos.

Bertie

Bertie:

I find this hard to swallow, and I doubt that oxygen (at 20% of air),
regardless of pressure, is going to cause a detonation in an oleo. Just like
in a tire, the percentage of oxygen remains the same, so its ability to
support combustion also remains the same. Now, the increased oxygen pressure
might slightly increase the risk of corrosion, but we are not talking orders
of magnitude higher compared to ambient. At least this is my understanding
as I recall from being a chemistry undergrad and grad student.

The more I hear about this, the more I think it's an old wive's tale.

Anway, what did you think of Anthony's claim"it's not me?" What a moron.

"Viperdoc" wrote in
:

Bertie:

I find this hard to swallow, and I doubt that oxygen (at 20% of air),
regardless of pressure, is going to cause a detonation in an oleo.

Our oleos are a little more, eh, enthusiastic shall we say, than the
oleo on a cherokee! Thumping a hypothetical airplane that weighs, say
500,000 lbs onto an oleo strut of about a foot in dia at, maybe over
1,000 fpm rate of descent is going to get things pretty exciting inside
the strut.I have no idea what the compression ratio is in there, but
it's got to be reasonably high.
I do come across one grease monkey who has answers galore. Anything he
doesn't know he finds out for me the next time I'm through. He's just
one of these guys with an insatiable curiosity about all things
mechanical..

Just like in a tire, the percentage of oxygen remains the same, so its
ability to support combustion also remains the same.


Now, the
increased oxygen pressure might slightly increase the risk of
corrosion, but we are not talking orders of magnitude higher compared
to ambient. At least this is my understanding as I recall from being a
chemistry undergrad and grad student.

Apparenlty, the increased prsssure makes O2 much more aggresive so the
effect is not slight, but in any case, I'm only telling you what my bud
said and he's quality control for a big airline.

The more I hear about this, the more I think it's an old wive's tale.

Anway, what did you think of Anthony's claim"it's not me?" What a
moron.

Oh yeh. Couldn't care less if it's him or not, to be honest!


Bertie

"Robert M. Gary" wrote in message
...
I just got new tires for my wife's car. They're usnig Nitrogen too.
They put green caps on the valve steam to show its not air.

Yes, those green caps have proven to be much better at keeping the snake oil
inside the tire where it belongs. Also, I have never once seen a car with green
valve stem caps get attacked by elephants, (but that is just anecdotal evidence
and your experience may vary).


--
Vaughn

.................................................. .......
Nothing personal, but if you are posting through Google Groups I may not receive
your message. Google refuses to control the flood of spam messages originating
in their system, so on any given day I may or may not have Google blocked. Try
a real NNTP server & news reader program and you will never go back. All you
need is access to an NNTP server (AKA "news server") and a news reader program.
You probably already have a news reader program in your computer (Hint: Outlook
Express). Assuming that your Usenet needs are modest, use
http://news.aioe.org/ for free and/or http://www.teranews.com/ for a one-time
$3.95 setup fee.
.................................................. ........

Will poofread for food.

Vaughn Simon wrote:
"Robert M. Gary" wrote in message
...
I just got new tires for my wife's car. They're usnig Nitrogen too.
They put green caps on the valve steam to show its not air.

Yes, those green caps have proven to be much better at keeping the snake oil
inside the tire where it belongs.

On a side note...

- I learned a few years back that the CAP on a Schrader valve (the
common tire valve) is the PRIMARY seal. No cap, no promise of a good
seal from the valve.

- Green valves on bicycles mean the tire is "Slimed", and has a fiber /
goop sealant.

- Nitrogen DOES leak less than air, and is dryer than most compressed
air. While it isn't worth $59.95, some really good tire shops, and
places like Costco, provide it for free.

CO2, commonly used to quickly repair bicycle flats on the road, leaks
much faster than air!

- Anyone who's ever had an ice chunk in a tire can appreciate a "drier"
fill...

"JGalban via AviationKB.com" u32749@uwe wrote in message
news:8a4950eac1beb@uwe...
Peter Dohm wrote:
The only difference that would make nitrogen seen really beneficial to me
would be in the case of an aircraft which is kept hangared and seldom
operated. Then, if the tire threads last a number of years, and the tires
are sheltered from UV radiation, the inert nature of the nitrogen could be
usefull.


In theory, perhaps. In practice, tires oxidize from the outside as well
as
the inside. I've noticed that every time I've bought expensive, long-life
tires, they have to be chucked because the sidewalls are rotting, even
though
the tread is still good. It's not just air, but pollutants (particularly
in
the cities). Ozone, a common urban pollutant, is particularly bad for
tires.

John Galban=====N4BQ (PA28-180)

Ordinarily, I would just let this slide; but since the greenies have decided
that CO2 (which is nature's means of recycling oxygen) and O3 (which is
nature's cleanser of the atmosphere) are "pollutants" according to the
strange reasoning of their adled brains, I feel compelled to point out that
I suggested that the aircraft would be sheltered in a hangar--which would
protect the outsides of the tires from part of the damage. They still won't
last until the treads wear out, but it will help.

Peter

"Bertie the Bunyip" wrote in message
...
"Viperdoc" wrote in
:


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"


Mm, nice.

You heard about this?

http://www.gadling.com/2007/12/16/qu...-oxygen-tanks-
with-nitrogen/

Sounds worse than it was, but still....

Bertie

It appears that they were lucky and the oxygen was'nt needed; but it does
remind me of some of the speculation surrunding the Paine Stewart case. Two
hypotheses around my local airport were that 1) the tank was inadvertantly
filled with nitrogen or 2) that someone misread the labeling on the
regulator on/off handle--which is counterintuitively labeled with "on" or
"off" and arrows pointing which direction to turn the knob for the desired
result. I don't recall whether the case was ever fully resolved; but a lot
of pilots found a couple of areas worthy of their maximum vigilance!

Peter