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| Uncle Al |
 Posted: Fri Sep 17, 2004 11:15 am |
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Guest
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Helmut Wabnig wrote:
[quote:3d042e9817]
Red rubber stoppers on the valves are simply cute!
Google "gas filling tires" 45000 hits
If you have enough time you may want to read the arguments of the
salesmen, this time we want to concentrate on only one main argument,
which appears everywhere like the Amen in the prayer.
As introduction we cite a (German) web page:
Nitrogen as gas filling
LEAFLET for customers
Advantages of tires filled with Nitrogen (N2)
optimized road behaviour, Nitrogen does not expand, therfore constant
tire pressure, comfortable driving because no increased pressure as
with O2 / CO2 less rolling resistance causes lower gas consumption
increased lifetime of the tire.....
So far the main topic, a side theme may be mentioned:
no pressure loss in the tire
Oxygen is responsible because Oxygen has been exerted from the tire
and Nitrogen has been applied and no pressure loss is present
[snip to the conclusion][/quote:3d042e9817]
Thermal expansion of tire fill gas is identical for all chemical
compositions within Ideal Gas Law vs. van der Walls equation
solutions. Fill gas diffusion rate through tires is inversely
proportional to the square root of molecular weight. Exceptions are
for chemical interactions like solvation - CO2 often has anomalously
high permeation rates; a thin barrier layer of polar poly(vinyl
alcohol) is remarkably good for containing non-polar helium (Hi-Float
for helium-filled rubber balloons).
The perfect tire fill would then be 1.1 atmospheres of air (to be on
the safe side re back diffusion) and the rest of the pressurization as
a high molecular weight inert gas like Freon-12 (problems with
Minnesota winters) or SF6. This is patented for tennis balls that
never go flat. You would check tire pressure maybe once/year.
There are acoustic problems. In improved tennis balls the metallic
"ping!" was muted by adding a bit of foam fluff inside. One imagines
tires likewise before being mounted on the rim.
All this wonderful improvement and added safety was killed by
Enviro-whiners screaming "Greennhouse Effect!" Their methane farts
don't absorb infrared.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
http://www.mazepath.com/uncleal/qz.pdf |
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| Mike B |
| Posted: Sat Sep 18, 2004 8:48 am |
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Seems like there is not enough of the gas material anyway to cause a great
difference.
Helium would allow better heat transfer, but heat is generated in the walls
of the tire, so that would not seem to help. No enough O2 to be concerned
about in a fire.
Fill them up with mostly Water, now that would be a difference.
Actually you get a lot of water and water vapor in the air you fill your
tires up with, at the gas station, most of the driers don't work after
compression of the air due to lack of maintance.
Sulfur Hexafluoride sounds really nasty, reactive? They use it for cooling
burried powerlines. |
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| Steven B. Harris |
| Posted: Sat Sep 18, 2004 1:57 pm |
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Joined: 25 Jan 2004
Posts: 1696
Location: California
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"Mike B" <bozonamike@yahoo.com> wrote in message news:<2r305vF15snj1U1@uni-berlin.de>...
[quote:aa70b482f3]Seems like there is not enough of the gas material anyway to cause a great
difference.
Helium would allow better heat transfer, but heat is generated in the walls
of the tire, so that would not seem to help. No enough O2 to be concerned
about in a fire.
Fill them up with mostly Water, now that would be a difference.
Actually you get a lot of water and water vapor in the air you fill your
tires up with, at the gas station, most of the driers don't work after
compression of the air due to lack of maintance.
Sulfur Hexafluoride sounds really nasty, reactive? They use it for cooling
burried powerlines.
[/quote:aa70b482f3]
COMMENT:
Don't confuse SF6 with UF6 which *is* really nasty (due to a
propensity to equilibrate to a little bit of UF4 + F2).
SF6 is not not "really nasty," but rather more or less inert. You can
safely breathe it in and 80% mix with O2, just like Freons. You
wouldn't want to do this at high pressure in diving (due to anesthetic
effect and also some odd membrane effects), but at normal pressures
it's benign.
Contrary to comments of a previous poster, SF6 is not--- repeat NOT---
harmful to the ozone layer. Completely perfluorinated compounds, and
compounds of C,F, and H with no Cl or Br in general don't harm ozone,
and SF6 is no exception. CFCs and BFCs containing flourine, and either
chlorine or bromine all cause ozone damage, but it's the Cl. and Br.
free radicals that do it, not the fluorine. Fluorine doesn't form such
radicals in quanties to be dangerous to ozone-- it's too reactive.
Some of the confusion is due to the fact that SF6 and other
perfluorocarbons turn out to be very potent greenhouse gases-- even
more than methane. But whether or not they'll ever be present in the
atmosphere in quantities to add anything significant to the effect of
CO2 and CH4, is questionable. Greenhouse gases like CF4 (Freon 14)
have as long a half life in the atmosphere as ozone-toxic Freon 12
(CF2Cl2), so a buildup there might pose a greenhouse threat over a
very, very long time. I don't know about SF6.
SBH |
_________________
You can email me at sbharris@ix.RETICULATEDOBJECTcom. Find the synonym. |
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