Re: Prep for driver's school

["Nick Pashley" <NickPashley@xxxxxxxxxxxxxxxx>]

From: David Morrison <davidm3286@domain.elided>

>Check out www.powertank.com  I use a simular homemade
>setup with CO2 for offroading.  Just refill with Nitro
>instead of CO2 at a local welding supply.  BTW I use
>CO2 offroad because it generates more gas when it
>converts from a liquid...therefore more tire fills
>from a single tank.  But for the purposes of this
>discussion CO2 would probably be worse than compressed
>air for oxidizing rubber.  If I recall, Nitrogen has a
>greater change in volume than air due to temp changes,
>so after a cold night your psi will be
>lower...conversely track tires filled with N would
>gain more psi as they heat up.

>From memory:

PV=nRT        ideal gas law

P    pressure                        Pa
V    volume                        cubic metres
n    number of moles            a function of volume (dimensionless)
R    universal gas constant    8314 J/kmol/K
T    temperature                    Kelvin

P=nRT/V

A mole of gas occupies 28 litres at room temperature and pressure, therefore
that means at the same temperature, all gases occupy the same volume for the
same number of moles.

This means that P = constant * T for any gas and therefore I dont agree with
the statement above.  Indeed, air is mostly Nitrogen, hence we would not
expect to see a great difference between air and Nitrogen.

Nick Pashley

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