In article , LM wrote:
On Tue, 6 Apr 2010 17:00:00 -0400, Stormin Mormon wrote:

At 150 PSI, they would be useful as expansion tanks for air
compressors.

Interesting idea!

1. Buy copper pipe
2. Drill ten holes 2 inches apart in the steel pipe for the threaded bolts
3. Tap the ten holes in the galvanized steel pipe for the threaded bolts
3. Drill an axial hole through the center of ten threaded bolts
4. Drill a hole through the center of ten soda caps for the threaded bolts
5. Screw the ten threaded bolts into the caps and then into the steel pipe
6. Cap one end of the steel pipe & place a chuck on the other end
7. Chuck the other end of the steel pipe onto your CO2 regulator hose
6. Screw ten 2 liter soda bottles onto the ten caps bolted to the pipe
7. Turn on the C02 gas and pressurize the twenty liters to 150psi
8. Remove the chuck
9. You now have 20 liters of 150psi portable C02!

QUESTION:
How many liters of gas does a typical automotive car tire take anyway?

Eyeball-estimate - roughly a torus that on largish side has a
tubular cross section whose diameter is 20 cm, and with a 50 cm diameter
of the tube's "centerline". Volume of such a "largish tire" would in
cubic centimeters be 20 squared times pi/4 tomes 50 times pi, or 49,348
cubic centimeters. Divide by 1,000 to get liters - about 49.

That does sound to me large for a tire, maybe about right for a tire for
a large SUV. Also, most car and SUV tires are not inflated past 36 PSI.
50 liters at 36 PSI, if compressed to 150 PSI, takes up 12 liters.

One more thing - CO2 has slightly different dynamics in compressibility
than air does, due to its lower specific heat ratio. CO2 at 32 PSI in a
14 PSI atmosphere has the same "stiffness" as air would have at about 28.5
PSI. The vehicle's ride and "road feel" and how much the tires get mashed
by bumps and potholes would be as if the tires were underinflated about
11%. The specific heat ratio of a gas alters its compressibility when it
is compressed or expanded quickly enough to have its temperature respond
to the change in pressure rather than being held by heat conduction to the
ambient temperature.

However, the wear rate and wear pattern would be determined more by the
pressure alone. Compensating with a higher pressure would concentrate the
wear towards the "centerline" of the tread.

Also, pressure alone contributes to much of the stress that parts of the
tire must face and the shape of the tire and its contact patch when it is
supporting a load. This affects its traction on wet roadways at
higher speeds. These factors can severely limit use of higher pressure
just because the gas is more compressible in a "dynamic sense".

- Don Klipstein )