Kaz wrote:
Geocritter wrote:
I think I’m slowly getting there. If atmospheric pressure at sea level is 14.7psi (empty tire) and the tire holds 2.37cu ft empty, then solving for X where X equals the volume of gas in the tire at 70psi using this formula:
2.37/14.7 = X/70
resulting in X = 11.3cu ft of gas (nitrogen) in the tire to achieve a pressure of 70psi.
I absolutely don’t trust my math, can someone verify?
Steve
Not exactly, but close. You're confusing "absolute" pressure (psia) with gauge pressure (psig). If you put a tire gauge on an empty tire (only atmospheric pressure), it will read 0 psi, not 14.7 psi. So, 70 psig is actually 84.7 psia. Otherwise, you are correct. By the ideal gas law, pressure is proportional to the amount of gas in the container.
Good point I hadn't thought of that. However, the only concern I have with pressure is how it affects volume. Now I know that with the smaller 50cu ft cylinder, if I needed to I could fill at least 4 deflated tires (not that I ever expect to). It appears that the small tank will easily meet my probable compressed gas needs for years. I also learned that I can exchange the cylinders at Napa auto parts stores which makes it very convenient too.
Once again, I want to thank everyone for their input.
Steve
