Please help me do the math...

[icuppu]

Even though you are right, lets do it simpler for the next guy who reads your post. To begin, there are 12 inches in a foot, so if we multiply a foot in three dimensions we get a cubic foot (12 x 12 x 12 = 12^3 = 1,728 cubic inches). Next, there are approximately 14.504 psi in Barometric Atmospheric Pressure called a Bar. So, the key is to convert the questionable cubic inches, in this case it is 48 in^3, and to convert the pressure into Bars, or the compression factor, in this case 3,000 psi.So, we can multiply two fractions, or combine the numerals together into one fraction, or... the sky is the limit. 



This is what it would look like and would be recognizable:

(45/12^3) x (3,000/14.504) = 5.75 ft.^3; this avoids the repeating periodic decimals that go on forever and clutters the mind from thinking logically.

Now, there are 2.54 cm in one inch, and if we multiply it by itself three times we get a volume called cubic centimeters per cubic inch and this is what it looks like:

2.54 x 2.54 x 2.54 = 2.54^3 = 16.387064 cm^3, or "cc", which is used for liquid measures, I like cm^3, which is for volumes; even though they look the same in number.

Now the math process follows:

215 cc / 2.54^3 / 12^3 x 3,000 psi / 14.504 = 1.57 ft.^3; this way the numbers look familiar and make sense from where they came and are going.

The easy part: 5.75 ft.^3 / 1.57 ft.^3 = 55 unit less, but in this case, fills.

The thing to do is to set up a table with all the constants to where you just input your variables.

Cool question.

 

[icuppu]

Even though you are right, lets do it simpler for the next guy who reads your post.

To begin, there are 12 inches in a foot, so if we multiply a foot , or twelve inches, in three dimensions we get a cubic foot (12 x 12 x 12 = 12^3 = 1,728 cubic inches).

Next, there are approximately 14.504 psi in Barometric Atmospheric Pressure called a Bar. So, the key is to convert the questionable cubic inches, in this case it is 48 in^3, and to convert the pressure (psi) into Bars, or the compression factor, in this case 3,000 psi to 310 Bar.So, we can multiply two fractions, or combine the numerals together into one fraction, or... the sky is the limit. 

This is what it would look like and would be recognizable as entered into a calculator, parenthesis are for emphasis and clarity of grouping:

(45/12^3) x (3,000/14.504) = 5.75 ft.^3; this avoids the repeating periodic decimals that go on forever and clutters the mind from thinking logically.

Now follows, there are 2.54 cm in one inch (by international law), and if we multiply it by itself three times we get a volume called cubic centimeters per cubic inch and this is what it looks like:

2.54 x 2.54 x 2.54 = 2.54^3 = 16.387064 cm^3, or "cc", which is used for liquid measures, I like cm^3, which is for volumes; even though they look the same in number, (a gallon of beer is not the same as a gallon of sand; even though, they are the same volume).

Now the math process follows:

215 cc / 2.54^3 / 12^3 x 3,000 psi / 14.504 = 1.57 ft.^3; this way the numbers look familiar and make sense from where they came and are going.

The easy part: 5.75 ft.^3 / 1.57 ft.^3 = 55 unit less, but in this case, fills.

The thing to do is to set up a table with all the constants to where you just input your variables. 

Lastly, this is what the whole enchilada would look like as input into a calculator:

[(45/12^3) x (3,000/14.504) ] / [215 cc / 2.54^3 / 12^3 x 3,000 psi / 14.504] = 55 frills!

In closing, as to the SBCA, or SCUBA tanks, just as with air guns, a single variable does not mean much. The 45 minute is for a sedentary fire fighter watching his buddies battle a flaming building and rescuing a baby from the second floor. The rescuing firefighters will be lucky to have 20 minutes of air from the 45 minute bottle. Retired fire fighter. As to the SCUBA tanks; for example, an 80 in^3 aluminum tank filled to 3,000 psi will last on average 60 minutes on the surface and for each atmosphere, or 33 foot submersion, the pressure increases and cuts the time by that amount, so at 33 feet, the tank will only last 30 minutes, and at 66 feet, 20 minutes, and 99 feet, 15 minutes, deeper you run into nitrogen narcosis and even deeper your air becomes toxic and even deeper your air becomes poisonous. If you rise more than 3 feet while holding your breath with compressed air, you run the risk of blowing out your lung alveoli and you will drown with your own blood. You also cannot rise faster than one foot per second, or you risk nitrogen bubbles in the joints which have been known to incapacitate divers to the point of drowning unless taken to a hyperbaric chamber, or even better, back down deeper to come up and decompress. The other variable is how hard you are breathing, working, swimming, struggling, etc.Retired, Dive Rescue Specialist because air guns are safer.. My air gun shoots fast, shoots a group through a hole, and it looks bada$$. Sound familiar?

Numbers do'nt lie, but you can lie with numbers, and the laws of physics are not just really good ideas.

Cool question.

 

[kmd1984]

Wow, thanks for the input! I enjoyed the read!



Kmd