Short and Fat/Long and Thin? Pony Tank Preferences

[DA Aquamaster]

DA Aquamaster,
After re-reading, I understand why the math is so straighforward for a 30. Could you please tell me how to figure the same for a 40? Thanks. Jim

In either case you use a ratio of the tank pressure when full over the tank volume when full which is equal to the volume of the tank over the pressure of the tank at any given pressure.

Volume (full)/Pressure (full) = Volume/pressure

With a 40 you would start with the tank holding 40 cu ft at 3000 psi.

Since you know the current tank pressure you are solving for the current volume:

40/3000 = X/current tank pressure

multiple both sides by the current tank pressure to isolate the X. which gives you your formula:.

(40)(current tank pressure)/3000 = X

So if you have 2200 psi in the tank:

(40 x 2200)/3000 = 29.3 cu ft.

But...that is way more complicated than it has to be. Instead you can get half of the division out of the way up front, do it once and never have to do it again.

Divide 3000 psi by 40 cu ft and you get 75 psi/cu ft which will then be a constant for your 40 cu ft tank.

So if you have 2200 psi, you just divide 2200 by 75 to get the same 29.3 cu ft.

This is where the difference between the math required with a 30 and 40 is most evident as with a 30 you are dividing by a constant of 100 rather than a constant of 75 and just have to move a decimal point to get the answer.

 

[jim T.]

DA Aquamaster,
Thanks so much for your explanation! I really appreciate this and ALL of the succinct responses you've given me. (Everyone else here, as well.) I'm still weighing pony tank sizes.

I did have one further "clarification" question regarding my R 190 reg. question on the regs. forum. I'll PM you, hoping that'll be ok.

Jim T.

 

[bgi]

After slinging a luxfer and catalina 30, I prefer the catalina. It's imperceptibly larger in diameter (3/8"), but about 2" shorter, so it doesn't get in the way as much FOR ME.