# How do you measure the Cubic inches of a curved tube or pipe. Like a 4" PVC Elbow?

I have an air cannon and want to know how much it holds

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7 years ago
The volume is going to be approximately the length of the curve times the area of the cross-section, which in this case is a circle (pi*r^2).

The actual math involved in defining the shape, and calculating the exact volume might be kind of tricky.

If you actually have one of these pipe fittings in your possession, you could directly measure the interior volume by filling it up with something, like water, or sand.  Then you take out the water or sand, and measure it with your volume measuring tool, aka "measuring cup".
caarntedd7 years ago
7 years ago
Lol...or have him tell you to use a hall effect sensor to measure the volume

(just kidding R.M.S.)
seandogue7 years ago
A) Fill it with water.

Since a neato principle of water is that 10 ml of water equals 1 cc...
(oh gawd.,..I'm going on memory here...you'd better check the accuracy of that last statement!)

B) measure the amount of liquid from step A in ml. From ml, convert to cubic centimeters. from cc convert to cubic inches.
7 years ago
1ml = 1 cc

If you want to make calculations, try a good geometry text or find a boiler-makers or sheet metal fitters instruction book at the library and look in it for the calculations.  Otherwise, you have to try to find the center path (try averaging the inner and outer curves of the bend) and multiplying by the area of the pipe.
7 years ago
<kicks self in buttox for not remembering correctly

thanks. I figured I'd made a mistake, since my aged brain is foggy and scattered at times.

Now if I could only go back and edit my original post so as to cover up my mistake and keep that illusion of infinite wisdom from the leetle green man going... ;-)