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Questions On Tank Pressure


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#1 monkey with a nf

monkey with a nf

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Posted 01 May 2007 - 07:54 PM

I am attempting to build a magazine-fed pneumatic homemade, similar to(it actually started as) Flaming Hilt's version of the SOBR-P. As such, I am basing the tank off of an AT3K tank. I found that for every 1 cubic inch of airtank volume, something pressurized the same as an AT3K with four pumps has about 3.32 cubic inches of air. I have no idea how this translates to PSI, though I assume that it is below the limit of schedule 40 PVC.

When I run through the calculations, I find that the ideal length of 3/4" PVC for the optimum air volume for 12" 17/36" brass is about 5", but at the pressure I plan to use it should be about 1.5". Therefore, this is my planned tank volume (I'm using 3/4" because this is what I'm using as a valve). Does this all seem right? I'm trying to both have this get the approximate range and accuracy of a singled AT3K, and not have it blow up in my hands.
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QUOTE(Pineapple @ Sep 12 2007, 03:13 PM) View Post

For maximum efficiency?


1. Pump up. Count how many pumps.

2. Keep going until you hear a loud "bang".

3. Subtract one pump from the total. Rebuild your air bladder.


There you go.

#2 CaptainSlug

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Posted 01 May 2007 - 08:10 PM

PSI is a measure of both force and of volume. Tanks can be measured by volumetric capacity combined with maximum pressure rating to determine their filled capacity. How to do that is beyond me (I hate math) and isn't terribly important for what you are trying to do anyways.

Keep in mind that even the most robust manual bike pump imaginable is incapable of filling any tank beyond 70PSI. Which is still well below the maximum pressure rating of PVC pipe (120PSI). Even the strongest person I can imagine is not capable of physically overcoming that pressure level by using a standing pump.

A pressure gauge is still a good idea and you can by them for as little as $6 in the pressure range you're going to be working with.

Edited by CaptainSlug, 01 May 2007 - 08:12 PM.

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