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From: Steve Edwards <sedwards-at-awger.net>
Subject: Re: air canon question... T-30 !!!! [TANKS]
Date: Tue, 01 Feb 2005 22:34:14 -0500
Reply-To: tanks-at-rctankcombat.com

berin1-at-optusnet.com.au wrote:

>Aircannons are bloody dangerous, I used to use pvc 
>for a pressure chamber then blew the inside of a plywood tank chassis to bits, very 
>glad it 
>was in a wooden box. 
>  
>

note #1:   If you're going to use PVC for an air cannon, make sure it's 
pressure rated.

note #2:  When PVC fails under pressure, it doesn't just crack -- it 
explodes violently.

note #3:  Popoff valves are a very good idea.

Rule of thumb for reasonable performance from an air cannon using 
"lightweight" projectiles:

    barrel length = desired fps / 20 ( ~15" for 300fps)

    air resevoir volume = barrel volume x 2

    resevoir pressure = 80-100psi

Theoretical performance for a .69 x 12" (17.4 cal) bbl with 9cu-inch 
resevoir -at- 100psi and a .62cfm valve: 288fps

    - Steve "yes, it's another spreadsheet" Edwards