T-Shirt cannon pnuematic set ups

[Cody Carey]

Originally Posted by vivek16

Actually, 120 psi is a lot. There is a reason FIRST has us use only 60 psi. If you do make a pvc gun, please, please make sure that you don't use pvc for the air storage or charging.

Wrapping the tube (barrel) in duct tape a lot and putting a bigger tube around it makes it a little safer.

be safe, Vivek

When originally designing our T-shirt cannon, We looked at the pressure ratings listed in the Engineering toolbox.( http://www.engineeringtoolbox.com/pv...res-d_796.html )

It clearly lists that the maximum allowable operating pressure for 3" schedule 40 (which is what we used) is 158 Psi, and the minimum bursting pressure is 840 psi. Considering that that is 38 psi above what the exhaust valve on the pump we were using is set to, combined with the fact that we had the tank encased in a plexiglass shield and we wouldn't be operating it in temperatures above 140F (thank God)... I'd say we were perfectly within the confines of what would be considered "safe".

As for wrapping the barrel and/or tank in Duct tape, and placing it in a larger section of pipe, that would not only make it a little safer, it would virtually eliminate any safety hazard at all. No shrapnel means no major injuries... and the chances of the larger pipe bursting (if it is sealed) are minimal as well, because the largetr pipe would be exposed to a much smaller pressure PSI than the little one was.

As for the reasoning behind FIRST having the teams limited to 60 PSI, I doubt it has to do with the bursting pressures of PVC,but can more likely be attributed to them being overly stringent with their safety regulations... but as there have been no major pneumatic related injuries that I know of thus far in the program, I'd be an idiot to argue with their reasoning.

I'd say that as long as you have the tank well guarded from any shock, and you don't abuse the thing, you're safe to use PVC in a 120 PSI system.