[SML] Cannon burst from air cannon

[Joe]

I've used ball valves created for garden hoses on manually operated air cannons before. They are indeed fast, though I never got the same boom that the pressure cap was able to create.  I looked at the PVC pipe ball valves, but they were MUCH too stiff to open with the speed that the garden hose version would operate.
When I started to use the electrically operated diaphragm valve (i.e. the sprinkler valves) They had a much greater air flow, but I would get what sounded like a tuba sounding a note rather than a boom. Actually, that was for smaller air cannons than the one I am currently designing. No tuba sound yet, but no boom from just the diaphragm valve that has 3/4" inlet/outlet.  I need something that will allow the pressure to build up after the diaphragm valve, then release at some pressure, and then reset to do it again.
I guess a completely different approach is to upgrade the audio system wattage on that side of the stage.
-Joe Dunfee
 717-203-8670 Cell
 

    On Tuesday, December 9, 2025 at 01:51:20 PM EST, Jerry Durand via Stagecraft <stagecraft at theatrical.net> wrote:  
 
  On pumpkin cannons I've seen ball valves with a way to turn it fast.  Could be as simple as a spring with a rope you cut.  If you needed electrical control, a pneumatic piston fired by a solenoid.  
 
 For the lowest of dead simple, a wheel for a handle on the valve, wrap with rope... yank.
 
 On 09-Dec-25 21:40, Joe via Stagecraft wrote:
  
 
  First, it is good that Jerry Durand reminded folks about the explosion risks with PVC pipe.  I reminded the folks working with me about that, so I at least reduced the temptation to see how loud they can make it.  I accidentally created a safety feature on my system by using a bicycle pump that was designed for higher volume and lower pressure. Taking it to 70psi was the maximum they had enough weight to pump. 
  I understand the Cv rating (resistance to air flow).  When I searched for blast valves for dust collection systems.  However, all the ones I found were ball, or knife-gate valves.  None automatically opened at a certain pressure, or reset. They were simply valves to direct the air flow to the tool being used.  I am puzzled why they called them blast valves. 
  Here is a quick sketch of how I might imagine a type of resettable high pressure valve might work.  Structurally, it is like the air outlet of your clothes dryer, or bathroom exhaust fan. However, I added a magnet to hold the flap closed until pressure exceeds its holding power. The spring loaded hinge on the flap would then close the flap, so it can be used again. 
 
 
 But, I can't find any type of air valve like this, or that is designed for releasing at a fairly high pressure (i.e. 60psi). 
  Jon, can you provide a link to the type of valve you were talking about? 
    -Joe    
  
     On Monday, December 8, 2025 at 11:39:25 PM EST, Jon Lagerquist via Stagecraft <stagecraft at theatrical.net> wrote:
 For valves I found that "blast valves" designed to clean dust collection systems do a great job. I remember them having a CV of about 50.this means they are making a big hole very fast so lots of air moves quickly, producing a good sound with or without a cap.    
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