This is my first project that will actually be finished. It has a 60x1.5" barrel, and a 54x2" compression chamber. It uses a 1" solenoid sprinkler valve to control airflow, and all pipe is PVC SCH40. It will operate around 100-120 PSI normally, but should be able to handle at least 150. I need some ideas for ammo, all I can think of is D batteries and potatoes, any suggestions? I'll have pictures soon.
UPDATE: The cannon is finished, and it works great. I did forget to glue my barrel and it blew off behind my ear, giving me a good deal of shell shock. Easily fixed though. I'm still trying to find a good ammunition, and I'll have to redo my valve setup, it leaks.
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electroshockman
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theregoesthewindow
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really i thought sprinklers were only to 120 psioperate around 100-120 PSI normally, but should be able to handle at least 150
but for ammo you should just look in ammo discussion forum
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saladtossser
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use 1.25" for D sized batterys
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electroshockman
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I'm also wondering where I can get SCH80 pipes... They don't have them at home depot. I want my next gun to be a smaller but more powerful gun, what kind of design and valve should I use?
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Urban Ninja
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I would use a piston valve if you want a lot of power. I cant seem to find sprinklers in bunnings so I just make a piston.
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boilingleadbath
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"but I couldn't find sch 80 at home depot"
One cannot find most plumbing-related things at home despot. Order online, or go to a plumbing specialty store (although I'v been disapointed there too...)
"I thought sprinklers where only to 120"
Yeah, most are only rated to 120 psi. (most - toro's are rated to 150, and there are exotic ones rated to several hundred) However, that doesn't mean you can't subject them to higher pressures - plastiex009 (spudtech forums) has tested one to 420 psi. (I think)
"I thought sch 80 should be used for chambers"
Depends appon how saftey-oreinted you are. Most people don't, though... pressure rated sch 40 is good enough for most purposes.
One cannot find most plumbing-related things at home despot. Order online, or go to a plumbing specialty store (although I'v been disapointed there too...)
"I thought sprinklers where only to 120"
Yeah, most are only rated to 120 psi. (most - toro's are rated to 150, and there are exotic ones rated to several hundred) However, that doesn't mean you can't subject them to higher pressures - plastiex009 (spudtech forums) has tested one to 420 psi. (I think)
"I thought sch 80 should be used for chambers"
Depends appon how saftey-oreinted you are. Most people don't, though... pressure rated sch 40 is good enough for most purposes.
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drac
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Boilingleadbath, Plasticex tested them hydrostatically, using pressurized dish soap I believe. This is not indicitive of what will happen to the valve when using air, because it stores much more potential energy than water.
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boilingleadbath
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drac, the premis of the difference between water and air in these plumbing systems is that the air can continue to provide the same pressure after the pipe stretches when filled and this would cause a runaway positive-feedback cycle (which is false anyway), whereas the pressure provide by the water would fall drasticaly and not do so.
However, in the case of plastiex's test, he acctualy filled it until it read 420 psi on the gauge - and this mimics the situation with air.
(however, it should be noted that you can get a factor of 2 increase in pressure during a actual launch due to resonances and whatnot)
Not that this all means that it's a good idea to use 200 psi with a valve rated to 120 - that extra space between the rating and the burst pressure is called a "saftey margain" for a reason.
However, in the case of plastiex's test, he acctualy filled it until it read 420 psi on the gauge - and this mimics the situation with air.
(however, it should be noted that you can get a factor of 2 increase in pressure during a actual launch due to resonances and whatnot)
Not that this all means that it's a good idea to use 200 psi with a valve rated to 120 - that extra space between the rating and the burst pressure is called a "saftey margain" for a reason.