Supercannon II
how far down the air chamber do you set the piston
? # 2 lets say you fill the cannon loaded and psi lets say 80 psi
and you fire it there is still air left in it how much psi is it
could you leave the air in it and use a hand pump to fill it back up (with water)
for another shot
http://www.harborfreightusa.com/usa/ite ... bcatid=652
i ask because i want to use this on the river
Supercannon II ???
- SSCBen
- Posts: 6449
- Joined: Sat Mar 22, 2003 1:00 pm
Re: Supercannon II ???
You set the piston however far you want down the chamber. I usually go for a 1:1 air-water ratio but any other ratio is possible. Unless you attach the gun to an external air source (i.e. an air compressor or air tank) the pressure will drop. Higher air-water ratios (the piston pushed less far down) have more constant pressure without an external air source. Lower air-water ratios (the piston pushed far down) have more pressure drop and if the ratio is low enough not all of the water might be able to shoot out.
As for question #2, the answer is that it depends. If the temperature can be treated as relatively constant, Boyle's law can be used to calculate the pressure drop due to the volume increase. If the temperature isn't constant but there is no heat transfer, isentropic relationships can be used similarly. Reality is somewhere between the two depending on time scale; for simplicity I suggest using Boyle's law.
Usually the leftover air is exhausted. This is wasteful, yes, but the water gun was not designed to be practical. I have trouble explaining this to people who want to use it for other things. Supercannon II as is would be difficult to modify to be practical in normal water fights or river fights. The appetite for water is simply too high, so high that it's dangerous to shoot at people. A scaled down water gun much like Supercannon II but with a smaller nozzle would be more practical, but I can't see it being very practical still. Let me reiterate this: I do not recommend using Supercannon II as shown on the website page in any sort of water fight.
Leaving the air in and pumping water in makes it like a precharger/LPD water gun. This is a legitimate idea that is best applied in water guns of a different scale than Supercannon II. The pump you linked to likely is very inadequate for the job and likely will be both hard to pump and break at higher pressures. I'd suggest making a pump like the APH but using a pressure chamber like a scaled down Supercannon II if you want to go this route.
As for question #2, the answer is that it depends. If the temperature can be treated as relatively constant, Boyle's law can be used to calculate the pressure drop due to the volume increase. If the temperature isn't constant but there is no heat transfer, isentropic relationships can be used similarly. Reality is somewhere between the two depending on time scale; for simplicity I suggest using Boyle's law.
Usually the leftover air is exhausted. This is wasteful, yes, but the water gun was not designed to be practical. I have trouble explaining this to people who want to use it for other things. Supercannon II as is would be difficult to modify to be practical in normal water fights or river fights. The appetite for water is simply too high, so high that it's dangerous to shoot at people. A scaled down water gun much like Supercannon II but with a smaller nozzle would be more practical, but I can't see it being very practical still. Let me reiterate this: I do not recommend using Supercannon II as shown on the website page in any sort of water fight.
Leaving the air in and pumping water in makes it like a precharger/LPD water gun. This is a legitimate idea that is best applied in water guns of a different scale than Supercannon II. The pump you linked to likely is very inadequate for the job and likely will be both hard to pump and break at higher pressures. I'd suggest making a pump like the APH but using a pressure chamber like a scaled down Supercannon II if you want to go this route.
- Drenchenator
- Posts: 807
- Joined: Fri Jun 18, 2004 12:00 pm
Re: Supercannon II ???
If you want a river gun, I suggest the Sac American one or the Waterzooka; either is better for use on a river because they need no pressure or fancy loading systems.
The Drenchenator, also known as Lt. Col. Drench.
- Silence
- Posts: 3825
- Joined: Sun Apr 09, 2006 9:01 pm
Re: Supercannon II ???
Plus you'll get decent range with the right nozzle, since there aren't any valves to restrict the flow.Drenchenator wrote:If you want a river gun, I suggest the Sac American one or the Waterzooka; either is better for use on a river because they need no pressure or fancy loading systems.
Most of the other designs on the website are more conventional: they're safe to use in a water war (if that's your goal) and they were designed with water pumps (and not air pumps) in mind.
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- Posts: 3
- Joined: Fri Jul 20, 2007 1:57 am
Re: Supercannon II ???
yes i have made 3 of the sac kind 2' pvc and get 40'-50' out of them