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Building my first pneumatic cannon today. I've built a couple combustion ones before.
Using PN12 (178psi) piping, 2 meter (6.5 feet) 50mm chamber (2.12 internal diameter) split into two lengths joined by a tee. So it's two 3.25ft chambers side by side.
I thought about making a piston valve, but decided on a ball valve I found. Its internal diameter is also 2.12 inches and it can be opened in a very very short time because the ball is very well lubricated.
As for the barrel: I bought the wrong/too much pipe initally so I will have two barrels. One 1.69in internal about 72in long, and a 2.12in internal about 72in too.
I think the ball valve I have for this project will be good, because it opens so fast. Also, when using a solenoid, you have to shrink the diameter of the pipe to make it fit the valve. With my chamber system, there won't be any point that is more narrow that 2.12". The entire system will be 2.12" diameter is I used the 2.12" barrel.
Not going to paint this cannon or anything, cause it'll just be used by me.
GGDT predicts 380fps for a 100g projectile.
I'll post pics tonight.
A ball valve may be fast relative to other ball valves, but that time is an eternity in spudgun terms. Your projectile might be in the barrel for 20 ms - the ball valve will take about 100-200 ms to open.
Using a powerful spring to open it should give you a lot more power - if you can that's the best idea for extra power.
Other than that, it sounds like a nice build.
That 1.69 ID barrel means you can shoot golf balls. With a 6 foot barrel, I'm guessing you'll be able to lob one of those pretty far.
4 more hours till it's been 24 hours since I glued.
Not OK to use it at 20, right? Even if only filling to 50psi (rated to 178).
There is nothing *magical* that will occur at 24 hours after glueing. I typically let my cannons dry over night, and will shoot them at as high as my compressor can go. As of now, the glue being not cured is not of your worries anymore.
Got it to 30psi for first test, then my freakin' pump broke.
I should have known better than to buy it from The Warehouse (like an New Zealand version of Walmart).
Your in NZ?wow your like the fourth person on these forums incl me from NZ!
hey what city you in?yeah you should of known better to buy it from the warehouse,you can get 21litre 2HP 115psi air comps for about $90NZD from supercheap.
EDIT:have you found any solenoid/sprinkler valves?and if you have where you get them?ive only seen one on trademe and its shite.
I just Mickey-moused something together, using a hand pump weed sprayer thing, it only goes to 40psi before the relieve valve on the tank pops though.
I saw a $120, 120psi 24l compressor at The Warehouse while I was in there too, but it didn't include a hose or fittings or anything. I'm in Masterton, we have a Super Cheap here, I'll check it out tomorrow. Does it come with a hose/tyre filler? If not, how much are they there if you know?
As for solenoid valves... I got quoted ridiculous prices from MasterTrade. They were industrial strength valves though, not for lawn/garden irrigation.
Even at 40psi, I am very very impressed with the performance. I took some lemons (half ripe) off our tree, pressurized to 40psi and fired at a brick wall, there was nothing but a wet patch and bits of lemon strewn everywhere.
I also tried a vertical fire of a 50g lemon at 40psi. GGDT says it should have gone about 110m up, it was MUCH more than that.
Water is very cool too, I've got some ice freezing in barrel pipe offcuts now
Any idea as to the legality of air cannons here? My father is in the police (and an avid gun fanatic) he says they would come into the category of air powered BB guns, so you either need to be over 18 or have a firearms license. Have you hear otherwise?
Combustion cannons ALWAYS require a firearms license.
Find attached a GGDT model (well, I would _like_ to attach it, but apparently .gdt files can't be uploaded).
So, find it here: http://download.yousendit.com/E7341D6345FB466F it will only be there for 7 days though.
EDIT: just did some more test firings. 50g lemon + 40psi = 218 paces @ 90cm per pace = 197m. GGDT predicts 163m for those values (with the 'max range' option ticked), so it was kinda off. Though my measurement was AFTER the roll of the projectile (no idea how much that was). I think my valve opening time is wrong though, there isn't much I can do but estimate. How fast it opens really depends on the temperature too. When it's hot, it can be very hard to open (well, hard compared to when it is cold).
Cant wait too see it.Is the barrel 50mm PN12?or 40mm PN12?Nice job mate from across the Tasman sea.
Barrel is 40mm PN12.
It screws directly into the ball valve though. I've got the pipe, I just need to buy another threaded joiner then I'll have a 50mm barrel too (PN12).
40psi + lemon + brick wall = http://img297.imageshack.us/img297/4471/picture1rl0.jpg (battery is there for scale)
Once I can find some AA batteries for my camera (above was with webcam) I'll take some photos. It's not much to look at though.
1:dont buy that air comp from the warehouse
2:supercheap may sell some air comps with the hose and stuff but i bought a coil hose and fittings for it to attach it to either a schrader or a quick connect for under $30.
3:combustions are illegal put pneumatics are classed as air rifles and require you to either be over 18 or be over 16 with a gun license.
The cheapest compressor they had was $125. Another $40 go you a hose, lots of disconnects, fillers etc etc.
Works well. I only get one shot per charge on the compressor though.
Took my cannon upto 60psi, loaded a kiwifruit in (with wadding) and BANG, the kiwifruit was vaporized upon leaving the barrel.
I'm looking for a perfect ammunition. Non-produce, fits perfectly. Any ideas? 1.75" ID.
I decided to paint today.
Bought some enamel spray paint, forrest green.
I know it's going to flake off, but it won't look as bad as mottled grey.
EDIT: my, it looks like complete and utter crap. For one, I ran out of paint after finished 7/8ths, but when I lifted the gun off the news paper, it took a lot of the paint with it.
oh well, atleast is still functions. I dont have to worry about the paint corroding the plastic? it was just normal spraypaint.
yeah it took 4 cans of enamel to paint my dam buster,and for the 1.75" barrel you could use a golf ball with wadding or a bouncy ball.
for the air comp i got mine from my dads mitre10 and he sells them cheap but i got the air hose stuff from www.ashair.com
Nut meets paint can at ~400kph.
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