Alright there's a lot here and I appreciate anyone who is taking the time to read this. Kind of in a hurry since we are experimenting with it tomorrow
We built a launcher, all fittings are brass, what other safety precautions should be taken?
What are people using as their delivery system?
What size and material expansion chamber are people using?
What are things to look out for?
So my buddy came to me with a request for a confetti cannon, and I basically built him a launcher
. After building the launcher I realized I had some concerns for the safety of the design and function. As of now it is safely stowed with no air source so no problems there
Basically I used one port on an on/off asa,
used a 1/8th to 3/8th adapter,
attached that to a 3/8 brass 1/4 turn valve,
which goes back to a 1/8th braided stainless steel hose,
which feeds into an expansion chamber,
which has another 1/8th to 3/8th adapter,
which feeds into another 3/8th brass 1/4 turn valve,
which finally feeds into the base of the launcher (3 inch pvc plug).
All this is powered by a 20 oz co2 tank.
We tested it and it works fairly well. The gas is pressurized from the on/off then cut off with the 1/4 turn valve so the gas has the ss hose and expansion chamber (AGD bike grip) to expand and is finally released with the second quarter turn valve. I figure this should keep the operating pressure of the cannon fairly low. If he needs more oomph he could always siphon it.
I've looked up the specs for brass pieces and it looks like they are suppose to with hold 1200 psi, and the ss hose itself can handle 3000psi so I'm not really worried there (should i be?).
My questions are what other safety things should I suggest? I would like to make this idiot proof.
I suggested drilling a small hole in the pvc launcher to have a hole to bleed air in case the item to be launched gets stuck in the tubing (we are using dixie cups right now, what are other people using?).
Would a burst disk be overkill?
And for later down the road after the confetti cannon has seen its use, I've read the larger the expansion chamber the bigger the shot (for some nerf rocket fun
), I don't really see an issue with using a 3/8 inch pipe to connect the two valves making a bigger expansion chamber, if the fittings can handle the 800-1000 psi of co2 (this is in a fairly controlled environment) a brass pipe should as well. Would I be grossly mistaken?
And if someone would check my calculations.
I am using
P = pressure in atmospheres, where 1 atm = 14.7 PSI at sea level
V = volume of gas in liters, where 1L = 61.02 in3
m = mass in grams of CO2
MW = molecular weight of CO2; MW = 12+32=44
R = 0.082 liter*atm/K
T = temperature in kelvins [which is 298 K at 25 C or 77 F]
24grams = 1 oz
16 oz = 1 pound
(pi*R^2)*H (R=radius, H=height)
so as it sits now (3.14*1.5in^2)*24in = the launcher has 169.56 cubic inches of volume or 2.77 liters
so to bring it to an operating pressure of roughly 120 psi or 8.163 atm
(8.163 atm)(2.77 liters) / (0.082liter*atm/K)(298K) = I would have to use 0.925 moles of co2 or 40 grams or 1.7 oz of co2
co2 exists at roughly 900psi or 14.7 atm at room temp so the volume i should be using V=nRT/P
(0.925 moles)(0.082liter*atm/K)(298K) / (14.7 atm) = 1.53 liters = which means i need an expansion chamber of roughly 94 cubic inches?
If we cut the launcher down to 12 inches that should be 47 cubic inches need to be filled with co2 to 900 psi which would mean i would need a 15 inch length of inch length of 2 inch piping. O_o that seems like a ginormous expansion chamber, what are people using? I know PVC is super unsafe, and I'm not sure how to connect a 3/8th valve to this expansion chamber.