Need help with design.

[KS-collector]

Im designing a propane powered launcher and have a few questions. My propane connection will be seperate from the gun, hooked by a hose. Its important to do it this way for my cosmetic goals. The valve was taken from a propane lantern so it will be right above the propane bottle. My main question is will I need to add a valve at the other end of the hose where it connects to the combustion chamber? Also, will it need to be steel braided hose? Or can I get away with the cheap stuff?
My goal is to have the end result look like a vietnam era artillery gun, the type you see mounted on the 2 wheeled trailers. It will be used to shoot nerf footballs across a field to simulate artilery fire during Airsoft games. Its a fairly low power application. It offer at least 100 yards of range, and no more than 300. Shot at a 45 degree angle.

[jackssmirkingrevenge]

If you're simulating artillery and care about aesthetics and realism, why not go the whole hog and make combustion cartridges?

They could be filled beforehand (I would recommend syringe metering for fast and effective results) and with a bit of thought you can make it eject the cartridges on firing just like an artillery piece, adding to the effect.

[KS-collector]

Thats cool as hell, but more complicated than I want to get. I will be breach loading it also. But im thinking of a section at the back of the barrel, on a hinge with simple latch that I can drop the shell in and close. Some pressure would escape, but Shouldnt be much. Any thoughts on this mr. Spudtech? Lol.

[KS-collector]

Btw I mean part of the barrel would open like a door. 6 inches long by 2.3-2.5 inches wide on a 2.5 inch wide barrel.

[KS-collector]

After farther review and a little time thinking, I think I will use a combustion cartridge. Just no auto election.

[ramses]

A lantern valve may not be the best choice because it probably includes a verry low pressure regulator (about 10" of water column, IIRC). A cheap propane torch is unregulated, and will allow you to reach fairly high pressure.

[KS-collector]

Meaning It would break my valve and need replaced, or break my valve ignite the propane bottle and explode my (oh so pretty) face? If I go with the pre filled shell idea, the valve and propane bottle will not be connected when it fires. Just a tire valve or something similar.

[ramses]

Meaning that you will be able to meter fuel into your chamber (or cartridge)

You will need a valve between the meter pipe and the chamber, even if you don't have it connected for firing. The tire valve could be made to work.

Essentially, you need to have a definitely separated volume of pipe between two valves (including the torch valve, if you want to use it). You fill this with propane to a give pressure using the valve near the propane tank, close that valve, and dump it into the chamber using the other valve. If you make a setup similar to Starman's Triple Thunder, you can get away with one ball valve, (but you will need quick connects).

[KS-collector]

Ah, for measuring. I got it now. I was gonna do the lazy mans way of this many seconds on the lowest open setting equals this much power. Similar to spray and pray, but slightly more accurate. But I see what your saying. Good advice. Thanks.

[Technician1002]

A lantern valve may not be the best choice because it probably includes a verry low pressure regulator (about 10" of water column, IIRC). A cheap propane torch is unregulated, and will allow you to reach fairly high pressure.

10 inch WC is the pressure of the larger BBQ regulators. Coleman lantern regulators are adjustable from zero to about 10 PSI. This permits using the jet pressure to properly form the mantle of the lantern. With lower pressure they would not form properly. Knowing this, a proper meter tube for ~10 PSI can be constructed. A tube with a volume of about 1.5 Times the volume of gas needed would work fine.

[Moonbogg]

Propane combustions aren't adjustable in power. You need to choose a power by deciding the size of the cannon. You can use a program called HGDT to do that. You might discover that your cannon blasts the round way the hell out of the playing area.

[KS-collector]

I thought with instead of the optimal 4% propane, I could use 2-3% propane I could reduce the power. Once I found the range I can work with, the angle of the cannon will dictate the target area.

[Lockednloaded]

I thought with instead of the optimal 4% propane, I could use 2-3% propane I could reduce the power. Once I found the range I can work with, the angle of the cannon will dictate the target area.

I think a much better way would be adding different flow restrictions to lower the power, such as insertable collars that can restrict to different diameters

[KS-collector]

That would work. Or if it shoots too far, drill holes along the barrel. Might have to test that effect on a small scale replica first tho. I can always make the barrel shorter too. Since it needs to look like an artillery cannon, it will have a large outer barrel for cosmetics, and the inner barrel can be as long or short as I need it to be as long as it doesnt stick out the end of my 10 ft (total length) outer barrel. The chamber/shell/cartridge will also be inside the outer barrel. But that part cant exceed 24 inches in lengt, or 7 inches wide. The smaller the better tho. A realistic size shell is best. Like 4 inches by 18, or similer.

[jackssmirkingrevenge]

im thinking of a section at the back of the barrel, on a hinge with simple latch that I can drop the shell in and close.

that sounds like it could work, I would make the cartridges out of the same pipe you are using for the barrel, and if you find a sleeve which matches the OD of this pìpe losses should be minimal.