star guns

[paddy]

Can anyone give me some specs on a diy star gun

[MadMat]

It's not rocket science. First off, think "mini-cannon". All you need is a sturdy tube, preferably thick walled convolute (parallel) wound paper, about 4-8 inches long, fairly close in size to the stars you want to shoot. One end of this tube needs to be plugged. I have repurposed paper tubes from used consumer fireworks in a pinch. The nice thing about this is they (depending on the type of firework it was) usually come with one end already plugged and a small fuse hole near the plug as well. You can use a tube that is larger, within reason, if you make a sabot for your star. Remember, you need containment to get the lift charge to work properly. If you do this, you have to make sure the bottom of the star is exposed to the flame of the lift charge so it takes fire. I have wrapped stars in a thin strip of paper to get containment, making sure one face of the star is exposed. Then all you need to do is put a piece of fuse in the hole, add a gram or two of BP and push the star down into the tube. Make sure the bare face of the star is facing the lift charge. Anything from holding the tube upright with a couple bricks or pieces of wood to fixing it to an old broom handle can be used. Like I said it isn't rocket science, it's just a mini-mortar to test out your stars before making a shell.

Edited June 29, 2021 by MadMat

[SharkWhisperer]

As with a mortar, you want to aim around the 1:6 ratio for inner diameter to length. You can make mortars out of cardboard tubes very easily as MadMat indicated, but they won't be all that durable in the long run. In this case, his 4-8" long guns/mortars/cardboard tubes would be on the order of 3/4" to 1.25" inner diameter. It doesn't need to be exact--shorter tubes will give more spread as a mine; think of it as a shotgun blast vs longer tubes (same diameter) that have a tighter firing pattern. Cardboard is cheap and easy so easily replaced. If you look on cannonfuse.com, they sell little 3/4", 1", and 1.25" ID minimortars that are just cardboard tubes (all 6" long) that you epoxy to a plastic base and poke a fuse hole through. You'll soon be blowing the bases off of those crummy little things though. You can make your own that are much more durable with little effort. Simples.

 

I have a 4-barrel stargun made out of various diameters of iron pipe welded to a piece of iron flatstock, with IDs from about 3/8" (for single stars, or just a few) to 1.25" (for a nice 15-30g load). Never gonna wreck that thing with BP--it'll rust out first. So you can make them small or large(ish), depending on your wishes. I rarely test a single star or just a few. More fun to make a mini-mine during the testing stages. You can also use them for testing appropriately sized shell inserts during development once you've advanced to that stage. But take it slow & don't get ahead of yourself.

 

Especially important as you go up in size from the smallest diameter is that they are firmly anchored and will not tip over, they have a solid base or plug that won't be blown out, the tubing/pipe material you use is both durable and safe for your application (cardboard is perhaps safest; please don't even consider PVC piping--larger mortars are usually made from non-fragmenting HDPE or fiberglass), and take care that you don't overload your guns with lift or stars. Usually, 10% of star/projectile weight in reasonably hot granulated BP will be sufficient lift for first tests to launch your stars. Maybe 15% if your powder is not the best, or if you want a little more altitude and velocity leaving the gun. Start small and work your way up, if desired, but take care not to overload your device. A flowerpotting cardboard minimortar/stargun won't fill you with shrapnel, but it can burn you, possibly badly if you're too close. Give it some distance and don't skimp on the fuse length. And never, as with regular mortars, look down the barrel of a stargun that's in use or been recently used--don't put any body parts in front of the muzzle that you consider valuable. Even a smaller stargun can put out a very dangerous blast.

[paddy]

My neighbor just gave me ship signal cannon. It has a 1in. bore with a 8in. length. it works great. thanks for the info.you were right,i was over thinking it..

[Arthur]

A star gun is simply a tube with a sealed end, you fire a star from it to test. It can be cardboard, metal or other (fibreglass for example). People make it more complicated by having lots of tubes of different sizes together, or more expensive by machining a multi bore item from a block of metal.