I’m trying to make a backyard artillery cannon that needs to be fairly accurate and very simple. I can’t be making trebuchets or onagers. I was thinking about using a surgical tube-powered plunger that would shoot a ball out of a length of pvc pipe. I need it to be accurate from trial to trial and dependent on the length of the plunger pull. External factors not withstanding, what are the elements that would contribute to accuracy? A close fit between the plunger, pipe, and ball diameter? A certain type of tubing? Any ideas that could help me design this thing would be much appreciated.
Sounds like you’re itching to build a rubber band gun. (I have no affiliation with them)
Like a rifle, you’ll want a long barrel. Pay attention to making the firing mechanism repeatable - if the part that actually shoves the ball out is able to slop around, you’ll have a tough time. Likewise, the ball/ammo should be a good fit to the barrel - if it’s loose, it’ll bounce around in the barrel as it takes off - this will hurt aim and distance.
Why can’t you make a small treb? At a guess, you could fling a tennis ball across a backyard with good accuracy with a 2’ throwing arm and a counterweight in the 5-10lb range. (I haven’t done the math, but trebs not much larger than this will throw tennis balls a couple hundred feet.)
You haven’t said just what your specs are. How far? What kind of ball? Why are you limited to an elastic powered tube? There are simpler alternatives, more powerful ones. If we’re talking tennis balls, what’s wrong with a racket?
Perhaps you may be interested in making a PVC Goat Cannon.
How about a potato gun, there are lots of plans on the internet. Just a warning, some folks in law enforcement may take a dim view of where you shoot these. I had both of mine seized a few years ago after I missed a tree and hit a house. :smack:
Damn you racer!
I went looking for links
The reason I want it limited to a rubber tubing power mechanism and a ball projectile (vs. a potato) is that I want to make a simple backyard artillery game that doesn’t require much (if any) setup between shots. Similar to the artillery flash games you see on the net, I simply want to set an angle and power level and let it rip towards a target. I figured I could mark the plunger at different increments to indicate power level.