Category Archives: PNEUMATICS

Range Testing Theory for Spud Guns (Or any Projectile)

Posted by on October 7, 2011 No comments

Going through my files, I came across this discussion that I wrote about the science behind spud guns (For actual guns that I’ve built, check out this mini-bolt-action model or this double-barrel pneumatic air cannon). If you’re interested in calculating the range of a projectile thrower of any kind, this discussion may be of some use to you.  I don’t recommend building a spud gun, and this whole discussing was written while I was still in college, so keep that in mind (also, where you see: “X^2″ or “V0^2″ etc that means X or whatever variable squared):

Spud Gun Testing and Ballistics

One thing that applies to both pneumatic and combustion spud guns is that the range of your cannon is related to the muzzle velocity or velocity at the end of the barrel. When a potato –or your choice of projectiles- is shot from your cannon, it has a certain velocity. This gives the potato some kinetic energy which hurls it away from the earth. Unfortunately, Read more »

The Double-barrel Pneumatic Air Cannon

Posted by on May 8, 2011 9 comments

After restoring my mine bolt-action potato cannon, I decided that the double-barrel cannon that resided in my garage would be interesting to get working again.  It hadn’t been fired in several years, and one of the valves no longer worked.  Additionally, it leaked badly, so I had my work cut out for me.  Here’s a picture of the gun partially restored before any sort of leak testing or firing (Read on for another video at the end):

double barrel PAC on ground

The principle behind this gun, or most pneumatic air cannons, Read more »

The Miniature Bolt-Action Pneumatic Potato Gun: Part 3 – Putting Everything Together

Posted by on April 20, 2011 No comments

So I’ve gone over the mechanical design of the bolt mechanism as well as the pneumatics involved.  However, I didn’t really go over putting everything together.  This device was actually constructed a few years ago and sat around in my garage since then.  It’s been a very popular post so far, so I’m glad I dug it up.

mini pneumatic potato cannon being assembledBefore recently, all the components just sat around together and were fired that way.  To make it really work, I needed some sort of stock to hold everything together.  After some thought, I used a 9 inch piece of 2 x 4 drilled out with hole saws to accommodate the different sizes of pipe.  I also cut a hole in the side to allow for better gripping.

Besides the grip hole, Read more »

The Miniature Bolt-Action Pneumatic Potato Gun – Part 2: Pneumatics

Posted by on April 10, 2011 4 comments

As mentioned in the last post, this may not be safe; I don’t recommend building this device.

pneumatics/ trigger viewBolt action rifles, as well as bolt-action potato guns can be loaded much faster than their muzzle-loaded counterparts.  In this case, the potato can be pre-cut and doesn’t have to be stuffed down the muzzle to a pre-determined depth.  One just has to insert the projectile into the breech as explained in this post, lock it into position, and fire.

Breech loading may seem interesting on it’s own merit, but it could still take a full minute or longer to fully charge your air reservoir to power the projectile down the barrel.  Without improved pneumatics, you still have a pretty slow process.  To speed this process up and give you several good shots between air charges Read more »

The Miniature Bolt-Action Pneumatic Potato Gun – Part 1: The bolt

Posted by on April 7, 2011 26 comments

I don’t recommend trying this and can’t guarantee that it’s safe.  PVC pipe is generally not rated for holding air pressure.

Years ago, I made a cannon that shot grapes, tater-tots, or cut potatoes with a 1/2 inch length of PVC pipe.  The innovative part of this was that it used a bolt-action mechanism to open and close the breech.  This meant that instead of having to stuff the projectile down the muzzle of the “gun” into the “chamber”, it could simply be placed in the breech and closed.  Bolt-action rifles were, of course, invented long ago, so I can’t take the credit for this.  One that fired potatoes would not come until much later though.

Here is what I came up with:

full bolt action mini potato cannon

I go over the pneumatics in this post, but here’s an animation of Read more »