Monthly Archives: April 2011

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

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 »

Making CAD Drawings Look Better on the Web (and Other GIMP Filter Uses)

If you’ve ever tried to put a mechanical drawing that you’ve saved as a .gif or other format on the internet, you’ve probably noticed that the lines don’t generally come out that well.  Depending on your CAD package there is probably some way to fix this with a line weight selection, however, I’m going to focus on how to darken your lines after the fact.

To accomplish this, I used the free GIMP photo editing package and it’s set of filters.  While experimenting with this in GIMP, I also discovered that the “filter” menu in the main window can do some really cool effects as well.

"COVER" mechanical drawing

Before filter

cover after applying "cartoon" filter

After "cartoon" filter











The images above are simple examples of how the “cartoon” filter in GIMP can enhance a mechanical drawing.  In some circumstances, this may be helpful.  If you want to try this yourself, Read more »

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

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 »