btrettel's Nerf blog

Back in 2006 I had an idea to improve a pneumatic Nerf gun my brother made. This Nerf gun had a semi-auto valve. At the time I was interested in semi-auto Nerf guns, but I saw the valve as a more daunting task than an advancement system. Like my brother, I started focusing on only the valve as the advancement system could come later.

I eventually started building the Nerf gun, but I ended the project after I found that one seal I used was too small and leaked. I later decided to end the project, but still, I did not see this as a waste of time as I learned a number of things in the process of planning and building (partly, at least) this Nerf gun.

I called the gun NAM, which stood for Nerf Assault Musket. You can view some images of the Nerf gun in construction here: http://btrettel.nerfers.com/images/nam/

Problems with my brother’s Nerf gun

• The valve was difficult to construct. It required the use of properly sized O-rings, and quite a bit of tinkering was necessary to get it to seal. But when it worked, it worked very well.
• The valve was difficult to service. To replace the seals (which seemed to be necessary on occasion) you had to basically take apart the entire valve. I didn’t intend to make servicing easier, rather, I wanted to make it unnecessary.

My solution

I replaced the O-rings with rubber sheets. This made sealing easier as the sheets did not have to be any precise size to seal. The rubber sheets basically sealed against the flat part of a 2 inch to 1 inch PVC bushing. I made the following animation to help explain this when I would get around to posting it.

The grey is pressurized air. The left end is the barrel. The right end is the air source. Basically, the valve cycles between filling the gas chamber (when the seal is against the left end) and evacuating the chamber (when the seal is against the right end).

I do not remember much more about the project aside from what I have detailed and linked to here. As I said, I considered this project to be a learning experience, and I kept many of the issues I had with this in mind when making FANG1.

Problems with NAM

Around the time I learned that one part would not seal correctly, I started thinking about the design and realized it had a few problems. Not all of what was listed below necessarily was on my mind back in 2007, but I see these problems now:

• Size – NAM was going to be a very long Nerf gun. Look at some of my photos; I couldn’t even fit the entire layout in one frame!
• Weight – PVC pipe was used extensively, and PVC pipe is not a lightweight material.
• Pressure source – If I recall correctly, I intended to fill NAM up with an air compressor. This is not practical for a Nerf war, and I made no plans to use a human powered pump of any variety (though, strictly speaking, this is perfectly possible with the air coupler swapped for a schrader valve).
• Lack of dart advancement mechanism – NAM was going to have a simple coupler for a barrel. This may have been okay for a test, but I wanted to go further.

Other things that caused me to change my design

• CaptainSlug’s ABP5K – This completely changed how I approached designing Nerf guns. Previously I limited myself to mostly PVC components as that was the norm. I did not really consider using components with only a structural purpose, even though that seems to be obvious now. You can definitely see CaptainSlug’s influence in FANG1.
• Reading more about spud guns – Over the next few months I would read a great deal about spud guns and how spud gunners designed them. Until 2008, I was basically ignorant about what a QEV was. I had assumed it would not have been something I would have been interested in even though I was familiar with them going back to perhaps 2005.

All in all, NAM was an interesting learning experience that definitely was not a waste of time. I need to get back into just tinkering like I did here.