Nerf Turret Part 2

Nerf Speedswarm teardown

I selected the Nerf Speedswarm for this project as it was fully automatic and was cheap (around $25.00). The Nerf Dart Tag Speedswarm is a 10 shot full auto blaster with ranges of about 35 feet. The Speedswarm is like a compact version of the Swarmfire with 10 less shots. Like the Swarmfire, this blaster won’t shoot Nerf streamlines unless you remove the dart pegs. I really liked the size, look and weight of the blaster, but I’m not sure about the blue trigger. Most Nerf guns require the user to pump them. The Speedswarm is the only Nerf gun under $30 I could find that was full auto, and can be operated electronically by pulling the trigger alone.

The SpeedSwarm is very hacker friendly. There are no glued parts or hidden screw holes. All I had to do was remove the few screws from one side to get the case open.

Once open you can see the system is very simple. There is an orange rotating barrel which is directly attached to the white plastic body that holds the firing system which is a spring powered piston. The actual circuit is very simple. A pressure trigger switch and battery case are wired together to a small motor.

Firing system

The gun function works by providing power to a small electric motor via the trigger pressure switch. When the trigger is pulled, 9VDC is applied to the motor which pulls the piston back and spring under tension.

The motor gears are missing teeth in strategic places which allows the piston to slip past the gears -under power by the spring- to fire each dart. At the same time the motor also pushes the rotating barrel one position to engage the next dart with each shot. This is done using a small lever at the same time the piston spring is put into tension. The timing of both of these parts is regulated by the gears, spring and motor. If the frame is expanded down the seam, it is possible to put the system into a configuration where the gears do not catch and the gun will not fire.

I found that there is a risk of this very thing happening, the frame expanding when I increased the voltage. To avoid this, I put a liberal amount of hot glue across the top seam of the piston housing and covered it with thick piece of paper before it cooled. This gives the seam more strength to resist coming apart and is much easier to remove if needed than real glue.

Battery cover doubles as false bottom

I do not intend on using the original battery case, but this makes a large hole in the frame without it. I found if I turn the case over it fits into the missing space in the frame perfectly and held in place with some hot glue.

I also removed the handle by using a wire clipper to break apart the plastic a bit at a time.

I then hot glued an empty wire coil to the battery case. On top of this I glued a servo wheel. I then hid the wire coil by wrapping with soda can aluminum.

Now that we have the basic tracking system working and weapon ready to go I figured it was a good time to come up with some form factor to hold the components. I didn’t want to spend time building a case or money buying one if I could get away with it. For now I wanted to focus on getting the system together and still working, I could spend more time on a great case later.

I was lucky enough to have saved the box my new cable modem came in after moving last year. It was actually a nice size to work with and would fit the project well.

• Electronic Speedswarm Nerf gun
• 2 Parallax PING))) Sensors
• 2 continuous servo motors
• 1 USB 5V rotating siren lamp
• 9V DC Speaker
• 1 Arduino Uno