Pak40 » Page 1 of 1

Here is a 21st Century Pak 40 that has been modified to use the Battle Circuit in conjunction with a commercially available ultrasonic motion detector kit.

The ultrasonic motion detection is in the gray box the the left. The sensors are the two silver circular objects.

The electronics are in the two black boxes behind the Pak 40. I didn't have one box big enough so I used two and glued them together.

The first step was to cut the muzzle break off so I could drill the barrel out. Not an easy task, go slow and straight. I worked from both ends to meet the middle. Since the barrel is skinny I ran the wire through and ended up glueing the flash LED at the end of the barrel and reattaching the muzzle break.

The recoil action on the Pak 40 works (by hand), but I had to add ceramic grease and reassemble the bottom carriage to make the action as smooth as possible. I used a servo with my recoil board and the action needs to be as smooth and easy as possible. No springs are needed.

The servo is mounted as shown, there is room for some screw heads so a bracket can be mounted to secure the servo to the gun carriage. The picture shows my first attempt, the servo is actually shown backwards here from my final asembly, the shaft is toward the back of the gun in the final configuration.

The white tube mounted to the left of the gun shield is the mount for the infrared LED.

Here is a shot of the servo in place. It is hot glued because I need to remake the bracket. The hot glue will hold for a while but an aluminum bracket should be a better solution. The servo arm attaches to brass wire that is attached to a hole drilled through the receiver block. If everythig works smoothly and there is no binding the action looks and works great. View the video on the home page by clicking on the photo of the recoil board.

There is one detector mounted on the gun shield with 4 hit LEDs. With one detector you can only hit the gun when it can hit you (in front of it).

It works great indoors. Outdoors result will vary. The ultrasonic detector is not perfect and may false trigger a lot, but with a fire rate of two seconds it's an adversary to watch. With sound triggered to the firing of the gun you'll get a nice noisy battlefield!

The idea was to have an anti-tank emplacement that would operate by itself. These could be used for ambush or to guard an objective. I had several ideas on how to make these work. I think the ultrasonic detector works well, the timed firing where the gun fires at a steady rate is the simplest. Click here to see my other ideas: