We want to continue an electric knife fighting tradition, but old designs are clumsy, sharp, or high-maintenance. The goal is to build an electrified baton which:
• creates a visible and audible spark
• will not disable a fighter when zapped
• will not seriously harm a fighter if jabbed
• is easy to service
• uses a rechargeable and swappable battery
• is affordable enough to build spares
• handles like a traditional weapon
• promotes the spirit of fun and competition, not harm
• hurts enough that being shocked is a deterrent
The project started as a way to form a team around the goal of building electric knives for the annual knife fight at Grindfest. We want a place to share photos, text, ideas, and maybe post it up so other people can copy our ideas or check our work for safety's sake.
If people refer to you as, "The first ingredient in a recipe for disaster," do us all a favor and try to revitalize the Beanie Babies trend instead of reading any farther. Anything that generates electrical arcs should be considered dangerous. Generating an electrical current in someone's body can cause muscles to "speak out of turn" in ways that are bad for bowels, brain matter, and hearts and stuff. If you zap someone who isn't prepared, they could lose their balance or worse. That said, these cheap stun guns are rubbish for self-defense. The zappy-sparky show is a deterrent, but that's just bluffing since these have less stopping power than a well-placed banana peel. They sting, and that's about it.
After this point, I am going to assume you're safe, foolish, masochistic, or a combination. Hey, I'm not the electric knife police, sort it out yourself.
Bill of Materials
I list specific parts throughout the instructions because that is how I built a working model, but substitutions are fine, so long as you understand why I picked the parts I show.
1" Pipe - This should have an inner diameter (ID) of 1" or 25mm
18650 battery - Probably wise to keep a few spares
18650 battery holder - Get the kind with a red and black wire
18650 battery charger
Stun gun* - Choose one model from below
Cold Steel Rubber Recon Tanto Training Knife 92R13RT
1" furniture leg protectors - Plugs for the back of the handle
(6 qty) 1/2" #6-32 countersunk machine screws
(2 qty) 1" #6 standoffs - 1" long with #6-32 internal threads
Normally open (N.O.) momentary pushbutton - hole mount
(3 qty) Solder sleeves - Clear shrink tube with a ring of solder, 24awg
Handle wrapping tape - Optional
Switch-pipe adapter - 3D printed
* Buying a raw high-voltage converter from an AliEx/eBay seller could land you with a device capable of damaging flesh. We chose to salvage one from an inexpensive stun gun.
We will start with the most exotic component in the entire build because it requires a 3D printer. If you picked a pushbutton with an exceptionally long threaded shaft, you might be able to skip this and mount your switch directly onto a chunk of pipe, otherwise, read on.
First, you will need to know a few dimensions from your parts. Starting with your switch, you will need the radius from the mounting threads, which is also the same as a hole you would drill to mount the switch. Be aware that this is a radius, not a diameter, so divide by two if necessary. With the example switch below, the switch has a thread diameter of 11.8mm, so the radius is 11.8/2 = 5.9mm.
The next dimension is the radius of the switch's hex nut. This measurement should come from opposite points. In the example switch, the hex nut is 17.5mm in diameter, so the radius is 17.5 / 2 = 8.75mm.
The next diameter we need is the outside radius of your pipe. The measurement must be in millimeters, so prepare your brain for a bit of unit conversion. I used 1" semi-flexible water pipe because it won't shatter like PVC. The spec sheet shows the outside diameter (OD), so remember to divide by two and convert to millimeters. The tubing has an OD of 1 5/16 inches, which is 33.3mm. 33.3mm divided by 2 is 16.6mm.
All my calculations are to the tenths place. You should be more precise if it helps you sleep better.
Take your measurements and head to my Round Pipe Switch Adapter Thingy. You will see a button labeled "Open in Customizer," which will show you eight editable fields. We only need to worry about three, namely, "Switch Thread Radius," "Switch Nut Radius," and "Pipe Outside Radius." Enter these values and click "Create Thing." Download this Thing, print it, and move on to the next step.
The rest of the steps are simple compared to this run-about. To be fair, I spent five days refining that model, so cut a guy a little slack.