2026-09-18 (F) Weekly Summary

I disassembled the old tang and blades and found that the coupler nuts were deformed, so I tossed them. I changed some sizing and clearance issues in the models and reprinted them. The most difficult problem was the aluminum bars, which were always too tight in the tang. I also need to drill out the internal switch piece holes before I shove a bolt through.

Everything fit smoothly

I wired up the latest parts and all the testing went perfectly! I got sparks along the blade instead of inside the handle, and it sounded fierce. My wife tested it on her arm a couple of times, and it scorched her, so I will have to regulate the battery power, swap out the transformer, or both.

Sparks where I want them

I spent the day researching how to use Zener diodes as voltage regulators. I plan to build battery holders in different colors—red for unregulated, yellow for medium voltage, and green for low voltage that runs all day. To find the optimal voltages, I will connect the knife to an adjustable power supply and find which voltage throws and which hurts but not too much. I estimate it will be a 1 W, 6 Ω resistor with a 1 W Zener diode rated at less than five volts.

Calculations and example circuit from an online tutorial

Removing the battery was clumsy, but I can improve it by combining the battery holder design with the end plug. Instead of a tapered machine screw, I will use a countersunk screw with a wedge-shaped cap, and if I size it for M8, it will allow tapping at 5/16”.

Sketch for a battery holder and plug

I started a new module that rendered the existing battery holder and added the braking unit at the back. The braking unit is currently just a long, rounded hexagon with a cavity for a machine screw. I made a hole that I will tap to M8 or 5/16", and it extends into the battery chamber so that I can pass a standard tap.

Rotating model showing the addition to the battery holder

I created a brake pad module that removes space for a lever arm and also makes the arm. The top of the arm is angled to match the countersunk machine screw, and the other side is parallel to the pipe's inner wall. When I insert the bolt, it should push the brakes out and hold it in place, but I worry it may twist.

Battery holder with brakes

The rest of the summary posts have been arranged by date.
First time here?

Completed projects from year 1
Completed projects from year 2
Completed projects from year 3
Completed projects from year 4
Completed projects from year 5
Completed projects from year 6
Completed projects from year 7
Completed projects from year 8
Completed projects from year 9
Completed projects from year 10
Completed projects from year 11
Completed projects from year 12

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