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The Auto Sword (Lazy Man's Sword)

The lazy man's sword is also called the "Auto Sword". It is a sword that swings all by itself. So it saves fatigue on your arm.

So, with this sword you can eat a sandwich and fight orcs at the same time. Makes things so much easier :)

This project also comes with a video. It is at the bottom of the page.

Will has a youtube channel with over 700 videos on projects you can make. Check it out right here


Will with the Auto Sword


The auto sword




Overview: I am not sure how the idea came to me but it seemed like it would be a lot of fun. I doubt anything like this has been done before so I went ahead and made it. I also went through a few different iterations when trying to figure out the mechanism of this sword. And my first thought was some kind of cam mechanism. Want to learn more about the creative process behind this project? Check out The Creativity of it: The Lazy Man's Sword

Would you consider a donation of $1 to support my work? Paypal makes it very easy and safe. Click here to donate $1 - Every little bit helps Will to keep making great tutorials and projects. Thanks!



Tamiya 72005 6-Spd Gearbox High Efficiency Kit

This is the exact little gear box motor that I purchase for this project. You build the gearbox and arrange the gears depending on the speed you want it to spin at. At the slower speeds you get more torque.



  • 1 Sheet of foamboard
  • 1 Gearbox motor (3 volt dc motor)
  • 1 battery box that holds two AA Batteries
  • 1 Switch
  • Some Wire
  • Hot glue gun, Or some kind of glue for foamboard
  • Some pieces of wood or popsicle sticks for the mechanism
  • A couple of small pieces of wood around 3 x 5 inches each
  • Some small screws

Battery box

5 Pcs Battery Box Holder w Cap On/Off Switch for 2x1.5V AA Batteries

This battery box comes with a switch. So you don't have to purchase or use a separate switch.


Ok, let's take a look at the sword. And if you have watched the video you know that the blade of the sword moves up and down kind of in a hatchet type of motion.

The Lazy Man's sword


This motion is achieved with a simple mechanism. It is a class 3 lever that converts the circular motion of the motor into a linear motion. Although it isn't a true linear motion. Lets take a closer look at the mechanism that does this.

The best way to understand this motion and this mechanism is to watch the video. It is only one minute long and shows this sword in action.

Diagram showing the motion of the motor and sword

The dashed circle is where the motor is. As the motor spins it pushes the wooden arm forward and backward. And this pushes the blade in the back and forth motion.

In this picture the arm is pulled back all the way. It is on one end of its arc.


The sword extended

This picture shows the motor at the other end of its arc. Now you can see that the arm is pushed all the way forward. And this pushes the blade of the sword all the way in one direction. The motor will continue it's spinning and draw this whole thing back to the starting position.


The pivot

One important point about this mechanism. In order for it to work properly you have to have the pivot point (fulcrum) of the mechanism in the same place as the pivot point for the sword inside.


The pivot point of the mechanism

This picture shows you what I mean. The wooden arm and the sword inside both pivot on the same point. This is an important thing when making this sword.


NextOk, You can watch the video below or you can continue on with the tutorial


Video Here:


Rapier sword

Make a Rapier sword

A rapier was a dueling sword from the 15th to 17th centuries and it is a great looking sword because of the intricate handle guard work. I have a template for you and you can make it with one sheet of foamboard. How to Make a Rapier


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