## Introduction: Miniature 3D Printable Catapult Using Tinkercad (move)

I am a middle school student who loves to tinker, build and invent new things. I spend a lot of my spare time on Tinkercad creating new projects. This one was inspired from a history book in which I read about siege weapons of the Medieval Era. When I saw the Tinkercad contest, I thought that I would most definitely make some sort of siege weapon for the make it move part. I hope you find this instructable useful and I would love to see your take on making it!

Note: this catapult is fully functional, and when modified for use with elastic bands, it is powerful.

## Supplies

There are not many supplies for this, but you will need:

This Instructable

A 3-D printer (optional)

## Step 1: The Bottom of the Frame

To start the catapult, you will need only boxes to make the bottom of the frame. To start with, take a cube and place it on your workplane. scale it to 75 mm long, 5 mm wide and 5 mm tall as well. Duplicate that shape, and move it over 35 mm (so that there is a 30 mm gap between these two prisms). Next, take another cube and set the dimensions to 30 mm long, 5 mm long and 5 mm wide. Place this shape between the two longer cuboids at the end of the two. Next, duplicate the smaller cuboid and move it along (or align) it so that it is in the exact middle between the two longer cuboids (this middle cuboid is there to add strength to the finished structure). Finally, duplicate the cuboid again, and this time move it so that it is at the other end to the first smaller cuboid that you placed. Once all of the smaller cuboids are in place, group all 5 shapes to form the bottom of the frame.

## Step 2: The Cross Pieces - Finishing the Frame

For the next step, you are going to make the cross pieces that holds the pole, and the catapult arm. Drag a cube into the workplane again, and set the length to 44 mm, height to 5 mm and width to 5 mm. Next, rotate the cuboid either 45 degrees, or -45 degrees (it doesn't matter now, and you'll see in a minute). Raise the cuboid until it is on 0 height (the bottom tip is touching the workplane). Then, duplicate the cuboid and rotate it 180 degrees. Next, move one of the cuboids 19 mm away from the other. Group the two shapes, and place it at the front of the catapult (as shown in the 5th picture of this section). Finally, duplicate the shape you have just made and put it on the other side of the frame's base, parallel to its counterpart. You have now finished making the frame!

## Step 3: The Arm's Pivot Point

This step is by far the easiest, and should cause little to no confusion. To start with, take a cylinder and place it on the workplane. Bump the number of sides up to 64 (maximum), and change the height to 40 mm, and the length and width to 4 mm. Change this cylinder to a hole. Duplicate the cylinder and make the sides 3.5 mm, rather than 4 mm. Take the cylinder that is a hole, and place it in the middle of where the two angled cuboids are (shown above). Then, group the frame with the hole. Repeat with the other cylinder that you made, except place this cylinder in the middle of the hole that you just made in the frame.

## Step 4: The Catapult's Arm

This was probably the most tricky step, though pretty easy when not describing it! Start by taking a half sphere and setting the dimensions to 16 mm wide, 20 mm long and 6 mm high. Duplicate that half sphere, make it a hole, and set the dimensions to 14 mm wide, 18 mm long and 4 mm high. Align the two shapes in such a way that the bowl that you have created has a 2 mm wall thickness, then group them to make that bowl. Create a cylinder, bump the sides up to 64, then flip it 90 degrees. The dimensions are 71.5 mm long, 6 mm wide and 6 mm high. Align it with the bowl, then move it until it touches the bowl. From there, push it into the bowl 10 mm. Ungroup the bowl, then select all 3 of the shapes and group them so that the cylinder fades naturally into the bowl. Next, create a 9 by 9 by 9 cube, and place it so that one edge touches the end of the arm without the bowl. Align the two shapes. Raise the whole arm (aside from the cube) 2 mm off the workplane. Then, move the cube 28 mm along the arm of the catapult so that there is a 19 mm gap between the cube and the edge of the arm without the bowl. Finally, make a cylinder and rotate it 90 degrees. Make it a whole and bump up the sides to 64. Make the dimensions of the cylinder 4.50 mm high, 4.50 wide and any length as long as it is 9 mm or larger. Place the cylinder through the cube and then group all of the shapes.

## Step 5: Finishing and 3-D Printing

To finish, place the arm through the cylinder that spans the 2 sides of the frame. If you aren't going to 3-D print it, then it's finished - enjoy! If you are going to 3-D print it, you will need to disconnect the arm and the cylinder that spans the frame, print them and then attach them.

To assemble, slide the cylinder through one side of the frame, through the arm and then through the other hole in the frame. Glue the cylinder to the frame and have fun with your very own catapult!