Build a Mechanical LEGO Turtle

Wondering what you can build with LEGO gears? Here’s a fun mechanical LEGO project that will make you smile! This cute turtle pokes his head out of his shell when you turn a knob. How cool is that?

LEGO projects with moving parts are just extra fun.

Besides this LEGO turtle, you’ll want to check out our LEGO Mechanical Piano Player and our LEGO Weightlessness Training Machine.

Some friends of ours contributed the idea for this LEGO project. Thank you Addie and Scott! We love this mechanical turtle LEGO creation!

How the LEGO Turtle Works

When you turn the knob on the side of the turtle’s shell, his head comes out of the shell. The knob is connected to a 20-tooth bevel gear that turns along with the knob. As it turns, the teeth in the gear mesh with the teeth on a couple of gear racks on the turtle’s neck.

Want to see a video demonstration? Click the button to play the video.

Ready to build your own adorable LEGO turtle?

I’m not showing full step-by-step instructions on this one because:

1. It’s EXTREMELY time consuming.
2. And, I really want kids to be creative on this one! Don’t stress over having the exact pieces and colors we used.

Essential Pieces:

To build this turtle, you will need these bricks for sure. I’ve included links to the specific parts on Brick Link for easy ordering. If you’re new to Brick Link, you can read all about how to use the site here: Buying Individual LEGO Bricks on Brick Link.

• Two 1 x 4 gear racks
• A 20-tooth bevel gear
• An axle, 6 studs long
• Tiles – three 2 x 4’s, a 2 x 2, a 1 x 2, two 1 x 6’s (any colors, but gray is good)
• 2 – 1 x 2 Technic brick – one brown and one in any color (ours in black)

These bricks are not essential, but helpful:

• 1 – 8 x 8 plate (ours is dark gray)
• 1 – 4 x 8 plate (dark gray)
• 2 – 4 x 8 light gray wedge plates, cut corners
• 1 – 4 x 4 green plate

Start by building the turtle’s head on a 4 x 4 green plate.

Build the turtle’s neck. The neck is 3 studs wide, so you’ll need to build it with a series of 2 x 3 plates.

Another option is to make the neck 4 studs wide, but then the neck will be the same width as the head on both sides. We just thought it was a little cuter this way. But it’s totally up to you!

The little 1 x 1 slope at the end of the neck past the gear racks prevents the head/neck from coming ALL the way out of the turtle.

Add a 2 x 3 green place right behind the head to cover up some of the open neck and make the turtle look cuter. You can’t cover any more of the gear rack, though, or the mechanism won’t work!

Here’s a peek at the inside of the turtle’s shell. Basically, the shell needs to provide a space for the head/neck to slide back and forth. Place tiles on the bottom of the shell so that the neck is able to slide.

The axle is running through the gear, then through a bush, then a 1 x 2 Technic brick, then another bush, then the 1 x 2 brown Technic brick on the shell, and then the knob (a 2 x 2 light gray round brick with ridges).

When you turn the knob, the gear will turn. Depending on which way you turn the knob, the gear will push the head out of the shell or back into the shell.

Once you get the mechanism working, you just need to build a shell to enclose the gear and gear rack.

We made each of our turtle’s feet with two 1 x 2 slopes, a 1 x 2 brick, and a 2 x 2 plate and 1 x 2 plate under them. Then we added a 2 x 2 brick to each one. But you can design your feet however you want!

Want more mechanical LEGO projects to build?

If your kids enjoy building LEGO projects with moving parts, you’ll definitely want to check out our LEGO inventions book!

Genius LEGO Inventions with Bricks You Already Have is full of 40 cool machines and gadgets. Each project has an explanation of the physics and engineering concepts behind the motion. Kids will learn about gears, linkages, levers, cams, pistons, potential and kinetic energy, center of gravity and more.

Order here: Genius LEGO Inventions with Bricks You Already Have