LEGO Gear Robot {Mechanical Project!}

Here’s a super cool LEGO project with gears! Build a robot that turns its head and moves its arms when you push it.

This robot is SO much fun to build, and the perfect project for kids who love to tinker and invent things.

I had originally build this robot with wheels, but they were not connected to the mechanism with gears. The head only turned when you moved the arms. My oldest son (who is now 22 and married and has a full-time job!) was over at our house and suggested that we should gear up the robot so that when you pushed it, the head would spin and the arms would turn.

I told him that sounded fun, but suggested that HE should fix it for me. And he did! 🙂 So part of this is his design. He is WAY better at mechanical projects than I am.

Once kids understand the concepts involved in getting this robot to work, it’s really quite simple to build.

This can be a very open-ended project. Kids do not need to make their robots look exactly like ours! Encourage them to get creative with the bricks they have. They might design a totally different head or body.

To get parts of a robot to rotate both horizontally (the head and wheels) and vertically (the arms), you need gears that intersect at a 90 degree angle. Bevel gears are the best for this.

This project uses 20-tooth bevel gears (2) and 12-tooth bevel gears (3). You’ll also need some Technic axles and Technic bush.

On the bottom of the robot, there is a set of two 12-tooth bevel gears. One gear is on the same axle as the back right wheel. When the wheels turn, this gear turns, which turns the gear that is meshed with it.

I used Technic axle pins (with no friction ridges) for the wheels that are not part of the gear assembly. These pins allow the wheels to spin freely. Then I used a 4 stud long axle for the wheel and gear.

The axle that runs vertically through that gear on the bottom of the robot goes up through the body and into that tan 20-tooth bevel gear that you see in the photo below.

The tan gear meshes with another 12-tooth bevel gear that is on the arm axle. The arms are on a 10 stud long axle that runs straight through the body.

To make the head turn, there is another 20-tooth bevel gear that meshes with the 12-tooth gear from above.

You can see the gear and axle for the head in the bottom right of the photo below.

The gear is sitting on top of the 12-tooth bevel gear. Then the axle sticks out through a 2 x 2 round tile with a hole.

The robot’s neck is a 2 x 2 round brick, which slides onto the axle. This enables the head to turn when you push the robot forward.

LEGO Gear Robot Video Demonstration

Here’s a video that shows our robot in action! It also shows how the gears work together. Click the play button to start the video. If you don’t see the play button, it’s probably because of an ad blocker on your web browser. Ads allow me to keep my content free for readers!

Want more Mechanical LEGO Projects?

Build Awesome LEGO Gadget and Machines – these are all projects with moving parts that DO something!