Tinkercad Robotics for School: Gerbil, the Jumping Robot!

Hello! My name is Mario. And I must recognize that the last entries of my "Tinkercad Robotics for School" series, are a little too complex for the majority of school students. For this new project, I wanted to create something that was simpler to create by teachers and students of grades 5, 6, 7 and 8.

So, if you like robots that are both fun and easy to build, today you are here for a treat: we will learn how to use Tinkercad to design and build Gerbil, a simple jumping robot! Using our traditional yellow gearbox, a rubber band, a 9V battery and 3D printed parts, the mechanism first moves up the stilts (the part that look like the legs) using gears that have teeth only in one half of them. This action stretches the rubber band, storing potential energy. When the teeth of the stilts reach the toothless part of the gears, the mechanism releases the stilts propelling the body upward (kinetic energy), more or less like a slingshot.

And it's so easy to print and assemble, that you can even build a little army! Add some decoration. You can design and 3D print some extra parts, or create a cardboard cover to make it look like a real gerbil or a kangaroo. Soon you will have a plague of mini-bots jumping everywhere!

• 1 Computer with access to Tinkercad
• 1 3D printer. Material: PLA
• 1 Gearbox "I" shape (like this one)
• 1 rubber band
• Zip-ties
• 1 Clip Connector for 9V battery (like this one).
• 1 9V battery. NOTE: at the beginning, I worked with 2 AAA batteries and their respective holder. However, tests demonstrated the robot worked far better with 9V.
• Pliers (for removing support material)
• Super-glue (cyanoacrylate, preferable with activator spray)
• Scissors (to cut the remaining zip-tie)
• OPTIONAL: 1 SPDT slide switch (like this one); soldering iron, soldering tin.

I started recycling the body part from one of my previous designs (the Evil Zipline Robot). I imported the STL with a 105% scale. Then I removed some parts that could obstruct the mechanism's movement.

From the Shape Generators, I brought a Cremallera and a Gear, and modified the parameters until the teeth of both components could intercalate. Then I brought a hole box, and placed in the center of the gear. The dimensions of the hole box are the same ones in the shaft of the gearbox, so it can fit. Then I grouped both shapes. .

I brought a Tube and aligned it to the center of the gear. I removed half of that tube using a hole box. I transformed the other half into a hole. I grouped this hole with the gear, to remove the teeth in half of it.

I selected and rotated both shapes, and placed them in the body, keeping in mind that the gear must be inserted in the gearbox's shaft. Then, I used a long box to create the stilt, and grouped it with the cremallera.

To keep the stilts in place, I brought some boxes to create a rail, so the stilt will only go up and down.

Using two cylinders, I created a groove on top of the stilt, so the rubber band can pass through it.

I also cut a segment of the body using a hole box, so the groove does not hit it when it goes down.

Using a solid box and a smaller hole box (with the stilt's dimensions), I created the socket where the stilt will be attached to the foot.

Using a Extrusion shape and some small cylinders, I created a foot.

If the body and the stilts are perpendicular to the feet, the robot will be jumping up and down in the same place. I wanted the robot to jump forward, so I rotated 25 degrees all the components except the feet. Then I grouped the ankle to the foot.

After this, I duplicated all the shapes but the body and the gearmotor, moved the duplicates to the other side, and used mirror effect to give symmetry. Then I grouped the rails to the body, the left stilt to the right stilt (their meeting point is the groove), and both feet.

To fasten the rubber band, I created a lug in the back, using two boxes and a cylinder; and a hook on the front, using cylinders and half spheres.

In Tinkercad, I returned to the Dashboard and duplicated the design, so I could rearrange all the pieces for a better printing; verifying that all of the components were laying over the workplane.

After rearranging the parts for printing, I exported the STL files and opened them in the slicer.

I used the following parameters:

• Printer: Creality Ender 3 V2
• Slicer: Ultimaker Cura 4.8.0
• Material: PLA
• Printing Temperature: 200°C
• Infill: 20% (body, feet), 100% (gears, stilts)
• Supports: Linear
• Raft: needed for the stilts, and maybe for the feet; to avoid any potential warping.
• Scale: 100%

I am attaching the STLs, so... now let's have some fun assembling it!

Take the gearbox. Attach the gears on each end of the shaft. Check that both gears have the teeth aligned, so they can hit and release the stilts at the same time.

Attach the gearbox to the 3D printed body, using an zip-tie. Tighten it, then cut the remaining part.

Insert the stilts from top to bottom of the body. The groove must be on top.

Attach the feet to the lowest part of the stilts. Use superglue if needed.

Place the battery into the backpack, and connect the wires to the pins of the motor. In this position, the red wire must be in front, and the black wire must be closer to the body. Note that at the beginning I tried with a AA battery holder, but its power was not enough, so I replaced it with a 9V battery.

Tie the rubber band to the back's lug, using a Lark's head (cow hitch) knot. Pass the rubber band through the top groove on the stilts, then secure it on the hooks placed on front of the body.

Your Jumping Robot is ready. You just need to connect both pins of the brackets to the battery. As optional step, you can also add a switch, so it's easier to turn your robot on and off. The Body's STL has a space where you can place it.

Time to take over the world, one jump at the time. :-)