Introduction: Tinkercad Robotics for School: Evil Zipline Robot!

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About: I'm Mario Caicedo Langer (M.C. for short), a Colombian STEAM educator living in Azerbaijan, BSc in Naval Sciences, Master in Toy Design, and former Navy officer. I am a CAD and 3D Printing enthusiast and an ar…

Hello! My name is Mario. Welcome you to a new lesson of "Tinkercad Robotics for School", where you can learn how to use Tinkercad to create simple and easy fun machines!

Today's challenge: we will create an Evil Zipline Robot! This little plastic machine can walk along a string or cable, sloth-style. I'm in love with this kind of machines since I was a kid and I saw this little bot in an episode of "The Wizard", an 80's TV series about a toys inventor. That inspired me to create a prototype one year ago, recycling a broken 3D pen and some 3D glasses. Also, there is a great zipline robot project by Tart Robotics, using Lego and some extra components.

What makes this project special is the following attributes:

  • Simplicity: the target is to teach design of a basic mechanism for a simple robot; so I wanted to keep the number and complexity of pieces at minimum. Also, the pieces may be reused or easily replaceable.
  • Fully 3D printed: no bolts, no nuts, no glue. Except for the gearbox, the power source, one zip-tie, and one little strip of mounting tape, almost everything was 3D printed.
  • Easy to design: in my first "Tinkercad Robotics for School", I created two walking machines (before trying this project, I recommend you to visit that one). Well, the good news is that the components to build one of these robots now are part of the Shape Library (Beta) of Tinkercad! And the better news: we will use and modify some of these components to create this Zipline Robot. That will save us a lot of time. You can identify those shapes by the code "MCL WR" in the category "Vehicles & Machines".
  • Customizable: the robot has available slots to place different accessories. I decided to go for "evilly weaponized character". But if you want, you can make it look like a monkey or a spider.

Supplies

  • 1 Computer with access to Tinkercad
  • 1 3D printer. Material: PLA. I'm using a Creality Ender 3 V2.
  • 1 Gearbox "I" shape (like this one)
  • 1 Battery holder for 2 AA batteries, with switch (like this one).
  • 2 AA Batteries
  • Zip-ties
  • 1 little strip of mounting tape.
  • Pliers (for removing support material)
  • Scissors (to cut the remaining zip-tie)
  • Flat screwdriver (in case you need to separate the pieces.)

OK, let's start with the fun!

Step 1: Main Body

As I mentioned in the previous step, we don't need to build the body from scratch.

Go to the Tinkercad library panel at the right of the screen, choose "Shapes Library (Beta)" and select the "Vehicles and Machines" category. Select the "MCL WR Body". This body was designed for a ground robot. However, we can repurpose it for our project.

Bring a "Hobby Gearmotor" from the category "Circuits" - "Components" and place it in the slot. Turn both shapes 90 degrees, with the flat area over the Workplane.

There is one critical change we must do to the body: adapting the battery holding area so, instead of carrying a 9V battery holder in horizontal position, it can carry a 2 AA batteries holder in vertical position, like a backpack. The best way is to fill the whole hole with a box, group it with the rest of the body, and then insert a new hole box with the dimensions of the 2AA Battery Holder.

IMPORTANT NOTE: for the moment, don't worry about the tolerances between the digital model and the real gearbox and battery holder. The printing will be with a 105% scale, for a better fitting of the real components.

Step 2: Cranks

From the same "Shapes Library (Beta)" - "Vehicles and Machines" category, select the "MCL WR Crank" and bring two to the Workplane. Place them aligned to the shaft on each side of the gearbox.

In real life, the shaft from the cranks must be opposite to allow the movement of the robot. That means: if the crank of the right is facing forward, the crank of the left must be facing back. However, in this part of the design both must be facing forward, to check that both sides are symmetrical and we can appreciate later if the hooks of the robot are aligned with the rope they will use to travel.

Now, bring a normal cylinder from the Library. Make it 5.00 mm diameter, and place it on top of the robot. This will become an axle to allow the articulation of the crank system while keeping it in place. Give it some bevel and segments, so the locking pieces can be placed in an easier way.

Step 3: Connecting Rod

From the "Shapes Library (Beta)" - "Vehicles and Machines" category, select the "MCL WR Short Rod" and bring it to a temporary Workplane over the crank. Turn it 90 degrees to a vertical position, and align the bottom hole to the crank's shaft.

This connecting rode will be the lower part of the robot's arm.

Step 4: Position Rod

Bring to the Workplane another "MCL WR Short Rod" from the "Shapes Library (Beta)" - "Vehicles and Machines" category. Remove one of the ends grouping it with a hole box. Instead that end, place a 5 mm diameter cylinder. This shaft will be connected to the robot arm, keeping it in place during the rotations of the crank. Give it some bevel and segments, so the locking pieces can be placed in an easier way.

To reduce stress and give more durability to the shaft, add a 9.66 diameter cylinder at the base and a "Revolved Adjustable" from "Shape Generators" in the union point to create a fillet. Then, group all these shapes.

Step 5: Aligning the Shafts

Bring the Position Rod to the robot, and insert its shaft through the Connecting Rod's available hole. Also, align the Position Rod's available hole with the cylinder that you placed on the top part of the body. This part requires a lot of hand dexterity: you must rotate or move these pieces until you have everything perfectly aligned.

When you are finally happy with the result, bring three "MCL WR Small Lock" from the "Shapes Library (Beta)" - "Vehicles and Machines" category, and place them on the shafts to "lock" the components.

Step 6: Replicating the Position Rod

Bring a new cylinder of 11 mm diameter, and align with the axle in the top part of the body. The functions of that cylinder are to attach the axle to the body, and to keep the Position Rod in place. Extend this cylinder and the axle to the opposite side, until you can appreciate the exact symmetry.

Now, duplicate the Position Rod, move it to the opposite side and use the mirror option to invert it. Check that the symmetry keeps being respected.

Step 7: The Arm

To create the arm, bring the "Bent Pipe" from the "Shapes Generators - Featured" library. The idea is to create curve arm of Outer Pipe Width = 4. It's recommendable to avoid the use of the handles to modify the dimensions, so you can keep this 4 mm accuracy in all the component. To reach the ideal proportions, use the parameters in the Inspector and keep experimenting. Use the handles only for rotation.

Bring another Bent Pipe to create the hook, a finger that will catch the rope so the robot can move.

The Connecting Rod is not 4 mm thick. Because the dimensions are locked, the best way to extended it is copying and pasting it, aligning the copy and group both of them into a single shape. Then, align the arm, trying to keep the stress lines to the minimum.

Step 8: Aligning the Hooks

When you feel you have finished with the arm and hook, group them with the Connecting Rod. Then, duplicate the resultant piece, mirror it and place it on the opposite side, respecting the symmetry.

Check that the top of the arms and the joint angles of both hooks are aligned. Also, check that the hooks are more or less aligned with the opposed arm. If not, modify the Inspector parameters until you reach the perfect position. Also, using a Paraboloid from the "Basic Shapes" Library, create a tip for the hook and group them.

Keep modifying the arm until the hooks are well aligned. When you finish, check that both sides have all the pieces and locks in place.

Step 9: Preparing for Customization

Remove the residual shafts from the bottom part of the body, grouping each one with a hole box.

Insert cylindric holes of 6 mm diameter in the bottom and top part of the body. These holes will be slots to attach accessories.

With this step, we finished the design of the basic robot.

Step 10: Slicing and Printing

After finishing with the basic design, go to Tinkercad Dashboard, and duplicate your design.

In this second design, delete the gearbox, disassemble the robot, and place the pieces over the Workplane.

When you are ready, export the shapes as STL, and bring them to the slicer.

I printed my robot in a Creality Ender 3 V2, using PLA as material. As slicer I used Ultimaker Cura 4.8.0, with the default settings, supports and 20% infill.

IMPORTANT NOTE 1: don't forget to scale all the pieces to a 105% size, so the real gearbox and battery holder can fit easily in the body and cranks.

IMPORTANT NOTE 2: After testing the prototype, it was evident that the "MCL WR Crank" was too small for this kind of robot, jamming the arms when moving. So I improved it, adding more distance between the shaft and the slot for the gearbox.

Attachments

Step 11: Physical Assembly

Once all the parts are printed, bring the gearbox, battery holder, zip-ties and scissors. Time to build and test our toy!

Step 12: Physical Cranks

Attach them to each shaft of the gearbox. Don't forget they must be alternate! That means, if the shaft of one crank is facing to the front side of the gearbox, the shaft of the other crank must be facing backwards.

Step 13: Attaching the Gearbox

Bring the body part. Add a little strip of mounting tape over the gearbox slot and then, place the gearbox. Fasten the gearbox to the body using two zip-ties. Cut the remaining end.

Step 14: Left Arm

Assemble the left arm taking our previous design and the photos as reference. Be very careful, or you could break the arms or the shafts.

Step 15: Right Arm

Assemble the right arm in a similar way to the previous step. When you finish, spin the gearbox and check that both arms are moving without obstructions.

Step 16: Battery Holder

Place the 2 AA batteries inside the battery holder. Now place the battery holder in the backpack and connect the wires to the pins of the motor in the gearbox.

Step 17: Accessories

You can create your own accessories, adding to them a small cylinder of 5.8 mm diameter, so you can attach them to the available 6 mm slots in the robot. Don't forget to print them with scale 105%.

I imagined this little evil guy as some kind of sci-fi death machine stalking in the skies, and with spear-guns so it can launch another line and jump to it. You can customize in a less sinister way.

Have fun and stay tuned for more DIY projects!

Attachments