Balance Challenge

Kristofer @ Strawbees

Keep a rolling ball on a Strawbees track and maintain balance using Quirkbot coding.



2 x 45-minute Periods

Class Size

30 Students

Group Size

2-3 Students


Explore more fun ways to program with Quirkbot and the hardware capabilities. Use it as a controller connected to the servo motor balancing a teetering, Strawbees seesaw track and balance a ping-pong ball. At the end of the lesson challenge the class to try to transport a ping-pong ball across as many tracks as possible before hitting the ground.


1-Legged Strawbee
2-Legged Strawbee
Quirkbot Servo Backpacks
USB cables
Alligator Clips
Servo Motor
Ping-Pong Balls
Mini Screwdriver


Lesson Split Time

Depending on needs, this lesson can be split and taught in two 45-minute periods. With a 15 minute break seperating two sessions for a break or clean-up. An additional 15 minute session at the end is for clean-up.

Team Dynamics

For groups working with Quirkbot students should understand the following roles: the Driver, the only person allowed to control the mouse for Quirkbot programming, and the Navigators, the ones that give directions on what to nodes to use and connect together. When working with Strawbees and Quirkbot at the same time, the Navigators become the the Builders (the group members that are responsible for constructing with Strawbees and test their creations for challenges). Be prepared to have students switch roles every 5 - 10 minutes.

Servo Mounts

Before beginning the lesson and save time build the Strawbees servo mounts and place on them for future use.

Learning Objectives

Express a solution in such a way that a computer—human and machine can effectively carry out for a problem.

Dive into an introduction of the Computational Thinking process by engaging in three steps: problem formulation (How does this work?), solution expression (build a model), and solution execution and evaluation (the results and feedback of solution).

Collaborate as a team to learn programming and build models to meet a solution to accomplish a challenge.

Engage in a difficult problem to solve using programming as a problem-solving tool where the outcome may not be desireable for a lengthy period of time.



Before teaching with Quirkbot programming be sure to make sure your classroom internet is setup and you are able to access the You will be unable to create and upload programs.

It is recommended to use Google Chrome to ensure Quirkbot CODE will work.


If a Quirkbot has stopped responding during class you can enable Recovery Mode. While on Recovery Mode the Quirkbot should be detectable again, allowing you to upload new code to it. Before starting lessons with Quirkbot you can familiarize yourself with the Quirkbot Recovery Mode instructions.


Students can register ahead of time with Quirkbot CODE and create an account to save and publish projects. Otherwise, students can log in as an Anonymous User and begin programming immediately.


Before screwing down the plastic horn onto the servo motor, snap a 2-Legged Strawbee onto the back of the longest horn and secure it down with mounting screw.

Lesson Steps

1. Introduction
5 minutes

Get your students starting to think practically about how elemental balance is for all inventions. In these exercises students will learn how to assemble a simple electronically powered balance that pivots a complimenting structure on a small motor.

Ask the class, "If you stood on the tip of a mountain, what is the motion you would make?" Have your students explain or even act it out! Mention, "You would fall! But you might be able to prolong your fall by balancing yourself using your arms and legs."

2. Building
20 minutes

Let your students know they will create a three dimensional structure in the shape of a pyramid, with the full use of the motor, their Quirkbot and their Strawbees. If you have an example made, display how it works. The motor will be attached to the top of the structure and pivot their “bridge” that will balance any items they choose to place on it (in this case, a ping pong ball). The motor is programmable through Quirkbot’s CODE portal so students can adjust the angle and speed at which the motor operates.

Have some students work on building the Strawbees tetrahedron structure to mount the servo motor on for the track. You can have students build multiple tetrahedrons that slightly decrease in size in order for a longer track for the ball to roll down on.

3. Building a Track
20 minutes

Let your students know building the track is a process and many times the ball will fall off. Make sure to show students how to assemble together the 2-Legged Strawbees and start by making a lot of them first before adding straws. It's important to note that the 2-Legged Strawbee's legs are slid further into each head of the other 2-Legged Strawbees. The center should not be rotating or moving around, but should be stationary. Walk around the room to check student's progress making on these.

4. Track Testing
5 minutes

Test the track to see if the ball can roll down from one end to the other. If the ball cannot, then fix the 2-Legged Strawbees and make sure the straws are not warping or are twisted between them. This might cause the ball to roll off the track before reaching the bottom. If your students are making extra tracks for the additional tetrahedra and the ball rolls down it fine, use a 1-Legged Strawbee to make a friction lock from the middle of the track

5. Servo Strawbees Mounts
10 minutes

To fasten the Servo Mount in your student's Strawbees constructions, here are two examples of how to wrap and connect Strawbees and creating a Servo Mount. You can add more Strawbees connected to each other to increase the friction and pull their legs through the holes to tighten the Servo Mounts. This helps your students attach the servo easier.

When putting a straw on the Strawbee on the servo motor horn, make sure to slide it over both the Strawbees and the motor arm itself. Encourage your students to pinch the end of the Straw first before sliding it so it covers both the servo horn and Strawbee.

6. Assembling the Track and Base
15 minutes

For this lesson, add two, 1-Legged Strawbees on each end of the servo motor mount. Students will attach the Quirkbot to the servo motor once the track is carefully assembled. Advise students to carefully slip the straws onto the servo horn and 2-Legged Strawbee to the track. One side of the track must be cut in half and trimmed to attach to the middle of the track. See the image as a reference.

7. Connecting Quirkbot
10 minutes

Attach the servo backpack to the Quirkbot in order to program the servo motor and connect the headers on the wire to the number 1 pins on the back. You can carefully hang the Quirkbot from the servo motor since it will be freely hanging as a touch controller.

8. Programming Quirkbot
20 minutes

Open Quirkbot CODE with the settings on Advanced so your students can see all nodes for this program. Have your students drag the following the nodes: 2 LEDs, 1 Converter, 1 Circuit Touch, 1 Servo Motor, and 1 Key Press.

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9. Showcase
15 minutes

Challenge your class with these: "Can you pass the ball from one Balancing structure to another?" "Can you make a long, steady track going down? See what happens if the ball rolls down too fast!" "Can you program the Quirkbot to keep the ball on top without having to touch it?

Let your students take turns and attempt to carefully balance the ball onto the tracks until it reaches the end. The Ball cannot fall off otherwise they have to switch!


To become steady and upright by distribution of weight.
The force from a physical body attracting another physical body with mass to its center.
The act of building up speed to move faster.
The condition when the outcome is undesirable and the opposite of success.
Forces are also described as a push or pull on an object. They can be due to phenomena such as gravity, magnetism, or anything that might cause a mass to accelerate.
A method of measuring the skill capability of a group or characteristic of something to pass through a set of conditions.

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