Can you engineer a chain-reaction machine that runs for 30 seconds and completes a task — without a single volt of electricity? You'll think, plan, build, and test — just like a real engineer.
Before you build anything, you need to understand the problem. Engineers don't start by building — they start by asking questions and learning from existing designs.
A
🎯 The Problem
You are designing a Rube Goldberg machine that must run continuously for at least 30 seconds after being triggered, and end by completing one simple, real task. No electric or battery-powered parts are allowed — every stage must run on gravity, springs, rolling, or other mechanical energy. To succeed, you need to understand how chain reactions work and why some machines are more reliable than others.
What You Need to Do
Two tasks for Criterion A
01
Research Chain-Reaction Machines
Explore the resources below and take notes on what you find. Focus on these four big ideas:
Simple Machines — Levers, inclined planes, pulleys, wheels & axles, wedges, and screws all move force differently. Which ones can you combine into a chain reaction?
Energy Transfer — Every stage must hand off enough energy to trigger the next one. How does potential energy become kinetic energy as your machine runs?
Reliability & Redundancy — A 30-second machine only works if every single stage fires every single time. Look for ways to build in backups so one wobble doesn't end the run.
Real-World Examples — Look at classic Rube Goldberg cartoons, music-video contraptions, and marble-run machines. How does each one keep the reaction going?
Simple Machines
Study these four building blocks — which will YOU combine?
LeverA bar that pivots on a fulcrum. A small push on one end lifts a load on the other.
Inclined PlaneA ramp that turns height into speed. Marbles and balls love this one.
PulleyA wheel and rope that redirects force. Pull one way, lift the other.
Wheel & AxleA small turn of the axle becomes a big turn of the wheel — great for rolling stages forward.
Why Chain Reactions Work
The physics behind every stage handoff
Potential → Kinetic EnergyHeight and tension store energy. When released, that energy becomes motion that powers the next stage.
One Trigger, One ReactionEvery stage must reliably reach the next. Test spacing and force so nothing stalls mid-run.
02
Sketch Two Real Machines
Choose two real Rube Goldberg machines you've researched (cartoons, videos, or contests) and sketch them by hand. Each sketch should:
Show the overall flow of stages clearly
Include the simple machines used (lever, ramp, pulley, etc.)
Be labeled with the machine's task and the mechanisms used
Include one sentence explaining why you think it's reliable
1. What are the six simple machines, and how does each one move or redirect force?
2. How does potential energy become kinetic energy as a chain reaction runs?
3. What makes one stage reliably trigger the next — and what makes it fail?
4. Based on your research, which mechanisms will YOU use — and why?
📋 For Your Slideshow
Complete Slides 3 and 4 in your student slideshow:
① Use your research notes to answer the 4 questions above — write like you know how!
② Include TWO sketch drawings of two different real Rube Goldberg machines. Don't forget to title your sketches.
Slide 3 — Research AnswersSlide 4 — Machine Sketches
Criterion B
PLAN YOUR MACHINE
Engineers don't build right away. They plan first. A strong plan helps prevent stalled stages and leads to a machine that runs all the way through.
B
🎯 Your Goal
Design a Rube Goldberg machine, built only from non-electric materials you bring from home, that runs for at least 30 seconds after being triggered and ends by completing one simple task. Your plan should show clearly how each stage will reliably trigger the next.
Example: Stage Flow
Use this as inspiration for your own sketch
Stage Flow — Top ViewLabel each stage with the simple machine it uses and draw an arrow to the next.
Trigger DetailWhere one stage hits the next is where machines fail. Plan generous contact zones and test them.
What You Need to Do
Three tasks for Criterion B
01
Choose Your Task & Mechanisms
Think about everything you learned in Criterion A and decide on your approach:
What simple task will your machine complete at the end? (ring a bell, pop a balloon, water a plant, turn a page, close a door...)
Which simple machines will you use at each stage, and in what order?
Where will the energy come from — gravity, a stretched rubber band, a released spring?
02
Create a Detailed Sketch
Draw your machine design by hand. Your sketch must include:
The full flow of the machine from trigger to task, in order
Labels for each stage and the simple machine it uses
Arrows showing the direction energy travels between stages
Marks showing where you'll add backups in case a stage misfires
Your sketch doesn't need to be perfect — it just needs to clearly show your idea.
03
Write Step-by-Step Build & Trigger Instructions
Before you start building, write out your plan like a recipe. This should include:
The order in which you'll build and test each stage
The materials you'll use for each stage — and a backup in case one isn't available
How each stage physically triggers the next one
What you'll do if a stage doesn't fire reliably in testing
⛰️
Use Gravity Wisely
Height is free energy. Start high stages early so falling and rolling can power the stages that follow.
🔁
Keep It Reliable
Build in backups. If one marble misses, does the whole run stop? Design for second chances.
📍
Plan Your Triggers
Machines most often fail where one stage meets the next. Think carefully about contact points.
⏱️
Think About Timing
Thirty seconds is longer than it sounds. Plan pacing — some stages should stretch the time, not just speed through it.
📋 For Your Slideshow
Complete Slides 5 and 6 in your student slideshow:
① Your step-by-step build and trigger instructions (both partners contribute).
② Detailed sketches of your machine design — full stage flow and a trigger closeup.
Now it's time to turn your plan into a real machine. Follow your design, make smart adjustments, and document every step of the way.
C
🎯 Your Goal
Build your machine using non-electric materials you bring from home. Follow your design sketch as closely as possible, but make smart changes if a stage isn't firing reliably — and note what you changed and why.
The Three Build Stages
You'll photograph your machine at each of these moments
BeginningSet up and test your first 2–3 stages. Take a photo before the rest is connected.
MiddleMid-stages connected and test-run. Capture it before the final task piece is attached.
FinishedComplete machine, decorated and ready for a full end-to-end test run.
Building Tips
Work smart, not just hard
01
Follow Your Plan — But Test Constantly
Use your Criterion B sketch as your guide, but build and test one stage at a time before connecting it to the next. If you deviate from the plan, make a quick note of what changed and why — this is valuable data for your Evaluate section.
02
Work Carefully & Together
Use materials wisely — plan for enough for the whole run
Focus on clean, dependable contact points between stages
Let glue or tape set fully before testing a connected stage
Work together — communicate with your partner
No electric parts of any kind — if it needs a battery, redesign it
03
Document Your Progress
Take photos at three key stages of your build:
📸 Beginning — your first 2–3 stages set up and tested
📸 Middle — halfway through, stages connected and running
📸 Finished — your completed machine before the timed test
04
Substitute Smart & Decorate 🎨
If a material you planned for isn't available, swap in something similar that does the same job — and note the substitution and why it still works. Then make your machine yours: decorate it, name it, give it personality.
🔧 If a Stage Won't Trigger Reliably...
That's engineering! If a domino keeps missing, a ramp is too slow, or a lever won't tip — don't panic. Adjust spacing, add weight, shorten the gap, and note what you changed. Problem-solving under constraints is exactly what this project is about.
📋 For Your Slideshow
Complete Slides 7 and 8 in your student slideshow:
① Photos of the three building stages (beginning, middle, finished).
② A final glamour shot of your decorated machine, ready for testing!
Slide 7 — Build PhotosSlide 8 — Finished Machine
Criterion D
TEST & EVALUATE
Engineers don't stop after building. They test, analyze, and think about how they could improve. Now it's your turn.
D
30sec
Did it run?
✓
Task completed?
0
Electric parts used?
How the Test Works
What you'll be watching for during the timed run
The Timed RunStart a stopwatch at the trigger. It must run at least 30 seconds and finish by completing the task.
Common Failure PointsMost machines fail from gaps that are too wide or stages with too much friction. Note where yours struggled.
What to Do
Four parts to your evaluation
01
Test Your Machine
Trigger your machine and time the full run. As it runs, observe carefully:
How long it ran before completing the task
Where it hesitated, stalled, or needed a nudge first try
How consistent it was across multiple runs
02
Record Your Results
Write down the facts from your test:
The total run time, from trigger to task completion
Whether it met the 30-second goal and completed the task (yes or no)
What happened during the test — describe it like a scientist
03
Analyze Your Design
Compare your original plan to what you actually built and how it performed:
What worked well in your design?
Which stages were the most reliable?
Which stages were the weakest — and why do you think that happened?
04
What Would You Improve?
Engineers are always improving. If you built it again:
What specific changes would you make to the design?
How would those changes make the machine more reliable?
What's the most important thing you learned from this whole experience?
💡 Didn't Hit 30 Seconds or Finish the Task?
That's okay — and it's actually great data. A machine that stalled at stage four taught you something a perfect run couldn't. Write honestly about what happened, why you think it happened, and what you'd do differently. That kind of reflection is exactly what Criterion D is looking for.
📋 For Your Slideshow
Complete Slides 9, 10, and 11 in your student slideshow:
① A video of your machine's timed run (film it!).
② A list of improvements — there's always room to grow.
③ A written reflection — at least one full paragraph in your own words.
Know the language of engineering. These terms will come up as you research, plan, build, and evaluate.
V
Engineering Terms
Vocabulary for the Rube Goldberg Challenge
Chain Reaction
A sequence of events where each one triggers the next, without any outside help once it starts.
Simple Machine
A basic mechanical device that changes the direction or amount of force. The six types are the lever, wheel & axle, pulley, inclined plane, wedge, and screw.
Lever
A rigid bar that pivots on a fixed point (the fulcrum) to lift or move a load.
Inclined Plane
A sloped surface, like a ramp, that lets gravity turn height into motion.
Pulley
A wheel with a rope or string over it, used to redirect a pulling force — often to lift something.
Wheel & Axle
A wheel attached to a rod (axle) so that turning one turns the other, multiplying force or speed.
Potential Energy
Stored energy, based on position or tension — like a ball at the top of a ramp or a stretched rubber band.
Kinetic Energy
The energy of motion. Potential energy converts to kinetic energy the moment something starts moving.
Energy Transfer
How energy moves from one stage of a machine to the next — for example, a rolling ball tipping over a lever.
Trigger
The action or push that starts a machine's chain reaction, and the point where each new stage begins.
Redundancy
A built-in backup so a machine still works even if one part doesn't fire perfectly the first time.
Friction
A force that resists motion between two surfaces. Too much friction can stall a stage before it reaches the next.
Reference
RULES & MATERIALS
Engineers often work within strict constraints. Part of the challenge is using what you have on hand, wisely and creatively.
R
Bring Your Own Materials
There's no fixed kit — gather these categories from home or the recycling bin
📦
Structural
Cardboard, boxes, books, tubes
🔵
Motion
Marbles, balls, dominoes, toy cars
🧵
Connectors
String, tape, rulers, tracks
🔔
Trigger & Finish
Cups, bells, spoons, balloons
⚠️ Important
No motors, batteries, circuits, or app/remote-controlled parts of any kind. Power must come only from gravity, springs, rolling, tipping, or other mechanical energy. If a material you planned isn't available, substitute something similar that does the same job — and explain your substitution in your slideshow.
The Challenge Rules
Your machine must meet all three requirements
⏱️
Run 30+ Seconds
From the first trigger to task completion, the chain reaction must keep going for at least 30 seconds without anyone touching it.
✅
Complete One Task
The final stage must accomplish a simple, real task — ring a bell, pop a balloon, water a plant, turn a page, and so on.
🚫
Zero Electric Parts
No motors, batteries, circuits, or remote controls anywhere in the machine — mechanical energy only.
🏆 Remember
A machine that runs the full 30 seconds, completes its task, and is beautifully designed is always better than one that just barely limps across the finish line. Aim high — your machine could end up in the Hall of Fame!
Assessment Tool
IB DESIGN RUBRIC
Click a level for each criterion to calculate your score. Each criterion is worth 1–8 marks. Total is out of 32.
Assessed via student slideshow — Slides 9, 10 & 11
Grade boundary reference
1–8
Grade 1–2
9–14
Grade 3–4
15–22
Grade 5–6
23–32
Grade 7
Interactive Tool
MACHINE LAB
Build a chain reaction using only simple machines. Pick a material for each stage, then run it and see if you can beat the 30-second target — without anything breaking.
⚙
🎮 How To Use The Lab
1. Click a simple machine below, then click a stage in your chain to place it there.
2. Click a material, then click a stage to set what it's made of. Materials change speed and reliability.
3. Use + / − Stage to change how many links are in your chain.
4. Hit ▶ Run Machine and watch the timer. Every machine and material combo has its own speed and its own chance of holding up under pressure!
1. Choose Your Simple Machines
Click one, then click a stage below to place it
2. Choose Your Materials
Click one, then click a stage to apply it — you can bring your own, just like the real challenge
3. Build Your Chain Reaction
Click an empty stage while a machine and/or material is selected above
0.0s
Estimated Time
30s
Target Run Time
—
Est. Success Chance
0.0s
Trigger → 30+ Seconds → Task Complete
💡 Why This Matters
Sturdier materials (like metal) are more reliable but slower. Slippery, light materials (like plastic) are fast but less predictable. Real Rube Goldberg builders make this exact trade-off — that's why redundancy and testing matter so much in Criterion C and D.