Retro Arcade Rube Goldberg Machine
// ABSTRACT
For EGR 121, a team of 20 students built a themed Rube Goldberg machine to transport a golf ball through a sequence of electromechanical sections without human intervention. My sub-team of four designed and built two sections: an Arduino-controlled elevator that detects the ball with an ultrasonic sensor and lifts it to the next stage, and an analog grand finale section that triggers a dramatic ending. The full machine ran twice successfully in under 8 minutes — a speed record for the class.
SKILLS
TOOLS
Project Structure
EGR 121's Rube Goldberg project is a large-team systems integration exercise: 20 students split into five sub-teams of four, each responsible for two themed sections. All sections must integrate seamlessly — the ball must transfer between sub-team sections without failure.
The theme was Retro Arcade, requiring visual design elements, sound, and mechanisms that evoked classic arcade games.
My Sub-team's Sections
Section 1: Arduino Elevator
The elevator section detects an incoming golf ball using an ultrasonic sensor, then engages a motor-driven elevator platform to lift the ball to the next stage.
Design requirements:
- Detect ball arrival without physical contact (to avoid redirecting the ball)
- Lift platform must engage reliably within 1–2 seconds of ball arrival
- Platform must return to the receive position automatically after each cycle
Implementation:
- Ultrasonic sensor (HC-SR04) mounted at the ball entry point, polling at 10 Hz
- Threshold-triggered motor engagement when ball detected within 5 cm
- Arduino Uno handling sensor reads, threshold comparison, and motor direction control via H-bridge driver
- Elevator rail laser-cut from acrylic for consistent travel and low friction
The elevator ran reliably across all test runs and both competition runs.
Section 2: Analog Grand Finale
The final section was entirely analog — no microcontroller. A ball-triggered analog circuit activated lights and a mechanical finale mechanism to signal the ball's arrival at the end of the machine.
Analog circuits were chosen for the finale to demonstrate a different design approach from the Arduino sections and to ensure maximum reliability (no code to fail).
Visual Design
The arcade theme was realized through:
- Laser-cut and engraved acrylic panels forming a pixel-art "Win Screen" — designed in vector software and engraved directly into the panel
- Themed decals on the elevator housing
- Coordinated color scheme across the sub-team's sections
Systems Integration
Integrating 20 students' work into a single machine is primarily a mechanical and communication challenge. Our sub-team participated in three full-team integration sessions, adjusting ball launch angles, surface friction, and trigger distances to ensure reliable ball transfer between sections.
Results
The full machine completed two successful runs in under 8 minutes during the final demonstration — a speed record within the class. Both of our sections performed without failure across all runs.