Mechanical Level 2 - Mechanism Design & Analysis

Learning Objective

Apply Level 1's generic mechanical foundation to FRC-specific problems: design and analyze power transmission systems (gear trains, belt and chain drives) with proper ratio calculations and component selection, understand bearing and shaft design for rotating machinery, use pneumatics as an actuation option, evaluate common FRC drivetrain types and when to use commercial-off-the-shelf (COTS) parts versus custom fabrication, and integrate multiple mechanical elements into a working mechanism validated with a physical prototype. This level is self-guided and typically takes a couple of months; completing it means you can perform most of the basic mechanical tasks the team needs day to day.

Prerequisites

• Mechanical Level 1 - Basic Mechanical Concepts
• CAD Level 1 - Fundamentals

Primary Resources

• FIRST Mechanisms Worksheet
• FIRST Robot Chassis & Drive Trains guide
• FIRST Pneumatics Manual
• WCP mechanism catalog
• REV Robotics catalog
• AndyMark catalog
• LearnFRC Mechanical, Build & Pneumatics track (mechanism and drivetrain lessons)

Tasks

1. Power Transmission

   • Calculate gear ratios and resulting output speed/torque for a gear train
   • Design a gear train for a specific application
   • Calculate belt/chain ratios, center distances, and required tension
   • Select an appropriate belt or chain for a given load
   • Build and test a simple gear reduction system

2. Bearing & Shaft Design

   • Select bearings based on load and speed requirements
   • Design a shaft system with proper support and retention
   • Calculate basic shaft deflection and stress for a simple case

3. Pneumatics

   • Understand basic pneumatic system components
     • Compressor
     • Solenoids
     • Cylinders
     • Regulators
   • Size a pneumatic cylinder for a given actuation task
   • Understand FRC-legal pneumatic system requirements and safety practices

4. Drivetrain Fundamentals

   • Compare tank/West Coast Drive and mecanum drivetrains
     • Traction
     • Complexity
     • Maneuverability tradeoffs
   • Understand how gearbox ratio selection affects drivetrain speed and pushing power
   • Evaluate a COTS drivetrain kit (e.g. AM14U, WCP kit chassis) against a custom design

5. COTS vs. Custom Fabrication

   • Identify when a COTS mechanism meets a design need versus requiring custom fabrication
   • Evaluate cost, lead time, and reliability tradeoffs between COTS and custom parts

6. Mechanism Integration

   • Combine multiple mechanical elements into a working mechanism
   • Analyze force flow through an assembled mechanism
   • Design for adjustability and maintainability
   • Capstone build: design, build, and test a multi-stage arm or elevator mechanism

Level 2 Completion Requirements

• Build and demonstrate a working gear reduction system
• Complete a drivetrain comparison exercise with a documented recommendation
• Design, build, and test a complete mechanism against a given specification
• Produce basic technical documentation for the completed mechanism

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