Mechanical Guide | FRC Rookie Guide

Step 1

OnShape Setup & CAD Basics

OnShape is a free, cloud-based CAD platform perfect for FRC teams. No installation needed - works in your browser!

Why OnShape?

Free for students and FRC teams
Cloud-based - collaborate in real-time
Access from any device with internet
Built-in version control
Extensive FRC parts library

Getting Started:

Create Free Education Account
Go to OnShape.com and sign up with your school email (.edu). Choose 'Education Plan' for free access.
OnShape Education
Complete OnShape Learning Center
Take the 'CAD Basics' and 'OnShape Fundamentals' courses. These are essential!
OnShape Learning Center
Learn FRC-Specific CAD
Follow the FRCDesign.org course - it takes you from zero to modeling a full robot!
FRCDesign.org Course
Practice with Simple Parts
Start by sketching 2D shapes, then extrude them into 3D. Practice with brackets, spacers, and simple plates.

📚 Essential CAD Skills

Sketching (rectangles, circles, lines)
Extrude, Revolve, Sweep
Constraints (coincident, parallel, perpendicular)
Assemblies and Mates
Parametric design

🎥 Video Tutorials & Visual Guides

Learn OnShape with step-by-step video tutorials and visual resources:

Step 2

FRC Parts Library

Don't model everything from scratch! Use pre-made CAD models of common FRC parts.

Important Part Libraries:

MKCad - Essential FRC Library
MKCad is the most comprehensive FRC parts library for OnShape. It includes motors, gearboxes, wheels, and structural components.
MKCad Library
Vendor CAD Models
Download official CAD models from vendors:
- REV Robotics - Motors, structural components
- AndyMark - Wheels, gearboxes, chassis kits
- VEX Robotics - Various mechanical components
- WCP (West Coast Products) - Drivetrain components
Link Parts Library to Your Account
Follow MKCad installation instructions to link the library. Then you can insert parts directly into your designs!

💡 Pro Tip

Create a 'Parts Reference' document in OnShape where you collect all commonly used parts. This makes it faster to find and insert parts when designing!

Step 3

Drivetrain Design

The drivetrain is the foundation of your robot. Without a reliable drivetrain, nothing else matters!

Common Drivetrain Types:

🚗 Tank Drive (West Coast Drive) - ⭐ BEST FOR ROOKIES

Most common for rookie teams. Simple, reliable, and powerful. The AM14U6 Kit of Parts chassis is the perfect starting point!

6-wheel configuration with center wheel dropped (6WD)
2-4 motors per side (4 CIMs recommended for competition)
Good traction and pushing power
Easy to build and maintain
🆕 2025 Kit of Parts: AM14U6 Chassis

✅ STRONGLY RECOMMENDED for first-year rookie teams!

🎯 Swerve Drive - ⚠️ ADVANCED (NOT for Rookies!)

Each wheel can rotate and drive independently for maximum maneuverability. However, this is MUCH more complex than tank drive!

4 independent swerve modules (8 motors total)
Complex programming and mechanical design
Expensive - MAXSwerve modules cost ~$2000+ for full drivetrain
🆕 2025 Rule R302: Teams can now REUSE swerve modules from previous years!

❌ NOT RECOMMENDED for first-year rookie teams! Start with tank drive and consider swerve in year 2 or 3.

Drivetrain Design Steps:

Choose Wheel Size
Common sizes: 4", 6", or 8" diameter. Larger wheels = higher speed, smaller wheels = more torque.
Select Motors and Gearing
CIM motors or NEO brushless are standard. Use JVN Calculator to determine gear ratios for desired speed.
JVN Drivetrain Calculator
Frame and Wheel Layout
Typical robot size: 28" x 28" starting configuration. Design frame using box tubing (1" x 2" aluminum).
Add Chain/Belt Drive
Connect motors to wheels via chain (#25 or #35) or timing belts. Ensure proper tension!

⚠️ Common Rookie Mistakes (Not in Official Guides!)

❌ Drivetrain too slow - check gear ratios! Aim for 12-15 ft/s for tank drive
❌ Chain too loose or too tight - should have ~1/4 inch deflection when pressed
❌ Not enough motor power (minimum 4 motors total for competitive drivetrain)
❌ Wheels rubbing on frame - leave at least 1/8 inch clearance
❌ Forgetting to drop center wheels - robot won't turn smoothly without this!
❌ Not budgeting for weight - your robot will get heavier as you add mechanisms!

⚖️ CRITICAL: Weight Management (They Don't Tell You This!)

Maximum robot weight: 125 lbs (without battery and bumpers). Most rookie teams discover this TOO LATE!

🔋 Battery adds ~15 lbs (NOT counted in 125 lb limit)
🛡️ Bumpers add ~10-15 lbs (NOT counted in 125 lb limit)
⚠️ ROOKIE MISTAKE: Shipping robot with battery = 20-30 lbs extra = FREIGHT OVERAGES!
📦 Build your shipping crate LIGHT - some rookie teams make 50+ lb crates!
💡 PRO TIP: Budget weight for EACH subsystem (drivetrain: 40-50 lbs, intake: 10-15 lbs, etc.)
⚖️ Weigh your robot WEEKLY during build season - don't wait until week 6!
🎯 Aim for 110-115 lbs to have room for last-minute additions

📊 Your robot's center of gravity changes when climbing/extending - design for stability!

📸 Drivetrain Visual Resources

See real-world examples and detailed diagrams of FRC drivetrains:

For Rookies - Tank Drive:

Advanced - Swerve Drive (Year 2-3+):

Step 4

Intake Mechanisms

The intake collects game pieces. Design philosophy: "Touch It, Own It" - control the piece as soon as you touch it!

Common Intake Types:

🔄 Roller Intake

Most versatile and common. Works for balls, cubes, cones, and more!

Uses compliant wheels (4" or 6" diameter)
Powered by 1 BAG motor or 775pro
Can pivot or extend to reach ground

🤲 Claw/Gripper Intake

Grabs and holds game pieces securely.

Good for cones and irregular shapes
Uses pneumatic cylinders or servos
Simpler design than rollers

Design Considerations:

Game Piece Analysis
Study the game manual! What shape/size are game pieces? How heavy? Where are they located on the field?
Mounting and Packaging
Intake should deploy outside robot frame perimeter. Use pneumatic cylinders or motor-driven pivots.
Power and Control
BAG motors are perfect for intakes. Add limit switches to detect when piece is captured.
Handoff to Mechanism
Design how intake transfers game piece to shooter/storage. Smooth handoff is critical!

💡 Intake Design Tips

Make it wide enough to easily capture pieces
Add compliance (springs, surgical tubing) for better grip
Test with actual game pieces, not just CAD!
Keep it simple - complexity = failure points

Step 5

Shooter Systems

Shooters score game pieces into goals. Three main types: flywheels, catapults, and linear punchers.

Shooter Types:

⚡ Flywheel Shooter

Most accurate and controllable. Wheels spin at high speed to launch game pieces.

Uses 2-4 NEO/Falcon motors
Variable speed for different distances
Best for balls and discs
Requires PID control for consistency

🎯 Catapult Shooter

Stores energy in springs or pneumatics, releases quickly.

Simpler than flywheels
One shot at a time (slower cycle)
Good for high arc shots
Uses surgical tubing or pneumatic cylinders

Flywheel Design Steps:

Calculate Required Exit Velocity
Use physics! Measure max shooting distance and goal height. Calculate required velocity using projectile motion equations.
Choose Wheel Size and Motor
Typical: 4" compliant wheels with NEO motors at 1:1 or 2:1 gear ratio. Use JVN Calculator!
Compression and Hood Angle
Game piece should be compressed between flywheels. Adjustable hood angle controls trajectory.
Add Vision Alignment (Optional)
Use Limelight or PhotonVision to automatically aim at goal. Greatly improves accuracy!

⚠️ Shooter Challenges

Inconsistent shots - check wheel RPM stability
Jamming - ensure proper feeding mechanism
Motor overheating - allow cool-down time
Not enough power - use multiple motors

Step 6

Gearbox Design & Motor Selection

Motors provide power, gearboxes convert that power to the speed and torque you need.

Common FRC Motors (2025 Updated):

🆕 NEO Vortex (REV) - NEW for 2025! High-power brushless motor with through-bore rotor and interchangeable shaft system. Works with SPARK Flex and REV ION System.
NEO Brushless V1.1 (REV) - Modern, powerful, efficient. Great for drivetrains and flywheels. Compatible with SPARK MAX.
Kraken X60 (WCP) - High-performance brushless motor. NEW integration kits for 3in MAXSwerve available in 2025.
Falcon 500 (CTRE) - High power, integrated encoder. Popular for swerve and shooters.
CIM Motor - Classic workhorse. Reliable for drivetrains (consider upgrading to brushless for 2025).

🆕 2025 Motor Highlights

NEO Vortex features dockable controller for easy mounting
New Gear Ratio Upgrade Kit for REV ION with 5 extra high-speed ratios
MAX 180 Degree Gearbox allows motor flipping for flexible design

Gear Ratio Basics:

Understand Speed vs Torque Trade-off
Higher gear ratio = more torque, less speed. Lower ratio = more speed, less torque.

Example: 10:1 ratio means output shaft rotates 1 time for every 10 motor rotations.
Use Online Calculators
Don't guess! Use these essential tools:
- JVN Design Calculator - Drivetrain speeds and motor loads
- ReCalc - Modern calculator for all mechanisms
ReCalc - Mechanism Calculator
COTS Gearboxes vs Custom
For rookies: Buy COTS (Commercial Off-The-Shelf) gearboxes from:
- VexPro Versaplanetary
- AndyMark Toughbox
- REV MAXPlanetary
Custom gearboxes are advanced - wait until 2nd or 3rd year!

⚙️ Typical Gear Ratios

Drivetrain: 8:1 to 12:1 (for 12-15 ft/s top speed)
Intake: 3:1 to 5:1 (moderate speed)
Flywheel: 1:1 to 2:1 (high speed)
Elevator/Climber: 15:1 to 50:1 (high torque)

Step 7

Manufacturing & Assembly

Turning your CAD design into real parts! Understanding manufacturing constraints early prevents problems later.

Common Manufacturing Methods:

🔧 Hand Tools (Drill, Saw, File)

Essential for every team. Can build entire robots with just these!

⚡ Bandsaw & Miter Saw

Cut box tubing and aluminum stock quickly and accurately.

🎯 CNC Mills & Routers (Advanced)

Computer-controlled precision cutting. Great for complex parts but not required!

Design for Manufacturing (DFM):

Use Standard Hole Sizes
#7 (0.201"), 1/4", and 1/2" holes are most common. Design holes for standard drills you have!
Minimize Custom Parts
Use COTS parts whenever possible. Every custom part = more time and potential errors.
Tolerance and Clearance
Add 0.020"-0.030" clearance for slip fits. Parts WILL have manufacturing errors!
Create Assembly Instructions
Export assembly views from CAD. Number parts and create bill of materials (BOM).
Test Fit Early
Make prototypes! Use cardboard, wood, or 3D prints to test mechanisms before final parts.

⚠️ Safety First!

Always wear safety glasses in shop
Get trained on each tool before using
Tie back long hair, remove jewelry
Never work alone - buddy system!

🎉 You're Ready to Build!

You now have the fundamentals of mechanical design! Remember: simple, reliable mechanisms beat complex, fragile ones. Start with basics and iterate!

Mechanical Design Guide