Shafts

Shafts are rotating elements used to transmit torque through a robot’s mechanisms. In FRC, different shaft geometries are used depending on how securely components must transfer motion and how much load the system experiences.

Common Shaft Types

1/2" Hex Shaft

• Most common FRC shaft type
• Torque is transmitted through flat faces
• No slipping when used with matching hubs
• Easy to assemble and align

3/8" Hex Shaft

• Smaller, lighter hex shaft option
• Used in compact or low-load mechanisms
• Easier to package in tight designs
• Lower torque capacity than 1/2" hex

1/2" Round Shaft

• Smooth cylindrical shaft
• Requires keys, pins, or set screws for torque transfer
• Can slip if not properly constrained
• Used when free rotation or simple pivots are needed

Spline XL Shaft System

Spline XL is a high-torque shafting system used in FRC for demanding applications.

Key Features:

• Multiple splines (teeth) around the shaft
• Very high torque capacity
• Prevents slippage under heavy load
• Allows precise, repeatable component alignment

Why Teams Use It:

• Handles extreme drivetrain loads
• More robust than hex shafts in high-stress systems
• Reduces wear from repeated high-torque cycles
• Improves long-term reliability

How They Relate

• Round shaft → simplest, lowest torque transfer (needs retention features)
• 3/8" hex → compact, moderate torque, space-saving option
• 1/2" hex → standard balance of strength and usability
• Spline XL → maximum torque capacity and reliability

As load requirements increase, teams typically move from round → smaller hex → 1/2" hex → spline-based systems.

Common Applications

• Drivetrains (1/2" hex, Spline XL)
• Intakes and rollers (3/8" and 1/2" hex)
• Elevators and arms (1/2" hex, Spline XL)
• Light pivots and mechanisms (round shaft)

Key Idea

Shaft selection depends on torque, packaging, and reliability needs. 3/8" hex is a compact option, 1/2" hex is the standard, round shafts require additional retention, and Spline XL is used when maximum torque capacity and durability are required.