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.