Explore the gears, linkages, and drivetrain layouts that bring robots to life.
Animated spur gears meshing at a 2:1 ratio — the driven gear has twice the teeth of the driver.
Four-Bar Linkage
A mechanism is a collection of rigid bodies connected by joints that converts input motion into a desired output motion. In robotics, mechanisms are the bridge between motors and the actions a robot performs — from driving wheels to lifting arms. Understanding how gears mesh, linkages articulate, and drivetrains distribute power is essential for designing robots that move with precision and reliability.
Gears transmit rotary motion between shafts. The relationship between two meshing gears is defined by the gear ratio, which determines the trade-off between speed and torque.
Gear Ratio = Driven Teeth / Driver Teeth
Example: A 60-tooth driven gear meshed with a 20-tooth driver gear → 60 / 20 = 3:1 ratio. The output shaft turns 3× slower but with 3× the torque.
The simplest and most common gear type. Teeth are straight and parallel to the axis of rotation. Ideal for parallel shaft arrangements. Easy to manufacture but can be noisy at high speeds.
Cone-shaped gears that transmit motion between intersecting shafts, typically at 90°. Used when you need to change the direction of a drive shaft. Common in differential drives.
A worm (screw) meshes with a worm wheel to achieve very high gear ratios in a compact space. Naturally self-locking — the wheel cannot back-drive the worm — making them ideal for lifts and winches.
A sun gear, planet gears, and a ring gear work together in a compact, coaxial arrangement. Offer high torque density and multiple gear ratios from one assembly. Common in servo gearboxes.
Beyond gears, robots rely on a variety of mechanisms to convert and redirect motion.
Four rigid bars connected by four revolute joints forming a closed loop. By varying the link lengths, you can create crank-rocker, double-crank, or double-rocker motion. Widely used in robot arms, claws, and leg mechanisms for walking robots.
Converts rotary motion into linear motion (or vice versa). A rotating crank drives a connecting rod that pushes a slider back and forth. Used in piston-style actuators and punching mechanisms.
A rotating cam with a profiled surface pushes a follower along a precise path. The follower's motion profile (rise, dwell, return) is determined by the cam's shape. Useful for pick-and-place timing and indexing.
Transmits motion between shafts that may be far apart. Timing belts (toothed) prevent slippage and are used in 3D printers and linear motion stages. V-belts absorb shock loads. The ratio works like gears: larger driven pulley = more torque, less speed.
The drivetrain determines how a mobile robot moves across a surface. Each layout offers different trade-offs in maneuverability, speed, complexity, and traction.
Two independently driven sides (left and right). Turning is achieved by running the sides at different speeds. Simple, durable, and provides excellent pushing power. Skid-steering can wear wheels on hard surfaces.
Four wheels with angled rollers allow omnidirectional movement — forward, sideways, and diagonal — without rotating the chassis. Complex to control but offers unmatched maneuverability in tight spaces.
Each wheel module can independently steer and drive. Combines the power of tank drive with the agility of mecanum. The most complex drivetrain to build and program, but considered the gold standard in competitive robotics.
Two driven wheels on a common axis with one or more caster wheels for balance. The simplest mobile robot drivetrain. Turns by varying wheel speeds. Common in educational robots and autonomous guided vehicles (AGVs).
When modeling gears in CAD, use simplified representations (cylinders with pitch-circle diameters) for assembly-level work. Full tooth profiles are only necessary for manufacturing drawings or finite-element analysis. This keeps your assemblies lightweight and responsive.
Cam & Follower Mechanism — a rotating cam with harmonic profile drives a flat-face follower through its guide.