Four-Bar Mechanisms, Straight-Line Generators & Kinematic Chains
Before computers, before electricity, mechanical linkages solved problems that seemed impossible. Watt needed straight-line motion for his steam engine. Peaucellier proved it could be done exactly. Chebyshev spent decades optimizing approximations. These elegant mechanisms convert one type of motion into another using nothing but rigid bars and pivot joints. Drag, adjust, and watch kinematics come alive.
The great challenge of the 18th and 19th centuries: how do you generate a perfect straight line from circular motion? These linkages answer that question with increasing precision.
James Watt's 1784 mechanism: two rockers connected by a coupler whose midpoint traces an approximate straight line. Still used in car suspensions today.
Pafnuty Chebyshev's 1850 design with the classic 2:2.5:1 ratio. Longer straight-line segment than Watt's, with both pivots on the same side.
The first exact straight-line mechanism (1873). Seven bars use circle inversion to convert circular motion into a mathematically perfect straight line.
Fundamental mechanical linkages that form the building blocks of machines, engines, and industrial equipment.
The most fundamental planar mechanism. Adjust all four link lengths and watch the Grashof condition determine whether full rotation is possible. Coupler curve traced in real time.
The engine inside every car: a rotating crank drives a sliding piston. Adjust crank radius, rod length, and offset. Real-time position and velocity graphs.
Converts continuous rotation into precise intermittent steps. Choose 3 to 8 slots and watch the pin engage and disengage. Used in film projectors and watches.
Specialized mechanisms that demonstrate sophisticated kinematic principles—from scaling to walking to mathematical theorems.
Move the input stylus and watch the output draw a scaled copy. Adjustable scale factor from 1x to 4x. Used for map copying, engraving, and even railroad power pickup.
Joe Klann's 1994 walking mechanism: a single rotating crank drives legs that mimic an animal's walking gait. Choose 1 to 6 legs and watch it stride.
The Roberts-Chebyshev theorem (1875): every four-bar coupler curve can be generated by three different linkages. Watch all three trace the same curve simultaneously.
Build your own linkages from scratch. Place joints, connect bars, add motors, and trace paths. Includes presets for four-bar and slider-crank mechanisms.