For engineers who already know the math—but still lose projects. For the last few years, I’ve been sharing technical guides here on Mechanical Design Handbook —how to size a motor, how to calculate fits, and (as you recently read) how to choose between timing belts and ball screws. But after 25 years in industrial automation, I realized something uncomfortable: Projects rarely fail because the math was wrong. They fail because: The client changed the scope three times in one week. A critical vendor lied about a shipping date (and no one verified it). The installation technician couldn’t fit a wrench into the gap we designed. University taught us the physics. It didn’t teach us the reality. That gap is why I wrote my new book, The Sheet Mechanic . This is not a textbook. It is a field manual for the messy, political, and chaotic space between the CAD model and the factory floor. It captures the systems I’ve used to survive industrial projec...
At first glance, it almost looks organic. The repeating motion resembles a person performing squats, or a stylized bipedal mechanism flexing through a rhythmic cycle. Behind that visual impression is a deterministic planar mechanism: nine moving links driven by a single continuously rotating crank, coupled through multiple interconnected closed loops. Nine moving links coordinated by a single input crank, simulated in MechanicSim2D. An intuitive reaction to seeing so many moving members is to assume that high link counts create chaotic or under-constrained motion. In kinematics, the opposite is often true: joints impose geometric constraints, and closed loops can reduce the number of independent coordinates when those constraints are independent. Advertisement Planar Mobility: The Kutzbach Criterion with Nine Moving Links In mechanism design, an unconstrained rigid body in planar space has three i...