CH4
Chapter 4 · Overhead cranes
Three motions with different loads: the gravity-driven hoist and the inertia-driven trolley and bridge. Duty groups, dual braking and brake-lift sequencing, anti-sway, skew and load monitoring, power feeds and operator controls.
5 lessons· 145 min
- 01Crane motions and the hoist driveThe hoist, trolley and bridge present different loads; how to size each drive (Tutorial 4.1), and what hook, magnet and grab add to the control.30 min
- 02Duty groups: why two cranes of the same capacity differClass of utilisation, load spectrum and the cube law of fatigue; ISO 4301 groups and CMAA classes; and what the duty group means for the motor and the drive.25 min
- 03Crane braking: mechanical, electrical, and the sequence between themDual braking, a braking resistor rated on the duty cycle, sizing the holding brake (eq. 4.4), two brakes on either side of the gearbox, and brake-lift sequencing.30 min
- 04Anti-sway: the load is a pendulumWhy a trolley start sets the load swinging, the pendulum period, two-pulse input shaping, and why a real anti-sway controller must follow the rope length (Lab IV).30 min
- 05Crane control: drives, skew, load monitoring and interfacesFrom Ward-Leonard to vector drives (Tutorial 4.2), master-slave and gantry skew control, graded overload protection, and how power and commands reach a travelling crane.30 min