The Crane Operator's Tricks and other Shenanigans with a Pendulum

Published

February 18, 2022

Author(s)

Stephan Schlamminger, Leon Chao, David B. Newell, Vincent Lee

Abstract

The dynamics of a swinging payload suspended from a stationary crane can be described as a simple pendulum, typically an unwelcome phenomenon on a construction site. An experienced crane operator can deliver a swinging payload and stop dead on target in a finite amount of time by strictly modulating the speed of the trolley. Generally, a series of precisely timed go-stop movements of the trolley are implemented to damp out the kinetic energy of the simple harmonic oscillator. Here, these mysterious crane operator's tricks will be revealed with a mathematical model, ultimately expanding to a generalized form capturing the case where the load is initially swinging. Finally, this theory is applied to a scientific experiment using a torsion balance to measure $G$, the universal gravitational constant responsible for the swinging of the crane's payload in the first place.

Citation

American Journal of Physics

Volume

90

Issue

3

Pub Type

Journals

Download Paper

https://doi.org/10.1119/10.0006965

Local Download

Keywords

pendulum, control theory, damping, gravitational constant

Citation

Schlamminger, S. , Chao, L. , Newell, D. and Lee, V. (2022), The Crane Operator's Tricks and other Shenanigans with a Pendulum, American Journal of Physics, [online], https://doi.org/10.1119/10.0006965, https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=932195 (Accessed October 8, 2025)