Measuring the hydrodynamic forces or water velocities beneath breaking waves is a difficult task. A simple way to find the maximum forces and velocities that a location has experienced is to use these mechanical dynamometers. Much like the maximum-recording spring scales used to measure fish, these provide a single measurement of the largest force experienced by a test ball since the last time they were read.

These devices are robust, inexpensive and simple to construct. The following pages will explain how to build and use them.