I’m not sure that it can be called succinct, but Mainline Modeler did a three-part series on trucks.
I’m going to attempt to scan the pages, and will post them here if they appear to be legible.
While our models tend to show two- or three-spring versions in cast sideframes, or even ones with actual springs, such as are offered by Kadee, many of the real ones had spring packages with many more springs that weren’t readily visible.
Here are the scans of the Mainline article (Click on the photos for a larger view)
