One of things I like about model railroading is you always can learn something new, even after being in the hobby for many years.
I have recently read one my old issue train magazines from this springs trains show titled "Model Trains", issue Spring 1957 costing 35 cents! A foot tall stack of old and some new CTT and OGR magazines is all I purchased this trip. The spring 57 issue has an article featured on the from cover, " Tank engines and tank-engine railroads".
Sorry I could not rotate!
After seeing some of the pictures, it seams a tank engine is what many of use now call a dockside switcher. Reading the article shows the age of steam versatile tank engine is a small 10 to 60 ton or so, usually a 0-4-0 or 0-6-0 engine that carries its own fuel and water and does not have a separate tender. It carried coal, wood or oil in a bunker behind the cab and water was kept in an inverted U-shaped saddletank that straddled the boiler (hence the term saddletanker is also used), or in side tanks mounted on the running boards. It is operated by one engineer.
Again no rotation possible
The reason tank engine may be a better term than dockside engine as dockside use was only a small percentage of its use. The tank engines were made by many manufacturers, were cheap and lightweight, made in any gauge, and were used anywhere a small job had to be done. These include mining, logging, quarries, industrial, mt switching, big railroad roundhouses and shops for car sorting and dead road engine movement to turntables, passenger trains, short railroads and many more.
One of the most famous tanker engines was the "Little Joe", 0-6-0T used by B&O on Pratt Street Line in downtown Baltimore until the GE 44 ton diesel came along.
The tanker engine was pointed to as a good choice to get into model railroading with a small layout and at low expense.
My better tanker engine (below) is a Mikes Train House MTH 840, 0-4-0. It is all cast metal and heavy with couplers on each end. It is geared way low and has a low top speed, ideal for switching. I always called it a dockside switcher.
Another tanker engine I have (below) is the Lionel 8905, 0-4-0, dc operating, light weight, cheapie plastic and only has one coupling. I have added a full-wave bridge rectifier to allow forward running with ac but no reverse unless I add a dpdt reversing/forward switch. I could add a front coupling but doubt I would run it much as it will not pull much.
After learning how versatile and popular the tank engine is I will now run my MTH 840 much more often.
Charlie