A Steam "Tutor"

Though it was the beloved steam engine that contributed so greatly in moving this country forth by connecting the East to the West, many of the younger generations have never experienced the thrill of seeing a full-scale one in operation.  So just what is a "Steam Engine" and what do their numbers stand for?"

Steam locomotives are known by their wheel arrangements following the "Whyte Classification System" which identified these engines by the number of wheels they had.

For Example:

 4-4-0

The first place indicates the number of small wheels which lead the locomotive, known as leading or pilot wheels.  These wheels support the weight of the cylinders and smoke box at the front of the locomotive and give the locomotive stability as it travels.

The second place shows the number of wheels which actually drive the locomotive, and so are called driving wheels.  These wheels are larger than either the leading or trailing wheels and besides propelling the engine, are strategically situated to support the locomotives main weight.

The third place usually gives the number of small wheels which trail the driving wheels, and are named trailing wheels.  They can support the weight of the boilers firebox in the cab.

Sometimes a locomotive's classification number will have four number places.  In this case, the third place gives the number of wheels in the second set of driving wheels, and the fourth place shows the number of trailing wheels.

Most Locomotive Types Have Names

Most locomotive types are also known by a name.  For example, the 4-4-0 type is commonly called an "American".  Other 19th century classes of locomotives include the 4-6-0 "Ten-wheeler", the 2-6-0 "Mogul" and the 2-8-0 "Consolidation".

Here is a compilation of wheel arrangements with their corresponding Nicknames and Use: