Whyte Notations & Wheels
Some of our favorite steam engines are the 2-8-0 at the Georgetown Loop, and the 2-8-2 locos at the Durango and Silverton.
You’ll often see steam locomotives described in this three-part classification, but what does it mean?
Most of the narrow gauge steam locomotives currently in service were built in the early years of the 20th century; the Whyte notation system came into use in December 1900. It describes steam locomotives by their wheel arrangements. The numbers describe the leading, driving, and trailing wheels on the engine.
The Whyte System of locomotive notation
For instance, the Georgetown Loop’s #111 (Baldwin Locomotive Works, 1926) is a 2-8-0. #111 has 2 leading wheels, 8 driving wheels, and no trailing wheels. Otherwise known as a Consolidation engine, #111 was one of the most popular types of steam engines, and being considered the ultimate heavy freight locomotive, 2-8-0 Consolidation locos were built in higher numbers than any other arrangement. (The Colorado Railroad Museum also has two 2-8-0 engines, #318 and #346, which is the oldest operating steam loco in the state. )
Durango and Silverton runs the #473 and the #476 in a 2-8-2 arrangement (called the Mikado locomotive). Mikados are workhorse engines, originally designed for the Japanese market. Used for both passenger and freight trains, the D&S has preserved locos that originally ran on the Rio Grande Line. The Mikado is often considered the iconic steam engine, and a prime candidate for restoration and modern use.
“Klondike Kate” - #4 at Como - is a 2-6-2 or Prairie locomotive, built by the Baldwin Locomotive works in 1912. Prairie locos were commonly used on the US Midwestern farms and fields. It is currently being reconstructed.
Georgetown Loop’s #111, a 2-8-0 Consolidation locomotive.
Each set of wheels has a unique function.
The leading wheels help the locomotive navigate curves and supports the boiler.
The driving wheels are the group of wheels in the center of the locomotive. One of the wheel pairs near the center is connected to the loco’s pistons, and that pair is connected to the other wheels via side rods - this arrangement transfers power to the other wheels.
The trailing wheels support the rear firebox and crew cab; these wheels can be connected to a booster engine for more power.