Milepost 170
When I'm discussing steam locomotives here, I often use terms like 0-6-0 or 2-8-8-2 well in case you are wondering...
The numbers refer to the number of wheels on the locomotive from front to rear. The system was developed by Frederick Whyte as an easy way to identify and differentiate between locomotives of differing wheel arrangements. That system is still commonly accepted today here in the States, but over in Europe, it was more common to count the axles instead of the wheels.
The picture at the top of this entry is of a Pennsylvania locomotive. If you look closely, from front to back, you will see that there are four small wheels (remember to count both sides), six larger driving wheels followed by two smaller trailing wheels. So that makes this particular locomotive a 4-6-2. Simple enough, no?
Two additional parts of the Whyte classification system are a "+" and a "T." The + was used to indicate that a locomotive was articulated; that it had two sets of drive wheels. The T was used to designate a loco that didn't have a tender. Instead, it simply had a larger space on the back of the loco for extra fuel & water. Generally, you will see the T used but more often than not, the + isn't nearly as common. Most articulated locos are just listed like 2-8-8-2 instead of 2-8+8-2.
Most common wheel arrangements also had a nickname as well. These were not official and in some cases, varied from road to road, but in general, they were commonly accepted. The honor of designating a particular wheel arrangement nickname usually went to the railroad that first used it. But even that wasn't always the case; some of the names just evolved and stuck.
Finally, one other "general" observation... locomotives whose classification started with a 0 often were engines that worked in railroad yards and were specifically given the task of switching other engines & cars. Those that began with a 2 were often assigned to freight duty. Finally, those that started with a 4 were most likely to be found in passenger service. As I said, this was kind of a rule of thumb, not a cast in stone fact.
Yard engines slowly plodded along. they didn't need a front set of wheels due to their slower speed of operation. The freight engines which usually started with a 2 moved faster but not as fast as the passenger engines. The larger 4-wheel lead truck assisted the locomotive in staying on the tracks at a higher speed and also provided a more stable ride.
Some common wheel arrangements and their nicknames are as follows:
0-4-0 generally a yard switcher.
0-6-0 another larger switcher type.
2-6-0 Mogul. A small freight engine.
2-8-0 A Consolidation.
2-8-2 A Mikado. This one is interesting as the name Mikado came from Japan. During World War II, some actually referred to these as "MacArthurs," but the term really didn't stick for long.
4-4-2 An Atlantic. This was probably the first more modern passenger engine.
4-6-2 A Pacific. A much larger, more powerful engine that saw service as both a freight and passenger engine.
4-8-4 Generally referred to as a Northern but on the New York Central System, they were called Niagaras. Like I said, these were sometimes called different names by different railroads.
2-8-8-2 or 2-8+8-2 An articulated locomotive called a Mallet, named after the French inventor who developed them. They were very large freight engines.
4-8-8-4 The Big Boy. These were among the largest engines ever built. They were used in high speed freight service out West on the Union Pacific system.
There are several others, but this will give you an idea of what all of these numbers mean. Next time, we can talk about diesel locomotives; they had their own classification system but it is a lot simpler. Until then...
dlm
