Locomotives or as those who worked
the woods called them, Locos
The locos that worked in the woods along the Mendocino Coast were of two main types, rod or piston and gear driven. The piston driven locos are classified using the Whyte system. The geared locos are identified by their manufacturers; Shay, Climax and Heisler.
Piston Driven Locos
The Whyte notation for classifying steam locos by wheel arrangements was devised by Frederick Methvan Whyte and came into use in the early 20th century. Whyte's system counts the number of leading wheels, then the number of driving wheels, and finally the number of trailing wheels, this being the common pattern of the conventional steam locomotive. Thus, a locomotive with two leading axles (and thus four wheels) in front, then three driving axles (six wheels) and followed by one trailing axle (two wheels) is classified as a 4-6-2.
It's important to stress that wheels, not axles, are what is counted in this system. Other classification schemes in use elsewhere (such as in France) count axles.
An Articulated locomotive is one or more engine units which can move independent of the main frame. This is done to allow a longer locomotive to negotiate tighter curves. Articulated locomotives are generally used either on lines with extreme curvature—logging, industrial, or mountainous railways, for example—or to allow very large locomotives to run on railways with standard axles in between powered axles, are just written by adding extra numbers in the middle; each number represents a grouping of wheels. Thus a Mallet (see below) is written under this modified Whyte notation as a 2-6-6-2; there are two leading axles, one group of three driving axles, another group of three driving axles, and then two trailing axles.
In addition the suffix 'T' is sometimes used to indicate a tank loco (otherwise, a tender locomotive is assumed). In American practice, most wheel arrangements in common use were given names. Below is a list of the most common wheel arrangements used along the Mendocino Coast: in the illustration, which should be read left to right, with the front of the locomotive to the left, small o is a carrying axle, and a big O is a driving axle.
|OO||0-4-0||Four-coupled||Click here to learn/see more|
|OOo||0-4-2||Click here to learn/see more|
|OOO||0-6-0||Six-Coupled||Click here to learn/see more|
|oOOo||2-4-2||Click here to learn/see more|
|oOOOo||2-6-2||Prairie||Click here to learn/see more|
|oOOOO||2-8-0||Consolidation||Click here to learn/see more|
|oOOOOo||2-8-2||Mikado||Click here to learn/see more|
|ooOO||4-4-0||American or Eight-Wheeler||Click here to learn/see more|
|ooOOO||4-6-0||Ten-Wheeler||Click here to learn/see more|
|oOOO-OOO-o||2-6-6-2||Mallet||Click here to learn/see more|
The geared locomotive was developed to meet the unique challenges of the logging industry. A number of different designs were tried, three of which achieved major success with sales of over 1,000 each.
The key features of the three successful designs are:
- Relatively small wheels mounted in freight car type trucks enabling a very short turning radius.
- The two or three (and in a few cases four) trucks were spread out under the locomotive to distribute the weight over the greatest possible length of track.
- The engine was coupled to the wheels and axels via drive shafts and gears. All wheels were driven to achieve the greatest possible traction over the maximum possible length of track. The diagram right shows how the Climax was geared:
- There was a gear reduction between the engine and drive axels on the order of 2:1 which achieved a corresponding increase in torque that was further aided by the small wheels --- an effect similar to driving an auto in low gear. This is a classic torque-speed trade off which was appropriate for the rough roadbeds --- 10 mph was really flying.
- All the geared locomotives were relatively light in comparison to rod locomotives of the era, ranging from about 10 tons initially to over 100 tons in the early 1900s. By comparison, the last of the big rod locomotives of the 1940s were over 500 tons.
The vast majority of geared locomotives were built to one of three distinct designs, whether licensed and official, or clones built after the expiration of key patents. Of the types, the Shay locomotive as the most numerous and best known. Climax and Heisler were the other two designs. The Geared Steam Locomotive Works site gives an in-depth review of the three different types.