A bit of history will make understanding a little easier.
If one tries to answer the questions regarding who came up with the idea of a steam engine, or the year the first was built, the point will be argued. But, in actuality, the answer is not in the 18th or 19th centuries. The first steam “engine” was conceived by and made by Heron of Alexandria. It was a simple device, consisting of a hollow sphere that rotated on an axis of pipe, that pipe supplying vapor to the sphere from a container of boiling water underneath. The sphere was fitted with two exhaust pipes that rotated the ball as would two jets do. This was more than 2,000 years ago. Just think. If the next step of putting this on wheels to perform work or even remaining stationary, the industrial revolution would have happened 1,850 years before it did. How would our world appear today?
Since we are speaking only of classification, operation and the details of how they work won’t be covered here in depth. A “saturated steam” engine, also called a “soaker,” is as its name implies, simple steam under not too high pressure. As technology increased, the “grate area” of the firebox increased, allowing for more heating area. Boiler size increased as well. It was these larger engines that became the super-heated variety. There were “feed water heaters” that pre-heated the water before it was put into the boiler above the firebox. As a result, higher steam pressure was achieved, resulting in more power from the expanding steam when put into the cylinders.
A single expansion engine, also called a “simple” engine, expands the steam in the cylinders and that steam is exhausted through the smoke box and smoke stack. A compound engine, expands the steam twice. The cylinders are two different sizes, one low pressure and the other high pressure. Steam is expanded first when fed to the low pressure cylinders, then their exhausted steam is expanded a second time in the high pressure cylinders before being exhausted through the smoke box and stack.
In a non-articulated rigid engine, the high and low pressure cylinders are on opposite sides of the engine. This arrangement is called the “cross compound” engine.
In an articulated locomotive, where there are two sets of cylinders and drivers under one boiler, the high and low pressure cylinders run in tandem, with the low pressure cylinders at the front and the high pressure cylinders behind. The idea came from Anatole Mallet (pronounced Mal-lee) and was much more efficient for the use of fuel and water. As a result, most times articulates are called Mallets, although the first articulates were the only true Mallets, in most cases. Even so, the system was improved by Mr. Vauclain of the Baldwin Locomotive works, and it was actually his design that resulted in the lion’s share of U.S. built compounds. By the time of the end of their service life, almost all the compounds were re-built as simple expansion engines.
But in the end, it was the wheel arrangements that ultimately determined which class a steam locomotive was tagged with. The earliest days saw many odd wheel arrangements but over time these were improved upon and the result was the most common types of wheel arrangements that defined the age of modern steam locomotives.
When speaking of the wheel arrangements they are expressed in a series of numbers, the first representing the number of wheels making up the leading or “pony truck,” the number of drivers or powered wheels, and the number of wheels in the trailing truck. Engines that had neither lead nor trailing truck wheels had a “0" in place of a number. As an example, most engines in yard service had no lead or trailing trucks, usually with six or eight drivers. One with six drivers then would be an 0-6-0 and with eight an 0-8-0. these engines were never really given a class designation, beyond “switcher,” aka a “goat,” or a “dockside,” the latter usually being a “tank” engine, carrying its fuel and water with it, as opposed to being in a trailing “tender.”
Many railroads assigned an engine to a class of their own designation, but the common names of the most common types, with wheel diagrams and names (where multiple names are shown, the most common appears first), are as follows:
0-4-4 oOOoo Forney 4-coupled
0-6-4 oOOOoo Forney 6-coupled
2-4-2 oOOo Columbia
2-6-0 oOOO Mogul
2-6-2 oOOOo Prairie
2-8-0 oOOOO Consolidation
2-8-2 oOOOOo Mikado
2-8-4 oOOOOoo Berkshire or Kanawha
2-10-0 oOOOOO Decapod
2-10-2 oOOOOOo Santa Fe
2-10-4 oOOOOOoo Texas
4-2-0 ooO Six-wheeler
4-2-2 ooOo Bicycle
4-4-0 ooOO American
4-4-2 ooOOo Atlantic
4-6-0 ooOOO Ten-wheeler
4-6-2 ooOOOo Pacific
4-6-4 ooOOOoo Hudson or Baltic
4-8-0 ooOOOO Mastodon
4-8-2 ooOOOOo Mountain
4-8-4 ooOOOOoo Northern, Niagra, Greenbrier or Dixie
4-10-2 ooOOOOOo Southern Pacific or Overland
4-12-2 ooOOOOOOo Union Pacific
Articulated:
2-6-6-6 oOOO OOOooo Allegheny
2-8-8-2 oOOOO OOOOo Chesapeake
4-6-6-4 ooOOO OOOoo Challenger
4-8-8-4 ooOOOO OOOOoo Big Boy
2-8-8-8-2 oOOOO OOOO OOOOo Triplex
2-8-8-8-4 oOOOO OOOO OOOOoo Triplex
The triplexes were few in number, built by Baldwin Locomotive works, for eastern coal hauling roads, like the Erie. Cumbersome, nearly impossible to counter balance due to their complexity and as a result, twenty miles per hour was about tops. But, it could do the twenty miles per hour all day long, up hill and down, dragging 12,000 tons of coal around.
There are five well known types of steam engines that stand in a class all their own:
1. “Camel Back”: Easily recognizable because the locomotive cab is near the middle of the boiler, where would have been found the engineer and head brakeman. The fireman was still resigned to his plight however, still positioned at the end of the locomotive behind the fire box.
2. “Heisler”: These were “geared” locomotives that were used in logging operations. Equipped with two cylinders ahead of the locomotive cab, one on each side, at a 45 degree angle to the center point underneath the boiler. The pistons turned a crank which in turn ran a drive shaft that powered the wheels through gear work, much the same way the drive train in your rear wheel drive automobile. In addition, the pairs of drivers on the two trucks had conventional “side rod” connections between the wheels. Probably the first Hybrid vehicle, in a sense.
3. “Shay”: These too were gear driven, but the cylinders were mounted vertically in front of the locomotive cab on the engineer’s (right-hand) side. They typically had either two sets of gear driven drivers or three sets. These were much larger and heavier than either the Heisler or Climax, up to 80 tons for the three truck variety. Some survive and still operate at both the Cass Scenic Railway or Roaring Camp and Big Trees Rail Road.
4. “Climax”: Another geared logging locomotive, but different from the Heisler in that the cylinders were outboard and ahead of the cab, but their 45 degree downward angle was parallel to the engine, front to rear.
5. “Cab Forward”: Unique to the Southern Pacific, the locomotive cab was located at the front of the engine. With differing wheel arrangements over the years, the first were compounds, although they were re-built to simple engines before being scrapped, with later engines being simple expansion, with the final development of wheel arrangement of 4-8-8-2. These engines literally ran backwards. The cab was located to the front so that crews wouldn’t suffocate from the noxious fumes from the engine’s exhaust when traveling through the numerous tunnels and snowsheds over the Donner Pass route through the Sierra Nevada mountains. At one time, forty miles of track was under snowshed.
This prompted many more than one or two 'boomers' demanding their time after one trip between Roseville, California and Sparks, Nevada, usually saying they would be, "...Damned if I'll railroad in a (insert the expletive of your own choosing here) barn!"
2007-07-10 05:41:07
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answer #1
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answered by Samurai Hoghead 7
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