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Trains Big Boy
Railroading Glossary
The following glossary is arranged alphabetically with each term catalogued by first letter. Select a letter below to begin.
A | B | C | D | E | F | G | H | I | J | K | L | M
N | O | P | Q | R | S | T | U | V | W | X | Y | Z
Pantograph
Roof-mounted device on an electric car or locomotive that collects electric current from overhead catenary; can be raised or lowered.
Parasitic load
In a diesel engine, any of the loads or devices powered by the prime mover that do not contribute to tractive effort, such as air compressor, traction motor blower, and radiator fans.
Parmelee Transfer
The firm employed by a committee of railroads to provide station-to-station transfer services for passengers (and their baggage) traveling through Chicago. Founded by Frank Parmelee in 1853.
PCC car
Presidents' Conference Committee car, a type of streamlined streetcar introduced in the 1930's. It was the product of a special committee of streetcar-line presidents.
Per diem
Latin for "per day". The daily rental fee paid by one railroad to a car owner for the use of one or more cars.
Percent
The measure of slope or inclination of track. See Grade.
PFE
Pacific Fruit Express.
Pickup
The addition of one or more cars to a train, especially when added between the train's originating and destination terminals.
Piggyback
The transportation of highway truck trailers or containers on flatcars (also referred to as TOFC).
Pilot
Employee assigned to a train to assist members of the train crew who are unfamiliar with the territory or rules of a portion of railroad over which the train will be operating.
Plant
Short for "interlocking plant". An arrangement of switches, signals, and their controlling apparatus, all connected to prohibit conflicting train movements.
Plug run
Passenger train of low stature.
Pooling agreement
Under a pooling agreement, railroads are operated separately but all income is divided arbitrarily, irrespective of traffic carried.
Pop valve
The safety or pressure release valve on a steam locomotive boiler.
POTUS
President of the United States. Often used as a code when a special passenger train is carrying the President.
Pound (rail)
The unit of measure of rail size is weight per yard. A 3-foot (1 yard) length of 90-pound rail, for example, weighs 90 pounds.
Powder River Basin
Vast area of rich, low-sulfur coal deposits, generating much rail traffic, in southern Montana and eastern Wyoming.
Power
Locomotives.
Power assembly
The related parts of each cylinder of a diesel engine that can be replaced or repaired without disassembling or removing the entire engine. Includes the cylinder head, cylinder liner, intake and exhaust valves, fuel injectors, etc.
Power stroke
The third piston stroke in a 4-cycle diesel engine. As the rising piston nears the top of the cylinder, and just before passing top dead center, fuel is admitted and burned, because of the high compression temperature, forcing the piston downward. The expansion of the hot gases continues to a point near bottom dead center, when complete release of pressure occurs as the exhaust valves open.
Prime mover
The main power plant in an internal combustion locomotive, as distinct from auxiliary power plants for head-end power, air compressor, and such. The prime mover is the diesel engine which turns the generator that supplies electric current to the traction motors of a diesel-electric locomotive.
Profile
A graphic representation of a railroad line showing the location and severity of grades; vertical and horizontal scales are generally not the same, so as to emphasize the grades.
Proprietary company
A corporation owning all or a controlling portion of the shares of another.
Protect
To be available for service; can refer to persons or equipment.
Puddle jumper
Self-propelled passenger-carrying rail car built in the early 1900's. They were powered by gasoline engines (later diesel engines), which turned an electric generator which fed current to traction motors geared to the wheels. Most were built in the 1910's and 1920's; the last ones were removed from service around 1960. Also called "doodlebugs" and "motor car".
Pull apart
Separation of two sections of rail, usually at a joint.
Pulling faces
The inside surface of the coupler knuckles on a locomotive.
Purchase
Payment of cash outright for all the property of a railroad, which may divide such proceeds as it wishes among its owners and then cease to exist as a corporation.
Pusher
A locomotive added to the rear of a train for a portion of its run to provide extra power to climb a grade. Called a "helper" if added to the front or middle of the train.
Push-pull
A mode of passenger-train operation. In one direction, the train operates conventionally with the locomotive pulling, but in the other direction the train operates in reverse with the locomotive pushing. The car at the opposite end of the train from the locomotive has a control cab for the engineer, eliminating the need for the train to be turned between runs.
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