Keeping Us in Line: Train Tracks

Railway Transport

As early as 1550, pragmatic Germans constructed and used wooden railway systems, reasoning that horse-drawn wagons and carts could travel more easily and quickly over wooden rails than dirt roads. By the late 1700s, iron wheels and rails had one-upped wooden ones.

But it wasn't until the steam locomotive was invented in 1797 in England that the railroad as we know it began to take shape.

The job of the locomotive is to change the chemical energy from the fuel (wood, coal, diesel fuel) into the kinetic energy of motion. The steam locomotive lasted for about a century, but was eventually replaced by the diesel locomotive, a mighty mechanical wonder that may consist of a giant engine along with electric alternators or generators to provide electrical power to the train. Many trains intersperse multiple locomotives throughout their lineup to increase and distribute the power.

Operators control the train by using the throttle, reversing gear and brake. The throttle controls the speed of the locomotive. The reversing gear enables the locomotive to back up. The brake allows the locomotive to slow and stop. Regardless of the type, locomotives use air brakes and hand brakes to stop the engine. Air brakes use high-pressure air to drive the brake foot against the wheel. The friction between the brake pad and the wheels slows the wheels' motions. A mechanical hand brake is also used in case the air brakes fail (usually when there's insufficient air pressure to drive them).

All railroad cars have an undercarriage that contains wheels and a suspension system to buffer the ride. On each end of the undercarriage, couplers, which are like hooks, connect the cars.

What's on top of the undercarriage depends upon the type of railroad car, and there are several.

• A boxcar is a basic box into which crates of goods can be piled up.
• An ore car has an open top and carries coal or other mineral ore such as bauxite.
• A tank car holds liquids, usually chemicals such as chlorine and ammonia.
• Flat cars can hold bulky irregular items on them, such as construction equipment or spools.
• Trailer cars can transport automobiles.
• Container cars are filled with boxed containers of various materials. Often, containers can be double-stacked on these cars.
• Passenger cars, of course, hold people. Some have glass-enclosed viewing areas on top, and some may even be sleeper cars for long trips.

Keeping Us in Line: Train Tracks

A railroad track consists of two parallel steel rails set a fixed distance apart, called the gauge. The standard gauge is 4 feet 8.5 inches (1,435 millimeters). The rails are connected to each other by railroad ties (called sleepers in Europe), which may be made of wood or concrete. The rails are usually bolted to the ties. The ties are set into the loose gravel or ballast. Ballast often consists of loose stones that help transfer the load to the underlying foundation. The ties "float" on the ballast and the weight of the track keeps them stabilized.

When rail workers are laying train tracks, they often use a flat-bottom steel rail that resembles the steel I-beam girders of construction. The rail has a wide base or foot, a narrow web and a head (wider than the web, but not as wide as the foot). The weights of the rails vary from 80 to 160 pounds (36 to 73 kilograms) per yard depending upon the type of train operating on the tracks and the country. Segments of rail track may connect to one another by bolted plates called fishplates, but most modern rail segments are welded together to provide a smooth ride.

Steel tracks can be straight or curved to steer the train since steel is easily bent into shape. Depending upon the topography, some curves may be slightly angled or banked to help the train stay on the track as it negotiates the curve. At various points along the track, rails may have switches, which can move a train from one track to another. Switches and accompanying track are important for controlling traffic. For example, when two trains are operating on the same track, a switch can allow one train to pull off to a holding track while the other one passes. A switch also can change a train's direction like moving it from a north-south track to an east-west one. Many railroad stations have switching yards where trains are assembled and moved onto various tracks.

Упражнение 1

Переведите на русский:

Steam/diesel locomotive, throttle, reversing gear, undercarriage, the suspension system, buffer, couplers, a railroad car (boxcar, ore car, tank car, flat car, trailer car, container car), the gauge, ties/sleepers, ballast, a flat-bottom steel rail, a girder (base/foot, web, head), fishplates, are welded together, switches, accompanying track, switching yards.

Date: 2016-01-14; view: 1036