A hopper car is a type of railroad freight car used to transport loose bulk commodities such as coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

, ore

Ore

An ore is a type of rock that contains minerals with important elements including metals. The ores are extracted through mining; these are then refined to extract the valuable element....

, grain

Cereal

Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...

, track ballast

Track ballast

Track ballast forms the trackbed upon which railway sleepers or railroad ties are laid. It is packed between, below, and around the ties. It is used to facilitate drainage of water, to distribute the load from the railroad ties, and also to keep down vegetation that might interfere with the track...

, and the like. The name originated from the coke

Coke (fuel)

Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

 manufacturing industry which is part of the steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

 industry (see Etymology below).

This type of car is distinguished from a gondola

Gondola (rail)

In railroad terminology, a gondola is an open-top type of rolling stock that is used for carrying loose bulk materials. Because of its low side walls, gondolas are used to carry either very dense material, such as steel plates or coils, or bulky items such as prefabricated pieces of rail...

 car in that it has opening doors on the underside or on the sides to discharge its cargo. The development of the hopper car went along with the development of automated handling of such commodities, with automated loading and unloading facilities. There are two main types of hopper car: open and covered.

Covered hopper

Covered hopper

A Covered Hopper is a railroad freight car. They are designed for carrying dry bulk loads, varying from grain to products such as sand and clay. The cover protects the loads from the weather - dried cement would be very hard to unload if mixed with water in transit, while grain would be liable to...

 cars are used for bulk cargo

Bulk cargo

Bulk cargo is commodity cargo that is transported unpackaged in large quantities. This cargo is usually dropped or poured, with a spout or shovel bucket, as a liquid or as a mass of relatively small solids , into a bulk carrier ship's hold, railroad car, or tanker truck/trailer/semi-trailer body...

 that must be protected from the elements (chiefly rain) such as grain

Cereal

Cereals are grasses cultivated for the edible components of their grain , composed of the endosperm, germ, and bran...

, sugar

Sugar

Sugar is a class of edible crystalline carbohydrates, mainly sucrose, lactose, and fructose, characterized by a sweet flavor.Sucrose in its refined form primarily comes from sugar cane and sugar beet...

, and fertilizer

Fertilizer

Fertilizer is any organic or inorganic material of natural or synthetic origin that is added to a soil to supply one or more plant nutrients essential to the growth of plants. A recent assessment found that about 40 to 60% of crop yields are attributable to commercial fertilizer use...

. Open cars are used for commodities such as coal

Coal

Coal is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure...

, which can get wet and dry out with less harmful effect. Hopper cars have been used by railways worldwide whenever automated cargo handling has been desired. "Ore jennies" is predominately a term for shorter open hopper cars hauling taconite

Taconite

Taconite is a variety of iron formation, an iron-bearing sedimentary rock, in which the iron minerals are interlayered with quartz, chert, or carbonate...

 by the Duluth, Missabe and Iron Range Railway

Duluth, Missabe and Iron Range Railway

The Duluth, Missabe and Iron Range Railway is a railroad operating in northern Minnesota and Wisconsin that hauls iron ore and later taconite to the Great Lakes ports of Duluth and Two Harbors, Minnesota...

 on Minnesota

Minnesota

Minnesota is a U.S. state located in the Midwestern United States. The twelfth largest state of the U.S., it is the twenty-first most populous, with 5.3 million residents. Minnesota was carved out of the eastern half of the Minnesota Territory and admitted to the Union as the thirty-second state...

's Iron Range

Iron Range

The Iron Range is a region that makes up the northeastern section of Minnesota in the United States. "The Range", as it is known by locals, is a region with multiple distinct bands of iron ore...

.

Recently in North America

North America

North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...

 the open hopper car has been in a terminal decline due to the advent of the rotary car dumper

Rotary car dumper

A rotary car dumper or wagon tippler is a mechanism used for unloading certain railroad cars such as hopper cars, gondolas or lorries . It holds the rail car to a section of track and rotates the track and car together to dump out the contents. Used with gondola cars, it is making open hopper cars...

 (which simply inverts the car to unload it, and has become the preferred unloading technology). A rotary dumper permits the use of simpler and more compact (because sloping ends are not required) gondola cars instead of hoppers. Covered hoppers, though, are still in widespread use. For loads that are less dense (such as grains) or susceptible to damage in the weather (such as unmixed cement

Cement

In the most general sense of the word, a cement is a binder, a substance that sets and hardens independently, and can bind other materials together. The word "cement" traces to the Romans, who used the term opus caementicium to describe masonry resembling modern concrete that was made from crushed...

), covered hopper

Covered hopper

A Covered Hopper is a railroad freight car. They are designed for carrying dry bulk loads, varying from grain to products such as sand and clay. The cover protects the loads from the weather - dried cement would be very hard to unload if mixed with water in transit, while grain would be liable to...

s are normally used.

Special hopper trains

The Coke Express

Coke Express

Coke Express trains are unit trains operated by CSX Transportation. They carry coke for steel making, power generation and other various uses. These cars consist of a mixture of standard and high-topped open-top hopper cars, most of which are owned by CSX...

, a unit train of hopper cars loaded with Coke (fuel)

Coke (fuel)

Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

, with the words "Coke Express" painted on the sides of the hoppers.

Typical American Freight Car Weights and Wheel Loads

Common Net Car Loads (Short tons/Long tons;tonnes)	Gross Car Weights (Pounds/kg)	Wheel Loads (Pounds/kg)
80 ST (71.4 LT; 72.6 t)	220000 (99,790.3 kg)	27500 (12,473.8 kg)
100 ST (89.3 LT; 90.7 t)	263000 (119,294.8 kg)	32875 (14,911.8 kg)
101 ST (90.2 LT; 91.6 t)	268000 (121,562.8 kg)	33500 (15,195.3 kg)
111 ST (99.1 LT; 100.7 t)	286000 (129,727.4 kg)	35750 (16,215.9 kg)
125 ST (111.6 LT; 113.4 t)	315000 (142,881.6 kg)	39375 (17,860.2 kg)

Increase in wheel loads has important implications for the rail infrastructure needed to accommodate future grain hopper car shipments. The weight of the car is transmitted to the rails and the underlying track structure through these wheel loads. As wheel loads increase, track maintenance expenses increase and the ability of a given rail weight, ballast depth, and tie configuration to handle prolonged rail traffic decreases. Moreover, the ability of a given bridge to handle prolonged rail traffic also decreases as wheel loads increase.

Etymology

The term "hopper car" comes from the coke

Coke (fuel)

Coke is the solid carbonaceous material derived from destructive distillation of low-ash, low-sulfur bituminous coal. Cokes from coal are grey, hard, and porous. While coke can be formed naturally, the commonly used form is man-made.- History :...

 manufacturing industry. Coke is used for the production of steel

Steel

Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...

. To make coke coal is packed into huge ovens which bake it to remove volatile oils. The goal is to turn the coal into carbon which is as pure as possible. In the historical process of coke manufacture after the coal was baked into coke it was pushed out onto a slanted metal roof called a "shed" or "wharf" where workers called "coke pullers" would wash down the hot coke with water hoses. Using a sort of a broom called a "beaver" they would then push the quenched coke into square holes in the shed which were called "hoppers" because the men would jump over the holes as they moved the coke around. The coke would fall down into a "hopper car" waiting below and would be shipped off by rail for further processing. In other words, the cars were named after the holes above them.

External links

• Union Pacific #7801 — photos and short history of an example of a typical self-clearing, open-top triple hopper.