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A hopper car, sometimes historically referred to as a jimmie, is a style of car used when transporting freight by railroad. These cars are designed to carry bulk commodities left in a loose state, such as grain, coal, and sugar, among many other things. Several firms manufacture hopper cars and handle repairs and refurbishments on older cars, and numerous freight railroads continue to use them for transport.
The design of a hopper car permits the use of gravity for unloading. The car has a sloping floor and hinged openings near the bottom or on the underside. When the unloading doors are swung open, the contents of the hopper car flow out. Tools known as vibrators can be used to shake the hopper car to encourage the contents to empty out completely, without leaving behind any pockets or deposits. Many hopper cars have up to four separate bays for cargo, each with their own unloading doors, which allows for very rapid unloading since all four doors can be opened at once.
The design is similar to that of the gondola, another type of railroad car designed for loose freight. Gondolas do not necessarily have sloping floors, however, and they cannot be unloaded via hopper doors; instead, the car must be tipped to deliver the load, or it must be manually unloaded. The key distinction between the hopper railcar and the gondola railcar is that hopper cars are unloaded with the help of gravity.
It is possible to find covered and uncovered cars. Some loads don't require very much protection, in which case they are loaded in an uncovered or open hopper car. Other loads, like sugar, need to be protected from the elements so that the load is not compromised, in which case a covered hopper car will be used to seal the load inside so that it cannot get wet.
Personnel in freight yards are generally familiar with the operation of hopper cars and can safely load and unload them. If there are special precautions with a specific load, they may be noted on the packing manifest or on the car itself so that people are familiar with any issues which need to be addressed when handling the load. People who are not experienced with hopper cars should make sure to stand clear during loading and unloading operations to reduce the risk of injury.