Editing Hopper car

{{short description|Railroad freight car used for transporting loose bulk commodities}}
{{use dmy dates|date=October 2019}}
[[File:Covered hopper car.jpg|thumb|Covered hopper cars carrying [[Fracking proppants|frac sand]] on the [[BNSF Railway]] through [[La Crosse, Wisconsin]]]]
[[File:Squared tank car.jpg|thumb|Hopper cars may carry [[hazardous materials]], such as this one in the Midwestern United States.  Its payload of [[ammonium nitrate]] is indicated by the [[UN number]] on the diamond-shaped [[Placard#United States Department of Transportation|U.S. DOT placard]].<ref name=":0">{{Cite web |last=Beaucham |first=Catherine C. |date=August 2023 |title=Evaluation of Potential Exposures to Railway Hazardous Material Inspectors |url=https://www.cdc.gov/niosh/hhe/reports/pdfs/2022-0049-3387.pdf |access-date=2024-05-04 |website=U.S. National Institute for Occupational Safety and Health |type=[[Health Hazard Evaluation Program|Health Hazard Evaluation Report]]}}</ref>]]
A '''hopper car''' ({{abbr|NAm|North America}}) or '''[[Open wagon#Hopper wagons|hopper wagon]]''' ({{abbr|UIC|International Union of Railways}}) is a type of [[railroad]] [[Railroad car#Freight cars|freight car]] that has opening doors or gates on the underside or on the sides to discharge its cargo.  They are used to transport loose solid [[Bulk cargo|bulk commodities]] such as [[coal]], [[ore]], [[cereal|grain]], and [[track ballast]].<ref>{{cite web|url=http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Covered+Hopper/ |archive-url=https://web.archive.org/web/20100916213706/http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Covered+Hopper/ |url-status=dead |archive-date=16 September 2010 |title=Covered Hopper Railcars |publisher=GATX Corporation |access-date=11 September 2012 }}</ref><ref>{{cite web|url=http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Small+Cube+Open-Top+Hoppers/ |archive-url=https://web.archive.org/web/20100916213808/http://www.gatx.com/wps/wcm/connect/GATX/GATX_SITE/Home/Rail/Rail+North+America/Products/Equipment+Types/Freight/Small+Cube+Open-Top+Hoppers/ |url-status=dead |archive-date=16 September 2010 |title=Small Cube Open-Top Hoppers and Gondolas |publisher=GATX Corporation |access-date=11 September 2012 }}</ref><ref>{{cite web|url=http://www.crdx.com/coveredHop.html |title=Covered Hopper Cars |publisher=Chicago Freight Car Leasing Company |access-date=11 September 2012 |url-status=dead |archive-url=https://web.archive.org/web/20120416165540/http://www.crdx.com/coveredHop.html |archive-date=16 April 2012 }}</ref>  Plastic pellets and some finely ground material, similar to flour, are transported in hopper cars that have pneumatic unloading. The bottom gates on the pneumatic hoppers connect to a hose attached to industrial facilities' storage tanks. Air is injected to fluidize the railcar contents for unloading.<ref>{{Cite web |title=5660 Pressureaide® Covered Hopper |url=https://www.gbrx.com/railcars/5660-pressureaide-covered-hopper/ |access-date=2025-01-12 |website=The Greenbrier Companies |language=en-US}}</ref> The hopper car was developed in parallel with the development of automated handling of such commodities, including automated loading and unloading facilities.

Hopper cars are distinguished from [[gondola (rail)|gondola cars]], which do not have opening doors on their underside or sides.  Gondola cars are simpler and more compact because sloping ends are not required, but a [[rotary car dumper]] is required to unload them.  Some "dual-purpose" hoppers have a rotary coupler on one or both ends, so they can be used in both rotary and bottom-dump operations.

== Types ==
Two main types of hopper car exist.  Covered hopper cars, which are equipped with a fixed roof, are used for cargo like [[cereal|grain]], [[sugar]], and [[fertilizer]], and [[Portland cement]]<ref>{{cite book |last=Walthers |first=W. K. |author-link=Wm. K. Walthers |title=Handbook for Model Railroaders |date=1937 |publisher=The Modelmaker Corporation |location=Wauwatosa, Wisconsin |page=114}}</ref> that must be protected from exposure to the weather.  [[Open wagon#Hopper wagons|Open hopper]] cars, which do not have a roof, are used for commodities such as [[coal]], which can suffer exposure with less detrimental effect.

Removable [[canvas]] covers are sometimes used to protect moisture sensitive commodities in open hopper cars.  Closed hopper cars have a metal top with waterproof loading hatches, which provides superior protection.<ref>{{cite book |last=Henry |first=Robert Self |title=This Fascinating Railroad Business |date=1942 |publisher=The Bobbs-Merrill Company |edition=First |location=New York |pages=248 & 249}}</ref> These loading hatches along the top of the covered hopper may be a single long opening along the centerline or a pattern of multiple round or square openings positioned to allow uniform weight distribution when loading the car.

Some covered hoppers have two to four separate bays, with chutes at the bottom to direct unloading contents. 

== Use ==
Hopper cars have been used by railways worldwide whenever automated cargo handling has been desired. "Ore jennies" is predominantly a term for shorter open hopper cars hauling [[taconite]] by the [[Duluth, Missabe and Iron Range Railway]] on [[Minnesota]]'s [[Iron Range]].  The [[Coke Express]], a  [[CSX Transportation|CSX]] [[unit train]] of hopper cars loaded with [[Coke (fuel)|coke]], with the words "Coke Express" painted on the sides of the hoppers.
[[File:Covered_hopper_grain_car.webp|left|thumb|Covered hopper grain car]]
Large [[Unit train|unit trains]] of various grain crops are a common sight in [[North America]], reaching up to 125 cars long. These predominantly haul grain from the large farming areas of the [[Great Plains]] to various markets, but a number of unit trains originate from other major farming areas, such as [[Illinois]] and [[Indiana]] as well as the Canadian provinces of [[Alberta]], [[Saskatchewan]] and [[Manitoba]]. These trains may originate from a single [[grain elevator]], or may be marshaled in a [[Classification yard|yard]] from various locals (short trains which serve nearby industries). The destinations tend to be large [[Flour mill|flour mills]] or [[Port|ports]] (for export), or they may be split up and delivered to multiple locations. The empty cars may return as a whole train, or may be sent back in smaller quantities on manifest trains (trains which carry just about any type of freight). These trains are used primarily for hauling products such as [[Maize|corn]], [[wheat]] and [[barley]].

== History ==
[[File:6619.JPG|left|thumb|This covered hopper car originally was built in the 1950s for the [[Atlantic Coast Line Railroad]]. After the 1967 SCL merger, these cars were fitted with [[Rotary car dumper|rotary couplers]] and used in [[Bone Valley]] phosphate service.]]
The word "hopper", meaning a "container with a narrow opening at bottom", goes back to the thirteenth century,<ref>{{cite web |title=Hopper |url=http://www.etymonline.com/index.php?search=hopper |website=Online Etymology dictionary}}</ref> and is found in [[Chaucer]]'s story "[[The Reeve's Tale]]" (written late fourteenth century) in reference to a machine for grinding grain into [[flour]].

Historically, open hopper cars were used to carry coarse mined products like [[coal]], [[ore]], and [[gravel]], while [[Boxcar|boxcars]] were used for granular materials requiring protection from the elements.

Weatherproof covers were added to hopper cars, creating the covered hopper.  Early production emphasized two-bay cars very similar to open coal hoppers and suitable for materials of similar density, like [[Portland cement]] or [[rock-salt]]. Some cars were available in the 1910s, and became more common by the 1940s. These early cars were volume-limited for less dense commodities like grain or [[sugar]], so later designs include longer covered hopper cars with higher sides and three or more bottom bays.<ref name="abc">{{cite book |last1=Sweetland |first1=David R. |title=Northern New England Color Guide to Freight and Passenger Equipment |last2=Horsley |first2=Stephen |date=1994 |publisher=Morning Sun Books |location=Edison, New Jersey |pages=35, 36 & 51 |lccn=94075695 |oclc=32243319}}</ref> Increasing [[axle load]] limits have allowed some of the heavier loads formerly assigned to two-bay hoppers to be assigned to larger, more efficient three-bay hoppers.

Some covered hopper cars retain the conventional centersill as a strength member transmitting [[Compression (physics)|compression]] and [[Tension (physics)|tension]] [[Force|forces]] from one car to the next. Beginning in the 1960s, designs distributing these forces along the sides of the car eliminated the centersill beam to simplify [[bulk material handling]] with wider hopper openings reducing the tendency for bridging to restrict gravity flow when unloading the car.<ref>{{cite web |title=Centerflow Cars |url=http://www.americanrailcar.com/Manufacturing/CenterflowCars |access-date=24 June 2020 |publisher=American Railcar Industries, Inc.}}</ref>

== Typical North American freight car weights and wheel loads ==
{| class="wikitable"
|-
! colspan="3" | Common net car loads
! colspan="2" | Gross car weights
! colspan="2" | Wheel loads
|-
! Short tons !! Long tons !! Tonnes
! Pounds !! Kilograms
! Pounds !! Kilograms
|-
| {{convert|80|ST|LT t|1|disp=table}}  || {{convert|220000|lb|kg|disp=table}} || {{convert|27500|lb|kg|disp=table}}
|-
| {{convert|100|ST|LT t|1|disp=table}} || {{convert|263000|lb|kg|disp=table}} || {{convert|32875|lb|kg|disp=table}}
|-
| {{convert|101|ST|LT t|1|disp=table}} || {{convert|268000|lb|kg|disp=table}} || {{convert|33500|lb|kg|disp=table}}
|-
| {{convert|111|ST|LT t|1|disp=table}} || {{convert|286000|lb|kg|disp=table}} || {{convert|35750|lb|kg|disp=table}}
|-
| {{convert|125|ST|LT t|1|disp=table}} || {{convert|315000|lb|kg|disp=table}} || {{convert|39375|lb|kg|disp=table}}
|}

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.<ref name="carweights">{{cite web |last1=Bitzan |first1=John D. |last2=Tolliver |first2=Denver D. |date=October 2001 |title=The Economics of Heavy Hopper Cars |url=http://www.mountain-plains.org/pubs/html/mpc-01-127-4/pg2.php |archive-url=https://web.archive.org/web/20110723174647/http://www.mountain-plains.org/pubs/html/mpc-01-127-4/pg2.php |archive-date=23 July 2011 |access-date=2010-08-07 |website=Mountain-Plains.org |publisher=Mountain Plains}}</ref> The [[axle load]] is twice the wheel load.

== Gallery ==
<gallery class=center caption="[[Open wagon#Hopper wagons|Non North American hopper cars]]" heights="150px" widths="200px">
File:Iron ore hopper (SJ, 1900).JPG|Swedish [[iron ore]] hopper ([[mineral wagon]]), built in 1900
File:Вагон.jpg|[[Kambarka Engineering Works]] hopper car to transport [[track ballast]], {{RailGauge|750mm|lk=on}} gauge
File:BOBRN class Hopper cars Freight rakes at Samalkot Junction 01.jpg|BOBRN class hopper cars freight [[Rake (train)|rakes]] used by [[Indian Railways]] 
File:Selbstentladewagen-Fccs6450-Mechanik.jpg|Unloading mechanism of a German hopper car
</gallery><gallery class="center" heights="150" widths="200" caption="North American hopper cars">
File:Coke Express.jpg|The Coke Express rolls through a [[level crossing]]. Cars display both the [[CSX Transportation|CSX]] logo and the words '''''COKE EXPRESS'''''
File:Hopper cars.jpg|Two-bay hopper cars of the [[Reading Railroad]]
File:Pittsburg August 2015 17 (hopper car).jpg|[[Northwestern Oklahoma Railroad|NOKL]] hopper car at [[Pittsburg, Texas]], in 2015
File:2009-07-05 Hopper car at N&W Durham Yard.jpg|[[Norfolk and Western Railway|N&W]] ballast hopper car.
File:CSXhopper7182012.jpg|a two-bay through-sill [[CSX]] covered hopper
File:LO DME 49328.jpg|Covered hopper of the [[Dakota, Minnesota and Eastern Railroad]]
</gallery>

== See also ==
* [[CDA wagon]]
* [[Gravity wagon]], also called a slant wagon
* [[Hopper barge]]
* [[Victorian Railways hopper wagons]]

== References ==
{{Reflist}}

== Further reading ==
* Bernard Ciry, "Les wagons-trémies à céréales et à bogies", ''Rail Miniature Flash'', No.&nbsp;632, Paris, Rigel Editions, June 2018, pages 28–41.

== External links ==
{{Commons category|Hopper railway wagons}}
* [https://web.archive.org/web/20060509071410/http://sdrm.org/roster/freight/hopp7801/index.html Union Pacific #7801] – Photos and short history of an example of a typical self-clearing, open-top triple hopper
* [https://web.archive.org/web/20140327040407/http://www.americanrailcar.com/RailcarManufacturing.aspx Rail car manufacturing]
* [https://web.archive.org/web/20111007195551/http://worldtraderef.com/WTR_site/Rail_Cars/Guide_to_Rail_Cars.asp Guide to Rail Cars] 

{{Freight cars}}
{{Mining equipment}}

[[Category:Freight rolling stock]]