On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle (wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing truck. On some large locomotives, a booster engine was mounted on the trailing truck to provide extra tractive effort when starting a heavy train and at low speeds on gradients.
The trailing wheels (boxed) on a 4-6-2 locomotive.
A cross-sectional view of a rigid trailing truck
Trailing wheels were used in some early locomotives but fell out of favor for a time during the latter 19th century. As demand for more powerful locomotives increased, trailing wheels began to be used to support the crew cab and rear firebox area.
Trailing wheels first appeared on American locomotives between 1890 and 1895, but their axle worked in rigid pedestals. It enabled boilers to be lowered, since the top of the main frames was dropped down behind the driving wheels and under the firebox. The firebox could also be longer and wider, increasing the heating surface area and steam generation capacity of the boiler, and therefore its power. The concept was soon improved to provide radial lateral movement by placing the pair of trailing wheels and their axle in a fabricated sub-frame or truck, usually with outside bearings as they gave the best lateral riding stability. One-piece cast-steel trailer trucks were developed about 1915, to provide the additional strength for a booster engine to be fitted to the trailing axle. Finally, about 1921 the Delta trailing truck was developed with an inverted-rocker centering device at the rear ends of the truck frame. Delta trucks were soon enlarged to carry four trailing wheels, and later six.[1]
In the Whyte notation, trailing wheels are designated by the last numbers in the series. For example, the 2-8-2 Mikado type locomotive had two leading wheels, eight driving wheels, and two trailing wheels. Some locomotives such as the 4-4-0 American type had no trailing wheels and were designated with a zero in the final place.
In the Whyte notation the number designates the number of wheels rather than the number of axles, thus the final 2 in the Mikado's 2-8-2 refers to two wheels (one axle) while the Northern type's 4-8-4 designation refers to four wheels (two axles).
^Alfred W Bruce.(1952) The Steam Locomotive in America - Its Development in the Twentieth Century New York, U.S.A. : Bonanza Books. p239-40, 256-57
^Huddlestone, Eugene L; George M Smerk. Uncle Sam's Locomotives: The USRA and the Nation's Railroads. Indiana University Press. p. 40. ISBN0-253-34086-1.
January 26, 2023
trailing, wheel, confused, with, tailwheel, steam, locomotive, trailing, wheel, trailing, axle, generally, unpowered, wheel, axle, wheelset, located, behind, driving, wheels, axle, trailing, wheels, usually, located, trailing, truck, some, large, locomotives, . Not to be confused with Tailwheel On a steam locomotive a trailing wheel or trailing axle is generally an unpowered wheel or axle wheelset located behind the driving wheels The axle of the trailing wheels is usually located in a trailing truck On some large locomotives a booster engine was mounted on the trailing truck to provide extra tractive effort when starting a heavy train and at low speeds on gradients The trailing wheels boxed on a 4 6 2 locomotive A cross sectional view of a rigid trailing truck Trailing wheels were used in some early locomotives but fell out of favor for a time during the latter 19th century As demand for more powerful locomotives increased trailing wheels began to be used to support the crew cab and rear firebox area Trailing wheels first appeared on American locomotives between 1890 and 1895 but their axle worked in rigid pedestals It enabled boilers to be lowered since the top of the main frames was dropped down behind the driving wheels and under the firebox The firebox could also be longer and wider increasing the heating surface area and steam generation capacity of the boiler and therefore its power The concept was soon improved to provide radial lateral movement by placing the pair of trailing wheels and their axle in a fabricated sub frame or truck usually with outside bearings as they gave the best lateral riding stability One piece cast steel trailer trucks were developed about 1915 to provide the additional strength for a booster engine to be fitted to the trailing axle Finally about 1921 the Delta trailing truck was developed with an inverted rocker centering device at the rear ends of the truck frame Delta trucks were soon enlarged to carry four trailing wheels and later six 1 A Delta type trailing truck fabricated using a one piece casting by Commonwealth Steel Company 2 In the Whyte notation trailing wheels are designated by the last numbers in the series For example the 2 8 2 Mikado type locomotive had two leading wheels eight driving wheels and two trailing wheels Some locomotives such as the 4 4 0 American type had no trailing wheels and were designated with a zero in the final place In the Whyte notation the number designates the number of wheels rather than the number of axles thus the final 2 in the Mikado s 2 8 2 refers to two wheels one axle while the Northern type s 4 8 4 designation refers to four wheels two axles The highest number of trailing wheels on a single locomotive is six as seen on 2 6 6 6 Allegheny type and the Pennsylvania Railroad s 6 8 6 steam turbine and 6 4 4 6 duplex locomotives as well as numerous Mason Bogie locomotives In the UIC classification system the number of axles rather than the number of wheels is counted See also EditAAR wheel arrangement Steam locomotive components UIC classification of locomotive axle arrangements Whyte notationReferences Edit Alfred W Bruce 1952 The Steam Locomotive in America Its Development in the Twentieth Century New York U S A Bonanza Books p239 40 256 57 Huddlestone Eugene L George M Smerk Uncle Sam s Locomotives The USRA and the Nation s Railroads Indiana University Press p 40 ISBN 0 253 34086 1 Retrieved from https en wikipedia org w index php title Trailing wheel amp oldid 1126095015, wikipedia, wiki, book, books, library,
