Under the
Whyte notation
The Whyte notation is a classification method for steam locomotives, and some internal combustion locomotives and electric locomotives, by wheel arrangement. It was devised by Frederick Methvan Whyte, and came into use in the early twenti ...
for the classification of
steam locomotive
A steam locomotive is a locomotive that provides the force to move itself and other vehicles by means of the expansion of steam. It is fuelled by burning combustible material (usually coal, Fuel oil, oil or, rarely, Wood fuel, wood) to heat ...
s by
wheel arrangement
In rail transport, a wheel arrangement or wheel configuration is a system of classifying the way in which wheels are distributed under a locomotive. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and c ...
, represents the arrangement of four
leading wheel
The leading wheel or leading axle or pilot wheel of a steam locomotive is an unpowered wheel or axle located in front of the driving wheels. The axle or axles of the leading wheels are normally located on a leading truck. Leading wheels are used ...
s, ten powered and coupled
driving wheel
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons (or turbine, in the case of a steam turbine locomotive). On a conventional, non-articulated locomotive, the driving wheels are all coupled t ...
s and two
trailing wheel
On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle (Wheelset (rail transport), wheelset) located behind the driving wheels. The axle of the trailing wheels is usually located in a trailing Bogie, t ...
s. In South Africa, where the wheel arrangement was first used, the type was known as a Reid Tenwheeler. In the United States of America it was known as a Southern Pacific on the
Southern Pacific Railroad
The Southern Pacific (or Espee from the railroad initials) was an American Railroad classes#Class I, Class I Rail transport, railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was oper ...
and as an Overland on the
Union Pacific Railroad
The Union Pacific Railroad is a Railroad classes, Class I freight-hauling railroad that operates 8,300 locomotives over routes in 23 U.S. states west of Chicago and New Orleans. Union Pacific is the second largest railroad in the United Stat ...
.
Overview
This wheel arrangement was first used on the
Natal Government Railways
The Natal Government Railways (NGR) was formed in January 1877 in the Colony of Natal.
In 1877, the Natal Government Railways acquired the Natal Railway Company for the sum of £40,000, gaining the line from the Point to Durban and from Durban ...
(NGR) in the
Colony of Natal
The Colony of Natal was a British colony in south-eastern Africa. It was proclaimed a British colony on 4 May 1843 after the British government had annexed the Boer Republic of Natalia, and on 31 May 1910 combined with three other colonies t ...
in 1899, on a tank locomotive that was designed to meet the requirement for a locomotive that could haul at least one and a half times as much as an NGR
Dübs A 4-8-2T locomotive.
In the United States, a simple expansion (simplex) version of the type was used only on the Southern Pacific and Union Pacific Railroads.
Baldwin Locomotive Works
The Baldwin Locomotive Works (BLW) was an American manufacturer of railway locomotives from 1825 to 1951. Originally located in Philadelphia, Pennsylvania, it moved to nearby Eddystone, Pennsylvania, Eddystone in the early 20th century. The com ...
built an experimental compound expansion in 1926, but since the weight and length of this engine was too much for all but the heaviest and straightest track and compound steam locomotives had already lost favor on United States railroads, its demonstration runs failed to generate interest and no more were produced.
[Swengel, F.M. (1967). ''The American Steam Locomotive: Vol. 1, The Evolution of the Steam Locomotive''. Davenport: Midwest Rail Publications. pp. 222–223.]
Usage
Brazil
Brazil had 5 1600mm gauge 4-10-2 tender locomotives, built by Henschel in 1938.
South Africa
Between 1899 and 1903, the
Natal Government Railways
The Natal Government Railways (NGR) was formed in January 1877 in the Colony of Natal.
In 1877, the Natal Government Railways acquired the Natal Railway Company for the sum of £40,000, gaining the line from the Point to Durban and from Durban ...
(NGR) placed 101 tank locomotives in service. The locomotive was designed by G.W. Reid, the Locomotive Superintendent of the NGR at the end of the nineteenth century, and built in Scotland by
Dübs and Company
Dübs & Co. was a locomotive manufacturer in Glasgow, Scotland, founded by Henry Dübs in 1863 and based at the Queens Park Works in Polmadie. In 1903 it amalgamated with two other Glasgow locomotive manufacturers to create the North British Loc ...
and the newly established
North British Locomotive Company
The North British Locomotive Company (NBL, NB Loco or North British) was created in 1903 through the merger of three Glasgow locomotive manufacturing companies; Sharp, Stewart and Company (Atlas Works), Neilson, Reid and Company (Hyde Park W ...
. On the NGR, the locomotive type became known as the Reid Tenwheeler and was officially designated Class C.
[''The Railway Report for year ending 31 Dec. 1908'', Natal Government Railways, p. 39, par 14.]
The locomotive used saturated steam and was equipped with
Allan straight link valve gear. The trailing wheels were of the
Cartazzi type that allowed the axle some lateral movement. In order to negotiate sharp curves, both the first and fifth sets of coupled wheels were
flangeless, but since the blind trailing coupled wheels had a tendency to derail while reversing, particularly over points, their tyre width was later increased from to . In 1912, after the establishment of the South African Railways, the surviving unmodified NGR locomotives were designated
Class H.
[Classification of S.A.R. Engines with Renumbering Lists, issued by the Chief Mechanical Engineer's Office, Pretoria, January 1912, pp. 7, 11, 13, 22–25 (Reprinted in April 1987 by SATS Museum, R.3125-6/9/11-1000)]

In 1901 and 1902, towards the end of the
Second Boer War
The Second Boer War (, , 11 October 189931 May 1902), also known as the Boer War, Transvaal War, Anglo–Boer War, or South African War, was a conflict fought between the British Empire and the two Boer republics (the South African Republic and ...
, the Imperial Military Railways also acquired 35 Reid Tenwheeler locomotives from Dübs and Company and
Neilson, Reid and Company. After the war, they came onto the roster of the Central South African Railways (CSAR), who designated them
Class E. In 1903, the CSAR modified six of them to
locomotives and, beginning in 1905, the remainder to
tank-and-tender locomotives.
A final order for one new Reid Tenwheeler was placed by
Witbank
Witbank (), officially eMalahleni, is a city situated on the Highveld of Mpumalanga, South Africa, within the Emalahleni Local Municipality, Mpumalanga, Emalahleni Local Municipality. The name Witbank is Afrikaans for "white ridge", and is named ...
Collieries as late as 1927. The total of 137 locomotives built to this design was about double the number of all other locomotives in use elsewhere in the world, all of which were tender locomotives that served in the United States and Brazil.
United States
In the United States, the type was used only on the
Southern Pacific Railroad
The Southern Pacific (or Espee from the railroad initials) was an American Railroad classes#Class I, Class I Rail transport, railroad network that existed from 1865 to 1996 and operated largely in the Western United States. The system was oper ...
(SP), which called it the Southern Pacific, and the
Union Pacific Railroad
The Union Pacific Railroad is a Railroad classes, Class I freight-hauling railroad that operates 8,300 locomotives over routes in 23 U.S. states west of Chicago and New Orleans. Union Pacific is the second largest railroad in the United Stat ...
(UP), which called it the Overland after their corporate sobriquet, ''The Overland Route''. Only sixty locomotives of this wheel arrangement were built for domestic service and all but one were constructed as simplex
three-cylinder engines.
[Boynton, James E. (1973). ''4-10-2: Three Barrels of Steam''. Glenwood: Felton. pp. 2, 5–6, 84–98, 144–149. ]
In 1925, the SP placed an order for sixteen locomotives with the
American Locomotive Company
The American Locomotive Company (often shortened to ALCO, ALCo or Alco) was an American manufacturer that operated from 1901 to 1969, initially specializing in the production of locomotives but later diversifying and fabricating at various time ...
(ALCO) and, later in the same year, the UP ordered one. The first SP locomotive,
no. 5000, was completed in April 1925, while the UP locomotive, no. 8000, was completed the following month. Within a few months, the SP ordered more of these engines and built up a fleet of 49. The UP, on the other hand, waited thirteen months before repeating orders and establishing a fleet of ten locomotives. All 59 were simplex locomotives and were built by ALCO.

In 1926,
Baldwin Locomotive Works
The Baldwin Locomotive Works (BLW) was an American manufacturer of railway locomotives from 1825 to 1951. Originally located in Philadelphia, Pennsylvania, it moved to nearby Eddystone, Pennsylvania, Eddystone in the early 20th century. The com ...
constructed an experimental demonstrator, the
Baldwin 60000, which was a three-cylinder
compound locomotive
A compound locomotive is a steam locomotive which is powered by a compound steam engine, compound engine, a type of steam engine where steam is expanded in two or more stages. The locomotive was only one application of compounding. Two and three ...
, the only so constructed. This engine used high-pressure steam in the inside cylinder and then exhausted that steam into the two low-pressure outside cylinders. It also had a
water tube boiler
A high pressure watertube boiler (also spelled water-tube and water tube) is a type of boiler in which water circulates in tubes heated externally by fire. Fuel is burned inside the furnace, creating hot gas which boils water in the steam-generat ...
, one of a very few locomotives so equipped in the United States. As technologically innovative as Baldwin's was, however, it was outmoded when built since compound steam locomotives had already lost favor in United States railroading.
It was found that the type ran better and rode smoother than the type from which it had evolved.
The third cylinder in the center of the cylinder saddle sloped down at a 9½ degree angle to a crank on the second drivers' axle, while the two outside rods connected to the third drivers. The three-cylinder feature on these locomotives gave them a distinctive sound at work, described as a "hop, skip and jump rhythm".
While the SP engines could operate only on relatively straight and heavily built
mainlines, their long service lives of between 28 and 30 years proved that they were good locomotives. The most serious mishap was when, in November 1946, one of the SP locomotives suffered a boiler explosion which killed four train crew. In addition, the inside cylinder's rod created serious maintenance problems because the floating bushings could fail, which lengthen maintenance down-time since such failures required major valve re-settings that caused delays. It was reported that such failures created such great pounding on the rails that railroad housewives along the line "complained of crockery cracking when a defective rumbled past their homes".
When the UP became tired of the major mechanical problems associated with three cylinders, it converted its locomotives to two-cylinder locomotives in 1942 and renumbered them 5090 to 5099.
Two locomotives of this type have been preserved:
*
Southern Pacific 5021, on static display at the
Los Angeles County Fairgrounds in
Pomona, California
Pomona ( ) is a city in eastern Los Angeles County, California, United States. Pomona is located in the Pomona Valley, between the Inland Empire and the San Gabriel Valley. At the 2020 United States census, 2020 census, the city's population was ...
.
* The
Baldwin 60000 demonstrator, on display at the
Franklin Institute Science Museum
The Franklin Institute is a science museum and a center of science education and research in Philadelphia, Pennsylvania. It is named after the American scientist and statesman Benjamin Franklin. It houses the Benjamin Franklin National Memoria ...
in
Philadelphia, Pennsylvania
Philadelphia ( ), colloquially referred to as Philly, is the List of municipalities in Pennsylvania, most populous city in the U.S. state of Pennsylvania and the List of United States cities by population, sixth-most populous city in the Unit ...
.
References
{{Whyte types
10,4-10-2