0-8-4
Encyclopedia
Under the Whyte notation
for the classification of steam locomotive
s, 0-8-4 represents the wheel arrangement
of no leading wheel
s, eight powered and coupled driving wheel
s on four axles, and four trailing wheel
s on two axles (usually in a trailing bogie).
s; there are no 0-8-4
tender locomotives recorded.
The first example was the Great Central Railway
Class 8H of 1907. These were designed for hump shunting and so required high tractive effort
, good adhesion and traction for starting from rest. Although developed from the 8A tender class, and having some interchangeable parts in their running gear, they also had three cylinders rather than two. The three cylinder tank locomotive was in fashion at this time, as a means of achieving good acceleration from rest, owing to their more even power delivery and the reduced risk of wheelslip
. This three-cylindered pattern had begun with Holden
's Decapod
of 1902 and carried through into Worsdell
and Raven
's fast passenger tank locomotives of 4-6-2T
and 4-4-4T layout for the North Eastern Railway
in 1910 and 1913. Worsdell also designed a comparable heavy shunter of his own, the Class X
, although this used the 4-8-0T layout with a leading bogie, rather than trailing.
The class was considered a success, although highly specialised, and developments were rebuilt and built new by the LNER. The rebuilt locomotive trialled a new outside-framed bogie, fitted with a booster engine
, the LNER being one of the few UK railways to favour these. Two further locomotives were also built by the LNER. Six were built in total.
The second example was LNWR 380 Class
. These were a simple stretched version of the inside-cylindered 0-8-2T 1185 Class
, which had been derived from the LNWR's numerous 0-8-0 freight locomotives, with a larger coal bunker. The class was intended for both shunting, banking and as mineral engines for the heavy coal or iron train use in the South Wales coalfield. The enlarged bunker made them more suitable for these longer workings. Thirty were built.
Whyte notation
The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte and came into use in the early twentieth century encouraged by an editorial in American Engineer and Railroad Journal...
for the classification of steam locomotive
Steam locomotive
A steam locomotive is a railway locomotive that produces its power through a steam engine. These locomotives are fueled by burning some combustible material, usually coal, wood or oil, to produce steam in a boiler, which drives the steam engine...
s, 0-8-4 represents the wheel arrangement
Wheel arrangement
In rail transport, a wheel arrangement is a system of classifying the way in which wheels are distributed beneath a locomotive.. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country...
of no leading wheel
Leading wheel
The leading wheel or leading axle 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 in a truck...
s, eight powered and coupled driving wheel
Driving wheel
On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons...
s on four axles, and four trailing wheel
Trailing wheel
On a steam locomotive, a trailing wheel or trailing axle is generally an unpowered wheel or axle located behind the driving wheels. The axle of the trailing wheels was usually located on a trailing truck...
s on two axles (usually in a trailing bogie).
Equivalent classifications
Other equivalent classifications are:- UIC classificationUIC classificationThe UIC classification of locomotive axle arrangements describes the wheel arrangement of locomotives, multiple units and trams. It is set out in the International Union of Railways "Leaflet 650 - Standard designation of axle arrangement on locomotives and multiple-unit sets". It is used in much...
: D2 (also known as German classification and Italian classification) - French classification: 042
- Turkish classificationTurkish classificationIn the Turkish classification system for railway locomotives, the number of powered axles are followed by the total number of axles. It is identical to the Swiss system except that the latter places a slash between the two numbers.Thus0-6-0 becomes 33...
: 46 - Swiss classification: 4/6
Examples
All examples of this wheel arrangement were tank locomotiveTank locomotive
A tank locomotive or tank engine is a steam locomotive that carries its water in one or more on-board water tanks, instead of pulling it behind it in a tender. It will most likely also have some kind of bunker to hold the fuel. There are several different types of tank locomotive dependent upon...
s; there are no 0-8-4
0-8-4
Under the Whyte notation for the classification of steam locomotives, 0-8-4 represents the wheel arrangement of no leading wheels, eight powered and coupled driving wheels on four axles, and four trailing wheels on two axles ....
tender locomotives recorded.
United Kingdom
The tank locomotives were themselves rare. Two separate classes were built in the UK, by two different railway companies. Both of these had their origins with an 0-8-0 tender design. Both classes were designed as powerful, but slow-speed, locomotives for heavy shunting. They did not require high speed or long range, so had no need for a leading truck or the greater coal capacity of a tender. Other than this though, they were quite distinct.The first example was the Great Central Railway
Great Central Railway
The Great Central Railway was a railway company in England which came into being when the Manchester, Sheffield and Lincolnshire Railway changed its name in 1897 in anticipation of the opening in 1899 of its London Extension . On 1 January 1923, it was grouped into the London and North Eastern...
Class 8H of 1907. These were designed for hump shunting and so required high tractive effort
Tractive effort
As used in mechanical engineering, the term tractive force is the pulling or pushing force exerted by a vehicle on another vehicle or object. The term tractive effort is synonymous with tractive force, and is often used in railway engineering to describe the pulling or pushing capability of a...
, good adhesion and traction for starting from rest. Although developed from the 8A tender class, and having some interchangeable parts in their running gear, they also had three cylinders rather than two. The three cylinder tank locomotive was in fashion at this time, as a means of achieving good acceleration from rest, owing to their more even power delivery and the reduced risk of wheelslip
Wheelslip
Articles on Wheelslip include:* Locomotive wheelslip, railways* Wheelspin, road vehicles* Wheelspin...
. This three-cylindered pattern had begun with Holden
James Holden (engineer)
James Holden was an English locomotive engineer.He is remembered mainly for the "Claud Hamilton" 4-4-0, his pioneering work with oil fuel, and his unique "Decapod".- Biography :...
's Decapod
GER Decapod
The GER Class A55 or Decapod was an experimental steam locomotive with an 0-10-0T wheel arrangement designed by James Holden for the Great Eastern Railway...
of 1902 and carried through into Worsdell
Wilson Worsdell
Wilson Worsdell was a British locomotive engineer who was locomotive superintendent of the North Eastern Railway from 1890 to 1910. He was the younger brother of T.W. Worsdell.-Family:...
and Raven
Vincent Raven
Sir Vincent Litchfield Raven KBE was chief mechanical engineer of the North Eastern Railway from 1910 to 1922.- Biography :...
's fast passenger tank locomotives of 4-6-2T
NER Class Y
The North Eastern Railway Class Y 4-6-2T tank locomotives were designed whilst Wilson Worsdell was Chief Mechanical Engineer, but none were built until 1910 by which time Vincent Raven had taken over.-Overview:...
and 4-4-4T layout for the North Eastern Railway
North Eastern Railway
North Eastern Railway could refer to:*North Eastern Railway *North Eastern Railway *North Eastern Railway *North Eastern Railway...
in 1910 and 1913. Worsdell also designed a comparable heavy shunter of his own, the Class X
NER Class X
The NER Class X was a class of 4-8-0T tank locomotive designed by Wilson Worsdell for the North Eastern Railway. They were intended for use as powerful shunting engines to arrange and move coal wagons for loading into ships. In total 15 were built, 10 by the NER between 1909 and 1910, and a...
, although this used the 4-8-0T layout with a leading bogie, rather than trailing.
The class was considered a success, although highly specialised, and developments were rebuilt and built new by the LNER. The rebuilt locomotive trialled a new outside-framed bogie, fitted with a booster engine
Booster engine
A booster engine for steam locomotives is a small two-cylinder steam engine back-gear-connected to the trailing truck axle on the locomotive or, if none, the lead truck on the tender. A rocking idler gear permits it to be put into operation by the engineer...
, the LNER being one of the few UK railways to favour these. Two further locomotives were also built by the LNER. Six were built in total.
The second example was LNWR 380 Class
LNWR 380 Class
The LNWR 380 Class was a class of 0-8-4T steam tank locomotives designed by H. P. M. Beames. Although designed under the LNWR regime they appeared as LMS locomotives after the 1923 grouping. They were essentially an extended version of the 1185 Class 0-8-2T with a longer bunker, and were also...
. These were a simple stretched version of the inside-cylindered 0-8-2T 1185 Class
LNWR 1185 Class
- External links :* *...
, which had been derived from the LNWR's numerous 0-8-0 freight locomotives, with a larger coal bunker. The class was intended for both shunting, banking and as mineral engines for the heavy coal or iron train use in the South Wales coalfield. The enlarged bunker made them more suitable for these longer workings. Thirty were built.