Leading wheel

Leading Wheel

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Leading wheel

The leading wheel or leading axle of a steam locomotive

Steam locomotive

A steam locomotive is a locomotive powered by steam. The term usually refers to its use on railways, but can also refer to a "road locomotive" such as a traction engine or steamroller....
is an unpowered wheel

Wheel

A wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation whilst supporting a load , or performing labour in machines....
or axle

Axle

An axle is a central shaft for a rotation wheel or gear. In some cases the axle may be fixed in position with a bearing or bushing sitting inside the hole in the wheel or gear to allow the wheel or gear to rotate around the axle....
located in front of the driving wheels. The axle or axles of the leading wheels are normally located in a truck (or "bogie

Bogie

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What is trailing and leading portion of wheel? pls tell me. Though it is a simple quiostion!

Encyclopedia

The leading wheel or leading axle of a steam locomotive

Steam locomotive

Wheel

A wheel is a circular device that is capable of rotating on its axis, facilitating movement or transportation whilst supporting a load , or performing labour in machines....
or axle

Axle

Bogie

A bogie is a wheeled wagon or trolley. In Machine terms, a bogie is a chassis or framework carrying wheels, attached to a vehicle. It can be fixed in place, as on a cargo truck, mounted on a swivel, as on a railway carriage or locomotive, or sprung as in the suspension of a caterpillar tracked vehicle....
"). Leading wheels are used to help the locomotive negotiate curves and to support the front portion of the boiler.

Importantly, the leading bogie does not have simple rotational motion about a vertical pivot, as might first be thought. It must also be free to slip sideways to a small extent (otherwise the locomotive is unable to follow curves accurately - a point lost on the 19th century railway pioneers), and some kind of springing mechanism is normally included to control this movement and give a tendency to return to centre. The sliding bogie of this type was patented by William Adams

William Adams (locomotive engineer)

William Adams was the Locomotive Superintendent of the North London Railway from 1858 to 1873; the Great Eastern Railway from 1873 until 1878 and the London and South Western Railway from then until his retirement in 1895....
in 1865. The first use of leading wheels is commonly attributed to John B. Jervis

John B. Jervis

John Bloomfield Jervis was an United States civil engineer. Working as chief engineer for the Delaware and Hudson, he designed the Stourbridge Lion, as well as the first steam locomotives with a leading bogie that became the 4-2-0 locomotive type....
who employed them in his 1832 design for a locomotive with four leading wheels and two driving wheel

Driving wheel

On a steam locomotive, a driving wheel is a powered wheel which is driven by the locomotive's pistons . On a conventional, non-articulated locomotive, the driving wheels are all coupled together with side rods ; normally one pair is directly driven by the main rod which is connected to the end of the piston rod; power is transmitted to th...
s (a type that became known as the Jervis). In the Whyte

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 ....
system of describing locomotive wheel arrangements

Wheel arrangement

In rail transport a wheel arrangement is a system of classifying the arrangement of the bogie of a locomotive by type, position, and connections....
, his locomotive would be classified as a 4-2-0

4-2-0

In the Whyte notation, a 4-2-0 is a railroad steam locomotive that consists of a 4-wheel leading truck followed by a single driving axle. This type of locomotive, often called a Jervis type, was common on United States railroads from the 1830s through the 1850s....
: that is to say, it had four leading wheels, two driving wheel

Driving 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 were usually located on a trailing Bogie....
s. In the UIC classification

UIC classification

The International Union of Railways classification is a comprehensive system for describing the wheel arrangement of locomotives, multiple units and trams....
system, which counts axles rather than wheels and uses letters to denote powered axles, the Jervis would be classified 2-A.

Locomotives without leading trucks are generally regarded as unsuitable for high speed use. The British Railway Inspectorate condemned the practice in 1895, following an accident involving two 0-4-4

0-4-4

In Whyte notation, an 0-4-4 is a railroad steam locomotive that has four coupled driving wheels followed by four trailing wheels, with no leading wheels....
s at Doublebois, Cornwall, on the Great Western Railway

Great Western Railway

The Great Western Railway was a History of rail transport in Great Britain that linked London with the south west and west of England and most of Wales....
. Other designers, however, persisted with the practice and the famous 0-4-2

0-4-2

In Whyte notation, a 0-4-2 is a railroad steam locomotive that has four coupled driving wheels followed by two trailing wheels, with no leading wheels....
Gladstone class

LB&SCR B1 Class

The London, Brighton and South Coast Railway B1 Class is a class of 0-4-2 express passenger steam locomotives, known from the name of the first, No....
passenger expresses of the London, Brighton and South Coast Railway

London, Brighton and South Coast Railway

The London, Brighton and South Coast Railway was a railway company in the United Kingdom from 1846 to 1922. Its territory formed a rough triangle, with London at its apex, practically the whole coastline of Sussex as its base, and a large part of Surrey....
remained in trouble-free service until 1933. A single leading axle (known as a pony truck) increases stability somewhat, while a four-wheel leading truck is almost essential for high-speed operation.

The highest number of leading wheels on a single locomotive is six as seen on the 6-2-0

6-2-0

In the Whyte notation, a 6-2-0 is a railroad steam locomotive that has an unpowered three-axle leading truck followed by a single powered driving axle....
Crampton

Crampton locomotive

A Crampton locomotive is a type of steam locomotive designed by Thomas Russell Crampton and built by various firms from 1846. The main British builders were Tulk and Ley and Robert Stephenson and Company....
type and the Pennsylvania Railroad

Pennsylvania Railroad

The Pennsylvania Railroad was an United States railroad, founded in 1846. Commonly referred to as the "Pennsy," the PRR was headquartered in Philadelphia, Pennsylvania....
's 6-4-4-6

6-4-4-6

A 6-4-4-6 steam locomotive, in the Whyte notation for describing locomotive wheel arrangements, is one with six leading wheels, two sets of four driving wheels, and six trailing wheels....
S1

PRR S1

The Pennsylvania Railroad S1 class steam locomotive was an experimental locomotive that was the largest rigid frame passenger locomotive ever built....
duplex locomotive

Duplex locomotive

A duplex locomotive is a steam locomotive that divides the driving force on its wheels by using two pairs of cylinders rigidly mounted to a single locomotive frame; it is not an articulated locomotive....
and 6-8-6

6-8-6

In Whyte notation a 6-8-6 is a steam locomotive with six unpowered leading wheels arranged into a three-axle leading truck, eight powered driving wheels, and six unpowered trailing wheels arranged into a three-axle trailing truck....
S2

PRR S2

The Pennsylvania Railroad's class S2 was a steam turbine locomotive. Only one prototype was built, #6200, delivered in 1944. The S2 was the sole example of the 6-8-6 wheel arrangement in the Whyte notation, featuring a six-wheel leading truck, eight driving wheels, and a six-wheel trailing truck....
steam turbine. Six-wheel leading trucks were not very popular. The Cramptons were built in the 1840s, but it wasn't until 1939 that the PRR used one on the S1.

Leading wheel

See also