Cylinder (steam locomotive)
Encyclopedia
Cylinder (engine)
A cylinder is the central working part of a reciprocating engine or pump, the space in which a piston travels. Multiple cylinders are commonly arranged side by side in a bank, or engine block, which is typically cast from aluminum or cast iron before receiving precision machine work...
s of a 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...
are the components that convert the power stored in the steam
Steam
Steam is the technical term for water vapor, the gaseous phase of water, which is formed when water boils. In common language it is often used to refer to the visible mist of water droplets formed as this water vapor condenses in the presence of cooler air...
into motion.
Cylinders may be arranged in several different ways.
Early locomotives
On early locomotives (e.g. Puffing BillyPuffing Billy (locomotive)
Puffing Billy is an early railway steam locomotive, constructed in 1813-1814 by engineer William Hedley, enginewright Jonathan Forster and blacksmith Timothy Hackworth for Christopher Blackett, the owner of Wylam Colliery near Newcastle upon Tyne, in the United Kingdom. It is the world's oldest...
) the cylinders were often set vertical
Vertical direction
In astronomy, geography, geometry and related sciences and contexts, a direction passing by a given point is said to be vertical if it is locally aligned with the gradient of the gravity field, i.e., with the direction of the gravitational force at that point...
and the motion was transmitted through beams, as in a beam engine
Beam engine
A beam engine is a type of steam engine where a pivoted overhead beam is used to apply the force from a vertical piston to a vertical connecting rod. This configuration, with the engine directly driving a pump, was first used by Thomas Newcomen around 1705 to remove water from mines in Cornwall...
.
Direct drive
The next stage (e.g. Stephenson's RocketStephenson's Rocket
Stephenson's Rocket was an early steam locomotive of 0-2-2 wheel arrangement, built in Newcastle Upon Tyne at the Forth Street Works of Robert Stephenson and Company in 1829.- Design innovations :...
) was to drive the wheels directly from steeply inclined cylinders placed at the back of the locomotive. Direct drive became the standard arrangement, but the cylinders were moved to the front and placed either horizontal
Horizontal plane
In geometry, physics, astronomy, geography, and related sciences, a plane is said to be horizontal at a given point if it is perpendicular to the gradient of the gravity field at that point— in other words, if apparent gravity makes a plumb bob hang perpendicular to the plane at that point.In...
or nearly horizontal.
Inside or outside cylinders
The front-mounted cylinders could be placed either inside (between the frames) or outside. Examples:- Inside cylinders, Planet locomotivePlanet (locomotive)Planet was an early steam locomotive built in 1830 by Robert Stephenson and Company for the Liverpool and Manchester Railway. The ninth locomotive built for the L&MR, it was Stephenson's next major design change after the Rocket. It was the first locomotive to employ inside cylinders, and...
- Outside cylinders, GNR Stirling 4-2-2GNR Stirling 4-2-2The Great Northern Railway No. 1 class Stirling Single is a class of steam locomotive designed for express passenger work. Designed by Patrick Stirling, they are characterised by a single pair of large driving wheels which led to the nickname "eight-footer"...
In the 19th and early 20th centuries, inside cylinders were widely used in the UK, but outside cylinders were more common in Continental Europe
Continental Europe
Continental Europe, also referred to as mainland Europe or simply the Continent, is the continent of Europe, explicitly excluding European islands....
and the USA. The reason for this difference is unclear. From about 1920, outside cylinders became more common in the UK but many inside-cylinder engines continued to be built.
Three or four cylinders
The demand for more power led to the development of engines with three cylinders (two outside and one inside) or four cylinders (two outside and two inside). Examples:- Three cylinders, SR Class VSR Class VThe SR V class, more commonly known as the Schools class, is a class of steam locomotive designed by Richard Maunsell for the Southern Railway. The class was a cut down version of his Lord Nelson class but also incorporated components from Urie and Maunsell's LSWR/SR King Arthur class...
- Four Cylinders, LMS Princess Royal ClassLMS Princess Royal ClassThe London, Midland and Scottish Railway Princess Royal Class is a class of an express passenger steam locomotive designed by William Stanier. They were Pacifics...
Crank angles
On a two-cylinder engine the cranksCrank (mechanism)
A crank is an arm attached at right angles to a rotating shaft by which reciprocating motion is imparted to or received from the shaft. It is used to change circular into reciprocating motion, or reciprocating into circular motion. The arm may be a bent portion of the shaft, or a separate arm...
, whether inside or outside, are set at 90 degrees
Degree (angle)
A degree , usually denoted by ° , is a measurement of plane angle, representing 1⁄360 of a full rotation; one degree is equivalent to π/180 radians...
. As the cylinders are double-acting (i.e. fed with steam alternately at each end) this gives four impulses per revolution and ensures that there are no dead centre
Dead centre
In a reciprocating engine, the dead centre is the position of a piston in which it is farthest from, or nearest to, the crankshaft. The former is known as top dead centre while the latter is known as bottom dead centre ....
s.
On a three-cylinder engine, two arrangements are possible:
- cranks set to give six equally spaced impulses per revolution – the usual arrangement. If the three cylinder axes are parallel, the cranks will be 120 degrees apart, but if the centre cylinder does not drive the leading driving axle, it will probably be inclined (as on most US three-cylinder locomotives and on some of GresleyNigel GresleySir Herbert Nigel Gresley was one of Britain's most famous steam locomotive engineers, who rose to become Chief Mechanical Engineer of the London and North Eastern Railway . He was the designer of some of the most famous steam locomotives in Britain, including the LNER Class A1 and LNER Class A4...
's three-cylinder locomotives in Great Britain), and the inside crank will be correspondingly shifted from 120 degrees. - outside cranks set at 90 degrees, inside crank set at 135 degrees, giving six unequally spaced impulses per revolution. This arrangement was sometimes used on three-cylinder compound locomotiveCompound locomotiveA compound engine unit is a type of steam engine where steam is expanded in two or more stages.A typical arrangement for a compound engine is that the steam is first expanded in a high-pressure cylinder, then having given up heat and losing pressure, it exhausts directly into one or more larger...
s which used the outside (low pressure) cylinders for starting. This will give evenly spaced exhausts when the engine is working compound.
Two arrangements are also possible on a four-cylinder engine:
- all four cranks set at 90 degrees. With this arrangement the cylinders act in pairs, so there are four impulses per revolution, as with a two-cylinder engine.
- pairs of cranks set at 90 degrees with the inside pair set at 45 degrees to the outside pair. This gives eight impulses per revolution. It increases weight and complexity, by requiring four sets of valve gearValve gearThe valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle...
, but gives smoother torqueTorqueTorque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
and reduces the risk of slippingLocomotive wheelslipLocomotive wheelslip is an event that affects railway motive power when starting from stationary.The greatest effort is required from a locomotive when starting...
.
Valves
The valve chests or steam chests which contain the slide valvesD slide valve
The slide valve is a rectilinear valve used to control the admission of steam into, and emission of exhaust from, the cylinder of a steam engine.-Use:...
or piston valve
Piston valve
A piston valve is a device used to control the motion of a fluid along a tube or pipe by means of the linear motion of a piston within a chamber or cylinder.Examples of piston valves are:...
s may be located in various positions.
Inside cylinders
If the cylinders are small, the valve chests may be located between the cylinders. For larger cylinders the valve chests are usually on top of the cylinders but, in early locomotives, they were sometimes underneath the cylinders.Outside cylinders
The valve chests are usually on top of the cylinders but, in older locomotives, the valve chests were sometimes located alongside the cylinders and inserted through slots in the frames. This meant that, while the cylinders were outside, the valves were inside and could be driven by inside valve gear.Valve gear
There are many variations in the location of the valve gearValve gear
The valve gear of a steam engine is the mechanism that operates the inlet and exhaust valves to admit steam into the cylinder and allow exhaust steam to escape, respectively, at the correct points in the cycle...
. In British practice, inside valve gear is usually of the Stephenson
Stephenson valve gear
The Stephenson valve gear or Stephenson link or shifting link is a simple design of valve gear that was widely used throughout the world for all kinds of steam engine. It is named after Robert Stephenson but was actually invented by his employees....
type while outside valve gear is usually of the Walschaerts type. However, this is not a rigid rule and most types of valve gear are capable of being used either inside or outside. Joy valve gear
Joy Valve Gear
Joy valve gear is a type of locomotive valve gear, patented in 1870, where the movement is derived from a vertical link connected to the connecting rod. The vertical movement is translated into the horizontal movement required by the valve spindle by a die block moving in a slide which can be...
was once popular, e.g. on the LNWR G Class
LNWR G Class
The London and North Western Railway G Class along with modifications that made them into G1, G2 and G2a classes, is a class of 0-8-0 steam locomotives designed for heavy freight work. They are known to railway enthusiasts as "Super Ds". This is because a large number of G1 class engines were...
.
Inside cylinders
On inside cylinder engines the valve gear is nearly always inside (between the frames), e.g. LMS Fowler Class 3FLMS Fowler Class 3F
The London Midland and Scottish Railway Fowler 3F 0-6-0T is a class of steam locomotive, often known as Jinty. They represent the ultimate development of the Midland Railway's six-coupled tank engines.- Introduction :...
.
Outside cylinders
On engines with outside cylinders there are three possible variations:- Inside valve gear driving inside valves, e.g. NER Class T2NER Class T2The North Eastern Railway Class T2, classified as Class Q6 by the LNER, is a class of 0-8-0 steam locomotive designed for heavy freight. 120 were built at Darlington Works between 1913 and 1921 to the design of Vincent Raven, based on the NER Class T and T1 .All passed into British Railways...
- Inside valve gear driving outside valves through rocking shafts, e.g. GWR 4900 ClassGWR 4900 ClassThe Great Western Railway 4900 Class or Hall Class is a class of 4-6-0 mixed traffic steam locomotives designed by Charles Collett. A total of 259 were built, numbered 4900–4999, 5900–5999 and 6900–6958. The LMS Stanier Class 5 4-6-0 and LNER Thompson Class B1 both drew heavily on design features...
- Outside valve gear driving outside valves, e.g. LSWR N15 ClassLSWR N15 ClassThe LSWR N15 class was a British 2–cylinder 4-6-0 express passenger steam locomotive designed by Robert W. Urie. The class has a complex build history spanning three sub-classes and eight years of construction from 1919 to 1926...
Three cylinders
There are three common variations:- Three sets of valve gear (two outside, one inside), e.g. LNER Peppercorn Class A2LNER Peppercorn Class A2The London and North Eastern Railway Peppercorn Class A2 is a class of steam locomotive designed for express passenger work by Arthur Peppercorn, the chief designer of the LNER after Edward Thompson...
- Outside valve gear driving the outside valves. Inside valve driven by Gresley conjugated valve gearGresley conjugated valve gearThe Gresley conjugated valve gear is a valve gear for steam locomotives designed by Sir Nigel Gresley, chief mechanical engineer of the LNER, assisted by Harold Holcroft...
, e.g. LNER Class A1/A3LNER Class A1/A3The London and North Eastern Railway LNER Gresley Classes A1 and A3 locomotives represented two distinct stages in the history of the British 4-6-2 "Pacific" steam locomotives designed by Nigel Gresley... - Three sets of inside valve gear (all valves inside), e.g. NER Class T3NER Class T3North Eastern Railway Class T3, classified Q7 by the LNER is a class of 0-8-0 steam locomotive designed for heavy freight. Five were built by the NER in 1919 and a further 10 by the London and North Eastern Railway in 1924.-Performance:...
Four cylinders
There are three common variations:- Four sets of valve gear (two outside, two inside), e.g. SR Lord Nelson ClassSR Lord Nelson ClassThe SR class LN or Lord Nelson class is a type of 4-cylinder 4-6-0 steam locomotive designed for the Southern Railway by Richard Maunsell in 1926. They were intended for Continental boat trains between London and Dover harbour, but were also later used for express passenger work to the South-West...
- Inside valve gear driving the inside valves directly and the outside valves via rocking shafts, e.g. GWR 4073 ClassGWR 4073 ClassThe GWR 4073 Class or Castle class locomotives are a group of 4-6-0 steam locomotives of the Great Western Railway. They were originally designed by the railway's Chief Mechanical Engineer, Charles Collett, for working the company's express passenger trains.-History:A development of the earlier...
- Outside valve gear driving the outside valves directly and the inside valves via rocking shafts, e.g. LMS Princess Coronation ClassLMS Princess Coronation ClassThe London Midland and Scottish Railway Coronation Class is a class of express passenger steam locomotives designed by William Stanier. They were an enlarged version of the LMS Princess Royal Class. Several examples were originally built as streamlined, though this was later removed...
Other variations
Geared steam locomotive
A geared steam locomotive is a type of steam locomotive which uses reduction gearing in the drivetrain, as opposed to the common directly driven design....
s which may have only one cylinder.
The only conventional steam locomotive with one cylinder that is known is the Nielson One-Cylinder Locomotive.