Steam Powered Multiple-Unit Trains
This page is inspired by the restored railmotor No.93 and auto-trailer No.92 plus the use of auto-trains with
But first, a little history to set the scene.
At one time virtually all railways operated on the principle that a heavy steam locomotive would be at the front hauling one or more goods wagons and / or passenger carriages. For the train to reverse its direction of travel the locomotive would usually need to be detached from the front of the train and either it or another locomotive be attached at the other end of the train. All this took time and needed extra staff to perform these functions.
As early as the late 1840's experiments were underway with passenger carriages that included an integral steam locomotive. These self-propelled steam trains were cheaper to operate and therefore more suited to low capacity quieter branch line services. They were often called Railmotors.
Railmotors came in two basic variants, these being of a passenger carriage with a small steam locomotive attached as a semi-trailer at one end, and a passenger carriage with a fully internal steam locomotive at one end. The latter type would sometimes use vertical boilers as these required less floor space.
Typically railmotors included rudimentary driving controls at the unpowered end of the passenger carriage, as this made it possible for the train driver to always be at the front - even when the steam traction unit was at the back. Nowadays we would call the small dedicated area located and used by the train driver at the unpowered end of the railmotor a driver's cab, however as these areas were already known as vestibules this name remained. Mechanical cables (wires), rodding and / or compressed air connected the driving controls at the unpowered end of the carriage to the steam power plant. The driver also controlled braking and could sound the whistle. Only the train driver would be located at the unpowered end of the carriage, the fireman always stayed with the power plant whilst the guard's duties were to serve the passengers - and sometimes also collect the fares. When the train driver was working at the unpowered end of the carriage the fireman had to perform extra duties in addition to adding coal to the fire and attending to the general needs of the steam power plant. An example of the extra duties was to release the brakes, because the braking system required steam to create a new vacuum and the ability to operate the relevant control lever had not been facilitated at the unpowered end of the carriage. The three members of staff (driver, guard and fireman) communicated with each other via a system of bell codes.
Part of the impetus behind the use of railmotors was the advent of electric street tramway and (nascent) motor bus competition which had seriously eroded the numbers of passengers using the railways for short local journeys. In many areas the street trams were operated using electricity and usually comprised single self-propelled railcars which like railmotors were fitted with driving controls at both ends. This meant that they could reverse direction of travel with ease. These features made them more productive and much cheaper to operate than steam trains.
Internally railmotors often featured an ambiance that was a mix of railway and tramway with features such as open saloon style seating and reversible walkover seat backs which meant that most passengers could face the direction of travel when seated.
On many routes the railmotors attracted so many extra passengers that additional passenger accommodation was required. For this the railways tended to use unpowered passenger carriage(s) which had been fitted with the same rudimentary driving controls to an end vestibule as the unpowered ends of the railmotors. In this way the train driver could continue to control the train from the front, even though the power plant was in the 'other' passenger carriage. This concept allowed the trains to operate in 'push-pull' mode.
A disadvantage of railmotors was that they were not normally very powerful, usually being just about able to power themselves plus (on some examples) an extra carriage. Sometimes adding an extra carriage made the trains so sluggish that they then had difficulty keeping to the timetable. This made them somewhat inflexible, as they were effectively unable to cope with greater than expected passenger demands - an example being busy market days on an otherwise lightly-used rural branch line. Often it was cheaper and easier to run the one mixed train which comprised both passenger carriage(s) and a few goods wagons.
Whilst in theory a way around the limited capacity of the railmotor would have been to join two (more more) together to form a longer train (complete with unpowered passenger carriages) this solution was not adopted, one reason being that a way for a single train driver to control multiple steam power plants from one set of controls at the front of the train had not been invented. (This was possible with electric trams and trains - but not steam trains). Therefore each railmotor would still require a driver and fireman - whilst using a more powerful locomotive plus unpowered passenger carriages only required two members of locomotive staff.
Other railmotor disadvantages include that when being serviced they took up much valuable workshop space (after all, they were usually longer than steam locomotives) and the proximity of the boiler made it difficult to keep the passenger space clean.
The Great Western Railway (GWR) introduced its first railmotors in 1903, and having found the concept to be viable by 1908 it had built a fleet of 99 railmotor carriage units plus 112 interchangeable power units which could be swapped between railmotors to suit maintenance needs.
However, because of their not being powerful and limited passenger capacity, in 1905 the GWR experimented with adding extra equipment to some small tank engines and separate passenger carriages so that they could work as fixed units where the driver could control the steam locomotive from the far end of the passenger carriage(s), eliminating the need for it to run round to the other end of the train at the end of each journey. These became known as auto-trains, with the carriages which were fitted with the vestibule and controls for the driver also being known as auto-coaches or auto-trailers.
With trials of auto-trains having proven successful, withdrawals of the railmotors began in 1914 and by 1935 they all had either been scrapped or converted to auto-trailers. The design proved very successful, with 163 examples in total - and the last being built by British Railways as late as 1954!
In addition to creating an 'almost' self-powered train where the power unit was powerful enough to haul several passenger carriages another advantage of the auto-train concept was that the locomotive could be detached for maintenance - or for use on a goods train.
GWR Railmotor No.93
Steam Railmotor No. 93 was built in March 1908. In November 1934 she was condemned as a steam railmotor and was converted into locomotive-hauled auto-trailer No.212. The conversion works included her losing her steam power plant and the train control equipment being modified to control an external locomotive attached at the end of the carriage where the internal steam power plant had previously been located. She was launched in her new guise in May 1935.
In 1956 she was withdrawn from passenger service and rather than being scrapped was used by British Railways as a mobile office. In 1970 the Great Western Society bought her with the long-term desire of restoring her to her original steam railmotor format. This was completed in 2011. Included in the required works was the fabrication and fitting of a brand new steam power unit.
These images come from several visits to the Didcot Railway Centre, in very different weather conditions.
The end with the steam traction unit, on the branch line at the Didcot Railway Centre.
The unpowered end, seen whilst passing Frome Mineral Junction signal cabin the branch line.
Another view of the end with the steam traction unit, shortly after having started to depart from the branch line station. Called Didcot Halt, this which represents a typical GWR halt (request station) with a very basic corrugated metal platform shelter. In addition to waste gases being expelled via the chimney spent steam can be seen being ejected from below the cylinders.
Partially inside the transfer shed at the branch line's other terminus station which is called Burlescombe. The transfer sheds were where goods were transferred between GWR broad gauge trains and the standard gauge trains operated by the other railway companies.
A study of the powered end of the railmotor as seen as it arrived at Burlescombe station. On the far left is the footplate. The vertical boiler is directly below the chimney. The circular hatch cover next to two windows is where the railmotor takes on water. To the right are the twin doors of the luggage area, next to that is the smaller passenger saloon and then the passenger doorway, seen here with the guard looking through the open window. Just visible on either side of the door are some handrails, these are seen more clearly in the next image.
The (former) smoking compartment, note the 'smoking' legend on the window glass. The passenger doorway is closed, either side of it can be seen some handrails, these are used (along with steps, only one of which is seen here) when the railmotor calls at halt-type stations that do not have raised platforms.
A study of the luggage area doors. The aim was to show the fully lined livery, but also visible are reflections of people on the platform and part of the station's name board sign.
A study of one side of the powered bogie. No. 93 uses outside Walschaert valve gear with balanced overhead ‘D’ type slide valves. The driving wheels are 4ft 0in in diameter.
The powered end of GWR railmotor No.93 at Oxford Road station on a wet day at the Didcot Railway Centre.
The unpowered end of GWR railmotor No.93 at Oxford Road station on a wet day at the Didcot Railway Centre.
GWR railmotor No.93 carries three coats of arms. This one is of the Great Western Railway.
The identity of this coat of arms remains unknown.
The identity of this coat of arms remains unknown.
Inside GWR Railmotor No.93
Internal view of the larger passenger saloon, which was for non-smoking passengers.
The seats have been upholstered using chocolate brown diamond pattern fabric.
The vestibule (compartment) at the far end of the railmotor includes the required
mechanical apparatus for the train driver to control acceleration, braking and sound the whistle.
Another internal view of the larger passenger saloon, looking in the opposite direction..
At the far end of the image it is just possible to see inside the much smaller passenger compartment which was dedicated
to passengers who liked to smoke - of course nowadays the entire train is designated as being 'non-smoking'.
Most of the transverse seats were of the 'walkover' type. These had movable backs that allowed passengers (if they wished) to always face in the direction of travel. This type of seating was more commonly found in trams and as far as is known the GWR only fitted these to its railmotors and auto-trailers. For the restoration project 40 walk-over seating units were sourced from 1920's trams being scrapped (because of fleet replacement) on the Glenelg tramway which serves the Australian city of Adelaide.
The window blinds feature the GWR logo (this is easiest to see in the larger versions of this image).
The chain is the communication cord, this was used by passengers to stop the train in an emergency.
Inside the luggage area, showing two of the folding seats, one of which is in the down position. Behind the door is the vertical boiler.
The GWR called the folding seats drop seat and as far as is known this type of seat was first used in 1934 and only fitted in railmotors and auto-trailers.
Inside the luggage area, showing the ceiling light, ventilators and grab rail.
Inside the luggage area, showing a folding seat plus the extra wide luggage doors.
A footplate view (as seen from the station platform) showing the top part of the vertical boiler.
A footplate view (as seen from the station platform). The fireman is adding coal to the fire. Because of space constraints and also the extra duties of the fireman when the train driver was in a cab elsewhere along the train the firemen tended to only add coal to the fire during stations stops.
A footplate view (as seen from the station platform) showing the vertical boiler in a single image.
Because of the very confined space two images were taken inside the driver's cab at the trailing end of the railmotor.
This image shows part of the regulator handle, the brake pressure vacuum gauge, the whistle cord and the battery electric bell which is used for sending coded messages to the fireman. The sign says one ring for start, two rings for stop, three rings for brakes off.
The other photograph which was taken inside the driver's cab at the trailing end of the railmotor shows the handbrake (this is used when stationary) and the brake lever which is used when there is a desire to reduce speed (ie: slow down!)
The main passenger entrance / exit is located between the larger and smaller saloon seating areas. Next to the door can be seen an electric bell unit. This allows the guard to send coded messages to the train driver and fireman. Similar bell units are also located elsewhere on the railmotor and on auto-trailers.
GWR Auto-Trailer No.92
Auto-trailer No.92 was built in 1912. In 1957 it was withdrawn and rather than being scrapped was used as a mess room at Cardiff Docks. In 1969 it was bought for preservation by the Great Western Society. This is the only original auto-trailer of the steam railmotor era to have survived
It is not known how much the corridor connection would have been used in the days when No.92 was operated as an auto-trailer, however research has suggested that since it has braking equipment it (and other auto-trailers which had corridor connections) would sometimes be used instead of ordinary brake carriages on longer trains which were hauled by a steam locomotive. Apparently the vacuum brake lever still worked when these auto-trailers were attached to ordinary trains, although the main reason for their suitability for being used in this way would be because (as with brake vans and ordinary brake coaches) they also had hand brakes.
Auto-trailer 92 is 70ft (21.33m) long. It has a 61ft (18.59m) wheelbase and has two 9ft (2.74m) wheelbase equalising beam bogies, which are commonly known as 'American' bogies. The large saloon features five pairs of walkover seats, with the end seats fixed, and two pairs of 9ft (2.74m) long longitudinal seats. The small saloon also contained five pairs of walkover seats, with the end seats fixed, and one pair of longitudinal seats 4ft 6in (1.37m) in length. In total there are 70 seats.
As with the railmotor, the inside of auto-trailer No.92 has been restored to what is believed to be its "as new" condition.
The corridor connection end of auto-trailer No.92 as seen when not attached to anything else.
The cable seen hanging from the top of the carriage is for the whistle.
Inside the luggage area
The corridor connect to the next carriage is at one end of the luggage area.
Inside the driver's cab, front left view; this and the next few images were taken whilst auto-trailer No.92
was stationary inside the Transfer Shed. Limited space did not allow a single image showing the entire cab.
Inside the driver's cab, front centre view showing the hand brake (see below) and the regulator. This connects to rodding under
the carriage which (at its other end) is connected to similar rodding on the next carriage (or steam engine) that makes a mechanical
connection with the steam traction unit. Its purpose is to control the steam engine in a way which facilitates movement - it is
pushed left to accelerate and right to coast. The principle is similar to the accelerator pedal on a rubber-tyred road vehicle.
Inside the driver's cab, front right (top). The hanging cable is used by the train driver to sound the whistle.
Inside the driver's cab, front right (bottom). Visible here are the hand brake (which is currently being used to prevent the
auto-trailer from moving), the foot pedal for the gong plus the normal service brake (red coloured lever) which the train driver
uses to slow down, for instance to stop at stations or red signals.
To comply with the law the brake lever invokes the brakes on the entire train - braking systems which
simultaneously apply the brakes on every passenger carriage throughout the train has been a legal requirement
since the 1889 Regulation of Railways Act. Note that the law was different for for goods trains.
Railmotor No.93 And auto-trailer No.92 Working Together
The restoration of steam railmotor No.93 and auto-trailer No.92 was completed in May 2013.
Their ‘home’ is now a specially constructed shed at the Didcot Railway Centre, where they are sometimes used in passenger service. They also sometimes carry passengers at other living museums and even on selected mainline railway routes.
When they run together they form what effectively is a steam multiple-unit train, in which guise they act as forerunners of the diesel and electric multiple-unit style trains which are well-known today.
The restoration of these two vehicles was partially funded by the Heritage Lottery Fund. It was carried out between 2007 and 2013 at the Llangollen Railway. The wood-panelled vehicles have been painted in crimson lake livery with white roof and burnished motion as was used between 1912 and 1922. This is perhaps less well-known than the famous GWR Chocolate and Cream livery, however it is possible that in the future they will be repainted in other authentic GWR liveries. Their interiors feature varnished oak, polished brass and original diamond pattern chocolate brown upholstery.
railmotor No.93 with matching auto-trailer No.92 - the direction of the steam suggests that the railmotor is leading the train.
Railmotor No.93 with matching auto-trailer No.92 - the direction of the steam suggests that the auto-trailer is leading the train.
A side view of the ends No.93 and No.92
A study of the ends No.93 and No.92, the orange arrow points to the coupling rod between the two vehicles
- this connects the regulator rod under No.92 with the regulator rod under No.93
The train in the pedestrian area awaiting a green signal to return to the Branch Line after the train crew's lunch break.
At the top of the carriage can be seen a circle-shaped warning gong. This is activated by a foot pedal, as seen in a different image.
The reason for the gong is that it was felt that the train's whistle (which is attached to the steam traction unit) would be too far away
to act as a warning / alert sound.
A film showing steam railmotor No.93 in action at the Didcot Railway Centre.
A film showing steam railmotor No.93 plus auto-coach No.92 in action at the Didcot Railway Centre.
A forward view film showing the train driver driving steam railmotor No.93 on the longer demonstration track at the Didcot Railway Centre. This line mostly parallels a section of mainline railway and also seen are a Class 180 Adelente and a Class 253 (or 254) High Speed Train.
The images below show a different GWR auto-coach, this being Hawksworth W231 which dates from 1951 and was the last design of auto-coach. It is painted in British Railways Crimson and Cream livery which is also known by its nickname of blood and custard.
Because GWR auto-coach technology was universal within the GWR fleet, it was possible for the Didcot Railway Centre to use W231 with steam railmotor No.93 to test that the latter's remanufactured auto gear was indeed working correctly. Despite the very great age difference and historical inaccuracy the trial found that all was indeed well with No.93.
Auto-coach W231 leading a train arriving at Oxford Road station. The train was actually powered by a British Rail diesel engine, however as the braking system was compatible it was still possible for the train driver in the leading vestibule to control the braking as the train arrived.
Inside the large passenger saloon.
Beyond where the boy is standing are a passenger door vestibule, the smaller passenger saloon and a goods area.
The seats in the smaller passenger saloon have a differently coloured upholstery.
A study of the straphangers and their supporting metal brackets. These were only located in the areas which had longitudinal seating..
The end of the larger passenger saloon that is next to the train driver's vestibule.
One passenger door on each side of railmotors and auto-coaches included retractable steps which would be deployed
at tramway style stops that did not have raised platforms. In this image the steps are seen stowed away below the
body so that the auto-coach can call at a station which has a raised platform.
Image & license: Geof Sheppard / Wikipedia encyclopædia CC-BY-3.0 https://commons.wikimedia.org/wiki/File:GWR_coach_A38_231_retractable_steps.jpg.
Push-Pull Auto-Trains - A Steam Locomotive With Auto-Trailer(s)
Trains formed of auto-carriages and a suitably equipped steam locomotive are known as auto-trains. Steam locomotives provided with the equipment to be used in an auto-train are said to be auto-fitted. The reason why auto-trains came into existence is described near the start of this page.
Auto-trains came in various configurations with between one and a maximum of four unpowered trailer carriages. Often when there were two auto-carriages such trains would be formed with the locomotive between them. Alternatively both trailer carriages could be attached at one end of the locomotive, however through experience it was found that only one intermediate trailer could be located between the auto-coach and locomotive without there being so much slack in the mechanical linkings that the concept started to become unworkable.
With their single traction unit plus several unpowered trailers and ability to travel in either direction with the train driver always at the front auto-trains effectively act as steam powered examples of a type of train that became commonplace on our railways when diesel and electric replaced steam traction.
However with diesel and electric traction it was usual to examples forerunners of trains which have one powered carriage plus several unpowered trailer carriages. Many British Railways Many diesel
Some Auto-Train Examples
The simplest auto-train combination - one auto-fitted locomotive (0-4-2 No.1466) plus one auto-coach (W231).
The arrow points to the apparatus just below the solebar of an auto-fitted locomotive
in to which an auto-coach coupling rod is fitted when running in auto-train mode.
An auto-coach coupling rod stowed away on an auto-coach when not in use.
Low winter sunshine catches an auto train with two auto-trailers (one each in front and behind the locomotive)
on the South Devon Railway as it approaches Nappers Halt.
Image & license: Geof Sheppard / Wikipedia encyclopædia CC-BY-3.0 https://commons.wikimedia.org/wiki/File:Nappers_Bridge_-_5542_between_two_auto_trailers.JPG.
A West Somerset Railway auto-train with both passenger carriages at the front of the engine
departs from Watchet on a journey to Donniford Halt and Bishops Lydeard.
Image & license: © Rabbi WP Thinrod / Geograph Project. CC BY-SA 2.0 http://www.geograph.org.uk/photo/636457.
In an era before electric and oil (diesel or petrol) powered trains became commonplace steam railmotor plus auto-trailer trainsets were the only examples of self-powered trains that consisted of solely passenger carriages. However the requirement for a train crew for each such trainset meant that it was not viable to join up several of these trainsets to form a true multiple-unit train. Nevertheless, they still acted as forerunners of the many two carriage diesel and electric trains that British Railways built which comprised just one self-powered carriage and one unpowered trailer carriage.
In their era auto-trains, which featured a single traction unit plus several unpowered trailers and could travel in either direction with the train driver always at the front, effectively acted as steam powered examples of a type of train that became commonplace on our railways when diesel and electric replaced steam traction. However with steam traction the powered vehicle did not also carry passengers and it was only ever possible for one train crew to control a single locomotive. By way of contrast with first generation diesel and electric trains it was usual for the entire train to be formed of passenger carriages (typically one powered [motor] coach with two or three unpowered trailers) and to create longer trains formed of several such trainsets that still have just one driver controlling all the traction units.
By the late 1920s steam railmotor technology had advanced enough to make double engined railcars possible - these featured an engine at each end and a single coal powered boiler. At least one of these comprised an articulated trainset where the trailer shared one of the powered bogies. (Built by Sentinel). Also, by then electric train control technologies had advanced enough for a single train driver to control a long self-powered electric train that included many traction units (for example: on urban electric railways in several British cities). However this was still an era when steam reigned supreme and trains which used liquid fuel engines (diesel / petrol) were extremely rare.
Who knows whether a multi-engine electronic control system could have been made to work with steam traction? Of course the coal boilers would still have needed a fireman, but...
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This page last updated 5th March 2017.