Mobile Test Plant

Upon its formation in 1923 the London Midland & Scottish Railway inherited dynamometer cars from the London & North Western and Lancashire & Yorkshire railways, which had been completed in 1909 and 1913 respectively. Of the two, the L&YR vehicle was the more sophisticated, but both measured drawbar pull in terms of the deflection of a powerful spring and in 1928 the accuracy of the former became suspect on account of hysterisis (although it continued in service until 1967).

During the 1930's the LMS planned elaborate new locomotive testing facilities, including a new  comprehensive test train (known as the Mobile Test Plant) and the Locomotive Testing Station at Rugby which was a joint project with the LNER. Both railways planned new dynamometer cars and ordered three Swiss Amsler hydraulic dynamometers, the third for incorporation in the stationary test plant at Rugby.

Construction of the new LMS dynamometer vehicle commenced at Derby C&W Works shortly before the outbreak of war in 1939, but it was not completed until a decade later, soon after the formation of British Railways in January 1948. Initial trial runs were made in late April 1949 and it ultimately made 1,086 scheduled test runs between May 1949 and July 1975, covering an estimated 147,616 miles. Although originally designed to test steam locomotives, in the event it was also employed to evaluate diesel and electric locomotives and also the Prototype High Speed Train on the East Coast Main Line in June 1973.

During its working life this vehicle has carried several liveries, i.e. BR 'blood and custard' , BR maroon and latterly the BR Research Department 'Red and Blue'. Restored in 1979 it has been lettered LMS in recognition of its origins although not actually completed until after Nationalisation in 1947.

The above information is provided - courtesy of the National Railway Museum.

It is now cosmetically restored into its former LMS livery and has recently (June 2011) moved from Barrow Hill to the MRC at Butterley, Derbyshire.

A number of tests were carried out with the London Midland (LM) Region Mobile Test Plant which enabled tests to be conducted on the road at constant speed. 

A description of the Mobile Test Plant 

The Mobile Test Plant comprised the LM Region No.3 Dynamometer Car M45049, Mobile Test Units Nos. 1, 2 and 3 M45053, M45054 and M45055 and a special locomotive corridor tender which were all designed and built by the LMS at Derby C&W Works in 1938 but not completed until after WW2.

The main Instrument Room in the Dynamometer Car, accommodated the Control Desk for the Mobile Test Units, as well as housing the Amsler Recording Table which provided a continuous record of speed, drawbar pull, horsepower etc. The various multi-point thermometers, draught gauges etc. were also housed in this room.

A smaller room, the Indicator Compartment, contained a Farnborough Indicator which furnished indicator cards on a crank angle base, whilst another compartment contained apparatus for continuous smoke box gas sampling during tests.

The Mobile Test Units, were electrically braked vehicles equipped with generators which could automatically keep the speed constant, irrespective of gradient, by varying the load as required. Externally they were identical but the gearing and electrics were designed for different speed ranges, these were up to 50, 90 and 120 mile/h, although they could and usually were, used in any combination.
The units were capable of being used singly, in pairs or all three together, according to the speed and braking force required for each controlled test. Control was applied from the Dynamometer Car and speed could be regulated by hand or automatically.

The special tender was equipped with a coal space and a corridor. The coal space would be used for test coal in one hundredweight (cwt.) bags, (approx. 50 kg) and for loose coal required for periods not under test and for standby purposes. A water meter was fitted to give the amount of water taken from the tender.

Look here for a contemporary account of the MTU in action.

Here are some pictures of the units which made up the Mobile Test Plant taken from the early BR test bulletins and the official pictures of them in Derby C&W Works when new.

All photos are from the author's collection except where indicated otherwise

The ex-LMS dynamometer car No:3, running number M45049. This was still in use when the author joined the Testing Section in the early 1970's

Test Car 3, as the dynamometer car became known, is in the formation of the prototype HST as it leaves Derby in February 1973. It is now restored and housed at Barrow Hill as part of the National Collection.


Inside Inside the dynamometer car showing the Amsler recording table with Sid Cowley (in white coat) monitoring the performance of a Derby-built Sulzer Type 2 diesel locomotive No: 5008 during the late 1950's drawgear The load-measuring drawgear from the dynamometer car
Control room The dynamometer car's control room for the MTU's The special tender with a coal space and corridor
45054 One of the three Mobile Test Units M45054 pictured as new in the C&W Works at Derby. Two of these were broken up in 1976 but No:45053 is preserved at the NRM although it is in poor condition. 45054 Another view of the MTU
Frames A picture of the underframe of the MTU with diesel engine in situ generator The generator of an MTU which was axle-hung to provide resistance to motion, rather like the rheostatic brake of today, when fed from the on board alternator
Engine room The MTU's engine compartment Engine compartment The MTU's electrical control room where the trailing load could be varied
From above 45054 viewed from above showing the ventilation hatches Black Five Here are two MTU's on the rear of a Stanier Class 5 loco on test in August 1949 pictured at Mitre Bridge carriage sidings. Note the LMS-liveried special tender.
Armathwaite The prototype 'Deltic' on test on the S&C circa 1955, has a couple of MTU's in the train. Note Dynamometer Car No:3 behind the loco in 'blood & custard' livery D8000 negotiates Derby N Jcn with the Dynamometer Car No:3 and an MTU in tow in 1958 - now in BR maroon livery.
At Derby in the 1970s

John Senior


The MTU's survived until 1976 and at least one was re-painted into R&DD red and blue livery. M45053 is part of the national collection at the NRM although in very poor state of preservation, having been kept outside for a number of years.

In 2011, having been stripped of its asbestos it was moved to the Embsay and Bolton Abbey railway where its renovation and restoration is being considered.

The ex-LMS dynamometer Car No:3, running number M45049, is preserved as part of the National Collection by the NRM and until recently was at Barrow Hill where it was re-painted into LMS crimson lake livery. It has now been re-located to the MRC at Butterley where it is housed in the Museum at Swanwick Junction.


M45053 at NRM York on 14 December 2002

Ben Williams

MTU Another view of M45053 at NRM York on 14 December 2002

Ben Williams

In a sorry state



M45049 restored at Barrow Hill

Martin Barnsdale

Under cover In the museum at Swanwick Jcn on 22 June 2011


45054 and 45055 were sent to Cashmores at Great Bridge in 1976 where they were cut up.


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