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Testing Locomotives

Out on the road from Swindon. . . . . . .

A “King” class locomotive under test fitted with an indicator shelter with a 20-coach train including the 1901 dynamometer car behind the tender. Photo: Great Western Trust.

George Jackson Churchward (1857-1933). Churchyard was the Chief mechanical engineer of the Great Western Railway between 1902 and 1921. His use of longer stroke, longer valve travel, tapered boiler and higher steam presure showed the way to other designers in the first half of the 20th century. Image © National Railway Museum / Science & Society Picture Library -- All rights reserved

The GWR’s Chief Mechanical Engineer G J Churchward had ambitious plans for new designs and locomotive development at the start of the 20th century. He needed a range of measurements to be taken on the move to inform future design practice. In 1901 he built his 45 feet long eight-wheel dynamometer car to run with trains under test. It had an additional flangeless recording wheel linked to instruments to run at 440 revolutions per mile. This vehicle remained in use until the 1960s.

Hitherto, testing of Swindon’s newly-built locomotives on the move had meant a short trial run on the works sidings before a longer run out on the main lines. Locomotives usually ran light engine tender-first at a moderate speed in a westerly direction on the Bristol line for the 10 miles to Dauntsey or 17 miles to Chippenham before returning at a greater, even high speed to Swindon. A similar 12-mile test was also done on the South Wales line to Somerford and back. As a privilege, the gang which had assembled a new locomotive was allowed to ride on the footplate for these trial runs. Similarly, workshop staff and apprentices sometimes rode with newly-overhauled locomotives so that a “snag list” could be compiled. This could mean as many as six people on the footplate, not ideal for the shovel-wielding fireman. For guests on the footplate, the tender-first running wasn’t popular given the amount of coal dust swirling about, and some chose to ride on the running board at the rear by the smokebox hanging onto handrails! The next stage after overhaul was the “running-in turn” on a modestly-paced local parcels or stopping passenger service.

There was one test which could have ended badly, but didn’t. In May 1906, Swindon’s Assistant Works Manager Charles Collett – later Churchward’s successor and designer of the “King” and “Castle” classes amongst others – wanted to test if a new ex-works engine could run at 100 mph. “Saint” class 4-6-0 number 2903 was chosen for the trial on a day when Churchward wasn’t around. It was taken light engine to Stoke Gifford, turned on the triangle, and then fired up for the unofficial test run. On the footplate with Driver H J Robinson were Collett, Locomotive Inspector George Flewellen and Shop Foreman Evans. The loco was stopped at Chipping Sodbury on the return trip until it received “line clear” for the 20 mile stretch as far as Wootton Bassett. It was then driven at high speed down the nine-mile descent “racing ground” through Hullavington and Little Somerford. Stopwatch readings from the footplate using mileposts showed that a speed of 120 mph might have been reached for some distance. It wasn’t until 26 years later that Collett owned up to the trial by confirming the details when asked by the “Railway Magazine”. He felt that a speed of 120 mph had been achieved from his timings. The 4½ miles between the signal boxes at Hullavington and Little Somerford was covered in two minutes and this gave rise to speculation that 135 mph may have been reached at one point! Certainly, a speed of well over 100 mph was achieved, an impressive result for a new light engine.

The testing plant for stationary work, and the use of dynamometer cars out on the road were the main means of testing, but there was one more method used. That was the “indicator shelter”, a wood or metal structure with portholes built around a locomotive smokebox which could contain technicians and instruments for testing out on the road. Instruments connected to cylinders and the smokebox were monitored in real time by doughty technicians working in an unpleasant very hot and draughty environment on the move.

“County” class locomotive 1009 “County of Carmarthen” carrying the indicator shelter and fitted with an experimental stovepipe chimney in 1955 for drafting and blastpipe tests. Photo: British Railways.

Dynamometer cars were built by three other railway companies. One of these, the 1906 car built by the North Eastern Railway was used for the speed record-breaking run of “Mallard” in 1938. This car and the GWR’s 1901 car were extensively used in the 1948 locomotive exchanges when British Railways was seeking to find out which of the passenger and freight locomotives it had inherited performed best on which lines, and which of their characteristics should be included in the design and building of the new BR Standard classes. Thus, Southern Region locomotives were seen as far north as Inverness 600 miles away from their usual territory, and trainspotters all over Britain were delighted to see strange “cops”!

Following the end of steam, BR Research Division started to use a closed line which was turned into the 13¾ mile Old Dalby test track near Melton Mowbray. After an upgrade to allow high speed running, the line has been extensively used for tests of pantographs, permanent way maintenance, crashworthiness, train control and warning systems, adhesion, braking and for a variety of new rolling stock. It is fitted with overhead line equipment and third and fourth rail electrification. Old Dalby has been operated by Network Rail since 2013. Another test facility, the Rail Innovation & Development Centre at Tuxford, Nottinghamshire offers a ten-mile single track for training and research purposes. In addition, around eight British universities work with Network Rail on rail research and development projects.

Mike Peart

About the author: Mike Peart is a former railwayman on British Railways (Western Region). He is co-author of Volumes 3 (Freight Marshalling Yards), 4 (Level Crossings) and 5 (Train Detection and Control) of the “History & Development of Railway Signalling in the British Isles” series, and Trains of Hope”, all published by The Friends of the National Railway Museum. He’s been an active Friend of the NRM since 1994 and was one of the four “schoolboy” founder members of the Great Western Society (Didcot Railway Centre) in 1961.

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