Water trough

"Water trough" redirects here. For the trough used to provide drinking water for animals, see Watering trough.

New York Central Railroad's Empire State Express takes on water from the track pan at Palatine, New York, in 1905

A track pan (American terminology) or water trough (British terminology) is a device to enable a steam railway locomotive to replenish its water supply while in motion. It consists of a long trough filled with water, lying along a flat stretch of railroad/railway track between the rails.

When a steam locomotive passes at speed over the trough, its water scoop can be lowered, and the speed of forward motion forces water into the scoop, up the scoop pipe and into the tanks or locomotive tender.

Track equipment

Ramsbottom water troughs on a four-line stretch of the LNWRs West Coast main line in 1904

Main line steam locomotives consume considerable volumes of water, and the tender or side tanks need to be replenished at intervals. To travel long distances non-stop, water must be replenished without stopping.

In 1860 John Ramsbottom, a Victorian locomotive engineer, devised the water trough/track pan to meet this need. It is a very long (several hundred yards) open-ended shallow trough laid between the rails. A nearby water source is needed to recharge the trough as passing trains take water. The entire length of the installation must be on level track, with a short section of rising track at each end to ensure that the water is retained. As trains needed to be moving at some speed to pick up enough water, a suitable separation between trough locations and commercial stopping points is essential.

The first installation was brought into use on 23 June 1860 at Mochdre, Conwy, on the North Wales main line of the London and North Western Railway (LNWR) about mid way between Chester and Holyhead.

The siting of the troughs requires a long enough length of straight and level track (although very large radius curves could be accommodated). There must be a good water supply nearby. In hard water areas, water softening plant may have been considered necessary.

Locomotive equipment

A scoop is fitted to the underside of the locomotive's tender (or the locomotive itself in the case of tank locomotives) in such a way that it can be raised or lowered, by a hand operated screw or a power mechanism. The scoop feeds into a vertical pipe that discharges into the water tank.

The scoop needs to be lowered at speed at the correct location - shortly after the start of the trough - and raised again when either the tank is full, or at the end of the trough. Lineside indicators are provided to assist engine crews in determining the location; in the UK it was a large white rectangular board with a black horizontal zigzag marking. On American railroads, illuminated trackside signals were employed for night-time usage, to indicate the start and approaching end of the track pan.

Venting on the tender needed to be free to allow a high rate of release of expelled air from the tank. Tank locomotives were generally fitted for picking up in either direction, but tender locomotives generally picked up in the forward direction only.

Operational considerations

The LNWR quickly installed water troughs at other locations, but other companies were slow to adopt the new apparatus. The Great Western Railway did so from 1895, and subsequently all the major railways in Great Britain, with the exception of the lines south of the River Thames, installed the equipment. Taking water at speed results in considerable spray behind the scoop; this risks drenching passengers in the leading vehicles, and in Great Britain it was customary for the guard or other traincrew to warn passengers in the first coach to keep the windows closed. In one incident on the LMS railway in Britain, two streamlined trains with "Coronation" class locomotives happened to pass each other at a water trough when one of the trains was taking on water. The other train suffered broken windows due to lumps of tender coal scattered by the spray and the complaints from drenched passengers caused the management to retimetable the trains to ensure this could not happen again. Vaughan says that the Royal Train when conveying royalty was not permitted to be passed by another train in a section where there was a water trough.

Vaughan states that the GWR investigated the effectiveness of varying train speed, and found that 45 mph was the optimum speed; but water could be picked up successfully as low as 15 mph. At that speed 944 gallons could be picked up in 440 yards, but Vaughan suggests that this is a low theoretical figure, and that it overlooks the bow wave effect which enables a greater take-up rate. There was a significant resistance to the forward motion of the engine during the process, enough to require special care by the driver to avoid problems on unfitted freight trains.

The considerable water spray made track maintenance difficult, and the physical trough equipment limited access for packing sleepers, exacerbating the problem. In very cold weather the water would freeze, preventing water pick-up, unless a heating apparatus was installed.

Track pans normally took a while to fill up after being used, so they could not be used immediately by a close-following train. They were also expensive to maintain, generally requiring a pumping station, a lot of plumbing, and an employee or two to maintain. They were thus only justified on a railroad with a high traffic volume. In the United States, several big eastern railroads used them, primarily the New York Central and Pennsylvania Railroad.

In Britain, they could be found on all main lines, except on the Southern Railway.

Use by diesel locomotives

Diesel locomotives were introduced in the United Kingdom by British Railways in the 1950s, working alongside steam traction until 1968. Passenger vehicles were heated by steam from the locomotive boiler at that time, and the early diesel locomotives were provided with auxiliary boilers to provide the steam. Locomotives intended for long non-stop runs (such as the Class 40 and Class 55) were fitted with water scoops to allow them to replenish the steam generator's water supply from troughs/pans. The withdrawal of steam traction and the introduction of rolling stock with electric rather than steam heating removed the need for such equipment on later types and scoop-equipped locomotives had their scoops removed.

Locations

A map showing the location of GWR troughs in the 1930s is reproduced in the book 'The Great Western Railway'. They are typically at spacings of 40 to 50 miles, but with some wide variations. There are a few instances of trough locations very close to major stopping points; for example Fox's Wood, near St Annes Park, two miles from Bristol Temple Meads; however this was installed when trains to South Wales travelled via Bath and Filton, using these troughs; after the opening of the South Wales direct route via Badminton, numerous passenger and goods trains continued to use the route and required the troughs. The lengths are also given: they vary from 524 to 620 yards (480 to 570 metres).

The locations were (in 1936):

Location	Mileage	In use from	Length (yards)
Pangbourne - Goring	43½	1 October 1895	620
Aldermaston - Midgham	45½	by 1904	620
Fairwood Junction (up)	111½	-	553
Fairwood Junction (down)	111¾	-	495
Cogload Jn - Creech Jn	159¼	March 1902	560
Exminster - Starcross	200	July 1904	560
Keynsham - Fox's Wood	114¾	1 October 1895	620
Chipping Sodbury	104	1 January 1903	524
Undy - Magor	150¼	-	560
Ferryside	240¾	-	620
Denham - Ruislip	2¼	20 November 1905	560
Kings Sutton	81½	-	560
Rowington Jn	114½	by July 1902	440 (560 from 1908)
Charlbury	78	-	560
Bromfield - Ludlow	22½	-	613
Lostwithiel	?	-	?

Similar 1934 maps showed troughs on the main East, Midland and West Coast routes from London to Scotland -

Kings Cross to Edinburgh Waverley

Location	Mileage apart	Length (yards)
Langley - Stevenage	27	694
Peterborough - Werrington Jt	52	638
Muskham	42	704
Scrooby - Bawtry	24	704
Northallerton - Danby Wiske	76	613
Lucker - Berwick	98	613
Edinburgh	73

London Euston to Edinburgh and Glasgow

Location	Mileage apart	Length (yards)
Hatch End - Bushey	15	505
Wolverton - Castlethorpe	38	559
Rugby - Brinklow	32	554
Tamworth - Lichfield	28	642
Whitmore - Madeley	36	563
Preston Brook - Moore	29	579
Brock - Garstang	40	561
Hest Bank - Bolton-le-sands	18	562
Low Gill - Tebay	26	553
Floriston - Gretna	45	560
Thankerton - Carstairs	64	557
Glasgow	32
Edinburgh	31

London St Pancras to Glasgow

Location	Mileage apart	Length (yards)
Oakley - Sharnbrook	55	557
Loughborough - Hathern (via Leicester)	58	557
Melton Mowbray (via Nottingham)	45	557
Dent - Hawes (see also Garsdale railway station	144	554
Floriston - Gretna	45	560
Kirkconnel - New Cumnock	58	564
Glasgow	49

Other British troughs are mentioned in articles on Ipswich and Tivetshall railway stations (Norfolk)

Alternative techniques

LSWR K10 class locomotive with "water cart" tender

Railway companies were well aware of the cost of installing and maintaining this equipment, and the provision of tenders with a large water capacity was an alternative employed in some cases. The London and South Western Railway in England used large 8-wheel tenders nicknamed "water carts".

See also

• Water crane

External links

• [1] Vintage cine of British steam engines in the 1950s using water troughs/track pans