Track pan

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 consist of a long trough filled with water, lying along a stretch of railroad/railway track between the rails.

Overview

Steam locomotives use considerable amounts of water, converted to steam and exhausted to the atmosphere when under power. While condensing equipment has been used in railway locomotives, it is only practical for low power applications, particularly in urban tunnels where the steam discharge would be objectionable. Consequently there is no recycling of water in typical steam locomotives, and the water supply carried in locomotive or tender tanks must be continually replenished.

This creates difficulties for heavy trains running over long distances without stopping for commercial purposes, and in the case of time-sensitive transits delays purely for the purpose of water replenishment at water stops are objectionable. Very large tenders were designed, but there are practical limits to tender size, and the dead weight haulage is unattractive.

John Ramsbottom, a Victorian locomotive engineer, devised the water trough/track pan. This is a very long (several hundred yards) shallow trough laid in between the rails at a suitable point on the line where tender replenishment is required and the trough can easily be refilled from a nearby water source. Obviously the entire length of the installation must be on level track, and suitable intervals between these locations and commercial stopping points are essential.

The first installation was about October of 1860 by the London and North Western Railway at Mochdre, Conwy on its North Wales Coast (or Chester and Holyhead) line. [cite book|author=Robbins, Michael|title=Points and Signals|date=1967|publisher=George Allen & Unwin|location=London]

Naturally-soft water sources were preferred as they caused less scaling in the locomotive's boiler. One example was at Oakley in Bedfordshire, where the troughs are long gone, but the sides of the cutting are still faced with brick to resist the overspray from a train taking on water.

Locomotive equipment

A "scoop" is fitted to the underside of the locomotive's tender (or in some unusual cases tank locomotives carried scoops, obviously under the locomotive) in such a way as it can be raised or lowered, normally remotely (often by a screw mechanism or compressed air). The scoop feeds into a vertical pipe that has an outlet at the top of the tender's water tank. When the scoop is lowered at speed into a water-filled track pan, water is forced up the pipe and into the water tank. This required good timing on the part of the fireman, who had to lower the scoop just after entry into the trough, and raise it before the end. A simple indication was provided on the operating mechanism to show if the tender was full. A lineside indicator was provided in Great Britain to show the start point of the troughs — it was a large white rectangular board with a black zigzag marking. On American railroads, illuminated trackside signals were employed for nighttime usage, to indicate the start and approaching end of the track pan.

The feed and venting arrangements on the tender needed to be carefully designed to accept a massive volume of water discharge into the tender at a high flow rate. Filling up from a track pan resulted in considerable water spray as the train progressed. It would certainly be advised not to have a window open in the first few cars after the locomotive—fortunately in the US, those cars were normally for baggage or mail. 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. It was often necessary that the train slow down during pick-up to prevent the inflow of water from causing structural damage to the tender. However, the New York Central used a very robust tender design that water pick-up to proceed without slowing the train.

It was easy to distinguish an American locomotive owned by a road that favored the track pan—the tender would have a huge coal capacity but a relatively tiny water tank. This was especially notable on the New York Central's later locomotives. On British locomotives, a large dome is often visible towards the back of the tender - this is the "deflector" which sits over the top of the scoop pipe, and bounces water back down into the tank.

Lineside equipment

The track was usually boarded out over the affected length, and this fact and the excessive water spray made track maintenance excessively difficult. In very cold weather the water would freeze, preventing water pick-up, unless a heating apparatus was installed. To assure satisfactory ingestion of water and to minimize water spray and sloshing, locomotive speed was normally reduced to about 40 miles per hour (65 km/h) during the water intake procedure.

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. [cite journal|author=Foster, Richard|title=L&NWR water troughs|journal=British Railway Journal|issue=London & Birmingham Railway edition|date=1989|pages=84–91] [cite book|author=Twells, H. N.|title=LMS Miscellany: a pictorial record|date=1982|publisher=Oxford Publishing Co|location=Oxford|isbn=0-86093-172-2] [cite journal|author=Vaughan, Adrian|title=Water troughs on the GWR|journal=Railway World|volume=51|date=1990|pages=278–80,370–4] [cite journal|title=Water pick-up troughs|journal=Railway Magazine|volume=74|date=1934|pages=4–7] [cite journal|author=Webb, David|title=Water troughs|journal=Cumbrian Railways Circular|volume=3|date=1984-8|pages=223,263–4]

Locations

A map showing the location of GWR troughs in the 1930's is reproduced in [The Great Western Railway - 150 Glorious Years, Whitehouse P and Thomas St John (editors), David & Charles, Newton Abbot, ISBN 0 7153 8763 4] . They are typically at spacings of 40 to 50 miles, but with some wide variations, and a few instances of trough locations very close to major stopping points (e.g. St Annes Park, two miles from Bristol Temple Meads.) The lengths are also given: they vary from 524 to 620 yards.

See also

* Water crane

References