Tender locomotive
From Wikipedia, the free encyclopedia
Steam locomotives often haul a tender, which is a special railway truck designed to hold the locomotive's fuel (wood, coal, or oil) and water. In America, tenders are sometimes called coal-cars. Steam locomotives consume large quantities of both fuel and water. Locomotives that do not have tenders and carry all their fuel and water on board the locomotive itself are called tank engines. Examples are the fictional locomotive Thomas the Tank Engine and the German BR 89.
One reason not to carry the fuel and water aboard the locomotive is that the rate of consumption of both is such that it is hard to carry enough for an extended range. Another is the desire to keep the locomotive's weight near constant, so that its hauling abilities remain consistent (since they are dependent on weight on driven wheels multiplied by a coefficient of friction).
The disadvantages of a tender are that it reduces the locomotive's weight and hence its adhesion and that it has difficulties running in reverse at speed, especially in tight curves. For these reasons, when locomotives cannot easily be turned at the end of their runs, or if the maximum adhesion possible is needed, tank locomotives are preferred.
In Germany, special attention was given to ensuring that tender locomotives were capable of moderately high speeds in reverse, pushing their tenders. The numerous BR 50 (2-10-0) locomotives, for example, were capable of 80 km/h (50 mph) in either direction, and were commonly used on branch lines with no turning facilities.
A source of possible confusion with regards to German locomotives is that in German, Tenderlokomotive means a tank locomotive. A locomotive with a separate, hauled tender is a Schlepptenderlokomotive.
The fuel and water capacities of a tender are usually proportional to the rate at which they are consumed, though there were exceptions. The Pennsylvania Railroad and the New York Central Railroad used track pans on many of their routes, allowing locomotives to pick up water at speed. The result was that the water tanks on these tenders were proportionally much smaller.
An additional tender which holds only water is called a "canteen." During the steam era, these were not frequently used. Water tanks were placed at regular intervals along the track, making a canteen unnecessary in most cases. However, there were times that canteens proved economical. The Norfolk & Western used canteens with its giant 2-8-8-2 locomotives on coal trains. Use of the canteen allowed one of the water stops to be skipped, meaning that the train did not have to climb a hill from a dead stop. Currently, Union Pacific uses canteens with its steam locomotives 844 and 3985 on excursion trains. Virtually all the trackside tanks were removed when steam locomotives were retired. Nowadays, fire hydrant hookups are used, which fills the tanks far more slowly. The canteens allow for greater range between stops.
The only example of a canteen in the United Kingdom was on Flying Scotsman during the late 1960s and early 1970s. As railways in Britain tend to be far shorter than those in the USA, the canteen was never seen as an economical proposition.
[edit] Other tenders
Sometimes a tender will be used for a diesel locomotive. This is typically a tank car with a fuel line that connects to the locomotive and MU connections to allow locomotives behind the tender to be controlled remotely. The Burlington Northern used fuel tenders in remote territory where fuel was expensive. Diesel fuel could be bought cheaply and loaded into the tender. A common consist was two EMD SD40-2s with a tender between them. Some of the tenders survived the Burlington Northern Santa Fe merger but retain the black and green BN colors. The Southern Pacific also briefly experimented with fuel tenders for diesels. Some slugs have fuel tanks and serve as fuel tenders for the attached locomotives.
Union Pacific used giant fuel tenders on its massive turbines. These tenders were originally used with steam locomotives, then reworked to hold heavy "Bunker C" fuel oil. Fuel capacity was about 23,000 gallons (87,000 liters). When the turbines were retired, some of the tenders were kept and reworked to hold water and used as canteens for steam locomotives.
On British Railways, brake tenders were used with early main line diesel locomotives. These were coupled in front of the locomotive to provide extra braking power.
Certain early British steam locomotives were fitted with powered tenders. As well as holding coal and water, these had wheels powered from the locomotive to provide greater strength and adhesion. However, these were abandoned for economic reasons - railwaymen working on locomotives so equipped demanded extra pay as they were effectively working on two locomotives. However, the concept was tried again on the Ravenglass and Eskdale Railway's River Mite, and the Garratt locomotive may be seen as an extension of this principle.
[edit] See also
- Tender, for other uses of the word
