Science Fair Project Encyclopedia
Steam locomotives often haul a tender, which is a special railroad car designed to hold the locomotive's fuel (wood or coal) and water. Steam locomotives consume large quantities of both. Locomotives that do not have tenders and carry all their fuel and water on board the locomotive itself are called tank locomotives. Examples are the toy train Thomas the Tank Engine or 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, locomotives that cannot easily be turned at the end of their runs, or that need the maximum adhesion possible, tend to use tank locomotives.
In Germany, special attention was given to ensuring that tender locomotives be 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 was 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.
- Tender, for other uses of the word
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