|
The Rhodesia Railways 15th class (later Zambian Railways and National Railways of Zimbabwe 15th classes), was the second-largest class of Garratt locomotives, with 74 locomotives built. Only the Class GMA/GMAM of the South African Railways was more numerous at 120 locomotives. ==Development and delivery== The 4-6-4+4-6-4 wheel arrangement is sometimes called a "Double Baltic" or "Double Hudson" Garratt. The Rhodesia Railways (RR) 15th class was one of only two Double Baltic Garratt classes built, the other class of "Double Baltics" being the Sudan Railways 250 class (which RR later bought and classified as their 17th class). The 15th class were largely based on the RR 16th class 2-8-2+2-8-2 Garratts. A requirement for a locomotive with a larger driving wheel diameter for higher speed train service on the more level parts of the railway led to the design of a new class. Initially a "Double Pacific" (4-6-2+2-6-4) was considered, but after examining the Sudan Railways 250 class (which were built in 1937), the RR settled on a design with the same wheel arrangement and same driver diameter () as the Sudanese Double Baltics. Initially four locomotives were ordered, and they were numbered 271–274. These Garratts were built with a "semi-streamlined" rounded front bunker (water tank), that would become synonymous with modern Garratt locomotives. The locomotives proved their worth, with a high availability, achieving per month. After World War II, a further 70 locomotives were ordered. The 1947 batch of ten were delivered with a modified front bunker, and a rounded rear bunker as well (the first four had a standard rectangular rear bunker). The next twenty locomotives had further modifications to the front bunker, while the rear bunker had been modified to increase coal capacity from . The last forty locomotives were designated as 15A class. While almost identical externally, they had their boiler pressure increased from . With the introduction of the 17th class (numbered 271–280) and the 18th class (numbered 281–289), the early members of the class were renumbered to put all of the 15th class into a solid block. Over the following years there were some swapping of boilers between locomotives of 15th, 15A and 16th classes, as well as exchanges of front bunkers, so it was impossible to say for certain if a particular locomotive is 15th or 15A class (i.e. has a 180 or 200 psi boiler). 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rhodesia Railways 15th class」の詳細全文を読む スポンサード リンク
|