Under the Whyte notation for the classification of steam locomotives by wheel arrangement, a is a Garratt articulated locomotive consisting of a pair of engine units back to back, with the boiler and cab suspended between them. The wheel arrangement has four leading wheels on two axles, usually in a leading bogie, eight powered and coupled driving wheels on four axles and two trailing wheels on one axle, usually in a trailing truck. Since the type is generally known as a Mountain, the corresponding Garratt type is usually known as a Double Mountain.
Overview A Garratt locomotive is actually two separate engines combined in a double articulated format, thereby providing multiple powered axles over which the total locomotive weight is spread. This results in a more powerful locomotive since, compared to a tender locomotive of similar total mass with tender included, a much larger percentage of the locomotive's total mass contributes to traction.Beyer, Peacock Garratt Locomotives
The Double Mountain was probably the optimal Garratt wheel arrangement, with the four-wheeled leading bogies and the two-wheeled trailing trucks on each engine unit ensuring stability at speed and with sixteen coupled wheels for traction. More coupled wheels would inhibit the locomotive on tight curves, while the only advantage of more non-coupled wheels would be to reduce the axle loading.
The largest steam locomotive built in Europe was a Garratt, built by Beyer, Peacock and Company for the Soviet Railways in 1932. The most numerous Garratt class in the world was also a Double Mountain, the Class GMA and GMAM of the South African Railways, of which 120 were built between 1954 and 1958.
Per definition, most Garratt locomotives are tank engines since they carry all their water and fuel in on-board water tanks and coal bunkers instead of in a separate tender. The three known exceptions were all tank-and-tender engines and were all Garratts.Espitalier, T.J.; Day, W.A.J. (1946). The Locomotive in South Africa - A Brief History of Railway Development. Chapter VII - South African Railways (Continued). South African Railways and Harbours Magazine, November 1946. pp. 894-896.
+4-8-2+2-8-4 Garratt production list – All manufacturers Gauge Railway Class Works no. Units Year BuilderSierra Leone Government Railway7707-7720141955-56Beyer, Peacock & CompanyKenya Uganda RailwayEC6300-630341926Beyer, Peacock & CompanyKenya Uganda RailwayEC16429-6440121928Beyer, Peacock & CompanyKenya Uganda RailwayEC16516-652381928Beyer, Peacock & CompanyAntofagasta (Chili) & Bolivia Railway6524-652631929Beyer, Peacock & CompanyCordoba Central Railway, ArgentinaE116550-6559101929Beyer, Peacock & CompanyKenya Uganda RailwayEC16637-663821930Beyer, Peacock & CompanyTanganyika RailwayGA6718-672031931Beyer, Peacock & CompanyWar Dept., Kenya Uganda RailwayHeavy7075-708171943Beyer, Peacock & CompanyWar Dept., BurmaLight7140-7159201945Beyer, Peacock & CompanyKenya Uganda RailwayEC67280-728561949Beyer, Peacock & CompanyBurma RailwaysGE7286-728941949Beyer, Peacock & CompanyAngola: Luanda Railway (CFL)5007308-731361949Beyer, Peacock & CompanyAntofagasta (Chili) & Bolivia Railway7420-742561950Beyer, Peacock & CompanyEast African Railways607577-758041954Beyer, Peacock & CompanyEast African Railways597632-7658271955Beyer, Peacock & CompanyEast African Railways607659-766681954Beyer, Peacock & CompanyEast African Railways597700-770671955Beyer, Peacock & CompanyEast African Railways607721-772551954Beyer, Peacock & CompanyCF d'Afrique Occidentale Française932715-2724101938Franco-Belge, FranceCF d'Afrique Occidentale Française932731-2740101939Franco-Belge, FranceCF d'Afrique Occidentale Française932748-275471941Franco-Belge, FranceEast African Railways602983-2994121954Franco-Belge, FranceRede Ferrovaria do Noroeste, Brazil25257-2526261952Henschel & SonKenya Uganda RailwayEC24070-24079101931North British Locomotive CompanyPLM, Algeria241-142.YAT2673-267641931Franco-Belge, FranceQueensland RailwaysASGCLTB 21-2551944Clyde EngineeringTasmanian Government RailwaysASGCLTB 37-3821945Clyde EngineeringQueensland RailwaysASGCLTB 51-5331944Clyde EngineeringWestern Australian Government RailwaysASGCLTB 54-5961945Clyde EngineeringTasmanian Government RailwaysASGCLTB 60-6231945Clyde EngineeringWestern Australian Government RailwaysASGCLTB 63-6531945Clyde EngineeringQueensland RailwaysASGCLTB 11-1991943-44Islington Railway WorkshopsWestern Australian Government RailwaysASGCLTB 2011943-44Islington Railway WorkshopsWestern Australian Government RailwaysASGCLTB 44-4521944 caIslington Railway WorkshopsWestern Australian Government RailwaysASGCLTB 26-3051943-44Midland Railway WorkshopsWestern Australian Government RailwaysASGCLTB 46-5051944 caMidland Railway WorkshopsQueensland RailwaysASGCLTB 1-551943-44Newport WorkshopsWestern Australian Government RailwaysASGCLTB 1011944Newport WorkshopsWestern Australian Government RailwaysASGCLTB 31-3221945Newport WorkshopsAustralian Portland CementASGCLTB 3311945Newport WorkshopsTasmanian Government RailwaysASGCLTB 6-831944Newport WorkshopsQueensland RailwaysASGCLTB 911944Newport WorkshopsAngola: Benguela Railway (CFB)10A6333-633861927Beyer, Peacock & CompanySouth African RailwaysGL6530-653121930Beyer, Peacock & CompanyEmu Bay Railway6580-658231929Beyer, Peacock & CompanyAngola: Benguela Railway (CFB)10B6602-6615141930Beyer, Peacock & CompanyNigerian Railways6635-663621930Beyer, Peacock & CompanySouth African RailwaysGL6639-664461930Beyer, Peacock & CompanySouth African RailwaysGM6883-6898161938Beyer, Peacock & CompanySouth African RailwaysGEA7168-7217501945-47Beyer, Peacock & CompanyQueensland RailwaysBG7341-7350101951Beyer, Peacock & CompanyAngola: Benguela Railway (CFB)10C7366-7375101951Beyer, Peacock & CompanyAngola: Benguela Railway (CFB)10C7376-737721952Beyer, Peacock & CompanySouth African RailwaysGMA7550-755231956Beyer, Peacock & CompanyAngola: Benguela Railway (CFB)10C7593-759861952Beyer, Peacock & CompanyAngola: Benguela Railway (CFB)10D7667-7676101955-56Beyer, Peacock & CompanySouth African RailwaysGMA7677-768151956Beyer, Peacock & CompanyRhodesia Railways207685-7699151954-55Beyer, Peacock & CompanySouth African RailwaysGMA7750-7764151956Beyer, Peacock & CompanyRhodesia Railways207780-778561957Beyer, Peacock & CompanyRhodesia Railways20A7786-7825401957-58Beyer, Peacock & CompanySouth African RailwaysGMA7836-7845101958Beyer, Peacock & CompanyC.F.Moçambique9512059-2070121952Du Haine Saint-PierreC.F. du Bas Congo a Katanga9002097-2108121953Du Haine Saint-PierreQueensland RailwaysBG2905-2924201951Franco-Belge, FranceSouth Australian Railways4002973-2982101953Franco-Belge, FranceAngola: Moçamedes Railway (CFM)10027000-2700561953Henschel & SonC.F.Moçambique97128642-2864651956Henschel & SonSouth African RailwaysGMA28680-28704251952Henschel & SonSouth African RailwaysGO28705-28729251954Henschel & SonSouth African RailwaysGMA29600-29629301954Henschel & SonAngola: Luanda Railway (CFL)5502493-249861954KruppSouth African RailwaysGMA27691-27702121956North British Locomotive CompanySouth African RailwaysGMA27769-27778101958North British Locomotive CompanySouth African RailwaysGMA27783-27792101958North British Locomotive CompanyIranian State Railway866787-679041936Beyer, Peacock & CompanySoviet Railways? [Ya]673711932Beyer, Peacock & CompanyBuenos Aires & Pacific Railway, Argentina951671511931Beyer, Peacock & CompanyBuenos Aires Great Southern, Argentina146417-6428121928Beyer, Peacock & CompanyBuenos Aires & Pacific Railway, Argentina9516532-653431930Beyer, Peacock & CompanyBengal Nagpur Railway, IndiaP6931-693441939Beyer, Peacock & Company
Usage Angola
All three main railway systems in Angola used Garratt locomotives.
The Caminho de Ferro de Benguela (CFB) was the largest user, with 48 locomotives built by Beyer, Peacock & Company between 1927 and 1956. Six Class 10A locomotives were delivered in 1927, followed by fourteen Class 10B locomotives in 1930. In 1951 and 1952, eighteen Class 10C locomotives followed, and ten Class 10D locomotives were delivered in 1955 and 1956.
Six Class 500 locomotives were built for the Caminhos de Ferro de Luanda (CFL) by Beyer, Peacock & Company in 1949. Six Class 550 locomotives, built for gauge, were delivered to the same system by Friedrich Krupp in 1954.
The third system, the Caminhos de Ferro de Moçâmedes (CFM), bought six Class 100 locomotives from Henschel & Son in 1953.
Australia Four classes of Garratt locomotives entered service in Australia between 1929 and 1953, all on gauge.
Beyer, Peacock & Company built three locomotives for the Emu Bay Railway in Tasmania in 1929.
The Australian Standard Garratt was developed in Australia during the Second World War, when the Commonwealth Land Transport Board (CLTB) commissioned Chief Mechanical Engineer Frederick Mills of the Western Australian Government Railways (WAGR) to design the locomotive as an emergency measure. Out of an intended 65 locomotives, 57 were built by the Midland Railway Workshops, Newport Workshops, Islington Workshops and Clyde Engineering between 1943 and 1945. The initial allocation was 23 locomotives to the Queensland Railways (QR), eight locomotives to the Tasmanian Government Railways, 25 locomotives to the WAGR and one to the Fyansford Cement Works Railway of Australian Portland Cement. Some of the locomotives later migrated from the QR and WAGR, where they were unpopular with crews, to other systems such as the South Australian Railways and the Emu Bay Railway.Gunzberg, A: A History of WAGR Steam Locomotives. ARHS WA 1984Oberg, Leon. (1975). Locomotives of Australia. Sydney, New South Wales: Reed.
Thirty BG class locomotives were built for the Queensland Railways in 1951, ten by Beyer, Peacock & Company and twenty by Société Franco-Belge.
Franco-Belge also built ten 400 Class locomotives for the South Australian Railways in 1953.
India In 1939, the Bengal Nagpur Railway introduced the Class P, weighing in at 230 tons and having a 17-ton axle load. Indian Railways had proposals for a 4-8-2+2-8-4 design known as the Class WHG, which ultimately never came to fruition due to the move towards dieselisation and electrification.
Kenya, Tanganyika and Uganda
The East African Railways (EAR), formed in 1948 by merging the Kenya and Uganda Railways with the Tanganyika Railways to operate railways in Kenya, Tanganyika and Uganda, operated the largest and most powerful steam locomotive on . This was the oil-fired EAR 59 class Garratt, of which 34 were built in two batches by Beyer, Peacock & Company in 1955. The 59 class had the reputation of being amongst the largest and most powerful steam locomotives in the world, with a diameter boiler and a tractive effort of . Although Garratt locomotives operated in all three territories, the 59 Class only worked in Kenya and latterly solely on the line between Nairobi and Mombasa. The last one was withdrawn from regular service in 1980.
South Africa Five classes of Double Mountain locomotives, three of which were tank-and-tender Garratts, were acquired by the South African Railways (SAR) between 1929 and 1954.