The South African Railways Class B 0-6-4T of 1893 was a steam locomotive from the pre-Union era in Transvaal.
Between 1893 and 1898, 175 Class B tank engines were placed in service by the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij in the Zuid-Afrikaansche Republiek.
In 1899, twenty more were ordered, of which only two were delivered by the time the Imperial Military Railways took over all railway operations in the two Boer Republics during the Second Boer War. The other eighteen locomotives in this order were intercepted by the Imperial Military Railways, who diverted two of them to Lourenço Marques.
At the end of the war, the survivors of these locomotives were taken onto the roster of the Central South African Railways, renumbered and designated Class B, while the two in Mozambique were taken onto the roster of the Caminhos de Ferro de Mocambique. In 1912, when the remaining locomotives were assimilated into the South African Railways, they were renumbered again, but retained their Class B designation.
Forerunners In 1891, the Nederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij (NZASM, often shortened to ZASM) of the Zuid-Afrikaansche Republiek (ZAR) placed an order with Emil Kessler's firm, the Maschinenfabrik Esslingen in Germany, for twenty 40 Tonner tank steam locomotives. While these locomotives were satisfactory in service, the trailing wheels initially proved troublesome owing to insufficient sideways freedom of movement when traversing sharp curves.Espitalier, T.J.; Day, W.A.J. (1944). The Locomotive in South Africa – A Brief History of Railway Development. Chapter IV – The N.Z.A.S.M. (Continued). South African Railways and Harbours Magazine, November 1944. pp. 844–845, 848.
Manufacturers To overcome this problem, the next order from the same manufacturer was for locomotives which were practically identical to the in their main dimensions, but with a four-wheeled trailing bogie. Because of the resultant increase in weight, these locomotives became known as the 46 Tonners.
The first twenty of these engines were delivered between 1893 and 1894 and numbered in the range from 61 to 80. They were followed by another 155 locomotives from the same manufacturer between 1894 and 1898, delivered in nine more batches and numbered in the range from 81 to 235.
In 1899, a further order for another twenty 46 Tonners was placed with the Nederlandse Fabriek van Werktuigen en Spoorwegmaterieel (Werkspoor) in the Netherlands. They were to have been numbered in the range from 236 to 255, following on the last of the Esslingen locomotives, but since delivery only commenced just before the outbreak of the Second Boer War, only numbers 236 and 237 actually entered service on the NZASM.
The remainder were intercepted by the Imperial Military Railways (IMR) who took over the operation of the Oranje-Vrijstaat Gouwerment-Spoorwegen (OVGS) and the NZASM on behalf of the invading British forces as possession was obtained of their railway lines. Sixteen of these engines were landed and erected at East London. The IMR diverted the other two to the Caminhos de Ferro de Mocambique (CFM) in Lourenço Marques.
Characteristics Like their predecessor 40 Tonners, the 46 Tonners had Heusinger valve gear, outside plate frames and used saturated steam. The original design of the 46 Tonner called for a straight-backed coal bunker, but the last sixteen Esslingen-built and the twenty Werkspoor-built locomotives had bunkers that sloped outwards towards the top at the back, which increased the coal capacity by 20%. Their water tanks were also enlarged to a 10% larger capacity.
In service, difficulty was experienced with the trailing bogie wheels fouling the firebox and the heads of stays and rivets. This was partially overcome by fitting stops to the engine frame, but this restriction of the sideways movement of the bogie wheels resulted in derailments in tight curves such as on diverging points. The engines performed well at relatively low speeds, but were prone to serious lateral oscillations at higher speeds. Cases of derailment on straight track at speed demonstrated the limitations of a design where there was no leading carrying wheel to stabilise the engine and considerable overhang of the cylinders.
Service NZASM In NZASM service, all the Esslingen-built 46 Tonners were given names as well as engine numbers. The names are listed in Table 1.
The 46 Tonners became the standard mainline locomotives of the NZASM and were used on all kinds of traffic between Pretoria in the ZAR and Lourenço Marques in Mozambique. Since they did not have a leading bogie, they were found to be rough-riding and it became the practice to run them bunker forward whenever possible. The trailing bogie had a steadying effect on the locomotive when leading and the crew was not shaken up as much.
On 10 October 1895, on ZAR President Paul Kruger's birthday, 46 Tonner no. 104 Van Rensburg hauled the NZASM train to the last bolt ceremony at Heidelberg, Transvaal, where the Transvaal and Natal mainlines were linked up.The South African Railways – Historical Survey. Editor George Hart, Publisher Bill Hart, Sponsored by Dorbyl Ltd., Published c. 1978, pp. 17, 21, 25.
Pretoria-Pietersburg Railway One of the locomotives, no. 64 Prinsloo, was leased or sold to the Pretoria-Pietersburg Railway (PPR) c. 1897. It retained both the NZASM number and name on the PPR.
Caminhos de Ferro de Moçambique Between 1897 and 1898, some of the NZASM 46 Tonner locomotives were sold to the CFM. The CFM eventually had at least thirty 46 Tonners in service. The two locomotives which were delivered after the outbreak of the war and which were diverted to Lourenço Marques upon arrival, IMR numbers 249 and 250, were also taken onto the CFM roster at the end of the war. Between 1907 and 1920, during the Central South African Railways (CSAR) and South African Railways (SAR) eras, six more 46 Tonners were sold to the CFM.CFM locomotive list, compiled by Reimar Holzinger
Imperial Military Railways All the NZASM 46 Tonners, as well as sixteen of the eighteen locomotives which were not delivered to the NZASM as a result of the outbreak of the war, were taken onto the roster of the IMR when it took over all railway operations in the ZAR during the war. It would appear that the locomotives were not renumbered in IMR service.
Central South African Railways Hostilities ceased on 1 June 1902. On 1 July 1902, when the IMR was transferred to civilian control, the survivors of the NZASM 46 Tonners were taken onto the CSAR roster. They were designated Class B and renumbered by the CSAR, but records of the renumbering details are scant. The available information on NZASM-to-CSAR renumbering only covers those locomotives which the CSAR had sold to the CFM between 1907 and 1910, as shown in Table 1 and included in Table 2.
Several alterations were made to the locomotives by the IMR and CSAR. The original crank webs had solid crank-pin collars. New crank webs were fitted, which enabled solid bushed connecting and coupling rods to be fitted in place of the original split brass type. The original unbalanced slide valves were replaced with balanced slide valves.
The builders, works numbers, names, original engine numbers and known renumbering onto the rosters of the CFM, CSAR and SAR are listed in the table. The known CFM engine numbers are in the range from 20 to 49, but since the CFM locomotives were probably allocated CFM numbers in the order in which they were acquired, most of the actual CFM engine numbers are not known with the exception of NZASM no. 229 Simon Turver which definitely became CFM no. 26.Central South African Railways (1907). CSAR Rolling Stock Register. Roster of CSAR Class B numbers 27 to 198 as from November 1907.