NZASM 46 Tonner 0-6-4T IMR 46 Tonner 0-6-4T CSAR Class B 0-6-4T South African Class B 0-6-4T
NZASM 46 Tonner no. 230Jan Wintervogel at Witbank, Transvaal, April 1993
Type and origin Power type Steam Designer Maschinenfabrik Esslingen Builder 175 by Esslingen 20 byWerkspoor Serial number Esslingen: 2598–2617, 2624–2633, 2656–2665, 2703–2712, 2714–2733, 2745–2789, 2824–2843, 2854–2873, 2877–2886, 2941–2950 Werkspoor: 1–10, 29–38 Model NZASM 46 Tonner Build date 1893–1899 Total produced 195
Specifications Configuration: ​  • Whyte 0-6-4T  • UIC C2'n2t Driver 2nd coupled axle Gauge 3 ft 6 in (1,067 mm)Cape gauge Coupled dia. 51+3⁄16 in (1,300 mm) Trailing dia. 31+7⁄8 in (810 mm) Wheelbase 19 ft8+7⁄32 in (6,000 mm) ​  • Axle spacing (Asymmetrical) 1–2:5 ft2+3⁄16 in (1,580 mm) 2–3:4 ft11+27⁄32 in (1,520 mm)  • Coupled 10 ft2+1⁄32 in (3,100 mm)  • Trailing 5 ft 3 in (1,600 mm) Length: ​  • Over couplers 34 ft 8 in (10,566 mm) Height 12 ft4+1⁄2 in (3,772 mm) Frame type Plate Axle load 10 LT 12 cwt (10,770 kg) ​  • Coupled 10 LT 12 cwt (10,770 kg)  • Trailing 13 LT 19 cwt 1 qtr (14,190 kg) Adhesive weight 31 LT 16 cwt (32,310 kg) Loco weight 45 LT 12 cwt (46,330 kg) Fuel type Coal Fuel capacity 4 LT (4.1 t) Water cap. 1,503 imp gal (6,830 L) Firebox: ​  • Type Round-top  • Grate area 15.6 sq ft (1.45 m2) Boiler: ​  • Pitch 5 ft9+1⁄2 in (1,765 mm)  • Diameter 3 ft10+5⁄8 in (1,184 mm)  • Tube plates 12 ft8+3⁄4 in (3,880 mm)  • Small tubes 144:1+25⁄32 in (45 mm) Boiler pressure 160 psi (1,103 kPa) Heating surface: ​  • Firebox 91.2 sq ft (8.47 m2)  • Tubes 845 sq ft (78.5 m2)  • Total surface 936.2 sq ft (86.98 m2) Cylinders Two Cylinder size 16+15⁄16 in (430 mm) bore 24+13⁄16 in (630 mm) stroke Valve gear Heusinger Valve type Slide Couplers Johnston link-and-pin
Performance figures Tractive effort 16,580 lbf (73.8 kN) @ 75%
Career Operators NZASM Pretoria-Pietersburg Railway CFM Imperial Military Railways Central South African Railways South African Railways Class NZASM 46 Tonner CSAR & SAR Class B Number in class NZASM 177, IMR 195, SAR 28 Numbers NZASM: 61–237 CFM: 20–49 IMR: 61–255 CSAR: 27-202 SAR: 1–2, 4–6, 8, 10–16, 18–22, 24–30, 33–43, 45–48, 50, 52, 54–55 Delivered 1893–1899 First run 1893 Withdrawn 1919

TheSouth African Railways Class B 0-6-4T of 1893 was a steam locomotive from the pre-Union era inTransvaal.

Between 1893 and 1898, 175 Class B0-6-4 tank engines were placed in service by theNederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij in theZuid-Afrikaansche Republiek.^[1]

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 theSecond Boer War. The other eighteen locomotives in this order were intercepted by the Imperial Military Railways, who diverted two of them to Lourenço Marques.^[1][2]

At the end of the war, the survivors of these locomotives were taken onto the roster of theCentral South African Railways, renumbered and designated Class B, while the two in Mozambique were taken onto the roster of theCaminhos 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.^[1][3]

In 1891, theNederlandsche-Zuid-Afrikaansche Spoorweg-Maatschappij (NZASM, often shortened to ZASM) of theZuid-Afrikaansche Republiek (ZAR) placed an order withEmil Kessler's firm, theMaschinenfabrik Esslingen in Germany, for twenty40 Tonner0-6-2 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.^[1][4][5]

To overcome this problem, the next order from the same manufacturer was for0-6-4T locomotives which were practically identical to the40 Tonners 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.^[1][4][5]

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.^[1][5]

In 1899, a further order for another twenty 46 Tonners was placed with theNederlandse 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.^[1]

The remainder were intercepted by the Imperial Military Railways (IMR) who took over the operation of theOranje-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 theCaminhos de Ferro de Mocambique (CFM) in Lourenço Marques.^[1][2][3]

Like their predecessor 40 Tonners, the 46 Tonners hadHeusinger valve gear, outsideplate 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.^[1][4]

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.^[4]

In NZASM service, all the Esslingen-built 46 Tonners were given names as well as engine numbers. The names are listed in Table 1.^[1]

The 46 Tonners became the standard mainline locomotives of the NZASM and were used on all kinds of traffic betweenPretoria in the ZAR andLourenço Marques inMozambique. 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.^[1][4][5]

On 10 October 1895, on ZAR PresidentPaul Kruger's birthday, 46 Tonner no. 104Van Rensburg hauled the NZASM train to the last bolt ceremony atHeidelberg, Transvaal, where the Transvaal and Natal mainlines were linked up.^[6]

One of the locomotives, no. 64Prinsloo, was leased or sold to the Pretoria-Pietersburg Railway (PPR) c. 1897. It retained both the NZASM number and name on the PPR.^[1]

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.^[2][3][7]

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.^[1][5]

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.^[1][5][7][8]

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.^[4]

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. 229Simon Turver which definitely became CFM no. 26.^{[5][8][9][10]}

When theUnion of South Africa was established on 31 May 1910, the three Colonial government railways (Cape Government Railways,Natal Government Railways and CSAR) were united under a single administration to control and administer the railways, ports and harbours of the Union. Although the South African Railways and Harbours came into existence in 1910, the actual classification and renumbering of all the rolling stock of the three constituent railways were only implemented with effect from 1 January 1912.^[6][11]

As a result of locomotive sales by the NZASM to the CFM before the war, wartime attrition and more sales by the CSAR to the CFM after the war, only 55 of the original 175 46 Tonner locomotives remained to be taken onto the SAR roster by 1910. They retained their Class B designation and their planned SAR number range was to be from 1 to 55. From the several gaps in the actual number sequence, it would appear that eleven of these locomotives were withdrawn or disposed of between 1910 and 1912. As a result, by the time the actual renumbering took place in 1912, only 44 of the locomotives remained to be taken onto the SAR roster.^{[1][5][9][11]}

In SAR service, the Class B was used as shunting engines in the Transvaal and the Orange Free State, and towards the end of their service lives also in the Western Cape. The last 46 Tonner was withdrawn from SAR service and scrapped during 1919, but several had earlier been sold to gold mining companies.^[4][5]

Several Class B locomotives were sold to mines and other industries by the CFM, CSAR and SAR when they began to be withdrawn from government railways service. Some remained in industrial service well into the twentieth century. At least one, identified as ex NZASM no. 195Evensen, later CFM no. 27, was purchased by the Randfontein Estates Gold Mine (REGM). Another saw service with Dunn's Locomotive Works in Witbank.^[1][2][3]

Four of the 46 Tonner locomotives are known to have survived.

• Esslingen-built SAR no. 19, NZASM no. 216Beelaerts van Blockland, is at the James Hall Museum atWemmer Pan inJohannesburg, restored as Consolidated Main Reef Mines & Estates no. 4.^[8]
• Esslingen-built SAR no. 41, NZASM no. 197Kracht, is on display at theOuteniqua Transport Museum inGeorge, restored incorrectly as NZASM no. 61Roos and bearing the namePresident Kruger, which was the name carried by 40 Tonner no. 42 in the NZASM days.^[8]
• Esslingen-built SAR no. 44, NZASM no. 230Jan Wintervogel, was donated by ESKOM to the SAR for preservation in 1971 and was steamed occasionally in the Spoornet era for steam enthusiasts' specials, filming and other activities.^[8]
• Werkspoor-built SAR no. 47, unnamed NZASM no. 236, was plinthed on the concourse at Pretoria station, restored incorrectly as NZASM no. 242.^[8]

• 
  Five 46 Tonner locomotives and 32 Tonner no. 991 in the Waterval-Boven roundhouse, c. 1895
• 
  Esslingen-built no. 213, the engineAustralien, at Barberton station in 1901
• 
  Werkspoor-built SAR no. 47, unnamed NZASM no. 236, plinthed at Pretoria station, 8 October 1989
• 
  Rear view of Esslingen-built NZASM 46 Tonner no. 230Jan Wintervogel, in steam at Witbank, April 1993

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