The South African Railways Class 16D 4-6-2 of 1925 was a steam locomotive. In 1925, the South African Railways placed two American-built Class 16D locomotives with a Pacific type wheel arrangement in passenger train service. Five more of these locomotives were ordered and placed in service in 1926.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, May 1946. pp. 373-376.

Manufacturer

On 15 December 1924, after an official tour of investigation to the

United States of America The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territo ...

by G.E. Titren, the Superintendent Motive Power of the South African Railways (SAR), an order was placed with the Baldwin Locomotive Works of

Philadelphia Philadelphia, often called Philly, is the List of municipalities in Pennsylvania#Municipalities, largest city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, the List of United States cities by population, sixth-largest city i ...

for four experimental locomotives, two of which were of a 4-6-2 Pacific type wheel arrangement. These locomotives were all delivered in 1925. The two Pacifics were designated Class 16D and numbered 860 and 861. The two Mountain types, which arrived from the same builders in the same shipment, were designated Class 15C. The Classes 16D and 15C were specially designed for working the ''Union Limited'' (

Johannesburg Johannesburg ( , , ; Zulu and xh, eGoli ), colloquially known as Jozi, Joburg, or "The City of Gold", is the largest city in South Africa, classified as a megacity, and is one of the 100 largest urban areas in the world. According to Dem ...

Cape Town Cape Town ( af, Kaapstad; , xh, iKapa) is one of South Africa's three capital cities, serving as the seat of the Parliament of South Africa. It is the legislative capital of the country, the oldest city in the country, and the second largest ...

) and ''Union Express'' (Cape Town to Johannesburg) passenger trains, the forerunners of the ''Blue Train''.Soul of A Railway, System 7, Western Transvaal, based in Johannesburg, Part 1. Johannesburg between the Home Signals, Part 1. Caption 18.
(Accessed on 20 March 2017)

Characteristics

These locomotives conformed to SAR requirements as far as practicable but also incorporated the latest American railway engineering practices. The engines introduced several features which were new to the SAR at the time, such as top feeds to the boiler, self-cleaning smokeboxes, Sellar's drifting valves, and grease lubrication to the coupled wheel axle boxes, crank pins and connecting rod big ends. Class 16D no

The locomotive's size quickly earned it the nickname ''Big Bertha'', while its contemporary Class 15C locomotive was nicknamed ''Big Bill''. The first two Pacifics were followed by another five locomotives from the same manufacturer in 1926, numbered in the range from 862 to 866. They had thick bar frames, which extended from the front

buffer beam A headstock of a rail vehicle is a transverse structural member located at the extreme end of the vehicle's underframe. The headstock supports the coupling at that end of the vehicle, and may also support buffers, in which case it may also be ...

to the rear

dragbox A dragbox (also ''drag-box'' or ''drag box'') is a substantial, often cast metal, part of a locomotive to which the coupling mechanism is attached to allow the locomotive to pull a train.Ransome-Wallis, Patrick (1959)''The Concise Encyclopedia of ...

. The boilers were equipped with three Coale pop type safety valves and Schmidt type superheaters. Their fireboxes were equipped with flexible side stays and water siphon arch tubes to support the brick arch and to improve circulation. Their Type KT tenders, arranged with self-trimming type coal bunkers, had a coal capacity of and a water capacity of which was considered sufficient for the engines to travel without having to replenish water.

Modifications

Considerable improvements were effected on the Class 16D after they entered service. The first modification was to their cylinders, which were reamed from a bore of . During 1941, all seven engines had their coupled wheels retyred from diameter. To compensate for the loss of tractive effort due to the larger diameter wheels, their operating boiler pressure was increased from by an adjustment of the setting of their safety valves.South African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 Aug 1941). ''Locomotive Diagram Book/Lokomotiefdiagramboek, 3'6" Gauge/Spoorwydte''. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. pp. 23-24, 45-46.South African Railways & Harbours/Suid Afrikaanse Spoorweë en Hawens (15 Aug 1941). ''Locomotive Diagram Book/Lokomotiefdiagramboek, 2'0" & 3'6" Gauge/Spoorwydte, Steam Locomotives/Stoomlokomotiewe''. SAR/SAS Mechanical Department/Werktuigkundige Dept. Drawing Office/Tekenkantoor, Pretoria. pp. 6a-7a, 23-24, 45-46. When larger tyres were fitted, the old tyres were left in position and turned down on the wheel centres to serve as liners and the new tyres were then shrunk on over the liners. The practice of increasing the diameter of coupled wheels, wheel spacing and other considerations permitting, was begun by A.G. Watson during his term in office as Chief Mechanical Engineer and was continued by his successors. The reduction of tractive effort caused by the larger wheels was made up by increasing boiler pressures or by fitting larger cylinders or both, as required. This practice resulted in more mileage between heavy repairs, less cost-per-mile on repairs and locomotives capable of higher speeds. In the Western Cape, wheatland fires caused by locomotives were a huge problem for farmers as well as for the SAR who had to pay out the claims. In the late 1960s Johannes Barnard, the assistant locomotive superintendent at Cape Town, invented a self-cleaning smokebox and a way to blow char out of the smokebox when the engine was standing in non-sensitive places such as at water stops. While on the run, excess char was diverted into a box mounted below the smokebox door. The consensus among railwaymen at the time was that these modifications were not entirely effective, but they remained in use for at least ten years nonetheless.Soul of A Railway, System 1, Part 2: Cape Town to Wellington. Caption 37.
(Accessed on 26 November 2016)Soul of A Railway, System 1, Part 7: The Caledon train. Captions 4, 61.
(Accessed on 29 November 2016)Soul of A Railway, System 1, Part 9: Caledon line freight, Part 2. Elgin-Caledon and beyond. Caption 25.
(Accessed on 24 March 2017)Soul of A Railway, System 1, Part 11: Cape Town-Kraaifontein-Malmesbury-Bitterfontein by C P Lewis. Captions 5, 7, 9.
(Accessed on 2 December 2016)

Service

The introduction of these large engines, along with their Class 15C Mountain type ''Big Bill'' siblings, resulted in a complete revision of traffic operation between

and

. The Pacifics were scheduled to work the stretch between Johannesburg and

Beaufort West Beaufort West (Afrikaans: ''Beaufort-Wes''; Xhosa: ''eBhofolo'') is a town in the Western Cape province in South Africa. It is the largest town in the arid Great Karoo region, and is known as the "Capital of the Karoo". It forms part of the Beau ...

while the ''Big Bill'' Mountains entered service on the stretch from Beaufort West to Cape Town with its ruling gradient of 1 in 40 (2½%) and severe curvature for approximately on the Hex River Railpass section between Touws River and

De Doorns De Doorns is situated in the Breede Valley Local Municipality, Cape Winelands District Municipality in the Western Cape province of South Africa. Location It lies in the Hex River Valley on the N1 National Route, 32 km north-east of Worce ...

. On Thursday 13 August 1925, ''Big Bertha'' no. 860 made locomotive history by hauling the ''Union Limited'', later to become the ''Blue Train'', over a distance of from Johannesburg to Cape Town in 29 hours. On the return journey, no. 860 took the ''Union Express'' over from ''Big Bill'' no. 2060 at Beaufort West and hauled it all the way back to Johannesburg. This continuous run by one locomotive set up a world record. Prior to this, it was customary to use three engines on the Cape Town run of these two named trains with engine changes at Kimberley and Beaufort West. On ordinary trains, up to six locomotives were often used with engine changes at

Klerksdorp Klerksdorp () is located in the North West Province, South Africa. Klerksdorp, the largest city in the North West Province, is located southeast of Mahikeng, the provincial capital. Klerksdorp was also the first capital of the then Transvaal Repu ...

, Kimberley,

De Aar De Aar is a town in the Northern Cape province of South Africa. It has a population of around 42,000 inhabitants. It is the second-most important railway junction in the country, situated on the line between Cape Town and Kimberley. The juncti ...

, Beaufort West and Touws River. Upon the arrival of larger locomotives, the Class 16D was later transferred to

Bloemfontein Bloemfontein, ( ; , "fountain of flowers") also known as Bloem, is one of South Africa's three capital cities and the capital of the Free State province. It serves as the country's judicial capital, along with legislative capital Cape To ...

in the

Orange Free State The Orange Free State ( nl, Oranje Vrijstaat; af, Oranje-Vrystaat;) was an independent Boer sovereign republic under British suzerainty in Southern Africa during the second half of the 19th century, which ceased to exist after it was defeat ...

, from where they worked north to Johannesburg. In 1939 they were relocated to Cape Town from where they hauled fast local commuter trains to

Wellington Wellington ( mi, Te Whanganui-a-Tara or ) is the capital city of New Zealand. It is located at the south-western tip of the North Island, between Cook Strait and the Remutaka Range. Wellington is the second-largest city in New Zealand by metr ...

and

Malmesbury Malmesbury () is a town and civil parish in north Wiltshire, England, which lies approximately west of Swindon, northeast of Bristol, and north of Chippenham. The older part of the town is on a hilltop which is almost surrounded by the upp ...

for the remainder of their careers. The

Klawer Klawer is a town in the Matzikama Municipality in the Western Cape province of South Africa. It is situated on the right bank of the Olifants River, south-east of Vredendal and north of Cape Town. According to the 2011 census it has a populat ...

Mail passenger train from Cape Town was one of the last reasonably respectable duties for the Baldwin Pacifics. By 1971, the days of the Class 16D in passenger service were numbered and service on goods trains and pick-up workings predominated. They were withdrawn from service in 1972.Soul of A Railway, System 7, Western Transvaal, based in Johannesburg, Part 26: Braamfontein West to Klerksdorp (home signal) by Les Pivnic, Part 1. Caption 15.
(Accessed on 6 May 2017)

Preservation

Illustration

File:Class 16D 4-6-2 no. 860.jpg, ''Big Bertha'' no. 860, as delivered with Johnston link-and-pin couplers, c. 1925 File:SAR Class 16D 860 (4-6-2) (Big Bertha).jpg, No. 860 on the Magaliesburg line, c. 1992 File:SAR Class 16D 860 (4-6-2).JPG, No. 860 at Monument station, May 2002

References

{{Steam locomotive tenders 1920 4-6-2 locomotives 2′C1′ h4 locomotives Baldwin locomotives Cape gauge railway locomotives Railway locomotives introduced in 1925 1925 in South Africa