South African Class 16DA 4-6-2 1930

The South African Railways Class 16DA 4-6-2 of 1930 was a steam locomotive.
In 1930, the South African Railways placed six redesigned Class 16DA steam locomotives with a 4-6-2 Pacific type wheel arrangement in passenger train service.
==Manufacturer==
An order for six locomotives for the South African Railways (SAR), similar to the Class 16DA Pacific type locomotives of 1928 and 1929 but built to an improved design, was placed with Henschel and Son of Kassel in Germany in 1930.
==Characteristics==
In an attempt to improve the steaming properties of further orders of Class 16DA locomotives, A.G. Watson, who had succeeded Colonel Collins as CME in 1929, designed a boiler of the Wootten type. It had a very wide firebox with a grate area of 60 square feet (5.574 square meters). Watson was a firm believer in large firegrates with enlarged blast pipe caps to give a reasonably low burning rate of fuel per unit of grate area, which improved boiler efficiency and reduced the emission of sparks and partially burnt fuel.
The boiler itself was of the same dimensions as that of the earlier locomotives in terms of girth and length between tube plates, the only difference being in the tube arrangement. The enlarged firebox, however, had a firegrate area which was 33⅓% larger than the 45 square feet (4.181 square metres) of the earlier Hohenzollern- and Baldwin-built locomotives. It was of comparable proportions to those which would later be installed on the Class 15E and Class 23.
This boiler and firebox was installed on these final six Class 16DA locomotives, numbered in the range from 874 to 879, which were built by Henschel and delivered in 1930. Compared to the earlier Hohenzollern- and Baldwin-built locomotives, the steaming ability of the six Henschel-built locomotives was phenomenal and led to the adoption of wide fireboxes without combustion chambers as the standard on all subsequent SAR mainline steam locomotives.
The Henschel-built Class 16DA locomotives with their much wider fireboxes, their correspondingly larger grate areas and slightly larger diameter trailing wheels were sufficiently different from the Baldwin- and Hohenzollern-builts to justify a separate classification such as Class 16DB, but this did not happen and the locomotives ended up being known as the Wide Firebox or Boepens Class 16DA.
==Modifications==
Five of these locomotives were delivered with Walschaerts valve gear. The last engine, no. 879, was built with Caprotti valve gear for experimental purposes. This rotary poppet valve gear was driven from a single gearbox on the center of the driving axle. The valve gear was given a fair trial, but was eventually replaced with the standard Walschaerts valve gear in 1940.
They were all delivered with 60 inches (1,520 millimeters) diameter coupled wheels and with their boiler operating pressure set at 195 pounds per square inch (1,340 kilopascals). Four of them were later retyred with 63 inches (1,600 millimeters) diameter tyres on their coupled wheels. At the same time, their operating boiler pressure was raised to 205 pounds per square inch (1,410 kilopascals) to not have their tractive effort reduced by the larger coupled wheels.
When the larger tyres were fitted, the old tyres were left in position and turned down on the wheel center's 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 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 policy resulted in more mileage between heavy repairs, less cost-per-mile on repairs and locomotives capable of higher speeds.
==Service==
The locomotives were placed in service at Kimberley and took over the working of the Union Limited and Union Express between there and Johannesburg from the narrow firebox Class 16DA. They were never stationed at Braamfontein Loco in Johannesburg, but were serviced there in the process of working between Kimberley and Johannesburg. They also worked south from Kimberley to Beaufort West.When the Class 16E arrived in 1935, these Class 16DAs remained in service on the express trains in company with the new locomotives which were also stationed at Kimberley and also worked north to Johannesburg and south to Beaufort West.
In 1939–1940, when new air-conditioned rolling stock was placed in service on the Union Limited and Union Express services between Cape Town and Johannesburg, all the Class 16DA and Class 16E locomotives were transferred to Bloemfontein in the Free State. From here, they continued to work passenger trains north and south, including the Orange Express which was the premier passenger train passing through Bloemfontein. During the 1950s the Orange Express was worked almost exclusively by wide firebox Class 16DA and Class 16E locomotives between Bloemfontein and Kimberley. When the Class 15F replaced them, they were relegated to suburban and local passenger train work. The wide firebox Class 16DA were withdrawn from service in 1973.
==Preservation==
Number	Works nmr 	THF / Private	Leaselend / Owner 	Current Location 	Outside SOUTH AFRICA	?
848 	BALDWIN 60255 	Private 	Wanki Collery 	Main Road 	Zimbabwe 	next to Wanki Highway
850 	BALDWIN 60827 	Private 	Theunissen Municipality 	Main Street 	 	
870 	HOHENZOLLERN 4655	THF 	 	Krugersdorp Locomotive Depot 	 	
876 	HENSC 21752 	THF 	Transnet Heritage Foundation (Museum)	Bloemfontein Locomotive Depot	 	
878 	HENSC 21754 	THF 	Transnet Engineering 	Bloemfontein Locomotive Depot	 	
879 	HENSC 21755 	THF 	Ceres Railway Company 	Cape Town Station 	 	
==Works numbers==
The table lists the Class 16DA engine numbers, works numbers and variations in coupled wheel sizes.
Class 16DA 4-6-2Works Numbers & Variations
SAR No.	Works
No.	Coupled
wheel dia.
874 	21749	63"/1600mm
875 	21750	63"/1600mm
876 	21751	60"/1524mm
877 	21752	60"/1524mm
878 	21753	63"/1600mm
879 	21754	63"/1600mm
==Gallery==
File:Class 16DA no. 879 Caprotti.jpg|No. 879 as built with Caprotti valve gear
File:SAR Class 16DA 876 (4-6-2) Lettie Uys.jpg|No. 876 Lettie Uys at Springfontein, c. 1991
File:SAR Class 16DA 878 (4-6-2).jpg|No. 878 at the Bloemfontein shops, 7 April 2006
File:SAR Class 16DA 879 Orange River - 130479.jpg|No. 879 at Oranjerivier, 13 April 1979
File:SAR Class 16DA 879 (4-6-2).jpg|No. 879 in dark blue Union Limited livery, c. 2002
Category:South African
Category:Henschel locomotives
Category:Built in 1930
Category:Passenger locomotives
Category:4-6-2 steam locomotives
Category:4-6-2 locomotives
Category:Locomotives
Category:Tender locomotives
Category:Steam locomotives