South African Class 16DA 4-6-2 1930

South African Railways

Industry	Railway transport
Founded	July 1, 1910 (1910-07-01)
Headquarters	Pretoria , South Africa
Products	Steam locomotives (including Class 16DA)

South African Railways Class 16DA 4-6-2 (1930)

The South African Railways Class 16DA 4-6-2 locomotives introduced in 1930 represent a series of steam engines designed for passenger service.

In that year, six units of the Class 16DA, featuring a 4-6-2 Pacific wheel configuration, were commissioned by the South African Railways. These locomotives were redesigned versions intended to enhance passenger train operations.

Manufacturer

File:16Da 876 Builders Plate.jpg

16Da 876 Builders Plate

In 1930, a contract was awarded to Henschel and Son of Kassel, Germany, for six locomotives destined for the South African Railways (SAR). These engines were modeled on the earlier Class 16DA Pacific types produced in 1928 and 1929, but featured an enhanced design.

Characteristics

File:A.G. Watson.jpg

A.G. Watson

Following his appointment as Chief Mechanical Engineer in 1929, succeeding Colonel Collins, A.G. Watson aimed to boost the steaming efficiency of subsequent Class 16DA orders by developing a boiler incorporating a Wootten style firebox. This firebox was notably wide, offering a grate area of 60 square feet (5.574 square metres). Watson advocated for expansive firegrates combined with enlarged blast pipe caps to maintain a relatively low fuel burning rate per unit grate area, thereby enhancing boiler performance and minimizing the release of sparks and unburnt fuel particles.

The boiler maintained the same girth and tube plate length dimensions as earlier models; however, the tube configuration was altered. The firebox's grate area expanded by one-third compared to the 45 square feet (4.181 square metres) grate size found on the previous Hohenzollern and Baldwin locomotives. Its dimensions were similar to those later fitted to the Class 15E and Class 23 locomotives.

This advanced boiler and firebox assembly was installed on the last six Class 16DA units, numbered between 874 and 879, manufactured by Henschel and delivered in 1930. When compared to their Hohenzollern and Baldwin predecessors, these Henschel-built locomotives exhibited exceptional steaming performance. This success influenced SAR’s decision to standardize wide fireboxes without combustion chambers on all future mainline steam locomotives.

Although the Henschel-produced Class 16DA engines featured significantly broader fireboxes, larger grate areas, and slightly increased trailing wheel diameters compared to the Baldwin and Hohenzollern versions—differences that might have warranted a distinct classification such as Class 16DB—they remained grouped under the Class 16DA designation. These locomotives became commonly known as the Wide Firebox or Boepens Class 16DA.

Modifications

Out of the batch, five locomotives were originally equipped with Walschaerts valve gear. The final unit, number 879, was constructed featuring Caprotti valve gear as part of an experimental trial. This rotary poppet valve mechanism operated via a single gearbox mounted at the center of the driving axle. Although the Caprotti gear underwent thorough testing, it was ultimately replaced by the conventional Walschaerts valve gear in 1940.

All locomotives were initially fitted with coupled wheels measuring 60 inches (1,520 millimetres) in diameter and boilers set to a pressure of 195 pounds per square inch (1,340 kilopascals). Subsequently, four units received new tyres increasing the coupled wheel diameter to 63 inches (1,600 millimetres). To compensate for the potential loss in tractive effort caused by these larger wheels, their boiler pressure was raised to 205 pounds per square inch (1,410 kilopascals).

During the fitting of the larger tyres, the original tyres were retained on the wheel centers and machined down to act as liners, upon which the new tyres were shrunk. This practice of enlarging coupled wheel diameters—along with adjustments to wheel spacing and other factors—was initiated by A.G. Watson during his tenure and sustained by subsequent Chief Mechanical Engineers. Any reduction in tractive effort resulting from increased wheel size was offset by elevating boiler pressures, installing larger cylinders, or a combination of both measures as necessary. This approach led to extended intervals between major overhauls, reduced maintenance costs per mile, and enhanced locomotive speeds.

Service

These locomotives entered service based at Kimberley, where they took over hauling duties for the Union Limited and Union Express trains running between Kimberley and Johannesburg from the narrower firebox Class 16DA engines. Although they were never assigned to Braamfontein Loco in Johannesburg, they received servicing there while operating on the Kimberley-Johannesburg route. Additionally, they handled services extending southward from Kimberley to Beaufort West.

File:SAR Class 16DA 878 (4-6-2) ID.JPG

Following the introduction of the Class 16E in 1935, these Class 16DA units continued operating express services alongside the newer locomotives stationed at Kimberley. Both classes ran routes northward to Johannesburg and southward to Beaufort West.

With the arrival of air-conditioned rolling stock on the Union Limited and Union Express routes between Cape Town and Johannesburg during 1939–1940, all Class 16DA and Class 16E engines were relocated to Bloemfontein in the Free State. From this base, they maintained passenger service operations both north and southbound, including hauling the prestigious Orange Express that passed through Bloemfontein. Throughout the 1950s, wide firebox Class 16DA and Class 16E locomotives predominantly worked the Orange Express between Bloemfontein and Kimberley. When superseded by Class 15F locomotives, these engines were reassigned to suburban and local passenger duties. The wide firebox Class 16DA fleet was ultimately retired from service in 1973.

Preservation

Number	Works Number	THF / Private Ownership	Leaselend / Custodian	Present Location
848	BALDWIN 60255	Private	Wanki Colliery	Main Road
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 following table provides details of the Class 16DA locomotives, including their engine numbers, corresponding works numbers, and the differences in coupled wheel diameters.

Class 16DA 4-6-2
Works Numbers and Wheel Diameter Variations

SAR No.	Works Number	Coupled Wheel Diameter
874	21749	63"/1600 mm
875	21750	63"/1600 mm
876	21751	60"/1524 mm
877	21752	60"/1524 mm
878	21753	63"/1600 mm
879	21754	63"/1600 mm

Illustrations

• No. 879 originally equipped with Caprotti valve gear
  No. 879 originally equipped with Caprotti valve gear
• No. 876 Lettie Uys photographed at Springfontein, circa 1991
  No. 876 Lettie Uys photographed at Springfontein, circa 1991
• No. 878 seen at Bloemfontein workshops on April 7, 2006
  No. 878 seen at Bloemfontein workshops on April 7, 2006
• No. 879 positioned at Oranjerivier, April 13, 1979
  No. 879 positioned at Oranjerivier, April 13, 1979
• No. 879 displaying the dark blue Union Limited livery, around the year 2002
  No. 879 displaying the dark blue Union Limited livery, around the year 2002