The cylinders were arranged outside the 4 inches (102 millimetres) thick bar frames, while the piston valves, arranged above the cylinders, were actuated by Walschaerts valve gear.
Reversing was effected by means of a screw gear.
The locomotive had a Belpaire firebox and, instead of the usual deep bridle casting, was built with a shallow casting and frame under the firebox.
This permitted all firebox stays to be removed without lifting the boiler from the frame.

The locomotive was superheated, using the Cole double-header superheater system.
The Cole superheater was somewhat similar to the Schmidt superheater system, except that the Cole type had two headers arranged at either side of the smokebox instead of one at the top.

Each of the eighteen 5 ¹⁄₄ inches (133 millimetres) diameter boiler flues contained four lengths of seamless steam pipes of 1 ¹⁄₂ inches (38 millimetres) outside diameter, arranged in double pairs which were connected at the back ends by return bends and with the two pairs connected to each other at the front by another return bend.
This forced the steam to traverse the entire four pipe lengths before entering the steam chests.
The two free front ends of each such foursome of pipes were bent around to meet the steam headers.
This design of superheater produced a superheat of from 175 to 250 degrees Fahrenheit (79 to 121 degrees Celsius) above saturation temperature.
The cylinders were arranged outside the 4 inches (102 millimetres) thick bar frames, while the piston valves, arranged above the cylinders, were actuated by Walschaerts valve gear. Reversing was effected by means of a screw gear. The locomotive had a Belpaire firebox and, instead of the usual deep bridle casting, was built with a shallow casting and frame under the firebox. This permitted all firebox stays to be removed without lifting the boiler from the frame.
The locomotive was superheated, using the Cole double-header superheater system. The Cole superheater was somewhat similar to the Schmidt superheater system, except that the Cole type had two headers arranged at either side of the smokebox instead of one at the top.
Each of the eighteen 5 ¹⁄₄ inches (133 millimetres) diameter boiler flues contained four lengths of seamless steam pipes of 1 ¹⁄₂ inches (38 millimetres) outside diameter, arranged in double pairs which were connected at the back ends by return bends and with the two pairs connected to each other at the front by another return bend. This forced the steam to traverse the entire four pipe lengths before entering the steam chests. The two free front ends of each such foursome of pipes were bent around to meet the steam headers. This design of superheater produced a superheat of from 175 to 250 degrees Fahrenheit (79 to 121 degrees Celsius) above saturation temperature.
South African Class 10D 4-6-2