CGR 4th Class 4-6-0TT 1882 Joy

On the Eastern System, problems were experienced with the low-grade local coal from the Cyphergat and Molteno collieries in the Stormberg. It had a high content of non-combustible material which often caused delays since it required frequent stops to allow the stoker to clear the grate of clinker and ash, a tedious task which required the locomotive to be stationary.[1][3]

John D. Tilney, the Eastern System Locomotive Superintendent, carried out many experiments in an attempt to overcome the coal problem. Some of these involved modifying some of the 4th Class locomotives to install oscillating firebars and larger fireboxes.[1]

Another modification by Tilney was an extended smokebox to make room for a very efficient spark arrester which was constructed of wire mesh. Several locomotives were altered to incorporate these spark arresters.[1][5]

Tilney's initiatives did not pass unnoticed. In 1881, the General Manager appointed Hawthorne R. Thornton as Chief Locomotive Superintendent for the whole of the Cape of Good Hope in response to the "growing tendency on the part of the several Locomotive Superintendents to bring in modifications of designs in essential parts of the engines and rolling stock".[3]

In the 1890s, some improvements to smokebox design took place. Extending the smokebox forward increased its volume. The increased amount of exhaust gases present in the smokebox had the effect of stabilising and improving the draught. The date of this improvement can be pinned to 1891 when the second batch of Michael Stephens’ Cape Government Railways (CGR) 5th Class 4-6-0 locomotives with their lengthened smokeboxes entered service. This had such a profound effect on the boiler’s steaming ability that virtually every locomotive on the CGR and NGR had their smokeboxes extended.[6]

4th Class Converted Joy in the Hex River railpass

While the locomotives proved to be good all-purpose engines, the Joy valve gear was not considered entirely satisfactory. After Michael Stephens retired and H.M. Beatty took over as Chief Locomotive Superintendent of the CGR in 1896, all the Neilson-built locomotives were converted to Stephenson valve gear and in the process also had their side-tanks removed. These modified tender locomotives became known as the Converted Joys.[1]

At the time these 4th Class locomotives entered service in 1882, the two Eastern System mainlines were open to King William's Town and approaching Sterkstroom respectively. Those of the Midland System were completed to Graaff Reinet and approaching Cradock respectively, while the Western System mainline was open to Beaufort West.[8]

In early 1897, six Converted Joy locomotives were sold to the Oranje-Vrijstaat Gouwerment-Spoorwegen (OVGS), where they were designated 4th Class G. These engines were all fitted with the Tilney-designed extended smokebox with spark arresters and had been reboilered prior to entering service on the OVGS. During reboilering, their Salter safety valves were replaced with the Ramsbottom type.[1][5]

In 1898, two Converted Joy locomotives, numbers 59 and 71, were sold to Pauling and Company. Pauling's used them during the construction of the Beira and Mashonaland Railway and renumbered them 2 and 1 respectively.[1]

When the Union of South Africa was established on 31 May 1910, the three Colonial government railways (CGR, Natal Government Railways and Central South African Railways) 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 was only implemented with effect from 1 January 1912.[8][9]

By 1912, seventeen of these locomotives survived. They were considered obsolete by the South African Railways, designated Class 04 and renumbered by having the numeral "0" prefixed to their existing numbers. Despite being considered obsolete, some of them were still being employed as shunting locomotives in Port Elizabeth in 1932. The rest had been scrapped by 1918.[1][9]

In 1915, shortly after the outbreak of the First World War, the German South West Africa colony was occupied by the Union Defence Forces. Since a large part of the territory's railway infrastructure and rolling stock was destroyed or damaged by retreating German forces, an urgent need arose for locomotives for use on the Cape gauge lines in that territory. In 1917, numbers 058, 060 to 064, 066 and 0631 were transferred to the Defence Department for service in South West Africa. All eight locomotives are believed to have returned to South Africa after the war.[10]