The South African Railways Class Experimental 6 4-8-0 of 1906 was a steam locomotive from the pre-Union era in the Cape of Good Hope. In 1906, the Cape Government Railways placed a single experimental 10th Class steam locomotive with a Mastodon type wheel arrangement in service on its Eastern System. In 1912, when this locomotive was assimilated into the South African Railways, it was renumbered and designated Class Experimental 6. Manufacturer The Cape 10th Class steam locomotive was designed by H.M. Beatty, the Locomotive Superintendent of the Cape Government Railways (CGR) from 1896 to 1910. The designs were prepared at the Salt River shops of the CGR in Cape Town and represented a further effort on Beatty's part to improve the steaming efficiency of his 8th Class of 1904. The 10th Class was, in most respects, a larger and more powerful version of the 8th Class, which it was meant to eventually replace on the Eastern System. In 1906, only one locomotive with a Type XF2 tender was delivered by Kitson and Company, numbered 880. Characteristics With this locomotive, as with the 9th Class Mikado which had been delivered by the same manufacturer earlier in that same year, Beatty overcame his aversion to boiler centre lines which exceeded twice the Cape gauge track width of above the railhead. The boiler pitch of the Cape 10th Class was at . In the designs of the two Cape 9th Class Mikado types, later the Classes Experimental 4 and Experimental 5, Beatty had achieved improved steaming efficiency by extending the locomotive frames with a bridle casting, such as the one he had designed for the CGR 6th Class 2-6-4 in 1901, to accommodate deep and wide fireboxes. With the 10th Class, on the other hand, he obtained a wide firebox by spreading the grate over the rear coupled wheels, hence the requirement to raise the boiler pitch. The front portion of the firebox formed a combustion chamber, which reduced spark throwing and thereby reduced wear on the tube ends. The inside of the firebox was of copper and the plates were thick throughout, except for the tube plate, which was thick at the tube ends. This firebox design was uncomplicated and allowed for liberal water spaces. The result was a firebox which was virtually a copy of the one which was used on the Hendrie B locomotive which had been placed in service