4-8-0 Steam Locomotives in New Zealand

Class B (Locobase 9568)

Data from Howell, Comparative Statistics of the Australasian Railways, Journal of the Royal Statistical Society, March 1899, pp. 98-99 and John Garner's [], last accessed 7 September 2008.

Sharp, Stewart of Glasgow contributed four (works #4508-4511) in 1899 and the NZR's own Addington shops built six (works #24, 26, 43, 54-56 in 1899 to 1903) of these sizable Twelve-wheelers. Garner's comment about their design summarizes what one can tell from the specs and from a photograph: "Mechanically the 'B' was years ahead of its time, with a new simple design of piston valve and a modified Walschaerts [sic] valve gear. For their time the 'B's were powerful brutes and rated to haul 600 ton goods trains on easy grades, and could handle 220 tons over the steep grades north of Dunedin."

They were obviously worth retaining and most put in six decades of service, although three of the four Sharp, Stewart locomotives were converted to 4-6-4T class We in 1902 (see Locobase 5189). Four were later refitted with a new boiler fitted with a wide firebox over a eighteen-year period.

Class Ba (Locobase 5164)

Data from John Garner's comprehensive site at [] ... (October 2002; last accessed 25 June 2025); and [] (visited 21 May 2004; revisited 25 June 2025 at []); D[ennis] Rock Carling, 4-8-0 Tender Locomotives (New York: Drake Publishers, Inc, 1972), p. 81 and serial 231 on table XIII [13], pp.106-107. Works numbers were 122 in 1911, 123-128 in 1912, and 129--131 in 1913.

Rolling on the NZR's Cape Gauge, these locomotives were intended for heavy freight work at speeds no greater than 30 mph (48 kph) on the South Island. Garner notes, however, that they also hauled passenger trains in the Otago area.

Of the 10, the NZR rebuilt two in 1928 with larger fireboxes and boilers to raise steaming capacity to main-line requirements. Mainline Steam Heritage Trust notes that this was a substantial effort. The boiler's centerline was raised from 6' 3" (1.9 m) to 7' 4" (2.23 m), the grate area enlarged to 26.4 sq ft (2.45 sq m), and pressure raised to 200 psi (14.06 bar). Tractive effort climbed to 21,200 lb (9,616 kg).

Obviously, this was not an urgent requirement as the other three to be made over were only modified in 1948-1949. Rated to haul 700-750 tons on the level, MSHT's account states "a wide-firebox Ba could surmount the notorious Mihiwaka Bank (north of Dunedin) with 270 tons, 50 tons better than one of the other members of the class fitted with a narrow-firebox boiler."

Other than the 555, withdrawn in June 1957, the Bas worked into the 1960s, eight lending their power to shunting. Modifications included a tender cab featuring a full-height structure on the locomotive end of the tender for better weather protection.

Of these, 552 survived the dissolution of the class thanks to its purchase by L J Hostick and his subsequent excursions to other parts of New Zealand.

Class Bb (Locobase 5165)

Data from John Garner's comprehensive site at [] ... (October 2002; last accessed 25 June 2025). See also "New Engines for the New Zealand Government Rys", Locomotive Magazine, Volume XXIII [23] (15 February 1917), p. 20; andSee also D[ennis] Rock Carling, 4-8-0 Tender Locomotives (New York: Drake Publishers, Inc, 1972), Table XIII [13], item 233, pp. 108-109. Works numbers were 63-74 in 1915, 75-82 in 1916, 83-90 in 1917, and 91-92 in 1918.

An obvious follow-on class to the Bas (Locobase 5164) with cylinders 1" (25.4 mm) larger in diameter, these 12-wheelers had the same small boilers and low factor of adhesion. A G Price replaced the Belpaire fireboxes fitted to the Ba with a round-top boiler.

John Garner wrote that ten of these engines were switched to shunting duties, where they were quite successful. That success led to the conversion of the entire class between 1932 and 1938.