NZR KB class

From Wikipedia, the free encyclopedia
Jump to: navigation, search
NZR KB class
Type and origin
Power type Steam
Builder NZR Hillside Workshops, Dunedin
Build date 1939
Configuration 4-8-4
Gauge 3 ft 6 in (1,067 mm)
Wheel diameter 54 in (1.372 m)
Wheelbase 34 ft 10 in (10.62 m)
Length 69 ft 8 in (21.23 m)
Width 8 ft 6 in (2.59 m)
Height 11 ft 6 in (3.51 m)
Adhesive weight 56.0 long tons (56.9 t; 62.7 short tons)
Loco weight 94.8 long tons (96.3 t; 106.2 short tons)
Tender weight 52.9 long tons (53.7 t; 59.2 short tons)
Total weight 147.7 long tons (150.1 t; 165.4 short tons)
Fuel type Coal
Fuel capacity 7.5 long tons (7.6 t; 8.4 short tons)
Water cap 5,000 imp gal (23,000 L; 6,000 US gal)
 • Firegrate area
47.7 sq ft (4.4 m2)
Boiler pressure 200 psi (1,379 kPa)
Feedwater heater ACFI
Heating surface 1,984 sq ft (184.3 m2)
 • Heating area 485 sq ft (45.1 m2)
Cylinders 2 driving
2 booster
Cylinder size 20 in × 26 in (508 mm × 660 mm)
Performance figures
Power output 1,400 hp (1,000 kW)
Tractive effort 30,815 lbf (137.07 kN)
36,815 lbf (163.76 kN) with booster
Number in class 6
Numbers 965 - 970
Locale South Island of New Zealand, mainly the Midland line
First run 1939 - 1940
Last run December 1968
Retired 1967 - 1969
Current owner Mainline Steam
Disposition Withdrawn; 1 preserved

The NZR KB class of 1939 was a class of mixed traffic steam locomotives that operated on New Zealand's railway network. They were built by the New Zealand Railways Department (NZR) after the success of the K class to meet the increasing traffic demands on the Midland Line in the South Island. The locomotives had a wheel arrangement of 4-8-4 and first appeared with distinctive streamlining, mainly to hide their ACFI feedwater systems.


Following the success of the K class in the North Island, there was a need for similar locomotives to operate the Midland Line, primarily between Springfield and Arthur's Pass. These new locomotives incorporated a number of improvements upon the K class, including a re-designed plate frame to eliminate cracking issues the K class experienced; roller bearings on all wheels; hydrostatic lubrication throughout; and the inclusion of the ACFI feed-water system that had been pioneered on K 919. The ACFI equipment's aesthetic appearance had been criticised, hence the KB and contemporary KA classes were both fitted with shrouding to obscure it.

The KB class were technically very similar to the KA class, but were distinguished by the inclusion of a booster on the rear axle of the trailing bogie and Nicholson thermic syphons in the firebox. The use of the booster, first proposed for the K class in 1932, was mainly due to steeper gradients and heavy freight trains on the Midland Line, especially Cass bank. Additional piping and sanding equipment for the booster gave the KB a slightly different appearance to the KA. The booster was intended solely for use at low speed, and some class members ultimately had the booster removed due to problems such as jamming in gear, reducing the locomotive's top speed.

Building of the locomotives commenced in 1939. Construction and assembly took place at NZR's Hillside Workshops. The first of the six member class was produced before the first of the KA class then under construction at Hutt Workshops. All of the class were in service by 1940.

In service[edit]

As intended, the KB class were based solely in the South Island and performed most of their work hauling freight trains on the Midland Line. However, during the Second World War, they were also used on the Main South Line.

While the aesthetic shrouding cleaned up the appearance of the locomotives, it was open at the top and gathered soot and dust which affected the working environment in the cab. After the war, the aesthetic shrouding was removed from the locomotives and the ACFI feed-water system was replaced with an exhaust steam injector.

Although the K and KA classes were converted to burn oil at the time, the KBs remained as coal burners due to the availability of high grade West Coast coal.

Withdrawal and disposal[edit]

From the mid-1950s, dieselisation impacted the utilisation of the KB class. This became especially pronounced in the 1960s, and the introduction of the DJ class in 1968 brought about their ultimate demise. As they were displaced from duties in the late 1960s, some members were used on the Main South Line, including hauling the South Island Limited.

The first withdrawals were KBs 966 and 969 in October 1967; both were cut up for scrap. KB 969 was withdrawn after hauling the only ever double-headed KB train, having suffered a cracked motion bracket. Before it was sent to the breakers' yard, it was inscribed with a message reading "Goodbye Kb 969, you'll come back as roofing iron".[1]

KB 967 was withdrawn in October 1968. This left only three KB's in service (965, 968 and 970), and of those, only 968 was serviceable; the remaining two were withdrawn by March 1969. 968 made its last journey on 22 June 1969, hauling a railway enthusiast's excursion from Christchurch to Arthur's Pass and return.


NZR donated members of the K and KA classes for preservation, but due to the considerable technical similarities, it chose not to donate a KB. Instead, enthusiasts had to purchase one at the scrap market rate of NZ$1500 (equal to $22,200 in December 2008 dollars[2]). KB 968 was supposed to be cut up the week following its last excursion, but a collection on the return journey was sufficient to temporarily save the locomotive.[1] Retired school teacher Cyril Evans raised the rest of the $1500 by showing railway films to Christchurch school children and collecting their donations. The locomotive was then vested into the Ferrymead Trust on behalf of the children of Canterbury and was displayed for a number of decades at the Ferrymead Railway. It is currently under restoration to main line operating condition at Mainline Steam's Christchurch depot.

List of locomotives[edit]

Key: In service On lease Out of service Preserved Overhaul/Repair Scrapped
Number Builder Introduced[3] Withdrawn [3] Notes
965 NZR Hillside Workshops June 1939 March 1969
966 NZR Hillside Workshops August 1939 October 1967
967 NZR Hillside Workshops September 1939 October 1968
968 NZR Hillside Workshops October 1939 March 1969 Preserved, Ferrymead Trust. Currently on-loan to Mainline Steam.
969 NZR Hillside Workshops December 1939 October 1967
970 NZR Hillside Workshops January 1940 March 1969


  1. ^ a b Sinclair, Roy (1987). Rail - The Great New Zealand Adventure. Wellington, New Zealand: Grantham House Publishing. pp. 140–145. ISBN 978-1-86934-013-1. 
  2. ^ "New Zealand CPI Inflation Calculator - Reserve Bank of New Zealand". Retrieved 2009-03-27. 
  3. ^ a b "Kb Class 4-8-2 Register". Retrieved 2008-10-29. 

External links[edit]