NZR AB class

NZR AB class

Preserved AB 778 hauling the Kingston Flyer
Type and origin
Power type Steam
Builder NZGR Addington Workshops (38)
North British Locomotive Company (83)
A & G Price Limited, Thames (20)
Build date 1915–1918, 1921–1927
Total produced 141
Specifications
Configuration 4-6-2
Gauge 3 ft 6 in (1,067 mm)
Driver dia. 54 in (1.372 m)
Wheelbase 52 ft 6 in (16.00 m)
Length 62 ft 5 in (19.02 m)
Loco weight 51.3 long tons (52.1 tonnes; 57.5 short tons)
Tender weight 33.4 long tons (33.9 tonnes; 37.4 short tons)
Total weight 84.7 long tons (86.1 tonnes; 94.9 short tons)
Fuel type Coal
Fuel capacity 4.0 long tons (4.1 tonnes; 4.5 short tons)
Water cap 3,500 imp gal (16,000 l; 4,200 US gal)
Firebox:
  Firegrate area
33 sq ft (3.1 m2)
Boiler pressure 180 lbf/in2 (1.24 MPa)
Heating surface 1,148 sq ft (106.7 m2)
Superheater:
  Heating area 204 sq ft (19.0 m2)
Cylinders Two, outside
Cylinder size 17 in × 26 in (432 mm × 660 mm)
Performance figures
Maximum speed 60 mph (97 km/h)
Tractive effort 20,030 lbf (89.10 kN)
Career
Operators NZR
Numbers 608–838
Locale All of New Zealand
First run October 1915
Withdrawn 1963–1969
Preserved 7 (608, 663, 699, 745, 778, 795, 832)
Current owner Kingston Flyer, Mainline Steam, Pleasant Point Museum and Railway, Museum of Transport and Technology, Ferrymead Railway, Rimutaka Incline Railway Heritage Trust.
Disposition Seven preserved, two lost in the wreck of Great Barrier Island in 1922, remainder scrapped.

The NZR AB class was a class of 4-6-2 Pacific tender steam locomotive that operated on New Zealand's national railway system. Originally an improvement on the 1906 A class, 141 were built between 1915 and 1927 by NZR's Addington Workshops, A & G Price Limited of Thames, New Zealand, and North British Locomotive Company, making the AB class the largest class of steam locomotives ever to run in New Zealand. An additional ten were rebuilt from the tank version of the AB – the WAB class – between 1947 and 1957. Two North British-made locomotives were lost in the wreck of the SS Wiltshire in May 1922.

Construction and design

The genesis of the AB class originated from the construction of A class 4-6-2 NO 409 at Addington Railway Workshops in 1906. A two-cylinder simple-expansion locomotive, 409 was initially classified AB to differentiate it from the four-cylinder compound A and AD class locomotives, which were by and large of a similar design although built as compounds. AB 409 was in reality the 'guinea pig' for what would become the most prolific type on the New Zealand Railways network, with construction beginning on a new prototype 4-6-2 in 1915.

The new locomotive, AB 608, was to a completely different design from AB 409 when it emerged from the Addington Workshops in 1915. Although largely similar to the A class, it had a new design of cab and boiler, which was fitted with a superheater after trials conducted on AB 409. It also had the distinctive Vanderbilt tender, which would become a hallmark of the AB class during its working life. This locomotive was to become the first of 141 similar locomotives built by various builders in New Zealand and the United Kingdom for NZGR.

Introduction

The AB class compared more favourably in service against the compound A class. Reputedly the first engine able to generate one horsepower for every 100 pounds of weight (16.4 W/kg), the AB class was efficient and versatile, and the engines were easy to maintain and operate. However, it became clear that there were several shortcomings of the design – notably the cab was too small, and the tenders were not sturdy enough. A new and longer cab was fitted to all new locomotives being built from that time onwards, with the first appearing on AB 663. New tender structures were also built at a later date.

The locomotives were extremely versatile, and the AB class were used on almost every section of the NZR network, the exception being the Nelson Section (closed 1955). In later years, the class were displaced from their mainline duties first by the larger J and K series locomotives, and later by the arrival of diesels (DA and DG classes in the North Island,DH and DJ classes in the South Island). As a result of the arrival of new diesels in the North Island from 1955 onwards, many of the North Island-based locomotives were transferred to the South Island to see out their remaining working lives.

The final duties of the AB class were on branchline workings, where they found their niche after being displaced from most mainline duties by larger locomotives. These in turn displaced the A and Q class 4-6-2 locomotives from their duties, resulting in the withdrawal of all Q class locomotives by 1957 and a reduction in the number of A class locomotives. The locomotives also worked some lesser mainline duties, and others, such as those at Gisborne, were used as bankers to assist trains heading south to Napier.

Being highly capable, the AB class were used for both freight and passenger trains. The AB class was easily able to pull an express passenger train at speeds of 100 km/h (62 mph), or haul 700-tonne goods trains on easy grades. They, along with the earlier 'F' class, were known as the 'Maids of all work'. Their work on express passenger trains was diminished by the arrival of the J class of 1939, and K class of 1932 tender locomotives in the 1930s, and also with the introduction of the heavier steel-panelled carriages built from 1930 until 1943. Despite being displaced, the AB class could still be found at work on relief expresses during holiday periods.

The locomotives did not change greatly during their NZR career. The first change was to fit Waikato-type spark arrestors to many of the North Island-based engines, resulting in a new 'pear-shaped' smokebox with an ash hopper at the base of the smokebox. The cast-iron smokebox doors were replaced by steel ones, and the brake pump was moved from its original location on the right-hand side of the smokebox to a new position, recessed into the running board, just forward of the cab on the same side.

Another notable change was that many of the class were fitted with ballast blocks for mechanical purposes. As the locomotives rode well, this was not to prevent derailments as with the Q class 4-6-2s of 1901. Furthermore, certain engines were not fitted with ballast blocks, so their inclusion is questionable. Other cosmetic changes included fitting a large Pyle National electric headlight on top of the smokebox and replacement of the copper-capped funnels with the standard NZR 'flowerpot' type.

Components

Boilers

The AB type boiler had a working pressure of 180psi, a standard across the type. These boilers were of standard construction, no matter which firm built them, and as such were interchangeable across any locomotives of the type. They were also similar to the boilers built for the WAB and WS class 4-6-4T tank locomotives in 1939 - in fact, the WAB boiler and AB boilers were the same, with those fitted to the WAB fitted with the necessary components to draw water from the locomotive's side tanks.

This type of boiler was also adapted for use on the Q and AA class 4-6-2 tender locomotives of 1901 and 1915 respectively when their original boilers wore out. In the case of the AA class, the boiler change was not necessitated by the condition of the boilers but due to the limitations of the original boilers. The replacement took place in the 1930s, and these locomotives gained new heights of reliability, before they were withdrawn in 1957 (at the same time as the Q class). All of these boilers were then put back into the AB class pool, and were reused on engines of that class.

In all, 6 separate classes used the standard AB boiler. When Q, AA and G class locomotives were scrapped in the 1950s, the boilers were overhauled to keep locomotives of A, AB, and WAB serviceable.

Tenders

Throughout their NZR careers, the AB class were known for their Vanderbilt tenders - one of three classes to use this tender, the others being the re-built G class 4-6-2, and the later J/Ja/Jb class 4-8-2 engines. The tenders, although satisfactory, suffered from having been constructed too lightly for the intended task, and were also prone to rusting, particularly around the frame channels. This necessitated the complete replacement of the tender frames from some locomotives, although not all were treated so.

The standard AB tender design was adapted for the three-cylinder G class locomotive 4-6-2 tender locomotive rebuilds of 1937. These tenders had a more substantial tender underframe, and was also unique in that the body was of welded construction rather than the traditional riveted style. As such, they became known as the 'G' style tender. When the six locomotives were withdrawn in 1956, their tenders were fitted to AB class locomotives.

Further 'G' type tenders were constructed later on by Addington Workshops (Christchurch) and Otahuhu Workshops (Auckland) for AB class locomotives whose tenders were not considered to be economically repairable. However, this was not always the case:

With 141 members of this type in New Zealand, tenders were inevitably swapped with other locomotives. For example, a locomotive undergoing overhaul might lose its good-condition tender to another with a poor-condition tender to speed up the process of outshopping the second locomotive. All tenders of the type were numbered; the number was made out of weld and was positioned just below the tender headlight bracket.

The tenders initially rode on drawing x-6002 standard bogies fitted with grease-lubricated bearings. Later, drawing x-10161 bogies, still fitted with grease-lubricated bearings were substituted on some locomotives as they came in for overhaul. A later variant was the drawing x-11183 'Timken' roller-bearing bogie fitted to the WAB class conversions of 1947-57 and as used under the G class locomotive tenders from 1937. Enthusiasts were able to identify these different types of bogies by their design characteristics - for example, the x-6002 bogies had a prominent journal box and were made of steel bar sections.

Frame replacement

During the late 1950s to early 1960s, many older AB class locomotives were being withdrawn as they wore out and were replaced by locomotives displaced from other regions. With many engines still in relatively good condition, these engines were cannabalised following withdrawal to keep other engines going until they were either worn out or replaced by the new diesel locomotives then being purchased by NZR. This became a fairly common practice at the time; as the locomotives were of a standard design, parts could be taken from any engine to ensure another could keep running for some time to come.

One example of this was AB 792, one of the ten WAB class conversions from 1947-57. Shopped for an 'A' grade overhaul at Hillside Workshops, the locomotive had a cracked mainframe but was otherwise in mechanically good condition. It was decided to use part of the good-condition frames from under AB 661, then recently withdrawn, to replace the damaged section from 792. The locomotive's frame was then altered by cutting the affected section out and fitting the new frame section, ex-661.

This meant that certain locomotives should have changed identity - the identity of the locomotive is attached (supposedly) to the frame of the locomotive. Therefore, AB 792 should have become AB 661 as a result of the frame repairs. However, with 661 written off and 792 being a younger locomotive that still had an economic career ahead, the NZR would not have considered 'returning' 661 to service and 'scrapping' 792.

Class roster

Key: In service On lease Out of service Preserved Overhaul/Repair Scrapped
Road
number
Builder Builders
number
In
service
Converted
from WAB class
Written
off
Comments
732 North British 22878 Lost in the wreck of the Wiltshire, Rosalie Bay, Great Barrier Island, 1922.
762 North British 22879 Lost in the wreck of the Wiltshire, Rosalie Bay, Great Barrier Island, 1922.
608 NZR Addington 163 10-1915 10-1967 Preserved, New Zealand Railway and Locomotive Society. On loan to Steam Incorporated. Named "Passchendaele" as the NZR War Memorial Locomotive in 1925. Operational and mainline certified.
609 NZR Addington 164 12-12-1915 25-4-1964
610 NZR Addington 165 1-1916 8-1968
611 NZR Addington 166 3-1916 8-1960
612 NZR Addington 167 5-1916 10-1967
613 NZR Addington 168 6-1916 10-1967
614 NZR Addington 183 5-1917 29-2-1964
615 NZR Addington 170 8-1916 4-1966
616 NZR Addington 171 9-1916 9-1967
617 NZR Addington 172 10-1916 3-1969
658 NZR Addington 169 8-1916 10-1968
659 NZR Addington 184 7-1917 29-2-1964
660 NZR Addington 185 8-1917 8-1968
661 NZR Addington 186 9-1917 31-3-1964
662 NZR Addington 187 11-1917 10-1967
663 NZR Addington 188 12-1917 7-1969 Preserved Mainline Steam. Named "Sharon Lee".
664 NZR Addington 189 2-1918 11-1963
665 NZR Addington 190 3-1918 4-1963
688 NZR Addington 191 10-1921 5-1968
689 NZR Addington 192 1-1922 4-1967
690 NZR Addington 215 3-1922 3-1969
691 NZR Addington 216 6-1922 7-1968
692 NZR Addington 217 8-1922 10-1968
693 NZR Addington 218 11-1922 3-1969
694 NZR Addington 219 12-1922 3-1969
695 NZR Addington 220 2-1923 4-1966
696 NZR Addington 221 4-1923 20-6-1964
697 NZR Addington 222 5-1923 20-6-1964
698 A & G Price 93 5-1922 10-1959
699 A & G Price 94 8-1922 3-1968 Preserved, Pleasant Point Museum and Railway.
700 A & G Price 95 9-1922 1-1966
701 A & G Price 96 12-1922 7-1968
702 A & G Price 97 5-1923 3-1965
703 A & G Price 98 7-1923 9-1966
704 A & G Price 99 9-1923 6-1969
705 A & G Price 100 10-1923 3-1969
706 A & G Price 101 11-1923 7-1969
707 A & G Price 102 6-1924 3-1969
708 A & G Price 103 7-1924 11-1966
709 A & G Price 104 8-1924 11-1966
710 A & G Price 105 10-1924 10-1963
711 A & G Price 106 12-1924 11-1966
712 A & G Price 107 2-1925 7-1965
713 A & G Price 108 3-1925 7-1968
714 A & G Price 109 6-1925 9-1966
715 A & G Price 110 8-1925 5-1968
716 A & G Price 111 10-1925 3-1964
717 A & G Price 112 12-1925 10-1967
718 North British 22848 1-1922 3-1969
719 North British 22849 1-1922 7-1968
720 North British 22853 1-1922 8-1968
721 North British 22856 2-1922 3-1969
722 North British 22857 2-1922 11-1966
723 North British 22860 3-1922 10-1968
724 North British 22869 4-1922 3-1969
725 North British 22873 4-1922 3-1969
726 North British 22875 5-1922 10-1968
727 North British 22876 5-1922 7-1968
728 North British 22877 5-1922 8-1968
729 North British 22881 7-1922 10-1968
730 North British 22883 8-1922 3-1969
731 North British 22884 9-1922 3-1969
732 North British 23043 10-1923 3-1969 The second AB 732; replaced the original lost in the wreck of the SS Wiltshire.
733 North British 22838 11-1921 4-1966
734 North British 22845 12-1921 2-1965
735 North British 22844 12-1921 3-1968
736 North British 22841 12-1921 3-1966
737 North British 22847 1-1922 3-1969
738 North British 22852 1-1922 1-1965
739 North British 22855 2-1922 7-1965
740 North British 22859 2-1922 10-1967
741 North British 22868 2-1922 2-1965
742 North British 22872 4-1922 2-1965
743 North British 22871 4-1922 6-1969
744 North British 22874 5-1922 3-1964
745 North British 22880 7-1922 1-1957 Preserved, Rimutaka Incline Railway Heritage Trust.
746 North British 22885 8-1922 3-1969
747 North British 22836 12-1921 10-1963
748 North British 22837 11-1921 9-1966
749 North British 22839 1-1922 10-1959
750 North British 22840 1-1922 6-1964
751 North British 22842 12-1921 10-1967
752 North British 22843 12-1921 2-1964
753 North British 22846 1-1922 10-1968
754 North British 22850 2-1922 3-1969
755 North British 22851 2-1922 3-1968
756 North British 22854 3-1922 8-1962
757 North British 22858 3-1922 3-1964
758 North British 22866 3-1922 9-1966
759 North British 22867 4-1922 1-1965
760 North British 22870 4-1922 3-1964
761 North British 22882 8-1922 6-1965
762 North British 23039 9-1923 10-1967 The second AB 762; replaced the original lost in the wreck of the SS Wiltshire.
773 North British 23040 9-1923 10-1968
774 North British 23041 9-1923 10-1959
775 North British 23042 9-1923 10-1958
776 NZR Addington 233 5-1925 4-1966
777 NZR Addington 234 6-1925 3-1969
778 NZR Addington 235 9-1925 7-1969 Preserved, Kingston Flyer.
779 NZR Addington 236 12-1925 7-1968
780 NZR Addington 237 2-1926 3-1969
781 NZR Addington 238 3-1926 8-1968
782 NZR Addington 239 5-1926 7-1969
783 NZR Addington 240 7-1926 11-1966
784 NZR Addington 241 9-1926 3-1969
785 NZR Addington 242 10-1926 2-1963
786 NZR Hillside 243 1926 as WAB 9-1947 10-1968
787 NZR Hillside 244 1926 as WAB 10-1947 4-1966
788 NZR Hillside 245 1926 as WAB 1-1948 3-1969
789 NZR Hillside 246 1926 as WAB 8-1947 3-1969
790 NZR Hillside 247 1926 as WAB 7-1957 2-1966
791 NZR Hillside 248 1926 as WAB 11-1947 10-1967
792 NZR Hillside 249 1927 as WAB 6-1947 7-1969
793 NZR Hillside 250 1927 as WAB 2-1948 3-1969
795 NZR Hillside 252 1927 as WAB 12-1947 7-1969 Preserved, Kingston Flyer.
798 A & G Price 115 1926 as WAB 11-1957 3-1969
803 A & G Price 120 1927 as WS 12-1957 7-1968
804 North British 23173 6-1925 4-1966
805 North British 23174 7-1925 7-1968
806 North British 23175 7-1925 3-1969
807 North British 23176 7-1925 3-1969
808 North British 23183 7-1925 9-1967
809 North British 23184 7-1925 4-1966
810 North British 23185 7-1925 10-1967
811 North British 23186 7-1925 7-1969
812 North British 23182 7-1925 10-1967
813 North British 23187 7-1925 3-1969
814 North British 23177 6-1925 3-1964
815 North British 23178 6-1925 11-1936
816 North British 23179 6-1925 6-1969
817 North British 23180 6-1925 11-1966
818 North British 23191 8-1925 10-1963
819 North British 23192 8-1925 11-1966
820 North British 23193 7-1925 3-1969
821 North British 23194 7-1925 3-1969
822 North British 23195 7-1925 3-1969
823 North British 23196 7-1925 7-1969
824 North British 23197 8-1925 1-1966
825 North British 23198 8-1925 10-1967
826 North British 23203 9-1925 10-1967
827 North British 23207 9-1925 5-1964
828 North British 23207 8-1925 8-1966
829 North British 23181 6-1925 5-1968
830 North British 23188 7-1925 10-1959
831 North British 23189 7-1925 3-1969
832 North British 23190 7-1925 12-1967 Preserved, Museum of Transport and Technology. On loan to the Glenbrook Vintage Railway.
833 North British 23199 7-1925 4-1966
834 North British 23200 7-1925 9-1966
835 North British 23201 7-1925 2-1964
836 North British 23202 8-1925 9-1963
837 North British 23205 8-1925 8-1965
838 North British 23206 8-1925 9-1966

[2]

Withdrawal

The majority of the class was withdrawn from NZR services during the 1960s, as diesel traction replaced steam, with the last concentrations of the AB class being located on the West Coast and in Southland. Many of those withdrawn were South Island locomotives which had reached the end of their economic lives between 1963 and 1967 (when the DJ class diesels arrived) and were replaced by ex-North Island locomotives. By 1971, several still remained on the books at the close of steam operations on the NZR.

Three remained on NZR books in 1972 - AB's 778 and 795 remained at Lyttelton to heat the carriages for the 'Boat Train', formerly known in an informal manner as the 'Jackaroo', while AB 663 remained either at Greymouth's Elmer Lane locomotive depot or at Dunedin. With interest for a nostalgic steam-operated train growing, both 778 and 795 were restored that same year for the famous Kingston Flyer, possibly New Zealand's most famous heritage railway. AB 663 was used initially at Dunedin for spare parts to keep 778 and 795, now named David McKellar and Greenvale respectively.[3]

The Kingston Flyer continues to run today with both AB's 778 and 795 as its principle motive power. Five other locomotives have been preserved by various other groups.

Names

AB 608 gained the notable distinction of being named Passchendaele in 1918 to commemorate the NZR staff who had been killed in the First World War. The locomotive had its nameplates removed in the 1940s, and they were placed on display in the Christchurch and Dunedin railway stations. Two replicas were made in 1963 for the NZR centenary event, and these are held by the New Zealand Railway & Locomotive Society. Other reproductions have been made, including one for the KiwiRail War Memorial at Hutt Workshops, which was dedicated in 2010. This was the only steam locomotive to be named after 1877.[4]

AB 663 was named Sharon Lee when it was restored to running condition in 1997. The locomotive is named after Sharon Lee Welch, daughter of Mainline Steam Trust principle Ian Welch.

AB 778 and AB 795 were named David McKellar (778) and Greenvale (795) respectively by NZR in 1971 when they were overhauled for the Kingston Flyer heritage train between Lumsden and Kingston.

Preservation

Seven AB class locomotives have been preserved:

Similar locomotives

The WAB class of 1917 was essentially a tank locomotive version of the AB class.

Preserved AB Class Locomotives

Key: In service In service, Mainline Certified Under overhaul/restoration Stored Static display Scrapped
Key: In service On lease Out of service Preserved Overhaul/Repair Scrapped
Number Builder Introduced Withdrawn[n 1] Current status Notes
608 NZR Addington Workshops October 1915 October 1967 In service (mainline certified) Preserved, New Zealand Railway and Locomotive Society. Leased to Steam Incorporated. Named "Passchendaele".
663 NZR Addington Workshops December 1917 July 1969 In service (mainline certified) Preserved, Mainline Steam. Named "Sharon Lee".
699 A & G Price August 1922 March 1968 Under overhaul Preserved, Pleasant Point Museum and Railway.
745 North British July 1922 January 1957 Stored (non-operational) Preserved, Rimutaka Incline Railway Heritage Trust.
778 NZR Addington Workshops September 1925 July 1969 Stored (non-operational) Preserved, Kingston Flyer. Named "David McKellar".
795 NZR Hillside Workshops May 1927 July 1969 Stored (operational). Preserved, Kingston Flyer. Originally built as a Wab class locomotive. Named "Greenvale".
832 North British July 1925 December 1967 Stored (non-operational) Preserved, Museum of Transport and Technology. Leased to the Glenbrook Vintage Railway.
  1. Withdrawn dates are the date from when the locomotive was withdrawn by NZR.

References

  1. http://www.nzsee.org.nz/db/Bulletin/Archive/02(1)0059.pdf
  2. Register of New Zealand Railways Steam Locomotives 1863–1971 ISBN 0-9582072-1-6
  3. http://www.trainweb.org/nzsteam/ab_reg.htm
  4. Sean Millar, The NZR Steam Locomotive, NZR&LS, 2011.
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