NZR BB class

NZR BB class
Type and origin
Power type Steam
Builder A & G Price, Thames, NZ
Serial number 63–92
Build date 1915 (12), 1916 (8), 1917 (8), 1918 (2)
Specifications
Configuration 4-8-0
UIC class 2'Dh
Gauge 3 ft 6 in (1,067 mm)
Driver diameter 42.5 in (1.080 m)
Length 52 ft 7 1⁄2 in (16.04 m)
Adhesive weight 32.5 long tons (33.0 t; 36.4 short tons)
Loco weight 43.5 long tons (44.2 t; 48.7 short tons)
Tender weight 25.5 long tons (25.9 t; 28.6 short tons)
Fuel type Coal
Fuel capacity 4 long tons (4.1 t; 4.5 short tons)
Water cap 1,700 imp gal (7,700 l; 2,000 US gal)
Firebox:
 • Firegrate area		 16.8 sq ft (1.56 m2)
Boiler pressure 175 psi (1.21 MPa)
Heating surface 724 sq ft (67.3 m2)
Superheater:
 • Heating area		 208 sq ft (19.3 m2)
Cylinders Two, outside
Cylinder size 17 in × 22 in (432 mm × 559 mm)
Performance figures
Maximum speed 40 mph (64 km/h)
Tractive effort 20,940 lbf (93.1 kN)
Career
Number in class 30
Numbers 55, 109, 143, 144, 147, 167, 169, 171, 197, 222, 618–637
Preserved 1 (BB 144)
Disposition One preserved, remainder scrapped

Origin and Design

The BB class of steam locomotives comprised 30 engines operated by New Zealand Railways in the North Island of New Zealand. Ordered to replace smaller locomotives of several classes in the North Island, they were similar in design and appearance to the preceding B and BA classes. The first BB class locomotive entered service in February 1915, with the last to commence operations doing so on 8 March 1917. All were built by A & G Price Ltd of Thames, New Zealand, and as their cylinders had a larger diameter than the B and BA locomotives they were capable of generating more power to haul heavier trains. The most visible difference however was the roundtop firebox in place of the preceding classes Belpaire design. The BB class could haul up to 700 long tons (710 t; 780 short tons) of freight on a level railway line, though they were limited to a top speed of around 40 mph (64 km/h).

Service

The BB class did not solely haul freight trains. They were also utilised to haul passenger trains, generally on branch lines where light track meant trains could not be operated at speeds unattainable for the BB class. These trains included services for miners working in coal mines along branches in the Waikato region (e.g. Glen Massey Branch). However, they arrived at the same time as the AB class pacific, and as these proved equally adept at hauling freight trains of similar tonnage they were proliferated while no further BB types were ordered.

In the later days of steam, powerful locomotives such as the K class were hauling heavy trains that the C class and other shunting locomotives at yards and depots simply could not handle. Accordingly, ten members of the BB class were modified to perform shunting duties between 1932 and 1938, and they successfully took on the heaviest of roles.

Most BB locomotives survived into the 1960s. In later years they were concentrated at the yards in Auckland, Frankton and Palmerston North. In the mid 1960s four were sent to Dunedin and Invercargill. During that decade, the complete withdrawal of the class was undertaken progressively, with the last two, BB 626 and BB 633, formally removed from service in August 1968. Another one of the last to be withdrawn was BB 144 in October 1967. It was purchased by Les Hostick. Today it is lease to Ian Welch and is under restoration at the Mainline Steam Heritage Trust's Parnell depot. No other BB locomotive has been preserved.

Class register

Key: In service Out of service Preserved Overhaul/Repair Scrapped
Road
number 		In
service 		Written
off 		Comments
55 1-1917 7-1965
109 3-1917 31-3-1964
143 4-1917 5-1959
144 7-1917 10-1967 Owned by Les Hostick. Lease to Ian Welch and is under restoration at the Mainline Steam Heritage Trust's Parnell depot.
147 8-1917 12-1965
167 10-1917 12-1965
169 11-1917 12-1960
171 11-1917 12-1965
197 3-1918 12-1962
222 3-1918 4-1966
618 2-1915 5-1966
619 3-1915 5-1959
620 4-1915 7-1965
621 5-1915 9-1959
622 6-1915 5-1959
623 7-1915 8-1959
624 8-1915 6-1957
625 8-1915 9-1962
626 9-1915 8-1968 Transferred to South Island, 1965.
627 11-1915 4-1966
628 12-1915 2-1963
629 12-1915 4-1966
630 2-1916 10-1967 Transferred to South Island, 1965.
631 5-1916 9-1966 Transferred to South Island, 1965.
632 5-1916 8-1959
633 6-1916 8-1968 Transferred to South Island, 1964.
634 6-1916 10-1963
635 9-1916 12-1965
636 9-1916 5-1966
637 11-1916 10-1963

References

    External links

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