NZR BA class

NZR BA class
BA 552 at Mainline Steam's Parnell depot
Power type	Steam
Builder	NZR Addington Workshops
Build date	1911 - 1913
Configuration	4-8-0
Gauge	3 ft 6 in (1,067 mm) Cape gauge
Driver diameter	42.5 in (1,080 mm)
Length	52 ft 3 in (15.93 m)
Weight on drivers	32.3 long tons (32.8 t)
Locomotive weight	43.9 long tons (44.6 t)
Tender weight	25.5 long tons (25.9 t)
Locomotive & tender combined weight	69.4 long tons (70.5 t)
Fuel type	Coal
Fuel capacity	4.0 long tons (4.1 t)
Water capacity	1,700 imp gal (7,700 l; 2,000 US gal)
Boiler pressure	175 psi (1,210 kPa) original 200 psi (1,400 kPa) rebuild
Firegrate area	16.7 square feet (1.55 m2) original 26.4 square feet (2.45 m2) rebuild
Superheater area	206 square feet (19.1 m2)
Cylinders	Two
Cylinder size	16 in × 22 in (410 mm × 560 mm)
Top speed	30 mph (48 km/h)
Tractive effort	18,550 lbf (82,500 N) original 21,200 lbf (94,000 N) rebuild
Number in class	10
Number	148, 497 - 500, 551 - 555
Locale	Otago and Southland
First run	November 1911
Last run	June 1969
Preserved	One (BA 552)
Disposition	Withdrawn 1 preserved

The B^A class was a class of steam locomotive built by the New Zealand Railways Department (NZR) for use on New Zealand's national rail network. The first B^A entered service in November 1911, with the last of the 11 class members introduced on 14 May 1913.

Construction and later enhancements

In design and appearance the B^A class was very similar to the B class of 1899-1903, but superheated and with a smaller firebox. They were designed primarily for use on freight trains in the South Island, and were capable of hauling a load of goods at speeds up to 30 mph.

In March 1928, B^A 552 was modified to have a wider firebox, and later that year the same work was done on B^A 498. It was almost two decades before the alterations were performed on any other members of the class: B^A 553 was done in May 1948, B^A 148 the next month, and fifth and last was B^A 499 in November 1949. The other B^A locomotives were left with unmodified fireboxes.

The upgraded engines were capable of producing more power: their boiler pressure was raised to 200 psi and they could generate 21,200 lbf. On straight, flat track, they could haul 700-750 tons, and on the arduous steep section of the Main South Line north of Dunedin they were capable of hauling 270 tons, 50 tons more than the five locomotives that were not upgraded.

In their later years, eight of the ten B^A locomotives were modified to perform shunting duties. This included an all-weather cab fixture on the tender to provide shelter for crews.

Operation

The locomotives occasionally hauled suburban passenger trains in Dunedin, but were primarily freight locomotives. They operated in Otago and Southland on the Main South Line and the many branch lines that fanned from it in the first half of the 20th century. The enhanced locomotives with larger fireboxes were often seen on the Otago Central Railway.

In later years, more powerful steam locomotives and then diesel-electrics were introduced and the B^A class was largely confined to heavy shunting duties and short-haul freight services in and around Dunedin. Some members of the class were transferred in the 1950s to the West Coast, where they operated for a few years on both shunting and longer distance services.

Withdrawal and preservation

The B^A class lasted into the 1960s, late in the days of steam; the era ended when a member of the J^A class hauled the last regularly scheduled steam-hauled revenue service on 26 October 1971. The first B^A to exit service was B^A 554 in May 1963, and through the mid-1960s, the class was progressively withdrawn. At the start of 1969, only one was left in service, B^A 552.

B^A 552 hauled railfan excursions in the mid-1960s, and in 1968 and into 1969 it was retained by NZR on standby, should extra motive power be required. In June 1969 the decision was made to withdraw the locomotive, and pressure came from railfans to retain it for preservation. It was used to haul an excursion in November of that year, and in September 1970 it was transferred to the North Island, in the process becoming the only member of the B^A class to leave the South Island. Although steam had technically ceased in the North Island, B^A 552 and A 423 were used on a steam delivery trip between Palmerston North and Frankton, with B^A 552 leading for much of the journey. It was then transferred to private ownership in Te Awamutu, where it was held in on static display, and is today based at Mainline Steam's Auckland depot. It has been refurbished and is in full running order, capable of hauling mainline excursion trains.

External links

• Mainline Steam's page on B^A 552
• New Zealand Railways Steam Locomotives - Class B^A