In 1950, when the N.Z.R. had already decided to obtain diesel-electric locomotives for the North Island Main Trunk line, sixteen oil-fired "Ja" class engines were ordered from the North British Locomotive Company, Glasgow. The locomotives were intended as a stop-gap at a time when secondary main line power was proving inadequate.
Apart from the fact that they were oil-fired, the Scottish engines differed little from their Hillside Ja's. An important variation, however, was the fitting of French T.I.A. "blow-down" equipment to reduce boiler scale and to enable sludge to be ejected.
The locomotives were originally assigned to important duties on the Auckland-Paekakariki section, and were also used on the Northland and Hawke's Bay routes. Towards the end of their service they were employed almost exclusively in the Auckland district, where their duties included the haulage of Main Trunk expresses between Auckland and Taumarunui.
If the North British locomotives possessed the potential for high-class performances similar to those of the Hillside engines, they lacked the opportunities. Even the most favourable stretches of the Auckland-Frankton main line and were not conducive to spirited running of the kind traditional on the Canterbury Plains.
Nevertheless, they proved capable of running at mile-a-minute speeds on level track with medium-weight expresses.
Ja1275 was retired in March 1968 and was purchased by Les Hostick. It was put into storage at Te Awamutu Railway Museum until 1994 when it was leased to Mainline Steam. It was moved to our Parnell depot where it has undergone an extensive overhaul returning to service in October 2004.
Cavalcade of New Zealand Locomotives. A.N. Palmer and W.W. Stewart