The New Zealand Railways Magazine, Volume 7, Issue 7 (December 1, 1932)
The New Locomotives
The New Locomotives.
The Department decided gradually to replace obsolete locomotives with locomotives embodying all modern development in design, and at the same time to develop such power in each unit as would reduce the present necessity for “double-heading” many of the existing services. Such a development could be given effect to, as the bridges on the main line which previously had limited the permissible axle-loading had, during the past few years, been replaced with structures permitting heavier locomotives to be used.
The mechanical designing group of the Department was, therefore, put to the task of developing a type of locomotive which would meet the conditions laid down, and this group has been actively engaged on this work for some months past. The work required is of a highly-specialised and technical nature, and every portion of the locomotive has to be drawn out in detail so that the shops, can manufacture and erect the parts, required without any hitch.
The designers were compelled to adopt the arrangement of eight-coupled driving wheels in order to keep within the permissible maximum loading for one wheel set, but the distribution of weight has been so made that, whilst the required adhesion is obtained for the power developed, the heavy weight of the locomotive will not limit its use to just a certain area, but will enable it to operate over the whole of the main track in the North Island. The power developed without the “booster” is slightly more than 50 per cent, greater than that obtained from the standard general purpose locomotive (plass “Ab”) now used to operate the Department's main liner services.