Berkshire Steamup
South Australian Railways '720B' class 2-8-4

Designed by Chief Mechanical Engineer Fred Shea.
Built at Islington Railway Workshops 1930-1943.

CYLINDERS (2) 22 ins x 28 ins (559mm x 711mm)
COUPLED WHEEL DIAMETER 57 ins (1,447.8mm)
TOTAL HEATING SURFACE
(including superheater) 3,726 square feet (346m²)
GRATE AREA 59.5 square feet (5.5m²)
BOILER PRESSURE 215 PSI (1,482.4 kpa)
TRACTIVE EFFORT (INCLUDING BOOSTER) 52,000 lbs (23,587kg)
TOTAL WEIGHT 232.3 tons (236 tonnes)
LENGTH OVERALL 83 feet 6 ins (25,450.8mm)

It was apparent, even after the removal of boosters, that the 710 'Mikados', unlike the 700 class, could only work over the secondary light line network with a reduced fuel/water load in their larger tenders.

The SAR therefore decided to build an even bigger, more powerful locomotive based on the earlier design but with the same route availability as the original Webb 2-8-2's. In theory this was to be achieved by increasing the boiler size and working pressure, once again fitting a booster but supporting it in a four wheel trailing truck and incorporating a large capacity tender carried on two six wheel trucks. A mechanical stoker was also included.

Seventeen 720B class locomotives were built in two batches between 1930-1943, these 'big Mikados' as they were called by just about everybody were in actual fact the only 'Berkshire' types to ever operate in Australia. Unfortunately they did not completely live up to their expectations damaging some of the lighter track work and experiencing problems at locations where only 75 foot turntables were provided.

The '720B's' therefore lived out their working lives hauling mainline freight and passenger trains with the occasional excursion into parts of the secondary network at a much reduced speed. Modifications included coal/oil firing and the fitting of skirting below the running plates and smooth all over boiler casings on the newer engines.

During the war years the 'Berkshires' ably assisted the 500, 600 and 700/710 classes in moving the vast increases in traffic but as diesels started being introduced in the early 1950's they were among the first of the 'Big Engines' to be condemned. Not one of them remains today, the last five being towed away for scrap in April 1960.