4D11½ Abt Class

Total Number of Engines Built 2
First Engine Built 1898
Last Engine Built 1898
First Engine Written Off 1916
Last Engine Written Off 1922


Discovery of gold at Mount Morgan in the Dawson Valley resulted in construction of a railway between Rockhampton and the mining town. The 24 mile route included the steep Razorback Range which was negotiated with a 1 mile 35 chain long rack section with 1 in 16 grades. These two engines were introduced to assist working trains on the rack section. The boilers originally had a working pressure of 175psi but this was later reduced to 150psi to assist adhesion.

All trains traversing the rack section in either direction had a rack engine attached in addition to the train engine. Ascending trains were banked in the rear and the rack engine was attached in front of descending trains. Alone, they could haul only 50 tons up or down the rack section but if assisting a B13 or B15 Class then the train load was 80 tons. The engines were attached to Mount Morgan and their working was restricted between there and the bottom of the rack section, a total distance of 4 miles.

The engines had outside frames and closely resembled the Mount Lyell engines in Tasmania . They were fitted with both Westinghouse and Le Chatelier counter pressure brakes. Their usage decreased after 1900 following the introduction of the larger more powerful 6D13½ Abt Class. N°340 spent its last days as washout engine at Mount Morgan .


Dubs – Dubs & Co. Glasgow

Technical Details
Wheel Arrangement0-4-2T0-4-2T
Cylinders (diameter x stroke) ins.11½ X 20
11½ x 15½ rack
11½ X 20
11½ x 15½ rack
Coupled Wheels diameter ins.3636
Boiler Pressure - psi.175150
Grate Area - sq. ft.11.311.3
Weight - Adhesive20.120.1
Weight - Engine26.8527.2
Weight - Tender--
Coal Capacity - tons0.751.0
Water Capacity - gallons600600
Tractive Effort - lbs. (85%)Adhesion 10,285
Rack 12,720
Adhesion 8,815
Rack 10,990
Factor of Adhesion4.375.11
Valve GearAd. - Walschaert
Rack - Hackworth
Ad. - Walschaert
Rack - Hackworth
Class Roster