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The reference for locomotives and railcars

Queensland Railways class BB18¼

Australia 1950 55 produced
Bearq07 CC BY-SA 4.0

The BB18¼ was a light 4-6-2 “Pacific” for mixed traffic that was ordered by the Queensland Railways after World War II from Vulcan Foundry in England. While the B in the designation stood for three coupled axles and the 18¼ denoted the cylinder diameter in inches, the second B was added to distinguish it from the earlier class B18¼ Pacific. The first 35 were built by Vulcan Foundry in 1950 and 1951. 20 more followed from Walkers Limited between 1955 and 1958. No. 1089 was the last steam locomotive placed into mainline service by any Australian railway company.

They had similar tasks as their predecessors, what included goods, suburban and long distance passenger traffic. Although they had a fairly low axle load, some bridges in the QR network were reinforced in the fifties to further increase their route availability. While long distance passenger services dominated their tasks in the first years, these were later taken over by diesel locomotives. Six have been preserved and 1037 is still in working condition. It is being owned by DownsSteam in Toowoomba.

Technical data

General

Built
1950-1951, 1955-1958
Manufacturers
Vulcan Foundry, Walkers
Wheel arrangement
4-6-2 (Pacific)
Gauge
1,067 mm (Cape gauge)

Dimensions and weights

Length
18.34 m
Wheelbase
8.28 m
Total wheelbase
14.16 m
Service mass
58.9 t
Adhesion mass
36.4 t
Total mass
102.8 t
Rigid wheelbase
3.35 m
Axle load
12.2 t
Water capacity
15,910 l
Fuel capacity
10.5 t (coal)

Boiler

Grate area
2.323 m²
Firebox surface
9.848 m²
Tube heating surface
131.737 m²
Evaporative heating surface
141.584 m²
Superheater surface
31.03 m²
Total heating surface
172.6 m²

Power plant

Driver diameter
1,295 mm
Boiler pressure
11.7 bar
Expansion type
simple expansion
Cylinders
two, 464 x 610 mm

Power

Power source
steam
Estimated power
820 kW (1,115 PS)
Starting effort
100.7 kN

Calculated values

Factor of adhesion
1 : 3.55
Optimal speed
50 km/h
Power-to-weight ratio
13.9 kW/t
Heating Surface Equivalent
252.9 m²
Cylinder volume/HSE
1 : 813.64
Adhesive weight/Total
1 : 1.62
Tractive force/Heating surface
1 : 12.19
Grate area/Heating surface
1 : 74.31
Firebox/Tube surface
1 : 13.38
Total/Superheater
1 : 4.56
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