Queensland Railways class B18¼
The B18¼ was a class of low-drivered Pacifics designed for mixed traffic. While the B in the designation stood for three driving axles, the number represented the cylinder diameter in inches. The stroke of the cylinders was 24 inches and the drivers had a diameter of four feet and three inches. They had a grate of 25 square feet and were superheated from the start.
North Ipswich Workshops built the first batch in 1926 and soon also Walkers Limited produced this class. A total of 83 were completed by 1947, of which 24 had come from Walkers. When the more modern, but otherwise similar BB18¼ was introduced in 1950, the B18¼ was relegated to other lines. All class members were withdrawn between 1967 and 1970. Today No. 771 is on display at the Queensland Museum Rail Workshops.
Technical data
General
- Built
- 1926-1947
- Manufacturers
- North Ipswich, Walkers
- Wheel arrangement
- 4-6-2 (Pacific)
- Gauge
- 1,067 mm (Cape gauge)
Dimensions and weights
- Service weight
- 57.2 t
- Total weight
- 94.7 t
- Water capacity
- 13,639 l
- Fuel capacity
- 8.1 t (coal)
Boiler
- Grate area
- 2.323 m²
- Firebox surface
- 9.848 m²
- Tube heating surface
- 140.377 m²
- Evaporative heating surface
- 150.225 m²
- Superheater surface
- 31.587 m²
- Total heating surface
- 181.8 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
- Optimal speed
- 50 km/h
- Power-to-weight ratio
- 14.3 kW/t
- Heating Surface Equivalent
- 262.6 m²
- Cylinder volume/HSE
- 1 : 783.43
- Tractive force/Heating surface
- 1 : 11.57
- Grate area/Heating surface
- 1 : 78.27
- Firebox/Tube surface
- 1 : 14.25
- Total/Superheater
- 1 : 4.76
