Pyrmont Bridge

Pyrmont Bridge is one of the world’s oldest surviving electrically operated swingspan bridges. It cost £112,500 to build, and opened in 1902, replacing the first bridge (that had been carrying traffic since 1857), allowing tall vessels to access southern Darling Harbour.

Pyrmont Bridge is the best known of 583 designed by the engineer Percy Allen. It has a steel truss swingspan with cheaper ironbark timber truss approach spans.

Almost all previous swingspan bridges were operated by winches, steam or hydraulic power. In this case Ultimo Power House was nearby, and modified tram motors drove the swingspan. This innovation won acclaim as a marvel of modern engineering at the international conference of the Institution of Civil Engineers (London) in 1907.

As container ships came to dominate trade, freight moved to Botany Bay, the railway goods yards closed and in 1981 Pyrmont Bridge closed to traffic. When Darling Harbour was redeveloped, the swingspan was restored and a monorail built. The monorail was dismantled in 2013 but the bridge still opens for demonstrations on weekends and public holidays, and whenever a tall vessel needs to pass through.

The swingspan has opened more than 600,000 times. An Institution of Engineers Australia commemorative plaque is at the bridge’s west end, and an inscription in the stonework at the eastern end recognises Percy Allan.

Timeline
1857 – First Pyrmont Bridge opens on 17 March
1899 – Construction starts on new bridge on 6 September
1902 – Swingspan bridge opens on 28 June
1981 – Pyrmont Bridge closes to all pedestrian and vehicular traffic on 7 August
1984 – Southern Darling Harbour (Cockle Bay) shipping and railway terminals close. Plans are launched to redevelop Darling Harbour
1988 – Darling Harbour precinct opens to the public. Pyrmont Bridge reopens to pedestrians

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Facts and Figures

  • Length: 369 metres
  • The bridge cost £112,500 to build
  • The bridge is made up of 14 spans: Australian ironbark is used on 12 spans, while the two central spans, which swing, are made ofm steel
  • The swingspan weighs 1,000 tonnes and is supported on a base of concrete and local sandstone filled with mass concrete: it weighs 6,800 tonnes. It is 13 metres in diameter and 19 metres deep. The water is 6.5 metres deep and the base extends a further 10 metres below the sea floor
  • Pyrmont Bridge takes 60 seconds to open. It must be opened for vessels more than 7 metres high
  • Vessels up to 21.5 metres wide can pass through the open channel
  • Pyrmont Bridge is driven by the original two 50 Hp 600 volt DC General Electric type 57 electric motors. Manual drum-type General Electric tramway controllers drive the motors for the swingspan and gates
  • Power was drawn from Ultimo Power House (now the Powerhouse Museum)
  • As a young engineer, J.J.C. Bradfield (who designed the Sydney Harbour Bridge) helped design the sandstone abutment walls at each end of Pyrmont Bridge
  • More than 5 million pedestrians cross the bridge each year