The Harbour Bridge and Big Shipping.
The Sydney Mail January 9, 1924
IN developing Empire ports maritime efficiency must not be hampered by the headway under bridges. How Sydney Harbour Bridge comes into consideration from this point of view involves interesting calculations. In 1900 there were 22,369,358 tons of merchant shipping afloat propelled by steam and 6,598,000 tons under sail, a total of 28,957,358 tons, distributed over 27,840 vessels. In 1923 there were 62,335,373 tons propelled by steam, and 2,830,865 tons under sail, or a total of 65,166,238 tons, distributed over 33,507 vessels.
Sailing tonnage now forms a very small and practically negligible portion of the world’s merchant shipping.
The interest of present-day shippers centres in steamers and motor vessels, particularly in those built of steel and iron. The real test of the strength of the various merchant fleets of the world is to be found in the statistics of sea going steel and iron vessels.
From the figures quoted it will be seen that from the beginning of the present century the shipping tonnage of the world has more than doubled.
The number of merchant ships has not greatly increased during this period, but the average size is far larger.
During the last ten years there has been a large increase in the use of oil instead of coal in the sea-carrying trade of the world, apart from the progress which the movement has already made in the great war fleets, the British Navy now depending almost exclusively on liquid fuel.
THE future lies with the oil-burning ship, which enjoys many economic and other advantages, including cleanliness. Of the 3049 steamers fitted for burning oil fuel, only 601, representing 3,792,676 tons are registered in Great Britain and Ireland, whilst 1709 steamers of 8,709,776 tons are registered in the United States of America.
Similar liners to those now engaged in the trans-Atlantic trades will at no very distant date be seen in Sydney Harbour, and it is the height required for the funnels and wireless aerials of such vessels which determines the headway to be provided under the bridge across Sydney Harbour.
The Olympic has funnels 137 feet and the Majestic 156 feet above load waterline. The wireless aerials are much higher than this; those on the Olympic are carried 195 feet above the load waterline, and those on the Majestic 216 feet.
There is a limit, however, to which the deck of the bridge can be carried above high-water level, and the most that can be done is to provide the maximum headway permissible under the governing factors of engineering and financial requirements. Within certain limit masts can be made telescopic, and for the headway under the Sydney Harbour Bridge it was not considered necessary to provide full clearance for the aerials of such liners as the Olympic or the Majestic.
The bridges erected across the east River, New York, U.S.A. all have a clear headway of 135 feet above high-water mark, and the same height has been provided for the Philadelphia-Camden bridge, now in course of erection across the Delaware River.
The Forth Bridge, over the Firth of Forth, Scotland, and also the Quebec Bridge, over the St. Lawrence River, have headways of 150 feet at high-water mark. The range of tide at Quebec, however, is 20 feet, at the Forth Bridge 20 feet, whilst in Sydney Harbour mean high water is only 5.04 feet above mean low water.
The shipping traffic under any of the bridges mentioned will not develop to the extent, nor be as important as that which will pass under the Sydney Harbour Bridge in future years.
TO make a reasonable provision for those future developments in the shipping business of Australia’s greatest seaport a headway of 170 feet at high water was decided upon. This height will allow mail steamers up to 20,000 gross tonnage to pass under the bridge without the necessity for telescopic masts, and will also permit the funnels of the largest vessels afloat to-day to pass under the bridge deck, and allow a reasonable margin for future development. In the future larger vessels than the present leviathans will assuredly be constructed, and though the internal combustion engine vessel may replace coal and oil burning steamers – thus rendering a less height funnel necessary – consideration of larger sized vessels of the future demands that the headway shall be kept as great as is reasonably practicable. To-day Sydney’s shipping is exceeded by only four ports in the United Kingdom – London, Liverpool, the Tyne, and Cardiff; withing 50 years Sydney will probably be the premier port of the Empire, and it is essential that the greatest headway practicable shall be provided for, and even with a clear headway of 170 feet at high water the largest main and passenger steamers which will ultimately enter Sydney Harbour will require to be provided with telescopic masts.
As the bridge will return a handsome profit from railway passenger traffic at the outset, this added cost for the 20 feet additional headway is not excessive when it is considered that this increased height will provide uninterrupted headway for probably 98 per cent. of the steamers trading to Sydney in the future.
BEFORE concluding it will be interesting to make mention of the new mail steamers which will be trading to Sydney in the new year. The P. and O. Company have bult the Mooltan and the Maloja, each with a gross tonnage of 20,700 tons, 623ft 6in long, 73ft 5in beam, and loaded draught 31ft 6in. The height of the funnels above light load waterline will be 111ft 6in; of the masts 162ft; and the wireless aerials, 152ft.
The Orient Company expect to have the Orama and the Oronsay on the run to Sydney next year, each having a gross tonnage of 20,000 tons, length 657ft, bean 75ft, draught 29ft, height of funnels above light load line 124ft, of masts 164ft, and wireless aerials 152ft.
The Union Company’s new motor ship of 20,000 tons will also be in commission next year, length 600ft, beam 72ft, draught 27ft 6in, height of funnels above light load line 104ft, only 20ft less in height than the funnels of the steamers Orama and Oronsay, whilst the height of the motor ship’s masts will be 159ft above light load line. She will be, if not the largest, one of the largest motor ships in the world.
The advent of these new liners presage an even greater expansion in Sydney’s future than in her past, and larger and yet larger ships will come into the world’s loveliest harbour.
