Building Bridges

Where do bridges begin? More than a few of the timber truss bridges of New South Wales (NSW) owe their existence to the energy and aspiration of local people, who lobbied their parliamentarians for a crossing over a river they saw as a barrier to transport and to the progress of their region.

Each particular location depended on the onsite surveyor who worked out the specifics of alignment, flood levels and foundations for the design engineer to assess the type of bridge to recommend for the Chief Bridge Engineer’s decision. Economy in spending from the public purse was always a prime factor for the design engineer, a factor revealed for instance where abutments were built close to a river bank to reduce the length of the span required. Without today’s knowledge of hydrology and river conservation and without useful flood records, economies like this could create new problems.1

Calls for tenders were published in the NSW Government Gazette and the pages of the Sydney Morning Herald, with plans exhibited at the Chief Engineer’s Bridge Street office. Country contractors responding to the same notice in their local paper went to the courthouse or police station in the town nearest the proposed bridge site to view the plans. The bridge builders tendered to these plans with no variation of the design allowed. Unlike the covered timber truss bridges of the eastern United States where each builder added his unique and identifiable touch, the timber truss bridges of NSW are recognised by their designers, rather than their builders.

Winning tenders were published in both the NSW Government Gazette and the relevant local paper, providing a detailed though incomplete record of the bridge builders. The winning firms were required to sign a contract copy of the bridge plan along with two sureties (also known as ‘bondsmen’) who guaranteed the working capital (see Figure 6.2). Each document also had the signature of a PWD officer. As the builders contracted on individual projects, their financial backers might differ each time. Payment was not made until completion, so the swifter the build, the greater the profit for the builder and his surety investors.

Colonial timber bridge contractors were often father and sons, or brothers, with experience as bridge carpenters. With each contract the whole family was involved in the work; setting up camp at bridge sites and travelling between jobs by bullock or horse team, sometimes with as many as fifty horses. Though there were very few mechanical aids to construction, quite often the contract was executed in twelve months, with the whole family engaged in the construction.

Ten families were particularly prominent in building the timber truss bridges of NSW, each building five or more bridges. These were the Ahearns, the Taylors, the Murphys, the Farquharsons, the Fitzgeralds, the Oakes, the Jacksons, the McGills, the McPhillips and the Foords (see Figure 6.3). For bigger projects extra carpenters were taken on. Notable among these men is William Robert Maloney, foreman for three of these family firms on a total of 34 bridges built between 1901 and 1918.

The Colony’s timber export trade was underway by the 1870s when the Mann River Bridge was built, but its location on the colony’s northern rivers enabled harvesting from the still plentiful trees in the ‘Big Scrub’ (see Figure 6.4). Forested parts of the central and south coasts also afforded local timber for bridges, but in western regions both ironbark and tallowwood were scarce and milled timber was transported from the coast. A crucial part of tendering was close estimation of the cost of subcontracting to distant sawmills, as well as to foundries for metalwork.

Percy Allan reported that the contract let in 1893 for the bridge over the Murrumbidgee River at Wagga Wagga, meant timber ‘was brought from the northern rivers of the colony to Sydney, 100 miles by sea, and thence by rail, 310 miles to Wagga Wagga’.4 More than twice the distance, and presumably the cost, would have challenged tenderers for the bridge over the Murray River at Swan Hill in 1895, with the successful firm Farquharsons tackling the logistics. The whole of the timber, with the exception of a few piles, was obtained from the northern rivers of NSW, forwarded to Melbourne by sea, a distance of about 726 miles, thence to a site by rail a distance of 214 miles, for a total carriage of 940 miles.5

The bridge-building families necessarily led transient lives following the trail of government contracts and longer stays in a district must have been very welcome. When Samuel McGill and his brothers won the contract in 1896 to bridge the Hunter River at Morpeth, they were finishing the bridge over the Macintyre River at Inverell in the north of the Colony. The families made their own way 260 miles (420 km) from there to Morpeth where they were able to settle for five years, becoming valued members of that growing community. During that time some of the McGills’ team travelled south to build the 1897 Allan Truss bridge over the Wingecaribee River at Berrima. They completed the Morpeth Bridge in 1898 and won more bridge contracts in the area, including the Dunmore Bridge opened in 1899 (see Figure 6.5) and the Hinton Bridge, finished in 1901. For the latter bids, they had the considerable competitive advantage of established relations with local sawmills and foundries, as well as minimal transport and set up costs.8

The Oakes family had a long association with large timber constructions, spanning several generations. William Frank Oakes built bridges in New Zealand before emigrating to NSW where his first major project, the Smoky Cape lighthouse in 1889, was also his last. His death meant his two teenage sons, 19-year-old Walter Frank and 17-year-old Percy George, took over the work, completing the lighthouse in 1891. Walter then took on work as a surveyor and civil engineer on railway projects in Sydney, including the St Leonards to Milsons Point railway extension.

Under the company name of WF Oakes, brothers Walter (see Figure 6.7) and Percy were engaged in 1894 as foremen to SF Stokes, contractor for the erection of Hampden Bridge at Wagga Wagga. The first example of Percy Allan’s new lightweight truss design, this was a major undertaking, with its longest span 110 feet (33.5 m) and deck area 3,165 square feet (294 m2). Under Chief Engineer for Roads and Bridges Robert Hickson’s 1891 reorganisation, the district road superintendents were now titled resident engineers. However, despite this onsite supervision, the bridge’s completion date of 5 April 1895 was not met. Fears grew that if the town’s 1862 ‘Company Bridge’ could not survive the winter, the Murrumbidgee would cut off traffic and commerce, with the electorate’s vociferous complaints aired in the Legislative Assembly.9

Hickson and Divisional Engineer Ernest de Burgh travelled to Wagga Wagga to assess the problems firsthand and find a way to accelerate the work (see Figure 6.6). The intervention worked and two months later the local press were able to anticipate an opening date and were quick to congratulate the contractor ‘on having been able to successfully overcome the difficulties of flood, stream and weather which he had to combat’. The actual opening ceremony was still four months away, celebrated with elation on 12 November 1895.10

The firm’s two de Burgh Truss bridges were built in 1902 in the Hunter River region, over Black Creek at Rothbury and over Webbers Creek on the Gresford to Singleton Road (see Figure 6.9).

The families seem to have been based in the area at this time, with two of their Dare Truss bridges, over the Macdonald River at Bendemeer and over the Williams River at Dungog, completed in 1905.12 Among their other Dare Truss bridges were two on the Richmond River in the state’s northeast, Colemans Bridge over Leycester Creek at Lismore in 1908 and the Bean Tree Bridge near Wiangaree in 1927. These marked nearly forty years as builders for the Oakes brothers (see Figure 6.10).

Designed by Percy Allan, the bridge at Swan Hill was the first of its type, with a lift span and Allan Truss timber spans. The contract was let to the Farquharsons in 1895. They ordered the metal components from a Melbourne firm and all the timber from Wyong sawmills was shipped through Melbourne and sent from there by rail. The firm had just completed the Tocumwal Bridge and was able to use the same plant, but the major saving was the new design that halved the cost of both labour and materials with

the more economical design of lift, the substitution of timber for iron side spans, and the securing of foundations for the two river piers at Swan Hill at a lesser depth than at Tocumwal.13

Farquharsons built the Union Bridge at Albury in 1898 and the Cobram Bridge in 1902. The firm took just over twelve months to complete the Howlong Bridge in 1908 with the Dare Truss, ‘the latest type used by the PWD, with top chords and braces of Ironbark, the lower chords steel and the suspension rods wrought iron’.14

It was no accident that the bridge between Barham and Koondrook was the exception to Farquharsons’ Murray River full set of bridges. The very experienced Farquharsons’ bid of £12,000 was the second lowest of the six tenders submitted, making Monash & Anderson’s winning bid of £10,345 seem more risky than competitive, hinting at either desperation or determination to break the older firm’s dominance. Unlike the Farquharson brothers, John Monash and JT Noble Anderson were both graduate engineers. The firm had successfully completed the timber truss Tambo Bridge at Bruthen, Victoria in 1899, but their completion date of 30 April 1904 for the Murray bridge was overrun.

Their problems compounded, with difficulties in keeping a workforce together following prolonged delays in delivery of the 170 tonnes of ironwork ordered from Ballarat’s Eureka Ironworks. The subsequent loss on the contract might have been the reason Monash never tendered for bridge building again, though this was more likely due to the financial collapse of the business after other bridge losses, most dramatically the collapse of their Monier bridge at Bendigo and Anderson’s departure for New Zealand. John Monash went on to make his fortune with the firm’s possession of the Monier patent for reinforced concrete, and then had a distinguished military career. William Farquharson remained a bridge builder to the last. He died in 1925, aged 85 in the midst of building the new Allan Truss bridge over Goobang Creek that replaced Condobolin’s 1880 Bennett Truss bridge. His bridge was replaced in 2008, just short of the long lifespan of its builder.15

Once numbered in their hundreds, timber truss bridges are now a rarity. The early bridges were built with hand tools, the broad axe, the adze, the hand auger and chalk line (see Figure 6.12). The broad axe made a hewn log ready, with the adze the primary tool for cutting and trimming a square edge on members so they would slot neatly into place to form the trusses. As these were hardwoods, blackbutt or ironbark, the bridge carpenter worked with a lot of effort and skill in making trusses.

Pile-driving was dangerous but work inside the pressurised caissons was even more so, with the only safety measure a signalman or ‘banksman’ posted at the top of the caisson to alert the engine-driver to any problem for those inside. At many sites contractors worked men night and day, especially if there had been delays. Only when workers at the SF Stokes’ bridge site at Wagga Wagga complained of the danger in winter 1894 was a banksman posted, and then only for the night time shift. When the local MLA visited the site he explained to a reporter:

Some locks are made with the exhaust taps on the outside (a very objectionable practice), and in these it is absolutely necessary to have a man outside, for those working in the lock cannot help themselves, or get out without his assistance. In such locks, the men inside give the signal, and the banksman allows the air to escape, when the door can be opened. As those outside cannot know the effect the reduction of the pressure is having upon those in the lock, and as a careless foreman may insist upon the taps being turned full, to shorten the time occupied in lowering the pressure, this is dangerous to the men.

In other locks the taps are inside, and are controlled by the men themselves, who if anything goes wrong have it in their power to open the lock and come out, and also can regulate the pressure to suit themselves; they are thus absolutely independent of a signalman.

The airlock in use at the Wagga Wagga bridge works was the latter type and by summer when the men had won their case for a banksman on the night shift – and increased wages for these hours – they agreed the extra man was not necessary in daytime.21 Four years later, builder Samuel McGill devised an improved airlock for the caissons used in construction of Dunmore Bridge on the Paterson River, patenting the design in Victoria as well as NSW.22

Work inside the caissons held other dangers too. A new recruit at the Farquharsons’ Cobram bridge site was struck by a bucket falling from the top; the same labourer some weeks later used his shovel to shield his head when a pick plummeted down the cylinder he was working inside. As he had no serious injury and such incidents were not uncommon, the only reason for this record was that just four days after the second incident, the same young man drowned in the Murray River, struck by the barrow of sand that fell with him from a temporary bridge.23

Bracing between the piers usually was a plate diaphragm with an oval ‘window’ (see Figure 6.17 above) and while bracing with iron stiffeners was less common, several examples exist (See Figure 6.19).

The approach spans of the bridges were relatively straightforward constructions over land. ‘Gin’ (engine) poles were used for erection because of the ease of rigging, moving and operating. They comprised a strong pole with four ropes and hoisting tackle fastened at the top end and were used for raising or moving heavy weights up to 50 feet in the air. Gin poles helped put in place a headstock on top of piles (see Figure 6.20) and girder logs on top of headstocks (see Figure 6.21) to build up the bridge deck. For smaller jobs, piling derricks could double as cranes.

Ironwork needed for the bridges included cast-iron shoes (also known as ‘chairs’) and rods, bolts, washers and angle blocks. These were generally ordered through a foundry which fabricated the items to patterns provided by Public Works. Large complex structures needed more elaborate planning for the quantities of ironwork required. For the Hampden Bridge at Wagga Wagga, Allan recorded that:

all the wrought iron bars are rolled from scrap at the Lithgow Ironworks, 97 miles distant by rail from the Atlas Company’s works in Sydney, where all the ironwork was manufactured, being then forwarded by rail to Wagga Wagga, a distance of 310 miles.24

Much like home assembly of modern flat-pack furniture, the first step in assembling the trusses was checking off the list of timber and iron parts. The skilled crews next framed the trusses on the ground for trial assembly to ensure timber sizing and tightness of fit. The arrangement of connections on the Bennett and McDonald trusses meant these were built in situ, on the bridge over the water. Grey ironbark has a weight of 75 pounds per cubic foot when green, reducing to 70 pounds per cubic foot when seasoned (from 1200 to 1100 kilograms per cubic metre, so a single top chord member for a 90 feet (27.4 m) Bennett Truss weighed over 3 tonnes. The lifting of these top chord timbers (yet to take place in Figure 6.22) was obviously a difficult and skilled procedure.

The small numbers of timber truss bridges constructed by the NSW Railways were also built by trial assembly before raising the pieces into position:

It is easy to see the advantage of the Allan Truss with connections arranged so the truss could be assembled first and then launched into position. Sometimes though, the depth of the trusses dictated the in situ method even with the Allan Truss, as at the McGills’ bridgeworks on the Macintyre River (see Figure 6.23).

Another example was with timber truss spans as components of lift span bridges. The lift span, comprising cast iron piers, a tower and movable deck, was built first and the connecting spans second (see Figure 6.24).

As the fabrication and assembly of the Pyrmont Bridge over Sydney’s Darling Harbour in 1902 was well documented, it is a guide to many of the steps involved. Each of the ironbark Allan trusses spanned 82 feet and weighed 15 tonnes and these were assembled on the wharf, close to the bridge site and to the designer’s attention (see Figures 6.25 & 6.26).

At Pyrmont, after fabrication the trusses were hoisted about thirty feet by pile-driving machines mounted on trolleys or barges, then towed to their sites and placed on the piers. All the trusses were lifted and placed in position in seven hours, with half a pier and two spans with roadway gates completed for traffic in just eight days (see Figure 6.27).

This process was also used with the Dare Truss, for example in building the first Commonwealth Avenue Bridge over the Molonglo River in Canberra in 1925 (see Figure 6.28).

In the more direct method allowed by Allan’s design, trusses were erected on the approaches, then each truss was launched individually using a ‘gin’ pole in the centre of the span, and a second pole on the far abutment, moved with hand-operated winches. Figures 6.29 & 6.30 demonstrate two stages of this method of launching a truss.

As each pair of trusses was installed, the cross girders were placed to carry the deck and the work of installing the deck planks, kerbs, tar coating, and fencing carried on (see Figure 6.31).

The bridge over Palmers Channel on the north coast of NSW (see Figure 6.31) was welcomed as ‘sister’ to the 1911 Dare Truss Sportsmans Creek bridge upstream at Lawrence. Locals cared less about the design distinction than the utility of their new bridge and the historic touch given its rubble abutments, topped with dressed stone from ‘the old Ramornie dancing hall [that] did duty for some fifty years.’27

The timber truss bridges can be read as a record of their builders, as well as of their designers, as novelist Kate Grenville suggested in The Idea of Perfection:

the men who had built this bridge had even gone to the trouble of countersinking the bolt-heads, pecking out a tidy hole to get it all as tight as a piece of cabinetwork. It was tricky, working hardwood like that, but they had thought it worth doing. “True” was the word carpenters used. It was as if they had thought there was something moral about it.28