04 January 2012

Talbragar Bridge collapse!

In my posting of 11 June 2011 on Talbragar, I made mention of the partial collapse of the railway bridge at that location under the weight of 6011.  This occurred on 9 January 1967 – 45 years ago this week. 
To commemorate the anniversary of that occasion I think it is timely to add further background and detail about this rather unusual incident, using information drawn from Railway Digests published by the NSW Division of the Australian Railway Historical Society.
The use of 60 class Garratts on lightly-constructed NSW branch lines was not new.  Indeed, a known benefit of the Garratt design was its relatively light axle loading, which made this class of locomotive more suitable for use on these lines than goods locomotives with much smaller hauling capacities – such as the 50, 53 and 55 class locomotives.
While the first 60 class had commenced service in July 1952, it was a further dozen years before Garratts made an appearance on the Coonamble line.  In an article on the 1963/64 wheat season, Geoff Parkinson noted in the January 1964 Digest that 32 and 30T classes were working the Coonamble line ‘but, for the first time, 60 class Garratts have worked through to Coonamble, hauling a load of 1450 tons in the up direction’ (my emphasis added)
It is not certain that the use of Garratts on the branch line was widespread, or continued outside of that wheat season.  While the 1963/64 wheat season had produced good yields, poor rainfalls in the following two growing seasons reduced the crop considerably. 
These relatively poor seasons had an adverse impact on the allocation of these modern goods locomotives to western depots.  By March 1966, the Digest noted that many of the Garratts allocated to western NSW depots were not actually in the Division at all.  The same report noted that in early March 1966, 6005 and 6040 were transferred away from Dubbo, leaving only 6004 allocated to Dubbo.
The allocation of Garratts in the central west was relatively fluid.  In June 1966 the Digest recorded that following the transfer of 6004 from Dubbo, there was only one Garratt officially allotted to the Western Division (6015 at Parkes), though 6005 remained at Dubbo on loan from Enfield.
When the numbers of Garratts in the west increased in the second half of the 1966, it was to deal with mainline goods traffic.  The August 1966 Digest noted that 6014 had been allocated to Dubbo, joining 6005.  Together, these two engines were regularly working goods trains, sometimes double-heading with other steam locomotives, on the Dubbo-Molong-Orange line.
However it was wheat that brought the Garratts back to the branch lines of central western NSW. When commenting on the much-improved outlook for the 1966/67 wheat season, the September 1966 Digest noted that ‘the Coonamble line is the State’s best branch, having a storage capacity for over 5.5 million bushels, so steam might put on a good show out there.’
This optimism for future steam workings around Dubbo proved prescient, although a view of this type was not shared by railway officialdom.  In the very same issue of the Digest, the then Commissioner for Railways in NSW, Neil McCusker, announced that mainline services into Dubbo would be fully dieselised by the end of 1966 and that trains on all Dubbo’s branchlines would be dieselised by the end of 1967.
The 1966/67 wheat harvest was indeed bountiful.  The Digest reported that by November 1966 wheat traffic around Dubbo had reached ‘saturation point’, noting that the ‘silos are full and there are insufficient rail trucks available to cope with the required traffic’.  The Digest noted that extra trains were being run on all lines – with the Coonamble line having the rare experience of two wheat specials being operated on the Saturday night/Sunday morning of 17 and 18 November 1966.
The January 1967 Digest noted the dimensions of the ‘explosion’ in NSW’s grain harvest.  It reported that the December 1966 estimate of the NSW harvest was above 170 million bushels, which was nearly 50 per cent higher than the total storage capacity available in the NSW Grain Elevator Board’s silos (118 million bushels).  Even though the Board had created 34 additional temporary silos, this would only shelter a further 14 million bushels.  As a result, novel solutions such as the use of hangars at the local aerodromes for grain storage at Baradine and Coonamble were adopted.
The increase in railway traffic from the harvest came during the holiday peak, thereby exacerbating the strain put on the railway system.  While no doubt officialdom wanted fewer steam locomotives in service, they were forced to restore previously withdrawn locomotives to active rosters. 
By the end of 1966, Neil McCusker’s plan for dieselisation of Dubbo was in tatters.  Dubbo locomotive depot was allocated a further six steam locomotives – two 30Ts, a 32 class and three Garratts.  This brought Dubbo’s allocation of steam locomotives to 21, involving five Garratts. 
All of these locomotives were heavily involved in wheat haulage on the Coonamble line, along with two ‘special loans’.  Diesel locomotive 48101 was noted by the Digest in early 1967 as seeing ‘extensive use... on Coonamble line wheat trains, whilst the loco is loaned to Dubbo ... for the Cobar ore workings’. 
The second ‘visitor’ that wheat season was also a harbinger of the future.  The Digest also noted that 4905 had been released from Cowra workings to assist on Coonamble line, but that it ‘had made little impact on the number of 30Ts, 32s and Garratts’ engaged in operations along the branch.
While  32 classes were permitted to traverse the Coonamble line at 30 miles per hour (mph) and 48 class diesels could run at up to 45 mph, Garratts were restricted to on 20 mph.
Despite this speed limit applying to Garratts on the branch line during a very busy wheat season, the rationale for extensive use of Garratts on the Coonamble line could be justified by their increased haulage capacity.  Garratts were permitted to haul up to 1,500 tons along the branch (a later Digest quotes this limit as 1,300 tons).  This was 50 per cent higher than the limit for a single 48 class (1,000 tons) and more than double the maximum load of 695 tons for a 32 class steam loco.
The February 1967 Digest carries a detailed report of 6011’s ‘sinking’ of Talbragar Bridge. It states that wheat haulage on the ‘heavily congested’ Coonamble branch was ‘thrown into chaos’ early on Monday 9 January 1967 when the centre span of the timber trestle bridge over the Talbragar River gave way under the weight of ‘light type’ Garratt 6011 on an up wheat special.
An immediate inspection followed, and at 3.30pm that afternoon the bridge was closed to all traffic by the Way and Works Branch just as 3313 was approaching with five BWH-type wheat wagons and a guards van.  The 32 class was stopped just short of the bridge, then set back to Brocklehurst where it was joined by 601/701 two-car diesel train and 3326 on No. 6 up pickup and 4905 on an up wheat from Eumungerie.  Brocklehurst must have been a fun place to be for those responsible for safe working!
The Digest also reports that the bridge was reopened at 10:00am on Wednesday 11 January 1967, with a 5 mph speed limit.  Load tests later that day were conducted by 3308, two loaded BBW ballast wagons and a PHG guards van.
While the Digest does not mention what happened to 6011 and its train, there are details about the consequential impact on other workings as a result of the incident.  During the closure passengers were conveyed by bus from Dubbo to Brocklehurst, then onto the ‘land locked’ two car diesel set.  All trains scheduled for 10 January were cancelled, including 6005 on No. 11 wheat to Coonamble (due to depart Dubbo at 8:30am on 10 January) and  3313 for Eumungerie on No. 7 extra wheat (departing Dubbo at 10:45am).
The Digest also notes that while Garratts had been working thrice-weekly along the branch on principally nocturnal ventures, all use of this locomotive was banned.
Finally, the Digest report notes that the use of 3326 on the pickup was unusual and brought about because Dubbo’s two superheated 30Ts which used six-wheel tenders (3020T and 3144T) were out of service.  The use of the 32 was considered rare as it would need to be split at Coonamble in order to be turned for the return journey.
So, what caused the Talbragar Bridge to give way that day?  Was it simply (a) just a matter of time, (b) a result of the much increased traffic on the branch as a result of the wheat season, (c) the use of heavier locomotives and rolling stock, or (d) a combination of all three factors?
Certainly, the bridge was a veteran.  Concern about its frailty had seen a permanent speed restriction of 20 mph placed on 32 class locomotives crossing the bridge in 1963.  Still, even after 6011 had testing the bridge and found it wanting, as I have noted previously the bridge dealt with a further 14 harvests before being replaced by a welded plate girder resting on concrete supports in late 1981. 
Similarly, there is some support for the argument that the much increased freight traffic as a result of the wheat harvest had some material impact on the chances of bridge failure.
Perhaps there is more credence in impact of heavier locomotives and wagons playing a direct role in the demise of the bridge’s centre span.  Although Garratts had a relatively light loading per axle and thus a small impact on any single piece of track, the ‘light’ version of the locomotive weighed 255 tons and much of this would have been borne by the bridge’s centre span at the time of crossing.
And Garratts may not have been the only culprits in the weight factor. The introduction of 48 and 49 class locomotives – both weighing around 80 tons – exceeded the previously largest locomotive – the 32 class at around 60 tons.
It is also likely that it just wasn’t the weight of the locomotives playing a factor in the incident.  Wheat was conveyed in RU wagons which had a gross weight of 36 tons loaded and BWH wagons with a 61 gross tonnage, loaded.  Given the amount of grain to be moved along the Coonamble line, it is conceivable that the Railways used a greater number of BWH wagons in trains than in previous years.  It is also possible that some of the new WH aluminum wagons, carrying an additional 10 tons above that of a BWH, were also pressed into service on the branch.
So, it is most likely that a range of factors – ageing infrastructure, more trains, heavier locomotives and wagons – coincided to create the circumstances facing 6011 on 9 January, 45 years ago.
There is one last matter to ponder, whether a Garratt will once more tread the rails to Coonamble.  Even with the replacement of the Talbragar Bridge in 1981, until very recently there was no prospect of this ever occurring again.  However, there is now a glimmer.  Excellent progress is being made by the ACT Division of the Australian Railway Historical Society to restore 6029 to operations, and there is even a very fine blog recording the progress of its restoration
The final physical hurdle facing a rejuvenated Garratt steaming to Coonamble appears to have been overcome with the replacement of the Coalbaggie Bridge near Eumungerie and general track upgrading, which now enables heavy 81 class diesels the entire length of the branch.
Here’s hoping that 2012 or 2013 brings a Garratt once more to Coonamble!

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