McDonald Truss Bridges

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The second type of timber truss bridges are the McDonald truss bridges.  John McDonald was the Engineer for Bridges for the Public Works Department of NSW. He made some major improvements to the Old PWD truss which reduced maintenance costs and increased the strength of the truss. McDonald truss bridges were built from 1880-1902.  They looked similar to the Old PWD truss. The main differences were the elimination of the double thickness top chord, the addition of splayed end chords  and the use of iron cradles for the tension rods at the ends of the top chord. The splayed ends provided better support and better distribution of the forces transmitted to and from the top chord.  The iron cradles for the tension rods removed the need to drill holes in the ends of the top chord.
In spite of these improvements, the truss still retained the single thick timber beam for the top chord.

McDonald truss bridges have a flattened appearance compared to the more common Allan and Dare trusses.

Statistics
Number built:    91
Number remaining:    5
Number to be preserved:    3

Bridge Name
Date Built
# of Spans
Location
Waterway Name
Status
To be preserved?
Crankies Plains
1902
2
Bombala
Coolumbooka River
Not rebuilt
No
Galston
1902
1
Galston Gorge
Tunks Creek
Original
Yes
Junction
1895
3
Tumut
Tumut River
Rebuilt
Yes
Five Day Creek
1902
1
Armidale-Kempsey Rd
Five Day Creek
Out of use
No
McKanes Falls
1893
2
Lithgow
Coxs River
Not rebuilt
Yes

Crankies Plains Bridge

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This bridge is located on the Bombala-Cathcart Road about 2km from Bombala.  It is a two span bridge built in 1902and crosses the Coolumbooka River.  In my opinion, it is the best looking of the McDonald trusses and is located in a beautiful setting.  Part of the reason of its good looks is that it has very little weather shielding installed, and none on the sloping end chords. It is unfortunately not on the list of bridges to be preserved.  This bridge has not been upgraded with modern materials.

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View of the bridge.

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This bridge is in an scenic, open area.

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View from the north side. This bridge still has the original style deck planking.

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View of the truss.

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View of the bridge from the south side.

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Closer view from the south side.

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View of the south abutment with bracing.

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View from the south side. This view shows the splayed end chords.

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View from the north side.  Note how the road narrows over the truss spans.



McKanes Falls Bridge

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This bridge is a two span bridge located on McKanes Falls Road about 5km south of Lithgow. It was built in 1893 and crosses the Coxs River.  It is one of the few timber truss bridges in NSW that are not painted white.  The centre pier was originally constructed of masonry similar with the abutments but was shifted downstream by flood in the early 1980s. It was replaced with a concrete pier.  The bridge is going to be preserved and will eventually be restored and upgraded.

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View of the bridge.

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View from the north side.

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Side view of the truss span.

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View of the splayed end chords.

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View of the underside. This view shows the bottom chord, composed of four separate beams (flitches) bolted together.

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View of the truss showing the iron rod and cradles.

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View of the bridge from the south side.

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View of the bridge from the north side.

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View of the bridge and river.



Galston Bridge

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Galston Bridge  is a single span bridge located on Galston Road. It was built in 1893 and crosses Tunks Creek in Galston Gorge, east of Hornsby. It is the shortest of all the remaining timber truss bridges in NSW. This bridge is going to be preserved without upgrading with modern materials as it does not have to carry heavy loads due to the road having a load limit.

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View of the bridge from the creek bed.

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View of the bridge from a convenient hill.

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View of the bridge.

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View of the underside. The tension rod cradle is visible on the lower left.

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Sign for the bridge. Several of the preserved bridges have a sign such as this.

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View of the bridge abutment.



Junction Bridge

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Junction Bridge is a three span bridge located on Tumut Plains Road, about 4km east of Tumut. It crosses the Tumut River and was built in 1895.  The bridge has been completely restored and strengthened.  According to the RMS (Roads and Maritime Services) here, this involved replacing one of the bottom chord flitches with a steel flitch, replacing the crossbeams with steel, replacing the approach spans with concrete, replacing the railing and adding more stay braces (the pieces of steel angle holding the trusses upright on the outside of the bridge). The result is very good.  The only thing I don't like is the new railing.  While made to resemble the original railing, it is still very obviously not original.  The bridge was also painted white, instead of the two tone green and brown it used to be.

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View of the bridge from the east side.

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View of the bridge deck.

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Close up of the one of the trusses.

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View of the bridge and sign.

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Close up of the iron cradle.

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View of the bridge from the east side.

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View of the truss and new railing.

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View of the bridge from the west side.


Bridge Videos

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Driving view of the four McDonald truss bridges still open to traffic.