Following my earlier post on the topic, Ian Phemister (http://iansmuswellbrookmerriwa.blogspot.com.au/) kindly provided me with a copy of his photos on the same subject taken from his extensive collection of information on the Merriwa line. It is a goldmine of detail. The first thing I noticed was that the shorter of the timber pier sets only has three piers rather than the four that I had constructed (based on old standard drawings). This has now been corrected.
From Ian's information, it is also interesting to note that an extra pier set has been added to reduce the span between the larger timber pier set and the abutment. I presume this occurred sometime after 1970 as it certainly not there in a 1970 photo of 3090 taken on the bridge.
Many thanks Ian. Your assistance is greatly appreciated.
To start the fabrication of the components, I fixed a length of track upside down to a strip of ply and then glued the steel and timber beams to the underside of the track. The main concrete piers were shaped from styrofoam, coated a mix of coloured tile grout and 50/50 PVA/water, and weathered further with soft pastels and isocol alcohol. Looking at the photo below, I may need to revisit the right hand pier to lighten it up somewhat.
The concrete piers were then glued to underside of the steel beams, and then a further strip of ply was glued to the underside of the piers thus creating a plywood sandwich. Additional styrofoam was added to create the locations for the abutments and timber pier sets. Again, looking at the photo (still a work in progress), a bit of shimming is still required to remove the slight curvature that can be seen around both bridge abutments.
Once the basic alignment has been finalised, the terrain will be finalised, and then I can focus on the detail of the abutments and the underside of the bridge using the information Ian provided.