Fantastic pics there Mark, its good to see that bridge obsessiveness is contageous. I now expect to see a fully scaled down version appearing on Frankland I hope you know!
Now that the scenery comp is over I'll air what I was working on. If you go up the page to my posting you'll see a little bridge crossing a brook, better known as Baddesley Viaduct ~
I got the basic measurements using Google Earth and pacing between the piers underneath the real thing, and using this I worked out the basic footprint for the diorama to occupy almost the maximum permitted footprint. Then I simply attacked some loft insulating board and carved it into the basic shape of the embankments.
It doesn't really look that big like this, and I thought as much at this point, so I mocked up the bridge deck using a suitable piece of timber and posed a train on it.
Now its looking a bit bigger!
My usual method for building abutments is to build a very basic ply skeleton.
The skeleton then forms the basis for the plasticard to be fixed to. This was the state of play after one day of construction. The decorative arch was incredibly simple to do, measure the inside diameter of the arch you are using and mark this on to the piece of plasticard it is to be cut into. Cut up to the location of the arch ring and snap the waste out, then offer the arch moulding up and mark the area of the stonework which needs flattening and gently carve away the material until the arch fits snugly. Glue it in place and then cut away the material left inside the arch and file it back, then if you require you can also carve the course lines into it where the cut plastic is otherwise a flat edge.
Next to do is the string course. Using suitably sized pieces of styrene build up the basic structure for the piece, then when the glue has set hard enough you can carve it to the desired profile using filler where required as pieces of the string course fit together around the ply skeleton.
With the string course cobbled together start working upwards. The real bridge has a missing pilaster on this abutment with the parapet partly rebuilt in brick. This was replicated by cutting the stone plasticard away along the mortar lines and directly replacing it with brick plasticard. Coping and capstones are then added on top in exactly the same manner as the string course, styrene built up to the basic profile and then carved into shape.
This series of photos shows the basic process used in producing the brick repairs to the sandstone. This time it is for the pier tops, all of which on the real thing exhibit a significant amount of repair work. The process of building the piers is exactly the same as for the abutments, the basic shape is made from ply and then skinned with plasticard.
When the piers and abutments were structurally completed they were given a coat of red oxide primer. This was then washed over with a flesh colour to give the mortar colour in the deeper detail. The stone was then drybrushed with a khaki coloured base coat and the brick repair was picked out with Railmatch 'Roof dirt', which is the losest match to engineering blue brick that I have yet found. When dry brushed over a red primer base the roof dirt leaves some of the red showing through which if you look closely at a lot of this type of brickwork is present on the real thing.
Turning away from the structurally complete abutments and piers, attention now turns to the girders. This bridge was initially intended to be built for the scenery comp, and one of the stipulations was that materials be available from the NRM shop, so with this in mind I dug out some N Gauge Knightwing girders as they are very close to being scale size for this bridge in 00. Only the very ends of the girder moulding were cut away.
Cutting the ends off the moulding allowed me to join the girders as per the prototype, and also allowed me to use the base plate of the kit itself to tie the girders together at the weak points. Basically the whole bridge deck was built upside down for its intended use.
With the girder decking complete and cut to the desired overall length the next step was to cut and fix the timber deck in place. The real thing uses 9" by 6" timbers so I used 3.2mm by 2mm styrene cut to length, a 'chopper' really helps to do a bulk job here! I also made up a jig to accurately lay the timber deck, this really made the process very easy indeed!
The next tediously repetetive job was the construction of the handrail stanchions, again a job for the chopper! Holes were then drilled to accept the handrail using a small spring clamp to keep a uniform distance between the holes.
A ballast board was then attached to the bridge deck to give the stanchions that bit more plastic to adhere to as well as giving them a fixed line to follow. With the handrails built it was out with the chopper again to cut another round of handrail supports which project below the timber deck and attach to the girder on every second gusset. Once dry the excess at the ends was removed and filed flat.
With one week to go until the deadline for the competition this was the state of play. Sandstone given two lighter shades of dry brushing to pick out some of the moulded detail in the plasticard, bridge deck painted and just the last abutment to paint up. All that is required to complete is the scenic scatter and the stream running below, which would probably take a day or so to complete each.
Considering it only took me 3 weeks to get this far I am quite pleased with the result and would have probably finished it well within the original deadline for the scenery competition. Progress is on hold with completing it though as my MRC discuss building a modular layout, this bridge is now intended to form a part of that layout.