MRL Bridge 218 has progressed a little recently. Five piers, two end abutments and the approach spans have been completed in a bid to span a large gap at the west end of the 4th Sub mainline where it crosses the Clark Fork River at Paradise MT. Without this structure, trains cannot begin to operate as intended. Using Kato Unitrack truss spans has saved some time and considerable amounts of money over using truss bridge kits, despite time-consuming modifications to the spans to off-set them to cross the river at an angle.
As of today, the track panels for each span are complete and a timbered bridge deck to create the impression of ‘bridge track’ is being installed using strips of 40thou styrene card. That is a mind boggling task in its own right, but given that Micro Engineering Company track bridge track is difficult to find in the UK, it is a viable option. The gauge of 9mm for N scale is achieved by soldering code 55 rail to copper clad sleeper strip, spaced to match the trussing members. The gaps are then filled in with styrene strips to represent the larger timbers used in bridge track. Each truss section has its own track panel and the truss spa track sections will be joined using the track rail joiners when assembled on the piers.
The structure is loosely placed on the layout to check the height of the bridge track with the adjacent abutments. There remains a few millimetres of adjustment to do in raising the bridge which can be done by completing the bearing pad detail. The piers are constructed of 80thou styrene with a wrapper of embossed stone card by South Eastern Finescale which was leftover from another project. The real Bridge 218 has concrete piers which, until recent repairs were undertaken by MRL, were looking pretty weathered and heavily patched and repaired. Embossed styrene card provides a key for a smear of Squadron filler which will be roughly rubbed down to create the desired worn concrete effect – some of the outline of the stone embossing may show though in places adding to the patched effect. Smooth styrene sheet would not have been so visually effective.
The structure will be used on the layout in unfinished condition for a time until the spans are painted dull black and weathered; the piers painted in some lovely warm concrete colours and a newer highway bridge constructed and placed immediately behind the rail bridge. Some additional detail remains to be added to the Unitrack truss spans over the next few modelling sessions.
It is turning out to be a long, long project, but one which I think will produce a passable representation of Bridge 218 on MRL at Paradise MT. Whilst there are some significant detail differences between the real truss spans of Bridge 218 and the Unitrack models, the compromise will be acceptable to me now the spans are off-set to cross the river at an angle and in the process of being detailed. There is not N gauge kit which could be used to make the truss spans making up Bridge 218 that is readily available. So rather than slip a piece of plywood in as a stop-gap, the Unitrack spans seem to be a fair substitute and should carry heavy (for N scale) 10 to 12 foot long trains without difficulty!