Bridging the Gap

What I really like about the Elmira Branch is the interesting topography that the line traverses between Williamsport, PA and Elmira, NY.  This is the portion of the branch that I chose to model.  The rural terrain, sweeping curves, steep grades, and numerous stream crossings give the feel of mountain railroading and will certainly add interest and challenges to the layout's operation.  And speaking of challenges, the modeled portion of the branch had at least four through truss bridges.  The bridges were pin-connected riveted steel single span structures and at least two of them were skewed.  Since I'm advancing the layout from north to south the first truss bridge is encountered just south of Southport Yard where the single track mainline crosses Seeley Creek on a 7-panel, pin-connected through truss bridge.

Now if the layout was being built in HO scale it would be a snap because of Central Valley's beautifully done rendition of a pin-connected through truss, but in S scale it's a different story.  At one time River Raisin Models offered a brass model of a through truss bridge.  It was an accurately detailed single track, pin-connected truss, 175-ft. long and had seven panels.  Nearly ideal, but the top chord was arch shaped and not flat like all of the Elmira Branch bridges.  They are also no longer in production, expensive, and very hard to find.  So, I decided to bite the bullet and scratch build a through truss bridge.

I found a article in an old publication from Kalmbach titled Bridges & Buildings for Model Railroads, first published in 1965.  It was a compilation of articles that appeared in Model Railroader Magazine over the years.  I have no idea how old my copy is but the price marked at the top was $3.00.  I doubt if the publication is still available, but you might still be able to find a copy on-line.

 The article has excellent plans for a 140-ft, seven panel through truss bridge.  The one drawback is that it's not a pin-connected truss, but other than that it has all the features that I'm looking for.  Also, a 140-ft span in S scale is more than 26-in. long.  I don't have quite that much room on the layout, so I chose to shorten the structure by one panel length making it a 120-ft long bridge.  My plan is to eliminate the center panel.

The original article uses strip wood construction, but I chose the fabricate the structure entirely out of styrene for two reasons.  First, I didn't want to sand all that wood smoothly enough so that it looks like steel.  And second, since I'm obsessive compulsive I can impress rivets into the styrene.

The truss members are mostly formed by laced girders for the vertical and diagonal pieces of each truss.  Building these are very tedious but the article shows how to build a template to assist in laying out the diagonal lacing bars. I would have preferred to use black styrene, but some of the sizes and shapes needed are hard enough to find in white styrene.  As a result it will be necessary to paint the girders as sub-assemblies  prior to fabricating the trusses.

Here's some photos of the complete laced girder sections:
 



This is obviously one of the most difficult parts of the structure to build.  The girders shown form the uprights for each truss panel so six of these are required (3 for each truss) the remaining uprights have horizontal lacing which are much easier to fabricate.  It will take a while for me to build this span and I will probably even need a temporary structure across Seeley Creek.  I hope to have some updates on my progress posted here so that you can see how things are going.