Bridges in the Works

Posted on August 24th, 2010, by Mike

I’ve been working on building a multi-span steel bridge that runs across the lift-out section that forms the entry into the staging yard. This is where the scenery starts, so while this particular bridge doesn’t represent any specific location on the mainline, I figured it needs to look like a finished portion of the layout proper. To that end, I’ve molded and coerced some topography to fit around the three leads into staging, which occur at different heights.

Bridge Pic 4385

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I still don’t have adequate lighting in my basement, so the quality of these photos vary somewhat. In this first pic, you can see staging tracks in the background, with my Class J and its maroon passenger train in front of the Seaboard Air Line Silver Comet. My layout isn’t gonna be a passenger-running layout, but sometimes you just cannot resist a good set of varnish! These two trains are on the upper deck of staging, representing Roanoke, Virginia, and other points “east” (in one of those famous quirks of railroading directionality, eastbound trains from Winchester actually travel mostly southwest down to Roanoke, where they are re-blocked with other N&W freight moving eastward to Norfolk).  The lower level is six real inches below, representing Grafton, West Virginia and points west.  The bridge carries the lead into Roanoke over the lead into Grafton.  In between these two, there’s a tight curve that is a single staging track for the local to Culpeper, Virginia. This will be a single train operated with Southern motive power, which is interchange traffic from Culpeper General Transit, a short line that runs on the former WP&P mainline to Richmond.

Bridge Pic 4404

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I built the bridge such that all the supports were hanging from the deck. This way, I could build the scenery right up to the foundations and thus set them naturally into the ground. These photos were taken as the plaster was freshly applied and still wet; when dry it will be significantly lighter in color, aside from the blend of sand and colored ballast that I’ve sprinkled on top. You can see my scenery methods in these photos – a plywood base at the lowest level of intended scenery, some expanding foam (“Great Stuff” brand comes with a neat little straw/nozzle that makes it easy to control), then a coating of plaster which is colored throughout. This becomes my “soil model”, and later I’ll vegetate it with conventional ground foam and static grass. Because it looks natural and real without any greenery applied, though, it is forgiving of inconsistency in foliage application, and tolerates abuse well. When I plant trees, I won’t end up with little piles of white plaster powder after drilling root holes.

The bridge is a combination of Micro-Engineering and Walthers kits, plus some scratchbuilt concrete piers. M-E supplied the steel trestle and deck girders, and Walthers contributed the plate girder. I wasn’t intended to make my own piers at all, but when I tried to figure out how to support the widely spaced plate girders on the skinny M-E steel bents, I realize I was gonna need something different. My piers are just simple styrene forms, painted with my favorite concoction: thinned acrylic paints to which a small amount of joint compound has been added. It dries with a noticeable grit to it, looking and feeling like concrete, and taking weathering very well (I use chalks mostly).

Bridge Pic 4399

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I will ultimately cut a front fascia to match the contours of the hills, but I need to let the plaster dry first and then I’ll be able to scribe it exactly. The back side,  however, towards the staging yards may well just stay the way you see it here, with the foam exposed and then plywood showing. Other finishing touches include the guardrails across the bridge, and details like the fire barrels and platforms.  Also, you can see that I need to add a few more ties at each end of the bridge, and then finish the ballasting.

As mentioned before, this bridge is actually part of a lift-out section, which is in effect a benchwork bridge. I’ve treated another drop-leaf section similarly, rendering it as a bridge; I like the way the model matches the real function.

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