Joined: 18 Oct 2004
Location: Minneapolis, MN, USA
|Posted: Thu Oct 08, 2009 3:41 pm Post subject: ZM-14 Three Span Stone Arch Bridge
|Three Span Stone Arch Bridge
Looking for a simple project that keeps to the Zenmaster’s rules that state you don’t want to have the same model that all other model railroaders own? Most N-Scalers aren’t shopping for bridges in a wargame miniature catalog! GHQ makes lots of fine buildings and other terrain kits for their Micro Armour® range. These models are in 1:285 scale – which is smaller than Z scale! So while most of the buildings could only be used in a forced perspective setting, the Three Span Stone Arch Bridge kit (GHQ’s TMB22) works very nicely in N scale. They also offer a One Span Stone Arch Bridge (TMB23) which could be used for a shorter span.
The bridge kit comes with
• 6 x single arch spans
• 4 x piers
• 4 x plinths (sprued onto one tree)
No roadbed is supplied – you cut that out of your preferred material: Strathmore board, other cardstock, wood veneer, sheet plastic, modeler’s plywood, or sheet metal would all work. I used styrene plastic, but we’ll cover that later. There is a shelf that runs the length of the spans upon which the roadbed is glued.
After thinking about it, I decided to paint the stone structures separately. The roadbed and the sidewalk would be concrete.
ASSEMBLING THE STONE STRUCTURES
No instructions are provided with the kit, but assembly is very simple. The ends of the spans nest very nicely into the piers. Super Glue works very well on these pewter parts.
The plinths are shown in the photo above – they are the ‘feet’ that raise the outer ends of the bridge to the same height as the central piers. Glue them on so that the mounting shelf is in the back (interior) of the bridge and the face details mirror those on the piers.
There is a lot of limestone in the area I’m modeling, so I base coated the assembled stone bridge pieces with a deep crème color using an airbrush.
Some of the area’s limestone is gray, and I decided to spruce up the bridge by making some of the quoins and the capstones a gray color.
To pick out the details, one great technique is to apply a wash. Since these parts are all metal, I used a turpentine based wash with about 1 part per 20 of Testor’s black enamel paint. After the wash was applied to the outer faces of the bridge, it was left ‘on it’s back’ to allow the pigment in the wash to sink into the crevices. After it dried, the stone assemblies were flipped over and a wash applied to the interior walls.
CREATING A ROADWAY DECK & SIDEWALK
I try to learn something new everyday. This project caused a simple internet search: how wide is the standard highway lane? Twelve feet it is! I wanted to be able to add some details (like maybe a fisherman or pedestrians), so figured a three foot wide sidewalk on one side of the bridge would be a nice touch. I considered adding a shoulder, but opted against that as I didn’t want the bridge too wide. A 27’ prototype width equated to 2.025”. Using a sheet of Evergreen styrene .040” thick, I cut the decking out using the standard “score and snap” technique. To facilitate blending the bridge deck into the surface of the surrounding highway, I left an extra half inch, more or less, at each end.
The side walk was made of a strip of the same styrene three scale feet wide (.225” in N scale). I used a metal straight edge and a hobby knife with a #11 blade to add score lines both for the edge of the curb and to segment the sidewalk every 3’ scale feet. To increase the width of the scores, before moving the metal ruler, I reversed the blade and re-scribed the slot with the back edge of the blade. After cleaning up the fuzzy scrap that the blade created, the sidewalk was then glued flush to one side of the bridge deck using liquid styrene cement.
The bridge roadway looked sterile compared to the sidewalk, so I scribed a center line and then an expansion joint perpendicularly every twenty scale feet (1.5”).
For color, I used GHQ’s Haze Gray (GHQ’s CLR16) as a base coat of cement gray.
Both to accentuate the scribed expansion joints, and to weather the deck, I mixed up an acrylic wash, still 20 parts water to 1 part black acrylic paint, and with a drop of dish washing detergent to break the meniscus. This was flowed all over the deck, and then worked with a small paint brush to make the stains on the roadway look realistic on the large, flat areas of the deck.
PUTTING IT ALL TOGETHER
This step was pretty easy. Making sure that the two sides of the bridge were squarely aligned, a thin application of super-glue was applied to the top of mounting shelf on both sides of the bridge. The deck was laid in place. Make sure that the edges of the roadway abut the sides tightly. Below is a bottom view of the finished bridge: note the mounting shelf on the pewter bridge sides to which the deck has been glued.
Flip it back over, and mount onto your module or layout! Though stone bridges are older, many are still in service across the country.
The GHQ one span bridge can be found here:
and the three span bridge can be found here:
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