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Mianus River Drawbridge Module Track Plan.

Mianus River Drawbridge

HO Scale Drawbridge Module Design

Track Plan At A Glance

Layout Theme: Drawbridge Module
Layout Type: Module
Size: 24"x48"
Scale: HO Scale
Era: 1990s
Track: Code 100
Turnouts: N/A
Min. Radius: N/A

Article by: Jim Spavins
Published: September 6, 2016

Drawbridges and modules are made to go together.  Animation on modules generally draws a crowd at a train show and drawbridges are one way to capture attention.  However, building a drawbridge for a module offers a unique set of challenges.

The design of this module is based on the colorful drawbridge over the Mianus River in Cos Cob, CT. Here, trains from Amtrak and Metro North cross this river every day.  As with any prototype-modeling project, a fair amount of selective compression would be in order. The real bridge has several approach spans whereas the model only has one on each side. However, by using the same colors, similar details like the extra height electrical towers, and placing the bridge in the appropriate setting, the bridge can be made easily recognizable by those who know the area - even if the dimensions are compressed. If you have more room or a bigger vehicle to transport the module to train shows, a six foot long module could also be constructed to fit the full length of the bridge.

In the design above, the center bridge section is the movable span portion of the structure. While a nice static model can be made of the bridge, adding this animation feature of having the span raise and lower will be a crowd pleaser. 

There are a few tricks to constructing a drawbridge I learned from experience (see CT River Drawbridge and Niantic River Drawbridge).  One of the most important aspects of constructing the drawbridge for a module is its durability. Since the model will be put through its paces when being moved, it is important the bridge be built from rugged materials.  As an example, one thought might be to use Atlas warren truss bridge kits (kitbashed) for the approach spans as these are very solid when assembled - and don't look too bad when painted and weathered.

Second, it is important to keep the bridge protected during moves. An obvious idea is to have the bridge sections be removable and placed in a separate box. By drilling holes in the piers and abutments and adding a short section of brass rod to the underside of each bridge section, the bridge will line up in the same spot every time it is setup and ensure smooth operation.  If you felt confident, you could simply build a cover for the entire module and build the bridge in place.  The only potential downside was that if some maintenance needs arises, the bridge would need to be removable anyway to fix problems without damaging the model.

Finally, to get power to the tracks, the easiest solution is through the use of plugs built into the base of the bridge and the piers.  This allows solid connections to the mainline track power feeders and doesn't rely on rail joiners to conduct power. If constructed properly, these plugs and connecting wires should be almost invisible to the viewer.

A view of the brightly painted Mianus River Drawbridge during a traffic jam on I-95. (Don't worry, I wasn't driving!) | Photo by Jim Spavins.

For Track Plan Tuesday's, I am digitizing all of my old track planning notebooks and sharing the designs here on the website.  To see all the plans, visit the track plan home page at: jimspavins.com/jimstrackplans.