Building a Model Railroad: Preliminary Design Issues

In my last post, I developed the rationale for my miniature railroad empire.  With a rationale and purpose for the railroad decided on, I could then move to the design of a track plan that would link together the three main “scenes”of the layout: The small mining village of Robertsdale; the EBT station and shop complex at Orbisonia; and the busy industrial interchange between the Blacklog Valley and the EBT at Blacklog. 

A scale model of anything but the simplest of railroads requires more space than most modelers have available.  Hence, the first step in creating a viable track plan is deciding what to leave out!  Since I model in HO scale (1:87), it quickly became clear that attempting to reproduce the 30-mile long EBT would be impossible.  A one mile long siding in HO would require more than 60 feet!  There simply isn’t enough space.  My train room is a finished bump-out in the attic that measures roughly 19 x 19 feet, with a 10 x 11 foot extension at one end that I use for my workbench, files and storage.  This is a substantial amount of space, but compromises were still necessary.

Thus the first decision in designing a track plan is to determine the maximum available space for the railroad.  In my case, there were windows on two walls of the train room, which complicated the placement of the benchwork.  I decided to leave an aisle along the window walls, placing the benchwork flush against the other two side walls.  This left me with a space of approximately 13 x 16 feet for the layout. 

Knowing the available space is only the first step in layout design.  How to fill that space with an operating model railroad involves a number of critical decisions.  At the very least, these decisions include:

·         The minimum radius of curvature

·         The minimum aisle width

·         The height of the benchwork above the floor

·         The maximum allowable grade

·         The type of benchwork construction.

  

All these questions will affect the design of the track plan, the benchwork, and ultimately, whether you have a model railroad that is interesting and fun to operate, or one that will be a constant source of aggravation and frustration.

Minimum Radius of Curvature

How sharp you make your curves depends on a number of factors, including the wheelbase of the locomotive and the length of the rolling stock.  Many articles have been written on the technical details of building curves on a model railroad; but for simplicity, I opted for a minimum radius of 24 inches for my HO scale Blacklog Valley, and 22 inches for the Hon3 East Broad Top.  In some places the radius is as much as 26 inches; in a few places (such as the wyes at Blacklog and Robertsdale) the curves are somewhat tighter. 

Minimum Aisle Width 

One of the most common errors in building a model railroad is making the aisles too narrow.  In an effort to increase the space for track and scenery, it is tempting to skimp on the width of the aisles.  I have learned through experience that while you may be able to get by with an aisle of 24 to 30 inches, a good three feet is the minimum when there is more than one person operating the trains.  Squeezing by visitors or guest operators is really difficult with anything less.  In my case, the side window aisles are 40 inches wide and the center aisle is three feet. 

Height of the Benchwork 

How high your model railroad is above the floor is a matter of individual taste.  The Lionel train layout my father built for me as a boy, rested on short sections of 2 x 4 placed on edge, making the layout was less than 4 inches off the floor.   This must have made wiring a nightmare!  My own preference is to have the railroad slightly below eye level.  Since I stand about 67 inches tall, I chose to set the height of the benchwork at Blacklog at 46 inches.  This permits me to view trains up close and personal, while allowing for easy access to mechanical and electrical work under the benchwork. 

Maximum Allowable Grade 

The ruling grade is the maximum degree of incline.  Prototype railroads generally operate with grades of less than 2 percent.  A 2 percent grade equals an increase of 2 feet in every 100 feet, which is fairly steep when you are pulling tons of freight uphill.  Some narrow gauge railroads had steeper grades, but rarely more than 3 or 4 percent.  Steep grades meant using helper engines, or sometimes breaking the train into smaller units.  Either solution added to the cost of moving freight.  Railroads were extremely creative in finding ways to avoid steep grades. 

On my layout, I arbitrarily set the maximum grade at 2 percent.  Coincidently, Woodland Scenics sells styrofoam inclines for two, three and four percent grades.  My Hon3 East Broad Top has a steady 2 percent climb from Blacklog to Rockhill, and again from Rockhill to Robertsdale. 

The HO gauge Blacklog Valley Railroad has a 2% descending grade out of Blacklog, such that the return loop passes 5 ½ inches below the narrow gauge EBT at Robertsdale.   In the photo below you can see the standard gauge tracks of the Blacklog Valley emerging from beneath Robertsdale on the HOn3 East Broad Top. 

In my next posting, I will explain how I built the benchwork that supports the layout, and why I decided on extruded foam insulation as the base for the railroad.