by Ed Enyedy/photos by the author
Structures help define the location and setting of your layout. While a train station might be the most recognizable local landmark, many busy junctions were guarded by interlocking towers. These structures started as standard designs that were often modified based upon available supplies and the site elevation, leading to a unique design for each tower.
The personal connections people have with interlocking towers compels me to create 3D-printed models, which is why I chose Grosvenor even though it was an obscure location to me. Built about 1900 outside of Athens, Ohio, this New York Central tower controlled the crossing of the Baltimore & Ohio Ohio Division. CSX now operates the former NYC line while the B&O rails have been abandoned, part of which forms the Adena Bikeway. Though the tower was destroyed by fire in 1982, the original diamond remains nearby, hidden in the weeds.
ABOVE: These photos from 1980 show the many details of the interlocking tower and adjacent tool shed, just two years before it was lost to a fire. —Karl Underwood photos, Todd Atkinson collection
Design
Creating a 3D print starts with drawing a computer model. I draw my models with Blender, a powerful, and most importantly, free, program. I was fortunate for this project to find pictures with straight-on views at
northamericaninterlockings.com. These photos were imported as a background into Blender and were useful for keeping the overall proportions in check. As far as the actual size of the building, I make an assumption that most doors are either 32” or 36” wide and scale the rest of the photo from that dimension.
Drawing the tower walls went quickly, as the shape is simple and the clapboard trim is just an array drawn once and repeated many times over. One advantage with 3D printing is that walls can be printed as a single piece, eliminating corner seams and guaranteeing a square structure.
With the main walls drawn, the next step is to cut openings for the windows and doors. I draw rectangles slightly larger than the windows to allow for tolerance and material shrinkage. I also add features to remove some of the clapboard trim so the window is inset slightly, giving the illusion it is thinner and closer to scale. Once drawn, the openings are then subtracted from the wall with a “boolean” operation. Any place where the walls and the window openings intersect gets removed. This is one place where Blender sometimes fails, and the calculation of some surfaces can get scrambled. While slower, I find it works better to make the openings one at a time instead of doing several all at once.
With the main tower drawn, I posted my progress on Facebook and asked for any additional photos for reference. I didn’t have any images of the rear and made the assumption no windows were present. Todd Atkinson came to my rescue with photos taken in 1980 by the late Karl Underwood. Included in the collection was a photo showing two windows in the upper rear wall and the chimney offset from the center. Making the corrections was easy and it was off to work on the stairway.
There is an “add-on” for Blender called Archipak which speeds up the process of drawing common elements, like roofs, fences, windows, and stairs. This powerful tool gives you the option to select all the details of the staircase — overall height and width, open or closed stairs, straight, U-shaped, or even spiral stairs. Plus there is the ability to select the railing style, post height, and spacing. For Grosevnor, I used Archipak for the basic stairs and drew the posts and railings manually because they were somewhat randomly placed on the prototype and didn’t conform to the software’s selections.
On other interlocking tower models, I’ve designed the staircases in sections because of the awkward shapes. Frequently, part of the stairs extends a distance from the tower, which would make a single piece fragile. I wanted to make the stairs one piece for easier assembly. Because the staircase derives strength from the wall and would be weak as a separate unit, temporary supports were added for rigidity during the printing and cleaning process. I also added alignment pins and corresponding holes in the walls…
