PRR Chartiers Branch: Hazel Mine - Layout Design
The diagram below is from a Sanborn insurance map dated November 1913. The space of the entire diagram scales out to be 4' by 8' in S-scale (1:64). I purposely kept the slightly rotated angle of the tipple on the right, such that most of the track work does not parallel the front edge of the layout (which is the top edge in this diagram). Yet, the orientation allows for the complete capture of all the main structures around the tipple, a good chunk of the Chartiers creek in the back of the layout, and even a bit of the Fort Pitt Bridge Works buildings (the gray rectangles in the lower-left corner). The track is still toward the front of the layout (for easy reach), and most all of the buildings will completely fit within the modeled space, including the mine entrance (in the lower-right corner of the diagram). Also shown in the diagram are two vertical orange lines. These represent the dividing lines of the individual modules that I am going to build. These were placed so as to avoid cutting structures in half. The other constraint is that the modules cannot be more than a total of 29" tall, for them to still fit through a regular interior house door (when carried sideways). However, my estimate is that none of the structures will be that tall.
Here is the same diagram, rotated such that it is oriented in the normal viewing angle. The front of the layout is along the bottom edge of this diagram. I actually like this arrangement better than the previous attempt I made at modeling this area, because the track isn't right at the front of the layout. The foreground structures will hide some of the locomotives and cars on the tracks, which will make the whole scene feel bigger than it really is.
Design Diagrams
This time I want to build a fairly complete CAD drawing of the entire project, so that I can think through all the steps to making this new layout/diorama, and so that I can share with you what is in my head. While "forcing" myself to do this, I have already had some additional thoughts that helped me figure out how to better build this diorama, so spending time doing this CAD work is well worth it. This first screen capture is of the core framework of the three modules that make up the diorama. The modules are all 48" (122cm) deep. The one on the left is 36" (91cm) wide, the middle one is 25.5" (65cm) wide, and the right one is 34.5" (88cm) wide. The boards are 6" (15-1/4cm) tall. The butt-joints will be glued together using biscuits.
Using the above-mentioned Sanborn diagram, I copied the x-y coordinates to the CAD drawing for the Chartiers creek placement. This represents the ground-level width and direction of the creek. I used a spreadsheet to calculate the coordinates and saved those, so that all I have to do is mark those locations on the plywood sheet and trace them out with a jigsaw. The idea is to cut the creek out of the single 4'x8' sheet as one piece. Once so cut, I will then cut them to match the dividing lines of the three modules. I will only be modeling the top water surface of the creek (based on what I learned from my previous attempt at modeling it), and so this piece needs to be moved down about 2 inches (about 10 scale feet, which is what locals have mentioned is the normal level of the creek) from the ground surface. I will then be able to model the creek's sloped banks from that dropped-down surface to the ground-level surface with my usual scenery base modeling techniques. The water surface will be painted a dark color, and one or more layers of Enviro-tex epoxy will be applied to this surface to represent the water. This will be one of the first things I'll do after building the basic framework, since the creek is at the back of the diorama, and some structures and trees will be overhanging the creek, making subsequent work on the creek harder.
The track layout of Sanborn insurance maps should always be taken with a grain of salt. However, their overall placement is probably close enough for an initial CAD drawing. The gray space in the diagram below represents the space taken up by the five tracks of the coal mine yard. I plan on making a dedicated track-planning CAD drawing in the near future, because I need to know where the turnouts are. I need to know the approximate space taken up in the diorama for the track area, because I plan on using ceiling tiles as the roadbed for the track. Due to the height increase (from above the plywood base), the structures need to be raised up as well, so I plan on putting them on ceiling tiles as well. I used ceiling tiles on my previous S-scale switching layout and I was happy with their sound absorption and their stability over the 7 years I had that layout (they do need to be thoroughly painted).
The design has evolved a bit more. Based on the idea that both track and track-dependent structures need to be built on top of the 1/2" ceiling tile, I decided to just cover the entire 3/4" plywood base with ceiling tile. So, that is what you are seeing in the diagram below: the vertical frame, the 3/4" plywood base, and the 1/2" ceiling tile. The track and structures will sit on top of this, and the creek will be cut out from all of them, and set at about 2 inches below the top of the ceiling tile.
With the recent design change of just using a full sheet of 3/4" plywood as the frame top, and applying 1/2" ceiling tile as the sub-roadbed, it became obvious that the front of the layout would now show the layered-cake look, which I don't like. So, in this design update, the front frame members have been raised by 1-1/4" to 7-1/4", so that the layers are no longer visible. On the sides and the rear it doesn't matter, because the backdrops will hide that.
However, to provide support for the top layers, which have now been shrunk back 3/4" and are no longer supported on the front, an extra board is necessary behind the front frame board. These don't have to be full height, so I made them 4 inches tall. Then thinking about the four-foot depth of the frame, I decided that it might be prudent to put a 4-inch tall brace in the middle as well. This provides support for the "ground" layer of plywood, and it makes sure that the long side panels stay square to the front and back (since they could potentially bow out or in). Both of these are shown in black outline in the next diagram. All of these changes will still allow me to cut these parts out of a single sheet of plywood.
Getting into new territory for me in the CAD program, I cut out the modules of the framework pieces on top of which the river piece is going to be placed. When I actually cut out the river top piece with a jigsaw, I will be able to trace it exactly on top of the framework pieces. The depth of the cut needs to be 2 inches minus whatever the thickness of the ceiling tile is. The river pieces will be attached to the framework with glue only to keep their top surface as flat and smooth as possible.
Using the diagram found in the The Engineering and Mining Journal mentioned in my Prototype Research page, rotated to match the above diagrams, this should give a good representation of the track plan for my set of modules. Track #1, the top one in the diagram, represents the straight-through line, and it feeds each of the other four tracks. The pair of turnouts forming the crossover from Track #2 to Track #3, right in front of the tipple, has been verified in one of the prototype photos dated 1913; the others have not been photographically proven. Also, I don't know if this track arrangement was still in place during the time period I model, so I am going on the presumption that everything remained the same. Still, there are 8 turnouts in this small section of the yard. Between Track #1 and Track #2, and again between Track #2 and Track #3 are run-arounds, so that would make switching even this small section a possibility. If I add no external "staging", Tracks #1, #2, and #3 can be accessed from each other, while Tracks #4 and #5 can only be accessed from each other. They connect to Track #1 further to the right of the diagram, and Track #5 merges into Track #4 further to the left of the diagram. Much further to the left of the diagram, Tracks #1 and #2 merge into #3, and the yard section comes to an end when Track #3 merges into #4 shortly before the siding merges back into the main branch line. So, the area to the right of the tipple, that which I am modeling, serves to feed empty hopper cars to the tipple for loading with various grades of coal, while the area to the left of the tipple (mostly not modeled here) serves as a massive storage yard for the loaded hoppers waiting for trains to collect them.