Prototype Research
The end-of-the-line of the Chartiers Branch was an engine servicing facility in Washington, PA. The facilities included a turntable, a three-stall rectangular engine house/repair shop, as well as the typical appliances, such as water spouts, a platform, etc. Some photos show a turntable cabin (see below), while others show the turntable without one. It must have been added or removed at some point in time. The photo below came from the "prr_panhandle_pa" Yahoo group's photo section.
The "prr_panhandle_pa" Yahoo group's files section has a Microsoft Word document that shows a map of the area dated between 1857 and 1906. It clearly shows the turntable and engine house. It indicates that the turntable was 60 feet in diameter. There is a prototype photo showing a 4-4-0 steam engine with tender on the bridge with maybe 4 feet to spare, so that would confirm the 60-foot length of the bridge. Note the orientation of the diagram. Conventionally, it should be turned clockwise 90 degrees, to have the "north" arrow pointing up.
A current screen capture of the MapQuest map of the area shows the approximate location of the engine servicing area. The area is now completely covered with residential neighborhoods. Note that the CSX Transportation line is not in the correct location. It actually runs parallel to W. Railroad St. (shown above it in white, but not labeled).
Model
On my home layout, this part of the layout is represented by a section in the layout room's closet. I will build it as a standard S-scale module, so that our club will have a turntable available to operate when we have a show. The module, therefore, will be removable and it will be connected to the rest of my layout via a simple removable section. That way I can still close the closet doors. I will probably make the turntable a bit bigger to accommodate the equipment we run on our club layout. Sixty feet scales out to 11-1/4" in S-scale); currently I am thinking about a 15 inch bridge (80-foot bridge).
The rough sketch below shows what I have in mind. Tracks "A" and "B" line up with the S-Mod interface. Track "C" connects to the removable section of track that connects to the rest of my home layout. Note that this sketch is not to scale.
Overall Status
Module frame constructed.