The approach & yard trackage for South Station is quite complicated as it allows a train on any of the 10 approach tracks to stop at any of the 28 platforms in the station. In order to do this amazing feat, the yard has to have a bewildering array of crossings, crossovers, wye's, & slip switches. etc.
In the very center of this puzzle is center diamond. The center diamond consists of 4 - 14 degree crossings arranged in a diamond pattern as you can see in the above photo. This diamond allowed trains to cross from one side of the yard to the other. The crossing also effectively split the yard in two; with platforms 1-14 serving one side of the yard, and the other side serving platforms 15-28.
When creating the track design for South Station, it was logical to start at the diamond as the spacing between the tracks were at their closest to point to each other.It also sets how the 28 double-slip switches that radiate from the diamond will be placed. From there, everything else falls into place.
This is the drawing I used to design the track plan for South Station. The drawing is the original 1898 plan of the yard trackage.
If you look at the drawing, you will notice that everything radiates from the center diamonds. I scaled the drawing to the correct size (this drawing scale is way off) as I already had the plan of the track platforms to scale from another drawing. From there it was easy to determine scale as I had a known measurement (the platforms). In HO scale, the Yard, buildings, & streets translate to roughly to a scale plan of 11ft x 30ft in HO Scale.
I re-created the entire plan above using 3rd Planit Railroad Track Planning software. I needed to draw a plan so that I could determine not only scale, but how many of what types of trunouts, double slips, crossings, etc. I would need to either build or buy. Here is a shopping list of the switches I will need in order to complete the project:
#6 Turnouts - 43ea.
#8 Turnouts - 24ea
#8 Double-slips - 30ea.
#6 Double Slips - 4ea.
19 degree crossings - 1ea
14 Degree crossings - 4ea
#10 Curved turnouts (various radius) - 10ea
#8 Curved turnouts (various radius) - 4ea
#6 Curved turnouts (various radius) - 6ea
#8 WYEs - 2ea
#6 WYEs - 2ea
#6 3-way Turnout - 1ea
Total number of switches I will need to build or buy - 131
Large amounts of switches, such as the #6 turnouts, #8 Double-slips, #8 turnouts I am building using Fast Tracks. The rest will be handbuilt,Fast Tracks,, or Shinohara code 83 track. All of the connecting pieces, curves, etc will be either hand-laid (again using Fast Tracks) or Atlas Code 83 flex track.
Not only is there a scary amount of switches, but the amount of switch machines & Digitrax DS64 I will need to buy. Your #8 Double Slip requires 4 Switch Machines to operate. Your DS64 controls 4 Switch Machines. So, lets do the math:
34 Double Slips (#6 & #8s) = 136 Tortoise Switch Machines & 34 DS64s.
82 Turnouts = 82 Tortoise Switch Machines & 21 DS64s.
1 3-Way Turnout = 2 Tortoise Switch Machines & 1 DS64.
Grand total = 220 Tortoise Switch Machines & 56 DS64s.
As of today, I have exactly 44 Tortoise Switch Machines & 0 DS64s.
OTOH, Rome wasn't built in a day & neither will this layout. As I am still in the planning & designing phase, I am slowly stockpiling material to begin construction. I have been buying flextrack, bulk rail, & Tortoise Switch Machines when I have the time & Budget. Currently, Fast Tracks is eating the budget as I needed to buy the following construction jigs to get me moving:
14 Degree Crossing - Part # AF-HO-X-14-ME83
#8 Double Slip - Part # AK-HO-S-8-ME83
#8 Turnout - Part # AK-HO-T-8-ME83
#6 Turnout - Part # AK-HO-T-6-ME83
So far I have purchased all of these jigs complete with the exception of the #6 Pointform Filing jig. When I purchased the #6 Turnout jig, I only bought the jig as I wanted to see if had the talent to actually build a turnout from scratch. It turns out that I actually enjoy building switches using Fast Tracks so I went ahead with the more expensive purchases. As the layout progresses, I will no doubt be buying more Fast Tracks jigs.
Of course, there is the problem of trying to work (or play) on a layout that is 11 feet wide. The average arm reach is 3 feet so that leaves me with how to be able to reach the center of the yard without having to be suspended from wires above the yard. The work-around for this will be to construct the layout so that the buildings & street that surround the edge of the yard will be able to be removed & moved away from the tracks. In other words, the parts of the layout such as the head house, baggage, express & power buildings will be able moved complete with the substructure. If I plan correctly, I can reduce the reach from 11 feet down to 6 feet. But, in order to do this, I will need to build the benchwork so that it is removable along with the structures on top of it.
Fortunately, a good friend of mine is a furniture maker who's shop is right over my layout space. He has agreed to help me work out the logistics of making the structures & benchwork removable in such a way as to not damage anything.