Hot on the heals of my blog post describing the town of Rosa Park, I thought I should explain how the diamond crossing is going to work since it is a rather important operational feature on the model railroad.
As stated previously, the diamond is necessary to bring the BN/BNSF track from an outside curve on the visible part of the layout into staging which is on the inside of the layout. The BN/BNSF tracks essentially loop around the lower deck but travel only through Marshall on the layout itself. Although the focus of the layout is the Dakota, Minnesota and Eastern (DME), I wanted an interchange with the BN/BNSF and I also wanted to just run a train in a continuous loop at times while working in the garage. But I also wanted the DME line towards the rear so I could place industries along the backscene and to enable it to leave Marshall on an incline (hidden) behind the garage doors to get to the (to be constructed) upper deck. After all, the upper deck is essentially the DME line from Marshall to Evan that I am actually modelling.
Here is an earlier generic plan of the layout, albeit some changes have since been made and I will mention one of those changes now. You can see the position of the town of Rosa Park and how the DME and BN/BNSF lines cross as they approach the peninsula. You can also see the BN/BNSF staging area behind Rosa Park and how it loops around behind Ivanhoe to cross over the doorway from where it can make a continuous loop. In this plan DME staging is to the left of the doorway but this has now changed to BN/BNSF stub-ended staging and the new DME staging is along the back of the garage doors. The new DME staging area can hold four staging tracks and the incline from Marshall to the upper deck, even if the diagram suggests insufficient space!
Photo 1 shows the diamond crossing and the BN/BNSF track moving from the outside to the inside of the baseboard where it joins the staging yard on the blue mat. This is an older photo and doesn’t show the final track positions in staging. The position of the water tower is still to be determined but it will have a critical role to play as I will explain shortly.
The crossing is a necessary part of the model railroad in order to move BN/BNSF trains from one position on the layout (the visible part) to another part of the layout where trains are stored in staging, or can complete a continuous run. As such, the BN/BNSF trains are considered to be moving through Marshall or they are somewhere else. There are two explanations for this: the first is that we consider offstage storage of trains to be representative of other parts of the railroad (e.g. an extension of the Marshall subdivision and other connecting parts throughout the United States) when we think of the prototype. However, we also need to consider that we are also operating a model railroad and we need to work out how best to channel trains from one place to another for model railroad storage purposes. So long as the model railroad storage purpose is not visible to us, we can maintain the illusion that our trains are moving through Marshall and going to another place – Wilmar, the Twin Cities, Sioux City, Kansas City, Spokane, the Pacific and Atlantic coasts, etc. I therefore have no problem moving my trains offstage in whatever manner best suits to maximise the operation of the trains on the visible part of the layout. This is not revolutionary by any means: some layouts have offstage storage where trains are built up by pulling freight cars and locos off shelves or from drawers.
In Photo 2 we see a mock up of the backscene boards used to separate the visible layout at Rosa Park and the hidden staging. Note the short board hiding the diamond from Larraway Lumber. It does look a tad messy but I am hopeful that with the right buildings and backscene the gap won’t be as obvious. But yes, one will indeed see a “mousehole” when looking from either side of this part of the layout (i.e. trains entering from the curve around the peninsula or when DME trains drive through Rosa Park to Marshall). For now, I will call it a transition zone and leave it that! The transition zone does not exist on the railroad, much the same as a helix does not exist on a real railroad. I will need to find a name for it though because the dispatcher must tell BN/BNSF crews when they can cross the diamond, while crews need to tell the dispatcher they are positioned short of the diamond and ready to come out onto the layout. And this is especially important for safe working.
The envisaged safe working procedure is actually pretty simple. Please note that I am about to explain the safe working procedure for the model railroad. DME trains do NOT have to seek permission from the dispatcher to travel through the transition zone between Rosa Park and Marshall. The default on the DME is that the transition zone does not exist. However, all BN/BNSF trains MUST stop on approach to the diamond from staging (i.e. from the right). The dispatcher can only allow a BN/BNSF train onto the layout by crossing the diamond when no DME trains are coming through. Once a BN/BNSF crew have the OK to proceed, their train crosses the diamond and enters the visible part of the layout on the outside curve of the peninsula which takes the train to Marshall. Once the train enters the visible part of the layout, the train is now “on the prototype” and will operate accordingly.
In Photo 3 we see a coal train crossing the diamond only after the dispatcher gave permission for this train to be at this point on the layout. This is naturally the case for the train coming from both directions. For trains coming from the east (the left) that will leave Marshall to go around the outer curve on the peninsula, and enter staging by crossing the diamond (from the left), the crew will get permission from the dispatcher when the train first arrives in Marshall. These trains actually originate from one of the four stub-ended sidings behind Rosa Park and continue behind Ivanhoe to cross the doorway and enter the BN/BNSF main just before the MSC/ADM industrial complex. Staging and operation around the doorway is actually handled by a yardmaster rather than the dispatcher but both yardmaster and dispatcher are in communication with each other.
Note that ALL DME trains take precedence. If a DME train will be in the way the dispatcher will hold the BN/BNSF train in staging or at Marshall until the passage is clear. Holding a BN/BNSF train in Marshall might be for any number of prototypical reasons, but holding for “the diamond crossing to be clear” won’t be one of them.
In photo 4 we see the same coal train crossing the diamond. Let’s pretend it is actually moving from right to left as though it has come onto the layout from staging. But how did the crew and the dispatcher know where the train was prior to getting permission to move onto the layout? The diamond in this transition zone will be hidden, as are the storage sidings themselves (remember that the upper deck will be over the top of the storage sidings eventually).
There are two options. The first is the use of a small wireless camera and screen but I am still to be convinced that this is the best approach. The second option is a little more creative and potentially offers the right type of information using a sensor and a LED.
And this is where the water tower comes into the picture. I envisage having a small light on the top of the water tower (I think Model Power or Korber might have even have sold water towers with blinking lights on top) which is activated by a sensor (an IRDOT most likely) when the BN/BNSF train is about 6-8 inches from the diamond. When the light is activated by the sensor the train must stop until given the OK to proceed by the dispatcher to cross the diamond and enter the layout (and thus now on the railroad). I need to give this spot a name (most likely a town). The crew can alert the dispatcher by saying that the train is at Split Rock (for example) and the dispatcher can say to hold at Split Rock or to proceed from Split Rock.
This is just speculation at this stage of layout construction. However, considering different operational options and making the distinction between prototype and model railroad is already making a difference to how I think about potential track changes and operation strategy. The proof of the pudding is yet to come. But at least we can start imagining the taste and what it might look like while it is still being cooked up.