The actual layout design

 Well, I have been asked multiple times about the actual design of the layout. So,here are the working drawings from 3rdPlanit that I have been using as I build. This first drawing shows the main line in the  center of the room in black. The overall distance on the diagonal is about 70 feet. You can see that I have had to deal with a very odd shape to the room. The two lobes on the right side were wide enough so that I could get return loops in while maintaining a 62 inch minimum radius on the main. The main line ends on this drawing - where it goes into the hidden yard which is below the main yard.
 You can also see the outline of the branch line benchwork on the wall going around 3/4's of the room starting at the bottom and going up to the top wall.  My problem was getting the branch around the lower left turn where the wall rises from the bottom and turns left. I had to squeeze in the branch, a 3 foot aisle and then 9 tracks in the yard/main of Northumberland. To do it I was forced to reduce the aisle to 28 inches for about 2 feet right at that corner.

 This drawing shows the main line and the hidden yard. It starts where the main leaves the upper yard (Northumberland), which is visible. You can now see the branch line in red. I used this drawing to figure my grades as I went from the base elevation in the hidden yard to the upper yard. I placed that 9 inches above the hidden yard and ended with a 1.75% grade. This allows me reasonable train lengths with the engine lash ups I plan to use. I used the branch line drawing to see what grade I needed to be able to cross the aisle at the top of the drawing with a through truss and have people be able to walk under it.

This is last drawing that I used to compute my track lengths for materials. It shows the overhead loop in light green added to the end of the branch line. You can see the branch track crossing the aisle at the top of the drawing. You come in that top door on the right and walk along the wall until you turn right at about the mid point of the room. I am making a field change by moving the aisle crossing to the left as I realized I cannot get a 40 inch straight section ( the bridge) in place and still make the curve I need to turn back to the overhead loop. So, the new location of the crossing is about 1/3 the way down the aisle from the door. This has forced me to increase the grade to 3% from the 2% it is up to Weigh Scales. This is actually prototypical as the grade stiffened beyond Weigh Scales in real life.
 So that is the design. It took me about a year to get everything figured in due to the shape of the room. I originally want to have the yard on an outside wall and the branch climbing through the center but could not get that to work. This design allows the branch line engineer to walk with his train and accomplish the switching I enjoy, while having main line trains run through the layout until we need to change engines or blocks of cars. I have done research on he scheduled freights that ran through Northumberland and will try to incorporate them as well as the passenger trains. I plan to use the branch as the line to Wilkes Barre also to add diversity the trains heading up and down the line. I can run some way freight on the main, but it is not as convenient for the operator. The control system will be conventional DC with Tower Operators like on the PRR.
 More later.