This will be a two level layout. Her is the calculation I ran to help design the helix that will allow trains to move between levels.
Track radius is 22″ which takes the diameter of the ring to 48″. Rings are 4″ apart vertically. Grade is 2.65%. 4.5 rings (18 segments) will allow trains to exit 18″ higher than they enter. Segments are 6″ wide. I should be able to cut from one 4’x8′ piece of plywood. Cuts would generally look like this although there will be less of them.
This is the helix design that makes the most sense to me. It is attractive and allows crawl under to the center of the helix to deal with disrailed trains.. It could also be enclosed. Trains would enter at 32″ (lower deck) and exit at 50″ (upper deck). Helex would be located outside the train room wall. Helex would be reversed from this photo.