First, it's true that I could easily move the loop section to the other desktop where I had easy access. Unfortunately, the only way to test that the subroadbed was level was to have the loop section in place on the corner desk. So this meant taking a few level readings, moving the loop section and making adjustments, then move the section back again to get more level readings. Lather, rinse, repeat. However, knowing that once track is down this section will no longer be movable, and knowing how hard it will be to fix it once it can't be moved, I was determined to take as long as it took to get the construction right.
Second, although I had that nice CAD drawing I had only a partially complete idea of how I was going to construct the mid and upper tiers. I drew a few sketches and had a plan, but I knew this was going to be an iterative prototyping process, and very possibly could require backtracking part of it and doing it again.
After lots of measuring, building cardboard mockups, cutting wood, sometimes recutting wood, etc, I got to this point by the 26th of December. It doesn't look like much was done:
You can see that a half-circle of the lower tier staging loop is in place, an apparently no other change. However, those little bits of white on the right of the photo are plastic shims I made during the first failed leveling process. I was thinking ahead to trying to reduce the grade of the top tier, and so I tried to set the lowest tier as low as possible, to the point of even having to cut into parts of the grid itself to fit the subroadbed in place. After a few hours of struggling with this I gave up, recognizing that this approach wasn't well suited to leveling the subroadbed.
At that point I returned to the tried and true method of C-clamping each pier support to part of the grid, adjusting it until the top is flat and it matches the level of the nearby pier support, then putting in two screws (after drilling pilot holes) to hold it place. Once all piers are in place, put the subroadbed on top, use one 1 1/4" screw (with pilot hole) to anchor it to each pier, then test for level and adjust as needed.
Note the blocks of wood on the desk to the right. These are 2x2 sections that have been cut to be the pier supports for the second tier. At this point I'd measured everything I'd need for the second level, but I didn't have that ready until January 4th, as shown in this picture:
The mid tier support piers are in place and everything is level. Because some of the piers were not completely covered by the mid level lauan plywood subroadbed, I cut small sections of the plywood to fit over the tops of those piers, and glued it on with wood glue. This is so that there will be a flat surface for the third level.
Getting all those piers level was a challenge. I eventually constructed special purpose wood block that sat on the low tier roadbed and covered the mid level tier, thus setting it's exact height relative to the roadbed. Even with lots of careful measuring, adjustments were needed after it was all in place. I didn't affix the mid tier roadbed yet, as I wanted clearance to lay the low level track.
Over the next few days I measured and cut all the pieces for third tier and put everything in place, without glue or screws, to make sure it would fit. Then I measured where the tracks would be placed as they left the loop area, and built cardboard mockups of the three levels to make sure it all was going to work. Once that was done I started laying the low level track. On January 17th this picture was taken:
The most obvious change is that the subroadbed and track are now in place, and if you look closely you can even see that they've been wired. At this point I'd tested the track with large cards and locomotives for track quality and clearance, including overhead clearance. During the testing I found to my dismay that the subroadbed was tilted so that trains leaned away from the center of the circle. Exactly the opposite of a superelevated curve. My first thought was to rip it out and start again, but I remembered having successfully added super elevation to the 17-20" curves on my first N scale layout in 2002 by putting plastic shims under the ties on the outside of the curve then gluing them in place. So I tried the same here and low and behold the result was a level (crossways) track. However, I did learn a lesson and now am religious about checking that the subroadbed is level across as well as lengthwise before moving to the next step.
In the spirit of austerity I reused the rail and roadbed that had been on the loop of the mid tier of the first staging implementation. Again, this was a learning experience. The blue roadbed was useable, but had enough dried glue on it to make it hard to work with. I'll probably not reuse the blue roadbed again, given how cheap it is. The track also had a lot of dried glue on it. I learned from this to simply scrap the dried glue off the bottom of the track with a paint scraper and then it's ready for reuse.
If you look to the right side of the photo you'll see some pieces of plywood that are pre-cut for the mid tier level and also some of the cardboard mockups. What the photo doesn't show is that at this point the rest of the old staging has been taken down and that pier supports for level 1 are in place half way down the staging wall.
As I looked at this I could not believe how long it took to get to that point. Fortunately the mid and upper tier went faster, and the subsequent work faster still, simply because in this approach I did the hardest stuff first.
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