Some adjustments and problem solving

Construction doesn't always go exactly as planned, especially when you are trying new techniques. This picture shows two adjustments that I had to make to solve of the problems I've encountered so far:



On the right side of the photo you see a red-handled C-Clamp in place. It's holding that section of plywood in place while the Elmer's Wood Glue dries. You see, I mismeasured the curve angle when I cut that subroadbed, and although I re-checked it, I thought I'd left enough extra width as a precaution so I didn't check to closely. Fortunately, the open space next to the subroad bed is unoccupied so the fix is as easy as adding a small bit of plywood. Because I want the two pieces of plywood to be the same level, and because of the difficulties with using screws to attach a narrow piece of plywood into the side of another piece of plywood, a strong wood glue is the preferred solution.

In the center of the photo is a bit more challenging of a problem. A short length, about 15" of curved 1/2" plywood has been put in place to serve as subroadbed for the middle tier return track. The wood had to be this short because the subroadbed on either side of it is 5.2mm lauan in due to clearance requirements underneath. Alas, the short length means only two support piers are available, and two is simply not enough to force the plywood into a level shape. I've found you need at least 3 piers, no greater than 12" apart.

So, the subroadbed was bowed up on both ends. The solution was to find a piece of 1 1/2" wide plywood with one very straight edge (I had some left over from the first staging effort), and attach it to the under side lengthwise against that straight edge. It's a slightly delicate operation as this type of wood is prone to splitting. I used 5/8" #6 screws, pilot holes, and of course C-clamps to line everything up. The end result, though, is indeed level and even.

One can avoid such problems with a subroadbed technique known as Spline Roadbed, an example of which is at the link. It requires extra effort in construction but done right it assures very even surfaces. Advocates also point out that it can be used to create natural spiral easements (transitions from straight a.k.a. tangent track to curved track).

However, in addition to the extra time and cost involved with creating spline subroadbed, most spline methods require extra vertical clearance (however, the specific spline method shown at the link above definitely minimizes this disadvantage).

For now I seem to be able to create level plywood subroadbed through careful construction, and in terms of spiral easements I use another technique that gets good results (to be described later). However, spline roadbed is a good method to be aware of, and I may decide to apply it to some situations later in the layout.