This is one of the trickier parts of building the layout, installing the curves with risers. Cookie cutter method has one major drawback. The curves are "springy" and like to bank naturally. This causes problems when you are trying to install the "supposedly straight" risers.
Before I got started, I checked all the risers that I made and sanded the tops flat and smooth. Then, I inserted the risers at the ends of the curves at 1.5" high, with 1.5" being measured from our constant zero point which is the top of the section joists, going to the top of the roadbed section. It is key that you keep and know your zero point throughout the installation of the roadbed. I thought that 1" might be a bit steep when calculated out...
1" rise (1.5" - .5" high on plywood) over a 21" run = 4.76% grade.
And that is steep, but not too steep. Still, I'll probably drop it back to 1" high roadbed.
1/2" rise over a 21" run = 2.4% grade. This is much more acceptable and realistic looking.
Here is the riser set at 1.5" and from this photo you can see the racking or curving of the plywood. I've got a bigger problem here than the plywood. The riser is right where the angle brace that supports the benchwork is located. Since we are on a joint between sections I can't go on the other side. I'll have to noodle this problem. Ideas welcomed!
The 1.5" looks ok here, and probably would be, but I'm going to drop it down.
The outer curve goes to the lop level. The clearance must be 3.5" at minimum for On30, and this riser is set at 4.5" which is too high. We'll take it down a notch.
When putting in risers I always clamp the risers in and leave them for a day or two to let the curve of the plywood relax. The riser in the back is the right height, but the roadbed is rising above it naturally.
Here you can see one of the risers close up and well mounted, with two others clamped in the back.
The riser top is level but the roadbed wants to spring toward the middle.
After some minor adjustments the curve is looking more natural. Splitting the Rise is where you start off with the tracks at a level above zero, and then lower one track while raising the other track. This allows for an overpass in a much shorter distance.
This square has a handy level on it. I can tell how high the track is, and how flat it is. A curve can lead to a tilted roadbed if you are not careful.
We'll let these sit overnight while I go find a wye, and then come back and adjust them. We also have to figure out what to do with the angle brace. Always problems to solve! Or opportunities!
1. Cookie cutter roadbed curves have a tendency to rack or twist, so special care is needed during installation.
2. Grades are calculated by this formula: RISE/RUN and be sure both numbers are in the same measurement such as inches.
3. Grades should preferably be about 2-3% in HO or On30, and not to exceed 4% except in a very short distance. Even some of the shortest trains can pull up a 4% grade without modification.