While the leg team and the L-girder team were wrestling with their components, my third class of seventh graders would construct the frames that sit on top of the L-girders. Four removable layout sections, three at 8’ and the fourth somewhat shorter to fit into a niche behind the main entry door. The design of each of the frames was based on a simple rectangle with cross pieces 16” o.c. but to accommodate the undulations and protuberances of the track plan no two frames were exactly alike.

Call me crazy, but I had plenty of the cheap 1x2 furring strips so that’s what I designed the frames around. I fully understood that my L-girders were not going to be perfectly flat and level so if we used the floor as a surface plate and tried to build the frames close to square we wouldn’t make things much worse and might even end up canceling some of the irregularities in the L-girders when the parts were assembled.

My layout building experience is not extensive, but I’ve never found it practical to use an off-track reference benchmark. I build my benchwork low enough to be below the lowest part of the landscape (exceptional canyons notwithstanding) and adjust risers as the roadbed is being installed by measuring up or down from a carpenters level that has one end resting on the roadbed.

This way I can more or less ignore imperfections in the lines of the benchwork, which works out well under these particular circumstances!

I used my hand-drawn sketch of the proposed track arrangement to determine the dimensions of the panel frames and made quick sketches of each frame showing the critical dimensions. Only one of the panels would be a perfect rectangle so I decided the whole class would build that one together, then I’d divide the class into three smaller teams and have each team take on one of the remaining oddball panel frames.

I drew the following sketch under the document camera and talked my way through it as I drew so that students could ask questions when they didn’t understand something. They had seen the other sketches showing the general arrangement of things and I’d discussed things like “backdrop” and “fascia” but it was all pretty abstract for them I’m sure. In particular the meaning of the detail of the spacer blocks to provide a recess behind the fascia for turnout control mounting was not obvious, but I told them they didn’t need to worry about it for now as we wouldn’t need the spacer blocks until much later.

My students were already familiar with the concept of a “material take-off” for estimating a job. Some weeks earlier I’d given each student a brand new unsharpened yellow pencil and asked them to make a list of everything needed to make it, including a quantity for each item on the list. That’s an extremely fertile exercise which broke open many new ways of thinking for the students, and was the basis for a series of projects involving surface area and volume and continuing on all the way up to manufacturing economics and, you guessed it, material transportation calculations. The students were already thinking about putting a pencil factory somewhere on the layout.

After some study of the sketch they correctly determined that we only needed two different parts to make the frame: two 8’ long 1x2s and seven 13-3/4” long 1x2s. I asked them to double check my calculation for the length of the cross members by subtracting the actual width of a 1x2 from 16” three times. Now this class had the opportunity to discover the surprise of nominal lumber dimensions just as the others had.

These cross members needed a bit more cutting precision in length and squareness than the legs or L-girders, so I showed the class how to measure and mark with a combination square and how to use a maple miter box and back saw. They expressed some consternation when I showed them how to set up the saw so that the set of the teeth met the cut mark on the workpiece.

“Can’t we just cut on the line?”

“Of course you can, but you’ll end up with a piece that’s not the same length as you went to the trouble of calculating and measuring. Here’s where attending to precision takes just a tiny bit more effort but gives much better results.”

We set up another rotation to give everyone experience with the saw and soon had everything we needed for our first frame ready to assemble. 

Jeff A.