Plywood Madness…
5th September 
no responses · Modelwork Continuing to resurrect posts from the old blog, this one presents a technique I use for making running boards on 1:48 locomotives. The running boards for the 1:48n3 Lima Shay documented in another series of posts here will be made using this technique. Running boards are often easily damaged, especially on operational models that receive a certain amount of handling. As I believe in using wood to represent wood, I make my running boards from Boxwood, but they need to be a little stronger in order to stand up to the occasional handling. To strengthen them I make them out of Boxwood and brass plywood. The picture below shows two sample plywood running board planks. You can just see the brass layer in the piece held in the tweezer clamps.
Boxwood and brass plywood
Essentially I sandwich a piece of .010″ T. brass sheet between two .015″ T. layers of Boxwood. The overall scale thickness is approximately equal to 2″ which is close enough to represent the planks used to form running boards on the prototype.
The trickiest part is ripping the .015 T. boxwood strips. I do this in a Preac Micro-Precision table saw using a sharp blade. One of the beauties of Boxwood is the ability to precisely cut and machine stock which due to the dense nature of Boxwood, is dimensionally stable. These pieces are cut to the desired thickness but cut oversize in width and length. I then cut .010″ T. brass strips to the same width. Then it’s a simple matter of cleaning all the mating surfaces and gluing up the three layers. I use an ACC cement and let each assembly cure under pressure. Once completely cured each piece is trimmed to final width in the Preac. The outside edge is covered with a thin strip of Boxwood trim to hide the brass edge and replicate the usual edge piece.
Mounting the boards is fairly straight-forward and I’ll cover that in more detail in the Shay construction series. Since they mount onto brass brackets that extend out from the frame rails, I mill a slot in the underside of the running board through the bottom layer of Boxwood to expose the brass sheet. I then glue the running board to the bracket again using ACC. A couple of small NBW castings which double as locating/reinforcing pins running through the boards and brackets complete the assembly. In this way the running boards can be finished separately and attached to the previously painted locomotive chassis.