This post is the beginning of a build log for a new trestle on the layout. It will be 560 scale feet long in 1:20.3 scale. That’s nearly 28 actual feet. The entire trestle is on a 2½% grade. I’m building it with five consecutive 112 scale foot long segments (about 5½ actual feet.) This length is convenient for working at my 6 foot long workbench.
The first segment is a slight (60 foot diameter) curve to the left. The next two segments are tangent (straight.) The final two segments are a slightly tighter curve (36 foot diameter) to the right. Basically it is a very long bridge on a very gentle S-curve.
There are 36 bents spaced 16 scale feet on centers. The bents are made from 12” x 12” posts and sills, with 12” x 14” caps. Diagonal bracing is 3” x 10” boards. Stringers are 8” x 18” timbers cut to 16 scale foot and 32 scale foot lengths. Three stringers make up each beam. Two beams are spaced ½ actual inch apart to support the ties. 1/8” x ¾” aluminum strips are sandwiched between the stringers on the tangent segments.
There are seven different heights for the bents, ranging between 4 and 14 inches tall. Most are single story, although there are a few two story bents near the center of the bridge. Here are the range of heights.
Here is the completed stack of bents.
All of the joints on the bents were made with Titebond III wood glue and various length pins with a pneumatic Grex 23 gauge pin nailer. On the two story bents, the posts of the second story are connected to the intermediate sill with staples. You can see the staples in the following photo.
Here is the pile of 8" x 18" stringers.
Here is a pile of 6 foot long 1/8" x 3/4" aluminum strips to be used for strengthening the tangent segments and keeping them perfectly straight.
Here is how I sandwich the aluminum strips between the wood stringers. I use “Gorilla” brand construction adhesive in a caulking gun and clamp the glued-up stringers between a couple of 1" x 2" boards until the glue sets. Clamps are like locomotives … you can never have too many.
In the next installment, I will tackle the curved segments and start building-up the deck.
More to follow,
Bob