I provided the prototype background on Southern Pacific whistle post design(s) over the years in an earlier post, from last December, which can be viewed here: https://modelingthesp.blogspot.com/2019/12/southern-pacifics-whistle-post.html . Now I want to address modeling.
Since I model 1953, I want to use the single-board design in force in those years, as shown in one of the photos in the post just cited. The letter “X” on the post is about 8 inches wide, and a suitable post would be a 12-inch wide board. This is quite easy to do in HO scale, using Evergreen styrene strip of 2 x 12-inch scale size.
I had some concern that during layout operation, a styrene post this thin would be pretty vulnerable to careless elbows, etc. One approach to that issue would be to realize that since the model post is very simple to build, one could merely make a whole bunch of styrene posts and replace whenever necessary. But some locations are vulnerable enough that I decided to make some posts out of brass.
I decided to go ahead and use the actual letter “X” from the later SP drawing, CS-1360, that was shown in the previous post on this topic (first paragraph above). It is interesting that it is slightly asymmetrical, with the part above the crossing of the two strokes slightly higher than the bottom part. Well, that is what SP did. Here is a view of it:
For my HO posts, this graphic is simply reduced to fit the model post, printed out on paper, and glued to the post, whether styrene or brass, using canopy glue.
I made one brass post by sawing a scale 12-inch wide strip out of 0.032-inch thickness brass sheet, but it is easier to use commercial 1/8-inch wide brass strip. In HO scale, this is close to 11 inches wide. The strip I purchased is 24 gauge red brass (15 percent zinc instead of the 30 percent found in yellow brass). Sheet of 24 gauge is 0,0239 inches thick, or in HO scale, very close to 2 inches. This is pretty suitable for modeling a 2 x 12-inch post in HO.
Shown below are a styrene post (with its back side already painted brown, as the prototype did) and below, a brass post, somewhat shorter. Both are long enough that they can meet the SP specification that the post top should stand 6 feet above the ground.
I have at least one well-protected location where a styrene post will probably survive, so made up one for that location and installed it. The cliff alongside this location should mean that careless elbows will not wander into this area. As the prototype drawing specifies (see that drawing in the post cited in the first paragraph of the present post), the location is 13 scale feet from the track centerline, and is in the ballast shoulder, not down in the ditch.
To illustrate a more exposed location, the view below shows one that is close to the layout edge along the aisle, at right. Here I installed a brass post. We will see how this one does in service!
In most operating sessions on my layout, crews usually do whistle for crossings, and I am glad to provide them a reminder to do so, in the form of a prototype post.