Monday, October 4, 2021

Completing a turntable

 About 35 years ago (!), I built a Diamond Scale turntable for my layout, then located in Pittsburgh, PA. I liked the kit and felt that the resulting turntable looked really nice. It worked fine, too, though I later removed the hand-crank mechanism as part of moving the layout to California. But the turntable itself actually never got finished. Many visitors over the years have seen it looking like this: 

The protruding ties, eye-catching because they are unfinished, are intended to support the walkway and handrail along both sides, and a cab for the table operator on the longer ties at lower right. I had stalled in progress on the project because of the kit’s directions for making the handrail. Here’s the drawing from the instructions:

Not only did this look like a difficult and fussy step to complete, keeping all posts parallel and vertical, but also the result was intended to be a wooden handrail structure, and with huge posts (the ties are about 10 x 10 scale inches). One could of course use smaller posts, but there’s a bigger question.

And that question is, what did Southern Pacific turntable handrails actually look like? In particular, were they like the intended result of the Diamond Scale kit? Was there a post at every long tie? How tall were those posts? and so on. Since my layout models an SP branch line, the turntable ought to reflect SP practice. 

The first answer is that SP turntables were definitely not all the same. Certainly there were wood handrails on some turntables, but particularly near and after World War II, quite a few of them had handrails made from pipe. I decided to examine some examples more closely.

I will begin with wood handrails. A wartime image at Dunsmuir, below, shows a Class F-5 2-10-2 on the turntable, and the handrails are clearly shown (Eastman photo, Shasta Division Archives), even it it isn’t a good view of any of the locomotives. This is certainly like the intended Diamond Scale handrail.

A second example, also a wartime image, is the turntable at Eugene. It’s a fine view of the turntable, clearly with a wooden handrail, with a longer span between posts than the Dunsmuir turntable shown above. It’s an SP photo, John R. Signor collection. And incidentally, also a nice view of the operator’s cab, which is quite similar to the Diamond Scale kit cab.

At this point, even though I was aware that many SP turntables did not have wooden handrails, I spent a little time figuring out how I would modify the Diamond Scale instructions to build a wooden handrail on my model turntable. My idea was to clamp something square near the ends of the ties, so that the posts could all be aligned, and individually squared up. Here’s a view of that arrangement, using a 1/4-inch square piece of hard balsa.

You can just see the ends of the long ties protruding beyond the edge of the balsa strip. I believe this method would yield posts well aligned, and thus ready to accept the longitudinal handrail boards that are seen in both the Eugene and Dunsmuir tables. The walkway could then be added inside the posts.

It was tempting to proceed with this process, just because I always like to build kits (mostly) as they are intended to be built. But as mentioned above, there were plenty of examples of SP turntables that did not have wooden handrails. I will take up those examples in a future post.

Tony Thompson


  1. What is "hard balsa"? Common sense can lead me to an answer, but is it commonly available, and is it desirable as a scratch-building material? Thanks!

    1. This is a term that I remember from my days building wooden model airplanes -- a long time ago, so maybe not a term still in use. It refers to a _relatively_ hard balsa. Balsa wood does vary considerably in hardness from piece to piece, and maybe the harder end of the range was sorted to be sold under that name. Whether that is still done, I don't know.

      As to use, I do use some of my stock as bracing inside structures.
      Tony Thompson