Sunday, May 21, 2023

An SP diesel fuel tank car, Part 2

In a previous post, I showed the prototype paint scheme I wanted to reproduce on a model car, a corrected and upgraded Athearn “42-foot tank car.” I also showed a couple of features of how I do that, and showed a model project that had gotten stalled because of an error in construction. You can see that post here: .

I decided to correct the wrong-side removal of a dome walk by reversing the location of the dome-top safety valves, which should be at the B end of the car. That end, of course, is determined by the brake gear on the underframe, but the remaining dome walk needs to be on the left-hand side of the car, as viewed from the B end. So here is the model, B end now at left, after slicing off and replacing the safety valves. The two round black scars are where the safety valves were located before removal and placement on the other side of the manway.

My next task is the handrail. As I have shown previously, one can readily bend a new handrail from brass wire (see my project description at: ).  That previous post also describes how to make a “pipe union” to join lengths of handrail, using stainless steel hypodermic tubing or brass tubing.

In making tank car handrails, one first needs to recognize, to repeat a point made in the post just cited, that prototype handrails were made from nominal 1-1/4-inch iron pipe. And that, as any table of nominal pipe sizes will tell you, has an outside diameter of 1.66 inches. This corresponds to a hair over 0.019 inches in HO scale.

Since the convenient packages of wire from Detail Associates went away, I have been using K&S no. 8159, which conveniently contains 12-inch lengths of 0.020-inch wire. That length is almost the circumference of an SP tank car in HO scale, so the length matters. In the photo below, you can see partial progress in bending the wire to the necessary shape: not there yet, but getting close.

It takes lots of trial fitting, adjustment of bending, more fitting, and so on, to get to a satisfactory part. This is one of those tasks I only undertake when feeling like I have lots of patience. Below you see the main handrail ready to attach, and the short piece that will complete it (length not yet finalized), along with the short piece of tubing below the railing that will be the pipe union.

But before adding the handrail, I wanted to complete painting. As shown in two prototype photos of these cars in service on the SP (included in the previous post, link in the first paragraph of the present post), these cars had black bottom sheets and black handrails and ladders. I went ahead and masked the upper part of the tank body seen above, and sprayed the bottom sheet with Tamiya Matte Black (TS-6). 

But before proceeding with the handrail, I turned my attention to the underframe. I explained in some detail previously how I re-work this Athearn underframe (see: ). 

This frame is in two parts. To begin, I fitted the parts together, and drilled through the post in the coupler pocket, starting from the handy hole in the top of the underframe, and right through the pocket cover underneath, so that I can tap for 2-56. 

Then I cut the coupler pocket covers off. I want to make those removable, not part of the underframe itself. Then I glued the bottom part of the frame to the top. With that attached, I used canopy glue to add some brake rodding to the molded-on levers, and some piping to the triple valve (a little hard to see below; you can click on the image to enlarge it if you wish).

The Athearn vertical-wheel handbrake stand represents a very unusual arrangement for a tank car of this era. I fill the hole where it is intended to be placed, using modeling putty. That’s what you see at the far right end of the view above. I will replace the Athearn part with a wire staff and soldered-on brake wheel.

I'll continue with completion of this tank car model in a future post.

Tony Thompson

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