Wednesday, April 12, 2023

Better model dome platforms, Part 2

A couple of years ago, I showed the background for the need of better dome platforms on those of our model tank cars that should have them (you can see that post here: ). 

That post, which introduced a dome platform kit from Yarmouth Model Works, was a follow-on to earlier efforts of mine on this topic (for example, this post: ), efforts to replace the Athearn platform.

The prototype platforms, as I’ve shown before, have very light-looking components, completely unlike the long-familiar Athearn platform on what Athearn calls a “chemical tank” car.  I show one below, to emphasize the extremely fat corner posts and oversize height and length of the platform. It’s not only oversize for HO, it is actually a bit oversize for S scale (except for the posts, which have no known equivalent).

There are a number of alternatives, as I’ve often mentioned on this blog, but today’s topic is further work on a really nice product. Yarmouth Model Works, in their kit YMV-360,  offer an excellent fret that can be folded up to make a really far better platform. My introduction of the kit is in the post linked in the first sentence of the present post.

In that post, I showed a Yarmouth fret folded up for use, and indicated I was starting on a couple of tank cars to use these platforms. One obstacle for me is that both of my project tank cars have fairly large conventional expansion domes, not the smaller, slender valve bonnet that is found on pressure tank cars. That’s a potential issue because the Yarmouth frame is hardly bigger than such expansion dames, making the preparation of the platform floor challenging.

Or so I thought. Like so many things, I worried about how to do it for far longer than it actually took to do it. First point I recognized was to use fairly thin styrene sheet for the platform, to make it easier to cut a round hole in a square platform. I used 0.020-inch thick scribed sheet. I chose that because in the prototype, until 1948, most tank cars has wood planking on the dome platform, not the metal grid material familiar in later years.

Second, I didn't have a simple way to lay out the dome diameter on the styrene platform. Or so I thought. Both of my domes are less than 0.75 actual inches in diameter, and I realized that that is just about the diameter of a U.S. five-cent coin. So I could use a nickel coin for layout, and cut inside of its diameter.

Then I played around with the folded fret and the new styrene platform, and immediately realized that the flimsy-feeling platform, which I was worried would be delicate, actually can be quite strong: if you just glue it to the platform, it’s held square and flat. Nice! Below, the platform is just resting on the frame, not yet glued. You’ll notice that the nickel coin happens not to be in the center of its platform.

The usual practice on tank car dome platforms was to orient the planks crosswise to the car, so I did that also. Then I glued the fret around the outside of the platform, using canopy glue. 

The Yarmouth recommendation is to use 0.015-inch wire for the handrails. However, this really is not correct in prototype terms. Both the side handrails on tank cars, and the handrails on dome platforms, were always specified as 1-1/4-inch nominal iron pipe size. But this is just a nominal dimension, not the pipe diameter. As you can readily discover on the Internet, the outside diameter of such pipe is in fact 1.66 inches, close to 0.019-inch wire in HO scale. 

But the arrangements of the Yarmouth parts are for the 0.015-inch wire, so I decided to build my first shot at the project that way, and made sure the platform holes were fully open, clearing them with a no. 78 drill. I began by installing the plain horizontal handrails, using phosphor bronze wire from the Tichy Train Group.

Here the railings are attached with canopy glue, which I’ve learned is quite tenacious. With those side railings in place, I experimented with how to make a consistent curvature in the railing pieces that are on either side of the platform entrance. I used the sharpened part of a wood pencil for a mandrel, and once I had four reasonably identical parts, attached them also with canopy glue. They were made oversize, and the excess lengths simply clipped off after the glue had set. 

You can see above that the railing parts aren’t entirely symmetrical, but this was a learning experience. Perfection not necessary in this case because with the platform finished, I painted it dark gray for this tank car, and dry-brushed it with Polly Scale “Grimy Black.” Moreover, please compare the photo just above with the Athearn monster shown at the top of the present post.

Here is the installed platform on the destination tank car, with side ladders yet to be installed.

For purposes of comparison, here is a similar-size tank car (though insulated), built in 1940 by American Car & Foundry (AC&F builder photo, courtesy Ed Kaminski) and leased to the Heyden Chemical Company. Note that the platform railings look a little heavier than the model above, doubtless because of the undersize wire used with the Yarmouth parts. But the general impression of the model platform is quite good.

Overall, these Yarmouth parts are really nice, and I will be building more of them for others of my tank cars that need a better platform.

Tony Thompson

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