Tuesday, April 19, 2016

Truck and wheelset modeling

In a previous post about my new shop track alongside the roundhouse at the town of Shumala on my layout, I mentioned the installation of a wheel track, as a radial track coming off the turntable. (You can read that post at the following link: http://modelingthesp.blogspot.com/2016/03/a-shop-track-for-shumala.html .) This present post is about modeling what goes there.
     I will begin with prototype wheelsets. Many modelers seem not to realize that the end of a railroad axle is the surface on which bearings ride, and is called a “journal.” (This is why both roller bearings and solid bearings are properly termed “journal bearings,” because they ride on the axle journal.) The photo below (from the National Malleable and Steel Castings Co.) shows a wheelset being removed from a truck, and the journal at the near end of the closest axle is evident.

     Prior to entering service, a newly mated pair of wheels and an axle are machined,  to achieve exact journal dimensions. If necessary, the wheel tread may also be machined to correctly contour the tread and flange. Freshly completed wheelsets sometimes have axles or wheel faces painted, as in this contemporary view.

     Our model wheelsets, of course, almost always have axles with pointed ends, intended to operate with only the point in contact within a conical hole in the sideframe. But the axle ends on this kind of wheelset do not look much like the prototype. Without naming any sources, compare the axle ends of this model wheelset with what you see in the photos above:

Also note that although the tapered center of the model axle here looks good, the prototype photos above all show an almost invisible taper for axles. Prototype drawings for axles, which show a rather gentle taper, can be seen in any volume of the Car Builders’s Cyclopedia over many years.
     The foregoing photos should suffice to demonstrate why modelers should not employ most model wheelsets as scenery, because of the pointed ends on our model axles. Instead, there is an easy solution already available: the Tichy package of wheelsets used with their flat car (converted to a wheel car). The wheelsets alone are available from Tichy as set 3004, eight axles and eight pairs of wheels, which can be assembled or used separately as stored parts. Here is the same model wheelset shown above, with its pointed axle ends, alongside one of the Tichy wheelsets. Note the difference in axle taper, and in wheel tread width also.

The “standard” model wheel tread in HO scale has had a width of 0.110 inches for many years, and that is the tread width of the pointy-ended wheelset shown above. What we now call “semi-scale” wheel treads are 0.088 inches wide. Prototype freight wheels have a rim thickness of 5-23/32 inches, which is 0.066 inches in HO scale. The Tichy wheels shown above are 0.066 inches wide, and though many modelers immediately say, upon seeing one, “it’s way too narrow,” in fact it is an accurate prototype wheel width.
     Another point about the photo of the Tichy wheelset is the journal. What’s critical for using these parts as models is that nearly all prototype wheelsets have a bright, metallic surface on the machined journal, with a rusty color on everything else. The Tichy set comes entirely in a good brownish-red color. I masked the axle centers and painted them Gloss Aluminum, Tamiya color  TS-17, and then touched up the axle centers as well as the wheels with Burnt Siena and related acrylic colors to produce a realistic look. That’s what you see above.
     With these points in mind, I have made up several wheelsets for my wheel track at Shumala. I am not stopping there, because I want to show a truck being worked on, but for now, these Tichy wheelsets show the kind of look I think we need to model when we show these items as scenery.

These wheelsets are not completed, because the color needs more work; this reddish color is the as-molded color as it comes from Tichy, but I want to get a browner shade on these wheelsets. Still, you can see the general appearance that will be created. Note that wheel treads are not shiny, indicating that these are new wheels, not yet in service.
     I will comment further about wheelsets and truck modeling in a future post.
Tony Thompson


  1. When stored on rip tracks, plain bearing wheelsets were often covered by rags and/or wood strips wrapped around the journal much like the saves of a barrel.

    Steve Lucas

  2. typo---"much like the STAVES of a barrel."

  3. You are right, Steve, and the same was sometimes true even of wheelsets which would receive roller bearings. The journals are the same.
    Tony Thompson

  4. I noticed that your wheels have ribbed backs. How late in time would these be appropriate?

    -Jack Shall


  5. Ribbed backs were only on cast wheels (though not all cast wheels had ribs), and though cast wheels were a decreasing part of wheel production after 1950, certainly they were commonplace throughout the 1950s. I'm not sure how late it would be reasonable to include them.
    Tony Thompson