Thursday, April 18, 2024

My latest column in MRH

As a regular columnist in Model Railroad Hobbyist (the “Getting Real” series of columns by several writers who take turns), my latest column is now appearing, the 27th I’ve written for this publication. It’s about “Modeling Perishable Shipping,” emphasizing the layout details that reflect handling of perishables, and also a little about operations. It’s in the “Running Extra” part of the April 2024 issue.

There are two main aspects I am trying to model (and that I described in the article). One, the loading of the cars (what can be seen outside the car), and two, ice refrigeration, both pre-icing (defined in the Protective Perishable Services tariff as filling the ice bunkers of an empty car before spotting for loading) and initial icing (again, tariff language for icing a loaded car before departure, at the nearest ice deck to the loading point).

For the loading part, we are limited in HO scale to what we can suggest from outside the car. On the loading docks of my packing houses, I often have a stack of shipping crates visible, as in the photo below at the Phelan & Taylor Produce Co. dock on my layout in East Shumala. The suggestion is that these crates are ready to load.

In addition, I spent a little space in the article describing the use of field boxes, in which harvest is brought to the packing house. A few of these are shown at right in the photo above. This is the easiest way we can depict the harvested perishables. 

Icing, of course, is a familiar operating possibility on model railroading. Most of us cannot begin to model a prototype-size mainline icing station. These ice decks were often 80 to 100 cars long. If I recall, the largest model ice deck I’ve seen is at the La Mesa Club’s Tehachapi layout in San Diego, and it’s about 30 cars long. In HO scale, that is really big: 30 car lengths, at nominally 40 feet per car, is 1200 scale feet, or nearly 14 actual feet.

I have modeled a far smaller facility, typical of small towns, only a two-car deck, and located at a private ice company. Such companies usually did not have the capacity to freeze 300-pound ice blocks for reefer icing, and accordingly the reefer ice was shipped in. (That made it what PFE called an ITP, an Ice Transfer Plant.) Below I show an Ice Service reefer about to be spotted at the loading door in the ice building (at right). Note that its ice hatches have been blanked off; the ice bunkers have been removed for more loading space.

Meanwhile, on the deck, I’ve modeling the workmen using the two typical ice-handling tools. Below, the man at left holds a “bident,” a two-pronged fork used to chop the ice into smaller pieces, and the man at right holds a “pickaroon,” with a point for pushing ice blocks, and a hook for pulling them toward you. Note that the ice is not clear. Modelers who have clear ice on their ice decks need to sand it so it is at most translucent, which is how ice on real ice decks looked.

The photo above is from an earlier period, before I added the metal sliding tray that the workmen used to slide ice out along the deck, and also added some smaller ice chunks. In the photo below, you see open ice hatches, with the plugs on the underside of each hatch cover.

Lastly, I touched on the issue (mentioned above) of pre-icing and initial icing. A couple of the packing houses on my layout don’t have their own pre-cooling capability, and must receive pre-iced empties (all the other houses, since they do pre-cool their produce, receive un-iced empties). 

This can be indicated in a waybill, as you see below, in the line just above the cargo description. The mention of Section 2 under “CPS” (Carrier Protective Service) means “standard refrigeration,” that is, ice in the bunkers.

My purpose in this particular MRH article was to emphasize how one can model perishable shipping, from harvest and loading, to icing, to long-range car movement. Hopefully I provided a few insights that might help modelers decide what they want to include, or can include, and how to model it.

Tony Thompson

Monday, April 15, 2024

Trackwork wars, Part 13

I'm pretty much done with the previous challenges described in this series, but one more interesting one did surface during my last operating session. There’s an old saying, that using a layout inevitably breaks things. Well, this was another demonstration of that adage. (For previous series posts, see for example: ). I’ll describe the issue because it was not a simple problem.

The interesting aspect of this particular problem is that it involves several different things. First, it’s a really old switch. dating back at least 40 years on the layout. (It’s one of the Russ Simpson “Scale Model Railroad Trackwork” No. 5 switches, wonderful components, and if I had managed to buy more of them, I would have used them throughout the layout. The point rails are all in one piece, from frog to throw bar.) 

Second point, I had had problems years ago with electrical performance of this particular switch, which relies on the contact between point rails and stock rails. I had solved this many years ago, by adding the contacts of a micro-switch under the layout with an operating wire up through the layout and into the hole in the center of the throw bar. Movement of the points moves the wire, which moves the contacts to the appropriate connection.

In the photo below, the switch point rails can be seen to be joined by a brass strip, to which they are soldered. In the center is a rivet which attached the brass strip to a plastic throw bar underneath everything. Or there was. It broke at the rivet, and the two pieces are lying parallel to the track, just above the points. The throw bar in turn has a hole at one end (at left in the view below), which was the connection to the (un-mounted) Bitter Creek ground throw which is at upper photo center.

My first shot at fixing this was to try and glue the left half of the throw bar (as you see it above, at left), back into place under the brass connector strip. This worked, but didn’t survive many throws. It was clear I needed to make an entire new throw bar.

I chose some Evergreen scale 6 x 10-inch styrene strip, and cut a length equal to the original throw bar. I then rounded the corners and drilled two holes, about no. 55, one in the center (to accommodate the wire activating the micro-switch contacts below the layout) and one near the end, for the ground throw. And I painted it black.

It wasn’t easy to slip the new throw bar under the switch points and over the center wire, but I got that done. There was a slight bend in the frame of the Bitter Creek throw, so I temporarily replaced it with a Caboose Industries throw, just to get it back in service.

This works well enough, and for now will remain this way. I was glad to be able to keep the successful electrical arrangement on this switch, while replacing the throw rod. The test will come, of course, when visitors operate through this switch, as they will repeatedly for almost any switching task at Shumala. Fingers crossed.

Tony Thompson

Friday, April 12, 2024

Adding California condors to the layout

This may seem a rather exotic idea. But I’m doing it. Probably many readers have seen layouts with kites in the air, or airplanes; I can remember visiting a layout with a blimp in the air. Well, why not birds? Of course, nearly all bird species are quite tiny in HO scale. But the California condor, with a wingspan of up to 10 feet (the largest in North America) is a potential exception. As explained below, I decided to give it a try.

These birds are mostly black, but like most vulture species, have a bare head. They also have elongated white patches on the underside of the wings. Below you see a California condor in Zion National Park (Phil Armitage public domain photo, 2007), with tracking devices visible on both wings. 

The California condor, as many readers may know, was on the verge of extinction, with only 22 birds alive in the wild, when conservation efforts began in 1987. Capturing wild birds for breeding, nurturing of chicks, added protection for birds released into the wild, and thorough monitoring of health of the population in the wild, has been a notable success. 

Today there are estimated to be 558 of these birds in the wild, and in addition to their last original range in the coastal mountains of California, they now are successfully ranging and breeding in many other areas, including the high Sierra, southern Utah and northern Arizona, and both Big Sur and Pinnacles National Park in California. Introduction of condors has recently been accomplished in Redwood National Park in northern California, and in northern Mexico. For more, see: .

The Miniprints offerings (see their line at: ) include a California condor in their extensive line of 3D-printed birds and animals in HO scale. The origin of this is interesting. My friend Seth Neumann contacted Bernard Hallen at Miniprints and asked if he could make a condor. What he apparently did was scale up a vulture, and of course condors are in the vulture family, so these are certainly close enough in HO scale. 

Seth bought some, painted them, and was kind enough to give me two pair. There are two standing birds and two in flight (shown below both from above, with all-black wings, and from below, like the prototype photo above). The model wing span is about 1.25 inches, which translates to about 9 feet in HO scale, certainly reasonable.

So how would these bird models be installed on a layout? They are soaring birds, so should be seen in a hilly area, and obviously the flying ones have to be in the air. For the standing birds, I luckily have a perfect rock outcrop above my layout town of Ballard, so one of them fits nicely there.

The thought of the condor, brooding above the town, inevitably brings to mind one of the great personalities that Charlie Brown’s dog, Snoopy, assumed: the “fierce vulture” in a tree. Not sure the condor looks a great deal like Charles Schulz's drawing (internet image).

The flying condor I decided to attach to a wire, allowing it to appear to be actually “in the air” above the hillside. I used 0.015-inch brass wire. I first tried it out unpainted, attaching it to the underside of the flying condor with canopy glue, and sticking the wire into the hillside above Ballard. You can readily see the wire in the photo below, because it is still shiny brass color.

I then spray-painted the wire medium gray, which seemed like a sufficiently neutral color to make it disappear. And it does, from most angles. In fact, the condor is now a little hard to photograph so that the wire shows. After trying several different perspectives, I did come up with one where the wire is visible. But I will repeat that viewing from the layout aisle, it’s pretty hard to see the wire.

This was a fun addition to the layout, and of course full credit to Seth Neumann for both the idea and the models. But now that they’re available from Miniprints, anyone can do the same. I’m glad to do something to honor the return of the California condor to the wild, even in HO scale.

Tony Thompson

Tuesday, April 9, 2024

Operating sessions 88 and 89

This past weekend I hosted two operating sessions on my layout, which happen to have been nos. 88 and 89 on the layout in its present form. They were especially important to me because of the work I have been doing to correct past problems with trackwork (as described, for example, in this post: ). I wanted to give the new track a full workout. 

Of course, an important preliminary job was to clean up the work area (shown in the post just linked) and restore structures, etc. to their rightful places. And you may note that the new switches are still not ballasted, until I get all the gremlins out of the trackwork.

The first day’s session was manned by Steve Van Meter, Lisa Gorrell, John Rodgers, and Seth Neumann. As crews almost always do, they elected to do half the session on one side of the layout, then switch over and do the second half on the other side from where they started. The photo below shows Lisa (at left) and Seth hard at work in Ballard, with Seth acting as conductor at this point. He’s probably identifying where he wants the engine next.

At the same time, the photo below shows Steve (at left) and John getting through the tasks at Shumala, mostly yard work here at the beginning of the session. It looks like Steve is conducting, since he is holding the paperwork. The clock on the wall shows layout time, not rest-of-the-world time, though it is a 1:1 clock; this permits us to operate in a specific segment of the prototype Southern Pacific timetable for the Guadalupe Subdivision of Coast Division.

Although a couple of layout elements needed repair during the session (switch points coming un-soldered, etc.), generally things worked all right. Here is a photo of the Santa Rosalia Local, ready to return to Shumala with the cars it has picked up during its run.

I should mention one other “feature” of the operating session, which I will explain, since the background is known to a very small number of people. Years ago at the annual Cocoa Beach meeting (for a few words about this year’s meeting, see: ), several of the early arriving attendees would repair to Mike Brock’s house and operate on his very nice Sherman Hill UP layout. Some years back, Bill Schneider (an O&W modeler) slipped an O&W coal hopper under the coal dock on the layout, understandably to Mike’s mystification and the great amusement of everyone else. The hopper remained there ever since. 

This year, with Mike having passed away last year, some of us were offered the chance to receive a freight car from Mike’s layout. I immediately seized the O&W hopper, and I intend it to surface from time to time on my layout, as a kind of memory of Mike’s layout. Bill knows I have the car, and seemed to feel it was going to a good home. Here is how it looked this weekend, with missing waybill as usual:

All in all, a pretty good session. Several things I wanted to ensure would work well for the upcoming ProRail event did work well. The new trackwork unfortunately is still not completely right, though better than it was. I will continue refining it. 

And I keep reminding myself of my friend Paul Weiss’s important observation (which he named “Host Flaw Hysteria”): the host feels like 5 percent of the layout misbehaving ruins the entire session, while the visitors realize that 95 percent worked fine, and pretty much overlook that 5 percent. May it remain true.

Tony Thompson

Saturday, April 6, 2024

Trackwork Wars, Part 12

My efforts to correct a pair of troublesome switches near the outer end of my Santa Rosalia Branch layout are continuing. In the previous post on this topic, I showed the beginnings of replacement, after the offending switches had been removed and discarded. (That post can be viewed at this link: .) An important issue unresolved at the end of that post was the realignment of the MP1 switch machines that power these two switches.

The decision I made was to move both MP1s, but not very far. This can be best illustrated with an overhead photo, showing an intermediate step. In the photo below, the MP1 at left has been shifted leftwards, and the trench for its operating rod enlarged to the left. That permitted the MP1 at right to be moved leftwards also, and on the premise that it will operate all right at an angle to the track’s perpendicular, a new trench was cut. The old trench is the empty one at the right.

Next came fitting the curved switch that goes to the right of the photo above. This had complications, since it was too long at the throwbar end, and too short at the far end. I fixed the latter with a couple of short segments of rail (a few millimeters long), soldered into long rail joiners.

I then proceeded to fit the track together. Though this was a little demanding, given that the area I was working in is among the least conveniently accessible on the layout, I did get everything lined up and assembled. Here you see it all, prior of course to detailed testing of the work and verification that it would operate okay. Both MP1 switch machines are connected too.

I began testing with a long-wheelbase Consolidation steam locomotive, just to see what is likely to be the worst case. Loco SP 2829 worked fairly well over this new track, but inconsistently seemed to find areas of less than perfect gauge. I have continued work to try and find (and correct) these little bugs, and have steadily found and fixed a number, but am sure more needs to be done.

So it’s clear that this new pair of switches is not exactly ready for “prime time,” as we say, but probably will be all right for my upcoming operating session. To be safe, I’ll probably use a 4-axle diesel switcher on the local, just to give a little margin for remaining problems.

Tony Thompson

Wednesday, April 3, 2024

Trackwork wars, Part 11

When last we visited this topic, the subject was the need to replace a pair of switches on my layout that had caused derailments and other trouble many times, over numerous operating sessions. Sometimes severely, sometimes not, but definitely trouble. I showed the location after removal of one of the switches (see that post at: ). 

I next completed removal of the two switches by taking out the curved one at the right of the photos I have been showing in prior posts. Here is the area with both of the offenders removed. At the top of the photo below is the new Walthers curved switch that will be installed.

After some careful fitting, a replacement No. 6 switch was placed at the left of the scene shown above. Rails were painted a kind of “Roof Brown” color, and aligned with the trackage at upper left (two tracks: one is the lead to the Jupiter Pump & Compressor plant, the other is the main track in Ballard). Testing of the new switch seemed to work well, though of course locomotives could only be run onto the new switch at this point, not completely through it and beyond. Here I was checking level.

With an operating session coming up, it occurred to me to carefully test other switches on the layout which have been problematic in the past. Almost immediately I found that one of the point rails at the east end of the Ballard double main had come un-soldered. This happened once before during an operating session, so I was glad to find it now, and re-solder. Here is how it looked when it had just failed.

My next project was to fit the second replacement switch into the area being worked. As I was starting this, I realized what a  different scene was being created by the work tools and materials, compared to the layout scene that usually exists here.

The new switch was readily fitted into the existing track alignment, but a new problem arose: the throw bar on this switch is located differently that was the case for the previous switch, and not even close — instead, it’s around three-fourths of an inch away. And what’s worse, it’s different in the direction that is closer to the adjoining switch, meaning the two MP1 switch machines can’t remain in their present locations.

I’ve shown all this below, with a large red arrow aligned with the current location of the throw bar of the switch that was previously located to the right. You can readily see, not only that this location isn’t at all close to the throw bar of the new switch, but equally seriously, that the new bar location would practically touch the switch machine to the left.

Obviously, I have to dig up the actuating rod that is buried at right, as it no longer connects to anything. One possibility then is to simply rotate the machine at right somewhat clockwise, and then operate a connecting rod at an angle to the track, instead of perpendicular.  It might also be practical to move or rotate the MP1 at left. Rotating it 180 degrees would probably be easiest. Then the one at right could be relocated so as to operate perpendicular to the track. Moving both switch machines isn’t attractive but might prove necessary. More on all this later, when progress has been made.

Tony Thompson

Sunday, March 31, 2024

Three-compartment tank cars

I recently had an interesting question sent to me by email. The essence of the question was, “Is it realistic to operate three-compartment tank cars?” I did send the questioner a link to Richard Hendrickson’s article in Model Railroad Hobbyist on the topic (“Multiple-compartment tank cars” in Model Railroad Hobbyist, in the issue of February 2015). But it occurred to me that I could add some comments here.

Multiple-compartment tank cars of any kind were relatively rare; by one estimate about 95 percent of all tank cars in the transition era were single-compartment cars. Nevertheless, tank cars with two or more compartments did exist and were often photographed. In HO scale, the most familiar model of such a car is the old Athearn “Blue Box” three-compartment plastic model.

I show an example below. Note that the car has low-height expansion domes with single safety valves, correct for the car as shown, and has the double rivet rows between domes that represent the attachment of the internal bulkheads that separate the compartments. It even has three outlet pipes, one beneath each dome. 

Problem is, no one has ever found a prototype three-compartment car this big, though this may well be what one would look like, if one existed. (Typical prototype three-compartment cars were usually much smaller, and had taller and narrower domes, by the way.)

This is an interesting model, with a discernible history. I have previously talked about the 1950s Athearn and Globe metal tank car kits (see that post at: ), and it’s long been evident that when Athearn chose to create a new plastic tank car, they began with the three-compartment car shown above. Yet they once had a very nice metal tank car kit for a three-compartment car (shown in the post just cited).

As noted above, prototype three-compartment cars were considerably smaller than the Athearn model shown, often about 6000 gallons total capacity, half the volume of the model shown above. For background on real cars, I recommend John Riddell’s article in Mainline Modeler entitled “ACF Tank Car” (issue for September 1995, pages 42–47). Beyond that introduction, a much fuller account was is the Richard Hendrickson article published in Model Railroad Hobbyist, February 2015.

What occasioned Richard’s article was the release of the beautiful Tangent model of a 6000-gallon three-compartment tank car in HO scale. Here is Richard’s version of this model, lettered with Black Cat decals and with added placards, chalk marks, rust stains at tank bands, and spillage from the domes.

An even better model of a car like this was the Southern Car & Foundry resin kit, modeling a car built by Standard Tank Car Company (a model developed with Richard’s input on the prototype). Moreover, it models a car which later in life, had two new end compartments added, making three altogether (and the new domes are smaller, since they serve smaller compartments than the original single compartment). Here is one of these models built up, lettered to match a prototype photo.

As this SC&F model reminds us, many three-compartment cars came into being as modified single-compartment cars. I have accomplished the same for one of the common uses of such cars, wine transportation. (For much more about tank cars and the wine business, see my “Getting Real” column in the Model Railroad Hobbyist issue for May 2023.) Here is an example, shown spotted for loading at the winery in my layout town of Ballard:

This model began as a Proto2000 insulated tank car, and I added the two end domes, deliberately in a quite different style, consistent with many prototype wine cars. I described the modeling in that MRH article, and also in a prior blog post (see it at: ).

My recommendation to modelers over the years has always been put those Athearn plastic three-dome cars in a storage box somewhere, to ensure no one sees them on your layout, and if you’re at all meticulous about freight cars, do the same with the Athearn plastic single-dome cars, with their hold-over low dome from the 3-dome model. 

It’s a shame to have to say that, because the Athearn plastic single-dome car is a very accurate Southern Pacific 12,500-gallon tank car — except for that very obvious wrong dome, and a few lesser details. I have for years converted them, a full dozen cars by now, with dome correction and fixing all the other details. A pretty full description of how that is done is here: .

But in summary, yes, three-compartment tank cars are entirely prototypical (if fairly rare), they just aren’t much like that old Athearn monster.

Tony Thompson 

Thursday, March 28, 2024

Trackwork wars, Part 10

In a recent post, number 9 in my series on this topic, I showed the work done in leveling some track in the area between my layout towns of Ballard and Santa Rosalia (you can read that post at this link: ). 

But even as that work was being completed, I realized it was not all of the problem. There remains some variability in the track gauge that still can cause derailments, and in a few places the track gauge becomes too tight. Thus this post.

For example, I have used the clear plastic “test car” shown in the previous post (see first paragraph for link), and even with the track leveled, there are still derailment problems. Below you can just see the leading wheel lifting and turning to derail.

Both these switches have given trouble for some time. The one at left in the photo below is a Peco, and like other Peco switches I have, it has evidently experienced shrinkage in its plastic parts, and the track gauge is now too tight. I corrected this once before, by filing the inside of the rail head. By now I’m not too enthused about continuing with that, as I have had to do the same with two other Peco switches on the layout, and it’s an apparently endless task. At least the other two don’t cause derailments after their gauge is corrected.

[By the way, I contacted the Peco “help” service about this shrinkage. Amazing how naive I was, even at my age: I thought they might apologize for the defect, might even send me a replacement. But in fact, Peco replied that they “had never heard of anyone experiencing shrinkage in a Peco switch,” though I have three different Pecos that have done this, and others around the U.S. have told me the same. Makes me take a deep breath before purchasing more Peco switches.]

Next I began to measure the individual rails in the two switches, since some appeared to perhaps be bent. I soon found that indeed there were bent rails, bent vertically, not horizontally, which is less convenient to fix (perhaps the result of an earlier derailment). At first I began to try and straighten them, which wasn’t going well, when it came to me: “What am I doing? Replace the bloody things!”

My first step, in which I admit I took pleasure, was to remove the annoying Peco switch. Once it was separated from the other track, I felt better already.

Over at the right edge, you can see the existing curved switch, and just above it, a new switch, one I had in stock, but not one that would fit.

I spent some time shopping for new switches, and reading a couple of email lists for comments about the various switches on the market. For the curved turnout at the right of these photos of the area (see middle photo, above), it looked like the dimensions of the relatively new Walthers line of “DCC friendly” switches would fit. 

For the other switch, a left-hand #6, I am still looking at options. The Walthers switch of this kind has a very straight diverging route beyond the frog, which I don’t think will work in my location. There are a couple of other manufacturers of switches that are options.

It would have been nice if these new switches could be located with throw bars exactly where their predecessors were located. But I realize that isn’t likely, so probably the entire switch machine locations (see photo above) will have to be moved, including digging up the buried tubes that carry the activating wires. That’s just to be expected as part of the project.

Now I just need to get the new switches in house and start restoration. Progress reports later.

Tony Thompson

Monday, March 25, 2024

SoundRail 2024

In alternate years, the layout owners around Puget Sound, Washington put together an operating weekend called, for obvious reasons, SoundRail. I attended this years, as I have done four previous SoundRails. I’ve always liked their emblem, combining rail with the waters of the Sound and Seattle’s iconic “Space Needle,” dating from the 1962 World's Fair.

This year, my layout assignments began with Joe Greene, located way up in Sequim, on the upper edge of the Olympic Peninsula. This is a wonderful layout, modeling the C&O in Appalachia in 1974. The job I drew this time was the excellent paper mill model, with (I think) 16 different car spots around the plant. This was interesting and fun! Mark Schutzer and I had a great time switching the entire area, along with some yard work.

The following day, we began the regular schedule of the meet (Joe’s layout was a “bonus” session). My first layout was Dale Kreutzer’s superb Rio Grande Southern 2nd District, set in 1926. I had operated there once before, so knew what to expect. It’s a marvelous job of scenery, the trains ran perfectly, and it was really a pleasure. I had the Mancos Turn, a switching-intensive assignment that was excellent for me, and much of the enjoyment was the beautiful setting.

Next came Bill Sornsin’s Great Northern, modeling the Seattle area and the eastward climb to the top of the Cascades in 1956 in HO scale. I was really looking forward to this, as I had not operated at Bill’s at the previous SoundRail, and was eager to see layout progress. There was a lot! He now has a magnificent model of King Street station, an iconic structure and of course the centerpiece of extensive passenger operation.

I got to work at Interbay Yard, which had only limited operating capability last time I was there, but now was a fully functioning yard, closely following the prototype trackage. The yard crew really had fun all day here. And the prototype yard is still there today, not far from Bill’s home.

My final layout was Jim Younkins’ N-scale Mud Bay & Southern, set in the Olympia area in 1974. This is a huge layout, with very nice scenery and excellent structures. One of the things I like about N scale is that industries can be big enough to look like they really need multiple freight car spots. My job this time (my third visit!) was at Elma, a location with a lot of switching. Here’s a view of North Elma, with the yard area in the foreground.

One of the many nice features of Jim’s layout for visitors is the excellent town maps on the fascia in each area. Here is the map for the scene shown above. (You can click on the image to enlarge it if you wish.)

This was another outstanding SoundRail, a meet I have enjoyed every time I have attended, and I’m sure I will go back. I report all this mostly to show how much interesting fun you can have at a meet like this, and I hope anyone reading this, who hasn’t every operated at such a meet, will seek one out and give it a try.

Tony Thompson

Friday, March 22, 2024

More about Chrysler trucks

In a recent post about the steel express refrigerator conversions of Pacific Fruit Express, I mentioned the Chrysler freight trucks applied to 25 of the cars when they were converted to passenger express service. These were visually distinctive because of the use of an external hydraulic snubber, which projected upwards on the side frame. (You can read that post at: .) Here is a photo of the prototype truck (PFE photo, CSRM).

I mentioned in that post that I had made representations of Chrysler trucks for my own car fleet’s PFE steel express reefers, using a casting from Ross Dando’s Twin Star Cars company. This was a nice part and certainly an accurate representation of what you see above. Here is that truck on my PFE car:

I don’t know whether Twin Star Cars will necessarily return that part to inventory. But there is an alternative and perhaps better option today: a company called “Plate C Model Prototypes” has made a 3-D printed version of this truck, now marketing it through 3D Central. You can see the 3D Central trucks at this link: . The Chrysler trucks are on page 2, and I used Part 4103-01, the original truck design. As of this writing, they are in stock. (The site warns that things can go in and out of stock, so patience might be necessary).

They really are nicely done. I show a rather close-up photo below, and in my opinion, this compares favorably with the Twin Star Cars version or the prototype photo above. Note in the lower view how much the snubber projects, as should be the case.

But if I already had a nice version of these trucks under my PFE express reefer, why did I buy another pair? Three years ago, I posted about the work I did, modeling one of the General American-Evans pioneer DF box cars, where DF = Damage-Free loaders. (That post can be found here: .) 

The just-linked post has more details, but briefly, the consortium of General American, the car builder, and Evans Products Co., the DF-loader maker, built 540 cars, 340 of them with conventional vertical panels, 8 on each side of the door. The photo below shows an example (George Sisk photo, Charles Winters collection), drawn from the 110 cars built in the late fall of 1950 and leased to the Pennsylvania Railroad.

The prototype GAEX cars had Chrysler trucks (visible above), which originally I decided to ignore, and simply used conventional trucks under the model. But in that post, I prophetically wrote, “Maybe I’ll come back later and redo the trucks.” That’s the reason for buying another pair: so I can complete my GAEX box car.

I won’t go into the model itself, as the background and modeling was adequately described in the two original posts (the second is linked two paragraphs above). For the current topic, what’s important is that now I can “finish” that model with correct trucks. Here are the Plate C trucks installed:

I am glad to make this model more accurate with the replacement of its kit trucks with these impressive 3-D printed versions of the Chrysler freight truck. This is yet another example of the accomplishments of 3-D printing in our hobby.

Tony Thompson

Tuesday, March 19, 2024

Understanding bridges, Part 2

In the previous post, I discussed the most fundamental principle of bridge design, the importance of beam or bridge depth, relative to length. The key point is that the stiffness of a beam (or bridge) depends on the width to the first power, but the depth to the third power. You can read that post at this link: .

Probably the most familiar type of large railroad bridge is the truss bridge. This is really just a beam bridge, but with unnecessary material removed, leaving just the material that ensures the depth of the “beam” (or bridge) is maintained, i.e. keeps the top and bottom apart. The familiar framework of a truss bridge can be understood in that way. I will show a typical railroad bridge, then delve into explanation.

Below you see Southern Pacific’s bridge across the Salinas River at Nacimiento, on the Coast Route, being crossed by a freight behind a pair of rebuilt GP9Es, in 1974 (Ed Workman photo). This is a Pratt truss, as I discuss below.

In the sketches below, imagine that the components shown are a stiff rubber. I think you can readily see in (a) that the bottom has to get longer (tension) and the top will get shorter in response to a load on the top. 

In (b) I show the simplest possible truss, known as a king truss, simply a triangle, and imagine that you have a handle underneath that you can pull down on. Again, I think it’s clear that the two upper members will be squeezed together as the lowest member lengthens. The problem with such a design is that the span is fairly long. Adding a rod between top and bottom (c) would minimize flex of the bottom member and in effect, hangs a floor beam from the top of the truss.

These are the fundamental ideas of how truss members behave. If we now draw a truss that can span a larger gap (it happens to be a Pratt truss; more on that in a moment), I can indicate the names of the truss members (posts, ties, chords, etc.) and you can see the stresses for uniform loading, in effect, equal loads on each floor beam.

Note that I have drawn some members (the top chord and end posts) heavier than the remaining members. This is because they are in compression, while all the other members are in tension and can be lighter. This is one of the attractions of the Pratt truss.

Over the decades, especially in the 19th century, there were a great many truss designs invented, many of them with numerous redundant members (as we now recognize). But quite a few are reasonably efficient designs and have been used for railroad bridges. I show a dozen of them below (a figure from Mallery’s book, citation in the first post of the series). Some, like the Pratt and Warren, are used today. The Howe truss, a carry-over from wooden bridge design, is less efficient as it has numerous members in compression, which have to be heavier.

Finally, one more important bridge type is the arch bridge. This bridge design directly reflects the fact that forces in the bridge are carried in the curvature of the arch, and thus are exerted entirely through the ends of the arch. The best arch bridge, then, is a a full half-circle, and the forces are directed exactly downward. But partially circular arches are also feasible, if sufficiently strong areas at the side of the bridge exist, so that the arch can bear into those sides.

This is not a new idea. Arches were used in ancient times, perhaps most impressively by the Romans. The famous aqueduct near Avignon, France, the Pont du Gard, still stands (photo from USGS website). This was part of a 31-mile aqueduct, and the engineering skill involved is evident because there was only a 56-foot drop over the whole 31 miles of the system.

Modern arch bridges for railroad use, thought not the most common type, certainly do exist. Among the most famous is the Great Northern’s bridge across the Mississippi River at Minneapolis, built in 1883 and carrying rail traffic into the 1980s, but now a hiking trail. In this view (Burlington Northern photo) GN No. 12, the Red River, is leaving Minneapolis for St. Paul behind an E7 diesel.

However, the drawback to the arch bridge is that it is normally erected over falsework which temporarily has to fill the space beneath it, at least if it is a masonry arch. The carton below shows an unlikely alternative (originally published int the Saturday Evening Post, now found throughout the internet):

My purpose in collecting this information and illustrations is to help modelers understand what they are doing when they choose a type of bridge for a layout situation. Mallery’s book contain a great deal more detail on this topic than is practical to show here, but this should suffice as an introduction. And the article by Larry Kline and me, also cited in the first post, contains more information on the history of railroad bridges.

Tony Thompson