Read this issue!
Please post any comments or questions you have here.
Kudo's to Richard Hendrickson for doing the research and putting all this together in one neat little package! I enjoyed the read and learned quite a bit about the development of the Freight Car Truck, and the linked .pdf file showing available trucks is certainly an asset to any model railroader. Well Done!
I will be referring to and rereading this article many times, I suspect. Truly a gem.
Danville & Western HO modeler and web historian
Stuff like this is what I like.
My other hat is Superintendent of the NMRA Pacific Northwest region Second Division. Last month we had a division meet and were fortunate enough to have Richard present this material in person!
Lotsa great stuff.
Contributing Editor, Model Railroad Hobbyist magazine
One of the more educational articles I have seen in a long time. Very impressive work and my compliments.
Dear MRH team,
Nice and very informative. So, when can we expect Part 2, the post 60's > current-era roller-bearing edition?
Aim to Improve,
This is what makes MRH the standout magazine. Great article!
So, when can we expect Part 2, the post 60's > current-era roller-bearing edition?
So, when can we expect Part 2, the post 60's > current-era roller-bearing edition?
I model 1969 so am asking the same question.
HO, 28x32, double deck, 1969, freelance, RailPro
Now there's some good solid information....even as a freelancer, my railroad isn't going to be making it's on trucks!!!
Terrific job! One of the best articles on trucks I've ever read. It will be a great source of reference material for years to come.
This article seemed to cover everything it stated it was going to, and covered it well. Will there be a follow-up article on passenger trucks?
somewhere on the MRH site. Perhaps Joe can start a Modeling Reference Library for articles like this that will see wide use and are essentially timeless.
Philip H. Chief Everything Officer Baton Rouge Southern Railroad, Mount Rainier Div.
Now I have to print it out
Excellent article. I also am looking forward to a Part 2.
This is really an exceptional article that covers the subject completely. I've read other articles in the model railroading press but none cover this so well and especially not with so many detailed photos.
Well done to both Richard for the research and writing and MRH for making it available to all of us!
Thank you Mr Hendrickson for doing this article. My modeling interests are the early 1900's logging railroads (1900 to 1920), and the 1950's right before steam died out. Articles like this help me better understand trucks and what would be right for each era. Hopefully in a future article, someone will be able to fill in pre-1900, as the kind of logging railroad I'm modeling would have often used obsolete equipment.
After covering trucks, somebody out there should cover brake wheels and brake systems with a similarly comprehensive article!
This is an excellent article, well beyond any other I have seen in the hobby press.
I hope you will do one on passenger trucks for the same time period.
I have downloaded the pdf on model trucks just in case in the years to come it disappears. I think that it should be added to the subscriber bonus downloads section. I know the plan is to keep the web site up to date, which I think is great, but overtime some things go away on the 'net.
I agree with the poster above who suggested this article be saved in a reference section on the MRH site.
articles in MRH so far. This and Bruces DCC articles are gems.
GREAT article, well researched and written. This one gets a permanent bookmark.
Thanks for the excellent article.
I have always wondered about the term 'Double Truss'. What does it refer to? Why is it that only later trucks, such as Photo 39, are referred to as 'Double Truss' yet they look to me to be similar to the the earlier trucks such as the Battendorf in Photo 16. Is it that when the U-Channel gets closed in, that it becomes 'Double Truss'.
Great article. I worked for 8 years on passenger type trucks and they are a real pain to repair worn parts.
Fantastic article. This is the kind of reference you just won't find in a print magazine.. or most books for that matter. Thank you very much, this article has been much appreciated!
“If you carry your childhood with you, you never become older.” My modest progress Blog
A very informative article, espically for newbies like myself who didn't realise there were so many different types of trucks.
Modeling in N Scale the transition era of the late 1930's/ early 40's Texas & Pacific RR (T&P) and the Missouri, Kansas, Texas RR (KATY) centered around Fort Worth, Texas.
Someone asked for a summary of hand brake wheels a few days ago. There are 59 pages covering a wide variety of freight car hand brakes in volume 10 of the Railway Prototype Cyclopedia. Additionally, RPC Volume 16 offered a summary of running boards and brake steps. If you have an interest in prototype freight car designs and hardware, I highly recommend these publications.
El Paso, TX
Follow along with my railroad modeling:
Thanks for this definitive article. It's a pleasure to read something so thoroughly researched and illustrated, and the writing is clear and concise.
Serving the Mid-Atlantic in N scale with the Bolero, Lindy & Tango RR (1925) and the Cha-Cha Chesapeake Industrial RR (1946).
Kudos to Richard for a great article on the wide variety, and history of freight car trucks.
But on one point we disagree:
"Following the war, roller bearing manufacturers engaged in a vigorous promotional campaign to market their wares to the railroads, even going so far as to describe roller bearings as "anti-friction" bearings in contrast to "friction" (i.e., plain) journal bearings. This terminology was nonsense, of course; all bearings have friction, and though roller bearings have less resistance to starting and at low speeds, their advantage was relatively slight at normal train speeds. "
This implies that "plain" journal bearings were slandered by the roller bearing vendors. As a mechanical engineer, I disagree. Readers should be aware of both sides of this debate, since there are implications for some modelers. To start, "anti-friction" was not a term dreamed up by marketing types. In fact, one of the earliest RR related patents, granted in 1845 (that is not a typo - yes 1845) was titled "Antifriction-box for Axles, &cc" This was US letter patent 4226 (available from uspto.gov), granted to Wm. Rowan of Belfast, Ireland! The drawing is of a journal box with cylindrical roller bearings surrounding the axle. Further research finds over 100 patents for "anti-friction" bearings for railroad journals before the first significant tests began in the 1920's.
The "grand-daddy" of today's modern tapered roller bearings was patented by Timken back in 1898, although Timken does not appear to focus his invention on the Railroad industry until after WWI (within the transportation industry, railroad roller bearings carry some of the largest loads and their development was not trivial). Many others patented various forms of roller bearings for the railroads, and Timken had several significant competitors. But Timken's "tapered" roller bearings are arranged in pairs on each journal. As paired tapered rollers, these bearings not only transmit the weight of the car from the truck journal to the axle, but they also transmit lateral forces when in curves. Other bearing vendors had alternative designs for countering the thrust loads (to include friction bearings or additional roller or ball bearings), but none were as efficient and as reliable as Timken's design.
But Timken's basic tapered roller bearing patents have long expired in this field, and today all freight car roller bearings use a set of opposing tapered roller bearings at each end of the axle, and the pairs are prepackaged in a modular unit that press fits onto the axle, and then slots in the truck side frames are lowered over the bearings outer structure to pin it in place.
Technically, the term "anti-friction" bearings predates railroads. A bearing is a device that transmits forces (loads) between two moving surfaces. A Friction bearing is a bearing where the two surfaces slide past each other - either in direct contact, or with a lubricant between them that avoids direct surface to surface contact. An anti-friction bearing involves only rolling contact - essentially internal wheels that roll between the two surfaces. The physics of the "resistance" of these two types of bearing is quite different. The impact of these differences on prototype railroad operations is significant.
That is because the resistance of modern anti-friction, or roller bearings, is a fraction of the old plain journal/friction bearings, especially when a train was starting. For those modeling into the transition era, especially steam powered trains, there is a famous saying - "A steam locomotive could pull a train it could not start, while a diesel could start a train that it could not pull." Credit the plain or "friction" bearing for this saying, or at least the derogatory saying about steam locomotives. (For diesels, the problem was the linear decrease in tractive effort as their speed increased, while modern, superpower steam locomotives had a slower drop-off in tractive effort due to their increased boiler horsepower as speed increased.)
The steam locomotive's starting challenge is because when a plain bearing first starts rotating, the axle and journal bearing are literally in direct contact - sliding past each other. This friction is huge - 10 to 20 times the minimum bearing friction that occurred between 10 and 20 mph. As the axle rotates and draws oil into the bearing gap, a film of oil would be established, eventually lifting the bearing block off the axle after several axle revolutions. The oil film now transferred the weight of the car from the truck journal to the axle (under considerable pressure), and the "friction" would drop by a factor of 10. But this is not "frictionless" - the oil in the gap is being sheared continuously, and that is another form of internal friction. This phenomena was the steam engine's bane - and the reason you hear old-timers talk about "taking slack" (which actually means to compress the couplers between cars so slack would be created in the draft gear - usually done by reversing the locomotive into the train before trying to start - often with sand flowing to also help coat the rails), and then "walking out" the train (or slack). Lots of banging and noise when starting a train like this, plus impact loads on each car's cargo that railroads sometimes had to pay for. But because the steam locomotive was now only trying to start one car at a time, the initial starting friction was only for a few cars - the other moving cars would be moving at 2-3 mph, and had established oil films in their journals that had significantly lower friction. Hence the term walking out the slack - typically at a walking pace. If the engine could not get the entire train up to that pace, the train would stall - and typically slack would be taken again (The process helped warm the bearing oil, which made it easier to draw into the bearing gap - especially in cold winter weather. So on the next attempt the engineer was facing a better situation.). Once the train was moving, plain journal bearing friction would actually drop as the speed approached 5-10 mph, giving the engineer a chance to readily increase speed in that regime (assuming flat, tangent track).
Roller bearings, because they were rolling contacts, did not suffer from this - especially once the more modern roller bearings began to appear (early roller bearings were oil filled, and suffered from much higher resistance than today's roller bearings.) But even in 1931 roller bearing starting resistance was a fraction of plain bearing starting resistance.
Tests in 1931 by the PRR and Timken documented the difference when starting two 100 car sets of 70 ton hoppers - one set with plain/friction bearings, and the other with roller bearings (a very early version).
"Starting tests on a 0.3 percent ascending grade with a 2-10-0 steam locomotive showed that 76 cars could be started with either bearing type by taking slack (starting one car at a time). With stretched trains (no slack), 65 roller bearing cars were started compared to 37 plain bearing cars. The easy starting characteristic of roller bearings could be used to reduce shock in couplers, draft gear, and lading." [The parenthetical notes are from the paper, not from me]
This helps explain why modern videos of restored steam engines are so easily able to start modern, roller bearing equipped freight trains. Now a steam locomotive can start a train it can also pull!
But for a steam era modeler, it is important to note that a steam locomotive would not start a steam era train by crawling at 1 mph, so I no longer am concerned about making sure model locomotives can meet this very exacting requirement under load (those modeling modern steam excursions may want the low speed crawl, since now it could be prototypical).
The PRR/Timken test also showed that the 1931 roller bearing equipped cars had 9 percent less rolling resistance at 50 mph. Today's modern roller bearings have only 1/3 to 1/4 the rolling resistance of the 1931 tests, and the resistance is nearly constant across a wide range of speeds. From a historical perspective, today's wheel bearings are a relatively small contributor to the overall train resistance.
Richard also states, correctly:
"In any case, railroad officials weren't inclined to spend money putting roller bearings on cars that spent much of their life off-line in interchange, so the relatively few cars that received roller bearing trucks were in assigned service and seldom or never left their owners' rails."
This is spot on - the owning RR received little economic benefit except for cars in captive service, and the private car owners had no incentive to invest in the much more expensive roller bearings.
Instead, it was the difference in hot box setout and accident rates that drove the major railroads to force an interchange requirement for roller bearings in the 1980s. New cars were required to have roller bearings starting in 1968, but cars could last forty years, so the transition was slow - for a modeler the key is to check the build date of the car, and use the proper truck. But note that many rail cars made after the mid-50's were roller bearing equipped. I have not found data that indicates if house cars (RR owned) dominated the early application of roller bearings compared to privately owned freight cars, but it makes sense that it would.
Back to hot box failures - in 1978 the AAR reported that 40% of the fleet was still plain bearing equipped, but accounted for 89% of the hotbox failures. The other 60% of the fleet was roller bearing equipped, but accounted for only 11% of the hot box failures. Although mileage per car type was not reported, if each fleet averaged about the same miles per car, then plain bearings were over 12 times more likely to suffer from a hot box failure - even after all of the attempts to improve plain journal bearing lubricator pads and seals.
For those who include hot box failure events in ops sessions - in 1951 hot box setouts were running one every 175,000 car miles. (Uncompressed, for a model railroad with a 10 scale mile long main line (pretty long), that would be one setout every 17,500 car trips across the main.) By 1964 hotboxes were occurring once every 1.17 Million car miles - once every 117,000 car trips on the same model railroad. Note that in 1964 plain bearings still outnumbered roller bearings. Today the miles per hotbox setout is much higher.
In 1958 on the SP Santa Cruz branch the first cars to show up in quantity with roller bearings were covered cement hoppers and 50 mechanical reefers. The boxcars still had plain bearing trucks but maybe they weren't sending the latest models onto the branch. Next group to get roller bearing was probably some of the sand hoppers but again that just might have been what was sent out on the branch.I can recall some fairly new looking boxcars from that era that still ran on plain trucks. The late 50's early 60's makes an interesting era to model as the fright car fleet was in transition to larger cars without roof walks but many older smaller cars still ran.....DaveBranum
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