When it comes to freight cars, one of the smallest and most overlooked parts is also one of the most important. The journals are vital bearings which transfer all of the weight of the car and its load onto the spinning axles and wheels. The strength of the journal determines the weight the car can carry. And a failure in the journal is likely to cause a serious derailment.
Before we look at the journals in more detail, it may help to put the actual weight of a train into perspective. Let’s compare the prototype with an O scale model. Since O Scale is 1/48 the size of the prototype, a Lionel 100 ton hopper for example will be 1/48 as long, 1/48 as tall as the real thing. So how much would the model weigh if it were 1/48 the actual weight?
Let’s use our 100 ton hopper car as a convenient example. The light weight of these cars is 58,300 pounds. So a scale model would weigh 1,214 pounds – without a load! Loaded, the 200,000 pound car would tip the scales at a little over two tons. Better build some stronger benchwork.
The point of this little exercise is to shed some light on the real scale involved in railroading. It yields a whole new appreciation on the forces inflected upon those relatively small bearings. It should also help explain why trains are nothing to fool with – in a car or in person.
For the first century of railroading, trucks used what are commonly referred to as friction bearings, but more properly called plain or solid bearings.
The term “friction bearing” emerged as manufacturers of new roller bearings looked for ways to promote the new innovation. The aim of all bearings is essentially to minimize friction.
The bearings needed to be kept lubricated constantly to offset the friction. Workers packed the journals with cloth “waste” soaked in oil. The oil puddled in the bottom of the journal box and wicked upwards as the train rolled.
Consequently, a car that had sat on a siding for a length of time would be more difficult to get started as oil dripped back down and the two bearing surfaces came in contact. Cold temperatures also had a noticeable negative effect on the performance of solid bearings.
In addition to being a lubricant, the oil also would burn and smoke as the levels got low and the bearing began to overheat. These smoking journals were known as “hot boxes” and were a common problem for decades on the rails. If the bearing went dry, the journal would score and eventually snap the end of the axle.
When the journals overheated, the smoke and smell would alert train crews in the caboose and at trackside to the problem – hopefully before it was too late. Once discovered, the journal would be repacked and oiled enough to move the car at restricted speed to the nearest yard or siding where it could be set out for repair.
As early as the 1920s, roller bearings began to emerge as a potential replacement for the dangerous and labor-intensive friction bearing. Like other technology improvements, roller bearings came first to locomotives and passenger equipment.
The pace of the conversion was dictated by cost, but also by the magnitude of the process. Since cars, especially freight cars, often interchange between different railroads, parts must be standardized so that a car can be repaired when on another line. It was and is not uncommon for cars to spend months away from their home rails.
To avoid excessive parts inventories, railroads use a few standard sizes of journals, brake shoes, wheels, axles, couplers, etc. So a seemingly simple design change like replacing a bearing or increasing the size of an axle can have far-reaching consequences.
Today, roller bearings are standard equipment on almost everything on the rails. Solid bearings were outlawed in interchange service in 1994. Cars which used older sideframes but had been converted to roller bearings were outlawed for hazardous materials cars in 1992 and all equipment in 1995.
In practice, most bearings and sideframes had been replaced long before those deadlines arrived. Some of the older bearing cars can still be found in cars which do not travel to other railroads however. This includes company service cars like maintenance of way equipment as well as equipment on tourist lines and industrial railroads.
Although it is far less common today, a roller bearing can still overheat. With cabooses no longer in common use, railroads have placed thermal sensors strategically along the mainlines to monitor for excessive heat in a passing train. And though technologies change, the vocabulary doesn’t. They’re still called hotboxes.
While these may all be just small details on a model, the conversion to roller bearings had a big impact on the operations of real railroads. And after all, some of the best parts of the hobby are found in the details!