Jim Thompson

Email Jim at jim.thompson@ipulpmedia.com

It is transportation month and I will be the first to admit that this column will likely not make you any money. But occasionally, we should have a little education and fun without worrying about ROI, eh? Over the years, when I have brought up these matters with individuals, I get, "Well I didn't know that." So perhaps I can give you a little education, too.

Originally, rail cars were hooked to each other with pins and a steel loop. This was very dangerous for connecting the cars, for the brakeman* had to stand between the cars and hold all the linking pieces in their hands. If a brakeman went to another railroad seeking a job and claiming to be experienced, the foreman* would look at their hands and if they had all their fingers they knew they were lying--that is how dangerous it was.

The modern knuckle coupler was invented in the late 1800's and has been essentially unchanged since then.

You might ask why the couplers do not provide a rigid connection between the cars. The answer is simple. If the cars and the engine were rigidly connected, the train could never start moving. If you happen to stand in a rail yard sometime, you might notice that the engineer may move in reverse for a moment before the train starts moving forward--this causes a clacking sound down the line. This is to get some slack in the first few cars to successfully go forward. Remember, Newtons' first law states that bodies at rest will stay at rest. The "sloppiness" in the couplers is so that the train can move in either direction, forward or backward. The train starts moving one car at a time. The engine moves and then the first car moves. Now the second car engages and starts to move. This continues down the train, one car at a time, until all the cars are moving forward.

Recalling physics, F = MA, comes into play here, too. If you have ever watched a train crash, it is amazing to see how long it takes the train to decelerate. Often it is mile or a mile and a half. Lots of weight there and F=MA is screaming all the way. If you want to see some of this action, go to YouTube and search "Virtual Rail Fan." There are about 400,000 members there.

When trains go around curves, you will notice the tracks are "banked" or lean in to facilitate this process. There is another neat engineering trick here, too. Notice that train wheels are slightly beveled and have an inside flange. When going along on a straight track, the dimensions are such that the wheels ride centered, and the flanges do not touch anything. Going around a curve, the train cars (and engine) all lean into the curve. The outside wheels ride up on the bevel until the flange touches the rail and the inside wheels, because of the fixed spacing on the axle, pull away from the track and run on the smaller end of the bevel. This clever design does two things: 1. It throws the center of gravity of the car to the inside of the curve, helping to corner better and 2. The relationship of the diameters of the wheel make it act like a differential in a rear automobile axle since the length of the inside curve is shorter than the length of the outside curve. That screeching you have heard as the train goes around the curve is the flange on the outside wheels rubbing the track.

Moving on, on intermodal trains, why do they stack the long units on top of the shorter units? Well, they have done wind tunnel studies and that arrangement offers the least wind resistance and turbulence between the cars. Saves fuel and adds speed.

All railroad cars are overdesigned in the axial or longitudinal direction. We often think about the load they carry as the primary weight issue, but the axial loads are perhaps even more important. The car right behind the engine must pull the entire rest of the length of the train. The one behind that must pull the rest of the train minus the engine and first car. You get the idea. The last car in the train has nothing to pull but itself. So, if we could always determine the location of a car in a train, its longitudinal, or axial, strength could be designed for its relative position in the train. Since it would be impractical to build a "consist" (the actual lineup of the cars in a specific train) based on such a parameter, all the cars are axially overdesigned except for the first one behind the engine.

More than you wanted to know!

Be safe and we will talk next week.

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*these words always ended in "man" as only men had these jobs back in the day.

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