Dynamic Braking on diesel/electric locomotives has changed train handling rules and procedures throughout the industry over the last 20 or so years. What then, is dynamic braking?
Dynamic braking is accomplished by taking the locomotives traction motors, six usually, one per axle, and through electric switching, change them into generators. The resulting electric current is dissipated in a grid, commonly located right behind the cab. Picture a giant toaster with a couple of blower motors, that’s a dynamic braking grid. And BTW, they are absolutely spectacular when they blow out at night…
I ran trains for a Class 1 carrier until my retirement almost 5 years ago. I started this second career in 1997, and at that time dynamic braking was encouraged, but not required. The operating instructions have slowly moved toward maximizing the use of dynos, and minimizing the use of the air brakes. It saves fuel. The carrier I worked for employed remote locomotive downloads for years. When your train passed a remote download point, your information would be automatically sent to HQ for a first look. If there was any discouraged or prohibited behavior recorded, you’d soon hear about it. Called on the carpet, so-to-speak…
It takes a bit of time to properly change from say, wide open throttle to maximum dynamic braking effort… There are 8 “notches,” in both the throttle, and the dynamic brakes. The carrier likes you to pause in between notches, usually 10 seconds will suffice. So from Throttle 8, figure on 10 seconds between notches reducing throttle, 10 additional seconds in “Idle.” Then, to enter the dynamic braking zone, you first put it in “Set Up,” for 10 seconds, then as you have time, gradually increase the dynamic braking effort until you feel you’ve bunched the slack up against the head end. Once they’re all up against you, it’s OK to increase the dynamic braking effort to maximum, won’t hurt a thing…
Now realize, all these 10 second delays add up. You’ll also have to be blowing the whistle at crossings, watching the block signals, paying attention to your location with respect to upcoming restrictions, and keeping one ear to the radio with the Defect Detector and the Dispatcher. Remember too, if you plan your speed reduction using maximum dynamic braking effort and find you are coming into the speed restriction too fast, your only option is to use the air brakes, or speed through the restriction, neither of which are good. Much better to plan your reduction using Notch 6 or so of dynamic braking, that way if you see you’re a little hot, you have Notch 7 and 8 you can go to, so as to properly control your speed. Sixteen to twenty thousand gross ton trains were the norm even 5 years ago. They take awhile to start, and they take awhile to stop. Normally a train that heavy will be restricted to 40 or 50 MPH tops...
The oldhead, stretch-braking method was quicker,more direct, but much less fuel efficient. To satisfy the oldheads, you had to be in Run 8, yup, wide open, to set air… Set the “Minimum” first, there’s a detent there at Minimum, it’s 5 or 6 pounds. After a minute or two, they “fillout the set,” to 10 pounds or so, adding air braking effort by 2 pounds if needed. As the train stopped, the engines would be straining against the train almost full throttle. You can see why this wasted fuel.
Locomotives are equipped with “counters.” Much like trip odometers in an automobile. If we were on a loaded coal train say, and doing our allotted 40 MPH with a 25 MPH speed restriction ahead, I’d start easing off them about 5 miles out. By 4 miles out, I’d have them in Set Up, and slowly begin bunching the slack. Normally, there’d be a Yellow Board at 2 miles out, and by then I’d have 5 MPH off it, and set the counter. From there, it was fairly simple to calculate the distance left until the restriction versus the speed we were then doing. I used to tell my students that the key to running the big, heavy trains was just like in an old Western, when somebody pulled a gun they’d say, “Don’t make any sudden moves.” The same holds true for a successful engineer. Everything slow and easy, no sudden moves!
I sure miss Sunday Trains, don’t you? This is just a little something to kick around. I hope you enjoyed it. Best, Hoghead99
