SPECIAL SKILL AND ATTENTION REQUIRED TO GET A TRAIN UP A STEEP GRADE.
In the last chapter, some details were given of the methods pursued in starting out with a heavy fast freight train. Where a train of that kind has to climb heavy grades, special skill and attention are needed in making the ascent successfully.
GETTING READY FOR THE GRADE.
The track for the first two miles from the starting-point is nearly level, permitting the engineer and fireman to get ready for a long pull not far distant. At the second mile-post a light descending grade is reached, which lasts one mile, and is succeeded by an ascending grade two and a half miles long, rising fifty-five feet to the mile.
WORKING UP THE HILL.
At the top of the descending grade, the engineer shuts off the steam while the fireman oils the valves: then he puts on a little steam, using a light throttle while the train is increasing in speed, until the base of the ascent is nearly reached, when he gets the throttle full open, letting the engine do its best work in the first notch off the center. By this time the train is swinging along thirty miles an hour, and is well on to the hill before the engine begins to feel its load. Decrease of speed is just becoming perceptible when the valve-travel gets the benefit of another notch, and the engine pulls at its load with renewed vigor. But soon the steepness of the ascent asserts itself in the laboring exhausts; and the reverse-lever is advanced another notch, to prevent the speed from getting below the velocity at which the engine is capable of holding the train on this grade. While the engineer is careful to maintain the speed within the power of his locomotive, he is also watchful not to increase the valve-travel faster than his fire can stand it; for, were he to jerk the lever two or three notches ahead at the beginning of the pull, the chances would be that he would “turn” its fire, or tear it up so badly that the steam would go back on him before he got half a mile farther on. Before the train is safe over the summit, it will probably be necessary to have the engine working down to 18 inches: but the advance to this long valve-travel is made by degrees; each increase being dependent upon, and regulated by, the speed. The quadrant is notched to give the cut-off at 6, 9, 12, 15, 18, and 21 inches. Repeated experiments, carefully watched, have convinced the engineer of this locomotive, that its maximum power is exerted in the 18-inch notch; so he never puts the lever down in the “corner” on a hill. A great many engines act differently, however, showing increased power for every notch advanced. If the cars in the train should prove easy running,—and there are great differences in cars in this respect,—it may not be necessary to hook the engine below 15 inches, or even 12 will suffice for some trains; but this can only be determined by seeing how it holds the speed in the various notches.
WHEEL-SLIPPING.
As the engine gets well on to the grade, and is exerting heavy tractive power, the wheels are liable to commence slipping; and it is very important that they should be prevented from doing so. An ounce of prevention is known to be worth a pound of cure; and it pays an engineer to assure himself that no drips from pump-glands, or feed-pipes, or cylinder-cocks, or from any other fountain, are dropping upon the rails ahead of the driving-wheels. There is no use telling an engineer of the decreased adhesion which the drivers exert on half-wet rails, from what they do on those that are clean and dry. Knowing the difference in this respect, every engineer should endeavor to prevent the wetting of the rails by leaks from his engine; for hundreds of engines get “laid down” on hills from slipping induced by this very cause.
HOW TO USE SAND.
The first consideration in this regard is to have clean, dry sand, and easy-working box-valves. Then the engineer should know how far the valves open by the distance he draws the lever. In starting from a station, or working at a point where slipping is likely to commence, the valves should be opened a little, and a slight sprinkling of sand dropped on the rails. This often serves the purpose of preventing slipping just as well as a heavy coating of sand. And it has none of the objectionable features of thick sanding. Trains often get stalled on grades by the sand-valves being allowed to run too freely. It is not an uncommon occurrence for engineers to open the valves wide, and let all the sand run upon the rails that the pipe will carry, so that a solid crust covers each rail, and every wheel on the train gets clogged with the powdered silica; and, after the train has passed over, a coating is left for the next one that comes along.