LOSS OF HEAT THROUGH EXCESS OF AIR.
In the fire-boxes of American engines, where double dampers are the rule, far more loss of heat is occasioned by excess of air than there is waste of fuel through the gases not receiving their natural supply of oxygen. The blast from the nozzles creates an impetuous draught through the grates; and when to this is added the rapid currents of air impelled into the open ash-pan by the violent motion of the train, the fire-box is found to be the center of a furious wind-storm. The excess of this storm can be regulated by keeping the front damper closed, and letting the engine draw its supply of air through the back damper. When the fire begins to get dirty, and the air-passages between the grates become partly choked, the forward damper can be opened with advantage. So long as an engine steams freely with the front damper closed, it is an indication that there is no necessity for keeping it open. With vicious, heavy firing, all the air that can be injected into the fire-box is needed to effect indifferently complete combustion; and the man who follows this wasteful practice can not get too much air through the fire. Consequently, it is only with moderately light firing that regulation of draught can be practiced. Running with the front damper open all the time is hard on the bottom part of the fire-box, and the ever-varying attrition of cold wind is responsible for many a leaky mud-ring.
LOSS OF HEAT FROM BAD DAMPERS.
In Britain, where far more attention has been devoted to economy of fuel than has been bestowed upon the matter this side of the Atlantic, locomotives are provided with ash-pans that are practically air-tight, and the damper-doors are made to close the openings. In many instances, the levers that operate the dampers have notched sectors, so that the quantity of air admitted may equal the necessities of the fire. British locomotives, as a rule, show a better record in the use of their fuel than is found in American practice; and a high percentage of the saving is due to the superior damper arrangements.
Imagine the trouble and expense there would be with a kitchen-stove that had no appliance for closing the draught! Yet some of our locomotive builders turn out their engines with practically no means of regulating the flow of air beneath the fire.
CHAPTER VII.
FINISHING THE TRIP.
RUNNING OVER ORDINARY TRACK.
The hill which our train encounters nearly at the beginning of the journey is the Pons Asinorum of the division. The style in which it is ascended shows what kind of an engine pulls the train, and it tests in a searching manner the ability of the engineer. Our engine has got over the summit successfully; and the succeeding descent is accomplished with comfort to the engine, and security to the train. And so the rest of the trip goes on. The train speeds merrily along through green, rolling prairies, away past leafy woodlands and flowery meadows: it cuts a wide swath through long cornfields, startles into wakefulness the denizens of sleek farmhouses, and raises a rill of excitement as it bounds through quiet villages. But every change of scene, every varied state of road-bed,—level track, ascending or descending grade,—is prepared for in advance by our engine-men. Their engine is found in proper time for each occasion, as it requires the exertion of great power, or permits the conservation of the machine’s energy. Over long stretches of undulatory track the train speeds; each man attending to his work so closely that the index of the steam-gauge is almost stationary, and the water does not vary an inch in the glass. This is accomplished by regular firing and uniform boiler-feeding, two operations which must go together to produce creditable results.