GASOLINE ENGINE PLANTS The standard voltage set—Two-cycle and four-cycle gasoline engines—Horsepower, and fuel consumption—Efficiency of small engines and generators—Cost of operating a one-kilowatt plant. Electricity is of so much value in farm operations, as well as in the farm house, that the farmer who is not fortunate enough to possess water-power of his own, or to live in a community where a coÖperative hydro-electric plant may be established, should not deny himself its many conveniences. In place of the water wheel to turn the dynamo, there is the gasoline engine (or other forms of internal combustion engine using oil, gas, or alcohol as fuel); in many districts where steam engines are used for logging or other operations, electricity may be generated as a by-product; and almost any windmill capable of pumping water can be made to The great advantage of water-power is that the expense of maintenance—once the plant is installed—is practically nothing. This advantage is offset in some measure by the fact that other forms of power, gas, steam, or windmills, are already installed, in many instances and that their judicious use in generating electricity does not impair their usefulness for the other farm operations for which they were originally purchased. In recent years gasoline engines have come into general use on farms as a cheap dependable source of power for all operations; and windmills date from the earliest times. They may be installed and maintained cheaply, solely for generating electricity, if desired. Steam engines, however, require so much care and expert attention that their use for farm electric plants is not to be advised, except under conditions where a small portion of their power can be used to make electricity as a by-product. There are two types of gasoline engine electric plants suitable for the farm, in general use: First: The Standard Voltage Set, in which the engine and dynamo are mounted on one base, and the engine is kept running when current is required for any purpose. These sets are usually of the 110-volt type, and all standard appliances, such as irons, toasters, motors, etc., may be used in connection with them. Since the electricity is drawn directly from the dynamo itself, without a storage battery, it is necessary that these engines be efficient and governed as to speed within a five per cent variation from no load to full load. Second: Storage Battery Sets, in which the dynamo is run only a few hours each week, and the electricity thus generated is "stored" by chemical means, in storage batteries, for use when required. Since, in this case, the current is drawn from the battery, instead of the dynamo, when used for lighting or other purposes, it is not necessary that a The Standard Voltage Set In response to a general demand, the first type (the direct-connected standard voltage set) has been developed to a high state of efficiency recently, and is to be had in a great variety of sizes (ranging from one-quarter kilowatt to 25 kilowatts and over) from many manufacturers. The principle of the gasoline engine as motive power is so familiar to the average farmer that it needs but a brief description here. Gasoline or other fuel (oil, gas, or alcohol) is transformed into vapor, mixed with air in correct proportions, and drawn into the engine cylinder and there exploded by means of a properly-timed electric spark. Internal combustion engines are of two general types—four-cycle and two-cycle. The former is by far the more common. In a four-cycle engine the piston must travel twice up and down in each cylinder, to deliver one A one-cylinder engine of the ordinary four-cycle type has one power stroke for every two revolutions of the fly wheel. A two-cylinder engine has one power stroke for one revolution of the fly wheel; and a four-cylinder engine has two power strokes to each revolution. The greater the number of cylinders, the more even the flow of power. In automobiles six cylinders are common, and in the last year or two, eight-cylinder engines began appearing on the market in large numbers. A twelve-cylinder engine is the prospect for the immediate future. Since the dynamo that is to supply electric A two-cylinder engine is more even in its flow of power and a four-cylinder engine still better. For this reason, standard voltage generating sets without battery are usually of two or four cylinders when of the four-cycle type. When a single-cylinder engine is used, it should be of the two-cycle type. In the two-cycle engine, there is one power stroke to each up-and-down journey of the piston. This effect is produced by having inlet and exhaust ports in the crank case, so arranged that, when the piston arrives at the bottom of the power stroke, the waste gases are pushed For direct lighting, the engine must be governed so as not to vary more than five per cent in speed between no load and full load. There are many makes on the market which advertise a speed variation of three per cent under normal loads. Governors are usually of the centrifugal ball type, integral with the fly wheel, regulating the amount of gas and air supplied to the cylinders in accordance with the speed. Thus, if such an engine began to slow down because of increase in load, the centrifugal balls would come closer together, and open the throttle, thus supplying more gas and air and increasing the speed. If the speed became excessive, due to sudden shutting off of lights, the centrifugal balls would fly farther apart, and the throttle would close until the speed was again adjusted to the load. These direct-connected standard voltage sets are as a rule fitted with the 110-volt, direct current, compound type of dynamo, the duplicate in every respect of the machine Since the installation of a direct-connected standard voltage plant of this type is similar With gasoline power, the cost of the engine offsets the cost of the water wheel. The engine is more expensive than the ordinary gasoline engine; but even this item of cost is offset by the cost of labor and materials used in installing a water wheel. The expense of maintenance is limited to gasoline and oil. Depreciation enters in both cases; and though it may be more rapid with a gasoline engine than a water wheel, that item will not be considered here. The cost of lubricating oil is inconsiderable. It will require, when operated at from one-half load to full load, approximately one pint of gasoline to each horsepower hour. When operated at less than half-load, its efficiency lowers. Thus, for a quarter-load, an average engine of this type may require three pints of gasoline for each horsepower hour. For this reason it is well, in installing such a plant, to have it of
This table is figured for an efficiency of only 40 per cent for the smaller generators, and 60 per cent for the larger. In machines from 5 to 25 kilowatts, the efficiency will run considerably higher. To determine the expense of operating a one-kilowatt gasoline generator set of this type, as to gasoline consumption, we can assume at full load that the gasoline engine is delivering 2½ horsepower, and consuming, let us say, 1¼ pint of gasoline for each horsepower hour Running this plant at only half-load—that is, using only 18 lights, or their equivalent—would reduce the price to about 3 cents an hour—since the efficiency decreases with smaller load. It is customary to figure an average of 3½ hours a day throughout the year, for all lights. On this basis the cost of gasoline for this one-kilowatt plant would be |