If the moulding is run along the walls flush with the ceiling, as is usual, a branch is made for a wall light, or wall tap, by means of a porcelain "T," or branch-block, which provides the means for running the circuit at right angles to itself without letting the wires come in contact with each other where they cross. Separable current taps should be installed in handy places on all circuits, so that small heating devices may be used without removing the lamps from their sockets. The two wires are bared for half an inch where they run through these current taps, and are fastened by means of brass screws.

"Multiple" Connections

All electric devices for this installation—lamps, irons, vacuum cleaners, motors—must be connected across the circuit—that is, bridged, from one wire to the other. This is called multiple, or shunt connection. There is only one exception to it, in wiring the house. That one exception is installing a wall switch, the ordinary snap switch. Since this wall switch, is, in effect, merely an instrument, which opens or closes a circuit, it should be connected to only one wire, which is cut to provide two ends for the screw connections in the switch. When a moulding branch is run down from the ceiling to some convenient spot for a snap switch (with which to turn the lights of a room on or off), a porcelain "T" is not used. All that is necessary to do is to loop the bottom wire of the circuit down through the branch moulding, and connect it to the switch at a terminal block, or porcelain base.

In wiring lamp fixtures, No. 14 rubber-covered wire will usually prove too large. For this purpose, No. 18 may be used, with one lamp to each loop. Hanging lamps may not be supported by electric lamp cord itself, if there is more than one lamp in the cluster, because the weight is apt to break the electrical connections. In such a case, the lamp should be supported by a chain, and the twisted cord conveying current to the electric bulbs, is woven in the links of the chain. For the pantry, kitchen, woodshed, barn, etc., a single hanging lamp may be suspended from a fielding rosette, as shown in the cut, provided a single knot is tied inside both the rosette and the lamp socket, to make it secure. This makes a very cheap fixture. The rosette of porcelain will cost 15 cents; the lamp socket 20 cents, and the lamp cord suspending the lamp and carrying the current will cost 1-1/2 cents a foot; while a tin shade will cost another 15 cents.



Official Inspection

In all communities, your insurance agent must inspect and pass your wiring before you are permitted to throw the main switch and turn on the electricity. Frequently they require that the moulding be left uncapped, until they have inspected it. If you have more than 660 watts in lamps to a circuit; if your joints are not soldered and well taped; if the moulding is used in any concealed or damp place, the agent is liable to condemn your work and refuse permission to turn on the electricity. However the rules are so clearly defined that it is difficult to go wrong; and a farmer who does his own wiring and takes pride in its appearance is more apt to be right than a professional electrician who is careless at his task. After the work has been passed, tack on the moulding capping, with brads, and paint the moulding to match the woodwork.

Wooden moulding wiring is perfectly satisfactory if properly installed. It is forbidden in many large cities, because of the liability of careless workmanship. It should never be installed in damp places, or out of sight. If the work is well done, the system leaves nothing to be desired; and it has the additional advantage of being cheap, and easily done by any farmer who can use carpenter tools. Farmers with moulding machinery can make their own moulding. The code prescribes it shall be of straight-grained wood; that the raceways for the wires shall be separated by a tongue of wood one-half inch wide; and that the backing shall be at least 3/8 inch thick. It must be covered, inside and out, with at least two coats of moisture-repellant paint. It can be had ready-made for about 2 cents a foot.

Special Heating Circuits

If one plans using electricity for heavy-duty stoves, such as ranges and radiators, it is necessary to install a separate heating circuit. This is the best procedure in any event, even when the devices are all small and suited to lamp circuits. The wire used can be determined by referring to the table for carrying capacity, under the column headed "rubber-covered." A stove or range drawing 40 amperes, would require a No. 4 wire, in moulding. A good plan is to run the heating circuit through the basement, attaching it to the rafters by means of porcelain knobs. Branches can then be run up through the floor to places where outlets are desired. Such a branch circuit should carry fuses suitable to the allowed carrying capacity of the wire.

Knob and Cleat Wiring

Knob and cleat wiring, such as is used extensively for barns and out-buildings, requires little explanation. The wires should not be closer than 2-1/2 inches in open places, and a wider space is better. The wires should be drawn taut, and supported by cleats or knobs at least every four feet. In case of branch circuits, one wire must be protected from the other it passes by means of a porcelain tube. It should never be used in damp places, and should be kept clear of dust and litter, and protected from abrasion.



Knob and tube wiring is frequently used in houses, being concealed between walls or flooring. In this case, the separate wires are stretched on adjoining beams or rafters, and porcelain tubes are used, in passing through cross beams. For a ceiling or wall outlet, a spliced branch is passed through the plaster by means of porcelain tubes or flexible loom.

Wires from the house to the barn should be uniform with transmission wires. At the point of entry to buildings they must be at least six inches apart, and must take the form of the "drop loop" as shown in the illustration. A double-pole entrance switch must be provided, opening downward, with a double-pole fuse. In passing over buildings wires must not come closer than 7 feet to flat roofs, or one foot to a ridge roof. Feed-wires for electric motors should be determined from the table of safe carrying capacities, and should be of liberal size.



CHAPTER IX

THE ELECTRIC PLANT AT WORK

Direct-connected generating sets—Belt drive—The switchboard—Governors and voltage regulators—Methods of achieving constant pressure at all loads: Over-compounding the dynamo; A system of resistances; (A home-made electric radiator); Regulating voltage by means of the rheostat—Automatic devices—Putting the plant in operation.

Dynamos may be connected to water wheels either by means of a belt, or the armature may spin on the same shaft as the water wheel itself. The latter is by far the more desirable way, as it eliminates the loss of power through shafting and belting, and does away altogether with the belts themselves as a source of trouble. An installation with the water wheel and armature on the same shaft is called a "direct-connected set" and is of almost universal use in large power plants.

To be able to use such a direct-connected set, the dynamo must be designed to develop its full voltage when run at a speed identical with that of the water wheel. That is, if the dynamo is wound to be run at a speed of 800 revolutions per minute, it must be driven by a water wheel which runs at this speed and can be governed within narrow limits. Small impulse wheels running under great heads attain high speed, and for such wheels it is possible to obtain a suitable dynamo at low cost. For instance, a 12-inch impulse wheel, running under a 200-foot head will develop 6-3/4 horsepower when running at a speed of 875 revolutions per minute. A dynamo for direct coupling to such a wheel should have a rated speed within 5 per cent of 875 r.p.m.; and, as generators of this speed are to be had from the stock of almost all manufacturers, there would be no extra charge.

When it comes to the larger wheels, however, of the impulse type, or to turbines operating under their usual head the question becomes a little more difficult. In such cases, the speed of the water wheel will vary from 150 revolutions per minute, to 400, which is slow speed for a small dynamo. As a general rule, the higher the speed of a dynamo, the lower the cost; because, to lower the speed for a given voltage, it is necessary either to increase the number of conductors on the armature, or to increase the number of field coils, or both. That means a larger machine, and a corresponding increase in cost.

In practice, in large plants, with alternating-current machines it has become usual to mount the field magnets on the shaft, and build the armature as a stationary ring in whose air space the field coils revolve. This simplifies the construction of slow-speed, large-output dynamos. Such a machine, however, is not to be had for the modest isolated plant of the farmer with his small water-power.



Dynamos can be designed for almost any waterwheel speed, and, among small manufacturers especially, there is a disposition to furnish these special machines at little advance in price over their stock machines. Frequently it is merely a matter of changing the winding on a stock machine. The farmer himself, in many cases, can re-wind an old dynamo to fit the speed requirements of a direct-connected drive if the difference is not too great. All that would be necessary to effect this change would be to get the necessary winding data from the manufacturer himself, and proceed with the winding. This data would give the gauge of wire and the number of turns required for each spool of the field magnets; and the gauge of wire and number of turns required for each slot in the armature. The average boy who has studied electricity (and there is something about electricity that makes it closer to the boy's heart than his pet dog) could do this work. The advantages of direct drive are so many that it should be used wherever possible.

When direct drive cannot be had, a belt must be used, either from a main shaft, or a countershaft. The belt must be of liberal size, and must be of the "endless" variety—with a scarfed joint. Leather belt lacing, or even the better grades of wire lacing, unless very carefully used, will prove unsatisfactory. The dynamo feels every variation in speed, and this is reflected in the lights. There is nothing quite so annoying as flickering lights. Usually this can be traced to the belt connections. Leather lacing forms a knot which causes the lights to flicker at each revolution of the belt. The endless belt does away with this trouble. Most dynamos are provided with sliding bases, by which the machine can be moved one way or another a few inches, to take up slack in the belt. To take advantage of this, the belt must be run in a horizontal line, or nearly so. Vertical belting is to be avoided.

The dynamo is mounted on a wooden base, in a dry location where it is protected from the weather, or dampness from any source. It must be mounted firmly, to prevent vibration when running up to speed; and the switchboard should occupy a place within easy reach. Wires running from the dynamo to the switchboard should be protected from injury, and must be of ample size to carry the full current of the machine without heating. A neat way is to carry them down through the flooring through porcelain tubes, thence to a point where they can be brought up at the back of the switchboard. If there is any danger of injury to these mains they may be enclosed in iron pipe. Keep the wires out of sight as much as possible, and make all connections on the back of the switchboard.

The Switchboard



The switchboard is constructed of some fireproof material, preferably slate or marble. When the cost of this material is an item to consider, build a substantial wooden frame for your switchboard. You can then screw asbestos shingles to this to hold the various instruments and with a little care such a switchboard can be made to look business-like, and it is fully as serviceable as the more expensive kind. The switchboard instruments have already been described briefly. They consist of a voltmeter (to measure voltage); an ammeter (to measure the strength of the current drawn, in amperes), a rheostat (to regulate the voltage of the machine to suit the individual requirements); and the usual switches and fuses. The main switch should be so wired that when open it will throw all the current off the line, but still leave the field coils, the voltmeter, and the switchboard lamp in circuit. The main-switch fuses should have a capacity about 50 per cent in excess of the full load of the dynamo. If the machine is rated for 50 amperes, 75-ampere fuses should be installed. This permits throwing on an overload in an emergency; and at the same time guards against a short circuit. If the capacity of the machine is under 30 amperes, plug fuses, costing 3 cents each, can be used. If it is above this capacity, cartridge fuses, costing a little more, are required. A supply of these fuses should be kept handy at all times.

Governors and Voltage Regulators



The necessity for water wheel governors will vary with conditions. As a general rule, it may be said that reaction turbines working under a low head with a large quantity of water do not require as much governing as the impulse wheel, working under high heads with small quantities of water. When governing is necessary at all, it is because the prime mover varies in speed from no load to full load. Planning one's plant with a liberal allowance of power—two water horsepower to one electrical horsepower is liberal—reduces the necessity of governors to a minimum. As an instance of this, the plant described in some detail in Chapters One and Six of this volume, runs without a governor.

However, a surplus of water-power is not usual. Generally plants are designed within narrow limits; and then the need of a governor becomes immediately apparent. There are many designs of governors on the market, the cheapest being of the centrifugal type, in which a pair of whirling balls are connected to the water wheel gate by means of gears, and open or close the gate as the speed lowers or rises.

Constant speed is necessary because voltage is directly dependent on speed. If the speed falls 25 per cent, the voltage falls likewise; and a plant with the voltage varying between such limits would be a constant source of annoyance, as well as expense for burned-out lamps.

Since constant voltage is the result aimed at by the use of a governor, the same result can be attained in other ways, several of which will be explained here briefly.

Over-Compounding

(1) Over-compounding the dynamo. This is simple and cheap, if one buys the right dynamo in the first instance; or if he can do the over-compounding himself, by the method described in the concluding paragraphs of Chapter Seven. If it is found that the speed of the water wheel drops 25 per cent between no load and full load, a dynamo with field coils over-compounded to this extent would give a fairly constant regulation. If you are buying a special dynamo for direct drive, your manufacturer can supply you with a machine that will maintain constant voltage under the normal variations in speed of your wheel.

A System of Resistances

(2) Constant load systems. This system provides that the dynamo shall be delivering a fixed amount of current at all times, under which circumstances the water wheel would not require regulation, as the demands on it would not vary from minute to minute or hour to hour.

This system is very simply arranged. It consists of having a set of "resistances" to throw into the circuit, in proportion to the amount of current used.

Let us say, as an example, that a 50-ampere generator is used at a pressure of 110 volts; and that it is desirable to work this plant at 80 per cent load, or 40 amperes current draft. When all the lights or appliances were in use, there would be no outside "resistance" in the circuit. When none of the lights or appliances were in use (as would be the case for many hours during the day) it would be necessary to consume this amount of current in some other way—to waste it. A resistance permitting 40 amperes of current to flow, would be necessary. Of what size should this resistance be?

The answer is had by applying Ohm's Law, explained in Chapter Five. The Law in this case, would be read R = E/C. Therefore, in this case R = 110/40 = 2-3/4 ohms resistance, would be required, switched across the mains, to keep the dynamo delivering its normal load.

The cheapest form of this resistance would be iron wire. In place of iron wire, German silver wire could be used. German silver wire is to be had cheaply, and is manufactured in two grades, 18% and 30%, with a resistance respectively 18 and 30 times that of copper for the same gauge. Nichrome wire has a resistance 60 times that of copper; and manganin wire has a resistance 65 times that of copper, of the same gauge.

First figure the number of feet of copper wire suitable for the purpose. Allowing 500 circular mills for each ampere, the gauge of the wire should be 40 x 500 = 20,000 circular mills, or approximately No. 7 B. & S. gauge. How many feet of No. 7 copper wire would give a resistance of 2-3/4 ohms? Referring to the copper wire table, we find that it requires 2006.2 of No. 7 wire to make one ohm. Then 2-3/4 ohms would require 5,517 feet.

Since 30 per cent German silver wire is approximately 30 times the resistance of copper, a No. 7 German silver wire, for this purpose, would be 1/30 the length of the copper wire, or 186 feet. If nichrome wire were used, it would be 1/60th the length of copper for the same gauge, or 93 feet. This resistance wire can be wound in spirals and made to occupy a very small space. As long as it is connected in circuit, the energy of the dynamo otherwise consumed as light would be wasted as heat. This heat could be utilized in the hot water boiler or stove when the lights were turned off.

In actual practice, however, the resistance necessary to keep the dynamo up to full load permanently, would not be furnished by one set of resistance coils. Each lamp circuit would have a set of resistance coils of its own. A double-throw switch would turn off the lamps and turn on the resistance coils, or vice versa.

Let us say a lamp circuit consisted of 6 carbon lamps, of 16 candlepower each. It would consume 6 x 1/2 ampere, or 3 amperes of current, and interpose a resistance of 36.6 ohms—say 37 ohms. Three amperes would require a wire of at least 1,500 circular mills in area for safety. This corresponds to a No. 18 wire. A No. 18 copper wire interposes a resistance of one ohm, for each 156.5 feet length. For 37 ohms, 5,790 feet would be required, for copper wire, which of course would be impractical. Dividing by 30 gives 193 feet for 30% German silver wire; and dividing by 60 gives 96 feet of nichrome wire of the same gauge.

It is simple to figure each circuit in this way and to construct resistance units for each switch. Since the resistance units develop considerable heat, they must be enclosed and protected.

A Home-made Stove or Radiator

While we are on the subject of resistance coils it might be well here to describe how to make stoves for cooking, and radiators for heating the house, at small expense. These stoves consist merely of resistances which turn hot—a dull red—when the current is turned on. Iron wire, German silver wire, or the various trade brands of resistance wire, of which nichrome, calido, and manganin are samples, can be used. In buying this wire, procure the table of resistance and carrying capacity from the manufacturers. From this table you can make your own radiators to keep the house warm in winter. Iron wire has the disadvantage of oxidizing when heated to redness, so that it goes to pieces after prolonged use. It is cheap, however, and much used for resistance in electrical work.

Let us say we wish to heat a bathroom, a room 6 x 8, and 8 feet high—that is a room containing 384 cubic feet of air space. Allowing 2 watts for each cubic foot, we would require 768 watts of current, or practically 7 amperes at 110 volts. What resistance would be required to limit the current to this amount? Apply Ohm's Law, as before, and we have R equals E divided by C, or R equals 110 divided by 7, which is 15.7 ohms. Forty-two feet of No. 20 German silver wire would emit this amount of heat and limit the current output to 7 amperes. In the Far West, it is quite common, in the outlying district, to find electric radiators made out of iron pipe covered with asbestos, on which the requisite amount of iron wire is wound and made secure. This pipe is mounted in a metal frame. Or the frame may consist of two pipes containing heating elements; and a switch, in this case, is so arranged that either one or two heating elements may be used at one time, according to the weather. An ingenious mechanic can construct such a radiator, experimenting with the aid of an ammeter to ascertain the length of wire required for any given stove.

Regulating Voltage at Switchboards

The voltage of any given machine may be regulated, within wide limits, by means of the field rheostat on the switchboard.

A dynamo with a rated speed of 1,500 revolutions per minute, for 110 volts, will actually attain this voltage at as low as 1,200 r.p.m. if all the regulating resistance be cut out. You can test this fact with your own machine by cutting out the resistance from the shunt field entirely, and starting the machine slowly, increasing its speed gradually, until the voltmeter needle registers 110 volts. Then measure the speed. It will be far below the rated speed of your machine.

If, on the other hand, the speed of such a machine runs up to 2,500 or over—that is, an excess of 67%—the voltage would rise proportionally, unless extra resistance was cut in. By cutting in such resistance—by the simple expedient of turning the rheostat handle on the switchboard,—the field coils are so weakened that the voltage is kept at the desired point in spite of the excessive speed of the machine. Excessive speeds are to be avoided, as a rule, because of mechanical strain. But within a wide range, the switchboard rheostat can be used for voltage regulation.

As it would be a source of continual annoyance to have to run to the switchboard every time the load of the machine was varied greatly this plan would not be practical for the isolated plant, unless the rheostat could be installed,—with a voltmeter—in one's kitchen. This could be done simply by running a small third wire from the switchboard to the house. Then, when the lights became dim from excessive load, a turn of the handle would bring them back to the proper voltage; and when they flared up and burned too bright, a turn of the handle in the opposite direction would remedy matters. By this simple arrangement, any member of the family could attend to voltage regulation with a minimum of bother.

Automatic Devices

There are several automatic devices for voltage regulation at the switchboard on the market. These consist usually of vibrator magnets or solenoids, in which the strength of the current, varying with different speeds, reacts in such a way as to regulate field resistance. Such voltage regulators can be had for $40 or less, and are thoroughly reliable.

* * * * *

To sum up the discussion of governors and voltage regulators: If you can allow a liberal proportion of water-power, and avoid crowding your dynamo, the chances are you will not need a governor for the ordinary reaction turbine wheel. Start your plant, and let it run for a few days or a few weeks without a governor, or regulator. Then if you find the operation is unsatisfactory, decide for yourself which of the above systems is best adapted for your conditions. Economy as well as convenience will affect your decision. The plant which is most nearly automatic is the best; but by taking a little trouble and giving extra attention, a great many dollars may be saved in extras.

Starting the Dynamo

You are now ready to put your plant in operation. Your dynamo has been mounted on a wooden foundation, and belted to the countershaft, by means of an endless belt.

See that the oil cups are filled. Then throw off the main switch and the field switch at the switchboard; open the water gate slowly, and occasionally test the speed of the dynamo. When it comes up to rated speed, say 1,500 per minute, let it run for a few minutes, to be sure everything is all right.

Having assured yourself that the mechanical details are all right, now look at the voltmeter. It is probably indicating a few volts pressure, from 4 to 8 or 10 perhaps. This pressure is due to the residual magnetism in the field cores, as the field coils are not yet connected. If by any chance, the needle does not register, or is now back of 0, try changing about the connections or the voltmeter on the back of the switchboard.

Now snap on the field switch. Instantly the needle will begin to move forward, though slowly; and it will stop. Turn the rheostat handle gradually; as you advance it, the voltmeter needle will advance. Finally you will come to a point where the needle will indicate 110 volts.

If you have designed your transmission line for a drop of 5 volts at half-load, advance the rheostat handle still further, until the needle points to 115 volts. Let the machine run this way for some time. When assured all is right, throw on the main switch, and turn on the light at the switchboard. Then go to the house and gradually turn on lights. Come back and inspect the dynamo as the load increases. It should not run hot, nor even very warm, up to full load. Its brushes should not spark, though a little sparking will do no harm.

Your plant is now ready to deliver current up to the capacity of its fuses. See that it does not lack good lubricating oil, and do not let its commutator get dirty. The commutator should assume a glossy chocolate brown color. If it becomes dirty, or the brushes spark badly, hold a piece of fine sandpaper against it. Never use emery paper! If, after years of service, it becomes roughened by wear, have it turned down in a lathe. Occasionally, every few weeks, say, take the brushes out and clean them with a cloth. They will wear out in the course of time and can be replaced for a few cents each. The bearings may need replacing after several years' continuous use.

Otherwise your electric plant will take care of itself. Keep it up to speed, and keep it clean and well oiled. Never shut it down unless you have to. In practice, dynamos run week after week, year after year, without stopping. This one, so long as you keep it running true to form, will deliver light, heat and power to you for nothing, which your city cousin pays for at the rate of 10 cents a kilowatt-hour.



PART III

GASOLINE ENGINES, WINDMILLS, ETC. THE STORAGE BATTERIES



CHAPTER X

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 cooperative 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 generate enough electricity for lighting the farm house at small expense.

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 special type of engine be used to insure constant speed.

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 power stroke. This results in one power impulse in each cylinder every two revolutions of the crank shaft. On its first down stroke, the piston sucks in gas. On its first up stroke, it compresses the gas. At the height of this stroke, the gas is exploded by means of the electric spark and the piston is driven down, on its power stroke. The fourth stroke is called the scavening stroke, and expels the burned gas. This completes the cycle.

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 current direct to lamps requires a steady flow of power, the single-cylinder gas or gasoline engine of the four-cycle type is not satisfactory as a rule. The lights will flicker with every other revolution of the fly wheel. This would be of no importance if the current was being used to charge a storage battery—and right here lies the reason why a cheaper engine may be used in connection with a storage battery than when the dynamo supplies the current direct for lighting.

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 out, and fresh gas drawn in before the up stroke begins.

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 described in previous chapters for water-power plants. They are practically automatic in operation and will run for hours without attention, except as to oil and gasoline supply. They may be installed in the woodshed or cellar without annoyance due to noise or vibration. It is necessary to start them, of course, when light or power is desired, and to stop them when no current is being drawn. There have appeared several makes on the market in which starting and stopping are automatic. Storage batteries are used in connection with these latter plants for starting the engine. When a light is turned on, or current is drawn for any purpose, an automatic switch turns the dynamo into a motor, and it starts the engine by means of the current stored in the battery. Instantly the engine has come up to speed, the motor becomes a dynamo again and begins to deliver current. When the last light is turned off, the engine stops automatically.

Since the installation of a direct-connected standard voltage plant of this type is similar in every respect, except as to motive power, to the hydro-electric plant, its cost, with this single exception, is the same. The same lamps, wire, and devices are used.

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 such size that it will be operating on at least three-fourths load under normal draft of current. Norman H. Schneider, in his book "Low Voltage Electric Lighting," gives the following table of proportions between the engine and dynamo:

Actual watts Actual Horsepower Nearest engine size 150 .5 1/2 225 .7 3/4 300 .86 1 450 1.12 1-1/4 600 1.5 1-1/2 750 1.7 1-3/4 1000 2.3 2-1/2 2000 4.5 5 4000 9.0 10

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 2-1/2 horsepower, and consuming, let us say, 1-1/4 pint of gasoline for each horsepower hour (to make allowance for lower efficiency in small engines). That would be 3.125 pints of gasoline per hour. Allowing a ten per cent loss of current in wiring, we have 900 watts of electricity to use, for this expenditure of gasoline. This would light 900 / 25 = 36 lamps of 25 watts each, a liberal allowance for house and barn, and permitting the use of small cooking devices and other conveniences when part of the lights were not in use. With gasoline selling at 12 cents a gallon, the use of this plant for an hour at full capacity would cost $0.047. Your city cousin pays 9 cents for the same current on a basis of 10 cents per kilowatt-hour; and in smaller towns where the rate is 15 cents, he would pay 13-1/2 cents.

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 3-1/2 hours a day throughout the year, for all lights. On this basis the cost of gasoline for this one-kilowatt plant would be 16-1/2 cents a day for full load, and approximately 10-1/2 cents a day for half-load. This is extremely favorable, as compared with the cost of electric current in our cities and towns, at the commercial rate, especially when one considers that light and power are to be had at any place or at any time on the farm simply by starting the engine. A smaller plant, operating at less cost for fuel, would furnish ample light for most farms; but it is well to remember in this connection plants smaller than one kilowatt are practical for light only, since electric irons, toasters, etc., draw from 400 to 660 watts each. Obviously a plant of 300 watts capacity would not permit the use of these instruments, although it would furnish 10 or 12 lamps of 25 watts each.



CHAPTER XI

THE STORAGE BATTERY

What a storage battery does—The lead battery and the Edison battery—Economy of tungsten lamps for storage batteries—The low-voltage battery for electric light—How to figure the capacity of a battery—Table of light requirements for a farm house—Watt-hours and lamp-hours—The cost of storage battery current—How to charge a storage battery—Care of storage batteries.

For the man who has a small supply of water to run a water wheel a few hours at a time, or who wishes to store electricity while he is doing routine jobs with a gasoline engine or other source of power, the storage battery solves the problem. The storage battery may be likened to a tank of water which is drawn on when water is needed, and which must be re-filled when empty. A storage battery, or accumulator is a device in which a chemical action is set up when an electric current is passed through it. This is called charging. When such a battery is charged, it has the property of giving off an electric current by means of a reversed chemical action when a circuit is provided, through a lamp or other connection. This reversed action is called discharging. Such a battery will discharge nearly as much current as is required originally to bring about the first chemical action.

There are two common types of storage battery—the lead accumulator, made up of lead plates (alternately positive and negative); and the two-metal accumulator, of which the Edison battery is a representative, made up of alternate plates of iron and nickel. In the lead accumulator, the "positive" plate may be recognized by its brown color when charging, while the "negative" plate is usually light gray, or leaden in color. The action of the charging current is to form oxides of lead in the plates; the action of the discharging current is to reduce the oxides to metallic lead again. This process can be repeated over and over again during the life of the battery.

Because of the cost of the batteries themselves, it is possible (from the viewpoint of the farmer and the size of his pocketbook) to store only a relatively small amount of electric current. For this reason, the storage battery was little used for private plants, where expense is a considerable item, up to a few years ago. Carbon lamps require from 3-1/2 to 4 watts for each candlepower of light they give out; and a lead battery capable of storing enough electricity to supply the average farm house with light by means of carbon lamps for three or four days at a time without recharging, proved too costly for private use.

The Tungsten Lamp

With the advent of the new tungsten lamp, however, reducing the current requirements for light by two-thirds, the storage battery immediately came into its own, and is now of general use.

Since incandescent lamps were first invented scientists have been trying to find some metal of high fusion to use in place of the carbon filament of the ordinary lamp. The higher the fusing point of this filament of wire, the more economical would be the light. Edison sought, thirty years ago, for just the qualities now found in tungsten metal. Tungsten metal was first used for incandescent lamps in the form of a paste, squirted into the shape of a thread. This proved too fragile. Later investigators devised means of drawing tungsten into wire; and it is tungsten wire that is now used so generally in lighting. A tungsten lamp has an average efficiency of 1-1/4 watts per candlepower, compared with 3-1/2 to 4 watts of the old-style carbon lamp. In larger sizes the efficiency is as low as .9 watt per candlepower; and only recently it has been found that if inert nitrogen gas is used in the glass bulb, instead of using a high vacuum as is the general practice, the efficiency of the lamp becomes still higher, approaching .5 watt for each candlepower in large lamps. This new nitrogen lamp is not yet being manufactured in small domestic sizes, though it will undoubtedly be put on the market in those sizes in the near future.



The tungsten lamp, requiring only one-third as much electric current as the carbon lamp, for the same amount of light, reduces the size (and the cost) of the storage battery in the same degree, thus bringing the storage battery within the means of the farmer. Some idea of the power that may be put into a small storage battery is to be had from the fact that a storage battery of only 6 volts pressure, such as is used in self-starters on automobiles, will turn a motor and crank a heavy six-cylinder engine; or it will run the automobile, without gasoline, for a mile or more with its own accumulated store of electric current.

The Low Voltage Battery

The 30-volt storage battery has become standard for small lighting plants, since the introduction of the tungsten lamp. Although the voltage of each separate cell of this battery registers 2.5 volts when fully charged, it falls to approximately 2 volts per cell immediately discharging begins. For this reason, it is customary to figure the working pressure of each cell at 2 volts. This means that a 30-volt battery should consist of at least 15 cells. Since, however, the voltage falls below 2 for each cell, as discharging proceeds, it is usual to include one additional cell for regulating purposes. Thus, the ordinary 30-volt storage battery consists of 16 cells, the last cell in the line remaining idle until the lamps begin to dim, when it is switched in by means of a simple arrangement of connections. This maintains a uniform pressure of 30 volts from the beginning to the end of the charge, at the lamp socket.

We saw in earlier chapters that the 110-volt current is the most satisfactory, under all conditions, where the current is to be used for heating and small power, as well as light. But a storage battery of 110 volts would require at least 55 cells, which would make it too expensive for ordinary farm use. As a 30-volt current is just as satisfactory for electric light, this type has become established, in connection with the battery, and it is used for electric lighting only, as a general rule.

Batteries are rated first, as to voltage; second, as to their capacity in ampere hours—that is, the number of amperes that may be drawn from them in a given number of hours. Thus, a battery rated at 60 ampere hours would give 60 amperes, at 30 volts pressure, for one hour; 30 amperes for 2 hours; 15 amperes for 4 hours; 7-1/2 amperes for 8 hours; 3-3/4 amperes for 16 hours; etc., etc. In practice, a battery should not be discharged faster than its 8-hour rate. Thus, a 60-ampere hour battery should not be drawn on at a greater rate than 7-1/2 amperes per hour.

This 8-hour rate also determines the rate at which a battery should be re-charged, once it is exhausted. Thus, this battery should be charged at the rate of 7-1/2 amperes for 8 hours, with another hour added to make up for losses that are bound to occur. A battery of 120-ampere hour capacity should be charged for 8 or 9 hours at the rate of 120 / 8, or 15 amperes, etc.

To determine the size of battery necessary for any particular instance, it is necessary first to decide on the number of lamps required, and their capacity. Thirty-volt lamps are to be had in the market in sizes of 10, 15 and 20 watts; they yield respectively 8, 12, and 16 candlepower each. Of these the 20-watt lamp is the most satisfactory for the living rooms; lamps of 10 or 15 watts may be used for the halls, the bathroom and the bedrooms. At 30 volts pressure these lamps would require a current of the following density in amperes:

Candle Power 30-volt lamp Amperes 8 10 watts 0.33 12 15 watts 0.50 16 20 watts 0.67

Let us assume, as an example, that Farmer Brown will use 20-watt lamps in his kitchen, dining room, and sitting room; and 10-watt lamps in the halls, bathroom, and bedrooms. His requirements may be figured either in lamp hours or in watt-hours. Since he is using two sizes of lamps, it will be simpler to figure his requirements in watt-hours. Thus:

Number Size of Hours Watt- Room of lamps lamps burned hours

Kitchen 1 20 4 80 Dining room 2 20 2 80 Sitting room 3 20 4 240 (3) Bedrooms 1 (each) 10 1 30 Bathroom 1 10 2 20 (2) Halls 1 (each) 10 4 80 Pantry 1 10 1 10 Cellar 1 10 1 10 —— Total 550

Since amperes equal watts divided by volts, the number of ampere hours required in this case each night would be 550 / 30 = 18.3 ampere hours; or approximately 4-1/2 amperes per hour for 4 hours.

Say it is convenient to charge this battery every fourth day. This would require a battery of 4 x 18.3 ampere hours, or 73.2 ampere hours. The nearest size on the market is the 80-ampere hour battery, which would be the one to use for this installation.

To charge this battery would require a dynamo capable of delivering 10 amperes of current for 9 hours. The generator should be of 45 volts pressure (allowing 2-1/2 volts in the generator for each 2 volts of battery) and the capacity of the generator would therefore be 450 watts. This would require a 1-1/4 horsepower gasoline engine. At 1-1/4 pints of gasoline for each horsepower, nine hours work of this engine would consume 14 pints of gasoline—or say 16 pints, or two gallons. At 12 cents a gallon for gasoline, lighting your house with this battery would cost 24 cents for four days, or 6 cents a day. Your city cousin, using commercial current, would pay 5-1/2 cents a day for the same amount of current at 10 cents a kilowatt-hour; or 8-1/4 cents at a 15-cent rate. If the battery is charged by the farm gasoline engine at the same time it is doing its other work, the cost would be still less, as the extra gasoline required would be small.

This figure does not take into account depreciation of battery and engine. The average farmer is too apt to overlook this factor in figuring the cost of machinery of all kinds, and for that reason is unprepared when the time comes to replace worn-out machinery. The dynamo and switchboard should last a lifetime with ordinary care, so there is no depreciation charge against them. The storage battery, a 30-volt, 80-ampere hour installation, should not cost in excess of $100; and, if it is necessary to buy a gasoline engine, a 1-1/4 horsepower engine can be had for $50 or less according to the type. Storage batteries of the lead type are sold under a two-years' guarantee—which does not mean that their life is limited to that length of time. With good care they may last as long as 10 years; with poor care it may be necessary to throw them away at the end of a year. The engine should be serviceable for at least 10 years, with ordinary replacements; and the storage battery may last from 6 to 10 years, with occasional renewal of parts. If it were necessary to duplicate both at the end of ten years, this would make a carrying charge of $1.25 a month for depreciation, which must be added to the cost of light.

Figuring by Lamp Hours

If all the lamps are to be of the same size—either ten, fifteen, or twenty watts, the light requirements of a farm house can be figured readily by lamp hours. In that event, the foregoing table would read as follows:

Lamp hours Kitchen, 1 lamp, 4 hours 4 Sitting room, 3 lamps, 4 hours each 12 Dining room, 2 lamps, 2 hours each 4 Bedrooms, 3 lamps, 1 hour each 3 Halls, 2 lamps, 4 hours each 8 Bathroom, 1 lamp, 2 hours 2 Pantry and cellar, 2 lamps, 1 hour each 2

To determine the ampere hours from this table, multiply the total number of lamp hours by the current in amperes required for each lamp. As 10, 15, and 20-watt tungsten lamps require .33, .50 and .67 amperes, respectively at 30 volts pressure, the above requirements in ampere hours would be 12, 17-1/2, or 24 ampere hours, according to the size of lamp chosen. This gives the average current consumption for one night. If it is desired to charge the battery twice a week on the average, multiply the number of lamp hours by 4, to get the size of battery required.

The foregoing illustration is not intended to indicate average light requirements for farms, but is given merely to show how a farmer may figure his own requirements. In some instances, it will be necessary to install a battery of 120 or more ampere hours, whereas a battery of 40 or 60 ampere hours would be quite serviceable in other instances. It all depends on how much light you wish to use and are willing to pay for, because with a storage battery the cost of electric light is directly in proportion to the number of lights used.

As a general rule, a larger generator and engine are required for a larger battery—although it is possible to charge a large battery with a small generator and engine by taking more time for the operation.

How to Charge a Storage Battery

Direct current only can be used for charging storage batteries. In the rare instance of alternating current only being available, it must be converted into direct current by any one of the many mechanical, chemical, or electrical devices on the market—that is, the alternating current must be straightened out, to flow always in one direction.

A shunt-wound dynamo must be used; else, when the voltage of the battery rises too high, it may "back up" and turn the dynamo as a motor, causing considerable damage. If a compound dynamo is already installed, or if it is desired to use such a machine for charging storage batteries, it can be done simply by disconnecting the series windings on the field coils, thus turning the machine into a shunt dynamo.

The voltage of the dynamo should be approximately 50 per cent above the working pressure of the battery. For this reason 45-volt machines are usually used for 30 or 32-volt batteries. Higher voltages may be used, if convenient. Thus a 110-volt dynamo may be used to charge a single 2-volt cell if necessary, although it is not advisable.

Direction of Current

Electricity flows from the positive to the negative terminal. A charging current must be so connected that the negative wire of the dynamo is always connected to the negative terminal of the battery, and the positive wire to the positive terminal. As the polarity is always marked on the battery, there is little danger of making a mistake in this particular.

When the storage battery is charged, and one begins to use its accumulation of energy, the current comes out in the opposite direction from which it entered in charging. In this respect, a storage battery is like a clock spring, which is wound up in one direction, and unwinds itself in the other. With all storage battery outfits, an ammeter (or current measure) is supplied with zero at the center. When the battery is being charged, the indicating needle points in one direction in proportion to the strength of the current flowing in; and when the battery is being discharged, the needle points in the opposite direction, in proportion to the strength of the current flowing out.

Sometimes one is at loss, in setting about to connect a battery and generator, to know which is the positive and which the negative wire of the generator. A very simple test is as follows:

Start the generator and bring it up to speed. Connect some form of resistance in "series" with the mains. A lamp in an ordinary lamp socket will do very well for this resistance. Dip the two ends of the wire (one coming from the generator, the other through the lamp) into a cup of water, in which a pinch of salt is dissolved. Bring them almost together and hold them there. Almost instantly, one wire will begin to turn bright, and give off bubbles. The wire which turns bright and gives off bubbles is the negative wire. The other is the positive.



Care of Battery

Since specific directions are furnished with all storage batteries, it is not necessary to go into the details of their care here. Storage battery plants are usually shipped with all connections made, or plainly indicated. All that is necessary is to fill the batteries with the acid solution, according to directions, and start the engine. If the engine is fitted with a governor, and the switchboard is of the automatic type, all the care necessary in charging is to start the engine. In fact, many makes utilize the dynamo as a "self-starter" for the engine, so that all that is necessary to start charging is to throw a switch which starts the engine. When the battery is fully charged, the engine is stopped automatically.

The "electrolyte" or solution in which the plates of the lead battery are immersed, is sulphuric acid, diluted with water in the proportion of one part of acid to five of water, by volume.

The specific gravity of ordinary commercial sulphuric acid is 1.835. Since its strength is apt to vary, however, it is best to mix the electrolyte with the aid of the hydrometer furnished with the battery. The hydrometer is a sealed glass tube, with a graduated scale somewhat resembling a thermometer. The height at which it floats in any given solution depends on the density of the solution. It should indicate approximately 1.15 for a storage battery electrolyte before charging. It should not be over 1.15—or 1,150 if your hydrometer reads in thousandths.

Only pure water should be used. Distilled water is the best, but fresh clean rain water is permissible. Never under any circumstances use hydrant water, as it contains impurities which will injure the battery, probably put it out of commission before its first charge.

Pour the acid into the water. Never under any circumstances pour the water into the acid, else an explosion may occur from the heat developed. Mix the electrolyte in a stone crock, or glass container, stirring with a glass rod, and testing from time to time with a hydrometer. Let it stand until cool and then pour it into the battery jars, filling them to 1/2 inch above the top of the plates.

Then begin charging. The first charge will probably take a longer time than subsequent charges. If the installation is of the automatic type, all that is necessary is to start the engine. If it is not of the automatic type, proceed as follows:

First be sure all connections are right. Then start the engine and bring the dynamo up to its rated speed. Adjust the voltage to the pressure specified. Then throw the switch connecting generator to battery. Watch the ammeter. It should register in amperes, one-eighth of the ampere-hour capacity of the battery, as already explained. If it registers too high, reduce the voltage of the generator slightly, by means of the field rheostat connected to the generator. This will also reduce the amperes flowing. If too low, raise the voltage until the amperes register correctly. Continue the charging operation until the cells begin to give off gas freely; or until the specific gravity of the electrolyte, measured by the hydrometer, stands at 1.24. Your battery is now fully charged. Throw the switch over to the service line, and your accumulator is ready to furnish light if you turn on your lamps.

Occasionally add distilled water to the cells, to make up for evaporation. It is seldom necessary to add acid, as this does not evaporate. If the battery is kept fully charged, it will not freeze even when the thermometer is well below zero.

A storage battery should be installed as near the house as possible—in the house, if possible. Since its current capacity is small, transmission losses must be reduced to a minimum.

In wiring the house for storage battery service, the same rules apply as with standard voltage. Not more than 6 amperes should be used on any single branch circuit. With low voltage batteries (from 12 volts to 32 volts) it is well to use No. 10 or No. 12 B. & S. gauge rubber-covered wire, instead of the usual No. 14 used with standard voltage. The extra expense will be only a few cents for each circuit, and precious volts will be saved in distribution of the current.



CHAPTER XII

BATTERY CHARGING DEVICES

The automatic plant most desirable—How an automobile lighting and starting system works—How the same results can be achieved in house lighting, by means of automatic devices—Plants without automatic regulation—Care necessary—The use of heating devices on storage battery current—Portable batteries—An electricity "route"—Automobile power for lighting a few lamps.

The water-power electric plants described in preceding chapters are practically automatic in operation. This is very desirable, as such plants require the minimum of care. It is possible to attain this same end with a storage battery plant.

Automatic maintenance approaches a high degree of perfection in the electric starting and lighting device on a modern automobile. In this case, a small dynamo geared to the main shaft is running whenever the engine is running. It is always ready to "pump" electricity into the storage battery when needed. An electric magnet, wound in a peculiar manner, automatically cuts off the charging current from the dynamo, when the battery is "full;" and the same magnet, or "regulator," permits the current to flow into the battery when needed. The principle is the same as in the familiar plumbing trap, which constantly maintains a given level of water in a tank, no matter how much water may be drawn from the tank. The result, in the case of the automobile battery, is that the battery is always kept fully charged; for no sooner does the "level" of electricity begin to drop (when used for starting or lighting) than the generator begins to charge. This is very desirable in more ways than one. In the first place, the energy of the battery is always the same; and in the second place, the mere fact that the battery is always kept fully charged gives it a long life.

The same result can be achieved in storage battery plants for house lighting, where the source of power is a gasoline or other engine engaged normally in other work. Then your electric current becomes merely a by-product of some other operation.

Take a typical instance where such a plant would be feasible: Farmer Brown has a five horsepower gasoline engine—an ordinary farm engine for which he paid probably $75 or $100. Electric light furnished direct from such an engine would be intolerable because of its constant flickering. This five horsepower engine is installed in the milk room of the dairy, and is belted to a countershaft. This countershaft is belted to the vacuum pump for the milking machine, and to the separator, and to a water pump, any one of which may be thrown into service by means of a tight-and-loose pulley. This countershaft is also belted to a small dynamo, which runs whenever the engine is running. The milking machine, the separator, and the water pump require that the gasoline engine be run on the average three hours each day.

The dynamo is connected by wires to the house storage battery through a properly designed switchboard. The "brains" of this switchboard is a little automatic device (called a regulator or a circuit breaker), which opens and shuts according to the amount of current stored in the battery and the strength of the current from the generator. When the battery is "full," this regulator is "open" and permits no current to flow. Then the dynamo is running idle, and the amount of power it absorbs from the gasoline engine is negligible. When the "level" of electricity in the battery falls, due to drawing current for light, the regulator is "shut," that is, the dynamo and battery are connected, and current flows into the battery.

These automatic instruments go still farther in their brainy work. They do not permit the dynamo to charge the battery when the voltage falls below a fixed point, due to the engine slowing down; neither do they permit the dynamo current to flow when the voltage gets too high due to sudden speeding up of the engine.

Necessarily, an instrument which will take care of a battery in this way, is intricate in construction. That is not an argument against it however. A watch is intricate, but so long as we continue to wind it at stated intervals, it keeps time. So with this storage battery plant: so long as Farmer Brown starts his engine to do his farm chores every day, his by-product of electricity is stored automatically.

Such installations are not expensive. A storage battery capable of lighting 8 tungsten lamps, of 16 candlepower each, continuously for 8 hours (or fewer lamps for a longer time); a switchboard containing all the required regulating instruments; and a dynamo of suitable size, can be had for from $250 to $300. All that is necessary to put such a plant in operation, is to belt the dynamo to the gasoline engine so that it will run at proper speed; and to connect the wires from dynamo to switchboard, and thence to the house service. The dynamo required for the above plant delivers 10 amperes at 45 volts pressure, or 10 x 45 = 450 watts. A gasoline, gas, or oil engine, or a windmill of 1-1/2 horsepower furnishes all the power needed. If the farmer uses his engine daily, or every other day, for other purposes, the cost of power will be practically negligible. With this system electric lights are available at any time day or night; and when the gasoline engine is in service daily for routine farm chores, the battery will never run low.

This system is especially desirable where one uses a windmill for power. The speed of the windmill is constantly fluctuating, so much so in fact that it could not be used for electric light without a storage battery. But when equipped with a regulator on the switchboard which permits the current to flow only when the battery needs it, and then only when the speed of the windmill is correct, the problem of turning wind power into electric light is solved.

* * * * *

If the farmer does not desire to go to the additional expense of automatic regulation, there are cheaper plants, requiring attention for charging. These plants are identical with those described above, except they have no regulators. With these plants, when the battery runs low (as is indicated by dimming of the lights) it is necessary to start the engine, bring it up to speed, adjust the dynamo voltage to the proper pressure, and throw a switch to charge the battery. For such plants it is customary to run the engine to charge the battery twice a week. It is necessary to run the engine from 8 to 10 hours to fully charge the discharged battery. When the battery approaches full charge, the fact is evidenced by so-called "gassing" or giving off of bubbles. Another way to determine if the battery is fully charged is by means of the voltmeter, as the volts slowly rise to the proper point during the process of charging. A third way, and probably the most reliable is by the use of the hydrometer. The voltage of each cell when fully charged should be 2.5; it should never be discharged below 1.75 volts. Many storage battery electric light plants on the market are provided with a simple and inexpensive circuit breaker, which automatically cuts off the current and stops the engine when the battery is charged. The current is then thrown from the dynamo to the house service by an automatic switch. If such a circuit breaker is not included, it is necessary to throw the switch by hand when charging is begun or ended.

Since the principal item of first cost, as well as depreciation, in a storage battery electric light plant is the storage battery itself, the smallest battery commensurate with needs is selected. Since the amount of current stored by these batteries is relatively small, electric irons and heating devices such as may be used freely on a direct-connected plant without a battery, are rather expensive luxuries. For instance, an electric iron drawing 400 watts an hour while in use, requires as much energy as 20 tungsten lamps of 16 candlepower each burning for the same length of time. Its rate of current consumption would be over 13 amperes, at 30 volts; which would require a larger battery than needed for light in the average farm home.

The use to which electricity from a storage battery is put, however, is wholly a matter of expense involved; and if one is willing to pay for these rather expensive luxuries, there is no reason why he should not have them. Heating, in any form, by electricity, requires a large amount of current proportionally. As a matter of fact, there is less heat to be had in thermal units from a horsepower-hour of electricity than from three ounces of coal. When one is generating current from water-power, or even direct from gasoline or oil, this is not an argument against electric heating devices. But it becomes a very serious consideration when one is installing a storage battery as the source of current, because of the high initial cost, and depreciation of such a battery.

Farmers who limit the use of their storage battery plants to lighting will get the best service.

Portable Batteries

Abroad it is becoming quite common for power companies to deliver storage batteries fully charged, and call for them when discharged. Without a stretch of the imagination, we can imagine an ingenious farmer possessing a water-power electric plant building up a thriving business among his less fortunate neighbors, with an "electricity" route. It could be made quite as paying as a milk route.



Many communities have water or steam power at a distance too great to transmit 110-volt current by wire economically; and because of lack of expert supervision, they do not care to risk using current at a pressure of 500 volts or higher, because of its danger to human life.

In such a case it would be quite feasible for families to wire their houses, and carry their batteries to the generating plant two or three times a week to be charged. There are a number of portable batteries on the market suitable for such service, at voltages ranging from 6 to 32 volts. The best results would be obtained by having two batteries, leaving one to be charged while the other was in use; and if the generating station was located at the creamery or feed mill, where the farmer calls regularly, the trouble would be reduced to a minimum.

Such a battery would necessarily be small, and of the sealed type, similar to those used in automobiles. It could be used merely for reading lamps—or it could be used for general lighting, according to the expense the farmer is willing to incur for batteries.

An ordinary storage battery used in automobile ignition and lighting systems is of the 6-volt, 60-ampere type, called in trade a "6-60." Lamps can be had for these batteries ranging in sizes from 2 candlepower to 25 candlepower. A lamp of 15 candlepower, drawing 2-1/2 amperes, is used for automobile headlights, and, as any one knows after an experience of meeting a headlight on a dark road, they give a great deal of light. A "6-60" battery keeps one of these lamps running for 24 hours, or two lamps running 12 hours. A minimum of wiring would be required to install such a battery for the reading lights in the sitting room, and for a hanging light in the dining room. The customary gates for charging these batteries in a large city is 10 cents; but in a country plant it could be made less.

To charge such a battery on a 110-volt direct current, it is necessary to install some means of limiting the amount of current, or in other words, the charging rate. This charging rate, for 8 hours should be, as we have seen, one-eighth of the ampere-hour capacity of the battery. Thus a "6-60" battery would require a 7-1/2 ampere current.

Connecting two such batteries in "series" (that is, the negative pole of one battery to the positive pole of the second) would make a 12-volt battery. Ten or twelve such batteries could be connected in "series," and a 110-volt direct current generator would charge them in 8 hours at a 7-1/2 ampere rate.

The diagram on page 259 shows the connections for charging on a 110-volt circuit.

An ordinary 16-candlepower carbon lamp is of 220 ohms resistance, and (by Ohm's Law, C equals E divided by R) permits 1/2 ampere of current to flow. By connecting 15 such lamps across the mains, in parallel, the required 7-1/2 amperes of current would be flowing from the generator through the lamps, and back again. Connect the battery in "series" at any point on either of the two mains, between the lamps and the generator, being careful to connect the positive end to the positive pole of the battery, and vice versa.

Lamps are the cheapest form of resistance; but in case they are not available, any other form of resistance can be used. Iron wire wound in spirals can be used, or any of the many makes of special resistance wire on the market. First it is necessary to determine the amount of resistance required.

We have just seen that the charging rate of a 60-ampere hour battery is 7-1/2 amperes. Applying Ohm's Law here, we find that ohms resistance equals volts divided by amperes, or R = 110/7.5 = 14.67 ohms. With a 220-volt current, the ohms resistance required in series with the storage battery of this size would be 29.33 ohms.

Automobile Power for Lighting

There are many ingenious ways by which an automobile may be utilized to furnish electric light for the home. The simplest is to run wires direct from the storage battery of the self-starting system, to the house or barn, in such a way that the current may be used for reading lamps in the sitting room. By a judicious use of the current in this way, the normal operation of the automobile in the daytime will keep the battery charged for use of the night lamps, and if care is used, such a plan should not affect the life of the battery. Care should be used also, in this regard, not to discharge the battery too low to prevent its utilizing its function of starting the car when it was desired to use the car. However, if the battery were discharged below its starting capacity, by any peradventure, the car could be started by the old-fashioned cranking method.

Using an automobile lighting system for house lighting implies that the car be stored in a garage near the house or barn; as this battery is too low in voltage to permit transmitting the current any distance. One hundred feet, with liberal sized transmission wires is probably the limit.

That such a system is feasible is amply proved by an occurrence recently reported in the daily papers. A doctor summoned to a remote farm house found that an immediate operation was necessary to save the patient's life. There was no light available, except a small kerosene lamp which was worse than nothing. The surgeon took a headlight off his car, strung a pair of wires through a window, and instantly had at his command a light of the necessary intensity.

Another manner in which an automobile engine may be used for house lighting is to let it serve as the charging power of a separate storage battery. The engine can be belted to the generator, in such a case, by means of the fly wheel. Or a form of friction drive can be devised, by means of which the rear wheels (jacked up off the floor) may supply the necessary motive power. In such a case it would be necessary to make allowance for the differential in the rear axle, so that the power developed by the engine would be delivered to the friction drive.



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Cooperation in Agriculture

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"The author has a broad outlook and never fails to suggest that the economic advantages of cooperation may frequently be quite subordinate to the general social and community interests which are fostered through a common undertaking. He writes with the genuine interest of a man having experience and faith in that of which he speaks."—Political Science Quarterly.

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ON SELECTION OF LAND, ETC.

Isaac P. Roberts' The Farmstead $1 50 T. F. Hunt's How to Choose a Farm 1 75 E. S. Cheyney and J. P. Wentling's The Farm Woodlot 1 50 Glenn W. Herrick's Insects Injurious to the Household 1 75

ON TILLAGE, ETC.

F. H. King's The Soil 1 50 Isaac P. Roberts' The Fertility of the Land 1 50 F. H. King's Irrigation and Drainage 1 50 Edward B. Voorhees' Fertilizers 1 25 Edward B. Voorhees' Forage Crops 1 50 J. A. Widtsoe's Dry Farming 1 50 L. H. Bailey's Principles of Agriculture 1 25 S. M. Tracy's Forage Crops for the South 1 50

ON PLANT DISEASES, ETC.

E. C. Lodeman's The Spraying of Plants 1 25

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L. H. Bailey's Garden-Making 1 50 L. H. Bailey's Vegetable-Gardening 1 50 L. H. Bailey's Forcing Book 1 25 L. H. Bailey's Plant Breeding 2 00

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L. H. Bailey's Nursery Book 1 50 L. H. Bailey's Fruit-Growing (New Edition) 1 75 L. H. Bailey's The Pruning Book 1 50 F. W. Card's Bush Fruits 1 50 W. Paddock & O. B. Whipple's Fruit-Growing in Arid Regions 1 50 J. E. Coit's Citrus Fruits Prepar

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The Rural Outlook Set

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THE COUNTRY LIFE MOVEMENT

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THE STATE AND THE FARMER (New Edition)

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It is the relation of the farmer to the government that Professor Bailey here discusses in its varying aspects. He deals specifically with the change in agricultural methods, in the shifting of the geographical centers of farming in the United States, and in the growth of agricultural institutions.

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* * * * *

Transcriber's Notes:

The square root symbol is indicated by sqrt(..)

Exponents are indicated by ^

Bold in a table is indicated by ..

THE END