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Autos for Rural Free Delivery

By Waldon Fawcett

HE United States Postoffice Department has, from time to time during the past few years, been importuned to authorize the employment of automobiles in the Rural Free Delivery Service, but until recently did not look with favor on the proposition. Physical aspects of the country and varying conditions of roads, were cited as among the obstacles; but the chief objection was found in defective mechanism in the construction of most of the motor-cars offered for the use of the country postmen. Lately, however, automobile manufacturers have remedied the objectionable defects of construction; and not only has the Postmaster-General issued an order permitting the use of automobiles and motor-cycles in rural mail service, but the Government has lately conducted a

series of trials with an automobile designed and constructed especially for this class of postal service.

The

The new automobile for rural free delivery was built at Waltham, Mass., and is in type a friction-drive buckboard fitted with mackintosh buggy-top. In this interesting car the power is transmitted through two friction discs. disc on the engine shaft has a metal face, and the wheel which engages upon it is covered with a special fibroid which has remarkable power of adhesion. The power is transmitted to the rear wheels through double chains. The degree of contact between the two discs is regulated by roller-bearing idlers in the rear of the metal disc, which is operated by a foot-lever. This lever has a ratchet action, giving it twenty different degrees of contact, this contact being increased as desired on heavy grades.

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HANDLING MAIL IN THE NEW AUTOMOBILE FOR RURAL FREE DELIVERY.

The engine is four horse-power; and a three-blade fiber fan mounted on the front of the cylinder assists in the aircooling properties. The maximum speed of the car is 25 miles per hour and the normal speed on ordinary roads is 15 to 18 miles per hour. In hill-climbing power-an important qualification for rural free delivery work-the car is claimed to exceed any other motor-car manufactured, regardless of horse-power or weight. In a recent official test, a car of this design climbed a grade of 32 degrees; and with two passengers climbed one of 22 degrees on the reverse gear. The R. F. D. auto weighs 600 pounds; and with the carrier and any quantity of mail that the rural postman is likely to be called upon to carry, the weight will not exceed 900 pounds. The forward part of the body is fitted with a cabinet divided into pigeonholes to be used as receptacles for mail matter; but the arrangement of this mail space is subject

to change in accordance with recommendations of officials of the Postoffice Department.

The mail vehicle has made most satisfactory showings in tests recently held on representative rural mail routes in Virginia and Maryland. These demonstrations, which took the form of regular deliveries of mail according to schedule, by carriers, will be supplemented by further practical tests under winter conditions. The officials of the Postoffice Department are particularly encouraged over the showing made by this automobile by reason of the fact that machines of this type can be furnished to carriers at only $400 each, which is little if any more than the average carrier must expend for a team of horses and vehicle in which to cover his route. Moreover, the operating expense is proportionately low, one car being capable of traveling 120 miles on four gallons of gasoline and less than two pints of oil.

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F you are tempted to reveal

A tale some one to you has told About another, let it pass,

Before you speak, three gates of gold. Three narrow gates-first, "Is it true?" Then, Is it needful?" In your mind Give truthful answer. And the next Is last and narrowest, "Is it kind?" And if, to reach your lips at last, It passes through these gateways three, Then you may tell the tale, nor fear What the result of speech may be.

CHALK
TALKS

by CARL S. DOW.

8

Number Thirty-Two-The Fuel Economizer

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S the price of coal steadily advances, the engineer strives to make steam machinery more economical. Added to the cost of the coal itself is the expense of handling and storing, an item of no little importance in a large city. Until recent years, the use of steam received far more attention than its generation. Improved valve gear, condensers, superheating, triple expansion, and jackets enable the engineer to get the maximum power for a given weight of steam; but these devices have now been so perfected that further economy in this direction will be had only with great effort.

If, now, we turn to the generation of steam, we find a more promising field. Large volumes of hot gases pour out of the chimneys of power houses, and when one realizes that they are at a temperature of 400° to 600° F., some idea may be had of the amount of heat thus wasted. With chimney or natural draft, some of this loss is really desirable, for draft is necessary, and natural draft depends upon the difference in temperature between the gases in the chimney and the air outside. With mechanical draft, whether forced or induced, this condition is not necessary, for the apparatus maintains the draft intensity regardless of the difference in temperature. A great saving may be effected by preventing the esof this heat; in fact, its utilization cape by means of an economizer will save from 10 to 20 per cent.

The Economizer

This apparatus consists of numerous vertical pipes so connected into headers that water may be continuously pumped

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through them, while the hot gases from the furnaces pass among and between.

There are two distinct types: in one, the pipes are arranged in straight rows; while in the other they are so placed that the pipes of one section are opposite the spaces of the adjacent section, this "staggered" arrangement effectively breaking up the flow of gases so that paths and give up a large portion of their heat. they impinge on the pipes standing in their

The economizer is placed between the furnaces and the chimney, so that the gases may be made to pass through it before entering the chimney. This is shown in the sketch on the blackboard. It is customary to arrange a by-pass to conduct the gases directly to the chimney in case the economizer is being cleaned or repaired.

In passing around the pipes, the gases deposit large quantities of soot on the surfaces, thereby rendering the pipes almost useless. To make the economizer a commercial success, the pipes are kept clean by means of scrapers which move slowly up and down, the sharp edges scraping off the accumulation of soot. The mechanism for moving the scrapers is actuated by a belt from a pulley.

Uses for the Heat

Transferring to water a large portion of the heat units in the gases, provides large quantities of hot water, which may be used according to the needs of the factory. It may be the means of heating the buildings, thereby saving steam, which, in turn, saves fuel. Or it may be used for boiling, washing, or dyeing in textile mills. Furthermore, it may be desirable to use it for feeding the boilers. In a boiler plant the hot water reduces the coal bill, for with cold feed-water considerable fuel is necessary to heat the

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water to the temperature at which it is converted into steam. It also reduces strains and insures more perfect combustion, for the boiler plates are maintained at a constant high temperature.

One may ask, why not use a longer boiler, or a larger one, and extract the heat in this way rather than install an economizer? It is evident that the temperature of the gases cannot be greatly reduced in the boiler, for they must be at a temperature much higher than that of the steam, else no steam will form. But in the economizer the water is heated, not converted into steam, therefore the gases may be at a lower temperature than the steam and yet be effective.

In power plants running under a variable road, as in street-railway work or electric lighting, the economizer acts as an accumulator. During the hours of light load, the banked fires slowly heat tons of water, which, being ready to enter

the boilers at the time of increase of load, enable the steam generators to work up to peak load with the expenditure of little extra fuel. The great storage capacity of the economizer will in many plants supply the boilers for nearly an hour.

The economizer is a feed-water heater; but, unlike the usual type of feed-water heater, flue gases are used instead of steam which may be available for other purposes. It uses heat that otherwise is lost. It is customary to install about four square feet of economizer heating surface per boiler horse-power. The increase in temperature of the feed water depends upon the size of the economizer, but is often about 150° F. With a feedwater heater, and an economizer, the boilers may be supplied with water at over 300°; thus the boiler simply converts the water into steam.

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