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Largest Electric Light in the World line dye of the desired color has been

What is the largest size electric light made ? dissolved. Aniline dyes of any color de--B. E. L.

sired may be obtained at a drug store. There is an electric light in the light

Be careful not to cover the base of the house on St. Catherine's Point in the

lamp with this solution. Isle of Wight, supposed to be the largest in the world. It is run by two dynamos, and if both work in conjunction the con

Demagnetizer centrated light is computed to be equal Question: I-wish to make a watch demagto 6.000.000 candle-power. The carbons netizer for use with alternating current. Will have a diameter of 212 inches, which is

you kindly publish the formula in the next

month's issue of your magazine. I want two, about seven times the size of the carbons one to work on from 75 to 90 volts, and the in the ordinary street arc lights. The other to work on 110 olts.-C. R. induction arrangement of each machine.

Answer: No formula is required for consists of 60 permanent magnets, each magnet being made of 8 steel plates.

making a watch demagnetizer. Make a The armature is 272 feet in diameter, and

wooden core of rectangular form, upon composed of 5 rings with 24 bobbins in

which to wind the coil. The core should

taper slightly so that it can be withdrawn each.

when the coil is wound, leaving an open

ing to receive the watch. The coil should Third Rail Electric Railway System be about 3 inches long, and should be

What are the advantages of the third rail wound to a depth of 1/2 inch with No. 28 system of electric traction ?--D. S. B.

B. & S. wire. The same coil can be used on either 75- or 110-volt circuits.

If it takes too much current and heats O O

up, reduce the current by putting a lamp in series.

Case-Hardening What is case-hardening and how is it done? -A. L. R.

The essential difference between maTHIRD RAIL ELECTRIC SHOE.

chine steel and tool steel is the amount

of carbon that they contain. If carWhere heavy trains are to be moved, bon be added to machine steel it will the third rail system offers a cheaper be turned into tool steel. Sometimes method of transmitting the large cur- articles are wanted very hard on the surrent strength necessary to their oper- face to resist wear and at the same time ation. The shoes offer facilities for very tough to withstand shocks. If the conveying a heavy current to the motors, piece be made of tool steel in order to be because of the large area of contact. On hard enough, it will be too brittle, and if a trolley system, the trolley wheel is de- made of machine steel in order to be stroyed very rapidly because of sparking, tough enough, will be too soft. To overcaused by the small area of contact be- come this difficulty the parts are made tween the wheel and wire. The cost of of machine steel and then the outside is maintenance is small in a third rail sys- carbonized or converted into tool steel tem and it is much more convenient, in to a slight depth, and this outside coating operation, not to have a trolley pole to of tool steel then hardened. The process watch,

is known as case-hardening. The method used generally consists of heating the

machine steel red hot in contact with To Color Incandescent Globes

something very rich in carbon, generally How can I color incandescent lamp globes ?

ground bone. The surface of the maDip the lamps in, or paint them with, chine steel takes up or absorbs the cara solution of collodion, in which an ani- bon and is converted into tool steel.

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Grinding the World's Coffee

By C. Smith

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LECTRICALLY operated
E labor-saving devices are at

present utilized to a very
great extent in the roasting
of coffee in all modern fac-

tories, the absolute cleanliness, the speed of operation and the thoroughness with which electric power does its work, all combining to make it of especial value in such installations.

Arabia, Java and Venezuela furnish a fair proportion of our coffee, but the greater part probably comes from Brazil, being imported in bags weighing 132 pounds. This is our ordinary green coffee, which is ready for roasting, if sufficiently clean. There may, however, te considerable manipulation required to prepare the green coffee for the roasters, the thorough cleaning being termed "milling," this process also making the coffee roast brighter.

The raw coffee is conveyed from a feed bin or bucket elevator, to the milling and

cleaning machine, entering a shaker-feed, which distributes it uniformly over a sieve, consisting of two sections, the first section of which sifts out the fine material and carries it to a bucket by means of a pipe, while the second section, which has larger holes, allows only the coffee to drop through and pass on, the sticks, strings, etc., being carried to another pan. The coffee which passes through the second sieve then enters the milling machine proper, which consists of revolving cylinders, between which the coffee is thoroughly scoured and brushed, the surface of the bean being smoothed and freed from all dirt and then discharged through a pipe.

An exhaust fan, placed above the machine, causes an air current through it, so that all the light waste material from the coffee is drawn up through the feed pipe and through an inclined pipe leading from the discharge hopper, slide dampers being utilized to regulate the

force of the air current, which is made just as for grain, with bins constructed sufficiently strong to lift everything but of galvanized iron. sound coffee beans, so that chaff, dust, The coffee is now ready for the most blighted beans, etc., go up the pipes. The important operation, namely, roasting, machines are operated by electric motors, and is transferred to the machines by varying in capacity from two horse power bucket elevators. The correct roasting of to five horse power, and have an output, good coffee is a delicate operation and in the latter case, of from thirty to forty depends upon the machinery only in part, bags per hour. Apparatus of this type skilled operators being essential. The also admits of adjustment and regula- coffee is carefully watched until, in the tion, both as to the separations made and judgment of the operator, the roasting the degree of milling to which the cof- has proceeded just far enough, the color fee is subjected.

of the bean indicating when this point The next important operation is sep- has been reached. The roasters, howarating or grading the coffee, that is, ever, provide that at any period of the sorting the beans into grades of uniform operation every bean is precisely like size and shape, and removing the round every other bean. "peaberry" as a separate grade. Coffee O ne of the accompanying illustrations of uniform beans always commands a shows a battery of eight roasters in operbetter price, although this has nothing ation in a modern factory. The roasters to do with its drinking qualities. Form- are built up in brick. erly a great deal of "polishing" or color- As soon as the roasting has proceeded ing of the green coffee was performed, far enough in the opinion of the operabut, at present, there is very little of this tor, the coffee is immediately discharged done since the coffee sells on its roasting into the cooler boxes, which are quickly value and not on its appearance in the wheeled to a cooler pipe, connected with green state. A separator is used for this an exhaust fan, the air of the room being work and consists of sieves for accurate- thus drawn through the coffee while, at ly grading the green coffee, a peaberry the same time, spading is resorted to, to apron being sometimes used, in addi- further facilitate the cooling. This proction, for the perfect separation of round ess has to be accomplished very quickly, beans.

as the coffee would otherwise become At the present time they are not used darker and darker in color, and finally as much as formerly, since the sieve sep- take fire, causing a loss of several hunarators now used give improved results. dred dollars worth of beans. The cooler In those factories, however, which are boxes, one of which is seen in the illusmost particular about separating the pea- tration, are arranged to tip on their berry perfectly, the aprons are still in use, trucks so as to discharge the coffee, after the coffee fed to them being the peaberry cooling, and are, in consequence, called grades produced by the sieves.

"tiptop” cooler boxes. The green coffee is now mixed in con- The principle in cooling is simply to siderable quantities, ten, twenty, or thirty spread the hot coffee out in a thin layer bags at a time, this being simply a whole- on top of a sheet of perforated metal so sale blending operation so as to avoid the as to quickly cool the beans by passing necessity of weighing out the right pro

air through them by means of a fan. portion for each batch as it is roasted. Formerly, the outlet of the fan blower Some manufacturers, however, hold that

was connected with the enclosed space

underneath the perforated metal sheet of each grade should be roasted separately and afterward blended. Shovelling was

the cooler box, but, inasmuch as there

was no outlet out of doors, the hot air formerly resorted to in this process, but,

rose to the top of the room. In modern at present, mixers driven by electric mo

practice an exhaust fan is utilized, the tors are used for this purpose and are

inlet being connected with the bottom much more thorough and economical in part of the cooler and the air from the their operation.

room being drawn down through the cofIn handling the green coffee bucket, fee and carried out of doors through a elevators and conveyors are employed pipe.

From the hopper into which the coffee vator would cause too much breakage is dumped from the cooler, it is conveyed and the beans are handled by gravity to a revolving screen which separates only as far as possible. In the stoning fine material, then to a pipe up which operation, the coffee is lifted up to the there is a light current of air which re- highest point of the factory by air sucmoves all chaff, hulls, etc., loosened from tion and from the stoner-hopper or rethe coffee during roasting and effects a ceiver into which it lands, is spouted to great improvement in its appearance. The a finisher, a mill, or to storage bins. beans then pass into another pipe, up In large concerns, the coffee is next which the air current is strong enough to sorted, so as to make a handsome, large carry sound beans, leaving all heavy ma- bean grade, leaving the small pieces to be

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terial such as stones and nails at the bot- used for grinding. As mentioned betom of the “stoner boot." Stoning is im- fore, some manufacturers prefer to mix portant to render the subsequent grind- their coffee after roasting, and in such ing operation safe for the mill, since cases the operation of blending is perstones get into the coffee either by care- formed at this stage. The glazing makes less gathering of berries dropped on the dull coffee look bright and seals the beans ground or by being put in, deliberately, so that they do not lose their aroma. to add weight. It might be thought that The finisher is merely a stout wooden all stones would be sifted out from the drum with cast iron heads and with doors green coffee by the separating machines in the side for filling and emptying. It This is true of those stones which are is run almost full of coffee, the finishing either larger or smaller than the beans, material being mostly water, the princibut the sieves fail to remove those which pal effect being produced by the friction are of the same size. In roasting, how- of the coffee on itself. ever, the beans become lighter and larger, In the regular glazing process, the cofincreasing the difference in specific grav- fee is mixed with a liquid, so as to spread ity between them and these stones and, it completely over every bean and then when the coffee is placed in the stoner this is baked on by a hot blast of air. pipe, the beans are in consequence car- The coffee is now ready for packing, ried up by the air current, leaving the although sometimes certain of the latter heavier stones behind.

operations are omitted. The second ilThe handling of the coffee, after roast- lustration shows a complete coffee roasting, is a very different matter from hand- ing plant, with the green coffee machinling the green coffee, since it is now easi- ery on the right. The capacity of this ly broken. For this reason a bucket-ele- plant is 200 bags per day.

Government Runs Cement Mill

By Guy E. Mitchell

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HE Interior Department construction in the West, large amounts has been exercising, for of cement are necessary, and in the case a branch of the govern- of the great Roosevelt dam in the Salt ment, an unusual amount River Valley in Arizona, the specificaof business sense, if not tions called for 200,000 barrels. It is downright spunk, in learned from the daily newspapers that dealing, not only with there is a cement trust, and it is further other branches of the gathered that this trust expected to coin

government, but with a million or so out of the cement contract private individuals. The Secretary of which it alone, it assumed, was competent the Interior is charged with the carry- to fill. Last winter the government ading out of the irrigation law and now vertised for bids, and the price proposed has at his disposal over twenty-five mil- by the trust was $9 a barrel. The raillions of dollars for this purpose. He road rates were very heavy, the distance seems determined to employ business to be transported was great and the ceprinciples in this work, without much ment people controlled the situation, so regard to red tape methods or the pro- they thought. By examination of one of tests and howls of private corporations the early reports of Arthur P. Davis, the expecting to secure large profits out of projector of this great Salt River irrigathis work.

tion project and now assistant chief enIn most of the big projects of dam gineer of the Reclamation Service, the

[graphic]

THE GOVERNMENT CEMENT GRINDER AT THE ROOSEVELT DAM, ARIZONA

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