Coal Age : devoted to the operating, technical and business problems of the coal-mining industry, Vol. 25, No. 22

X££-ffiS2S!!?!S£S Devotcd “>the *"d B“ s E. ™,,.

E. J. Me h r e n, Vice-President P ro b lem s o f th e C o al-M in in g I n d u str y Engineering Editor

Volum e 25 N E W YORK, M AY 29, 1924 N um ber 22

W hen the W rench Feli

A

W ith all its exaggeration, this story is illustrative o f a division o f labor such as makes every man dependent on his co-worker in an extrem ely intim ate manner.

Not all division of labor works in ju st that way. The prop cutter, for instance, cuts h is tim ber in the w inter and delivers the props for use in the summer. He hauls h is load when the snow affords good sledding.

He cuts and sleds h is product when he has nothing else to do. I f he takes a week’s holiday the m ine is not delayed. It may take six months to realize the effect of the delay and perhaps no inconvenience w ill be ex- perienced even then.

Sim ilarly, the roadman may be off a few days, w ith- out direct effect on the m ine operation. B ut m ost o f the men are so im m ediately dependent on other men’s labors th at an idle man is a source of inefficiency throughout th e plant. If the machinę cutter fa ils to cut, several loaders are idle, the motorman gets few er cars to haul, the dumper less cars to dump, the picking- table man less coal to clean, the trim m er less railroad coal to load and trim , and efficiency is destroyed. In conseąuence, the company may find th e cost of coal greafly increased.

Some adjustm ents may be made, but they are effected on the spur of the moment, and any arrangem ent made thus speedily usually is both unsatisfactory in opera­

tion and slow in execution. Storage of coal may help, but only in a degree, and in m ost cases no storage is provided. U ncertainty, discouragem ent and inefficiency destroy all morale. A man who does a poor day’s work becomes indifferent and sets h is g a it to su it th e lower output and becomes a relatively unproductive unit even when conditions favor m aximum output.

T his argum ent m igh t be used to advocate the steady reporting fo r duty of every man employed whose health and home conditions perm it, and undoubtedly much depends on the reliab ility o f the workman. P resent conditions favor such respon sibility. B ut to em phasize that consideration is not th e purpose of this editorial.

Eąually im portant is it th at the cu ttin g machinę shall cut its anticipated ąuota of coal, th at the shot shall be su ccessfu l and bring down the appropriate ton- nage, th at the roof shall not be allowed to fali and close a room, th at th e locom otive shall puli all the coal as soon as loaded, and th at the tipple shall alw ays be ready for effective operation, to m ention only a fe w of the links in the chain of production.

R eliability in machines is one of the keys to steady and profitable operation and no m ine can succeed th at has any uncertainty in the operation of its eąuipment.

Much mine d isability never finds its way to reports of the U. S. Geological Survey but does find place, not yearly or weekly but daily and hourly, in cost sheets.

Consequently, machines should be kept in p erfect or­

der, i f anything in the world can be labeled perfect.

To assure this, mere repair w ill not serve. The repair- man should be set to work at inspection. He m ust know that the mechanical eąuipm ent is always in good condi- tion so that slow work and shutdowns m ay be avoided and every man may do what is expected of him. That is why inspection is displacing repair and th e trouble finder is being superseded by the man who forestalls trouble by prompt inspection and early adjustm ent.

Graham B right, at the Cincinnati convention, said that steel and electric railw ay men spent tw ice as much on inspection as on repair, for in th at w ay the m ost important item in economical operation is assured.

J. F. MacWilliams states th at inspection has lightened the work of the repairman and the machinę shop. H is repairmen were being detailed to inspection duties. No one safely can neglect th is morał. M ost men are busy correcting what greater wisdom and intelligence would have foreseen and forestalled.

Is It Absurd?

D

A side from all in terest in th is undertaking engen- dered by the difficulties encountered and th e m eans taken to surm ount them, th is pipę line m ay ą u ite pos- sibly hołd a valuable su g gestion for the coal industry.

It has long been considered com m ercially fea sib le to coke coal in byproduct ovens only at or near centers of population or in the im m ediate proxim ity of ind u strial plants th at fu rn ish a ready m arket fo r the gas evolved.

May not large h igh-pressure tran sm ission lines solve the difficulties, heretofore considered at lea st form idable if not even insurm ountable, and perm it coal to be coked in byproduct ovens at th e m ine m outh, the gas to be sold in some d istant center of population, coke to be marketed as a high-grade dom estic fuel, w h ile th e other byproducts which run a long gam ut of u sefu ln ess be sold at prices w hich w ill largely d efray the cost o f the m in ing and coking processes?

Take the coal fields of Southern Illin ois as an exam ple.

These lie w ith in about 100 m iles of St. L ouis and less than 300 m iles as the crow flies from Chicago. Burned raw the coals of th is region, except when fired in fu r- naces th a t are specially constructed, are unusually smoky. A lthough the sm okeless com bustion of th ese

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coals is entirely possible, the furnaces employed are practicable only to the industrial user. The domestic consumer, on the other hand, who m ust content him self w ith the ordinary stove or house furnace cannot obviate the em ission o f smoke when burning these high- volatile fuels.

In view of the construction of such pipę lines as th at now b eing built in the Southland, is it any violent stretch o f th e im agination, any absurd flight of fancy, to picture Chicago w ithin a com paratively short tim e as a smokeless city, even though it has long been famed as the sm okiest locality in the country w ith the possible exeeption of Pittsburgh.

The advantages of byproduct coke as a dom estic fuel have only recently become known to the average user.

Already, however, coke has become a som ewhat form id- able rival for anthracite and other so-called smokeless dom estic fuels. Gas, on the other hand, has long been considered as a m ost convenient fuel for stationary heatin g appliances. M anufacturing both of these prod- ucts from a natural m ateriał at best but ill adapted to p erfect combustion, and sim ultaneously releasing a vast variety of useful byproducts ranging all the way from drugs to fertilizers and motor fuel, may at no remote date react not only to the financial advantage of the coal producer, but to the generał benefit and conven- ience of the entire country.

G uiding the P u b lic’s Choice

I

The anthracite operators found th at the public wanted too much large coal. So much indeed that the companies could not sell th eir fine sizes. The operators tried w ith some success to give the public w hat it wanted. They elim inated much needless degradation. They put in chutes that could be kept continuously fuli. They intro- duced conveyors and spiral troughs. They arranged in transporting coal to bed lumps on finer coal so as to reduce breakage. They removed the preferable sizes and fine sizes when crushing the larger so that no coal o f salable dim ensions should be passed through the rolls.

U nfortunately, they still had too much fine coal, and then there were the m ountains of undersize coal th at had accumulated in the earlier years when no one could burn an yth in g but coarse sizes.

Conseąuently, do w hat they would, they could not sell the fine sizes in sufficient volume. Did they fili the valleys w ith th eir fru itless lam entations? For a while, it m ust be confessed th at is ju st what they did. A t last, finding that th eir regrets were vain, they decided none too soon to educate the public to use fine coal.

R ealizing that those u sin g anthracite for steam pur- poses were headed uncompromisingly, and w ith some show of justification, toward bitum inous coal and oil, they sought to convert the dom estic consumer.

They combined th eir efforts and started economy shows. L ittle m ay have been done to cause people to dispense w ith eąuipm ent already in use, but this, at least, has been accom plished: When new houses are built, or when new furnaces are installed in place o f old and worn out eąuipm ent, many persons successfully have been induced to put in arrangem ents for burning

finer sizes. J u st how much has been accom plishe rem ains to be seen, but evidence points to th e attem pt being successful.

Let the Illinois operators take the hint. T hey may succeed in advancing the day when steam plants and locomotives, even dom estic furnaces, will be eąuipped for burning smali sizes and one of th eir difficulties w ill be at an end. Why do th ey not com bine to speed th a t happy day? Why leave it to salesm en who see only the easier way and sell w hat the consumer is ready to buy, leaving the operator’s problems unsolved? M eanwhile every effort should be made to reduce degradation from the face to the railroad car.

Closing Down Mines

W

It seems som etim es th at operators are disposed to believe that a mine thus shut down w ill be greatly in- jured. B ut it is well to remember th at the m ine will never contain more than a certain ąu antity o f w ater.

By ceasing to pump, a back pressure w ill be placed on the water which w ill probably reach a certain h eig h t and then cease to rise. The w ater pressure w ill attain a balance, after which no more w ater w ill come in. Con­

seąuently the operator who pumps during a shutdown n;ay pump more than the operator who leaves h is pump­

ing till resumption.

As for the mine itself it will be preserved rather than destroyed by fiooding. It is remarkable how m ines, flooded th irty or forty years ago, retain th e condition in which they were left. F alls are few partly because the timber is preserved and partly because th e w a ter keeps the condition of the roof, as to m oisture, con stan t; it does not become alternately w et and dry. The pressure of the water helps to su stain the drawslate. The m ine is watersealed and deterioration ceases.

The only disadvantages are th at reopening is slow, that the copper will be restru n g w ith difficulty and may be injured in w ithdraw ing, and there is an expense iń w ithdraw ing raił, copper and other eąuipm ent. A com ­ pany which thus proclaims its e lf out o f th e m arket for an extended period may make its creditors nervous. It may be at a disadvantage in d efend ing som e action in court, for the creditors may be able to im press some judge or ju ry th at such an action is prejudicial to th eir interests. B ut on the whole the total abandonm ent o f a mine is not so harm ful as it is generally feared and not as costly as a steady run of pum ping and v en tilatin g.

Care m ust be taken in reopening as gas m ay collect under pressure, and if it cannot escape by the return as the w aters are lowered, it may spread into th e intake w ith unfortunate results. The air in th ese pockets may be so mixed w ith carbon dioxide and nitrogen as to be unflammable but if it escapes into the air of th e ven ti- lated portion the carbon dioxide and n itrogen m ay be­

come so diluted by good air th at the firedamp w ill be­

come flammable and an explosion result from an open lamp or an electric spark. H owever, precautions can be taken a ga in st such an untoward event.

Early Coal Strip ping Fuli of Heartbreak—I

T he Art Was “ B o r n ” at D anville, 111., Where H and Work Began in 1866 Followed by the “ Land D redge,” Dragline, Shovel-C onveyor and Other Strange and Wondrous Things

By Grant Holmes D a n y ille , 111.

I

“born” in Danville, so to speak, and m ost of the develop- m ents th at have led from

the hand shovel to the 300- tonner have taken place righ t in D anville territory.

I f you^ mind has any pictorial tendencies you can see th e first coal strip ­ ping o f h istory— a man shoveling a little rotten coal from an exposed and weathered bed into a wagon. A s the coal seam was followed back into the hillside the job of rem oving the earth from it grew too heavy fo r th e man. So he made a horse do th e work w ith a slip scraper. Then came th e wheeled scraper for heavier operations.

A t about th is stage, coal

stripping started in the Danville region in 1866. Kirk- land, Blankeney & Graves opened a little pit on Grapę Creek. Then followed a few years of slow expansion in the business. Michael Kelley, in 1875 w as the next outstanding stripper. He began in H ungry Hollow and in th e n ext decade w as the principal operator o f the region, w ith both strip p its and underground operations.

When a man opened a team -and-scraper stripping, he expected to lose money in the sum m ertim e and make it back in th e w inter, as th e surface could be stripped only when th e ground w as not frożen. The truth of the m atter is, m any lost m oney and few got it back.

The usual method o f exposing the coal w as in long p its; first an oblong section along one edge of the field was plowed up, and then th e scrapers took off the loose dirt. The piece w as plowed again. Thus by alternate plow ing and scraping, the bed finally w as reached; the overburden b eing piled in a long mound overlooking the pit. Team s and w agons hauled out the coal during the w inter, and th e n ext sum m er a new błock parallel to that ju st taken out, w as stripped, the w aste being dumped into th e abandoned cut.

Considering th e enorm ous ąuantity of m ateriał to be removed from an acre of coal under 10 to 15 ft. o f over- burden, smali wonder w as it th at men cam e to th e con- clusion th at team -and-scraper strip p in g had no com- mercial value. N everth eless, it is o f in terest th a t th is method is still in use, though only fo r local coal.

A nother firm engaged in th is p rim itive method of strip p in g w as th a t o f J. N. H odges and A. J. Arm ii,

who in 1876 and 1877 loaded a lot o f coal near P itts- burg, Kansas. Mr. H odges had been engaged in rail- road-track laying and ballasting in Ohio, during the two years previous, and had used a steam shovel in th is track work for loading gravel. A fter a short experience in coal-stripping w ith team s and scrapers Mr. Hodges

and his partner decided th at the steam shovel could do the work fa r better.

In 1877, an Ohio con- tractin g company rented th ese two men an Otis steam s h o v e 1. U nfor- tunately there are no pictures or description of th is machinę available— the first machinę on record at least in the bitum inous-coal stripping business. How- ever, w e know th a t Mr.

Otis invented the steam shovel in 1839, and was killed in try in g to operate the first one made.

Concerning th e work of th is pioneer machinę, Mr.

H odges says — “We oper- ated th is shovel for about one year very successfully when I sold m y in terest to engage in other business, but the shovel w as operated for about three years when it was returned to the owners. We had land w ith from 8 ft. to 12 ft. overburden.

“This, w ith good m anagem ent, could be handled profitably, but coal at th is depth w as lim ited and the boom of th is shovel w as too short to do deeper work and w aste the overburden fa r enough away to uncover a p it of coal o f sufficient w idth to be handled econom- ically.” H e also says th a t th is experience proved to him th at a larger shovel would be successful, b ut the m anufacturers told him th at it w as not practical to build such a shovel.

The second strip p in g outfit w hich has come to my notice w as m erely a fu rtheran ce of Mr. H odges’ idea.

The Consolidated Coal Co. o f St. Louis, Mo., exten sive land owners, had a strip-coal area w hich lay in a river bottom, known as M issionfield, near Danville, 111. Here, th e overburden ran up to 35 ft., but in m any places, w as only 10 ft. to 15 ft. deep. The bed o f coal w as 6 ft.

thick. Contrast th is w ith the lig h tly buried seam stripped in K ansas by H odges and A rm ii! However, the seam th ey stripped w as only 3 ft. thick.

The first reąuirem ent to produce coal in th e M ission ­ field w as to find some one w ith sufficient nerve to attem pt strip p in g by contract. W righ t & W allace of L aF ayette, Ind., drainage contractors and dredgers, w ere induced to accept an “ironclad” agreem ent to uncover a given ąuantity o f coal daily fo r th e Consoli- iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii

T H IS IS A N E Y E -W IT N E S S H IS T O R Y

S

H a lf a century o f it su ccessiv ely as m echanic, boss, operator, ad visor to and reseuer o f failing strip com panies, and finally as an in vestor and director in m an y stripping com panies in Illinois, Indiana, K en tu ck y, Ohio and P en n sy lva n ia h ave given him a background in stripping such as few m en have. P rob ab ly no one is as w ell ąualified as he to te ll th e story o f coal stripping from its beginnings. So th is is his story, alth ough he credits his old-tim e friend and fellow -stripper, th e late A lec Swanberg, w ith m uch o f th e inspiration for it.

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dated Co., under the supervision of J. L. Swanberg and th eir m in in g engineer, Louis Stockett.

A s H odges and Armii had found, steam shovels had not been developed to a size suitable for stripping econom- ically, for there had been no cali for shovels larger than those for railroad excavations, but because dipper dredges were called upon to dig in deep water, they had been developed for longer d iggin g ranges. B eing experienced dredgemen, W right & Wallace relied on the size of the dredge to carry out th is contract for strip ­ ping, and in 1885 they purchased from the Marion Steam Shovel Co. of Marion, Ohio, a dredge m inus the hull.

Put Dredge on Wheels and Strip w ith It

The owners erected th is machinę on a wood fram e supported by wheels, and a dry-land dredge or stripping machinę was the result. Wood was the construction materiał used throughout in th is excavator, even on the boom which was 50 ft. long. A single-cylinder, vertical steam engine furnished power to hoist the 3-yd.

dipper and to sw ing the boom. Speed and power as measured today were not virtues w ith th is machinę, as one smali engine took care of all operations.

Four hundred cubic yards of overburden moved in a day w as a great record. One should remember in con- nection w ith th is “astounding” feat, th at those were the good old days when m ine labor worked ten hours for

$1.50. There was no means o f propelling th is dredge except by błock and tack le; hence, m oving the outfit was a slow process, especially on curves, as all w heels were fastened rigidly to the frame.

Because th eir shovel could d ig forward only, a cir- cular path o f operation w as adopted by W right &

Wallace, as the only m eans o f keeping the machinę con- stantly at work. The whole plan of operation resembled

a fiat coil spring— each cut decreased the diam etei o the island o f unstripped coal around which the machinę worked. A t one point in each revolution of the field, the shovel left, as best it could, a gap in the w a ste banks for the haulage way.

The initial circle, or thorough-cut, surrounded about th irty acres, which w as one-third o f the en tire field.

Many m onths w ere occupied in m aking th is and each succeeding circle, for, although the circum ference grew smaller, the curves became sharper, and proportionately hard to turn. When the circles became smali, jacks were used to skid th e land dredge around th e sharp corners.

The w idest cut the shovel w as able to make in th is overburden w as only about 20 ft. Lim ited dum ping rangę prevented placing the w astebanks fa r enough away to keep the dirt from covering up the fa ce of the coal, and because o f th is burial o f the face, entry cu ttin g w as necessary before the m in ers could load out the coal, all of which w as removed from each cut as fa s t as the strippers uncovered it. One can readily see that if a long tim e w as occupied by the dredge shovel in com pleting each circle, th e face o f th e coal around the

“island” would be exposed to th e w eather th e same length o f tim e, resu ltin g in a heavy percentage of rusty, rotten coal in the output.

The slow ness o f th is shovel, the narrow ness o f the cut, and th e annual flooding of th e field by the neigh- boring river, induced th e strip p in g contractors to place a second shovel in th e m ine in order to keep th eir agreem ent w ith the Consolidated Coal Co. A generał enlargem ent o f the first design, includ ing a li- y d . dipper, characterized th is second m achinę. N aturally, its plan o f operation w as the same. A short tim e later, a third strip p in g m achinę w as purchased, h av in g a l ł yd. dipper, a 65-ft. boom and tw o vertical steam

The Great Dry-Land Dredge, the Precursor but Hardly the Progenitor of the Modern Stripping Shovel T hou gh th is m&chinc w s s tłi6 s6cond put into op6ra.tion by W rip ht & W&lla,c6 c o n tr3.ctors in thG M issionflpM of ■p*_ ^ ...

it was the same type as the flrst which started work in 1885. It h?d a 50-ft. boom and a ił-yd dipper boih onertud '

?nTiT<?i?ń?u.rfrClm V VeTt1^ i = S^ n '^ / i e Kg l^ i ' cumbersome machinę rode on wheels fastened r ig id ly m?; błock and tackle and could cut only in a wide circular path which determined the method of stripping. It took months to make one cut around a 30-acre tract.

Butler Bros.’

1890 Dragline

M a c h in e s o f t h is ty p e , o r i g i n a l l y d e - v e lo p e d f o r t r e n c h - in g i n K a n s a s , w o r k e d i n p a ir s f r o m th e e d g e o f th e c u t. O n e u n c o v e re d th e c o a l a n d th e o th e r lo a d e d i t in t o r a il r o a d c a r s r u n d i r e c t l y i n t o th e p it . T h is l a t t e r w a s th e f i r s t m e c h a n ic a l c o n tr iv a n c e f o r l o a d i n g : s tr ip p e d c o a l. T h e s t r i p p i n g d r a g lin e s m a d e p a r a lle l c u ts a b o u t 2 0 - ft. w id e i n th e c o a l a n d o f a n y le n g th .

engines. B oth the strip p in g and coal ends of the busi­

ness had now assum ed quite respectable proportions w ith the three dredges operating.

In about three years, however, a snag w as struck which seemed to lead on to the many failures that occurred in a fter years. The coal m iners struck in 1888, sh u ttin g down the producing part of the opera- tions.

N o arrangem ents had been madę in the contract between the strippers and th e coal company to take care of such a contingency, therefore, W right & Wallace continued to operate th eir m achines during th e strike.

The m ine owners w ere powerless to stop them, and in time, affairs reached such a stage that each shovel had madę a complete circle in its respective working. Start- ing on th e n ext cut, the m achines began to cover up the coal stripped on th e preceding round. To stop the ruin- ous work, the coal company had to buy the dredges and the contract from th e strippers.

The strik ers and th e coal men at last settled th eir difficulties, and work w as again resumed. For two years the new owners operated th e three machines, but at th e end o f th at tim e th ey w ere greatly discouraged as no m oney had been made ow ing to heavy expense and the slow rate o f stripping. Hard work had almost worn out the m achines, w hich w ere not made to stand such strenuous d iggin g, and about 1890, a fter m any fru itless efforts at repairing, th e dredges were abandoned.

Butler Bros. Install Dragline Excavator

In K ansas and M issouri, w here gravel is scarce, but gumbo, a kind o f stiff clay is plentiful, a process called ballast burning had developed. A trench about 8 ft.

deep, 100 ft. w ide and a ąuarter of a m ile long, w as dug in the mud bed. In th is, alternate vertical layers of coal and clay w ere built and the coal w as burned. thus baking th e clay. B utler Bros., E nglishm en, had drag- lines fo r doing the d itch in g in th is process. They burned ballast fo r the Rock Island R.R.

The Consolidated Coal Co., having heard o f th ese dragline m achines and th eir excellent work, started an investigation to determ ine th e adaptability o f the drag­

line to stripping. This inąuiry ended by B utler Bros.

accepting the contract to complete th e job o f stripping the Consolidated poperty at Missionfield.

The year 1890 marked a new era in the stripping industry. Butler Bros.— H enry A. and W illiam—

started work in M issionfield w ith three draglines.

Each machinę w as o f different bucket capacity, I yd., 5 yd. and 1 yd. respectively.

Horizontal Boom Was About 80 Ft. Long

These drag or scraper buckets were sim ply steel boxes w ith an open end which had teeth on the bottom edge.

A cable, traveling through a sheave wheel on th e top of the drag, w as an adjustable trolley which not only raised or lowered th e bucket, but also provided a guide for its travel. Ropes fastened to each end governed the forward and reverse m otions. A fourth cable w as a means to trip a latch which let th e drag sw ing, open and down, to dump its load. These various cables were strung through a horizontal boom, some 80 ft. long.

W ire ropes suspended from a vertical fram e or gantry held the lower boom in position. Two upright boilers supplied power for a tw o-cylinder engine geared to three drums. Clutches controlled the starting, stopping and speed o f th ese drums, each o f which governed a bucket cable. G earing from the en gine to the truck axles gave th e m achinę self-propulsion in either direction.

Instead o f being down in the pit, the drag line worked on top o f a bank from one edge, th e horizontal boom extending over th e cut. W hen th e engineer w ished to dig, he either let th e bucket run out h a lf th e len gth of th e boom, on th e incline form ed by h o istin g th e trolley rope high in the air, or he pulled it out by m eans o f the reversin g cable. R eleasin g the trolley, he then

“dropped” th e bucket into th e pit.

The bucket w as dragged up th e side o f th e bank on w hich th e m achinę stood, until fuli o f m ateriał. Pick- ing up th e load w ith th e trolley, and lettin g it travel to the end o f the boom, th e en gineer tripped th e latch.

T his allowed the bucket to be dumped. N ow, w ith the exception o f pulling the drag h a lf w ay back, the opera- tion w as ready to be repeated. The accuracy and speed

Loading Strip-Pit Coal

T h e B u t l e r B r o s . d r a g lin e w a s th e f i r s t m e c h a n ic a l c o n tr iv a n e e f o r lo a d ­ in g ' s t r ip p e d c o a l.

A l i th e d r a g lin e s , w h e t h e r f o r c o a l o r o v e r b u r d e n , o p e r - e r a te d b u c k e ts lik e t h e o n e in t h e i l l u s - t r a t i o n o n c a b le s f r o m 8 0 - ft. b o o m s . T h e s c r a p e r b u c k ­ e ts f o r r e m o v in g o v e r b u r d e n o r l o a d ­ i n g c o a l w e r e s im - p l y s te e l b o x e s w i t h a n o p e n e n d w h ic h h a d te e th o n th e l o w e r e d g e . T h e c a p a c itie s o f th e s e b o x e s v a r ie d f r o m

% y d . t o 1 y d . B y t h e i r a id s k ille d o p - e r a t o r s w o u ld lo a d c o a l i n t o c a r s a t th e r a t e o f th r e e b u c k e ts p e r m in u t ę .

attained by an experienced engineer w as truły remark- able— three complete operations a m inutę w as not unusual.

As the boom did not sw ing, the whole machinę had to be moved freąuently to keep the “scraper” supplied w ith d iggin g materiał. This reąuired much track laying of an expensive naturę, because the so ft ground let the machinę sink down unless ties were laid as closely together as possible.

Dragline operations laid the coal open in rectangular cuts about 20 ft. wide and a ąuarter of a mile long. The length of the boom enabled the w aste bank to be built far enough away from the coal face to prevent its burial. E ntry driving was therefore unnecessary, the m iners loading the coal from the “open face.” When the end of the cut w as reached, the machinę was shifted back about 20 ft. from the edge of the bank.

It then dug back to the opposite end of the pit, laying open a new strip of coal and depositing the spoił in the cut from which the coal had ju st been ąuarried. “D rag- lin in g” transform ed the field into a series of parallel ridges.

The B utlers’ machines were first placed at work in the upper bottom of Missionfield, where W right &

Wallace had also operated. The stripping w as shallow in the center o f th is “bottom,” and the overburden con- tained no hard m ateriał such as shale or soapstone, con- seąuently the dragline operated w ith such ease and speed th at the Consolidated Coal Co. soon w as enjoying an output o f over 1,000 tons of coal a day.

The available strip p in g in this section o f the field did not last long, as a large part of th e coal had been mined while W right & W allace were at work. Increased depth of overburden, the unlooked-for appearance o f hard, blue shale above the coal, and a bad flood, forced Butler Bros. to move two o f th eir excavators into what is known as lower Missionfield. The third machinę was abandoned.

The overburden in the eastern end of th is field was ligh t, therefore, the dragline fairly made the dirt fly from about 40 acres o f coal. Here, the machines were

operated in tandem — one stripping, th e other loading coal into the railroad gondola cars w hich ran directly into the pit. This w as the first m achinę coal m ining.

However, in the center o f the field, shale, soapstone and increased depth o f overburden w ere encountered, retarding the progress of th e m achinę greatly, and it became necessary to drill and b last the hard m ateriał so that the bucket could d ig it. The profits decreased correspondingly, as B utler B ros.’ contract w ith the coal company w as to deliver th e coal on board cars, at a certain price per ton. The m ine w orkers becam e dis- satisfied, and struck for an eig h t hour day and heavy increase in w ages. These troubles stopped b usiness, and brought about the abandonment o f th e first drag- lines.

Cement Gun Used fo r R ock D u stin g M ines

R

The dust cloud at th is point w as dense 25 m in utes a fter the cement gun w as started, and definite evidence of dust settlem ent w as found as fa r as 9,000 ft. from the gun.

When the air current th at p asses through th e entry being dusted is uniform , the ąu an tity o f deposited d ust is necessarily g re a test near the point w here th e d ust is ejected. To obtain even d istrib u tion o f dust through an entry, it would be necessary to sh ift th e d u stin g machinę from tim e to tim e. In an en try such as th a t described, o f 98 są .ft. cross section and 6,000 ft. long, to obtain a deposit of, say, 4 lb. per linear foot, at th e rate of 1 ton (o f 2,000 lb.) an hour, th e m echanical dis- tributor would have to operate for 12 hours.— B ulletin 225, Bureau o f M ines.

Further Progress Made with Voice Transmission From Underground Workings to Surface

Are Wireless Tests V a lu a b le W hen T hey Are M ade B e t w e e n t h e M ine and High- Powered Stations on the Surface ?

P r o p a g a t i o n Affected by Earth Strata and Sheet W a ter— E x p e r i- m ents carried on from M ine Loco- m otive Successful

Recewing and Sending from Locomotive B^y J. J. J^akosky

U . S. B u r e a u o f M in e s

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less com munication have been conducted in - Illinois, Pennsylvania, Arizona, Utah, Idaho, Colorado, M ichigan, W yoming, Kentucky, N ew York, Connecticut, and in England, Germany, Italy and France. A s a result, occasional press notices and illus- trations have appeared in many papers. This may lead to the im pression th at radio communication in m ines and tunnels is an established fact and th at the method is com paratively simple. A s a m atter of fact, th is is not so.

In practically all th ese tests the generał procedure has been to take underground a receiving set o f vary- ing degrees o f sen sitiv ity and listen to broadcast m usie or speeches from high-power broadcasting stations.

The results o f th ese experim ents are of real value and much in terestin g inform ation is b eing obtained.

R eceiying station s have been placed on train s and Com­

m unications received w hile th ey w ere p assin g through tunnels, tubes under rivers or subways. Other tests have been conducted in the Grand Canyon of the Colo­

rado, in subm erged subm arines, in w ater wells and caissons, in the new tubes under the Hudson River, etc.

T ests have been made in every conceivable part o f a m ining plant, from th e carpeted offices of the officials to the m ule barns underground.

Tests Determ ine Tr a nsm issio n Factors

T hese te sts are o f much in terest and are usefu l when interpreted w ith reference to the conditions under w hich they are made, as fo r instance, in relation to th e surface and sh eet w aters, th e geology, m ineralogy, and topog- raphy of th e m easures, the presence o f m etallic con- ductors, such as electric pow er and lig h tin g circuits, compressed air and w ater piping, trolley w ires, tele- phone lines, h o istin g cables, headfram es, etc.

P ractically all th ese tests, however, have three com-

No t e—Headpiece shows set connected to harp on trolley pole.

Line-radio communication may be carried on while the locomotive is in operation. Very little interference resulted from sparking of the trolley wheel. All tube sockets were mounted on special cushions to minimize vibration.

mon factors. F irst, reception is from broadcasting stations of a power very much greater than practical for underground sending sets, However, even one-way communication, th at is, from the high-powered station on the surface to a receiving set in the mine* would be of value if the entombed m iners who survive could be eąuipped w ith reliable receiving apparatus to allow them to tune in to some nearby station. The entombed men could be inform ed of the progress of the rescue par- ties and th at inform ation, though it afforded no physi- cal aid, m ight prove to be a favorable psychological factor. In some cases even entombed men m igh t be directed to parts of the m ine w here they could be reached by rescue parties.

N o Successful Min e-to-Surface Tests

Second, in m ost of th e te sts com ing to th e attention of the U. S. Bureau o f M ines, there is no m ention o f successful transm ission from w ith in th e m ine to the surface. T his transm ission is o f th e g rea test impor- tance. I f a reliable m eans o f voice transferen ce can be placed at the disposal o f entombed men, th ey could inform rescue parties o f th eir exact location, th e num- ber of men entombed and livin g, th eir nam es and d esig- nation number, and the condition o f the a ir supply.

Such inform ation would greatly fa c ilita te rescue oper- ations.

Thirdly, in practically all te sts conducted eith er by the Bureau o f M ines or outside experim enters, the data obtained indicates th a t m etallic conductors such as trol­

ley w ires, power and lig h tin g circuits, car rails, com- pressed-air and w ater piping, h oistin g cables, steel fram e work, etc., are the controlling fa ctors in under­

ground com m unication. An early publication of the Bureau called atten tion to th e influence of such con­

ductors upon radio transm ission , and later work has greatly em phasized th e im portance of th is featu re.

M ost experim enters have neglected to consider the ef- fe cts o f such m etallic conductors or “carriers” for the high-frequency currents. In some tests, however, the apparatus, w hen moved to other locations w ith in the

m ine w here such conductors did not exist, gave en- tirely different results.

In practically every deep underground m ine te s t it has been noted th at reception is much b etter in one place than in another. When th e apparatus is moved from one part o f a room, into an adjacent w orking or to another entry on the sam e level, b etter sign als may be received. In other cases a fter th e change no radio com m unication can be received.

I f th e radio w aves actually penetrated the earth for any appreciable distance, it does not seem probable th at m oving the apparatus a few fe e t would make such a great difference in the result. The effects of line-

present, its sheet distribution, and, to a som ew hat less extent, on the type of ore or m inerał.

Some form ations, such as coal, shale, etc., are in- sulators when dry. The m etals recovered from ores may be excellent conductors but such ores as th ey ex ist in the earth are not n ecessarily so. T his is due to the fa ct that the m etallic particles, if e x istin g as such, are separated by the m atrix which as a rule is a non- conductor. In m ost ores the m etals do not e x ist as such but as chemical compounds, which m u st later be extracted by hydrom etallurgical or pyrom etallurgical processes.

Coal, which often contains as much as 95 per cent

Portable Mine Apparatus This receiving set was connected to two short sections of mine raił and picked up signals from a line-radio transmitting s e t connected to the rails in another section of the mine.

Oftentimes, g o o d results can be ob- tained by connect- ing the receiving set to the raił and driving a peg in the ground.

radio or so-called “wired w ireless” should be considered by experim enters when conducting such tests.

I do not intend to convey the im pression th at pure radio is th e only system o f com m unication. On the contrary, any reliable portable system o f voice com­

m unication w ill be satisfactory . The point to be em- phasized, however, in connection w ith such tests is that if line-radio played an im portant part in carrying the sig n a ls in or out o f th e m ine when te sts are conducted and w hile th e m ine is in good w orking order— and all trolley w ires, power and lig h tin g circuits, etc., are in- sulated from th e ground and w ith no breaks in such m etallic conductors— can the same system of com muni­

cation be relied upon in cases of d isaster? Fire, falls of rock and roof, explosions, m ine flooding, etc., will not only ground the electrical circuits but also break the conductors in m any places, cau sin g changes in the electrical ch aracteristics o f th e m etallic carriers, which m u st all be taken into account.

So far, practically all data obtained from te sts con­

ducted by th e Bureau indicate th at th e absorption o f radio w aves in p en etratin g the earth depends m ainly upon th e relative conductivity o f the strata through w hich th e w aves are propagated. The conductivity of th e earth depends largely upon th e ąu antity o f w ater

of carbon, is usually an excellent insulator. P ractically none o f the carbon in coal is ex iste n t in th e green state but is present as a com plex bitum inous or pitch-like materiał, which acts as an insulator. M ost o f th e east- ern coals are of such close structure as to contain little free w ater or m oisture. The “com bined” w ater does not add to the electrical conductivity. M any seam s, both horizontal and vertical, contain sh eet w aters and seep- ages between strata which prevent tran sm ission o f s ig ­ nals for any considerable distance. Other m inerals such as hem atite and certain sulphide ores are conductors even when dry.

In all cases, however, th e con d uctivity o f beds o f ores and m inerals is g reatly increased by the presence of water. Mine w aters con tain in g relatively large quan- tities o f dissolved sa lts are good electrolytes. Radio waves are greatly attenuated in p en etratin g such waters, and in horizontal, uniform strata w ith num erous sheet w aters, only a sh ort penetration o f the radio waves may be expected. The th ick ness and num ber of such sheet-w ater form ation s lim it the p en etratin g power of the radio signals.

Sim ilar effects have been noted in num erous govern- ment tests conducted on subm arine sig n a llin g . I t has been found th a t even th e com paratively high-pow ered

transm itting station s aboard battleships can not be re- lied upon for continuous communication w ith subma- rines when they have submerged to a depth approaching that of the average shallow coal mine in this country.

In m ine tests conducted when receiving from surface station s, it has been found that the signal strength is not greatly affected at a short distance underground, but drops off rapidly as soon as a depth is reached approxim ating th at of seepages and the sheet-w ater for- m ations. T his holds true, of course, when there are no m etallic conductors present to act as carriers. In mines having electric lig h t and power circuits, such conductors

tained indicated th at the rangę is dependent almost entirely upon the type o f conductors present, th eir elec- trical constants, etc. The tran sm ittin g rangę o f th is set in the average coal mine is only a fe w hundred fe et when there are no conductors present, but m ay be sev- eral thousand fe et when operating in the vicin ity of power and lig h tin g circuits, telephone lines or other metallic carriers.

In another series of tests sim ilar effects were noted when u sin g a loop aerial for transm ission. It is not necessary that the m etallic conductor be tuned or have a natural period the same as th at o f the wave. The

Bureau’s Experimental

Laboratory This station has

been licensed to use any wave length and power. From here the experi- menters were kept in touch with all the portable field stations as they were moved about in the mine. Both code and v o i c e transmitting equip- ment was used.

w ill carry the signals down from th e surface— and often w ith but slig h t dim inution in inten sity.

The exten t to which such conductors act as carriers fo r the high-frequency waves depends upon th eir elec- trical ch aracteristics and the wave freąuency. If the electrical circuits offer high resistances to th e high- freąuency currents, there will, of course, be a great loss in signal stren gth. However, the capacities o f machinę w indings, parallel w irin g, etc., are often o f sufficient m agnitude to offer a relatively Iow reactance bypass or shunt fo r the h igh freąuencies.

In a series of recent te sts a 10-w att telephone tran s­

m ittin g set w as mounted upon an electric locomotive, and the outfit connected to the harp of th e locomotive trolley pole. A portable receivin g set, con sistin g o f a detector and tw o steps of audio-frequency, w as used on the su rface and connected to a 50-ft. single-w ire antenna. The m ine w as operated by a sh a ft about 400 ft. deep. There w as no difficulty in picking up s ig ­ nals from the underground m oving locom otive station as long as th e receivin g antenna w as placed in the v icin ity o f any electrical conductor extending into the mine. The sig n a ls w ere picked up readily when the receiving antenna w as near the trolley w ires, power and lig h tin g circuits, telephone lines, and h oistin g cables, th e relative m agnitude of th e sign als from the different carriers being in the order named.

In a series o f te sts conducted to determ ine th e tr a n s­

m ission ran gę underground, a portable 10-w att trans- m itter w as mounted on a storage-b attery locom otive.

A short th ree-w ire antenna mounted on the top of the locom otive w as used fo r tra n sm ittin g. The data ob-

wave is propagated or guided by such conductors which function “apęriodically.”

The effects of line-radio are particularly noticeable when u sing a loop antenna for reception. In alm ost every case w here the receiver is placed at a sufficient distance underground to be shielded, it has been found that the loop antenna, when near m etallic carriers, func- tions b est when placed in more than one direction regardless o f the true direction of th e tra n sm ittin g station. M oving the set to another location in the vicin ity often results in the loop p oin tin g in a different direction. A study o f near-by conductors show s th e reasons fo r such changes in the directional properties o f the loop. W hen u sin g a capacity-type antenna, such as a w ire stretched along the m ine entry, th is loss of directional properties as a rule cannot be noticed.

The variation in electrical ch aracteristics o f under­

ground m ine-power d istrib u tin g system s ind icates th a t certain optimum freąu en cies e x ist fo r each m ine. The higher the freąuency used th e more efficient th e radia- tion and the less loss in signal stren gth, when carrying across gaps due to m etallic breaks, etc., in the con­

ductors. On the other hand, the atten uation o f th e high freąu en cies when tra velin g along m etallic conduc­

tors or directly through the earth is much g reater than for the longer w ave-lengths. The optim um freąu en cy to be used in each case w ill depend upon th e electrical constants of the underground m etallic conductors, dis- tances to be covered and typ e o f com m unication desired.

I t would, of course, be adm irable i f adeąuate provi- sion could be made for th e placing of m ine com m unica­

tion rescue sets underground and have them ready for

T esting with Loop A erial P r a c t i c a l l y al l

metallic conductors have a tendency to warp the signals and destroy the di- rectional properties of the loop. This portable set was used in many places in the mine to study the effects of water, pipes, rails and mine cars.

use in cases of em ergency. However, the capital in- vested in idle eąuipm ent w hile w a itin g for som ething to happen offers a serious obstacle— especially as the real u sefu lness o f the apparatus for rescue operations has not y et been determined.

A direct service for the apparatus m ust be found in the everyday operation o f a mine. Because radio can operate effectively and efficiently when the radiated en- ergy can be guided by m etallic conductors, it may be p ossible to use a sim ple low-power portable line-radio set. The installation of a line-radio telephone set is simple, it being necessary only to lay a w ire 25 to 50 ft.

long on the ground or stretch it along the wali or roof and in a direction approxim ately parallel to carriers, or to couple the set directly to such conductors by the use o f suitable capacities or inductances. A s fa r as actual in stallation of apparatus is concerned, th e line- radio is sim pler and can be installed in shorter tim e than th e p resent underground m ine telephone w ith its connecting w ires.

The line-radio apparatus itself, however, is more com- plicated than th e present sim ple m ine telephone. A fter th e line-radio apparatus has been developed to the point w here its use for m ine com m unication can be safely recommended, its finał adoption w ill depend upon the op eratin g conditions p revailing in each m ine. The line- radio apparatus alone w ill necessarily have a h igh er up- keep and m aintenance expense, but to offset th is will be, not only the alm ost total elim ination of telephone line and w ire m aintenance, but also one less w ire to be given space in the m ine haulagew ays and entries T his holds tru e o f course when th e line-radio u tilizes power or lig h tin g circuits already in place.

I t has been found th at practically any conductor in- sulated sufficiently for the economic transm ission of power or lig h tin g current w ill act efficiently as a carrier fo r th e h ig h freąuency current. The conductor acts in a double capacity, the high-frequency current being superim posed upon th e low -frequency or direct-current pow er w ith o u t any interference to the power supply and w ith only slig h t in terference to the carrier-current com m unication i f proper coupling and filtering system s are used. N o in terferen ce to telephone circu its is noted

by superim posing the high-frequency carrier on th e tle- phone line. Much recent experim ental and commercial work on line-radio and carrier-current Communications has established its fe a sib ility .

I f the apparatus can be made sufficiently practicable to be used as a m ine com m unication apparatus, it w ill prove advantageous for the follow in g r e a so n s :

(1) Men would soon become acąuainted w ith th e oper­

ation and care o f th e apparatus. In case of a d isaster such knowledge would be of fa r more value than any short course or tra in in g w hich m ig h t be given men for the operation o f other rescue apparatus.

(2 ) M aintenance and inspection service w ill be jus- tified for other reasons besides the purely hum anitarian viewpoint of safety.

(3 ) Purchase o f sets, m aintenance and apparatus costs can be charged to operating rather than to safety

— and there is alw ays more m oney available fo r the former.

(4 ) Breaks in the m etallic conductors do not com- pletely stop com m unication, as w ith a break in the lines connecting the present m ine telephones. Short breaks in the carriers such as opening o f sw itches, etc., are not as a rule directly noticeable in operation. Severe disasters which m igh t cause one or more breaks w ill not com pletely destroy th e conductors, and com m unica­

tion could probably be established despite them .

A Little Volume on Min e Ven tila tio n.— T o Thomas Bryson, a m in in g en gin eer and certificated col- liery m anager o f th e M ining College o f W igan, England, the industry is indebted for a book entitled “Theory and Practice of Mine V en tila tion .” It is a thoroughly practical publication and is especially stro n g on the subject o f m ine fan s. The public is accustom ed to books which lay em phasis on d istribu tion o f a ir; th is book lays th e rig h t stress on th e ventilator. I t trea ts of main fan s and boosters but does not fa il to deal w ith the basie principles o f air d istribu tion and m easure- ment. The book m easures 4 f x 7 ł in., has 255 pp. and is distributed in the U nited S ta tes by Longm ans, Green

& Co., 55 F ifth Ave., N ew York City, th e price being $3.