Coal Age : devoted to the operating, technical and business problems of the coal-mining industry, Vol. 25, No. 7

McGr a w- Hil l Co m p a n y, In c. Devoted to the Operating, Technical and Business

Ja m e s H . McGr a w, P restd en t R. Da w s o n Ha l l

E. J . Me h r e n, V ice-President Problems of the Coal-Mining Industry Engineering E ditor

Yolume 25 N EW YORK, FEBR U A R Y 14, 1914 Number 7

For a N ew Era in S afety

S

Unfortunately, th e effect of com pensation has not been as great as m igh t have been expected. Several ways of obtai.ning greater sa fety still are being overlooked, and it seems now, a fter several years of accident compensa­

tion, that the laws m ust be strengthened.

In many sections of the country have been found operators ready to co-operate in a revision of the laws ,having that end in view. A. J. Moorshead tried through the American M ining Congress to have such revision put into practice, but h is effort seem s long ago to have spent its force.

The Rocky M ountain coal operators are actively ad- vocating b etter legislation and the Rocky M ountain Coal Mining In stitu te is even now canvassing w ays of achieving greater sa fe ty in the dry areas of the W est.

This effort o f the operating men w ill surely meet with the approbation o f all the m ining fraternity.

Some tim e back some of the w estern Pennsylvania operators sought to elim inate the menace of mixed lights by dem anding th at all m ines having areas operated by sa fe ty lamps be operated entirely w ith such lamps. They w ere not successful, however, in procuring sufficient support to make th eir legislative plans suc­

cessful.

An effort should be made to g et sa fety m easures re- ąuired in one state adopted in all others where condi- tions are sim ilar. Much cred it should be given to those concerns which, like the Old Ben Coal Corporation, have adopted safeguards ou td istancin g those provided ;in mines confronted w ith sim ilar sa fety problems. In the long run such precautions are not only salutary but profitable, especially when taken to prevent such acci­

dents as may involve a whole m ine in a common catas- trophe.

A New U se o f T rad e A sso cia tio n s

A

ment of Justice m igh t be around. We m ust be eąually careful and shall avoid g iv in g any sta tistic s of mine explosions caused by coal dust, for fear some one m igh t make an improper use o f them .

A brick, we are told, is a construction m ateriał of use in masonry, but it has been used to com mit murder.

Statistics resemble th at brick and i f someone used it improperly, the D epartm ent of Ju stice m ight ask who it was that sm uggled in th e brick and we could be con- victed of being the g u ilty party. Someone m igh t say, for instance, th at m ine explosions w ere so m any and the cost is so high that th e price--- but th at is enough.

Before we w rite more we m ust ask the subscription de- partment if Secretary Daugherty or any of h is hench- men are reading Coal A g e.

Avoiding bricks, whether in hand or in flight, we wish to suggest a new use o f trade associations. Could not some such body erect for its members a mili, cen- trally located, yet fa r enough from the m ines to avoid having a scalę made for it by the United Mine Work- ers, where rock could be ground for the use of members and others in the rock dustin g o f m ines? Of course unless it was intrastate it would not be allowed to ascertain the cost of the installation, the cost of grind- ing the rock, the ąuantity ground or distributed, th e percentage of its product th at would go through any given screen, but nevertheless it m igh t be well to install it i f it could be done w ithout the aid of sta tistic s and if it rendered no accounts to its members. A t least, we believe it m ight be perm itted to ex ist fo r a w hile till the Departm ent of Justice tried once again to legislate the action into one of crim inal intent.

Such a mili could do much to make m ines sa fe in the area it served. The su ggestion has been made to Coal A g e ; it surely is w orthy of consideration— if legał, o f course.

Can’t W in w ith P o o r Cards

N

Coal operators in flush tim es overextend them selves.

They load th eir financial structure w ith m ines and lands until it fairly groans under th e strain . They do not put enough of th eir profits back into th e plants th ey have, but sąuander th eir m oney in plants th ey desire to add to their holdings. A s a result w hen the close m argin comes they are taken en tirely by surprise.

I f they had loading m achines and shortw all cu tters, good tracks and sw itches, pipes and screens w hich did not have to be perpetually renewed, autom atic sub- stations, reclosing circuit breakers, pumps and doors—

to m ention a few item s— th ey could clip off th e few cents that would keep them out of th e market, and, being in the market, th ey would be able to run steadily and clip off some more cents.

A viciou s cycle in h ig h cost perpetually drives th e operator fu rth er and fu rth er to th e wali. W hen the cost is high, the price o f coal m u st be h igh, and being high m ust be made a little h igher because th e m in es cannot run steadily. W hen fo r th is reason th e p rice

231

232 CO A L A G E Vol. 25, No. 7 is raised a little higher, then the minę runs still morę

irregularly, and the price m ust be raised again. Just a little advantage—two cents on the steady-run basis may make a difference of ten or more tim es that much because of its effect on steadiness and intensity of run.

Times of Iow prices cali for high courage combined with circumspection. A little diligent figuring, how- ever, will show ju st where a man can be relieved here, there and the other place to engage at other and more profitable work for the company.

There are in this world but two cycles, the cycle of success and the cycle of failure. A little profit makes efficient operation and steady business and spells suc­

cess. A little loss of money and of faith results in an excessive economy and that again in inefficient, irregu- lar, ill-sustained operation and bankruptcy. A trifling difference in cost oftentim es separates the two. Low cost sets the cycle of success in operation. H igh cost brings in operation the vicious cycle of failure.

Give T liem a B oost

Y

Manning, Cottrell and Bain have each in their turn tried to do their work fearlessly and constructively.

M istakes of judgm ent may have been made but not of heart. They have deserved a more outspoken note of approval. Their effort to keep safety before the indus­

try should be given wholehearted support. Their ad- vocacy of rock dust should bear more effective fruit.

Their investigations of sa fety appliances should meet w ith greater interest and what they have recommended and devised should have speedier acceptance.

They are the friends of the industry and no one can conceive any instrum entality better suited than the U. S. Bureau of Mines for the obtaining of th at greatest o f needs for the reform ation of the industry— cleaner coal.

A concern in Buenos Aires purchased its coal for some tw enty years from a company of standing in the United States. In the course o f those years the mine became exhausted, and the A rgentine firm was notified by the American company o f that fact. “We have,” said the United States company, “other coal which m ight suit you.” The Argentine firm tried it and did not like it as well. Its officials, accordingly, said: “There are lots of m ines in the United S tates; let us try some of them .” They did so, and got in the hands of the sharks th at seem more active in the export field than perhaps in the domestic. A s a result these Buenos Aires buyers said th ey would never try again to buy in this country.

They purchased coal from Europę and told an American

commercial attache th a t never till the U nited States would guarantee coal ąuality would they again be in the m arket for coal from th is c o u n try ’s mines.

Shall we never learn th at adeąuate inspection has been, and ever w ill be, the sh eet anchor of successful trade?

Better In sp ectio n a l F o rces

R

„ mines of the United S tates make it essential to improve the inspectional service. A t present we have no adeąuate safety organization. In each state we have only chief inspectors and subalterns. The latter have a hard life traveling through the m ines and being al- ways away from home. Their salaries are smali.

Though their tenure o f office is reasonably secure and in most cases not threatened by p olitics, th ey have no hope of promotion. Increased com fort, decreased exer- tion with advancing years, g row in g public appreciation are denied them. Such conditions do not provide the best men. The inspectional service is a blind alley.

In Great Britain, on the other hand, th ere are grades of inspectors. The upper classes of the service are' spared the drudgeries of generał inspection. When a problem is presented th ey act to settle it, and being more competent than the generał run o f th e inspectorate and living on a higher piane of social recognition they are able to approach those who w ish to contravene their authority or stretch the law by some tech n icality with a degree of confidence and und erstan din g th a t makes their representations respected. I t is difficult for a

$4,000 or $5,000 man to make th e $25,000 or $50,000 president of a large company realize th at he m ust con- form to some practice which s a fe ty prescribes or the law reąuires.

Furthermore, our inspectors in generał have not re- ceived technical training. They have experience ob- tained in actual contact w ith m in in g problems. They have studied enough to obtain a certificate but most of them know little enough about electricity and almost nothing about the other form s o f s a fe ty th at would throw light on safety at m ines. T hey are rarely traveled men. They know th eir d istrict well and th ey know perhaps more than th eir d istrict knows but there is no incentive to acquire more. T hey are sa fe to continue to be inspectors w ithout th is fu rth er instruction. The safety services of the coal m ines are b etter than we have any right to expect under p resent conditions, but why not take the steps th at will make them still better?

Mr. Le w i s’ i d e a of the proper place for the wage scalę negotiations, concurred in by a fe w operators, was an unfortunate one from m any standpoints. The choice of Jacksonville, Fla., fo r the Feb. 11 conference t°p easily g ives the im pression th at operators and miners are entering the forthcom ing parley in a play- ful, vacation mood. The argum ent th a t the negotia­

tions ought to be removed as fa r as possible from the interfering influences o f the coal states is thin soup.

If the sessions should be drawn out at great length the unpleasant im pression o f the conference would be intensified over th e country. H ence it w ill be good policy for both sides to knuckle down to business at once upon their arrival in sunny Florida and do the one logical th ing w ithout delay— extend the present wage agreement.

February 14, 1924 C O A L A G E 233

Three Methods o f Preparation >

And Two o f Shipment Embodied In Design o f Indiana Tipple

One Grizzly and Tw o Shaking Screens U sed—F ive Sizes M ay B e Shipped by Truck, Eleven Sizes by R aił— Large Concrete Storage B ins F acilitate Local Shipments and R elieve Car Shortage

A

Three methods o f preparing coal are provided in th is plant. The first is the preparation of run-of-m ine over a li- in . bar screen, m aking standard H -in . lump and li- in . screenings. T his product can be made w ithout operation of any mechanical screen ing equipment and is intended to sa tisfy th at portion o f the trade that has become accustomed to th is kind o f coal, having used it for years, and which th erefore still demands it.

Al l La r g e Co a l Lo a d e d Ov e r Bo o m s

Passing the coal over a horizontal screen, w here it can be picked, and then loading it into cars on fo u r tracks form s the second m ethod of coal p rep aratio n . The th ree la rg e r sizes a re loaded over loading booms.

Screening in th is m ann er to g eth e r w ith provision fo r picking and fo r loading into cars by m eans of booms

Excellent facilities for w agon shipm ent are provided at few mines. The headpiece show s how the Clinton Coal Co. has made provision for local delivery. TTie concrete bins here shown span not only one railroad track but a paved wagon space as well.

Shipment of any size may thus be made by either car or truck.

is all that is necessary in order to obtain the b est domestic preparation.

The third system o f handling coal at th is plant con- sists of delivering the run-of-m ine from the w eigh hopper in the tipple direct to an elevator, by w hich it is raised and then screened over a horizontal screen into five sizes, each of w hich is deposited in a separate concrete bin. The sizes made are designated as screen­

ings, pea, nut, eg g and lump coal. The bins are quite wide and each is fitted w ith tw o openings, or gates, in the bottom. One of th ese g ates delivers to cars on the screenings track under the tipple. Thus all coal pre- pared in th is manner can be shipped by raił i f desired.

On the other side o f the bins the coal is loaded directly into wagons. A m echanical rescreen is inserted in the wagon chutes, w hich results in an extrem ely h igh - grade coal being available to the tow n of Clinton, located at a distance o f a m ile and a half from th is m ine.

The space below th e b in s is provided w ith a concrete floor or pavement. T his is extended so as to make con- nection w ith a concrete road leading to Clinton, The capacity of th e bins is such as to provide fo r a large wagon and truck b usiness. It also serves fo r coal storage frequently reliev in g the situ a tio n w hen there is a car shortage and th ese sizes are b ein g shipped.

Fr o m Ca g e Co a l Ma y Ta k e Se v e r a l Ro u t e s

A b rief description o f th e method o f h and ling and the mechanical equipm ent follow s: The coal is dis- charged from self-dum ping cages into steel chutes which deliver it to a bottom-door gravity-dum p w eigh hopper serv in g a chute and bar screen. In case bar-

234 C O A L A G E Vol. 25, No. 7

F ig. 1— Side View of Tipple

I n a d d i t i o n t o t h e f o u r s iz e s m a d e o v e r t h e ti p p l e s c r e e n s , tw o s i z e s m a d e b y a b a r s c r e e n , a s w e ll a s r u n - o f - m i n e , m a y a ls o b e s h ip p e d .

screen coal is to be sold the veils covering th is screen are lifted and th e screenings delivered direct to a hopper above the slack track. The 11-in. lump coal flows to a feed er hopper which delivers to an apron loading boom over th e nut-coal track.

In case run-of-m ine is to be loaded the veils over the bar screen are closed and the en tire m ine product is loaded over the boom on the nut track. The recipro- catin g feed er is so adjusted th at it delivers th e coal to the boom quickly, so that an interval is preserved be- tw een dumps from the m ine car. Thus th is boom can be used fo r insp ecting th e contents o f each car for docking purposes.

BYPASS SH U N T S THE COAL TO THE B lN S

When it is desired to send coal to the concrete bins for preparation a door below the bar screen is opened and the run-of-m ine delivered through it to an apron conveyor. T his in turn feeds a gravity discharge elevator which delivers the coal at the top to a hori- zontal screen 5 ft. wide. T his screen is provided w ith

l i - , 2 i - and 4-in. openings. The larger sizes o f coal are picked at intervals along th is screen and the refuse deposited in the rock trough, which delivers it to a smali bin at the end of the storage bins, whence it is hauled away in wagons.

I f it is desired to prepare the coal over the screen in the tipple another door in the chute is opened. This deflects the coal to the reciprocating feed er directly below it, which in turn distributes it evenly on a 6-ft.

horizontal screen. T his separates the coal into H -in ., 3-in., 6-in. and lump sizes, thus m aking grades th at are standard in Illinois and Indiana. The larger sizes of coal can be picked on th is screen. The pickings are placed in the refuse trough over the screen and delivered beyond the lump track into a bin from which th ey are hauled away in wagons.

Ro c k Is Re a d il y Se n t to Wa s t e

Another feature o f interest embodied in th is installa- tion is the means employed in handling rock from the mine. Doors are placed in the dump chute above the w eigh hopper. These, when opened, deliver rock to a steel bin at the side o f the tipple. A side-dump car draws rock from th is bin and proceeds up a 10-deg.

incline to the gob pile beyond the railroad tracks. This incline extends directly over the three loading booms and is in the same position that it occupied before the steel tipple was built, its trestle having been incorpora- ted into the new tipple structure.

The provision o f three d istin ct methods fo r prepar- ing the coal is the m ost unusual featu re th is prepara­

tion plant embodies. In a measure it is exceptional also in the excellent facilities th at have been provided for shipping the entire mine output or any portion of it in prepared sizes fo r local consumption.

At this plant the rescreen and storage bins were built by the coal company w hile the eąuipm ent and machinery w as furnished by the Roberts & Schaefer Co., of Chicago. The steel tipple also, including all eąuipment, w as designed and built by th is sam e firm, actual erection being perform ed by R. G. Ławry, contracting engineer.

F I G . 2

Local B ins

T h is p i c t u r e s h o w s t h e c o n c r e t e b i n s e x t e n d i n g a t r i g h t a n g l e s to t h e ti p p l e p r o p e r , in w h ic h a r e s t o r e d fiv e s iz e s o f c o a l t h a t a r e p r e p a r e d o n s c r e e n s a b o v e th e m . F r o m t h e s e b in s t h e c o a l m a y b e d e liv e r e d e i t h e r t o t r u c k s o r w a g o n s l o c a t e d in t h e p a v e d s p a c e b e ­ lo w t h e m o r t o r a i l ­ r o a d c a r s o n t h e s l a c k t r a c k . C o a l f o r l o c a l d e l i v e r y is r e - s c r e e n e d m a k i n g a n e x c e p t i o n a l l y g o o d p r o d u c t .

February 14, 1924 C O A L A G E 235

Building a Long Retarding-Conveyor Gallery at Brotherhood Minę,

Coal Riyer Collieries

Structure R ises 800 F t., Is in Places 40 F t. A bove Ground and 1,400 F t. Long, the M axim um Grade Being 35 D eg.— H ow Joints Are Stiffened and Strengthened

By W. J. De n m a n

A s s i s t a n t E n g in e e r , C o a l R i v e r C o llie r ie s

1

At the Brotherhood m ine of the Coal River Collieries, on the Laurel Fork of B ig Coal River, Boone County, W est V irgin ia, has been built a headhouse and conveyor gallery of som ewhat unusual construction. The new headhouse is located 1,400 ft. away from the railroad and some 800 ft. above it, the coal being conveyed to the

tipple at the railroad by a rope-and-button conveyor (one of the longest, if not actually the longest, ever installed in a single u n it). The maximum slope of the conveyor is 35 deg. The headhouse bents in generał are built of 10xl0-in. tim ber w ith 2x8-in. bracing and w ith all intersections bolted. On the conveyor gallery the bents rangę from 5 to 40 ft. in h eig h t w ith standard 8x8-in. and 10xl0-in. four-post tow er construction hav- ing 2x8-in. level and cross bracings, all intersections being bolted. W ith such a structure we expected to have much expense for upkeep and inspection. The join t bolts would have to be tightened continually, th at being our experience w ith bolted structures.

Use Plates to St ip f e n Tim ber Jo in t s

In order to avoid some of th is uncertainty and ex- pense and to make a structure unusually stiff and safe w e used a new device con sistin g of a cold-rolled steel plate of special com position which is made in square and round form s. The dim ensions of the sąuare plates are l i in., 4 in. and 5 in. The round type has a diam- eter of 3 in. A hole in the center of each plate is made o f ample size to perm it the passage of th e bolt w ith which it is used. The edges of the plate are cut so as to form triangular teeth I in. h igh and about i in.

w ide at the base. T hese teeth are turned alternately up and down so th a t th ey project on both sides o f the plate. They are so designed th at when th e plates are inserted in the tim ber jo in ts th ey relieve th e bolts of m ost of the shear stresses.

In F ig . 2 is shown a view o f one of the tim b er-join t plates, clearly illu stra tin g th e ir construction. These plates can be used in bolted and in other form s of tim ber join ts such as post jo in ts, elim in atin g thereby the n ecessity of a pin and m ortice. Our first use o f them, however, w as in connection w ith bolted work.

They were placed betw een th e m em bers o f a jo in t so th a t the bolts passed through the two m em bers and also through the hole in the center of the plate. The en tire jo in t then w as pulled tig h t, cau sing the teeth to b ite into the wood on both sides o f th e plate.

When w e first considered th ese tim b er-join t plates our main desire w as to obtain a m ore rigid structure w ith a greater factor o f safety . T ests made by the D epartm ent o f Civil E n g in eerin g o f Columbia U n i- v ersity at its te s tin g laboratories showed th e results tabulated in F ig . 3. T hey w ere made on a num ber o f F ig . 1— Rope-an(f-Button Conveyor Gallery

T h is l o n g i t u d i n a l c r o s s - s e c t i o n s h o w s a h a l f s p a n b e t w e e n tw o b e n ts , t h e j o i n t s b e i n g s t i f f e n e d b y s p e c i a l l y d e s i g n e d p l a t e s a n d t h e s p a n s b y a n i n y e r t e d t r u s s .

236 C O A L A G E Vol. 25, No. 7 join ts each made up of 4x5.93-in. yellow-pine timber,

w ith two 2.02x5.93-in. yellow-pine splice plates, three

£xlO-in. bolts, six gx3£x3i-in . w ashers and fou r 4x4x 0.052-in. tim ber-joint plates, the bolt holes being o f 1 in. diam eter and the plates being countersunk in the splice and main members. In the first te st the plates were sąueezed into the tim bers by pressure applied to the top and bottom o f the splice plates by means o f a te stin g m achinę. The other two join ts were simply tigh ten ed by the £-in. bolts. The three join ts were subjected to tension through suitable connections attached to the main and splice tim bers and the relative m ovement of splice plate and main members w as meas- ured w ith an extensom eter.

Wh e n Jo i n t Is We l l Ma d e Ti m b e r Is Sa v e d

Because th ese tests dem onstrated that a join t made up w ith these plates was much stronger than one made up m erely w ith bolts w e w ere able to effect radical savings in the m aterials and labor reąuired for the work.

The illustration in the headpiece shows the conveyor gallery near the foot Of the hill and indicates the type of construction used when the bents reąuired were long. F ig. 1 gives details of the conveyor-gallery bents and indicates how the plates were installed. Four-inch plates were used throughout.

Sim ilar plates w ere used in connection w ith the 2x8-in. bracing in the conveyor gallery, m aking a more rigid job and elim in ating one-half the number of bolts which otherw ise we would have had to use.

Four-inch plates were used where the 10xl0-in . posts of the high tow er bents were lap-spliced, a single,

I n t h e u p p e r r i g h t - h a n d c o r n e r is o n e o f t h e s p e c i a l p l a t e s a n d o n t h e r i g h t a s c a r f j o i n t s t i f t e n e d b y f o u r o f t h e s e d e v ic e s .

Fig. 3— Tensile Test of Timber Joints with Special Shear-Sustaining P lates

T h e c u r v e s o f d e f o r m a t i o n have each an individual baseline

m a r k e d “ O .” P r e s s i n g t h e p l a t e s into the tim ber apparently m a k e s li t t le d if fe r e n c e u n d e r a t e n s i o n o f 11 t o n s but allows seriously g r e a t e r deformation thereafter.

instead of a staggered, line o f bolts b eing used. Despite the reduction in m ateriał and com plexity, g reater stiff- ness and strength was obtained than could have been afforded by joints o f the original design.

Fig. 1 shows the details on the conveyor gallery on the upper part o f the hill. It w ill be noted that tim ber-joint plates have been used in sp licin g 6-in. x 10-in. x 40-ft. built-up beams. These beams w ere built of two lines of 2x l0 -in . oak planks, 18 ft. and 22 ft.

long, respectively, w ith filier splices at th e ends and centers 8 ft. in length. P lates w ere used at th ese splice joints.

To the present our experience has been exceedingly satisfactory and we hope, as is claimed, th a t even where the timber dries out, the rig id ity o f th e jo in t w ill not be impaired. So far, we have not had an opportunity to check up th is in detail, but though the wood has already dried out som ew hat th e jo in ts do not show the slightest tendency to loosen, nor w as th ere any splitting at the bolt holes. On the contrary, the plate seemed rather to prevent th is action from occurring. Periodical inspections, however, are still b eing made.

So far we have used th ese p lates only w here they can be held by the com pression of bolts. In the ap- proach treśtle to our No. 4 tipple we expect to install them on the tops of the caps and under the stringers, elim inating dapping and dow eling and keeping the tim ­ ber faces apart, thus decreasing rot And increasin g the life of the timber.

U sefu l Data o n S torage B atteries For N on -T ech n ical M en

“Elements of Storage B a tteries,” by Jansky and Wood, describes in a elear and sim ple w ay the principles, oper- ation and m aintenance o f storage b a tteries fo r th e non- technical man who is desirous o f g ettin g th e highest efiiciency out of th e b a tteries w hich he uses or super- vises. The underlying principles o f the various types of storage b atteries are explained in considerable de­

tail. An im portant section o f the book is devoted to the proper ch argin g o f the b atteries, togeth er w ith a description of various typ es o f ch argin g eąuipm ent.

The book is published by the M cGraw-Hill Book Co., 370 Seventh Ave., N ew York.

February 14, 1924 C O A L A G E 237

Specially Designed Motors for Larry-Car Service

M echanical D etails Are Such as to Accom m odate H eavie Axles— M ust H ave Armaturę W inding and Gear R atio Suit- able for Slow Speed— M otors F itted with B ali Bearings

By C. A. Atwell M o to r E n g i n e e r i n g D e p a r t m e n t

> W e s t i n g h o u s e E l e c t r i c & M fg . Co.

E

The motors used fo r propelling larry cars should be of the same generał construction as the modern railw ay types o f m otor; th a t is, th ey should be series-wound, com m utating pole m otors o f rugged construction su it- able for m ounting on the car axle and geared to the axle by sin gle reduction gearin g. The featu res th at were mentioned above as common to all larry cars place several special reąuirem ents on the m otors, however, that are not reąuired fo r the usual railw ay m otors.

This makes it n ecessary th at the m otors w hich are entirely suitable fo r use on larry cars be designed especially for th a t service. The principal special re­

ąuirements are:

T h e h e a d p ie c e s h o w s a t y p i c a l m in e l a r r y c a r . T h e u s e o f t h i s c a r is r a p i d l y i n c r e a s i n g , d u e t o t h e l a r g e r c a p a c i t y a n d t h e e a s e o f d u m p in g . T h e a r r a n g e m e n t f o r d u m p i n g u s u a l l y i s m a d e t o n t t h e c o n d i t i o n s f a r b e t t e r t h a n is p o s s ib le w i t h t h e o r d i n a r v m in e c a r .

(1 ) E xtra large axle bearings.

(2 ) Slow-speed w inding.

(3 ) Ball-type arm aturę bearings.

The fact th a t larry cars are built prim arily for car- ryin g heavy loads n ecessita tes a truck d esign u sin g a large axle. This in turn reąuires larger axle bearings than are custom ary for the usual railw ay typ e motor

M u c h d e p e n d s u p o n t h e a x l e d i a m e t e r , D , b e c a u s e i f i t i s in - c r e a s e d t h e g e a r c e n t e r d i s t a n c e , A . i n c r e a s e s a n d C , t h e c l e a r - a n c e u n d e r t h e g e a r c a s e , i n c r e a s e s b e c a u s e o f t h e u s e o f a l a r g e r g e a r . B is t h e c l e a r a n c e u n d e r t h e m o t o r f r a m e .

238 C O A L A G E Vol. 25, No. 7

F ig. 2— Larry-Car Motor

T h is s p e c i a l l y d e s i g n e d m o t o r is r a t e d a t 80 h p . a n d 230 o r 550 v o lts . T h e a x l e b e a r i n g s a r e f o r a n 8 -in . r e a r a x le . B a l i a r m a ­ t u r ę b e a r i n g s p e r m i t h i g h e r m o t o r e fflc ie n c y a n d p r o p e r l u b r ic a - t i o n o f t h e b e a r i n g s w i t h o u t o v e rflo w i n t o t h e m o t o r a n d w in d in g s .

o f the same size such as are used on street railway, interurban, or even fr e ig h t locomotive service. In F ig . 1, the dim ension “A ” represents the “gear center distance.” On standard railw ay motors th is distance usually is made a minim um for the largest size axle th at is likely to be used w ith a certain motor. A minimum distance, “A ,” has the advantage of a maxi- mum clearance, “C,” between the gear case and top o f raił. In order to increase the axle bearing bore,

“D ,” the gear center distance, “A ,” m ust be increased.

A gear w ith more teeth is used to make up for the increase in gear center distance and mesh w ith the motor pinion. The clearance, “C,” is reduced by the sam e amount that “A ” is increased. As it is not neces- sary for “C” to be as large for slow-speed service as on high-speed railw ay service, th is decrease is not detri- mental.

The voltages common about industrial m ateriał yards w here larry cars are used generally fali w ith in the ranges of 230 to 250 volts or 500 to 550 volts. Of th ese voltages the m ost common are 2'30 and 550. A car speed w ithin the lim its of 8 to 12 m iles per hour at the nominał ratin g of the motor usually is desired.

0 2.000 4j000 6P00 &000 IQ000 12000 14,000 16000 18,000 20000 22(100 24000 28X10 2^000 R ated Load in Pounds

F ig. 3— Load Rating of Bali Bearing

I t w ill b e o b s e r v e d f r o m t h i s c u r v e t h a t t h e m a n u f a c t u r e r ’s l o a d r a t i n g d e c r e a s e s w i t h i n c r e a s e i n s p e e d . T h is c u r v e s h o w s t h e e x t r e m e i m p a c t l o a d s t h e b e a r i n g w ill w i t h s t a n d a t s lo w s p e e d s .

Fig. 4— Motor for Narrow Track Gage

T h is m o to r is r a t e d a t 7.5 h p . a n d is m a d e f o r tis e o n l a r r y c a r s o p e r a te d o n 1 8 -in . t r a c k g a g e .

tained from a larry car motor which has a winding designed especially for the voltage and speed reąuired in such slow-moving eąuipment.

Bali armaturę bearings are preferred to the sleeve type on larry-car motors for the same reason as on m ining locomotive motors. They reąuire less lubrica- tion and attention and m aintain the arm aturę in a cen­

tral position w ith respect to th e field poles. Bali bear­

ings usually are lubricated w ith grease w h ile sleeve bearings are lubricated w ith oil, which often results in over-oiling and a conseąuent entrance o f oil insid e the motor, where it dam ages the w in din gs or commutator.

Bali bearings have not been accepted as standard on the higher speed railw ay m otors, but th is is due to the mechanical inability o f the bali bearing to stand up under the conditions of high arm aturę speed and im- pacts received at high car speeds. The average speed of the larry car service is even lower than th a t of the mining locomotive, so the odds are stron gly in favor of the bali type of arm aturę bearings. F ig . 3 shows how the m anufacturer’s ratin g o f a bali bearing in- creases as the speed decreases.

Fig. 2 illu strates an 80-hp. larry-car m otor that pos- sesses the special reąuirem ents m entioned above. The following tabulation shows com parisons o f th is motor with a high-speed 600-volt railw ay m otor th a t has the same size of fram e and same arm aturę and field-pole dimensions.

C O M P A R IS O N O F L A R R Y -C A R M O TO R W IT H H IG H -S P E E D RAILW A Y M O TO R OF T H E SA M E P R IN C IP A L D IM E N S IO N S

Lb. Diam.

of Wheel

W t. of M o to r C om plete w ith G ears

M o to r H p. Volts Amp. R .P .M . M .P .H . T ractiv e

E ffort G ear

R atio (See Fiu. 1)

A B C n

L a rry C a r M o to r... 80 230 550

305

128 390 8 6 3,500 15/67 33 4,470 16.6 4 | 2} 8

H ig h Speed R ailw ay M o to r .. 140 600 202 900 23 2 2,260 16/61 33 4.050 15.4 4J 3 * 6

T y p e of A rm atu rę Bearings

Sleeve

The special yoltage and speed reąuirem ents o f th e larry car service practically prohibit the use of an ex istin g railway motor w inding. It som etim es happens th at a standard high-speed 600-volt railw ay motor, when oper­

ated on 230 or 250 volts, will run at the desired sp eed ; but, due to the fact that the motor is designed for 600-volt service, the ampere capacity o f th e copper conductors in the w indings will not be adeąuate for the lower yoltage. This w ill result in obtaining less horse- power for a given m otor size and w e ig h t than is ob-

February 14, 1924 C O A L A G E 239

P reyen tin g Stray Currents from D eton ating E xplosives

Ground C urrents C ause Prem ature E xplosion — P oten - tial D ifferences R edu ced b y Interconnections and

G rounds— K eep Firing Cable W eil In sulated By E. E. Jones

G

lated and free from splices or broken insulation.

It should be inspected freąuently—at least every day. U sually leakage of stray currents into the blasting circuit are the cause of premature explo- sions because the cable or conductors often span areas or materials having high potential differ­

ences.

J

Some of the men refused to work in the sh a ft unless steam w as used in place of electricity for operating the hoists and pumps. T his was practically out of the ąuestion, sińce the electric eąuipm ent had already been installed. It w as decided, therefore, to make te sts to determine the cause o f the explosion and to decide upon the remedy.

The system we w ere u sing for power was grounded on one side and supplied by a 1,000-kw. rotary converter,

Fig. 1— How the Eąuipm ent and Pipes Were Inter- connected and Grounded

The h eavy lin es sh o w w h ere a so lid 0000 copper con d u ctor w a s connected and gTounded, th u s red u c in g th e p o te n tia l differen ce b e ­ tw een variou s ob jects to a p oin t too Iow to se t off a b la stin g cap.

From Explosives E ng in e er, Septem ber, 1923.

sim ilar to those used in street railw ay system s except that 250 volts were employed instead of 500 to 700, as in street railways. F irst, all the sw itches in the hoist, pump, motor and com pressor circuits were opened to make sure that the trouble w as not caused by a leak from the positive side of the system to any of these machines.

While the sw itches were open, an electric b lastin g cap was connected between a pipę in the air line and

Fig. 2— Elevation View of Shaft Showing Ground Connections

B y th u s effectiv ely g rou n d in g th e sy s te m o f electr ic a p p aratu s, pipę lin es and tow er the conftdence o f th e w orkm ei) w a s regain ed and th e w ork m ade sa fe.

the discharge line from the pumps. The in sta n t a connection w as made, the b lastin g cap detonated. A connection w as then made between the air line and the ground adjacent to th e sh aft. The cap detonated, but not instantly, which showed th at there w as not at all tim es suffieient voltage between th ese points to fire a cap.

N ext, a connection w as made between the m etal of the h oist fram e and th e ground, and th e b lastin g cap fired instantly. F inally, a connection w as made be­

tw een the bottom of the sh a ft and a w et place near the su rface; in a fe w seconds th e cap detonated. From th ese results it w as evident th a t there w as a suffieient difference of potential present in the variou s places selected to fire b lastin g caps connected in an ordinary circuit in the sh a ft.

To eąualize the voltage at variou s points around the surface and at th e bottom o f th e sh aft, the fram es of all the m achines on th e su rface and th e pump at th e bottom of th e sh a ft w ere m etallically interconnected w ith a heavy copper conductor and grounded. The tw o h oists w ere connected by a heavy copper cable which was grounded; th is cable also w as connected to other surface eąuipm ent and to all pipes g oin g down the sh aft. The grounds at the tw o h o ists w ere made by b urying a coil of 0000 copper w ire in a hole 4 in. deep.

Salt w ater w as poured on th e coil to inerease its earth contact. The different connections and grounds are shown in the accom panying diagram s.

240 C O A L A G E Vol. 25, No. 7 A fter th is work was completed $25 was offered to

some o f the m ost intelligent workmen if they could fire an electric blasting cap by connecting it in any way that it would explode, without, o f course, u sing a blast­

ing machinę or the power circuit. None of them was able to fire a cap in th is way. A fter the tests the caps used were fired by connecting into a power line to prove that they were good caps.

T ests were then made with a m ili-voltm eter, w ith which no difference in potential greater than 100 mili- volts could be detected between any two pipes, from any of the pipes to the ground, or from the top of the sh aft to the bottom. When it w as thus dem onstrated that danger from stray currents had been elim inated the confidence of the men was restored.

The follow ing rules were strictly enforced:

(1) Explosives must be in an insulated Container when lowered down the shaft. (2) No more than two men c a n be in the shaft while the shots are being prepared. (3) The muck bucket must not touch the bottom of the shaft during the preparations for a blast. (4) The blasting m a ­ chinę must be in possession o f the top man and can be used only by the men who prepare the shots in the shaft and then only in the presence of the top man. (5) The shooting cable must be inspected daily from top to bottom. I f a bare place is found, the cable m ust be thrown away and a new one obtained.

I consider No. 5 a very im portant rule, because if stray currents should develop, the danger would be greatly reduced if the leading and connecting w ires were all well insulated. I am glad to say th at no one was seriously hurt during the sin k in g o f the sh aft.

New Coal-Cutting M achinę D riyes Gangways

Sam e D e v ic e C uts, B reaks and D elivers P rod u ct—

E ntries M a y B e D r iv en on B o th Sides o f M ain G angw ay

By Ar t h u r Ge r k e W aldenb urg, S ilesia , G erm any

Ą T T E M P T S at driving galleries in a coal seam by 1 m achines date back to the tim e when boring by means of m achines w as begun. Technical periodicals and books of the last decades contain descriptions of machines which were successful only in so far as they were patented. Many were put to test, but w ithout the result hoped for. T hat all these attem pts failed probably is due to the fa ct th at it w as im possible to produce eąuipm ent that could stand the great strain of coal cutting, and to provide a guide th at excluded any deviation from the direction intended.

In sp ite of th ese failures, however, the activity of inventors has not come to a standstill, and numerous appliances have been patented. The solution o f the problem would be o f special importance to the m ining industry, sińce driving galleries means w aste o f money and tim e. The quicker the gallery advances, th e sooner large-scale m in ing m ay begin and the larger will be the number of men at work. As the advantages to be gained are many, a description o f a new coal-cutting machinę, called “R otatia,” is of interest. Some tim e ago th is machinę was introduced in th e German, Czech and H ungarian m in ing industry and proved a complete success.

T his rotating coal-cutting machinę consists of three main parts: (1 ) The driving device; (2 ) a system of tubes for len gth en in g; (3 ) the cu ttin g device, which con sists o f cutters composed of several parts, and the m echanism for vertically cu ttin g or breaking the core, likew ise composed o f several parts.

The d riving device, fixed on a carriage, is secured on an inclined plate at any point from which a gallery is to be driven, w hile th e cu ttin g device is kept in close touch w ith the face o f the coal through the system of len gth en ing tubes, as shown in F ig. 1. The whole system is connected w ith the sh a ft of the driving de- vice by a special coupling. The len gth en ing pieces are tubes w ith flanges and are connected by keys and two locking screws. The cu ttin g device is fitted to the last len gth en in g piece and rests on a column provided w ith

an adjustable bearing, stayed a g a in st the roof or the sides.

A t a suitable distance from th is column a second column, which also may be stayed and arranged in various positions, is provided w ith an adjustable bear­

ing. On the cutting sh a ft behind th is second column is mounted the cu ttin g device, as shown in F ig . 2.

The arms of the cu ttin g device are connected by means of rings which correspond to the diam eter o f th e cut to be made. The cu ttin g device on the cu ttin g shaft has on its front side a crown cu tter for prelim inary boring, which serves as a guide for the cu ttin g device and also makes it easier to cut the core.

The arrangem ent for cu ttin g th e cores is mounted in the cutter arms. On every second arm, ly in g op- posite each other, there are cu tters o f equal size and form, one set for cu ttin g th e outer, the other for cut-

i i

1—Machinę Which Mines C oal

breaks and'loads coal*1 rotary coal cutter which mechanically cuts,

February 14, 1924 C O A L A G E 241

Fig. 2— Cutters Projecting from Two or More Rings Are Driven by a Long Line of Shafting

W h a t w ill puzzle th e A m erican read er w ill be to tell how the coal can b e rem oved w ith a lin e o f sh a ftin g and p o sts flllin g the roadw ay fo r a d ista n ce w h ich in c a se s is sa id to be 230 ft. T his is effected b y th o se rock in g or sw in g in g ch u tes, w h ich , introduced in Germ any, B elg iu m and G reat B ritain , are now flndin g th eir w a y into the m in es o f th e a n th ra c ite region of th e U n ited S ta tes. The sh aft is ex ten d ed a s th e c u tters advan ce, new colu m n s being erected for its support. T h is m u st ca u se som e d ela y in th e oper- ations. T he colu m n s are ad ju sted r ea d ily by a screw w ith ra tch ets.

ting the inner core. These cutters are arranged in a circle which exactly corresponds to the diam eter of the cut to be made. These core cutters are behind the arm s o f the rings holding the cu ttin g tools and are regulated by springs. When the machinę is in operation the driving m echanism is set in motion by compressed air or electric power. The cu ttin g oper­

ation begins as soon as the advance work is completed, and the cu ttin g tools begin to work, m aking one outer and one inner circular cut. I f the coal is very solid, a third narrow cut is made near the center.

A fter about one fo o t of coal has been cut, the ad1 vance work stops and the cu ttin g device continues rotating about its sh a ft w ith ou t advancing. The core is then cut or broken by the operation of a special mechanism on the arm s of the core cutter. This core-

cutting device consists o f parts like sickles w hich are advanced into the coal w ith an up-and-down motion so as to break the outer and the inner core. The broken core falls in lumps of large and smali size and th ese are carried off by means o f a rocking or sw in gin g chute. When the whole of the core is cut, th e advance work again begins to act and th e cycle o f operations repeats. The advance work m ay be extended to the total length of 3 ft. A fter 3 ft. has been cut, a length- ening piece is screwed on and work proceeds. Addi- tional lengthening pieces are added as required.

As th e roadways advance new columns m ust be set.

The system of lengthening tubes m ay be extended to about 230 ft. when necessary. The driving device may be sh ifted from the entrance into th e gallery and the work carried on to any desired point.

F IG 3

F ig s. 3 and 4— Cutting a Room in One Direction or in Two

T h e f ig u r ę o n t h e r i g h t s h o w s t h e c u t t e r s w o r k i n g i n t w o d i r e c t i o n s o n a l o n g w a l l f a c e , t h e c o a l l e f t b y t h e c u t t e r d o u b t l e s s b e i n g r e m o v e d b y p ic k s . I n t h i s c a s e lo a d i n g c a n b e p e r f o r m e d r e a d i l y , a s t h e t r a c k

c a n b e s e t a l o n g s id e t h e d r i v e s h a f t . ''D rivin g Eguipm eni’