cme AMErICan Machinist

Vol. 53





HE mechanics of the oil fields are both varied and interesting, and, aside from the lure of oil pros- pecting which seems to get under a man’s skin the same as mining, the actual mechanics.of the job are of especial interest. Through the kindness of C. E. Reed. vice president and general manager of the Reed Roller Bit Co., Houston, Texas, I was able to visit the well-known Humble field and watch some of the opera- tions at first hand and at

from horizontal to vertical, drive the toolhead (calied a rotary table) that turns the boring tools and the string

of pipe which must reach to the bottom of the hole. Then there is a good-sized water or slush pump (two are usually connected) which forces water or slush down the drill stem and as it returns, coats the side of the hole with mud and also floats out the dirt and pulverized rock as the boring head descends. The driving of the ' toolhead which turns the

the same time have the benefit of Mr. Reed’s ex- perience in oi] well work. From the minute it is de- cided to drill a well, money begins to flow out of the treasury with remarkable ease and regularity. The

The drilling of oil handling of oil after it mechanical problems, closely akin to the These include

cutting tool may be

wells, is found, some of


sundry other machinina operations,

drilling bar naturally re- quires considerable power and is subjected to hard usage, owing to the irregu-

and the pumping and present many which are very

of the machine shop. larity in the hardness of

boring and milling, together with the earth and the rocks in which the which are encountered.

several thousand feet below This necessitates the use

erection of the derrick or the earth’s surface. The mechanism used in of material which will not frame, averaging about 100 pumping also involves interesting problems in only be strong enough to ft. in height, gets away power transmission. resist the stresses, but

with the first thousand dol-

which can stand an increas-

lars, on which there is usually no salvage as the derrick is always left stand- ing unless it is destroyed by being blown to pieces or by fire. Then comes the drilling machinery, which usually has a steam engine and boiler of from 50 to 60 hp. capacity, a goodly array of chain reduction gearing between the engine and the driving head of what is | practically a vertical bor- ing machine. The center view in headpiece shows a


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Les Ee aoe by sae a Apa 8,93


Nagase LAA ee (9 ~ normal supply.

ing amount of punishment as the hole becomes deeper. The tool is connected to the driving pipe by a rigid socket which is made of a steel forging pierced from the solid. Some idea of the sockets and the quantities in which they are used can be had from Fig. 1, which is a view taken outside the forge shop of the Lucey Manufacturing Co., Hous- ton, Texas. The quantity shown is, in fact, below the As the too]

little of this. Bevel gears

that transmit the motion FIG. 1. A PILE

goes down, lengths of pipe

TOOL JOINTS are added. Only one joint



can be added at a time. While this is not such a difficult matter at the beginning of the hole, it is in creasingly serious as the hole goes down. When we consider that many of these wells reach a depth of over 3,000 ft. (with 4,000 ft. by no means uncommon) the weight of pipe which must be handled becomes an increasingly important figure. The tools are handled by a heavy block and a steel cable, power beng obtained from the engine of the power plant. This cost of handling the pipe makes it all the more important that the bor- ing tools remain sharp as long as possible in order to avoid the cost of pulling them out of the well for sharpening. The pulling out process means stopping the drilling or productive work while 3,000 or 4,000 ft. of pipe ar. pulled out, uncou- pled at every 60 or 80 ft. and replaced after the new or sharpened tool has been put in place, before the boring can continue. Here is where more of the treasury fund melts away. Roughly speak- ing, the cost of drilling may be estimated at a minimum of $5 per ft., which of itself means a tidy little sum on a 4,000- or 5,000-ft, well for only a hole in the ground.

Drilling a well is bad enough when all goes well, but when things begin to happen there is more excitement and uncertainty, not to mention expense, than the average shopman dreams of.

Just before we reached this field, this particular well, which was approximately 2,200 ft. deep, had struck a gas pocket of sufficient pressure to blow the tools out of the well for a considerable distance and to fill the casing which had fullowed the boring tool down, with rock and all kinds of debris. This obstruction has been jammed in so tightly by the gas pressure that the ordinary drill- ing head or bit made very little impression on it. Mr. Reed sent for one of his special boring heads to go The boring head was successfully








through this rock.


Vol. 53, No. 15

jused, and after continuing the boring for about 300 ft. more, oil was encountered. It then became necessary to put in a strainer to keep out the sand.

The oil strainers are usually made by drilling a pipe fairly full of holes and then wrapping the outside of it with a wire, winding it around the pipe so as to leave a very slight space between the wires, an opening of only a few thousandths of an inch being the usual practice. The wires are then soldered at intervals so as to retain them in the relative position and after a pointed cap has been placed on the lower end the strainer is complete. Strainers are very necessary to prevent sand from clogging the pipe and also to keep sand out of the pump which forces the oil to the surface.

In the setting of the strainer at this well further diffi- culties were encountered, due to the end of one of the pipes in the collar being slightly cupped. An attempt to mill off this obstruction, by putting down a 6-in. mill- ing cutter on the end of the pipe, resulted in the loss of the milling tool in the well. Grappling failed to recover it, and, being of hardened steel, it was almost impossible to cut it away with any tools which could be sent down.


The next step out of the difficulty is what is known as “side tracking” which is done by milling out the side of the pipe for a considerable distance above the obstruc- tion. The operation of side-tracking is usually per- formed by lodging in the well, above the obstruction, what is known as a “whip stock.” This is round at the bottom end and of a diameter slightly under the inside ef the pipe and anywhere from 10 to 15 ft. long. It is bevelled off on one side so that at the top it is a thin crescent shape. The whip stock forces the milling tool against the side of pipe to be cut. The tool most fre- quently used is shown in Fig. 2.

This tool is screwed on the lower joint of the drill stem and cuts out the side of the pipe for a considerable distance, so as to make a comparatively slight angle for the new hole. Through this long hole milled through the side of the casing, a new well-hole is drilled as far down as necessary. This hole through the side of the casing is usually 5{ or 7{ in. in diameter, but may be any size; and through it the drilling bit is operated by the drill stem, which is usually 4 in.-pipe. This opera- tion is a very common one in drilling wells by the rotary


6 A


rooL FOR








October 7, 1920


Milling cutters of various sizes, shapes and kinds, both internal, external and ends, are used at various times as necessity arises. It also occasionally happens that it is desired to pull out an old casing, and, if this has been in the ground any length of time, it is almost impossible to do so, owing to the pressure. In such cases, a tool, of the type shown in Fig. 3, is lowered into the pipe, and holes are punched in the walls at intervals, so as to allow water to be forced down the pipe and through the holes, washing the outside and loosening the earth which is holding it firmly in place. A little examination will show that, as this tool is lowered into the pipe, the cutter A drags or trails, and offers no resistance to its passage. When however, it is desired to punch a hole, the motion of the tool is simply reversed. As it is pulled up the point of the cutter catches the side of the pipe and forces a hole through it. The tool is then raised a short dis- tance with the cutter trailing once more, and, by simply reversing the motion, or forcing it down, another hole is punched, leaving the tool in position to be pushed down the pipe as far as may seem desirable. By this means, it is easy to perforate pipes at any desired depth and many have been recovered by its use.

After the oil well has ceased to gush or flow, the ques- tion of pumping has to be looked after. Vast quantities of oil are obtained in this manner after the gas pres- sure is reduced so the oil will not flow. The pump is a simple affair, usually having a barrel about 6 ft. long, this being sometimes made in 12-in. sections but usually made in one piece. The plunger carries a ball valve top and bottom, the whole thing being very simply constructed. The pump as a whole is shown in Fig. 4 and consists of a skeleton frame fastened to the floor of the derrick. The pump rod A is moved up and down by the bell crank, the usual stroke being about 12 in. Suitable linkages connect the end of the bell crank with the pump rod and avoid any tendency to cramping. The pump cylinder and plunger are lowered nearly to the bottom of the well and located with regard to the depth of oil. Motion is imparted to it by means of the connecting cables.

The problem of getting the power to the pump involves considerable rough and ready engineering, which is extremely interesting. At this particular field the method of transmitting power is that of the Joseph Reid Gas Engine, of Oil City, Pa., which consist of a large wheel, Fig. 5, mounted on a vertical shaft and carrying two large eccentrics beneath. From the straps

Get Increased Production—With Improved Machinery 655

on these eccentrics, cables radiate in as many directions as may be necessary to reach the various oil wells. The throws of the eccentrics are approximately the same as the stroke of the pump and the various methods of getting the cables from the source of power to the pumps, which may be half a mile away across the field, are interesting.


Fig. 6, shows a few of these cables coming out from the power house, those shown being only a small por- tion of the number in actual use. The cables are


fastened to the eccentric straps by means of clevises and suitable pins, and if then for any reason it is desired to stop any particular pump, it is only necessary to dis- connect one of the cables at aconvenient point and fasten it to a short stationary cable which holds it in position ready to be again coupled when desired.

In some instances it is possible to run the cables directly from the power to the pump, even though this be half a mile or more away. In such cases, timbers which are usually somewhat larger than railroad ties are set into the ground and holes bored through them at the proper places to guide the cables and allow them to work freely. The cables are then threaded through these holes and connected to the power wheel.

. a




Frequent application of crude oil to the cables as they pass through these supports reduces friction and also delays wear of the hole. The cables are usually kept about 18 in. from the ground.

Figs. 7, 8 and 9 show cases where it has been neces- sary to transmit power “around the corner” and the method used for so doing. In Fig. 7, the power is brought out on the cable A, coupled to the large cross- beam B, which is fastened to the post C by a wire rope and a cable D run from the other end in the direction of the arrow to a well which could hardly be reached in any other way. Each end of the crossbeam rests on timbers as shown, crude oil again supplying the neces- vary lubricant.

In another case, the well was so located that while a direct line could not be used, the obstruction only required a small deviation. This was secured as shown in Fig. 8. The power line comes out at A, coupled into a shackle at D. The shackle is held in position by the



cable C, and moves in a radius from the post F. The pump line E couples in the other end of the shackle and is almost a direct continuation of the cable A.

This swinging slightly reduces the length of the stroke which is restored by the connection shown in Fig. 9. The power line A is the lower coupling on the post B. The post vibrates and, as the pump line C runs off the upper end, the pump receives an increased stroke. These are only a few of the devices used, but give a good idea of the ingenuity displayed in this kind of work.

Device for Grinding Clearance Angles on Tools for the Automatic By F. P. ROGERS

The halftone presented herewith shows a holder for grinding the forming toois commonly used on automatic machines, enabling the operator to produce definite clearance angles with certiinty, even though he may remove the tool from the grinding machine many times.

The device consists of carefully finished base with edges ground exactly parallel; a swinging dovetail holder, pivoted at one end on the center Jine of the base, and graduated at the other end to facilitate setting to any desired angle; and a spring packing piece, or shoe to adapt the holder to smaller sizes of dovetail.

The device is to be used in conjunction with the magnetic chuck, the base being placed against the aligning bar of the chuck to locate it. After the correct setting is once obtained the device may be removed from the machine or the work released from the holder and replaced at any time with certainty of maintaining the angle.

This feature renders it of value for the reason that in the production of tools of the nature for which this device is intended it is frequently desirable to remove the work from the grinding machine for various rea- sons and during such periods the grinding machine is not “‘tied up,” but may be used for other purposes or by other operators. When the grinding of the tool is to be resumed the holder is replaced on the magnetic chuck with one side against the aligning bar and no “setting up” or trial cuts are necessary.

Besides the work for which it was originally intended the device is useful for grinding keys, wedges, or other pieces upon which a definite angle must be obtained.


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emesis. ot

October 7, 1920

OGRAMS 9 57 anna ‘ila IL

HE firm of R. Hoe & Co. is a long-established

manufacturer of printing presses in New York

City. For forty-eight years, since 1872, it has maintained an apprentice school as a supplement to the ordinary apprenticeship system in which a skilled trade is taught by the traditional method of working by the | side of journeymen on I] regular factory production. Ninety per cent of the man- ufacturing administrative

R. Hoe & Cx

force of the plant are said in most machine-building plants, is the traditional form of put together a mechanical

to be graduates of the school, here. This system is as well as all of the forty to sixty high-grade men em- ployed outside the factory in installing the presses. Thus, the school has high

being the chief feature.

Part I was publishe

apprenticeship modernized to meet existing con- ditions, a school meeting after working hours of one apprentice to five

Get Increased Production—With Improved Machinery 657

To be accepted as an apprentice a boy must be sixteen to eighteen years of age and a graduate of the elementary school, with the preference that he come directly from school rather than after a series of casual employments, during which his experiences lead him too

frequently to contract hab-

mcmama its of insubordination and »., New York, N. Y.

An apprenticeship system which has withstood the test of time and which is well adapted to use

shiftlessness. In addition to educational requirements, a simple test for mechani- cal deftness is imposed by described requiring the candidate to construction toy. A _ ratio

journeymen can not be ex- ceeded by agreement with the machinists’ union. On

n the Sept. 23 tssue.)

favor with the management

of the company, a factor which greatly lessens the danger of exploiting the apprentices by keeping them at machines or processes long after they have learned them, as is frequently the case where foremen and managers are not themselves apprentice trained. It is said that overtime production is not allowed to inter- fere with attendance at the school, and that apprentices are never laid off during even the dullest seasons.

Wivws | | ane 8


this basis there were on April 16, 1920, when the investigation was made, 173 apprentices. About sixty apprentices are taken on each year.

Apprenticeship is offered in the following trades:

Foundry . with 3-year course and 2 enrolled Machinist . with 4year course and 160 enrolled Electrician with 4 year course and | enrolled Sawsmith with 3-year course and > enrollec Patternmaker with 5 ir yIrs€ > enrolled

Total 173 enrolled



Over 90 per cent of the enrollment is seen to be in the machinists’ trade. Rates of pay for machinist apprentices are as follows:

First year—lI c. per hour $7 04 per wk Second year—24ec, per hour 10. 56 per wk Third year 42 per hour 18 48 per wk First six months, fourth year—56c. per hr 24 64 per wk Second six months, fourth year——70c. per hr 30 80 per wk

The shop schedule of the foundry apprentices is out- lined as follows: 6 months helping molder on the floor, tempering sand, etc.; 6 months coremaking; 6 months on bench; 9 months on the floor; and 9 months on dry- sand work; a total of 3 years.

For the machinists the schedule is divided into four groups. Group 1 is for one month at general work, tool room or cutting-off machines. Group 2 calls for work at drill press, two months; vise, two months; boring mill, two months; and keying machine and hand monitor, two months, or slotter, two months. Group 3 schedules work at planer, six months; gear cutter, six months; miller, five months; lathe, ten months. The

iG. 10. APPRENTICES IN A DRAWING CLASS work of group 4 is done at erecting for twelve months. This is a total of 48 months.

Sawmaking is to be considered a special phase of smithing and an interesting example of hand crafts- manship still surviving in industry. The apprentices spend the following periods on the various classes of work: Anvil, six months; punching, 3 months; repair- ing saws, 3 months; shanks, months; bit room, 3 months; setting and filing, 6 months; hardening, 6 months; anvil, 2 years 6 months. This implies that five years are required before reaching full journeyman’s standing.

The patternmakers serve for two years at various classes of work under a master patternmaker, followed by nine months in the foundry to learn the difficulties encountered in casting from a pattern, in order that their later work may be so constructed as to meet They then return to the pattern shop to complete their time.

» “0

foundry requirements.


At considerable expense the apprentice school has been installed in a section loft and equipped with three classrooms, a drafting room and a library, besides a lunch room. Views of the school are shown in Figs. 8, 9 and 10. The lunch room was installed so that coffee and sandwiches could be given the boys in the inter-

MACHINIST Vol. 53, No. 15
















FIG. 11.

mission between the closing of the shop at 5 p.m. and the classes, which begin at 5:20 and end at 6:45.

The school personnel consists of a supervisor, a drafting instructor and three teachers who handle the mathematics, English and mechanics. The supervisor, who divides his time between directing the school and office work, is himself a graduate of the school. The drafting instructor is drawn from the company’s draft- ing-room staff and the other instructors are technical graduates with positions in the city, but not otherwise in the company’s employ.

Owing to the relatively large size of the school and the fact that all students pursue a uniform course, instruction can be graded to suit the previous training of each apprentice and to provide instruction suited to his attainments no matter at what time of the year he may enter the school. For this reason the curriculum is divided into seven units designated as C-3, C-2, C-1, 3-3, B-2, B-1, and A. Ordinary students are expected to complete this in three years, the C units being taken in the first year, B units in the second, and A in the third.


= as

works MACHINE a conoucr res 0 TIMES seouneo =|


bn hae



‘3 h




October 7, 1920

The weekly time division or schedule of classes is as

follows: Class C-3 First night Freehand drawing

Mathematics—Review of fractions, decimals, ratio, square

root, etc Second night Mathematics English—Oral and written composition, punctuation and general expression of thought Third night English j Mathematics. .

Class C-2 First night Freehand drawing ae . Mathematics—Mensuration, simple equations in algebra, problems iliustrated by freehand sketches Second night Mathematics English—Continuation of «-3 Third night English Mathematics

R. H. & Co. Form 5143-717-s00

R. HOE & CO.’S Evening School for Apprentices


nuneeewersbeneesene oane ecece CLass

lenaaenes ........<<..s-. ae IIE Sire onan nine teameneisails ID ooo vac tieeeintaeetinen I ui wipidmsennieeh ane aneeaiahie ee

Mechanics .....-----

Mechanical Drawing

Average in Studies ___.

In order to be advanced, the apprenfice’s a verage ‘in Studies must be at least 65.

Shop Rating based on Workmanship Attendance and Conduct........



1 hr

2 hr 1 hr



Oe et i TERM-REPORT CARD FOR APPRENTICE WORK Class C-1 First night Drawing— Mechanical drawing commenced

Mathematics—Constructive geometry. Only such prob lems considered as can be done with the aid of compass and straight edge

Second night Mechanics—Heat, air, liquid, power and work with prob lems and experiments requiring simple apparatus

Third night English

Mathematics Class B-3

First night Mechanical Drawing; continued

Second night Geometry—Theoretical, with proofs of simpler problems; trigonometry of the right triangle use of tables of natural functions

English—W ritten work, des« ription and exposition

Chird mght Mechanics—Mechanical forces and friction Class B-2 First night Mechanics—Gear teeth and gearing Second night Mechanical drawing—Cears, showing characteristics of involute and cycloidal teeth

Cinrd night Mathematies—Strength of materials, especially applied to proper proportions and materials for machine parts English, continued Class B-I First night Mechanical drawing—Free hand sketching and dimen-

sioning and lettering of plans, sketches, and data for making prints /

Second night Mechanics—Power transmission as used in a factory. Pul- leys, shafting, belting, gearing. Electricity, what it 1s and how it operates

English—Report writing and similar work

Vhird night Mechanics

JClass A First night Mechanical Drawing—Free hand detail drawings for the different parts of a simple machine, such as belt-shifter arrangement, and from these to make up a general \ssembly ~econd night Mechanics —Fssentials of machine designing

5 ha

14 hr | hr } br

1 he 1} hr 1} hr hr

t hr 1} br

1) hr

Get Increased Production—With Improved Machinery 659

Careful records are kept of the progress of the apprentiee both in his shopwork and in the apprentice school, term reports being sent to the parent and prizes being conferred on those with the best records in both shopwork and school at the annual closing exercises held in June.


The forms in use by this company for handling the records of its apprentice department seem well adapted to the purposes intended. There is, first, the application form, both front and reverse of which are shown in Fig. 11, which is filled out and fited in the employment department when the boy first seeks entrance into the training school. There is, also, the card, Fig. 12, on which a cumulative record is kept of the apprentice and his work in the different departments of the plant. This is transferred with the apprentice from one department to another as he progresses from one machine or type of work to another. Finally, there is the term report card, shown in Fig. 13, which is filled out and sent to the apprentice’s parents each term.

The apparent high quality of the apprentices in this plant and the generous provisions for their instruction, both in the shop and school, would lead one to believe that the management is employing considerable effort in the training of its future mechanics. The program may be commended as an example of satisfactory mod- ernized apprenticeship.

Molding a Drum With Deep Sand Pockets

By M. E. DuGGcAN

An interesting article under the above title appeared on page 1,056, Vol. 52, of American Machinist. There are some points in the description of the molding operation that I do not quite understand and therefore I am going to ask some questions; not with intent to be sarcastic, but to add to my fund of knowledge concerning practical pattern making and foundry practice.

From the description I would infer that the pattern was made to mold in green sand, using a core for the central hole. Is this correct?

The depth of the pockets is given in paragraph four as 9 in., but aothing is said about the length and diameter of the drum; thickness of wall; thickness of the web at the bottom of the arms, etc. I would like to know these figures.

When the alterations on the pattern were made that enabled unskilled labor to produce 10 castings per day against 3 castings in the same time with the original pattern and the services of a skilled molder, were the alterations made by the same patternmaker that made the original pattern? If not, was his attention called to the alterations and their result so that he would not make the same mistake a second time?

If I were to make this pattern I would construct it to be molded with the ribs in the drag in green sand, provided there was body enough to the sand to support itself. However, if it was made to mold in green sand with the ribs in the cope no alterations would be neces- sary to enable the molder to mold the ribs in core; the pattern could still be used as a core box. All that would be necessary in this case would be to suspend the core from the cope with wires.



Vol, 18, -No..15

Motor-Flywheel Drive for Merchant Mill

By J. B.



Designing flywheels for rolling-mill use is not a simple matter; but the author gives in this dis- cussion a treatment of the problem which is con- cise, yet quite sufficient for ordinary needs, and in such a form that it may be readily adapted to

use in actual design work.

T IS our purpose to present in this article an outline

of the calculations necessary to check the electric

drive for a 22-in. merchant mill. The mill is a 22-in., three-high, merchant mill of four stands. It is driven by an induction motor of 1,800

rated horsepower, taking three-phase, 25-cycle, alter- nating current at 6,600 volts, in connection with a heavy flywheel coupled to the motor shaft and a herringbone gear and pinion, as shown in Fig. 1. In checking this drive two distinct steps must be taken:

First: An investigation must be made of the inter- action of the motor and flywheel wher the mill is running at maximum capacity, in order to determine the sufficiency of the to perform the work required.

Second: the flywheel rim and arms.


An investigation of the stresses induced in


a’) Drop in Speed due to load.

The following notation and formula are used in the calculations:

hp Horsepower of motor;

hp Friction horsepower ;

hp Maximum horsepower at peak load;

R R.p.m. at no load (synchronous speed) ; R R.p.m. at full load;

R R.p.m. at friction load (flywheel speed) ; T Full-load torque at full-load speed;

Artiller |



Using the


= [— Birt oa , g” Pl 4" ) ' . . rf ca/ leeth | Face. Deg v C. bie yM we Pb > a | yA a Flywhee/ 7 7 a Ux 45 “1 S ¢ e c c | Bearing Y ( UP IIINIG Motor Coupling y + =e A oO" o g) NS Pinion: Cast Steel, 0.35 to 0.45 ae. es Carbon. 2-88" PD. 57”C P 4 Cut Helica Teeth Yy 43" Face. 22 Deg. Involute. FIG. 1. GENERAL ARRANGEMENT OF THE DRIVE FOR IN. MERCHANT MILL

Friction-load torque at friction speed fF. ; Maximum torque at friction speed R,; Maximum torque above 7,; Fuil-load torque at speed R,; Maximum torque exerted by per cent of full load; Actual! torque exerted by flywheel; Per cent of slip at full load; Per cent of slip at friction load; Total slip in per cent; Total slip in r.p.m.;

Per cent drop below initial flywheel assisting motor; Per cent drop below friction speed with

flywheel assisting motor;

tiywheel in:

speed with

Drop in r.p.m. with flywheel assisting motor ; R.p.m, drop in speed below synchronous speed ; Per cent total actual drop below syn- chronous speed with flywheel assisting

motor; Maximum load above friction in per cent; Total inertia effect of motor and flywheel; Length of peak in seconds; Length of interval between


peaks in

above notation we have the following for

hp X 5,250

i - 1 R. R —R, Ss (2) R s hp, are) (3) hp R, R SR (4) hp, X 5,250 - 6) | R, 5 hp. X 5,250 ", - R. = (6) r r r (7) re hp X 5,250 r R. ae T y ; (9) I T. The formulas for calculating the

drop below initial speed which takes place with the flywheel assisting the motor are exceedingly complicated. This drop in speed is represented in our notation by S,; but its value ma) be readily found without any calcula- tions by using the following factors from the charts published in the Amer ican Machinist for Mar. 7, 1912, in an article by Messrs. Riker and Fletcher:

October 7, 1920

T; Wr? S,; and ¢t The results given here were obtained by that method. : . S,= S, X’S, (11) A 5S, = J. X BR, (12) es oe! No attempt is made here to give the derivation of

the equations used; but those who care to study the ; theory are referred to the various papers on the subject

published in the transactions of tne American Institute

of Electrical Engineers. 5 I (b) Recovery of Speed. if L Friction horsepower in per cent (13) F T. = TT. (14)

S, = SR, (15)

SOLUTION FOR SPEED DROP In our particular case we proceed as follows, the : specifications and conditions of operation being: a 1,800-hp. motor;

250 r.p.m. (synchronous speed) ; 243 r.p.m. at full load;

Slip 10 per cent of full-load speed when carrying

175 per cent overload; Friction hp. 20 per cent of 360 hp. Peak load 6,534 hp.; Duration of peak load Interval between peaks

0.87 seconds; 2.0 seconds.

Substituting these va'ues in the above formulas we

nave: Full-load torque at full-load speed T 1,800 5,250 243 250 243 250

or 2.8 per cent

Slip at full load S =

7 en | 360 X 2.8 Slip at friction load Ss 1,800 0.56 per cent

Friction-load speed flywheel speed 0.0056 250 248.6 r.p.m. Friction-load torque at flywheel speed T, = oe” 7,603 ft.-lb. Maximum torque at flywheel speed 6,534 & 5,250

= : 7 98 ) eo . T: 948.6 137,986 ft.-lb Maximum torque above friction T, - 7,603 130,383 ft.-lb. Total intertia effect of rotor and flywheel 2,260,000, since, { Wr of rotor = 460,000 ) (Wr of flywheel = 1,800,000) Full-load torque at flywheel speed 800 5,250 Ton ee os SR OES HiT




38,889 ft.-lb.







== Wr


Get Increased Production—With Improved Machinery



Maximum load above friction in per cent 130,383 38,013

Since an overload of 175 per cent causes a drop in speed of 10 per cent cf the full-load speed, and we

have an overload of 343 per cent, we find that 343 - 175, or 168 per cent additional overload, will cause a

L= 3.429, ar 348 per cent (9)

further drop in speed of 168 0.028 4.7. per cent. Consequently, the total drop is 10 + 4.7 14.7 per cent, which is the value of S.,. Total slip below flywheel speed in r.p.m. S 248.6 < 0.147 36.54 r.p.m. (10)

In order to find S,, the drop below initial speed which takes place with the flywheel assisting the motor, we enter the previously mentioned chart, using the fol- lowing factors:

T; 130,383 Pe Wr 2,260,000 ~ 9-09%6

S, 36.54 and ¢ 0.87 seconds,

and we find that S, 36 per cent of S.,.

S, 0.36 « 14.7 5.29