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We are advised by Carrington Phelps, Secretary of the professional Classes War Relief of America, having offices at 33 West 42d Street, New York, that this organization is now prepared for active relief of professional men who have enlisted in military service or are assisting the Government in the civil service or in civil life, at the sacrifice of their usual sources of income. The organization has found that the main obstacle to such relief is the hesitancy of this class of persons to make known their needs. Relief cases have to be sought out; the organization has already found some but has asked the cooperation of the Institute to assist in finding as many more as may exist. It is suggested that the Institute can render useful service in this connection, first, by informing our members of this feature of war relief, by being on the alert to report those needing relief, and to make all possible inquiry after such cases. It is further desired that information as to all such cases be forwarded immediately upon their discovery.

Jan 3, 1918

Since the beginning of the 20th century the world has been trying to find a new political system, even as it did at the end of the 18th century. The French Revolution instigated the destruction of absolute monarchies when Napoleon unwittingly showed the masses the advantages of freedom, as opposed to the abuses of unlimited power by the imperialists. In spite of advances in culture, science, and technology during the past 50 years, there is a hangover of laissez-faire economic principles. Failure to divert the trends of minority pressure groups has caused two world wars and is the basis for the current social unrest and turmoil. In the ebullition of ideas there have risen to the surface the dregs of ideas, old and new-Nazism, Fascism, Russian Communism-a hodgepodge of imperialistic, socialistic, communistic and capitalistic maneuverings where state monopoly of capital enables ruthless exploitation of the masses. The United States owes much of its industrial greatness to the work of pioneers in the mineral industries. The task of the pioneer was to locate and develop in a rude way the mineral resources of the nation. Today, mineral industries leaders are still in great demand, but for a different purpose-to direct intelligent utilization of the limited, waning, submarginal mineral resources. Today the need is for trained earth scientists, mineral

Jan 1, 1950

By George Watkin Evans

During the past ten or twelve years, the average reader of newspaper and magazine articles has been led to believe that enormous deposits of high-grade coal exist in the northland and that these can be mined for practically nothing. But much of the reputed glitter and attractiveness of Alaskan coals disappears when viewed at close range. Many areas of coal-bearing rocks are widely distributed geographically from Cape Lisburne, on Bering Sea, to Admiralty Island, south of Juneau. Bituminous coal is found at Cape Lisburne, on the Bering Sea, at Five Finger Rapids on the upper Yukon, and at Herendeen Bay and Chignik Bay; lignite is found on the Kobuck River, along the Yukon River from points near the mouth to Tonakat, near Rampart, at Dawson, on the east shore of Cook Inlet, and in the Tanana Valley, 50 mi. south of Nenana. The Susitna and Matanuska Valleys contain coal ranging from lignite to anthracite, and in the Bering Lake district, there are coals ranging from semi-bituminous to anthracite. No effort will be made to describe all of these fields, but the writer will confine himself to the four principal fields, namely, the Nenana field! in the interior of Alaska, tributary to the Fairbanks district; the Matanuska field, in the Matanuska Valley; the Kachemak Bay field on the east shore of Cook Inlet; and the Bering River field, east of the mouth of Copper River. Nenana Coal Field The Nenana field occupies an area east of the Nenana River 70 mi. (112 km.) southwest of Fairbanks and approximately 50 mi, from the town of Nenana, which is located at the junction of the Alaskan Railway and the Tanana River. It is on the northern flank of the Alaskan Range and occurs within the foothills of that district. The elevations range from 1000 to 4000 ft. (304 to 1219 m.). Future developments may prove the field to extend from a considerable distance west of the Nenana River to the headwaters of the Tanana River. The coal measures are of Tertiary age and are probably Eocene. They are not badly deformed by folding, but portions of the field show

Jan 1, 1922

By W. L. Phillips

Stress-train curves were obtained for single crystals of silver, Ag-5 pct Zn, Ag-10 pct Zn, and Ag-20 pct Zn tested in tension and shear at 78°, 195°, and 297°K. At room temperature the critical resolced shear stress gC increased, the length of' the easy-glide region increased, and the rate of' work hardening dwving easy glide decreased with increasixg zinc concentration. The change in the ratio of uc at room temperature to that at lower temperatures was significantly greater for the alloys than for pure silver. It was found that an increment in stress was necessary to continue slip when the slip direction was rotated 60 deg. The magnitude of this increment increased with strain for all alloys, increased with zinc concentration for a given strain, and for a given strain increased with decreasing -temperature. DESPITE its practical importance in improving the mechanical properties, alloying is not fully understood. Except for copper alloys few sets of systematic data are available. Von Goler and Sachs' studied the deformation of Cu-Zn alloys of increasing zinc content and found that, for dilute alloys, the critical resolved shear stress increases linearly with concentration. The range of easy glide was found to increase with increasing zinc content. Schmid and seliger,2 Sachs and Weerts,3 and Osswald4 have shown that with Mg-A1, Au-Ag, and Cu-Ni crystals, respectively, the critical resolved shear stress also varies linearly with concentration. More recently, Linde and his coworkers have investigated the variation of the critical shear stress of copper alloyed with tin , antimony, indium, germanium, silicon, nickel, and gold. They found that the slope of the critical resolved shear stress is related to the change of lattice parameter with composition, and also to the difference in Goldschmidt's atomic diameter between solvent and solute atoms. Garstone, Honey-combe, and creetham6 have shown that similar relationships can be found for small additions of silver, gold, and germanium to pure copper. They found that, with increasing silver or gold concentration, the critical shear stress for glide is increased by alloying, and so is the range of easy glide, which reaches as much as 60 pct for 0.50 pct Ag alloy and 0.62 pct Au alloy, as compared to 6 pct for pure copper of similar initial orientation. They also found that the alloying additions had little effect on the rate of hardening during easy glide, the slope scarcely changing with increasing alloy content. General secondary slip was detected only when the crystals began to harden rapidly. Although the slip appeared to be very fine in the early stages of deformation, coarser slip bands were formed towards the end of the extensive easy-glide range. The present investigation describes the deformation characteristics of single crystals of Ag-Zn containing different concentrations of zinc. Tension and shear testing were used for this study. EXPERIMENTAL PROCEDURE The method of growing the single crystals, sample preparation, and method of testing have been described in detail previously.' EXPERIMENTAL RESULTS A) Tension-Room Temperature. The initial orientations and stress-strain curves of single crystals of silver, Ag-10.0 pct Zn, and Ag-20.0 pct Zn are shown in Fig. 1. It is evident that there is considerable change in the stress-strain characteristics as a function of zinc concentration. The effects of zinc concentration on the critical resolved shear stress for both CU-zn8 and Ag-Zn alloys are summarized in Fig. 2. At all concentrations the resolved shear stress of the Cu-Zn alloys is higher than that of the Ag-Zn alloys. The resolved shear stress increases parabolically as a function of composition for both alloy systems. The length of easy-glide region increased with increasing zinc concentration, Fig. 3b). As the length increased the slope (do/de) decreased slightly, Fig. 3(b). Metallographic investigations demonstrated two significant effects of increasing zinc concentration. First, the amount of clustering increased, compare Figs. 4(a) and (b). The slip lines changed from uniform in pure silver to clustered in the Ag-20 pct Zn and Ag-30 pct Zn alloys. Second, the amount of cross slip decreased as the amount of clustering decreased.

Jan 1, 1968

By J. C. Lee

This investigation considers the penetration of a crack through an interfacial boundary separating two materials. The interface is assumed to be an imperfect bond characterized by frictional resistance and the cracks are assumed to be pressurized. The formulation is achieved through the use of complex variable methods together with the application of dislocation solutions. Results are given in the form of dimensionless variables that represent the injection of an incompressible liquid.

Jan 1, 1984

By J. W. Snavely

THE high tension belt conveyor is introducing a new and tremendously expanded era of low cost bulk material handling. High tension belt conveyors are generally those installations involving very long centers, high lifts, or drops, in which the belts are stressed up to their maximum tension values, and further, where the belt construction provides tension capacity far beyond what is possible with conventional belt constructions. With these high tension installations, the magnitude of the forces involved demands careful refinement of accepted design practice in order to achieve optimum balance of all factors.

Jan 3, 1951

The centenary of Julia Ward Howe, author of "The Battle Hymn of the Republic," is of particular interest to the members of the Institute because of the very active part that has been taken in the affairs of the Institute by her son, Dr. H. M. Howe. By an order of the Board of Education, the one hundredth anniversary of Mrs. Howe's birth, May 27, was observed in the public schools of New York City with the singing of the fatuous battle hymn. Boston, the city of her adoption, celebrated her centenary by a service in the Church of the Disciples, where Governor Coolidge made an address, and in which John Andrew Post took a prominent part. General Pershing sent a letter, which was read by the Rev. Abraham Mitrie Rihbany, in which he said: "It is a great privilege to bear witness to the widespread effect of ?The Battle Hymn of the Republic? on the morale of the fighting men. It is unique in its religious fervor and enthusiasm and whenever sung it can have but the same effect which it produced when it was first sung in the Civil War."

Jan 7, 1919

By Stanley M. Miller

For rock or soil materials assumed to be generally isotropic and homogeneous, seepage theory and analytic geometry can be used to develop a mathematical technique for estimating the steady state, pie-zometric drawdown to a slope face. The resulting parabolic drawdown curve is a function of slope angle and the height of the original water table above the slope toe. When the slope is cut at a rate faster than that which allows a steady state to be attained, a non- steady state analysis approximates the transient drawdown. Monte Carlo simulation provides realizations of possible drawdown curves that can be included in slope stability risk analyses.

Jan 1, 1983

By F. E. Brackett

THE simplicity of the propeller or disk fan, its small size and low cost, has, in recent years, led to an extended use of ventilators of this type at mines where only slight pressure is required. On this account the author of this paper has prepared for the new edition of Peele's Mining Engineers' Handbook a more accurate method of computing the required size, power, and so forth, than was possible for the first edition. The main object of this paper is to set forth the data collected in the course of that work, and to discuss the subject with more latitude than would have been advisable in a handbook, even if space had been available. Theory of Fans A great deal has been written about the theory of fans from Rankine's time down to the present. Nevertheless a rigid mathematical analysis of the propeller fan seems to be wanting. A general idea of the mechanics and difficulties in the way of analysis may be gathered from the following: The useful pressure and velocity effects of the oblique impact of the vanes on the axial current would evidently be nil if the blades were perpendicular to the plane of rotation, or if they were of such helicoidal form that the screw pitch multiplied by the speed represented an axial velocity agreeing with the actual velocity. Somewhere between these zero angles there is a pitch which, under given conditions of flow, would produce the maximum useful effect. A true helicoidal blade can be so arranged that it would offer no retarding effect on the air current at any part of the wheel, provided the axial velocity be assumed the same in all parts of the cross-section of the air course, but if plane surfaces are used, it is possible, under some conditions, that the air would be retarded at the middle parts of the wheel while it was accelerated at the circumference. Whatever be the form of vane, it seems evident that the tips are far more effective than the center of the wheel, because of their higher velocity. For this reason some investigators believe that a backward current forms through the middle of the wheel and that part of the air is circulated in a radial axial loop. Ignoring the possible existence of this eddy and the friction of the walls of the air course; and assuming the axial velocity of the air through all parts of the wheel, some rational analysis of the impact might be made according to the theory of deflecting surfaces, were it not

Jan 1, 1928

By Shosei Serata

Conventional roof bolting may be giving ground to a new technique that utilizes only the ground itself to stabilize mine openings. This newly developed stress control technique (SCT) has initially been used in sedimentary ore bodies that are both overlain and underlain by weak strata. The technique is also suited to the design of production panels and main entry systems, and is readily adaptable to room and pillar as well as total- extraction mining, including both shortwall and longwall coal mining. In applications where the technique has been used, the requirements for roof bolting and floor renewal were virtually eliminated. The SCT comprises three basic methods and covers a wide range of problems associated with failing roofs and heaving floors in underground mines (see Table 1).

Jan 5, 1976

The primary purpose of the Institute is to advance the technologic and engineering arts embraced by it through interchange of knowledge. This can best be done by the presentation and discussion of technical papers by its members. Short practical papers are especially welcome. An author should always satisfy himself that his material is of a quality that will be a credit to him and to the Institute. The preparation of a good paper frequently leads to a reorientation of the author's thoughts, and publication contributes much to the professional standing of the author. Members are urged to submit papers presenting the results of their work. Attention to the following suggestions will greatly further the prompt and efficient handling of manuscripts.

Jan 1, 1944

By John Johnston

The actual amount of any metal volatilized from a mixture of metals depends on the magnitude of its partial vapor pressure under the specified conditions of temperature, and on the circumstances attending the heating—in particular, on the duration of heating, the volume of gas coming into actual contact with the surface of the metal, the extent of this surface, and the rate of diffusion of the volatile metal from the body of the melt toward the surface.' If two (or more) metals are volatilizing from the same mixture of metals, the several conditions are identical except for the difference in partial pressure and in rate of diffusion of the volatilizing metals; the second of these two factors is without doubt only of secondary importance as it is probable that the rates of diffusion of the volatilizing metals would be very similar. Hence, in order to gain an estimate of the relative amounts of two metals that may be volatilized from a given mixture, it is necessary to know the vapor pressure, or, more precisely, to ascertain for each metal its partial vapor pressure in equilibrium with the liquid (or solid) alloy under the particular circumstances. The partial pressure of each constituent depends on the effective concentration of that constituent in the alloy2 as well as on the vapor pressure of the constituent when pure, and it can be calculated when both of the above factors are known. The first step, therefore, is to ascertain the vapor pressure of the several pure metals. Vapor Pressure of Pure Metals The experimental data on the vapor pressure of the several pure metals with which we are here concerned are not so accurate as could be wished, nor have the determinations been made in general at temperatures such that the results can be used directly. In a previous

Jan 1, 1919

The papers presented at the International Congress, held in San Francisco, Cal., Sept. 20 to 25, 1915, are published in 11 volumes of Transactions. In addition, an index volume is published, containing .besides the author and title index, a report of the business meetings of the Congress, and a brief digest of each paper presented. The following is a schedule of the volumes: Index and Digest.-General proceedings, indexes and digests. Vol. I. Panama Canal. II. Waterways and Irrigation. III. Municipal Engineering. IV. Railway Engineering. V. Materials of Engineering Construction. VI. Mechanical Engineering. VII. Electrical Engineering and Hydro-electric Power Development. VIII. Mining Engineering. IX. Metallurgy. X. Naval Architecture and Marine Engineering. XI. Miscellaneous. Aeronautics; Refrigeration; Agricultural Engineering; Engineering Education; Heating and Ventilation. Remember the New York Meeting, Feb. 14 to 17, 1916.

Jan 12, 1915

By Howland Bancroft

THE writer has observed that some confusion is experienced by many mining engineers in making vertical sections of ore deposits in mining properties which they have examined. Having much examination work calling for the correct interpretation of vein structure and the subsequent platting of the same on sections, it has occurred to the writer that the accompanying diagram may be of use to others who at times may be called upon to prepare numerous sections. For example, a great mass of data on-strike and dip of ore bodies is collected underground in separate

Jan 7, 1914

By C. A. Stickels

The preferred crystallographic orientations developed during recrystallization of polycrystalline electrolytic iron sheet, cold-rolled 90 pct, were ivestigated. Recrystallization at 500° or 565° C for relatively short limes produces a texture which is similar to the rolling texture. A duplex partial fiber texture, significantly different from the rolling texture, is found when the annealing time is increased. Recrystallization at 700°C also produces a sequence of textures with increasing annealing time. In order of their appearance, these textures are: 1) the duplex partial fiber texture found at lower temperatures, 2) a four-component texture "near {322}(296)", 3) a {112)(110) +(111)(110) texture, and 4) a two-component "near {554)(225)" texture. Secondary recrystallization, or discontinuous grain growth, accompanies the development of the latter texture. However, the "near {554} (225)" texture was nol observed when secondary recrystallization occurred under other conditions. All of the ideal orientations found in recrystallization textures can be accounted for by the growth of minor components of the deformation texture. IN recent years there has been increased interest in improving the drawability of metals by controlling the preferred crystallographic orientation of the sheet.1-l3 Since more low-carbon steel is drawn than any other material, considerable attention has been focused on the properties of sheet steel. Efforts to improve drawability through texture control have been hampered by the lack of any published systematic study of the recrystallization textures developed in iron annealed below Acl. The purpose of the present work was to supply some of this missing information, specifically, the recrystallization textures obtained by isothermal anneals of polycrystalline iron, cold-rolled 90 pct. LITERATURE REVIEW—DEFORMATION TEXTURES Barrett14 reviewed and summarized the investigations of rolling textures in iron and low-carbon steel prior to 1952. The texture of heavily deformed iron (rolled 90 pct or more) is described as consisting of two partial fiber textures. The dominant fiber texture (designated here as fiber texture A) has a (110) fiber axis in the rolling direction and includes the orientations (001)[110], {112}( 110), and {111}(110). The secondary texture (designated here as fiber texture B) is described as having a (111) fiber axis in the sheet normal direction, and includes the orientations {111)( 110) and (111)(112). Since the publication of Barrett's book, there have been two detailed studies of the deformation texture in polycrystalline iron. In both instances, the more sensitive diffractometer methods of pole-figure determination were used. Bennewitz15 studied the cold-rolling textures developed in polycrystalline low-carbon steel and a 3 pct Si steel. He determined (110), (2OO), and (222) pole figures for specimens reduced 30, 50, 60, and 90 pct and analyzed his results in terms of partial fiber textures. He distinguished three stages in the development of the final deformation texture. 1) Grains rotate to form two incomplete fiber textures, with (110) fiber axes inclined 30 deg to the sheet normal toward the rolling direction (fiber texture B). After 50 pct reduction, the highest density of poles is near an ideal orientation {554}(225), the two components of which are members of this duplex fiber texture. 2) With increasing amounts of reduction, grains rotate about the former fiber axes toward ideal orientations of the type {112)( 110) (common to fiber textures A and B). 3) Finally, grains rotate about their ( 110) axis in the rolling direction, clockwise and counterclockwise from the orientations {112}(110). This produces the range of orientations from (111)(110) to (001)(110) commonly found in the rolling texture of heavily deformed iron (fiber texture A). No significant difference was found between the deformation textures of low-carbon and silicon steels. A few years earlier, Haessner and weik16 had determined (110) pole figures for carbonyl iron rolled to 30, 60, 80, and 90 pct reduction in thickness. heir data agree quite well with the more complete data of Bennewitz, but a somewhat different description of the evolution of the deformation texture was given. The appearance of (110) poles in the transverse direction is ascribed to a (100)[011] component rather than "near {554}( 225) " components, and the (110) fiber axes of fiber texture B are described as located 35 deg rather than 30 deg from the sheet normal. Both of these studies agree that the secondary texture present in heavily rolled iron, the duplex fiber texture B, has (110) fiber axes and not a single ( 111) fiber axis normal to the sheet, as

Jan 1, 1965

By Arthur H. Redfield

In estimating the unmined petroleum reserves of Central America, it is not feasible to employ the methods that have been worked out in thc oil fields of the United States. No producing wells have been brought in and no drilling sections have been made public. It is accordingly necessary to fall back on a crude "barrels per square mile" estimate. The method chosen is a comparison of the structure of the foreign field of unknown reserves with that of some supposedly analogous North American field of which the reserves have been estimated. This method makes no pretense at scientific accuracy, but furnishes a working basis for an estimate. The areal geology of Central America is illustrated in the inap prepared by Sapper and more recently in the geologic map of North America accompanying U. S. Geological Survey Professional Paper No. 71, "Index to the stratigraphy of North America." Disregarding for the present the narrow Quaternary coastal plains and alluvial deposits of the river valleys, three chief zones may be distinguished. These arc: A zone of late eruptive and effusive rocks; a zone of highly folded prr-Cambrian(?) or early Paleozoic crystalline schists and slates, considerably intruded by pre-Tertiary plutonic rocks; and a zone of more or less folded sediments, chiefly of Cretaceous or Tertiary age. The zone of late eruptive and effusive rocks of Central America begins in southeastern Chiapas, Mexico, and extends, with increasing breadth, across southern Guatemala, across practically the whole of El Salvador, and across southern Honduras to the valley of Rio Goascorhn, where the igneous zone attains a width of about 100 mi. (160 km.) East of the Goascordn Valley late eruptives and effusives play a subordinate part, being confined largely to thc Departments of Valle and Choluteca. Dikes and sills of igneous rocks intrude the sedimentary formations of central and northern Honduras. Late igneous rocks cover about four-fifths of the area of Nicaragua. In Costa Rica, late igneous rocks form the diagonal ranges of the Sierra de Guanacaste and the Cordillma Central, and play a part in the upbnild-

Jan 1, 1923

By Arthur H. Redfield

In estimating the unmined petroleum reserves of Central America, it is not feasible to employ the methods that have been worked out in thc oil fields of the United States. No producing wells have been brought in and no drilling sections have been made public. It is accordingly necessary to fall back on a crude "barrels per square mile" estimate. The method chosen is a comparison of the structure of the foreign field of unknown reserves with that of some supposedly analogous North American field of which the reserves have been estimated. This method makes no pretense at scientific accuracy, but furnishes a working basis for an estimate. The areal geology of Central America is illustrated in the inap prepared by Sapper and more recently in the geologic map of North America accompanying U. S. Geological Survey Professional Paper No. 71, "Index to the stratigraphy of North America." Disregarding for the present the narrow Quaternary coastal plains and alluvial deposits of the river valleys, three chief zones may be distinguished. These arc: A zone of late eruptive and effusive rocks; a zone of highly folded prr-Cambrian(?) or early Paleozoic crystalline schists and slates, considerably intruded by pre-Tertiary plutonic rocks; and a zone of more or less folded sediments, chiefly of Cretaceous or Tertiary age. The zone of late eruptive and effusive rocks of Central America begins in southeastern Chiapas, Mexico, and extends, with increasing breadth, across southern Guatemala, across practically the whole of El Salvador, and across southern Honduras to the valley of Rio Goascorhn, where the igneous zone attains a width of about 100 mi. (160 km.) East of the Goascordn Valley late eruptives and effusives play a subordinate part, being confined largely to thc Departments of Valle and Choluteca. Dikes and sills of igneous rocks intrude the sedimentary formations of central and northern Honduras. Late igneous rocks cover about four-fifths of the area of Nicaragua. In Costa Rica, late igneous rocks form the diagonal ranges of the Sierra de Guanacaste and the Cordillma Central, and play a part in the upbnild-

Jan 1, 1923

By A. Lee Barrett

The Maintenance Committee of the Coal Division of the American Institute of Mining and Metallurgical Engineers is presenting with this report the first of a series of cost comparisons which it plans to present the Institute. The plan is to assemble maintenance cost on all equipment connected with mechanical operations at the face of coal mines, to arrange these costs by districts, to make comparisons between districts, and within districts. This particular report covers data with respect to mobile loading machines, including both "on-track" and "off-track" equipment. It is anticipated—in fact, considerable data have already been accumulated—that next year complete maintenance costs by districts can he presented for complete loading units, including the various classes and combinations of on-track and off-track equipment. Data have also been collected with respect to some phases of maintenance methods and certain recommendations of the committee are included dealing with maintenance problems. In the assembly of these data more than 120 questionnaires were sent to operating companies throughout the United States. At the time the report was written 33 questionnaires had been returned with completed information and an additional group of companies had written that the information requested was not at present available but that they hoped to have such information available in the not far distant future. The replies as

Jan 1, 1947

By A. Lee Barrett

The Maintenance Committee of the Coal Division of the American Institute of Mining and Metallurgical Engineers is presenting with this report the first of a series of cost comparisons which it plans to present the Institute. The plan is to assemble maintenance cost on all equipment connected with mechanical operations at the face of coal mines, to arrange these costs by districts, to make comparisons between districts, and within districts. This particular report covers data with respect to mobile loading machines, including both "on-track" and "off-track" equipment. It is anticipated—in fact, considerable data have already been accumulated—that next year complete maintenance costs by districts can he presented for complete loading units, including the various classes and combinations of on-track and off-track equipment. Data have also been collected with respect to some phases of maintenance methods and certain recommendations of the committee are included dealing with maintenance problems. In the assembly of these data more than 120 questionnaires were sent to operating companies throughout the United States. At the time the report was written 33 questionnaires had been returned with completed information and an additional group of companies had written that the information requested was not at present available but that they hoped to have such information available in the not far distant future. The replies as

Jan 1, 1947

By G. P. Boomsliter

IN previous discussions on stresses in hoisting ropes, little has "been said concerning the effect of the elasticity of the rope itself on the stresses due to acceleration. Laschinger1 has calculated acceleration stresses. for several cases but he has ignored the elasticity of the rope as a factor, except as it compresses the drum and stretches itself as it winds thereon. He also deals with steam plants and he shows the effect of the "jerky" start of the engine. This effect would actually be reduced by the elasticity of the cable. With the advent of the motor-driven hoist, new conditions have arisen. The jerk mentioned by Laschinger has been eliminated and smoother starting made possible. But the elastic properties of the rope seem to introduce considerable periodic acceleration stresses in the rope. The following discussion of acceleration stresses is based on the assumption of a constant acceleration at the drum. To be exact, the mathematical work is based upon the assumption that the top is moving upward with a constant acceleration, and ignores the fact that the cable is shortening as it winds. However, the effect of the shortening would be inconsiderable during the first part of the acceleration period. Most hoisting engineers make the assumption of constant acceleration at the drum. Under the older method of calculating acceleration stresses, this would be true with a constant torque motor. But if stresses vary, as this paper attempts to show that they do, constant torque would not give constant acceleration, although the velocity-time curves obtained in the full size test herein described showed that they approach rather closely to this condition, at least as nearly as could be measured.

Jan 2, 1927