MASS production and commercial competition have combined to lend great importance to modifications of motor-vehicle design and so have developed new types of engineers known as tool engineers and production engineers, who take the ideals of automotive engineers and convert them into practicalities, so that the design becomes an ideal manufacturing project that makes it possible to produce a car economically. Special tools are required for many of the machining operations, and for the designing of these the more intelligent and skilled of the workmen are developed into tool-makers for the making of fixtures, jigs, dies, gages, cutters, and punches. Gradually the better tool-makers became tool designers and transferred their work from the bench to the drawing-board, becoming twin brothers of the automotive engineer. Of late, the designing and building of special equipment and allied work have entered into the duties of the tool designer.
NEARLY all steel used in this process of manufacturing frames comes to the plant in the form of strips, which are rolled to remove curvature and inspected automatically for dimensions. All operations and handling are automatic, except pickling, cleaning and oiling the stock and inspecting the assembled frame, until the enameled frame is ready to be shipped. Economical use of the strip steel is dependent upon an offsetting operation that makes the strip conform to the vertical curves desired in the finished frame. With the aid of illustrations, the author follows the fabricating process through the various lines and other units, until a frame is ready for shipment or storage, within less than 2 hr. after it enters the manufacturing line as strip steel.
AN outline is given of the work performed and the method of procedure followed in correlating test results on specimens of heat-treated S.A.E. chromium-vanadium steel 6130 as a basis for revision of the physical-property charts for certain automotive steels. Revision of the charts was proposed by the Iron and Steel Division of the Standards Committee of the Society, and a subcommittee, of which the author is a member, was appointed to carry on the preliminary work of revision. The paper is a report of the results of the tests made. Test specimens of S.A.E. Steel 6130, to be drawn at three different temperatures after quenching, were prepared by four steel manufacturers. These were distributed among 30 cooperating laboratories, which made a series of about 115 tests including complete chemical analysis, tensile-strength, and Brinell, scleroscope and Rockwell hardness tests on the specimens.
MARKED improvement in high-speed high-efficiency engines will be accomplished during the next few years, according to the author. They will have better balance, longer life and greater efficiency, and will develop more power and be more satisfactory to the motoring public. Details of recent developments in this class of engine are given by the author after remarking that the present trend is toward a large number of small changes in design and construction rather than toward radical departures from former design and methods. Mr. Duesenberg comments upon the main features of design of his 91-cu. in. racing-car engine and its parts, and on the troubles that necessitated design changes. The combustion-chamber is stated to be the most important contributor to high efficiency. If the shape of the combustion-chamber, the area of the valves, and the location of the valves and spark-plugs are not right, all the other refinements of detail are of little value.
MOST passenger automobiles are overpowered and probably 80 per cent of such vehicles operate at less than 35 m.p.h. for 90 per cent of the time, according to the author. At 30 m.p.h. an average 3000 to 3500-lb. passenger-car requires from 12 to 15 hp., but the engine carried is capable of developing from 50 to 55 hp. The result is that the car is operated for the greater part of the time at one-third to one-quarter throttle opening. Full power is needed only for accelerating and hill-climbing; during the remainder of the time the excess weight of the engine and other parts must be carried at a loss of efficiency. The author maintains that smaller engines can be used advantageously when equipped with superchargers, the supercharger being used only when excess power is required.
CYLINDER finishing by rough and finish-boring with wide tools, which was thought good enough during the first dozen years of the automobile-production period, was supplanted by reaming and grinding. Later, cast-iron and copper laps were used, but all these methods were slow and did not produce the fine finish for which a demand developed. Experiments were begun about 1920 with the process known as honing. Five years later the company with which the author is connected converted one of its drilling-machines into a single-spindle honing-machine. Other companies made similar conversions. The first honing-head was introduced in 1923. Not until three years ago, however, did honing begin to be regarded as a real production-method possibility. Since then, very rapid progress has been made and numerous improved machines, honing-heads and honing-stones have been produced.
ECONOMIC factors applying to mass production are dealt with in an endeavor to show how, by following certain laws of manufacturing management based on economic laws, the Ford Motor Co. has attained its very low production costs. Some of these laws, which were put into concrete form as recently as 1926 by L. P. Alford, are quoted, and examples of methods are given to show how they operate.
BY means of the gear-correcting process described, spur and helical gears are corrected to give a high degree of uniformity in spacing and profile so that the gears become practically interchangeable. They acquire a “crown face” which enables them to run with unusual quietness under practical conditions. This is essentially an inspection-correction process, as it automatically finds and eliminates the errors. The lap is the important item in the process. It is of chilled cast-iron, gray cast-iron, or type metal, and is made by casting in a mold around a steel chill cut to approximate the gear to be corrected but has a face-width several times that of the gear. The lap, when completed, looks like a wide-faced internal gear.
GROUND teeth for transmission gears are advocated because they can be made to the same degree of accuracy as the other fine working-parts of a motor-car. The designing engineer is held responsible for conditions unfavorable to the adoption of gear grinding by the production department. Mr. Orcutt believes that cluster gears should be avoided because it is impossible to finish them accurately. Fundamental principles of rigid shafts and correct bearing arrangements are laid down, and the degree of accuracy is specified for the fitting parts. Transmission-case design still needs development and study to avoid resonance. Designs are recommended that will provide ample center distance to avoid pinions with a small number of teeth. The unmodified involute is recommended as the most satisfactory form of tooth. Spigot bearings receive special consideration. Two designs of transmission are submitted, in one of which the spigot bearing is eliminated.
PROVISION is made, in the piston and rings described by the author, for an adequate flow of heat from all parts of the piston-head to the cylinder-wall by means of adequate cross-section of aluminum alloy in the head and a tongue-and-groove type of piston-ring structure which provides a greater amount of surface than is usual for heat transfer. A labyrinth oil-seal is provided which aids heat transference and prevents leakage past the piston-rings, and the heat transfer is said to be such that the heat does not destroy the oil seal between the piston and the ring. Charts are included that show the effects in reduced temperatures, oil consumption and gas leakage with the construction described. Attention is given also to a skirt construction most suitable to use with the piston-head and rings described.
IF the costs of almost any group of manufacturers who market the same product are analyzed, two kinds of differences will be detected, according to the author. The real differences in costs arise from superior management, higher productivity, and better disposition and utilization of capital. The accidental differences result from the failure of manufacturers to include in cost records all of the proper legitimate items of expense. Confining his treatment of the subject to an analysis of the depreciation of plant and equipment, the author states that depreciation is a decline in the value which is certain to occur as a result of wear and tear and gradual obsolescence. It is caused by the possession and use of an asset, and is therefore a part of the cost of production. The accountant attempts to recover depreciation loss in the value of the capital assets by charging it into the cost of production.
PRODUCTION of parts in lots, rather than continuously, may sound like a throwback in the automotive industry, but analysis shows that forgings, stampings, body parts and hardware, replacement parts and other parts are made in lots even in large-production manufacturing organizations. Formulas presented by Professor Raymond determine the size of lot that can be manufactured most economically, and show when the change should be made to continuous production. Consideration is given even to such factors as cost of the space for finished stores and return on the investment in finished parts. The lots indicated are not absolute quantities but are designated in the form of economic ranges that are practicable until there is a marked change in sales or other conditions. The formulas can also be applied to help determine the type of handling equipment that will be most economical to use.
CONVEYORS and handling systems often are planned and installed after a building is erected. The Pontiac plant, described in this paper, is an exception because it was designed without limitations as to space and for a definite production program. With the aid of photographs and floor plans on which the positions from which the photographs were taken are indicated, the complete production line of the plant is shown in detail. The order of assembly and the points at which various units are applied to the chassis are shown; also the locations of the storage spaces for many of the parts and the provisions for transporting them to the assembly line. Among the striking features of the chassis-assembly line is a hump, midway of the length of the building, which raises the chassis to the mezzanine level to allow passage underneath.
WE are in a new era of production that has been made possible by the broader vision of the production engineer, who is now an established factor in industry because of the demand for reduced production costs. The two factors over which he has control are labor and machinery. Labor cost is of diminishing significance as machinery takes over an increasing proportion of the responsibility for performance. To the two production principles of the division of labor and the transfer of skill to machinery is added a third principle deduced from facts observed in modern production practice. This principle is integrated production, the combining of work units, which are the smallest possible divisions into which operations are broken down by the time-study man, so that a number of identical or similar operations are performed simultaneously by multiple tools, with the maximum efficiency and economy for each tool or each work unit.
ONE of the standards adopted earliest by the Society is the list of taper fittings. This standard was adopted in 1914, and has been in use ever since with little revision. Saying that the indicated method of dimensioning and stating limits for taper fittings is not practical, at least in some cases, the author suggests various methods for expressing the tolerance in terms of the longitudinal position of a basic diameter. Another point brought out is that the sides of the keyway are not parallel to the taper. In the 2-in. size, for instance, if the bottom of the keyway is made parallel to the extreme element of the taper as it existed before cutting the keyway, the depth at the side is computed to be 0.0318 in. at the large end of the taper and 0.0392 in. at the small end, a variation of 0.0074 in. between the two ends.
AFTER defining the function of transport as the transfer of persons and things from one part of the earth's surface to another in the minimum time and at the minimum cost, and dividing modern transport into human, animal and mechanical, the author proceeds to describe the part played by commercial motor-vehicles in the Country's economic structure. Since food and drink are necessities of life, the first examples of motor-truck transportation discussed include the haulage of milk, bakery products, livestock, produce, vegetables and fruit. These are followed by the use of the motor-truck in local and long-distance general hauling, retail delivery service of dry-goods and chain-store supplies, the oil industry and for the transportation of express matter. A section follows on the use made of this form of transportation by public utilities and municipalities.
AFTER defining the meaning of store-door delivery and outlining its history in Canada, the author reviews in detail the functions of the cartage agent and the railroad company under that system, and gives an idea of the territory and population served. Operation of Canadian store-door delivery is fully described, both as to the terminal facilities and the methods of handling, recording and checking outbound and inbound freight shipments. The author shows that in eastern Canada more than 97 per cent of the carted inbound tonnage is delivered to consignees by the end of the day following its receipt at the railroad sheds. Cartage tariffs used in Canadian store-door delivery are given and the legal situation involved in the operation of cartage service by railroads is outlined.
IN a large plant, especially where the product is diversified, the problem of tool equipment is complex. Great savings can be made by standardization and simplification in small items of tool equipment. Typical examples of drawings and tabulated dimensions for tools and tool parts are given; also a list of some 20 parts that can be standardized to advantage. Without simplification and cooperation from every man connected with tool work, standardization does not bring the desired results.
EXTENSION of motorcoach services over routes of 100 miles or more in length in all parts of the Country is shown by a map, and figures are given of the number of routes, the miles of highway over which the services are operated, running time, rates of fare charged and like data. Facilities and operating methods differentiating long-distance from suburban services are mentioned and the similarity to railroad practice pointed out. A characteristic of routes ranging from several hundred to nearly 1500 miles is that service is afforded continuously for 24 hr. per day seven days per week and many passengers ride day and night. Such long runs are broken into stages so that a driver does not work more than 8 to 10 hr. as a rule and vehicles are changed at the end of a run of a certain distance, which may vary from about 200 to nearly 750 miles.