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Technical Paper

Duralumin All-Metal Airplane Construction

1928-01-01
280030
PSYCHOLOGY of the public, as well as engineering structure and aerodynamics, is involved in commercial aviation. The public has confidence in metal. With quantity production in view, the author and his associates considered costs of production as related to quantity and also costs of maintenance at airports and in the field, and chose metal as the material of construction. Structural members are fashioned from sheet duralumin rather than from tubes and a type of construction was evolved that can be made with the minimum investment in tools, that is cheap to put together and that can be repaired with the smallest amount of equipment and labor. For compression loads, duralumin has a great deal more strength for a given weight than has steel. It cannot be used, however, for compression members in combination with steel in tension members because of the difference in coefficient of expansion.
Technical Paper

Methods of Building Metal Airplane Structures

1928-01-01
280029
USEFUL load-carrying capacity is a measure of the comparative value of two airplanes of the same size, having identical powerplants, speed, rate of climb and other flying characteristics. It seems to be feasible to combine in the same airplane both the greatest ability to carry useful load and the least cost of construction. Blanked and pressed metal work offers substantial advantage to the extent that parts, particularly sub-assemblies, can be made directly by machine in complete units ready to set in the final assembly. The author shows and describes the methods followed by his organization in forming the members, building the frames and assembling the units of metal aircraft. Trusses are blanked and the web members pressed to ¾-circle form. Dies for long members are variable in length by being made in pieces that can be removed or inserted as desired. Flanged-tube sections are employed for truss chords.
Technical Paper

The Automatic Fabrication of Automobile Frames

1928-01-01
280021
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.
Technical Paper

Progress in Honing-Machines and the Honing Process

1928-01-01
280060
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.
Technical Paper

Material Handling in the Pontiac Assembly Plant

1929-01-01
290072
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.
Technical Paper

Integrated Production

1927-01-01
270053
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.
Technical Paper

Measurement of Taper Fittings

1927-01-01
270056
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.
Technical Paper

Quieter Gears Are Being Demanded! How Shall We Make Them?

1933-01-01
330019
LIMITATIONS of present processes for cutting and finishing transmission gears are covered in a general way by Mr. Cederleaf. He shows also that future demands for more quiet transmissions can be met only by an equal improvement in gear-cutting-and-finishing equipment; or by the development of new processes; or by the realization, on the part of engineers, that the most economical method of obtaining better results is, by redesign, to eliminate from the transmission the necessity for greater dimensional accuracy.
Technical Paper

SOME PRINCIPLES OF LOW-COST TOOLING

1933-01-01
330013
After predicting that the demand for changes in automotive products and the substitution of new devices will increase in the next few years and stating major factors with which managements are concerned at present, the author mentions that, after direct-labor costs, the next largest items of expense in a machine shop are generally depreciation and obsolescence of machines, fixtures and tools, especially when a plant is tooled for high production. He believes that the machine-tool industry might aid by reducing its prices and that this can be done, but that in such case the industry must eliminate its present cast-iron type of designing and many of its present manufacturing methods. General machine-shop practice is analyzed and the illustrations show three classes of fixtures: (a) holding, (b) self-contained tools with holding means and (c) complete mechanisms.
Technical Paper

Future Clutch Progress Charted from Design A-B-C's

1933-01-01
330011
FIRST consideration is given by the author to basic improvements in clutches of the lever-release single-plate and to those of the two-plate types. He emphasizes that the severity of clutch service has increased very materially in the last few years and that the increased clutch duty of today is further augmented by the car manufacturer in providing cars having greater acceleration and higher torque, particularly at the higher speeds and usually without a proportionate increase in clutch size. Developments along logical lines which have resulted in improvements in design are cited as being (a) the design of the driven disc and the selection of facings, to produce improved engagement and greater life; (b) design of the cover-plate assembly to permit higher spring pressure with less retracting movement of the pressure plate; and better selection of facing and pressure-plate materials to reduce facing wear and pressure-plate distortion or scoring.
Technical Paper

Cageless Roller Bearings Develop High Carrying Capacities

1933-01-01
330047
A ROLLER having the same diameter as a corresponding ball and a length equal to the ball diameter has approximately four times the carrying capacity of a ball, according to Mr. Hermann. The data presented on cageless roller bearings are based upon knowledge of the carrying capacity and life of the ball bearing. The reason for the increased carrying capacity of a roller over that of a ball is due to the distribution of the load over a line of contact rather than at a point of contact. The roller bearing increases the number of such line contacts and therefore further distributes the load to the raceways. By increasing the number of line contacts, the cageless rollers reduce the stress per roller and failure due to fatigue. The fatigue factor is reduced 40 per cent, comparing a cageless with a caged roller.
Technical Paper

An Analysis of Tires and Wheels as Causes of “Tramp”

1933-01-01
330042
THIS paper presents the solution of the factors in tires and wheels that cause a particular type of front-end vibration termed “tramp,” which is a vertical vibration of the front axle accompanied by a small degree of simultaneous oscillation of the wheel assembly about the king pin. This vibration in turn sets up the disturbance of the body and chassis. The front-axle vibration is caused by the unbalance and variation in rolling radius of the rotating front-wheel assemblies. The theoretical action of these two factors is developed in detail and supported by experimental results. The foregoing two factors act independently. The resultant of the two periodic forces which they set up depends on their phase relationship.
Technical Paper

Brake-Drum Metallurgy

1932-01-01
320006
EITHER steel or cast iron will provide a good braking surface provided the grain structure is laminated pearlite, according to the author. Such a structure can be secured in pressed steel by alloying or by case-hardening, in high-carbon steel rings welded to a stamped back and in centrifugally cast iron by careful control without alloying. Uniformity of analysis is important and control of the rate of cooling is still more important in castings. The graphite content of iron is not considered important as a lubricant. Methods of centrifugal casting and of testing are illustrated; also the form and microstructure of representative brake-drums. Discussers agree as to the microstructure needed and present additional views as to ways of securing that structure and the desirability of capacity for absorbing and dissipating heat. They believe grain size and strength more important than hardness.
Technical Paper

Welding in All-Steel Body Production

1932-01-01
320041
ALL-STEEL welded bodies for passenger-cars have many advantages over composite bodies, among them being fewer parts, doors of only two pieces, no visible outside seams, lower tops for the same headroom, less roof weight, lower center of gravity, greater safety, increased visibility, permanent quiet, economical upkeep and perfect outside lines. Wood and steel react so differently to stress that neither adds much to the strength of the other in a composite structure. Steel alone, welded into a unit structure, is lighter and less bulky. The entire side of the body is stamped from a single sheet, with the openings die formed to reenforce it. Chassis frame and body follow the same lines, so that they reenforce each other and body sills can be omitted. This plan saves 2 in. in height, as compared with some other bodies.
Technical Paper

Production Standards Applied to Motor-Vehicle Maintenance

1930-01-01
300045
MAINTENANCE is a part of automotive production and as such is destined to adopt production standards. While passenger-car manufacturers have fostered the application of these standards to maintain a parity between factory production and maintenance, commercial-vehicle operators have established standards and methods in response to an economic demand to obtain low-cost maintenance. How this has been done in Philadelphia is the subject of the paper. Scheduling vehicles through the shop in accordance with the seasonal requirements of transportation enables a centralized shop having 120,000 sq. ft. of floor space to service a fleet of 450 motorcoaches, 1500 taxicabs and approximately 150 pieces of various utility equipment with practically no fluctuations in the working force and the minimum number of spare units. Major overhauling of motorcoaches is done in the winter months when the demand is relatively light, while the taxicabs receive attention in the summer.
Technical Paper

Casting Cylinders in Green Sand

1930-01-01
300039
CYLINDER-BLOCKS, with their hollow form and complicated arrangement of water-jackets, valve passages, pockets and bearings, are difficult to cast, and require a large quantity of cores. These have generally been baked or dry-sand cores, but the author's organization has met with success in making the more bulky cores, those for the cylinder-barrels and crankcase, in green sand. Descriptions and copious photographs and drawings are given of two methods of molding one six-cylinder block in green sand, and the possibilities of the system are indicated by illustrations of cylinders and details of cylinders that have been molded or that are suitable for molding in green sand. Cooperation between designer and foundryman is essential in realizing the economy possible with this method of molding, a large part of which results from the great saving in cost of sand.
Technical Paper

New Developments in Machining Aluminum and Its Alloys

1930-01-01
300040
COMPARATIVELY large rake and clear angles required for best results leave a relatively thin cutting-edge on a cutting tool for aluminum. One difficulty encountered is that tools of such form are not always available or suitable, for various reasons, for instance, small tools of various types are available only with cutting edges suitable for steel and bronze, and the desirable amount of top rake cannot well be provided on circular form-tools. Tool bits of various sorts can be reground to the desired angle. A simple round form of tip that is shown can be utilized in tools for various purposes, including use as inserted teeth in a face-milling cutter. High-speed-steel tools are suitable for most aluminum alloys, but alloys containing a high percentage of silicon can be machined to advantage only by using cemented tungsten-carbide. Machine-tools should be suitable for high speed.
Technical Paper

Recent Developments in Poppet Valves

1931-01-01
310007
AFTER stating that increased speed, mean effective pressure and piston displacement of engines have made valve conditions more difficult during the last few years, the author recalls the path which development has followed by a brief list of materials and methods of cooling. Where the stem joins the head is the hottest part of the valve. A shield for this point is shown, also a shroud to protect the end of the valve-stem guide. Cooling the valve increases its life. Salt and sodium cooling are compared, and methods of sealing the coolant in place are described. The construction and behavior of copper-cooled valves are illustrated and recounted, and a one-piece hollow-head valve is described. Reasons for valve-seat inserts are given.
Technical Paper

The Field for Synthetic Lubricating Oils

1931-01-01
310033
ONE method employed in a fundamental investigation of the composition of lubricating oils as it affects the viscosity characteristics has involved the synthesis of viscous oils by polymerizing a wide range of olefins with a condensing agent, such as aluminum chloride. Many thousand gallons of synthetic lubricating oils have been made within the last two or three years from olefins produced by cracking paraffin waxes. Details of the process have been published previously and hence are not included. The present paper deals with the characteristics of two such oils that have been synthesized in commercial quantities. The raw materials and the process of manufacture make these more expensive than ordinary motor oils, but their temperature-viscosity characteristics make them desirable for use in transmission and steering mechanisms and in hydraulic shock-absorbers, as they are less susceptible than the usual oil to viscosity changes with changes of temperature.
Technical Paper

Weight Saving by Structural Efficiency

1931-01-01
310034
METHODS employed by the author to reduce the weight of the structural frame without sacrificing strength are described in the paper. To obtain this result the best available cross-section must be selected and the members arranged to transmit the load directly to the final supports which should lie approximately in a plane that is parallel to the load vector; also where a bending moment is caused by the loading, the support attachment should produce a moment of the same amount and of opposite sign. Avoiding secondary bending and utilizing the advantages of full continuity over supports can be secured by a simple arrangement of the frame members. Substitution of power tools for hand tools will effect a reduction in assembly costs. Sections suitable for power assembly include closed hollow-sections, which have a high structural efficiency, as well as angles, channels, I-beams and similar shapes.
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