The early wheels merely rolled, carried weight and resisted side strains; later they were called upon to transmit braking forces and still later the driving force. Prior to the automobile, wire wheels were not called upon to support much weight and the usual type was that used for bicycles. When automobiles were first built, bicycle-type wire-wheels were employed and used until the demand for larger wheels presented unsurmountable obstacles. From that time a development was in progress in this country and in England that resulted in the triple-spoke wire-wheel which has grown in popularity since 1912. The different types of wheels are discussed and the advantages and disadvantages of wire wheels stated; three diagrams are shown. As the wire wheel is a “suspension” wheel, the car weight is hung or “cradled” from scores of resilient, flexible spokes, and the pull is always on three-quarters of the spokes.
It has long been recognized that, in automotive engines, particularly those of six or more cylinders, excessive vibration is apt to occur despite all precautions taken in balancing; and that this is because the engine impulses coincide at certain speeds with the torsional period of the crankshaft, or rate at which it naturally twists and untwists about some point or points as nodes. Very serious vibration occurred in the main engines for the United States submarines S 4 to S 9, which are required to complete five specified non-stop shop tests and an investigation was made of which the author reports the findings in detail, illustrated with photographs and charts.
These experiences relate to the Akron-Boston motor-truck express, established in April, 1917, the Wingfoot Highway Express between Akron and Cleveland which began active operations in January, 1919, and the Goodyear Heights motor omnibuses for passenger service in Akron inaugurated in December, 1917. The preliminary difficulties are reviewed and a mass of specific data regarding construction, operation, maintenance and costs is presented in textual and tabular form, the latter including a summary of pneumatic-tire accomplishment, comparative truck efficiency, an operating summary for six months, the operating cost and efficiency of two 3½-ton twin trucks running on pneumatic and on solid tires respectively, and an operative summary of the Goodyear Heights buses.
Although disc wheels have not been produced in such great quantities as some of the other types, they have advanced far enough in practical application to demonstrate their possibilities and fundamental correctness. Distinction should be made between the wheel itself, the single-taper dished disc and other features such as tire, rim and hub applications. Single-taper dished-disc wheels were developed in France and in this country at about the same time but, on account of the variation in European and American tire practice, the resultant wheels took different forms. The author describes these forms and comments upon them, the argument being favorable to the single-taper disc, and the statement is made that, given the data as to the service expected, the weight and power of the car, the single-disc wheel will compare favorably with any other type, since, when properly designed, the strains are diffused over the entire surface.
A brief outline of the elementary principles of the operation of jump-spark ignition systems is given preliminarily to the discussion of the advantages of battery-type systems, and four vital elements in a jump-spark ignition system are stated. A diagram is shown and explained of an hydraulic analogy, followed by a discussion of oscillating voltage and oscillograms of what occurs in the primary circuit of an ignition system when the secondary is disconnected. The subjects of spark-plug gaps and current values receive considerable attention and similar treatment is accorded magneto speeds and spark polarity, numerous oscillograms accompanying the text. The effects of magneto and of battery ignition on engine power are stated and commented upon and this is followed by a lengthy comparison of battery and magneto ignition, illustrated with charts.
Iron ranks first of all the metals; copper, lead and zinc come fairly close together in tonnage; tin ranks next; and aluminum is fifth of the non-ferrous metals. The place of aluminum in the automotive industry is shown in a diagram and another brings out the production of copper and aluminum, both receiving comment. The metallography of aluminum alloys is discussed in some detail, as well as the phenomena of growth and aging, charts and photomicrographs being shown and commented upon. The effect of alloying on physical properties is treated in a similar manner in considerable detail and a comparison of aluminum with other metals follows. Forging alloys are described and some miscellaneous aluminum-alloy forged parts are pictured. The advantages of forging alloys are enumerated and many of their present uses specified; other contemplated uses for the newest alloy are for cast disc-wheels for passenger cars, differential carriers and cast rear-axle housings.
Kerosene has advanced to the front rank as a fuel for the farm tractor within a decade. A heavily preponderating majority of tractors burn kerosene. The history of early oil engines is reviewed and some comparative costs of kerosene and gasoline fuel for tractors, obtained from tests made in January, 1920, are given. Kerosene tractor-engine development is then discussed. The conditions required for complete combustion are the same in principle for both kerosene and gasoline, but in actual practice a wider latitude in providing ideal conditions is permissible for gasoline than for kerosene. The four classes of commercial liquid fuels usable in internal-combustion engines are the alcohols, the gasolines, the common kerosenes and the low-cost heavy-oil fuels. The alcohols rank lowest in heating value per pound of combustible. Under existing economic conditions neither alcohol nor the fuel oils require consideration as available fuels for the tractor.
The feeling that a truly heavy-duty engine for truck and tractor service was not available led the company represented by the authors to commence the development of an engine that would be capable of high speed as well as have ability to develop maximum horsepower and torque at low or medium speeds. Five specific requirements are stated for a tractor and three for a truck engine; the requirements of a universal truck and tractor engine are then specified under six headings. The special features of design of the engine developed are described in minute detail and illustrated by photographs and charts, seven definite features being mentioned as having been productive of the desired results. The testing apparatus is described and power and torque curves, a timing diagram and capacity curves of the water and oil-pumps are presented. Gasoline was used as fuel, although the engine is designed to use either gasoline or kerosene and is said to be adapted to the use of the heavier fuels.
The author presents the practical side of the body designer's work and refers to him as being between the office and the shop, the one who stands in the way of the impatient man that wants action without preparation. The development of the body designer and body designing is reviewed and the position and duties of the designer are stated at some length. The design factors are considered in detail and the making and utilization of wax models are described, followed by a lengthy consideration of curved-surface bodies, wood body frames, style and body types. The fittings and minor design details are discussed and future designs predicted from present indications. The author explains the body designing business in detail to refute the suspicion that the working methods of body designers are different from those employed by the other members of an engineering force because body designing is different and distinct from the other branches of motor-car engineering work.
The free, resilient, self-expanding, one-piece piston-ring is a product of strictly modern times. It belongs to the internal-combustion engine principally, although it is applicable to steam engines, air-compressors and pumps. Its present high state of perfection has been made possible only by the first-class material now available and the use of machine tools of precision. The author outlines the history of the gradual evolution of the modern piston-ring from the former piston-packing, giving illustrations, shows and comments upon the early types of steam pistons and then discusses piston-ring design. Piston-ring friction, the difficulties of producing rings that fit the cylinder perfectly and the shape of rings necessary to obtain approximately uniform radial pressure against the cylinder wall are considered at some length and illustrated by diagrams.
The purpose of the tests described was to subject various models of truck to shocks far in excess of anything likely to be encountered in actual service, to study the effect of different spring and tire equipment on impact and the effect of unsprung weight upon road impact, as well as the effect of varying speed on these impacts. A series of “jumping tests” for motor trucks was conducted and a new system of motion pictures, capable of being afterward slowed down for analysis, was used to record the results. Trucks were run at speeds of from 15 to 18 m.p.h. along a straightaway course and over a sharp incline. The trucks sprang into the air and struck the ground as from a vertical drop of several feet. The apparatus and the five trucks used are described fully, the data obtained and the method of computing results are presented, and the analysis and conclusions which follow are sufficiently detailed to afford much constructive information on this subject.