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STARTING with the Sturtevant in 1904, transmission developments are reviewed to date. Requirements for successful and satisfactory automatic transmissions are discussed and interpreted in the light of present and future development. Six tables that classify transmissions comprise the nucleus of this part. These tables group the methods of varying the speed; the means of control; the gear engagement or connection; the shifting methods; clutches; and clutch control. THE story of over two million miles of operating experience using the “Mono-Drive” type of automatic transmission on 101 passenger buses in Chicago, is told in the second part of the paper. The mechanical operation of this automatic transmission is explained, and specifications and data are given on the buses in which they are used. A review of the maintenance record of the transmissions concludes the paper.

GENERAL DESIGN and detail mechanical developments that have been made in the last year and incorporated in automobile, truck and motorcoach models for 1932 are reviewed by the author, who also points out noticeable trends in a number of directions. He deals in order with the cars as a whole and with each major component, from the powerplant to the tires and body, as found in many leading makes. Decision of the industry not to announce the details of new models until the end of the year, at or immediately before the opening of the New York Automobile Show in January, interfered with the presentation at this time of a complete picture of all the improvements made in American motor-vehicles, but enough information is believed to be given to show the more important developments and the ways in which the automotive engineers have responded to the desire of the times for greater refinement and efficiency in automobiles.

DEPENDING upon the location of the front wheel, the door and step are placed either at the front or back of the cab. Some designs incorporate a protruding “hood” portion, whereas others extend the cab fully forward. The engine compartment is either immediately back of the radiator or under the cross seat. The floor and seat heights are relatively higher than in the conventional truck, and better visibility is obtained. The engine hood is well insulated for heat and sometimes for sound as well. Most powerplants are removable readily for major repairs although, in most instances, major maintenance operations can be done readily within the cab. Front axle treads have been increased in order to give greater stability on the road as well as to avoid an excessively large wheelhouse. The change in weight distribution has called for considerably more study on braking distribution.

THE introduction of the oil filter into the lubricating system of internal-combustion engines marked a distinct advancement, Mr. Wolf states. However, he adds, due to the varying combination of working conditions, the operator who dreams that all lubrication problems are eliminated by the use of oil filters is due for a rude awakening. He continues to remark that any valuable tool can be abused if full cognizance is not taken of its possible shortcomings, and he enumerates those of the filter to form a basis of a true appraisal of its intrinsic worth. Mr. Wolf notes that conflicting opinions are heard regarding filters due to the widely different circumstances under which identical equipment is operated. In stop-and-start operations, light delivery trucks and some passenger cars never have the engine warm enough in extremely cold weather to permit functioning of the filter, he points out.

DEVOTED to the mechanism of free-wheeling devices, this paper contains detailed descriptions of the devices now in use on American cars and a résumé of the experiences of the Studebaker Corp., which pioneered the device in this Country, and other prominent manufacturers, showing how present designs of roller clutch have evolved from those first developed, in which several rollers of graduated sizes were used in each pocket. Lubrication of free-wheeling transmissions is discussed. Coil-spring clutches and one English design in which frictional contact is obtained through wedge-shaped shoes are also described. The author concludes with the suggestion of a combination unit to include free-wheeling, service brake and sprag.

THE auxiliary transmission and the 2-speed axle are not in direct competition as methods of obtaining multiratio gearing for, as Mr. Wolf points out, neither can fill the field of the other. Where their reduction ratios overlap, Mr. Wolf says that the 2-speed axle is more economical in first cost and can give speedier performance at a lower operating cost. On the other hand, he shows that when larger reductions are required than the 2-speed axle can provide or where three ratios are needed, the auxiliary transmission is without a peer. In general, he says that the type of multiratio gearing that should be used and in what combination depends on the type of truck operation and the degree of economy the operator will obtain from the additional investment.

FULL cognizance of the fact that the power-weight ratio of a vehicle is the fundamental factor which no trick or gadget can possibly circumvent, was brought about by the formulation of the SAE Truck Ability Rating, Mr. Wolf reminds. A better power-weight ratio can be accomplished, he explains, by three expedients, singly or collectively, these being: increasing the power of the engine; conserving the power developed; and reducing the weight of any of the components making up the gross vehicle weight. Past and present practices covering the ratio of chassis weight to gross vehicle weight for 1935 and 1940 are analyzed in this paper; also horsepower to gross vehicle weight for 1931, 1935, and 1940. Some typical truck models are scrutinized for specification and design trends over the past ten years or more, emphasizing the horsepower and torque per pound of chassis weight, as well as the gross vehicle weight per pound-foot engine torque.

THE TRACTIVE ability of a motor-vehicle, as stated by the author, is the measure of its power to overcome outside resistances to its translation, based on the tangential force exerted by the driving wheels at their points of contact with the road. The propelling force is derived from the engine. To compute the “tangential force” of the foregoing definition it is engine torque that interests us rather than the horsepower, he states. If the horsepower is given, it can be converted into torque. After analyzing this point mathematically, the author discusses typical tractive-factors of modern motor-trucks so that he is enabled to develop an economic factor mathematically and thus be prepared to discuss tractive resistance as opposed to tractive effort. Air resistance is considered in detail as a particularly important factor concerning motorcoaches, and the author's points are backed up by diagrams and charts as well as by numerous tables of statistical and computed data.