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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 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.

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.

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.

BOTH the tractor-semi-trailer and the six-wheel vehicle have the same number of axles and wheels and each has its own particular advantages. They are seldom competitive if the transportation problem is analyzed properly and legislation does not unduly oppress either. The six-wheeler has the advantage over the tractor-semi-trailer of weight saving, more traction if four driving wheels are used, lower insurance rates, and it is free from any “jack-knifing” proclivities. The chief distinction in the construction of six-wheelers depends upon the types of axles used, whether they be dead or driving. There are five classifications in use today, ranging in various combinations all the way from three driving axles to one. The rear bogie unit may have two driving axles or a driving and a trailing axle. There is a natural resistance to turning in a bogie unit since the wheels do not roll tangentially when the vehicle travels around a curve.

UNJUST legislation in the middle of the 19th Century retarded the introduction of road locomotion. The Motor Carrier Act, 1935, calls for extreme regulation, patterned after railroad control. The many differences between the two services prevent like treatment without strangling the virtues and economies of motor transportation. The difficulty of attempting to regulate it is due to the fact that most “fleets” consist of one truck which is owner-operated and only 9 per cent of all trucks are of the For-Hire type. The present predicament of the railroads is due chiefly to general conditions brought about by the depression, the result of over-regulation, and in not keeping in step with the advancement of other industries. The passenger automobile accounts for some loss of revenue, but its use is taken for granted. It therefore seems strange that the other forms of rubber-tired vehicle are not accepted in the march of progress.