Search Results

The comparatively slow introduction of mechanical power for farm operations has been a surprise and a disappointment to many. It is easily understandable why the deficient machines failed to sell but not so clear why really efficient outfits failed to make greater headway. No one can make a thorough study of the existing situation and conclude that any or all of the reasons given are even in a large part responsible for the slowness in adopting the tractor more generally on the farms; it is obvious that there are other strong influences. Most of these are connected with the farm business itself and, by considering the matter in relation to the individual farmer rather than farmers as a class, these influences become more clear.

In investigating the forces that tend to break up and destroy roads, the most destructive of these being that of impact, the United States Bureau of Public Roads devised a method of receiving the impact of a truck on a small copper cylinder and determining its amount by measuring the deformation of the cylinder. The impact values are largely dependent upon the type and construction of the truck. Unsprung weights have a great influence upon the impact value of the blow on the road surface and a reverse influence upon the body of the truck; these effects are in two different directions. The present aim of the Bureau is to investigate this impact and the effect of the unsprung weight on the road. Most of the tests have been made on solid tires, a few have been made on worn solid tires and some on pneumatic tires. The Bureau intends to elaborate all of these tests, including different types of pneumatic tire, different unsprung weights and special wheels, such as cushion or spring wheels.

The farm tractor is finding itself among the most essential of mechanical agricultural devices; the industry is young, and controlling basic factors of design are not yet completely crystallized, nor has research had its proper share in the development. Some further factors of the author's earlier article on tractor plowing speeds2 are discussed in this paper. The earlier article dealt chiefly with plowing data on the assumption that there was delivered at the drawbar of the tractor a constant horsepower. This paper starts with a normal condition of a constant engine power which is to be delivered to the crankshaft under governor control for any of the travel speeds analyzed. The tractor is considered as powered by a given brake-horsepower engine, this power being transmitted through sets of gears in which the net bearing and gear efficiency is taken to be 73 per cent.

THE objects to be obtained in testing tractors are listed, but field testing only is dealt with. Regardless of the attempt of the Society of Automotive Engineers to standardize the practice of drawbar horsepower rating of tractors, the practice followed by the industry is anything but uniform. Drawbar horsepower actually developed in tests at the 1918 National Power-Farming Demonstration, varied from 50 to 200 per cent of the rating. The need of more than 25 per cent reserve, as provided by S. A. E. Standard Practice, is argued. Drawbar pull is suggested as an important part of the rating. Rating of tractors by the number of plows pulled will not be satisfactory, owing to wide variation in soil conditions. To make satisfactory tests an accurate dynamometer is required. The Hyatt and Iowa instruments are described. The importance of care in making tests is emphasized. In the discussion, the Gulley and Giddings recording dynamometers are described.

THE rapid development of heavy-duty trucks and farm tractors has made it necessary for manufacturers of engines used in such automotive apparatus to face problems regarding which there is no past experience to fall back upon. The necessity in both types of engine for maximum strength in all parts carrying excessive loads constitutes a problem of great importance, but in addition to it are others of the proper utilization of fuels at present available, lubrication under excessive load conditions over long periods of time; and, of nearly as much importance, the relation of fuels to lubricants and the effect of fuels upon lubricants. Moreover, information is to be acquired regarding the value of prospective fuels as power producers, the effects they have upon engines, lubricants, etc., comparisons of cost and the like. The tests recorded in the paper were made in an endeavor to ascertain some of these unknown values.

THE author believes a more thorough understanding of the functions and use of drawbar implements is necessary. The tractor is incidental to agriculture. The implements used with tractors do the actual work and the tractor is a means to that end. Many tractors are sold on the quality of work done by the implements, and not because of their own work. Many a tractor is condemned because the implement combination is not correct. The amount of draft of plows must be thoroughly understood. Good plowing requires considerably more power than poor plowing, although done at the same depth and width. Turning the same number of square inches of furrow section will in one case require from 20 to 30 per cent more power than in another.

The author considers the adaptation of farming implements to the farm tractor the most important engineering problem confronting tractor manufacturers. The problems are intricate in their ramifications, all-inclusive in their scope and fundamental. They can never be solved by theoretical discussion and laboratory tests alone. Extensive field experiments are needed with the machines operated by the farmers themselves. It is the implement which does the work. The mold-board plow and the disk harrow are standard for soil preparation; the oscillating sickle, the reel and the knotter-head for harvesting; the revolving toothed cylinder and the oscillating rack for threshing. Power must be transmitted to these fundamental devices. The automotive tractor fills a place in the farm power field not successfully covered heretofore by any single prime mover.

In the past the majority of trucks have been equipped with wood wheels. These gave good service, but the results demanded under strenuous modern conditions seem, the author states, to make the substitution of steel wheels on medium and heavy-duty trucks imperative. Truck engineers and builders seem to recognize the fact, but to hesitate to make the change, chiefly because a metal wheel is somewhat higher in first cost and because some designs have not as yet rendered the service expected of them. The service return of metal wheels is given from the records and reports of the London General Omnibus Co. and the Fifth Avenue Coach Co., both of which use steel wheels exclusively. The added mileage is in excess of wood-wheel service and exceptional tire mileage is shown. The author states briefly the arguments for the hollow-spoke, hollow-rim, the hollow full-flaring spoke and the integral-hub metal wheels.

Whatever may be the conclusion of business men and engineers as to the fuel problem, dealing with it from the point of view of the engineer as a service man nothing further is needed than that the problem is before us. The paper deals with engine troubles that have been found to demand the greatest amount of attention from farmers. Tractors are not built for or operated by engineers. No quantity production is likely to be attained for some time to come with anything but the commonest forms of cylinder and other features. This judgment is based entirely on the limitations in upkeep knowledge of the average user. The four-cylinder tractor engine seems to be rapidly becoming standard, due to its simplicity and the familiarity of most farmers with this type. Consideration is given, topic by topic, to important parts of the tractor engine and the relation of fuel to difficulties discussed.

THE United States was practically unprepared in the field of military motor-transport at the beginning of the war. Due largely to the cooperation of the Society of Automotive Engineers and its members individually, this handicap was overcome and a position stronger in this respect than that of any of the other belligerents was attained. The early efforts and the cooperation between the Society and the various Government departments are described, especially with reference to the Quartermaster Corps which at that time had charge of all motor transportation. Regarding the Class B truck, it is shown that the Society acted as a point of contact between the various members of the industry and the War Department and, although not fostering any program or plan of its own, it was largely responsible for the success of the standardization program conceived and carried out by the Army.

The authors advance for discussion some important problems in the construction of airplanes for military use in this country. The functions of military airplanes designed for strategical and tactical reconnaissance, control of artillery fire and for pursuit are outlined. Problems in construction with reference to the two-propeller system, methods of reducing vibration, application of starting motors, details of the gasoline supply-system, metal construction for airplanes, flexible piping, desirable characteristics of mufflers, shock absorbers, landing gear, fire safety-devices, control of cooling-water temperature, variable camber wings, variable pitch propellers and propeller stresses, are all given consideration. The paper is concluded with suggestions for improvement in design relating to the use of bearing shims, the rigidity of crankcase castings, interchangeability of parts and better detail construction in the oiling, ignition, fuel supply and cooling systems.

It is the purpose of the author to analyze some of the factors that have influenced tractor development. He reviews a number of factors on which the usefulness of tractors depends, showing what the farmer is interested in when buying tractors and how the design should be worked out to secure the greatest general efficiency. The paper then mentions certain general specifications that are required by tractor engines. The author finds that the conditions on about 90 per cent of all farms require a four-cylinder engine of between 16 and 40 hp., operating on the four-stroke cycle. The disadvantages of the two-cylinder horizontal-opposed engine are summarized. An empirical formula is given that can be used to calculate the most satisfactory operating speed of an engine. In concluding the paper a number of the most important general themes of design are outlined. Particular mention is made of the lubrication system and of the special provisions required for kerosene burning engines.