Search Results

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.

Two series of tests were made in 1918; one to determine whether the mixture giving best economy and that giving maximum power is a constant quality for all conditions of speed and power output; the other to ascertain what effect changes in the temperature of the fuel-intake system have on the quality of the mixture which gives the maximum power and that which gives best economy. The standard United States ambulance four-cylinder engine was used for these tests, its carbureter having a primary air passage, a primary fuel-jet, an auxiliary air passage with an air-valve and a secondary fuel-jet, the manifold being cast integrally with the cylinder block and a curved riser conducting the fuel mixture from the carbureter to it. The testing methods and fuel consumption measurements are described.

The paper relates to some of the methods and apparatus which can be used to advantage in large-scale farming operations. The laying out of a production program, the transportation of men and supplies, special implements for raw-land preparation, tractor dynamometers, large tractors, special plowing and tilling implements, four-wheel-drive tractors and road haulage are discussed. An operation chart applying to an area of 40,000 acres is first presented and analyzed. Regarding hours of operation, the author maintains that with a suitable organization and proper selection of motive power and implements, tractors can be kept in motion 20 hr. per day and gives a time-table. Consideration is then given in some detail to the problems of electric lighting, the implements used in raw-land preparation, the power required for various operations, types of tractor construction, plowing and harrowing, harvesting, hauling and tractor-train schedules, the whole being copiously illustrated.

Continued lowering in the grade of fuel obtainable compels automotive engineers to produce engines that will utilize it with maximum economy. The manufacture of Pacific coast engine-distillate with an initial-distillation point of about 240 and an end-point of 480 deg. fahr. was abandoned by the principal oil companies early in 1920. Utilizing this fuel efficiently through its period of declining values forced advance solution of some fuel problems prior to a general lowering of grade of all automotive fuels.

The undisputed economy of the Diesel-type engine using heavy fuel oil is recognized, as no other power-generating unit of today shows better thermal efficiency. It is the result of the direct application of fuel in working cylinders. Transmission processes, such as the burning of fuel under a boiler to produce a working agent which must be carried to the prime mover, are less economical. The various factors which enter into a comparison between steam and heavy-oil installations are illustrated. The subject is treated in a more or less elementary manner. The diagrams and sketches are intended to explain the working principles of such examples of two and four-cycle engines as are now in actual operation in cargo ships, these being of the single-acting type. Double-acting and opposed-piston-type engines have been built and are being tried out. The working processes of two-cycle and four-cycle engines are illustrated and described in some detail, inclusive of critical comment.

Emphasizing the necessity of persuading fuel manufacturers to improve the suitability of internal-combustion engine fuel by the mixture of other materials with petroleum distillates, and realizing that efficiency is also dependent upon improved engine design, the author then states that results easily obtainable in the simplest forms of automotive engine when using fuel volatile at fairly low temperatures, must be considered in working out a future automotive fuel policy. The alternatives to this as they appear in the light of present knowledge are then stated, including design considerations. The principles that should be followed to obtain as good results as possible with heavy fuel in the conventional type of engine are then described. These include considerations of valve-timing and fuel distribution. Valve-timing should assist correct distribution, especially at the lower engine speeds.

THIS paper describes the various types of radiator installations in use. Tabulated data on several makes of radiation and on successful airplane radiator installations are given. A brief review of laboratory tests is made and the features to be considered in design and manufacture are discussed. The author concludes by cautioning engineers against attempting to base new designs entirely upon experimental data, without comparing the tentative design with existing successful installations.

THE ever-increasing demand for highly volatile fuels and constantly decreasing volatility, constitute a serious problem. Synthetic fuels have been suggested as a remedy, but these require a change in carburetion methods. It is the author's conviction that, if any redesigning is necessary, this should embody a combustion method by which any of the existing liquid hydrocarbons can be utilized and further change of method obviated, if a new fuel should later be developed. The high-compression engine is presented as a solution. Proof is offered that by its adoption any liquid hydrocarbon fuel can be utilized under any temperature condition and a real saving in fuel accomplished through increased thermal efficiency. Sustained effort should be made along these lines to increase thermal efficiency and provide an engine of adequate power, flexibility, ease of control and ability to operate on any of the fuels obtainable now or later.

IN the cooling system for an automobile engine, the water-jacket must be designed to give ample capacity and free flow of the water. It is essential that water-pump capacities and speeds be figured to equal the radiator capacity so as not to retard the flow of water through the radiator and cause hot water to back up into the cylinder; the radiator must always be kept full and still handle the water as fast as the pump carries it. Fan locations are necessarily considered with relation to the radiator and radiator shroud. Fan diameters, blade path and fan speeds should be given thought, in order that the proper volume of air can be handled to carry heat from the engine. The frontal area of the radiator core in square feet per horsepower developed by the engine and several other details which can be worked out by the fan and radiator manufacturers should receive attention. The best possible fan bearings must be used, giving special attention to radial and thrust loads, fan speeds, etc.

The paper treats the subject of ability from the point of view of its relation to the present trend in motor-truck design, setting forth some of the fundamental considerations involved. An ability formula when applied to automotive vehicles is to determine a “factor of experience” from which engine sizes and gear ratios can be calculated. While passenger-car performance is measured in terms of speed and acceleration, the latter are not the most important considerations in motor trucks, the speed of which is limited by the use of a governor. Wind resistance also is negligible at truck speeds. Practically the only resistances to be overcome by a motor truck are road friction and the force of gravity. Both road and grade resistance are in direct proportion to weight carried and are usually expressed in terms of pounds per pound.

SOME practical examples of correct as well as of incorrect methods of designing are studied, using a motor vehicle for illustration. The mechanism of such a vehicle should be very simple, and the elimination of certain links and members here and there may become more or less desirable. It is essential to know how much this will burden other members, and what strengthening or even redesigning may become necessary. It has been proposed to eliminate the torque and radius-rods. By formulas and drawings the author shows how complex the problem is and the various changes that must follow such an attempt. A vehicle must have much stiffer springs if the torque rod is to be eliminated. This inevitably leads to a study of springs and of the influences of brakes. A vehicle can be operated at somewhat higher speed with a torque-rod.

THE design of a modification of the Class B Government standardized truck engine is presented, the principal object being a saving in weight without sacrificing either durability or safety factors. The crankcase design is rigid, but the metal is distributed so that the weight will be a minimum. The crankshafts are made of chrome-nickel steel of an elastic limit of 120,000 lb. per sq. in., which further carries out the idea of durability with low weight. The connecting-rod length is slightly more than twice that of the stroke, and this, with light-weight pistons, obviates vibration, without adding weight to the engine on account of increased cylinder height. The flywheel and bell-housing diameters were selected with a view to securing enough flywheel weight for smooth running without increasing the engine weight materially. All-steel supports reduce breakage of arms to a minimum. The manifolds are carefully designed to give economical performance, even with low-grade fuels.

EVERY plow in use should have 10 b.-hp. available. Every tractor engine should deliver continuously at least 33 hp. If the 330-cu. in. engine mentioned were as good as a Liberty airplane engine, it could deliver 57 hp. at 1000 r.p.m. The horsepower actually obtained is as follows: 41.5 in the laboratory 33.0 at the factory 29.0 when burning gasoline 23.0 when burning kerosene 21.0 with poor piston-rings 19.0 with poor spark-plugs 9.5 available at the drawbar The great engineering problem of the future lies between the 57 and the 23 hp. From 19 to 9.5 hp. is the manufacturer's problem. The main difficulties, as outlined by the figures given, lie in the combustion chamber and its ability to dissipate the surplus heat, and in the limitations of fuel. There will be no need for refiners to continue to break up the heavier fuels by processes already so successful, if by ingenuity and good understanding of thermodynamics these can be made to burn in present-day engines.

THE oil engines described are for stationary or land installations and are of the “hot-surface” design with combustion at constant volume. Progress in the design is referred to and the thermal efficiency of modern designs is compared with that found in engines twenty-five years ago. Three important features are reviewed, namely: (a) Reliability, (b) first cost and (c) economy. Improvements in the design of spraying devices, and other details of construction which have brought about greater reliability, are referred to. Dimensions of large two and four-cycle oil engines are given, and the first costs of each type are contrasted. The greater economy of the modern oil engine as compared with the earlier type is explained. Indicator cards, test data, speed, weights and other details of interest are enumerated concerning the De La Vergne SI type of oil engine, this being an example of the results obtained in a modern hot-surface-type oil engine.

BRAKE trouble is often only faulty brake-rod location. In the Hotchkiss drive unless the rear brake-rod center is located on the transverse axis, about which all rear-axle torque takes place, and the front brake-rod center lies on the axis which most closely approximates the center of the curve along which the torque axis moves relative to the frame, faulty brake action will result. The most effective way to locate a brake-rod is by a gage, two applications of which are shown in the figures, one to correct front center height and the other to correct the length of rod. The gage consists of graduated rods which, together with a dial indicator, are put in the place of the brake-rod and held by special clamps. The axle and springs are put through approximately normal action independently, and any tendency of the rod to elongate or shorten is indicated on the dial. The figures show how, for various points, such changes in length might take place.

Few points have aroused such discussion among users and engineers as that of the desirable number of cylinders in an engine. A large part of the work of the author has been in the direction of attaining the same ends as those achieved by the multi-cylinder engine but by different means. He discusses the relations between torque at clutch and number of cylinders and multicylinder engines and uniform torque, the factors governing torque recoil, torque recoil as a function of car weight and engine balance. His conclusion is that the multi-cylinder engine now so widely used exceeds the real requirements and obtains its smoothness of operation at the expense of more desirable qualities. A reduction in car weight would in his opinion enable existing standards of performance to be maintained and even improved by the use of four cylinders for the heavier type, with all that this means in tremendous advantages to the automotive industry and to the user.

A new type of automotive engine should be the quest of all designing engineers. Investigation has revealed the fact that 68 per cent of all tractor engine troubles occur in magnetos, spark-plugs and carbureters, the accessories of the present-day automotive engine. Four-fifths of the fuel energy supplied is regularly wasted, yet the fuel is a liquid meeting severe requirements of volatility, etc., and is already becoming scarce and costly. In an airplane, fuel is carried by engine power. In ocean-going cargo vessels it increases available revenue space. It is at once clear that for purely practical reasons the question of fuel economy, no less than the question of the nature of the fuel, becomes momentous. What fuel will do is entirely a question of what process it is put through in the engine; in what way combustion is turned into power.

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.

Efficiency, appearance and comfort will be the catchwords of the car of the future. Extreme simplicity of chassis will be needed to reduce weight and permit the use of substantial sheet-metal fenders, mud-guards and bodies. The center of gravity should be as low as possible consistent with good appearance. For comfort the width and angle of seats will be studied more carefully and the doors will be wider. A new type of spring suspension is coming to the fore, known as the three-point cantilever. Cars adopting it will have a certain wheelbase and a longer spring base. A car equipped with this new mechanism has been driven at 60 m.p.h. in safety and comfort without the use of shock absorbers or snubbers. It is the opinion of the author that this new spring suspension will revolutionize passenger-car construction.