Variable Gear Research Articles

Historical Fish Assemblage Flux in the Cheyenne River below Angostura Dam

ABSTRACT Dams on rivers alter hydrology and geomorphology downstream, which often affect fish assemblage composition. Such was the case on the Upper Cheyenne River below Angostura Dam. Fish species composition varied dramatically among sampling periods, including pre-dam (1892 to 1893), immediate post-dam (1949 to 1952), and recent (post-1995) collections. Of 25 fish species that were collected, only the white sucker (Catostomus commersonii) was present in all sampling periods. Quantitative comparisons of recent samples (1996 to 1997 versus 2004) indicated 41% faunal turnover between 1997 and 2004 (seven species missing, two species gained). However, the most remarkable change from 1997 to 2004 was the increased dominance of red shiner (Cyprinella lutrensis lutrensis; from 6 to 22%) and smallmouth bass (Micropterus dolomieu; from 3 to 18%), and disappearance of flathead chub (Platygobio gracilis; from 28 to 0%). A mix of historic inhabitants, invasive native species, and invasive nonnative species dominated the recent (2004) fish community. Possible explanations for dramatic fish assemblage flux below Angostura Dam include variable sampling bias and gear limitations, major flow regime differences between drought periods and normal periods, top-down effects of smallmouth bass predation, chronic effects of Angostura Dam on instream habitat conditions, or (most likely) a combination of these effects.

Modelling and optimisation of powertrains

At the Institute for Applied Mechanics of the Technical University of Munich, several specialised computer programs have been developed for the vibrational analysis of powertrains. This article focuses on the mechanical models of timing chain drives (included in KETSIM), continuously variable transmission gears using belts or chains as well as gears (in DYNAS), the cosimulation of different computer codes including hydraulics (HYSIM) and the optimisation of highly complex multidisciplinary systems. The programs stated above are in use for numerous industrial applications and have been verified by many comparisons between measurement and simulation. A mathematical optimisation has been added and is shown to give good results.

An experimental study for drivability improvements in vehicle acceleration mode

Modern vehicles require a high degree of refinement, including good drivability. Vehicle drivability, which becomes a key decisive factor for marketability, is affected by many parameters such as engine control and the dynamic characteristics in the drivelines. Therefore, engine and drivetrain characteristics should be analysed to achieve a well-balanced vehicle response simultaneously. This paper describes experimental procedures that have been developed to measure engine torque and investigate shuffle characteristics. A simplified powertrain model is presented for vehicle dynamic response analysis. Submodels within the model are the engine and drivetrain. Using this model, the friction and inertial moment for each submodel were measured, and effects of parameters were analysed. To analyse vehicle dynamics behaviour, frictional torques and the rotational inertia moment of the engine and the drivetrain were measured. Shuffle characteristics at the tip-in condition were investigated in an experimental vehicle at the second and third gear stages. It was found that shuffle characteristics are caused by sudden changes in engine torque and have a different vibration frequency with gear stage variation. The rotational inertia moment of the engine, including flywheel rotation, is a key factor influencing the shuffle characteristics.

Analytical Description of Meshing of Constant Pressure Angle Teeth Profiles on a Variable Radius Gear and its Applications

This paper presents a method for determining the profile of the gear teeth on a variable radius wheel characterized by a constant pressure angle. The method can generate special gears using numerically controlled milling machines. As will be shown, the method, applied to a constant radius gear, generates an involute profile. The method is based on the integration of a differential equation describing the mesh between gears of variable radius, where the mesh point position is computed during rotation starting from the point, freely selected, where the tooth crosses the pitch line. The individual point is subsequently rotated in the opposite direction by an angle equal to the angle of rotation from the initial pitch line point, thereby generating the tooth profile. The method, applied to a wheel of variable radius, defined analytically or numerically, can compute teeth profiles on pairs of pitch lines of any shape. In particular, the motion of a slotted rotating link mechanism has been reproduced, but for the sign. Teeth profiles of other variable radius wheels have also been obtained. The results are more than satisfactory and are presented below. A numerically controlled milling machine has been programmed to actually build the antirotating slotted link equivalent gear. The present method, however, has much broader application, such as assigning the speed law to consequentially determine the gear form, as can be done with cams. Furthermore, a special planetary gear train makes it also possible to obtain reciprocating motion driven solely by gears. This has been built and its picture and scheme are presented in the paper. However, due to the low efficiency of the said mechanism, the best way to utilize this new technology seems to be to couple a crank and a rod to the pair of variable radius gears, as has been done at Hanover University. Some possible applications are presented. The special feature of these gears is the programmability of the shape of the pitch lines during the design phase, and thus of the velocity and acceleration profiles. In this way velocity profiles that could formerly only be obtained electro-pneumatically can be produced from purely mechanical components, with the added advantage of being able to control the level of inertia forces during the design phase. [S1050-0472(00)01601-9]

Variable gearing during locomotion in the human musculoskeletal system.

Human feet and toes provide a mechanism for changing the gear ratio of the ankle extensor muscles during a running step. A variable gear ratio could enhance muscle performance during constant-speed running by applying a more effective prestretch during landing, while maintaining the muscles near the high-efficiency or high-power portion of the force-velocity curve during takeoff. Furthermore, during acceleration, variable gearing may allow muscle contractile properties to remain optimized despite rapid changes in running speed. Forceplate and kinematic analyses of running steps show low gear ratios at touchdown that increase throughout the contact phase.

Physiological evaluation of a newly designed lever mechanism for wheelchairs.

Lever-propelled wheelchairs have been described as more efficient and less physically demanding than hand-rim-propelled wheelchairs. To evaluate a newly designed lever mechanism (MARC) in both one- and two-arm use, a series of wheelchair exercise tests were performed on a motor-driven treadmill. Eight able-bodied male subjects performed a standard exercise test in the prototype MARC, both in an asynchronic and a synchronic bimanual propelling mode and in an unilateral (left-sided) mode. Subsequently the subjects performed additional exercise tests in a conventional crank-to-rod lever mechanism with unilateral and bimanual propulsion and in a conventional hand rim wheelchair. Analysis of variance was used to study the effect of the different work modes upon power output and cardiorespiratory parameters statistically (p < 0.05). The MARC stood out well in comparison with the conventional lever design. The additional design features which are to be implemented (variable gearing, reverse gear) will make the MARC a useful wheelchair. One-arm wheelchair propulsion is a very strenuous form of locomotion, requiring careful consideration in terms of provision. Mechanical and ergonomic improvements are quite feasible in lever propulsion and may to a certain extent reduce this problem. To improve overall mobility of wheelchair-dependent subjects further, ergonomic and mechanical design improvements are very necessary in lever as well as hand-rim wheelchairs. A combined biomechanical and physiological research approach will help in the definition of design criteria and fitting guidelines.

Control Strategy of PWM Inverter Drive System for Electric Vehicles

This paper presents an advanced ac drive system used in electric vehicles (EV's). The system consists of an induction motor, a PWM transistorized inverter, a variable ratio gear box and a controller. The special features of the drive system are discussed, with emphasis on the control strategy which can optimize the performance of the EV.

Dynamic Behavior of Gear Systems and Variation of Coefficient of Friction and Efficiency During the Engagement Cycle

In this work, the instantaneous and average efficiency and coefficient of friction of gear drives operating at low, medium, and moderately high speeds were experimentally and analytically investigated. First, using the gear testing machine specially designed for this type of investigation, the frictional losses in gearing during the engagement period were obtained experimentally. Based upon the obtained data, the values of efficiency and coefficient of friction were evaluated. A mathematical model simulating the gear testing machine was then developed and employed for the analysis of the dynamic behavior of the gear train system and analytical evaluation of gear system efficiency. The results obtained from this model were compared to those obtained directly from experiments, and a close correlation was achieved. The influence of such factors as diametral pitch, contact ratio, magnitude of transmitted load, and speed upon the efficiency of gear drives and the coefficient of friction in gearing was investigated. This investigation showed that the suggested method may be used to predict the dynamic behavior and efficiency of gear systems if a coefficient of friction is known or assumed. This investigation also gives some promise for power gear transmission design with improved capacity when scoring is the limiting criterion for capacity.

Closure to “Discussion of ‘Dynamic Behavior of Gear Systems and Variation of Coefficient of Friction and Efficiency During the Engagement Cycle’” (1975, ASME J. Eng. Ind., 97, p. 1280)

Closure to “Discussion of ‘Dynamic Behavior of Gear Systems and Variation of Coefficient of Friction and Efficiency During the Engagement Cycle’” (1975, ASME J. Eng. Ind., 97, p. 1280)

Discussion: “Dynamic Behavior of Gear Systems and Variation of Coefficient of Friction and Efficiency During the Engagement Cycle” (Radzimovsky, E., and Mirarefi, A., 1975, ASME J. Eng. Ind., 97, pp. 1274–1280)

Discussion: “Dynamic Behavior of Gear Systems and Variation of Coefficient of Friction and Efficiency During the Engagement Cycle” (Radzimovsky, E., and Mirarefi, A., 1975, ASME J. Eng. Ind., 97, pp. 1274–1280)

The selection of variable gear for minimum energy

The system under consideration is that of a motor, coupled by a gear train to an inertial load, where the requirement is to rotate the load by a given angle and come to a halt. The question considered is whether the use of a variable gear, instead of one with constant ratio, will reduce the required energy, and if so, what are the optimal gear ratio function and the corresponding control function.

A Carnot Theorem for Split Torque Variable Speed Gears

Used in conjunction with differentials a continuously variable gear can vary a larger power through a smaller range of ratios: limits on this process are established.

Illusion and Reality: A Study of the Sources of Poetry

ILLUSION AND REALITY A STUDY OF THE SOURCES OF POETRY By CHRISTOPHER CAUDWELL CONTENTS BIOGRAPHICAL NOTE INTRODUCTION THE BIRTH OF POETRY THE DEATH OF MYTHOLOGY THE INVOLVMENT OF MODERN POETRY ENGLISH POETS: I PRIMITIVE ACCUMULATION II THE INDUSTRIAL REVOLUTION III DECLINE OF CAPITALISM THE WORLD THE PHANTASY POETRYS DREAMWORK THE ARTS THE FUTURE OF POETRY..... BIBLIOGRAPHY INDEX BIOGRAPHICAL NOTE THIS is one of the great books of our time. It is not easy reading. It is a book to be studied and annotated and returned to again and again. The reader will then find that, however often he takes it up, it will always give him fresh food for thought. The author, Christopher St. John Sprigg, was born in Putney on October 20, 1907. He was educated at the Benedictine school at Ealing. He left school at sixteen and a half and worked for three years as a reporter on the Yorkshire Observer. Then he returned to London and joined a firm of aeronautical publishers, first as editor and later as a director. He invented an infinitely variable gear, the designs for which were published in the Automobile Engineer. They attracted a good deal of attention from experts. He published five textbooks on aero nautics, seven detective novels, and some poems and short stories. All this before he was twentyfive. In May, 1935, under the name of Christopher Caudwell, he published his first serious novel, This My Hand. It shows that lie had made a close study of psychology, but he had not yet succeeded in relating his knowledge to life. At the end of 1934 he had come across some of the Marxist classics, and the following summer he spent in Cornwall immersed in the works of Marx, Engcls, and Lenin, Shortly after hisreturn to London he finished the first draft of Illusion and Reality. Then, in December, he took lodgings in Poplar and later joined the Poplar Branch of the Communist Party. Many of his Poplar comrades were dockers, almost aggressively proletarian, and a little suspicious at first of the, quiet, well spoken young man who wrote books for a living out before long he was accepted as one of themselves, doing his share of whatever had to be done. A few months after joining the Party he went over to Paris to get a firsthand experience of the Popular Front and he came back with renewed energy and enthusiasm. Besides continuing to write novels for a living, he rewrote Illusion and Reality, completed . the essays published subsequently as Studies in a Dying Culture, and began The. Crisis in Physics. He worked to the clock. After spending the day at his typewriter, he would leave the house at five and go out to the Branch to speak at an openair meeting, or sell the Daily Worker at the corner of Crisp Street Market. . Meanwhile, the Spanish Civil War had broken out. The Poplar Branch threw itself into the campaign, with Caudwell as one of the leading spirits. By November they had raised enough money to buy an ambulance, and Caudwell was chosen to drive it across France.

最近の無段変速機

最近の無段変速機

A Note on the Checking of Variable Gears as Used for Integrators

A new technique is described for the accurate determination, with reference to some given scale, of the zero of a variable gear of the Bush type. Advantages over the now existing methods are claimed.

An Accurate Automatic Syringe Mechanism

An apparatus capable of transferring accurately successive predetermined volumes of a sterile medium to a bacterial culture flask is described. It consists of a glass syringe and valve system automatically operated by a compact series of levers attached to a power unit through a variable gear giving a wide range of interval between successive operations. Details of the construction of the lever system for positively moving the syringe plunger to and fro are given together with the means employed for adjusting the excursion of the plunger over a wide range and instructions for setting the mechanism for use. An improved syringe holder designed to grip the barrel rigidly but to allow of slight universal adjustment of alignment of its axis is also described.

The Effect of a Variable Gear Reduction on Propeller Performance in Modern Airplanes

The Effect of a Variable Gear Reduction on Propeller Performance in Modern Airplanes

Studies of High Speed Airplanes

The authors have devised a series of high speed design studies in which several advanced ideas and innovations are proposed. The factors having an important influence on high speed are considered and the airplane design arrangements are so proportioned as to minimize adverse effects, to the lowest values which are believed attainable without fundamental changes involving the invention of new principles of flight now unknown or undeveloped. Data are presented showing the lowest values of the drag of the component parts of a modern airplane, which represent current practices. Further data are given to show possible improvement in these values and the ones that may be entirely eliminated. An analysis of the factors influencing propeller design for high speed aircraft is made, together with a prediction of the propulsive efficiencies which may be obtained, based on recent research. The maximum attainable efficiency becomes less as the speed and altitude are increased. Possibilities of increasing the indicated optimum propulsive efficiencies and the desirability of a variable gear drive device, are discussed briefly. The paper concludes with the familiar presentation of a chart showing the advance in high speed by years, which is extrapolated on the basis of the authors ' studies to show a prediction of the maximum speed attainable with aircraft designed according to conventional practices. This maximum speed is considered attainable within two years. T authors have prepared this paper and present it from the point of view of the practicing designer and aerodynamicist. The contents represent studies of airplanes made in the manner employed in design offices, making use of the results of the authors' work with wind tunnel and flight tests. Rather than approach the subject in general terms or by a mathematical development it was decided to explore the high speed possibilities of the future by a study of an airplane design, with some systematic variations of gross weight, wing loading, and power. The prerequisites for maximum speed are well established and most of the factors have been discussed by other authors.' The factors used as a basis for the present design studies are (1) high wing loading; (2) entirely enclosed power plant; (3) selection of optimum propeller, arranged as a pusher; (4) mid-wing and tail arrangement with elimination of unfavorable interference; (5) a cabin and windshield enclosed within the normal contour lines of the fuselage; (6) a finely streamlined fuselage shape; (7) smooth body, wing, and tail surfaces with the suppression of all excrescences, wrinkles, rivet heads and skin laps; (8) Presented at the Aerodynamics Session, Eighth Annual Meeting, I.Ae.S., New York, January 26, 1940. Speed Airplanes

Variable Pitch Airscrews and Variable Gears

The subject defined by the title of this paper is one which cannot be covered completely in the time at my disposal. I propose therefore to confine my remarks to-night almost entirely to the aerodynamic aspects of the problem and to put before you some possible advantages that may be gained by substituting a variable pitch airscrew for the normal fixed pitch airscrew, and in certain cases to compare the results with those given by the introduction of a variable gear airscrew. The mechanical side of the problem is a subject complete in itself and will not be dealt with here.

A New Infinitely Variable Poppet Valve Gear

A New Infinitely Variable Poppet Valve Gear