Power Transmission

5 Key excerpts on "Power Transmission"

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  eBook - ePub

  Hydrostatic Transmissions and Actuators

  Operation, Modelling and Applications

  • Gustavo Costa, Nariman Sepehri(Authors)
  • 2015(Publication Date)
  • Wiley

    (Publisher)

  Chapter 1 Introduction to Power Transmission

  The term Power Transmission refers to a collection of devices assembled to transmit power from one physical point to another. In this chapter, we describe the most common types of Power Transmissions and introduce the subject of hydrostatic transmissions and actuators. This chapter is divided into six parts:

  • Mechanical transmissions
  • Hydrodynamic transmissions
  • Hydrostatic transmissions
  • Hydromechanical transmissions
  • Mechanical actuators
  • Hydrostatic actuators

  It is important to mention that there are other types of Power Transmissions. For example, an electricity gridline is a type of Power Transmission – from the generator to the final user. However, when mechanical energy is involved (kinetic and potential), the aforementioned types are the most representative.

  The majority of this chapter deals with the topic ‘transmissions’, with a smaller portion dedicated to ‘actuators’, as actuators can be seen as a special type of hydrostatic transmission where the motor is replaced by a hydraulic cylinder. We start with a basic concept common to both mechanical and hydrostatic transmissions: the transmission ratio.

  1.1 Transmission Ratio

  1.1.1 Generalities

  Figure 1.1 illustrates a typical situation where a Power Transmission can be applied. The input shaft is rotating with an angular speed and is connected to a prime mover (such as an electric motor or an engine) whose output power is . We connect the input shaft to an output (driven) shaft that must rotate at an angular speed . The angular speed of the driven shaft may be greater or lesser than the angular speed of the input shaft or even have an opposite direction in relation to the input shaft's angular speed.

  Figure 1.1

  Typical situation requiring a Power Transmission

  When mechanical transmissions, such as gearboxes, belts and chains, are considered, the spatial arrangement of the driving and driven shafts is of paramount importance because it dictates the technology to be used. For example, in the case of parallel shafts, a gear transmission may be used if their distance from each other is not too great. However, the farther the shafts are from each other, the heavier the gearbox becomes, leading to more demanding requirements with respect to alignment and lubrication. Belts and pulleys may be used for transmissions between shafts that are separated by a considerable length, but the problem of spatial arrangement remains. Moreover, the power to be transmitted becomes considerably limited due to the belt-to-pulley friction coefficient. Chain transmissions are noisy and require the shafts to be perfectly parallel with constant lubrication. Additionally, these types of transmissions – with the exception of some special arrangements of chains and belts – do not allow for continuous transmission ratios, as will be explained shortly.

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  eBook - ePub

  Farm Machinery and Equipment

  • Harris Pearson Smith(Author)
  • 2020(Publication Date)
  • Morse Press

    (Publisher)

  CHAPTER 4

  TRANSMISSION OF POWER AND COMPONENT PARTSOF MACHINES

  The method of transmitting power from its source to the point of use is one of the greatest problems of the farm-equipment designer. The problem is relatively simple when a tractor is used to operate a threshing machine. The size and speed of the pulleys on the two units are approximately the same. The tractor pulley is lined up with the thresher pulley, and a flat belt is fitted over them and tightened by backing the tractor. The power is ready to be transmitted from the tractor to the thresher. But the problem is multiplied many times in the case of a self-propelled combine, where the source of power is an engine mounted on the machine. Power must be transmitted to a slow-revolving reel and to a high-speed fan. Rotating movement must be changed into back-and-forth movement for the knife on the cutter bar and to an oscillating or shaking movement for the straw rack and grain pan. All this is done by means of pulleys and belts, sprocket wheels and chain, gears, and shafts. The operation is made possible by having good bearings to support the shafts and parts. The various parts of the machine are held together by different kinds of bolts and screws. Therefore, it is well to learn something about all these units to have an appreciation of their use in the design and construction of farm equipment.

  METHODS OF TRANSMITTING POWER

  The methods of transmitting power in connection with farm equipment are (1) direct drive, (2) pulleys and belts, (3) sprocket wheels and chain, (4) gears, (5) shafts and universal joints, and (6) flexible shafting.

  Direct Drives. When a machine is driven directly from the shaft of an electric motor or internal-combustion engine, this is termed a direct drive or direct connection

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  eBook - ePub

  Control Methods for Electrical Machines

  • Rene Husson(Author)
  • 2013(Publication Date)
  • Wiley-ISTE

    (Publisher)

  Chapter 1

  Overview of Mechanical Transmission Problems 1

  1.1. Technological aspects

  The direct approach of a system of mechanical transmission of power may be delicate. In this chapter, we propose to assimilate a real mechanism to a discrete mechanical system. We will then identify its main components and propose a classification based on their efficiency (in section 1.1.1 ; see also [SPI 97]). The general theorems of mechanical application to these simple models after an easy mathematical treatment will highlight the relevant parameters governing machine performance and point to directions of thought in order to improve the command of those mechanisms (sections 1.1.2 , 1.1.3 and 1.1.4 ; see also [SPI 97]). Finally, the main elements of tribology will be presented in section 1.1.5 . Indeed, the study of friction and lubrication and their consequences constitutes an essential part in the conception and the functioning of machines.

  1.1.1. General structures of the machines

  These engines are connected with machines through transmission power systems or mechanisms such as gearings, belts or chains, clutches or brakes, systems connecting rod-crank or the sawnut systems, cams or eccentric, elastic coupling.

  Any mechanism is put in motion by an entrance element called the leading or driving element, which supplies the driving energy. An exit element called the led or receiving element is the element by which the energy connected to loads goes out of the mechanism. The power circulates from the engine towards loads. The exit of a component constitutes the entrance of the next component.

  1.1.1.1. Engine

  In a power converter, the engine receives as an input an electrical power; as an output this power is always a mechanical power (couple and angular speed or strength and linear speed). The variation curve of the couple or the strength according to the speed is the curve of capacity of the engine, the characteristic of the engine. This conversion involves losses and therefore the notion of the engine’s efficiency is introduced.

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  eBook - PDF

  Mechanical Science

  • W. C. Bolton(Author)
  • 2013(Publication Date)
  • Wiley-Blackwell

    (Publisher)

  Chapter 13 Power Transmission 13.1 Machines and some basic definitions A machine is a mechanical device which can enable: • A force to be perhaps magnified, e.g. a screw jack, or reduced. • A force to be applied in a more convenient direction. • The displacement of the point of application of a force to be magnified or reduced, e.g. a lever. They are Power Transmission devices. Some basic terms used in describing the operation of machines are: 1 The effort is the input force to the machine. 2 The load is the output force from a machine. 3 The force ratio or mechanical advantage (MA) is the ratio load/effort. 4 The movement ratio or velocity ratio (VR) is the ratio (distance moved by effort)/(distance moved by load). 5 The efficiency of a machine is the fraction: (energy transferred from the machine to the load)/(energy transferred from the effort to the machine) or, if we consider the energy input and output per second, (power input)/(power output). For an ideal machine where there are no frictional forces, mechanical energy is conserved and so the work done by the effort must equal the work done by the load, thus effort × distance moved by effort = load × distance moved by load This can be rearranged to give load effort = distance moved by effort distance moved by load and so we have MA = VR. For a non-ideal, simple machine, the relationship between the effort E and the load L is of the form E = aL + b 324 Power Transmission 325 where a and b are constant. In the ideal machine b is zero; in the non-ideal machine it can be considered to be the effort needed to overcome friction. Hence MA = F E = F aL + b = 1 a + b/L If the load is large, then b/L becomes small and so the mechanical advantage approximates to 1 /a .

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  Engineering Practice with Oilfield and Drilling Applications

  • Donald W. Dareing(Author)
  • 2022(Publication Date)
  • Wiley-ASME Press Series

    (Publisher)

  Part II Power Generation, Transmission, Consumption Every machine has three functional aspects: (i) Power supply, (ii) Power Transmission and (iii) end use. Machines are designed to perform to a given set of specifications as discussed in Part I. During the process of achieving an end use, energy is consumed as indicated in the drawing. Power generation Power Transmission End use Fuel Exhaust Friction There are several options for a power source (electric motors, gasoline engines, diesel engines, gas turbines). Output performance of each dictates which is best for a given application. Power is trans-mitted by means of any one of several mechanisms (gears, pulleys, linkages, power screw, hydrau-lics) to achieve a specified end effect. Part of input energy will be lost to friction or other inefficiencies. Part II covers these aspects of machine design. The oil well drilling rig and its five subsystems is used to illustrate this process. 123 Engineering Practice with Oilfield and Drilling Applications , First Edition. Donald W. Dareing. © 2022 John Wiley & Sons, Inc. Published 2022 by John Wiley & Sons, Inc. 3 Power Generation Water Wheels The water wheel was used as a source of power for many years. The evolution of the water wheel was driven by population growth and the need for greater food output. The Egyptian Nora (~700 BC) was used to lift water for irrigation. The Romans milled grain during the fourth century AD and at the time of William the Conqueror, England had about 5000 grist mills. By 1790, there were about 2000 grist mills in colonel America. By the time of the Civil War, there were some 55 000 water wheels in use, many powered manufacturing facilities. Power generated by the water wheel (~10 hp) was transmitted through gear trains to achieve a required output torque and speed. Grist mills typically have a gear ratio of 25 : 1 with the millstone having the higher speed and lower tor-que.

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