Technology & Engineering
Epicyclic Gear
An epicyclic gear, also known as planetary gear, is a gear system consisting of one or more outer gears, called planet gears, revolving around a central gear, known as the sun gear. This arrangement allows for compact and efficient speed and torque transmission, commonly used in automotive transmissions, bicycles, and industrial machinery.
Written by Perlego with AI-assistance
10 Key excerpts on "Epicyclic Gear"
eBook - PDF- Sparrow Consulting(Author)
- 2021(Publication Date)
- Future Managers(Publisher)
A gear can do this through gear ratios, which is the ratio of the output speed to the input speed. This is important in heavy machinery and trucks that require large amounts of torque to function correctly. • Gears can also reverse the direction of rotation. This is important in many applications, such as the ability of a vehicle to reverse. Definition Torque – a force that produces rotation of an object 1.1 Epicyclic Gears An Epicyclic Gear, also known as a planetary gear, is used most often due to its many benefits and applications. It has three main components: • Sun gear: the central gear in an Epicyclic Gear train that meshes with the planetary gears • Planetary gears or pinions: the gears that mesh with both the sun gear and the ring gear • Ring or annulus gear: the outer gear in an Epicyclic Gear train. 3 N5 Mechanotechnics|Hands-On! The planet gears are mounted onto a planetary carrier or arm that rotates all the planetary gears relative to the sun gear. An arrangement of the three main components and the planetary carrier is shown in Figure 1.1. Epicyclic Gears are used: • in compact areas (where space and weight are an issue); • as speed reducers; • to apply torque; and • for automatic transmissions. They have many applications and are used extensively throughout automation, machinery and industry. Some common examples where Epicyclic Gears are used are electric screwdrivers, lathes, oscillating sprinklers, automatic transmissions in vehicles, turbines, watches, robotic arms, hoists, pulley blocks and the power train between an internal combustion engine and an electric motor. Note The word ‘epicyclic’ was first used in 500 BC by the Greeks. They invented the idea of epicycles (circles travelling on circular orbits) to model planetary orbital paths such as the earth rotating around the sun. 1.1.1 Spur gears There are different types of gears available today. Each different design has its own functions, advantages and disadvantages.
eBook - PDF- J. Carvill(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
Various gear ratios can be obtained depending upon which member is held stationary, the inner gear, the outer gear or the planet gear ring. In an Epicyclic Gearbox the various elements are held by friction brakes as desired. An advantage of Epicyclic Gears is that their input and output shafts are concentric. GEAR TRAIN Figure 1.,97 Internal gear When more than two gears are employed the system Epicyclic Gear i s k n 0 w n a s zgear train. When these gears are mounted in a casing with a lubrication system the assembly is An Epicyclic Gear comprises a sun gear keyed to a called a gearbox. An intermediate shaft is called a central shaft, and several planet gears which are meshed lay shaft. with and revolve around the sun gear. The planet gears In an automobile gearbox some of the gears are on are mounted on spindles held in position by a carrier splined shafts and can be moved by using a hand attached to a sleeve running on the sun gear shaft. operated gear selector to give different speed ratios. Figure 1.98 Epicyclic Gear 22 Figure 1.100 Double reduction gear train Figure 1.101 Gear changing Figure 1.101a Splined gear shaft GEAR MATERIALS Gears are made from cast iron for light duty, and cast and alloy steels for heavy duty. Bronze is used for worm gears. Plastics, particularly laminates such as Tufnol, are used in special cases. Small gears are usually cast or forged, and large gears, e.g. marine gears, are welded fabrications. Steel gears often have the teeth case-hardened and ground to a high surface finish. Figure 1.102 Cast steel gear Figure 1.103 Welded steel gear 1.5 FLU ID SEALS, JOINTS AND GASKETS FLUID SEALS Fluid seals are devices for preventing unwanted leakage of liquids and gases in machines. The seal may be between two fixed parts or two parts with relative motion. Seals between fixed parts are generally known as joints, gaskets and sealing washers.
eBook - PDFMechanotechnics N4 Student's Book
TVET FIRST
- R Cameron(Author)
- 2021(Publication Date)
- Macmillan(Publisher)
Typically, the planet gears are mounted on a movable lever arm or carrier which itself Epicyclic Gear system: a gear system consisting of one or more outer gears (planet gears) that revolve about a central gear (sun gear) 123 Gear drives TVET FIRST may rotate relative to the sun gear. Epicyclic Gear systems also contain an outer ring gear or annulus, which meshes with the planet gears. (See Figure 5.28.) An Epicyclic Gear system can be used to perform several different functions. For example, it can be used to: • Reduce speed while increasing torque. • Increase speed while reducing torque. • Change direction. All these functions are possible by applying the input rotation to different gears and holding one of the other two gears stationary. annulus lever arm (carrier) planet sun planet planet planet Figure 5.28: Epicyclic Gear system Note An Epicyclic Gear system is also known as a planetary gear system. In an Epicyclic Gear system, the motion is derived by rotating the lever arm. This carries at least one of the wheels (planets) around the axis of another wheel of the system. The result is that the wheels receive a compound rotation. In addition to the amount owing to the value of the system, one revolution is given owing to the rotation of the lever arm. 5.4.1 Basic working of an Epicyclic Gear system The number of times that a planet pinion rotates on its shaft when making one complete revolution around the sun gear depends on the gear ratio. Suppose that the ratio between two gears is 3:1. So, the sun gear has 18 teeth and the planet pinion has 6 teeth. The planet pinion rotates four times around its own shaft to complete one revolution around the stationary sun gear. The fourth rotation comes from the change of position of the planet pinion as it moves around the sun gear.
eBook - PDF- M.J. Nunney(Author)
- 2016(Publication Date)
- Newnes(Publisher)
However, a point of further interest is that in the early 1980s the British company of Self-Changing Gears Ltd introduced a fully automatic five-speed transmission system for European and American city buses, which is based on the original Wilson gearbox but is provided with electrohydraulic control. Epicyclic Gearing has by no means been confined to use in gearboxes. Among the other applications of this type of gearing that may be found in motor vehicles are overdrive units for passenger cars and light commercial vehicles; two-speed final drives and hub reduction gears for heavy-vehicle rear axles; and torque-dividing dif-ferentials in the transfer gearing of four-wheel-drive vehicles. Advantages of Epicyclic Gearing The principal advantages of an epicyclic over a layshaft gear train may be summarized as follows: 1 Changes from one ratio to another can be effected without interruption of the drive, because the per-manently meshed gear train is engaged by friction elements. 2 It can be made more compact for a given torque capacity, because its members rotate about a common axis and there are a greater number of teeth in contact to share the load. 3 It is more versatile in application because it makes available a wider combination of ratios from a given gear train, although there are limits on the ratio attainable in practice. 4 The gear separating forces are balanced and self-contained, which together with a relatively low speed of tooth engagement is conducive to quiet operation. Basic construction of an Epicyclic Gear train An Epicyclic Gear train comprises three essential mem-bers, which are known as the sun gear, planet pinions 261 262 LIGHT AND HEAVY VEHICLE TECHNOLOGY and annulus gear (Figure 16.1). The sun gear is situated on the central axis of the gear train. Surrounding the sun gear are the planet pinions, which can freely rotate on pins mounted in a planet carrier and are equally spaced around the sun gear with which they are per-manently meshed.
eBook - ePub- M J Nunney, Malcolm Nunney(Authors)
- 2007(Publication Date)
- Routledge(Publisher)
The successful combination of the Wilson Epicyclic Gearbox and fluid coupling is known to have influenced the early development of the fully automatic gearbox by General Motors in America. Where the modern automatic gearbox differs from the earlier Wilson gearbox is chiefly in the more economic arrangement of its Epicyclic Gearing and the more sophisticated manner in which the motion of selected members is controlled. However, a point of further interest is that in the early 1980s the British company of Self-Changing Gears Ltd introduced a fully automatic five-speed transmission system for European and American city buses, which is based on the original Wilson gearbox but is provided with electro-hydraulic control.Epicyclic Gearing has by no means been confined to use in gearboxes. Among the other applications of this type of gearing that may be found in motor vehicles are overdrive units for passenger cars and light commercial vehicles; two-speed final drives and hub reduction gears for heavy-vehicle rear axles; and torque-dividing differentials in the transfer gearing of four-wheel-drive vehicles (Sections 18, 20 and 21).Advantages of Epicyclic Gearing
The principal advantages of an epicyclic over a layshaft gear train may be summarized as follows:1 Changes from one ratio to another can be effected without interruption of the drive, because the permanently meshed gear train is engaged by friction elements. 2 It can be made more compact for a given torque capacity, because its members rotate about a common axis and there are a greater number of teeth in contact to share the load. 3 It is more versatile in application because it makes available a wider combination of ratios from a given gear train, although there are limits on the ratio attainable in practice. 4 The gear separating forces are balanced and self-contained, which together with a relatively low speed of tooth engagement is conducive to quiet operation.Basic construction of an Epicyclic Gear train
An Epicyclic Gear train comprises three essential members, which are known as the sun gear, planet pinions and annulus gear (Figure 16.1
eBook - PDF- M.J. Nunney(Author)
- 2013(Publication Date)
- Newnes(Publisher)
However, a point of further interest is that in the early 1980s the British company of Self-Changing Gears Ltd introduced a fully automatic five-speed transmission system for European and American city buses, which is based on the original Wilson gearbox but is provided with electrohydraulic control. Epicyclic Gearing has by no means been confined to use in gearboxes. Among the other applications of this type of gearing that may be found in motor vehicles are overdrive units for passenger cars and light commercial vehicles; two-speed final drives and hub reduction gears for heavy-vehicle rear axles; and torque-dividing dif-ferentials in the transfer gearing of four-wheel-drive vehicles. Advantages of Epicyclic Gearing The principal advantages of an epicyclic over a layshaft gear train may be summarized as follows: 1 Changes from one ratio to another can be effected without interruption of the drive, because the per-manently meshed gear train is engaged by friction elements. 2 It can be made more compact for a given torque capacity, because its members rotate about a common axis and there are a greater number of teeth in contact to share the load. 3 It is more versatile in application because it makes available a wider combination of ratios from a given gear train, although there are limits on the ratio attainable in practice. 4 The gear separating forces are balanced and self-contained, which together with a relatively low speed of tooth engagement is conducive to quiet operation. Basic construction of an Epicyclic Gear train An Epicyclic Gear train comprises three essential mem-bers, which are known as the sun gear, planet pinions Epicyclic GearBOXES 307 and annulus gear (Figure 16.1). The sun gear is situated on the central axis of the gear train. Surrounding the sun gear are the planet pinions, which can freely rotate on pins mounted in a planet carrier and are equally spaced around the sun gear with which they are per-manently meshed.
eBook - PDF- Ajeet Singh(Author)
- 2017(Publication Date)
- Cambridge University Press(Publisher)
9.6 Epicyclic Gear Trains An Epicyclic Gear train consists of one or more rotating gears, revolving around a central gear. Epicyclic trains also called as planetary gear trains. These are suitable, where large speed reduction is required in a compact space. It has four elements, which are interconnected to each other as shown in Figure 9.3. a . Central gear It rotates about its own central axis at a speed of w c . This gear can be external gear or internal gear. If it is external gear, it is also called as sun gear. Figure 9.3(a) shows sun gear as external gear and Figure 9.3(b) shows central gear as a ring or annulus gear as an internal gear. b. Arm / Spider It also rotates about the same axis as that of central gear at angular velocity w a . If there is only one planetary gear, it is called arm. If there are three or four planetary gears, it is called planet carrier or spider (Figure 9.4). Fundamentals of Machine Design, Volume II 352 Axle S P Input Output Arm Arm A P Arm Axle A P Input Output A = Annulus gear = Planetary gear = Central gear = Sun gear P C S (a) External central gear (b) Internal central gear Figure 9.3 Epicyclic Gear train c. Planetary gear It is mounted on an axle fitted on one end of the arm. It meshes with the sun gear and rotates at rotational speed of w p about its own axis. Since it rotates in the same way as the planets rotate about the sun, this gear is called planetary gear. Number of plenary gears can be two or three or four as shown in the pictures below. P Spider P P P S A P Spider Axle Two planetary gears Three planetary gears Four planetary gears Figure 9.4 Epicyclic Gear train with three planetary gears on a spider Generally in gear boxes, three or four planetary gears are used to keep the rotating masses balanced. The arm is replaced by a spider having three or four arms as shown in Figure 9.4. Following are the unique features of this drive:
eBook - PDFMechanotechnics N5 Student's Book
TVET FIRST
- P du Toit(Author)
- 2021(Publication Date)
- Macmillan(Publisher)
Gear B meshes with gear A and has its axis on the arm at O 2 , about which the gear B can rotate. If the arm is fixed, the gear train is simple. Then, gear A can drive gear B or vice versa. But, if gear A is fixed and the arm is rotated about the axis of gear A (i.e. O 1 ), then the gear B is forced to rotate upon and around gear A. This motion is called epicyclic. The gear trains arranged in a way that one or more of their members move upon and around another member are known as Epicyclic Gear trains. The Epicyclic Gear trains may be simple or compound. 1.6.1 Pitch circle diameters of planetary gears To calculate the number of teeth on the ring gear, look at Figure 1.16. PCD ANNULUS = PCD SUN + 2 × PCD PLANETARY But: PCD = m × T Therefore: T A = T S + 2 × T P 1.6.2 Torque on Epicyclic Gears The purpose of any gearbox is to change the torque between input and output. For this reason, the gearbox case has to be clamped to stop it from rotating. An Epicyclic Gear train is kept in equilibrium by three externally applied torques. This is the case only if there is no angular acceleration of any of the members. We will not consider any frictional losses. The three torques are: • The input torque on the driving shaft (T I ). • The resisting or output torque on the output shaft (T O ). • The holding or braking torque on the fixed member (T H ). Look at Figure 1.17 to see the following: • When the input and output shafts rotate in the same direction, then the input and output torques will act in opposite directions. • When the input and output shafts rotate in opposite directions then the input and output torques will act in the same direction. B A C O 1 O 2 Figure 1.15: Simple Epicyclic Gears S P A PCD S PCD P PCD P PCD A Figure 1.16: Pitch circle diameters
- Ganapathy Nagarajan(Author)
- 2024(Publication Date)
- CRC Press(Publisher)
Epicyclic Gear trains 昀nd their applications in textile machines especially in differential gear box of speed frames and in comber machines. It is useful for transmitting high velocity ratios with gears of moderate sizes in comparatively lesser space. 2.2.6 Velocity ratio of Epicyclic Gear train Two methods are in practice to 昀nd out the velocity ratio of epicycle gear train: 1. Tabular method 52 Textile Mechanisms in Spinning and Weaving Machines 2. Algebraic method These methods are discussed in detail as follows. 1. Tabular method Consider an Epicyclic Gear train as shown in Fig. 2.6. Let T A = Number of teeth on gear A T B = Number of teeth on gear B Let us suppose that the arm is 昀xed. Therefore the axes of both the gears are also 昀xed relative to each other. When the gear makes one revolution anti- clockwise, the gear B will make T A /T B revolutions. Assuming anti-clockwise rotation as positive and clockwise rotation negative, we can say that gear A makes +1 revolution anti-clockwise, gear B will make (−T A /T B ) revolutions. This statement of relative motion is entered in the 昀rst row of Table 2.1. Secondly, if the gear A makes +x revolutions, then the gear B will make (−x *T A /T B ) revolutions. This statement is entered in the second row of Table 2.1. In other words, multiply the each motion entered in the 昀rst row by x. Thirdly, each element of an epicyclic train is given +y revolutions and entered in the third row. Finally, the motion of each element of the gear train is added up and entered in the fourth row. Table 2.1 Table of motions Step no. Conditions of motions Arm C Gear A Gear B 1 Arm 昀xed,. Gear A rotates through +1 revolution. i.e. anti-clockwise 0 +1 –T A /T B 2 Arm 昀xed.
No longer available |Learn more- (Author)
- 2014(Publication Date)
- Orange Apple(Publisher)
Such a mechanism is used in automobiles to convert the rotation of the steering wheel into the left-to-right motion of the tie rod(s). Racks also feature in the theory of gear geometry, where, for instance, the tooth shape of an interchangeable set of gears may be specified for the rack (infinite radius), and the tooth shapes for gears of particular actual radii then derived from that. The rack and pinion gear type is employed in a rack railway. Epicyclic Epicyclic Gearing ____________________ WORLD TECHNOLOGIES ____________________ In Epicyclic Gearing one or more of the gear axes moves. Examples are sun and planet gearing and mechanical differentials. Sun and planet Sun (yellow) and planet (red) gearing Sun and planet gearing was a method of converting reciprocal motion into rotary motion in steam engines. It played an important role in the Industrial Revolution. The Sun is yellow, the planet red, the reciprocating crank is blue, the flywheel is green and the driveshaft is grey. Harmonic drive Harmonic drive gearing ____________________ WORLD TECHNOLOGIES ____________________ A harmonic drive is a specialized proprietary gearing mechanism. Cage gear Cage gear in Pantigo Windmill, Long Island A cage gear , also called a lantern gear or lantern pinion has cylindrical rods for teeth, parallel to the axle and arranged in a circle around it, much as the bars on a round bird cage or lantern. The assembly is held together by disks at either end into which the tooth rods and axle are set. Nomenclature General nomenclature Rotational frequency, n Measured in rotation over time, such as RPM. Angular frequency, ω Measured in radians per second. 1 RPM = π / 30 rad/second ____________________ WORLD TECHNOLOGIES ____________________ Number of teeth, N How many teeth a gear has, an integer. In the case of worms, it is the number of thread starts that the worm has. Gear, wheel The larger of two interacting gears or a gear on its own.
Index pages curate the most relevant extracts from our library of academic textbooks. They’ve been created using an in-house natural language model (NLM), each adding context and meaning to key research topics.
