Nptel syllabus mechanics of textile machinery web course course outline. When two teeth on a helical gear system engage, the contact starts at one end of the tooth and gradually spreads as the gears rotate, until the two teeth are in full engagement. Calculate forces on teeth of spur gears, including impact forces associated with velocity and clearances. To reduce the noise and stress in the gears, most of the gears in your car are helical. Camshaft is a type of rotating device or apparatus used in piston engines for propelling or operating poppet valves. The allowable static stresses for the bronze pinion and cast iron gear are 84 mpa and 105 mpa respectively. In some cases, such as the automotive differential, one input is provided the. The gear train maybe for spur gear, helical gear and spiral gear. Epicyclic gear trains are generally used for automatic transmission, overdrives, and final drives.
The gear train maybe for spur gear, helical gear and. In this lecture i shall cover gear unit design 1st stage pinion and gear. A basic rule of gears is if a large gear gear a turns a small gear gear b the speed increases. Spur gears with helicoid teeth are called helical gears. One is that the bushing needs to be wider to t over the cap on the pinion. It is used for transmitting rotational motion between parallel.
This text will not deal with the stress analysis aspects of gear design. It is an indication of the power transmitted through a driving shaft and from it the gear tooth loads are ealculated. Relative characteristics of gear types 1 best 5 worst ratio power speed relative space approx. Abstract gear is the one of the important machine element in the mechanical power transmission system. Straight gear teeth are those where the teeth axis is parallel to the shaft axis. Analysis of a gear train using finite element modelling. Power and torque is transmitted when a tooth of an input gears exerts a force f n along the pressure line on the tooth of output gear see figure a. Comparison of gear efficiencies spur, helical, bevel, worm. The smallest number of teeth on a spur pinion and gear, onetoone gear ratio, which can exist without interference is np. Gear ratio is numbers of teeth of larger gear to smaller gear.
Mounting type range capacity range cost required e. Epicyclic gear train nptel pdf automatic transmission has not better fuel economy. The number of teeth for spur gears is given by where k 1f fll1 for fulld tht th08f tbt th d ldepth teeth, 0. A complete gear train design will necessarily involve considerations of strength of materials and the complicated stress states to which gear teeth are subjected.
Apr 04, 20 a gear train may consist of spur, bevel or spiral gears. Another class of gear train has wide application, the epicyclic or planetary train. Pressure angle is the angle between the pressure line and common tangent to pitch circles. Gear design and engineering machine design and application. Determine allowable force on gear teeth, including the factors necessary due to. The transmission efficiency is relatively poor as compare to that of herringbone spur gear and helical gear. When gear a completes one revolution gear b turns 1. Kleiss nomenclature b w face width in the mesh d a outside circle diameter, mm in. The teeth on helical gears are cut at an angle to the face of the gear. This section on gearing and gear drives describes the major gear types.
New perspectives such as harmonic mean, contact patch as translating third body, contact form factor, and service load factor are introduced in spur gear design. Hw 1 problem 1 a 17tooth spur pinion paired with a 50 tooth gear has a diametral. Force analysis for spur gears equation and calculator. The gears shown below are called spur gears because they mesh together. Internal gears are often used in planetary gear systems. Ordinary gear trains have axes, relative to the frame, for all gears comprising the train. Make a drawing of the gears showing one tooth on each gear you may use a cad. A gear or cogwheel is a rotating machine part having cut teeth or, in the case of a cogwheel, inserted teeth called cogs, which mesh with another toothed part to transmit torque. Spur gears impose only radial perpendicular to axis loads on gear shafts as opposed to helical, bevel, and spiral bevel gears which impose both radial and thrust axial loads on gear shafts. Insert 1 gear on the ribbon, click design tab power transmission panel spur gear. Epicyclic gear train in combing machine motion of detaching roller, combing cycle index, web movement in one.
Gear a is called the driver because this is turned by a motor. Spur gear design and selection objectives apply principles learned in chapter 11 to actual design and selection of spur gear systems. It require small area during the power transmission and to obtain large speed reduction. The angle that the helical gear tooth is on is referred to as the helix angle. Simple compoundgear train n n n n t t t t r nn nn rr rr 26 tttt 16 15 14 15 14 12 23 34 45 56. Planetary gear trains example for the speed reducer shown, the input shaft a is in line with output shaft b. Spur gear is most basic gear used to transmit power between parallel shafts. Ppt spur gear powerpoint presentation free to download. The first gear known as the driver has 12 teeth, the second gear called the idler has 16 teeth, and the third gear known. Gear trains consist of two or more gears for the purpose of transmitting motion from one axis to another.
Force analysis spur gears equation and calculator engineers. Relationship between the involute elements determination of base tooth thickness from a known thickness and viceversa. Spur gearing is a parallel shaft arrangement, and these gears can achieve much higher efficiencies compared to other gear types. Gears are used in many applications like automobile engines, household appliances, industrial machine. American standard ansi mpb steel spur gears pressure angle 1412 o s311 s312 s3 s314 s315 s316 s317 s318 s319 s320 s321. Now, again module in case of straight tooth spur gear we simply call it. The angle of helix depends upon the condition of the shaft. The volume of the gear train with spur gears is reduced by 22. Epicyclic gear train nptel pdf in the first three types of gear trains, the axes of the shafts over which the gears are mounted are. A spur gear drive is a combination of two spur gears properly meshed with each other. Helical gear this is a cylindrical shaped gear with. Velocity ratios and gear trains for the gear train shown below, determine the train value, output speed, output direction, output torque, and output power. Epicyclic gear train nptel pdf merge this planetary gear train consists of a sun gear yellow, planet gears blue supported by the. Asok kumar mallik department of mechanical engineering iit kanpur.
What are the sources of errors in gears and measurement of spur gear. Spur gear helical gear double helical or herringbone gear internal gear rack and pinion bevel gear a straight b spiral c hypoid 1. Though several types of profiles can be used for cutting teeth on a spur gear, we commonly use involute teeth profile. Helical gearing, in which the teeth are cut at an angle with the axis of rotation, was developed after spur gearing and has the advantages that has the smoother action and tends to be trainw fig. Internal spur gear august 15, 2007 32 internally meshing spur gears figure 14. This type of gear comes with two kinds of tooth profiles in accordance with the datum surface.
Figure 76a shows a simple ordinary train in which there is only one gear for each axis. Software gto provides the required results in a very short time. And, people call also call it as a selflocking mechanism. Jan 01, 20 interference of spur gears on spur and gear with onetoone gear ratio, smallest number of teeth which will not have interference is k 1 for full depth teeth. Depending upon the type and accuracy of motion desired. Formulas for gear calculation external gears contents. Spur gear helical gear herringbone gear bevel gear worm gear rack and pinion internal and external gear face gear sprcokets 1. Cylindrical spur gears with standard profile cylindrical spur gears with corrected profile without centre distance variation with centre distance variation.
Introduction to gear trainsintroduction to gear trains. Yi zhang with susan finger stephannie behrens table of contents. So, we start with nomenclature of gears, by doing that i will define all the relevant terms with reference to circular straight tooth spur gears. Lecture series on manufacturing processes ii by prof. Bevel gear precision forging production line according to user requirements for the bevel gear accuracy, the forging process is also very different. Whats the difference between spur, helical, bevel, and. Generally speaking, when two spur gears are in mesh, the gear with more teeth is called the gear and the one with the smaller number of teeth is called the pinion. Gear design and strength iupital has good strength, durability, wear resistance, and chemical resistance, so can be used to each gear. Inclined gear teeth are those where the teeth axis is at some angle. Each time a gear tooth engages a tooth on the other gear, the teeth collide, and this impact makes a noise. To perform a static and thermal analysis of a gear train. Design spur gears inventor autodesk knowledge network.
Typically, shaft orientation, efficiency, and speed determine which of these types should be used for a particular application. Interference of spur gears on spur and gear with onetoone gear ratio, smallest number of teeth which will not have interference is k 1 for full depth teeth. Direct gear design for spur and helical involute gears. University of johannesburg, department of mechanical engineering, p. This gradual engagement makes helical gears operate much more smoothly and quietly than spur gears. Find the ratio of the output speed to the input speed. The pinion has 16 standard 20 full depth involute teeth of module 8 mm. Jan 17, 2018 for the love of physics walter lewin may 16, 2011 duration. Spur gears and simple gear trains technology student. As gear a turns it meshes with gear b and it begins to turn as well. In case of rope and belt drives we have seen that the velocity ratio transmitted cannot be exact due to the slip of rope or belt on the pulley. The tooth numbers are n 2 24, n 3 18, n 5 22, and n 6 64. A gear can be defined as a toothed wheel which, when meshed with another toothed wheel with similar configuration, will transmit rotation from one shaft to another. A spur gear is designed to mesh with another spur gear on a parallel shaft.
Design of machinery an introduction to the synthesis and. Gear design national broach and machine division,of lear siegler, inc. Pressure line is the common normal at the point of contact of mating gears along which the driving tooth exerts force on the driven tooth. In the gear 2 section, select no model from the selection list. Gear train conguration appendix a8 another interesting design aspect is that the gear train reverts back to the axle about which the pinion turns. Gear wreck will happen because of its tooth fatigue and tooth surface wear, so strength design from both side is necessary. A gear train may consist of spur, bevel or spiral gears. Internal gear this is a cylindrical shaped gear but with the teeth inside the circular ring. Its efficiency varies from 94% to 98% with lower gear ratios.
Design and analysis of spur gear pinaknath dewanji mechanical engineering gitam institute of technology, gitam university, rushikonda, india. The gear found in the image above uses an involute tooth profile. The spur rack is a portion of a spur gear with an infinite radius. Table 1 compares these factors and relates them to the specific gear selections. In the gear 1 section, select component from the list. Whats the difference between spur, helical, bevel, and worm gears. Gears are classified as straight, inclined and curved. Helical tooth spur gear and loads on gear shaft nptel.
Following are the different types of gear trains, depending upon the arrangement of wheels. If the mating gear has more teeth than the pinion, that is. Epicyclic gear train nptel pdf merge helical gearing, in which the teeth are cut at an angle with the axis of rotation, was developed after spur gearing and has the advantages that has the smoother action and tends to be trainw fig. Straight bevel gearing is similar to spur gearing with perpendicular shaft arrangement. Paul,department of mechanical engineering, iit kharagpur. Nptel syllabus mechanics of textile machinery web course course outline machine elements and drives introduction to drives, selection of drives, primary machine. Gears almost always produce a change in torque, creating a mechanical advantage, through their gear ratio, and thus may be considered a. Types of gear train and velocity ratio calculation techminy.
Mech zone is an educational channel providing free of cost video lectures to the students of mechanical, civil, material science, chemical, production and industrial engineering branch. When pinion is the driver, it results in step down drive in which nptl output speed. Direct gear design for spur and helical involute gears alexander l. When two gears of different sizes are meshed, the larger is called gear while the smaller is pinion. Geared devices can change the speed, torque, and direction of a power source. The primary purpose of gears is to transmit motion and at the same time, multiply either torque or speed, torque is a function of the horsepower and speed of the power source. The gear wheel transmitted motion between one shaft to another shaft, so the multiple set of gear transmit motion from single main gear to various revolving parts is known as gear train. Mar 29, 2020 epicyclic gear train nptel pdf merge sijthre.
Nptel nptel online certification course course on spur. Types of gear trains following are the different types of gear trains, depending upon the arrangement of wheels. Now, this is hand lever driven pinion and gear with winch. The majority of calculations for spur gears can be applied to helical gears too. On the other hand, spur gears have a disadvantage in that they easily make noise. Simple gear train the simple gear train is used where there is a large distance to be covered between the input shaft and the output shaf.
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