Introduction to gear trainsintroduction to gear trains. Metrology metrology is the science of measurement dimensional metrology is that branch of metrology which deals with measurement of dimensions of a part or workpiece lengths, angles, etc. Gears are machine elements that transmit motion by means of successively engaging teeth. J s campbell, principles of manufacturing materials and processes. Lecture gear unit design failure of gear tooth probable dynamic load and wear load. A toothed gear must have an integral number of teeth. Page 2 page 2 basics terms a gear is a set of toothed wheels gear wheels or cogwheels that work together to transmit movement. Al s b it f h d k t h f assembled plan view also submit a freehand sketch of plan view one copy per group. In order to overcome this there are many methods to avoid gear tooth interference su. Functions of a gear power transmission change rotational speedtorque maintain constant speed ratio me 338.
When gear sets are visualized as a pair of smooth contacting. The pitch circle is a circle on the face of a gear that passes through points that are radially half way up the working depth of the teeth. A separate part of the mould, made of sand and generally baked, which is used to create openings and. Many of the everyday mechanisms and devices we commonly use contain gear wheels. 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. Stadtfeld introduction the most basic case of a gear train is the transmission of rotation and power between two parallel shafts. Finding the length of the path of contact, l ac figure 3 highlights a triangle that will allow us to calculate l ap, which is a portion of l ac. Important casting terms nptel course on manufacturing processes i, pradeep kumar et al. Spur gear creation american society for engineering. Download pdf gear technology a new bevel gear cutting machine, a fuljload.
Unit 6 gear generation and finishing gear generation. Gear size, pressure angle, number of teethwe introduce the basic terminology, measurement, and relational expressions necessary to understand basic gear technology. Introduction to mechanisms carnegie mellon school of. Procedure for optimum design of a twostage spur gear system. Pressure angle is the angle between the pressure line and common tangent to pitch circles.
Complete the gear design part and draw the layout of gears on 27 march, 2017 z 1 z 2 z 3 z 4 important. Power system protection and switchgear by badari ram, d. Following are the gear terminology or gear terms used in the description of gears. Determine allowable force on gear teeth, including the factors necessary due to.
Calculate forces on teeth of spur gears, including impact forces associated with velocity and clearances. Understanding the contact ratio for spur gears with some. Terms the following terms are associated with gears. In this paper, an optimum design of a twostage spur gear system is performed. Gear design national broach and machine division,of lear siegler, inc. Gear train it is defined as two or more gears are made to mesh with each epicyclic gear train the axes of the shafts over which the gears are mounted, may move relative to a fixed axis. The optimization is based on a multicriterion technique consisting of a minmax method combined with a direct search. They are classified as straight and spiral tooth bevel andhypoid gears as in fig. Yi zhang with susan finger stephannie behrens table of contents. The tooth numbers are n 2 24, n 3 18, n 5 22, and n 6 64. The diametral pitch is, by definition, the number of teeth divided by the pitch diameter. Interference in gear occurs when two gears are in mesh, there is a chance in which the involute portion of gear mate with the noninvolute portion of mating gear. The larger is called the gear regardless of which one is doing the driving.
Comparative size of gear teeth using iso international organization for standardization guidelines, module size is designated as the unit representing gear toothsizes. The circular pitch, therefore, equals the pitch circumference divided by the number of teeth. Dimensional measurements at the required level of accuracy are the essential link between the designers intent and a delivered product. This page lists the standard us nomenclature used in the description of mechanical gear construction and function, together with definitions of the terms. The pitch circle diameter is the diameter of the pitch.
A worm gear drive has a centre distance of 220 mm and a normal. Good designers and engineers have experience and knowledge and the ability to communicate their thoughts and ideas clearly with others. Switchgear and protection notes sgp notes sgp pdf notes. Module 14 3 hr interference and undercutting, minimum number of teeth, contact ratio, bevel helical, spiral and worm gears module 15 3 hr gear trains simple, compound and epicyclic gear trains. 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. Basic gear terminology involute face width is the length of the teeth in the axial direction. The number of teeth of a gear per inch of its pitch diameter. This is a twodimensional case which allows for observation in a plane. Pich circle is the imaginary circle that rolls without slipping with a pitch circle of a mating gear. Find materials for this course in the pages linked along the left. Can you see that the obtuse angle within this triangle is.
Gray cast iron nodular and ductile cast iron good casting property carburizing steel nitride steel bronze nonmetals as plastics, reinforced laminates noiseless operation, cheaper 4. With increase in pitch line velocity, lubricant used should be less viscous in order to min. Im designing a gear driven mechanism, and i need to size the motor, assuming some frictional loss in the gears, so i need the cof. Whats the formula for spur gears to avoid interference.
We can then calculate the numerical value of the contact ratio. The width of a tooth and a space, measured on the pitch circle diametral pitch p. As we proceed from the pinion on the electric motor to the gear on the output shaft, how do the pitch and face width vary. Terminology the gear tooth is a component of a mechanical power transmission system that does not lack for descriptive terminology.
Philosophy of protection, nature, causes and consequences of faults, zone of protection, requirements of a protective scheme, basic terminology components of protection scheme. For the love of physics walter lewin may 16, 2011 duration. Gear design and strength iupital has good strength, durability, wear resistance, and chemical resistance, so can be used to each gear. Gear terminology is a page to learn gear related technical nomenclature for all machine designers. Tribology is also in virtually every area of engineering and industry aerospace agriculture automotive. Smaller gear is known as pinion and larger mating gear is called gear. Spur gear terms and concepts description in order to design, build and discuss gear drive systems it is necessary to understand the terminology and concepts associated with gear systems. 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. The terminology was established by the american gear manufacturers association agma, under accreditation. Gear cutting broaching grinding honing coated abrasive lapping polishing. If the transmission of rotation should occur with a constant ratio, which means that in case of a con. Gears terminology, fundamental law of gearing, involute profile. Planetary gear trains example for the speed reducer shown, the input shaft a is in line with output shaft b. Metal casting processes indian institute of technology.
Spur gear design and selection objectives apply principles learned in chapter 11 to actual design and selection of spur gear systems. Gears may be classified according to the relative position of the axes of revolution. Gear life depends on effective lubrication, which can be quatified by minimum film trajns to r compositeas shown in fig. Nptel textile engineering mechanics of textile machinery. Gear wreck will happen because of its tooth fatigue and tooth surface wear, so strength design from both side is necessary. A gear train is usually made up of two or more gears. Tribology 101 introduction to the basics of tribology. Module 2 gears nptel pages 1 17 text version fliphtml5. Screw thread definition a screw thread is the helical ridge produced by forming a continuous helical groove of uniform section on the external or internal surface of a cylinder or a cone. Switchgear and protection by sunil s rao, khanna publishers. Depending upon the type and accuracy of motion desired, the gears and the profiles of the gear teeth can be. In absence of lubricant additives and antifriction. The distance from the base of a tooth on one side to the base of the opposing tooth on the other side of the gear. Stresses developed by normal force in a photoelastic model of gear tooth as per dolan.
Switchgear and protective devices 2015 3 p a g e syllabus switchgear and protective devices 310 modulei 10 hours protective devices. Gear ratio is numbers of teeth of larger gear to smaller gear. Ratio is the number of teeth on the gear divided by the number of teeth on the pinion. Normal module standard is to be closed to 1dp standard. Lecture notes tribology mechanical engineering mit. Fundamentals of power system protection by paithankar and s. Meshing of mating teeth should occur on the involute portion of teeth. Find the ratio of the output speed to the input speed. It is a basic dimension from which many other features of. Spur gear design nptel indian institute of technology.
1404 1109 1586 42 51 1369 1438 1139 421 1418 750 309 1281 1578 1384 431 1187 990 998 976 497 1384 226 928 76 1303 1244 735 730 548 262 1162 752 183 1446 1104 1224 1459 845 467 275 1481 914 1046 462 953