In absence of lubricant additives and antifriction. Spur gear creation american society for engineering. 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. Many of the everyday mechanisms and devices we commonly use contain gear wheels. This page lists the standard us nomenclature used in the description of mechanical gear construction and function, together with definitions of the terms.
Gears terminology, fundamental law of gearing, involute profile. Lecture notes tribology mechanical engineering mit. Good designers and engineers have experience and knowledge and the ability to communicate their thoughts and ideas clearly with others. 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. Download pdf gear technology a new bevel gear cutting machine, a fuljload.
Smaller gear is known as pinion and larger mating gear is called gear. 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. Calculate forces on teeth of spur gears, including impact forces associated with velocity and clearances. Find materials for this course in the pages linked along the left. Gears are machine elements that transmit motion by means of successively engaging teeth.
A gear train is usually made up of two or more gears. Ratio is the number of teeth on the gear divided by the number of teeth on the pinion. Comparative size of gear teeth using iso international organization for standardization guidelines, module size is designated as the unit representing gear toothsizes. The number of teeth of a gear per inch of its pitch diameter. 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. Terms the following terms are associated with gears. The optimization is based on a multicriterion technique consisting of a minmax method combined with a direct search. 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 diametral pitch is, by definition, the number of teeth divided by the pitch diameter. It is a basic dimension from which many other features of. Functions of a gear power transmission change rotational speedtorque maintain constant speed ratio me 338. This is a twodimensional case which allows for observation in a plane.
Find the ratio of the output speed to the input speed. Meshing of mating teeth should occur on the involute portion of teeth. Complete the gear design part and draw the layout of gears on 27 march, 2017 z 1 z 2 z 3 z 4 important. Terminology the gear tooth is a component of a mechanical power transmission system that does not lack for descriptive terminology. J s campbell, principles of manufacturing materials and processes. Switchgear and protection notes sgp notes sgp pdf notes. A separate part of the mould, made of sand and generally baked, which is used to create openings and. Spur gear design nptel indian institute of technology. With increase in pitch line velocity, lubricant used should be less viscous in order to min. Switchgear and protective devices 2015 3 p a g e syllabus switchgear and protective devices 310 modulei 10 hours protective devices. Page 2 page 2 basics terms a gear is a set of toothed wheels gear wheels or cogwheels that work together to transmit movement. Gears may be classified according to the relative position of the axes of revolution. Stresses developed by normal force in a photoelastic model of gear tooth as per dolan.
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 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. Understanding the contact ratio for spur gears with some. Whats the formula for spur gears to avoid interference. 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. 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. Procedure for optimum design of a twostage spur gear system. A toothed gear must have an integral number of teeth. The larger is called the gear regardless of which one is doing the driving. 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. Tribology is also in virtually every area of engineering and industry aerospace agriculture automotive. Philosophy of protection, nature, causes and consequences of faults, zone of protection, requirements of a protective scheme, basic terminology components of protection scheme. Switchgear and protection by sunil s rao, khanna publishers.
Fundamentals of power system protection by paithankar and s. Introduction to gear trainsintroduction to gear trains. 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. 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. Normal module standard is to be closed to 1dp standard. Following are the gear terminology or gear terms used in the description of gears. In this paper, an optimum design of a twostage spur gear system is performed. Module 2 gears nptel pages 1 17 text version fliphtml5. The width of a tooth and a space, measured on the pitch circle diametral pitch p. 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. Gear design national broach and machine division,of lear siegler, inc. They are classified as straight and spiral tooth bevel andhypoid gears as in fig.
Basic gear terminology involute face width is the length of the teeth in the axial direction. In order to overcome this there are many methods to avoid gear tooth interference su. Unit 6 gear generation and finishing gear generation. Gear terminology is a page to learn gear related technical nomenclature for all machine designers. 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. Gear design and strength iupital has good strength, durability, wear resistance, and chemical resistance, so can be used to each gear. Introduction to mechanisms carnegie mellon school of. Depending upon the type and accuracy of motion desired, the gears and the profiles of the gear teeth can be. 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. Planetary gear trains example for the speed reducer shown, the input shaft a is in line with output shaft b. Lecture gear unit design failure of gear tooth probable dynamic load and wear load.
Stadtfeld introduction the most basic case of a gear train is the transmission of rotation and power between two parallel shafts. Yi zhang with susan finger stephannie behrens table of contents. Power system protection and switchgear by badari ram, d. Gear cutting broaching grinding honing coated abrasive lapping polishing. Pressure angle is the angle between the pressure line and common tangent to pitch circles. Nptel textile engineering mechanics of textile machinery. Determine allowable force on gear teeth, including the factors necessary due to. If the transmission of rotation should occur with a constant ratio, which means that in case of a con. 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. Spur gear design and selection objectives apply principles learned in chapter 11 to actual design and selection of spur gear systems. 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.
Gear ratio is numbers of teeth of larger gear to smaller gear. Gear size, pressure angle, number of teethwe introduce the basic terminology, measurement, and relational expressions necessary to understand basic gear technology. A worm gear drive has a centre distance of 220 mm and a normal. Gear life depends on effective lubrication, which can be quatified by minimum film trajns to r compositeas shown in fig. The pitch circle diameter is the diameter of the pitch.
The terminology was established by the american gear manufacturers association agma, under accreditation. When gear sets are visualized as a pair of smooth contacting. Important casting terms nptel course on manufacturing processes i, pradeep kumar et al. Metal casting processes indian institute of technology. The tooth numbers are n 2 24, n 3 18, n 5 22, and n 6 64. Tribology 101 introduction to the basics of tribology. Gear wreck will happen because of its tooth fatigue and tooth surface wear, so strength design from both side is necessary. We can then calculate the numerical value of the contact ratio.
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