Fundamentals of kinematics and dynamic of machines and mechanisms / I have taught kinematics and dynamics of machines and mechanisms for many. This is full text of the report of Satish Chandra Committee (), pages in original Kinematics of machines jbk das pdf. This may not be fully legible due to. Hi friends i just have upload an ebook on Kinematics of machinery. I hope it will help you to guide well. let me know if you need more updates.
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Kinematics of Machines for IV Semester - Mechanical Engineering of Vtu by J.b.k Das, , available at Book Depository with free delivery. KINEMATICS OF caite.info - Download as PDF File .pdf), Text File .txt) or read online. KINEMATICS OF caite.info Kinematics Of Machines For 4th Sem Mechanical Eng Vtu by JBK Das, P L Srinivasa Murthy. Tags: vtu, local author, mech kinematics, machinesjbk, das, srinivasa, murthysapna, book, house, (m) Theory of Machines and Mechanisms.
The motion allowed may be rotational revolute joint , translational sliding or prismatic joint , or a combination of the two roll-slide joint. This is four bar mechanism with double crank in which the shortest link is fixed. Language Clear. The ball and socket joint is a spherical pair. This fascinating mechanism converts rotary motion to reciprocating motion in two axis. In other mechanisms.
Whitworth quick return mechanism is an application of third inversion of the single slider crank chain. Quick return mechanisms are used in machine tools to give a slow cutting stroke and a quick return stroke.
Drag link mechanis m: This is four bar mechanism with double crank in which the shortest link is fixed. Quick return mechanis ms: Quick Return Motion Mechanis ms: Many a times mechanisms are designed to perform repetitive operations. The extreme values of the transmission angle occur when the crank lies along the line of frame. Transmission angle. Description of common mechanis ms-Single. During these operations for a certain period the mechanisms will be under load known as working stroke and the remaining period is known as the return stroke.
If the crank AB rotates at a uniform speed. This rotation of link CD is transformed to quick return reciprocatory motion of the ram E by the link CE as shown in figure.
Indexing Mechanis ms. Ratchets are used in feed mechanisms. Shortest link is always stationary link. It is the necessary condition for the drag link quick return mechanism. Rocking Mechanisms: Inte rmittent motion mechanis m: A ratchet and Pawl mechanism consists of a ratchet wheel 2 and a pawl 3 as shown in the figure.
When the lever 4 carrying pawl is raised. Ratchets and escapements. As the pawl lever is lowered the pawl slides over the ratchet teeth. Sum of the shortest and the longest links of the four links 1. Ratchet and Pawl mechanism: This mechanism is used in producing intermittent rotary motion member. One more pawl 5 is used to prevent the ratchet from reversing.
Hence this mechanism finds its use in copying devices such as engraving or profiling machines. Q and P are in a straight line. This is a simple figure of a Pantograph. C and D. Pantograph is used to copy the curves in reduced or enlarged scales. Toggle Mechanism: B moves to Q1. The links are pin jointed at A. Q is a point on the link AD. Link BA is extended to fixed pin O.
Their motions will be proportional to their distance from the fixed point. Let ABCD be the initial position. Then it can be shown that the points P and Q always move parallel and similar to each other over any path straight or curved. It consists of a driving wheel D carrying a pin P which engages in a slot of follower F as shown in figure. C moves to Q1. Suppose if point Q moves to Q1. Geneva mechanis m: Geneva mechanism is an intermittent motion mechanism. During the remaining time of one revo lution of the driver.
During one quarter revolution of the driving plate. D moves to D1 and P to P1 and the new configuration of the mechanism is shown by dotted lines.
Links CD and CE are of same length. When the vehicles steer to the right as shown in the figure. This is done by actually drawing the mechanism to a scale or by calculations.
This is the principle used in toggle mechanism. A toggle mechanism is used when large forces act through a short distance is required.
This can also be used for shaft with angular misalignment where flexible coupling does not serve the purpose. Therefore for different value of the corresponding value of and are tabulated. The figure below shows a toggle mechanism. In an Ackermann steering gear mechanism.
The ratio of the crank movement to the slider movement approaching infinity is proportional to the mechanical advantage. It is commonly known as Universal joint. The fundamental equation for correct steering is. In slider crank mechanism as the crank approaches one of its dead centre position.
Ackermann steering gear mechanis m: This mechanism is made of only turning pairs and is made of only turning pairs wear and tear of the parts is less and cheaper in manufacturing. In Europe it is called as Cardan joint. The crescent shaped cut out in dark orange section lets the points of the cross past.
Notice that the handle traces out an ellipse rather than a circle. By varying the angle of the crank piece it can be used to change the angle of movement from 1 degree to degrees. A similar mechanism is used in ellipse drawing tools. This mechanism is used to convert between rotary motion and reciprocating motion. In all other positions pure rolling is not obtainable.
The bell crank is used to convert the direction of reciprocating movement. The Geneva stop mechanism is used commonly in film cameras. Notice how the speed of the.
Three correct steering positions will be: The Geneva stop is used to provide intermittent motion. This fascinating mechanism converts rotary motion to reciprocating motion in two axis. The Geneva stop is named after the Geneva cross.
It reaches maximum speed in the middle of its travel then gradually slows down until it reaches the end of its travel. For each complete turn of the worm shaft the gear shaft advances only one tooth of the gear. Ratchets are also used in the freewheel mechanism of a bicycle.
The rack is the flat. Rack and pinion can convert from rotary to linear of from linear to rotary. The part used to move the ratchet is known as the pawl. In the rack and pinion railway a central rack between the two rails engages with a pinion on the engine allowing the train to be pulled up very steep slopes. The diameter of the gear determines the speed that the rack moves as the pinion turns. As the speed is reduced the power to the drive increases correspondingly.
Unlike ordinary gears. A worm is used to reduce speed.
Ideal for use with small electric motors. The piston starts from one end. The ratchet can be used as a way of gearing down motion. Rack and pinion gears give a positive motion especially compared to the friction drive of a wheel in tarmac. Ratchets are also used to ensure that motion only occurs in only one direction.
The rack and pinion is used to convert between rotary and linear motion. By its nature motion created by a ratchet is intermittent. Rack and pinions are commonly used in the steering system of cars to convert the rotary motion of the steering wheel to the side to side motion in the wheels. By using two pawls simultaneously this intermittent effect can be almost.
The ratchet can be used to move a toothed wheel one tooth at a time. Worm gears are a compact. Notice that as the blue gear turns clockwise the orange gear turns anti-clockwise. The balance wheel. A fine pointed follower will more accurately trace the outline of the cam. It is the escapement which divides the time into equal segments.
This is deliberate.
In this common design high pressure steam is pumped alternately into one side of the piston. In the example above the blue gear has eleven teeth and the orange gear has twenty five. This more accurate movement is at the expense of the strength of the cam follower. Cam follower design is important in the way the profile of the cam is followed.
The reciprocating motion of the piston is converted to useful rotary motion using a crank. The motion created can be simple and regular or complex and irregular. As the cam turns. In the above example the number of teeth on the orange gear is not divisible by the number of teeth on the blue gear. Steam engines were the backbone of the industrial revolution. If the orange gear had thirty three teeth then every three turns of the blue gear the same teeth would mesh together which could cause excessive wear.
The watch escapement is the centre of the time piece. Cams are used to convert rotary motion into reciprocating motion. By using none divisible numbers the same teeth mesh only every seventeen turns of the blue gear. Gears are used to change speed in rotational movement. The power comes through the escape wheel which gives a small 'kick' to the palettes purple at each tick.
Straight line generators. Exact straight line motion mechanis m. PB and BQ of equal length to the fixed pin A. Peaucillier mechanism: The pin Q is constrained to move long the circumference of a circle by means of the link OQ. This is also a four bar chain.
The link OQ and the fixed link are equal in length.
Peaucellier mechanism. Hart mechanism. The best position for O may be found by making use of the instantaneous centre of QR. Scott Russell mechanism 2. The pins P and Q are on opposite corners of a four bar chain which has all four links QC. Design of Crank-rocke r Mechanis ms: Straight Line Motion Mechanisms: The easiest way to generate a straight line motion is by using a sliding pair but in precision machines sliding pairs are not preferred because of wear and tear.
Peaucillier mechanism b. In this animation the oval crank has been made transparent so that you can see how the control valve crank is attached. Approximate straight line motion mechanisms a. As the large wheel the fly wheel turns a small crank or cam is used to move the small red control valve back and forth controlling where the steam flows. Watt mechanism. Hence in such cases different methods are used to generate straight line motion mechanisms: Since AB and BP are links of a constant length.
Therefore the point P traces out a straight path normal to AR. Imagine yourself standing at the center of a merry. In this way. In a direction perpendicular to the link Coriolis Acceleration: The absolute velocity of any point on a mechanism is the velocity of that point with reference to ground.
Perhaps the most confusing of these is the coriolis acceleration. This is the coriolis acceleration. A slider attached to a rotating link such that the slider is moving in or out along the link as the link rotates experiences all 4 components of acceleration. A slider attached to ground experiences only sliding acceleration. Velocity and acceleration analysis by complex numbers: Analysis of single slider crank mechanism and four bar mechanism by loop closure equations and complex numbers.
In a direction perpendicular to the link Sliding Acceleration: The velocity of a point on a moving link relative to the p ivot of the link is given by the equation: The total acceleration of that point is the vector sum of the components. Coriolis component of acceleration. The total acceleration of a point is the vector sum of all applicable acceleration components: Velocity and acceleration analysis by vector polygons: Relative velocity and accelerations of particles in a common link.
Points toward the center of rotation Tangential Acceleration: Important Concepts in Velocity Analysis 1. Even though you are walking at a constant speed and the merry-go-round is spinning at a constant speed. Relative velocity describes how one point on a mechanism moves relative to another point on the mechanism. In the direction of sliding. A rotating link will produce normal and tangential acceleration components at any point a distance. Acceleration Components Normal Acceleration: In what direction did your speed increase?
This is the direction of the coriolis acceleration. One should be able to form a closed triangle for a 4-bar that shows the vector equation: The basic steps are these: The vector. Plot all other velocity vector directions. This is a vector that originates at the zero velocity point and runs perpendicular to the link to show the direction of motion. Coriolis Acceleration: Velocity Analysis of Four Bar Mechanis ms: Problems solving in Four Bar Mechanisms and additional links.
Coincident points. Kinematic analysis by Complex Algebra methods: A point on a grounded link such as point B will produce an absolute velocity vector passing through the ze ro velocity point and perpendicular to the link.
Vector Approach: This vector will be perpendicular to the link AB and pass through the reference point A on the velocity diagram. Velocity and Acceleration polygons: Graphical velocity analysis: It is a very short step using basic trigonometry with sines and cosines to convert the graphical results into numerical results. A point on a floating link such as B relative to point A will produce a relative velocity vector.
In a direction perpendicular to the link. Velocity Analysis of Slider Crank Mechanis ms: Problems solving in Slider Crank Mechanisms and additional links. Acceleration Analysis of Four Bar Mechanisms: Plot your known linkage velocities on the velocity plot. Set up a velocity reference plane with a point of zero velocity designated.
Graphical Method. A linkage that is rotating about ground gives an absolute velocity. Acceleration Analysis of Slider Crank Mechanis ms: Computer applications in the kinematic analysis of simple mechanis ms: Computer programming for simple mechanisms Use the equation. This is the motion constraint type that we will focus upon.
Oscilllating rotating. Type of followers. Layout of plate cam profiles: Uniform acceleration and retardation and Cycloidal motion. Velocity and acceleration time curves for cam profiles. Critical path motion — The path by which the follower satisfies a given motion is of interest in addition to the extreme positions.
Uniform velocity. Force closed. Types of motion constraints: Critical extreme position — the positions of the follower that are of primary concern are the extreme positions. This is a more difficult and less common design problem. Disc cam with reciprocating fo llower having knife edge. This motion is specified through the use of SVAJ diagrams diagrams that describe the desired displacement-velocity-acceleration and jerk of the follower motion Type of cams.
Simple harmonic and Cycloidal motions: Describing the motion: A cam is designed by considering the desired motion of the follower. Displacement diagrams Cam Terminology: Physical components: Follower motions including SHM.
Drawing the displacement diagrams for the different kinds of the motions and the plate cam profiles for these different motions and different followers. Uniform acceleration and retardation and Cycloidal motions Knife-edge.
Circular arc and Tangent cams: Circular arc Tangent cam High speed cams: High speed cams Standard cam motion: Simple Harmonic Motion Uniform velocity motion Uniform acceleration and retardation motion Cycloidal motion Pressure angle and undercutting: Pressure angle Undercutting.
Derivatives of Followe r motion: Velocity and acceleration of the followers for various types of motions. Calculation of Velocity and acceleration of the followers for various types of motions. Spur gear Terminology and definitions: Spur Gears: External Internal Definitions Inte r changeable gears. Fundame ntal Law of toothed gearing and Involute gearing: Inter changeable gears Gear tooth action Terminology Non standard gear teeth: Inte rference and undercutting: Interference in involute gears Methods of avoiding interference Back lash Notice that as the blue gear turns clockwise the orange gear turns anticlockwise.
For example. Compound Gear Trains — A compound gear train is a train where at least one shaft carries more than one gear. A simple gear train will typically have 2 or 3 gears and a gear ratio of If the train has 3 gears. Parallel axis gear trains: Simple Gear Trains — A simple gear train is a collection of meshing gears where each gear is on its own axis. The train ratio for a simple gear train is the ratio of the number of teeth on the input gear to the number of teeth on the output gear.
Gear trains: Gear Train Basics The velocity ratio. To enable the rear wheels to revolve at the same speeds when going straight. Problems in epicyclic gear trains. A common approach to the design of compound gear trains is to first determine the number of gear reduction steps needed each step is typically smaller than Reverted Gear Trains — A reverted gear train is a special case of a compound gear train.
To enable the rear wheels to revolve at different speeds when negotiating a curve. Proble m: Epicyclic gear trains: If the axis of the shafts over which the gears are mounted are moving relative to a fixed axis.
Assuming no idler gears are used. Once this is done. Used in the rear axle of an automobile. A reverted gear train has the input and output shafts in —line with one another.
Surface contacts: Basic laws of friction Pivot and collar. Friction drives: Friction drives Positive drives and Slip drives Speed ratio Problems on conical pivot. Friction in scre w threads: Friction in screw and nut Friction in screw jack Problems in screw jack.
Problem on flat pivot. Sliding and Rolling friction: Sliding contact bearings Rolling contact bearings Problems in bearings Friction aspects in Brakes: Friction in vehicle propulsion and braking: Login Please enter your login details.
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