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 musicmarkup.info - Download as PDF File .pdf), Text File .txt) or read online. KINEMATICS OF musicmarkup.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.
Path traced 2 2 2 2 by mid-point of PQ is a circle. Scotch yoke mechanism: This mechanism, the slider P is fixed. When PQ rotates above P, the slider Q reciprocates in the vertical slot. The mechanism is used to convert rotary to reciprocating mechanism. If one block is turning through an angle, the frame and the other block will also turn through the same angle. It is shown in the figure below. An application of the third inversion of the double slider crank mechanism is Oldhams coupling shown in the figure.
Gupta , S.
Chand publication 2. Theory of machines P. Ballaney , Khanna publication 3. Bansal ,Laxmi publication 7. Marks Time: 3Hrs Note : 1. Question No. Answer any two full questions from each of the remaining sections 3. Any missing data may be suitably assumed 1. Give its applications. It is subjected to a load of 30 KN. The angle of the cone is degree and the co-efficient of friction is 0. Find the power lost in friction, when the speed is rpm, assuming uniform pressure condition. Let ABCD be the initial position.
Suppose if point Q moves to Q1 , then all the links and the joints will move to the new positions such as A moves to A1 , B moves to Q1, C moves to Q1 , D moves to D1 and P to P1 and the new configuration of the mechanism is shown by dotted lines.
Toggle Mechanism: In slider crank mechanism as the crank approaches one of its dead centre position, the slider approaches zero. The ratio of the crank movement to the slider movement approaching infinity is proportional to the mechanical advantage.
This is the principle used in toggle mechanism. A toggle mechanism is used when large forces act through a short distance is required. The figure below shows a toggle mechanism. Links CD and CE are of same length. Hookes joint: Hookes joint used to connect two parallel intersecting shafts as shown in figure.
This can also be used for shaft with angular misalignment where flexible coupling does not serve the purpose. Hence Hookes joint is a means of connecting two rotating shafts whose axes lie in the same plane and their directions making a small angle with each other. It is commonly known as Universal joint. In Europe it is called as Cardan joint. 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.
When the vehicles steer to the right as shown in the figure, the short link BL is turned so as to increase , where as the link LK causes the other short link AK to turn so as to reduce.
For different angle of turn , the corresponding value of and Cot Cos are noted.
This is done by actually drawing the mechanism to a scale or by calculations. Therefore for different value of the corresponding value of and are tabulated. In an Ackermann steering gear mechanism, the instantaneous centre I does not lie on the axis of the rear axle but on a line parallel to the rear axle axis at an approximate distance of 0.
Three correct steering positions will be: 1 When moving straight. In all other positions pure rolling is not obtainable. The bell crank is used to convert the direction of reciprocating movement. By varying the angle of the crank piece it can be used to change the angle of movement from 1 degree to degrees. The Geneva stop is used to provide intermittent motion, the orange wheel turns continuously, the dark blue pin then turns the blue cross quarter of a turn for each revolution of the drive wheel.
The crescent shaped cut out in dark orange section lets the points of the cross past, then locks the wheel in place when it is stationary. The Geneva stop mechanism is used commonly in film cameras.
Notice that the handle traces out an ellipse rather than a circle. A similar mechanism is used in ellipse drawing tools. Notice how the speed of the piston changes. The piston starts from one end, and increases its speed. It reaches maximum speed in the middle of its travel then gradually slows down until it reaches the end of its travel. The rack is the flat, toothed part, the pinion is the gear. Rack and pinion can convert from rotary to linear of from linear to rotary.
The diameter of the gear determines the speed that the rack moves as the pinion turns. 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.
Rack and pinion gears give a positive motion especially compared to the friction drive of a wheel in tarmac. 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 part used to move the ratchet is known as the pawl. The ratchet can be used as a way of gearing down motion. By its nature motion created by a ratchet is intermittent.
By using two pawls simultaneously this intermittent effect can be almost, but not quite, removed. Ratchets are also used to ensure that motion only occurs in only one direction, useful for winding gear which must not be allowed to drop. Ratchets are also used in the freewheel mechanism of a bicycle. For each complete turn of the worm shaft the gear shaft advances only one tooth of the gear.
In this case, with a twelve tooth gear, the speed is reduced by a factor of twelve. Also, the axis of rotation is turned by 90 degrees. Unlike ordinary gears, the motion is not reversible, a worm can drive a gear to reduce speed but a gear cannot drive a worm to increase it. As the speed is reduced the power to the drive increases correspondingly. Worm gears are a compact, efficient means of substantially decreasing speed and increasing power.
Ideal for use with small electric motors. It is the escapement which divides the time into equal segments. The balance wheel, the gold wheel, oscillates backwards and forwards on a hairspring not shown as the balance wheel moves the lever is moved allowing the escape wheel green to rotate by one tooth. The power comes through the escape wheel which gives a small 'kick' to the palettes purple at each tick. In the example above the blue gear has eleven teeth and the orange gear has twenty five.
Notice that as the blue gear turns clockwise the orange gear turns anti-clockwise. In the above example the number of teeth on the orange gear is not divisible by the number of teeth on the blue gear. This is deliberate. 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. By using none divisible numbers the same teeth mesh only every seventeen turns of the blue gear.
CAMS: Cams are used to convert rotary motion into reciprocating motion. The motion created can be simple and regular or complex and irregular.
As the cam turns, driven by the circular motion, the cam follower traces the surface of the cam transmitting its motion to the required mechanism. Cam follower design is important in the way the profile of the cam is followed. A fine pointed follower will more accurately trace the outline of the cam.
This more accurate movement is at the expense of the strength of the cam follower. Steam engines were the backbone of the industrial revolution. In this common design high pressure steam is pumped alternately into one side of the piston, then the other forcing it back and forth. The reciprocating motion of the piston is converted to useful rotary motion using a crank. 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.
In this animation the oval crank has been made transparent so that you can see how the control valve crank is attached. Straight line generators, 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.
Hence in such cases different methods are used to generate straight line motion mechanisms: 1.
Exact straight line motion mechanis m. Peaucellier mechanism, b. Hart mechanism, c. Scott Russell mechanism 2. Approximate straight line motion mechanisms a. Watt mechanism, b. Grasshoppers mechanism, c. Roberts mechanism, d. Tchebicheffs mechanism a. Peaucillier mechanism : The pin Q is constrained to move long the circumference of a circle by means of the link OQ.
The link OQ and the fixed link are equal in length.
Therefore the point P traces out a straight path normal to AR. Robe rts mechanis m: This is also a four bar chain. The best position for O may be found by making use of the instantaneous centre of QR. The path of O is clearly approximately horizontal in the Roberts mechanism. Peaucillier mechanism b.
Velocity and acceleration analysis by complex numbers: Analysis of single slider crank mechanism and four bar mechanism by loop closure equations and complex numbers. Displacement, velocity and acceleration analysis in simple mechanis ms : Important Concepts in Velocity Analysis 1.
The absolute velocity of any point on a mechanism is the velocity of that point with reference to ground. 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, r, from the rotational pivot of the link. The total acceleration of that point is the vector sum of the components.
A slider attached to ground experiences only sliding 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. Perhaps the most confusing of these is the coriolis acceleration, though the concept of coriolis acceleration is fairly simple. Imagine yourself standing at the center of a merry- go-round as it spins at a constant speed.
Even though you are walking at a constant speed and the merry-go-round is spinning at a constant speed, your total velocity is increasing because you are moving away from the center of rotation i. This is the coriolis acceleration. In what direction did your speed increase? This is the direction of the coriolis acceleration. In this way, the x and y components of the total acceleration can be found. Graphical Method, 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.
The basic steps are these: 1. Set up a velocity reference plane with a point of zero velocity designated. Plot your known linkage velocities on the velocity plot. A linkage that is rotating about ground gives an absolute velocity. This is a vector that originates at the zero velocity point and runs perpendicular to the link to show the direction of motion. The vector, VA, gives the velocity of point A.
Plot all other velocity vector directions. 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. A point on a floating link such as B relative to point A will produce a relative velocity vector.