In A Sliding Pair Minimum Number Of Degree Of Freedom

In a sliding pair minimum number of degree of freedom is only one. 2)Turning pair. In a turning pair also degree of freedom is one.when two links are connected such that one link revolves around another link it forms a turning pair. 3)Cylindrical pair. In a cylindrical pair degree of freedom is two.If one link turns and slides along another link it forms a cylindrical pair. 4)Rolling pair. In a rolling pair degree of freedom is two.The object moves both linearly and angularly. 5)Spherical pair. In a spherical pair degree of freedom is three.It can both move left and right,up and down,and rotate along the same point. (b)Based on nature of contact. 1)Lower pair. If contact between two links is surface contact also having degree of freedom one, then the pair is known as lower pair. Example: Sliding pair. 2)Higher pair. If contact between two links is either point contact or line contact then the pair is known as higher pair. Example: Point contact-Rolling pair. Line contact-Cylindrical pair. 3)Mechanical pair. (a)Open pair. In this pair everything is open to the admosphere. (b)Closed pair. In this pair everything is closed from the admosphere. (B)Indexing mechanism. This type of mechanism is used in automatic lathe’s etc. Assume one revolution of the driver.In 360 degrees,270 degrees makes locking of follower. Remaining 90 degrees is used to make rotation of the follower. 2)Snap action mechanism. It is used in calling bells, bicycle bells etc. 3)Motion adjustment mechanism. The mechanism used to adjust or modify any one of the links in a mechanism is known as motion adjustment mechanism. Differential screw used in bench vice, pipe wrench, Lathe chuck and screw jack are some of the examples of motion adjustment mechanism. 4)Scott Russel mechanism. This is one of the mechanism to produce straight line motion mechanism.The mechanism in which the straight line is copied from a existing straight line constrain is known as Scott Russel mechanism. 3) Explain the different types of quick return motion mechanism? Quick return motion are of two types.They are, 1)Crank and slotted lever quick return motion mechanism. 2)Whitworth quick return motion mechanism Crank and slotted lever quick return motion mechanism. In this mechanism,the link AC forming the turning pair is fixed.The driving crank CB revolves with uniform angular speed about the fixed center C.A sliding block attached to the crank pin at B slides along the slotted bar AP and thus causes AP to oscillate about the pivorted point A.A short link PR transmits the motion from AP to ram which carries the tool and reciprocates along the line of stroke perpendicular to CD.When the driving crank CA moves from the position CA

This is the equation of a circle of radius AP.

4) Explain (i) the different types of joints (ii) Inversion of four bar kinetic chain (ii) Inversion of Basic Single Slider Crank Chain

(i) The different types of joints are

a. Binary Joint b. Ternary Joint c. Quaternary Joint a) Binary Joint If two links are connected at the same junction it is called binary joint. Illustration: In the above figure ( kinetic Chain) Number of binary joints j = 4 L = 2/3 (j+2) L = 4 4=2/3 (6) 4=4 L.H.S. = R.H.S. It is a kinetic chain based on Kline’s equation. b) Ternary Joint (i) If three are connected to the same junction, then is known ternary joint (ii) One ternary joint is equivalent to two binary joints. Illustration: In the fig: No of binary joints = A+B+C = 3 Number of Ternary joints = C+E Equivalent binary joints = 2+2 = 4 Hence total number of binary joints = 3 + 4 = 7 Based on Kline’s Equation L = 2/3 (J+2) 6 = 2/3 (9) 6=6 Hence is a Kinematic Chain. c) Quaternary Joint If four links are connected to the same joint then it is a Quaternary joint. One quaternary joint = Three binary joints In the figure Number of binary joint C = 1 Number of ternary joints = A + B + E + F Equivalent binary joints = 8 Number of quaternary joints = D, G Equivalent binary joints = 6, Total Number of Equivalent binary joints J = 15 Based on Kline’s equation L = 2/3 (I+2) 11 = 2/3 (17) L.H.S. ≠ R.H.S Hence it is not a kinematics chain In the figure if the link (DG) is deleted then it would be a kinematic chain. The chain is represented as 5) Inversion of four Bar Kinematic Chain

The inversions of four bar kinematic chain are as follows a) Beam Engine: i) This is also known as crank and lever mechanism. Link (1) Frame Link (2) Crank Link (3) Connecting rod Link (4) lever arrangement Link (5) Piston ii) In this mechanism one link oscillated while the other rotates about fixed link. iii) It is used to convert the rotary motion into reciprocating motion. b) Coupling Rod of Locomotive i) This is also known as Double Crank mechanism. Since both cranks rotate about the points in the fixed link. ii) It consists of four links iii) The opposite links are equal in length, iv) Links (1) and (3) work as two cranks v) This motion is also known as rotary – rotary converter. c) Watt’s Indicator Mechanism: E i) This mechanism was invented by Watt for his steam Engine to guide the position rod. ii) It is also known as simple indicator. iii) It is also known as double lever mechanism iv) Links BC and DEF work as levers whose displacement is directly proportional to steam or gas pressure.ngine Wheel MODULE -3 KINAMATICS OF CAMS

TWO MARKS :1.What is cam ?

Cam is a rotating mechanical member used for transmitting desired motion to a follower by direct contact 2.Classification of cam? (i) according to cam shape (ii) according to follower movement (iii) according to manner of constraint of the follower 3.Classify cam based on a shape ? (i) wedge cam (ii) radial cams (iii) spiral cams (iv) drum cams (v) spherical cams 4.classification of follower ? (i) According to follower shape (ii)according to motion of follower 5.What is roller follower? In place of a knife edge roller is provided at the contacting end of the follower 6.Spherical follower ? In the contacting end of the follower is of spherical shape . 7.Angle of ascend ? The angle of rotation of the cam from the position when the follower begins to rise till it reaches its highest points . it is d HQRWHGE\ 8. Angle of descend? The angle through which the cam rotates during the time the follower returns to the

LQLWLDOSRVLWLRQ,WLVGHQRWHGE\ U 9.Angle of dwell? It is the angle through which the cam rotates while the follower remains stationary at the highest or the lowest . 10. Angle of action ? The total angle moved by the cam during its rotation between the beginning of rise and the end of return of the follower 11.What is radial or disc cams? In radial cams the follower reciprocates or oscillates in a direction perpendicular to the cam axis . The cams are all radial rams. In actual practice, radial cams are widely used due to their simplicity and compactness. 12.What is dwell? The zero displacement or the absence of motion of the follower during the motion of the cam is called dwell. 13. What is classification of followers according to follower shape? (i) Knife edge follower (ii) Roller follower (iii) Mushroom or flat faced follower and (iv) Spherical faced or curved shoe follower 14.What is classification of follower according to the motion of the follower? (i) Reciprocating or translating follower (ii) Oscillating or rotating follower 15.What is classification of followers according to the path of motion ? (i) Radial follower and (ii) Offset follower 16.What are the motion of the follower ? The follower can have any of the following four types of motions (i) Uniform velocity (ii) Simple harmonic motion (iii) uniform acceleration and retardation (iv) cycloidal motion. 17.What is the application of cam? Closing and opening of inlet and exit value operating in IC engine . 18.What are the necessary elements of a cam mechanism? (i) Cam-The driving member is known as the cam (ii) Follower-The driven member is known as the follower. (iii) Frame-It supports the cam and guider the follower. 19.What is translating angle? The wedge is replaced by a flat plate with a groove . The plate cam moves back and forth imparting a translatory motion to the follower. Thus these cams are also known as translating cams. 16 MARKS :- BRIEF ANSWERS

(1) A cam rotating clockwise at a uniform speed of 1000 r.p.m Is required to give a roller follower the motion defined below : 1.Follower to move outwards through 50mm during 120 of cam rotation 2. Follower to dwell for next 60 of cam rotation 3. Follower to return to its standing position during next 90 of cam rotation 4. Follower to dwell for the next of the cam rotation The minimum radius of the cam is 50 mm and the diameter of roller is comm. . The line of stroke of the follower is offset by 20mm from the axis of the cam shaft . If the displacement of the follower takes place with uniform and equal acceleration and retardation of both the

outward and return stoke draw profile of the cam and find the maximum velocity and acceleration during outstroke and return stroke.(16) Displacement diagram(8) Draw a rectangular block of length 18cm breath 50cm Divided the block for forward dwell of return stroke Divide forward and return stroke to equal halves. Join the diagonal of the forward and return stroke block and mark the mid points Then divide the c4ntre line in to six equal parts the remain four and in to with divide in and that corresponding points are marked Join all the points Offset type;(8) Draw a circle of radius of 50mm and a roller of diameter of 10mm on the centre Now draw another circle join center of the roller Join them tangentially and then transfer the points from the displacement diameter to here . Take the degree for forward dwell and out stroke and divide the form and latter to six equal parts. MODULE -4 GEARS & CLUTHES TWO MARKS :1. Define spur gear.

A spur gear is a cylindrical gear whose tooth traces are straight line generation of the reference cylinder. They are used to transmit rotary motion between parallel shafts.

2 . Define addendum and dedendum.

Addendum is the radial distance of a tooth from the pitch circle to the top of the tooth. Dedendum is the radial distance of a tooth from the pitch circle to the bottom of the tooth.

3. Define circular pitch . It is the distance measured on the circumference of the pitch circle from a point of one tooth to the corresponding point on the next tooth. It is denoted by Pc Circular pitch Pc= Π /DT Where D = Diameter of pitch circle. T = Number of teeth on the wheel. 4 . Define I) path of contact. II) Length of path of contact. Path of contact : It is the path traced by the point of contact of two teeth from the beginning to the end of engagement. Length of path of contact : It is the length of common normal cut- off by the addendum circles of the wheel and pinion.

5. State the law of gearing.

Law of gearing states that, the common normal at the point of contact between a pair of teeth must always pass through the pitch point.

6. Define conjugate action . When the tooth profiles are so shaped so as to produce a constant angular velocity ratio during Meshing, then the surface are said to de conjugate.

7. Define angle of approach . The angle of approach is defined as the angle through which a gear rotates from the instant a pair of teeth comes into contact until the teeth are in contact at the pitch point.

8 . List out the characteristics of in volute action. a) Arc of contact. b) Length of path of contact. c) Contact ratio.

9. Define contact ratio.

Contact ratio is defined as the ratio of the length of arc of contact to the circular pitch athematically. Contact ratio = length of arc of contact

Pc Where Pc = circular path.

10 . What is the advantage of in volute gear? The most important advantage of involutes gear is that the center distance for a pair of involute gears can be varied within limits without changing the velocity ratio.

11. What are the conditions to be satisfied for interchangeability of all gears. For interchangeability of all gears, the set must have the same circular pitch, module, diameter pitch, pressure, angle, addendum and dedendum and tooth thickness must be one half of the circular pitch.

12. Define gear tooth system.

A tooth system is a standard which specifies the relationship between addendum, dedendum, working depth, tooth thickness and pressure angle to attain interchangeability of gears of tooth numbers but of the same pressure angle and pitch

13.

Define cycloid.

A cycloid is the curve traced by a point on the circumference of a circle which rolls without slipping on a fixed straight line.

14. Define clearance.

The amount by which the dedendum of a gear exceeds the addendum of the mating gear is called clearance.

15. When in volute interference occurs . If the teeth are of such proportion that the beginning of contact occurs before the interference point is met then the involute proportion of the driven gear will mate a non in volute portion of the driving gear and involute interference is said to occur.

16. What is the principle reason for employing non standard gears? a) To eliminate the undercutting. b) To prevent interference. c) To maintain reasonable contact ratio.

17. What are the advantages and disadvantages of gear drive. Advantages: a) It transmits exact velocity ratio. b) It has high efficiency. Disadvantages: a) The manufacture of gears require special tool and equipment. b) The error in cutting teeth may cause vibrations and noise during operation. 18. Define helix angle ( β ).

It is the angle between the line drawn through one of the teeth and the center line of the shaft on which the gear is maintained.

19. Define gear ratio. The quotient of the number of teeth on the wheel divided by the number of threads on the worm.

20. Define gear train. A combination of gears that is used for transmitting motion from one shaft to another

shaft is known as gear train. E.g. spur gear, spiral gear.

21 . Define velocity ratio. Velocity ratio of a simple gear train is defined as the ratio of the angular velocity of the first gear in the train to the angular velocity of the last gear.

22 . Define epicycles gear train. In a gear train when the axes of shafts over which the gears are mounted move relative to a fixed axis is called epicyclic gear train. . 23. List out the function of differential gear used in the rear drive of an automobile.

a) To transmit motion from the engine shaft to the rear driving wheels b ) To rotate the rear wheel of different speeds while the automobile is taking a turn. b) c) 24. d) Define bevel gears. e) f) The gears which are used to connect shafts whose axes of rotation intersect are called g) bevel gears. h) i) 25. j) Define limited slip differential.

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The coupling unit which is sensitive to wheel speed causes most of the torque to be l) directed to the slow moving wheel. This combination is called limited slip m) differentia MODULE –5 FRICTION TWO MARKS :-

1. Define clutch. Clutch is a transmission device of an automobile which is used to engage and disengage the power from the engine to the rest of the system. 2. What are the types of friction clutches? Types of friction clutches are: *Disc or plate clutches. *Cone clutches. *Centrifugal clutches. 3. Define centrifugal clutch. Centrifugal clutch is being increasingly used in automobile and machines obviously it works on the principle of centrifugal force. 4. What are the types of flat drives? The types of flat drives are: *Compound belt drive. *Stepped or cone pulley drive. *Fast and loose pulley. 5. Define slip. Slip is defined as the relative motion between the belt and pulley. 6. Define law of belting. Law of belting states that the centre line of the belt, as if approaches the pulley lie in a plane perpendicular to the axis of that pulley or must lie in the plane of the pulley otherwise the belt will run off the pulley. 7. Rope drive: Utility. The rope drives are widely used when large power is to be transmitted continuously from one pulley to another over a considerable distance. One advantage of rope drives is that a number of separate driver may be from the driving pulley. 8. Belt drive: Utility.

Belt drive is commonly used for transmission of power when exact velocity ratio is not required. Generally, belt drives are used to transmit power from one pulley to another, when the two pulleys are not more than 10 meters apart. 9. What are the types of ropes? The types of ropes are: *Fiber ropes. *Wire ropes. 10. Quarter turn left drive. The quarter turn left drive is used with shafts arranged at right angles and rotating in one definite direction. 11. Define the velocity ratio of the belt drive. The velocity ratio of the belt drive is defined as the ratio between the velocities of the driver and the follower or the driven. 12. Advantages of V-belt. *Power transmitted is more due to wedging action in the grooved pulleys. *V-belt is more compact, quite and shock absorbing. *The V-belt drive is positive because of negligible slip between the belt and the groove. *High velocity ratio may be obtained. 13. Disadvantages of V-belt. *It cannot be used with large center distances. *It is not as durable as flat belt. *It is a costlier system. 14. Circular belts or ropes. *Ropes are circular in cross section. *It is used to transmit more power. *Distance between two pulleys is more than 8metres. 15. Belt materials. BELT TYPES

BELT MATERIALS Flat belts Leather, canvas, cotton & rubber.

V-belts Rubberized fabric & rubber. Ropes Cotton, hemp & manila. 16. Name the types of friction.

*Static friction. *Dynamic friction. 17. Define the angle of repose.

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18. What is meant by frictional force? Force of friction is always acting in the direction opposite to the direction of motion. 19. Why self locking screws have lesser efficiency? Self locking needs some friction on the thread surface of the screw and hence it needs higher effort to lift a body and hence automatically the efficiency decreases. 20. What is static friction? It is the friction experienced by a body, when at rest. 21. What is dynam It is the friction experienced by the body, when in motion. The dynamic friction is also called as kinematic friction. 22. What is co-efficient of friction? It is defined as the ratio of the limiting friction(F) to the normal reaction(R 23. Define screw jack. The screw jack is the device used to lift the heavy loads by applying a comparatively small effort at its handle. The working principle of screw jack is similar to that of an inclined plane. 24. Square thread vs V-thread. *V-thread is stronger and often moves frictional to the motion than square threads. *A given load may be lifted by applying lesser force by square thread as compared to V-threads. *V-threads are capable of taking more loads as compared to square threadsic friction? 25. What is the effort required to lift a 50tonne lorry using screw jack? (

26. Open belt drive. The open belt drive is used with shaft arranged parallel and rotating in same direction. The tension in the lower side will be more than in the upper side belt because of more tension in the lower side belt, the lower side belt is known as tight side where as the upper side is known as the slack side 27. Open belt drive with one idler pulley. Idler pulleys are provide to obtain high velocity ratio and when the required belt tension cannot be obtained by other means. Idler pulley is also known as jockey pulley.