BASIC MECHANICAL ENGINEERING FIRST YEAR ENGINEERING (University of Pune) Prepared By- Prof. S.S. Khasbage BASIC MECHANICAL ENGINEERING Prof. S.S.Khasbage surajkhasbage@ymail.com

Introduction to Mechanical Engineering UNIT I Mechanical Elements: Function, Sketch, Description, Uses and Classification of – Shaft, Axle, Parallel Key, Rigid Flange Coupling, Ball Bearing, Single Plate Clutch & Disc Brake Power Transmission Devices: Construction, Working, Comparison , Application and Classification of – Belt Drives (Flat & V-Belt), Chain Drives and Spur Gear Drive arranged with Simple Gear Train Introduction to Mechanical Engineering Book Referred – Design of Machine Elements by V. B. Bhandari Prof. S.S.Khasbage surajkhasbage@ymail.com

Text & Reference Books Basic Mechanical Engineering by G. Shanmugam & S. Ravindran, Tata McGraw-Hill Publisher Foundation of Mechanical Engineering by R. K. Purohit, Scientific Publisher Elements of Mechanical Engineering by C. S. Chetankumar & B. P. Mahesh, S. Chand Publications Engineering Thermodynamics by P. K. Nag, Tata McGraw-Hill Publisher (Unit No. V & VI) Elements of Workshop Technology by Chaudhari & Hajra, Media Promoters & Publishers (Unit No. III & IV) Prof. S.S.Khasbage surajkhasbage@ymail.com

Marking Scheme 50+50+25 Online Test: 50 Marks Online Test 1: 30 Minutes Examination, 25 Marks Online Test 2: 30 Minutes Examination, 25 Marks Theory Paper: 2 Hours Examination, 50 Marks Term-work: 25 marks Prof. S.S.Khasbage surajkhasbage@ymail.com

Objective and Outcomes of Unit I Understand and identify basic machine elements and power transmission devices with their functions. Outcomes of Unit I: Distinguish between different Basic Machine Elements with their application Enable to decide a correct system or device required in a specific application Knowledge of advantages and limitations of selected system or device over other options Prof. S.S.Khasbage surajkhasbage@ymail.com

Mechanical Machine Elements Holding Type Nuts and Bolts Keys Couplings Rivets Cotters Supporting Type Body Frame Axle Bearings Frames Power Transmitting Elements Gears Shafts Pulleys and Belts Sprockets and Chains Clutches Prof. S.S.Khasbage surajkhasbage@ymail.com

Automobile Transmission System Prof. S.S.Khasbage surajkhasbage@ymail.com www.Wikipedia.org 

Shaft The shaft is a rotating bar generally of circular cross section, which is used to transmit torque or rotational motion. Common Terms Associated with Shafts: Transmission Shaft Line Shaft Counter Shaft Jackshaft Spindle Crankshaft Prof. S.S.Khasbage surajkhasbage@ymail.com

Transmission Shaft The shaft which is directly connected power is called transmission shaft Prof. S.S.Khasbage surajkhasbage@ymail.com

Line Shaft Line shaft is a very long transmission shaft which is directly driven by the prime mover (or power source) and which is used distribute power from main the main power source to different power consuming devices. Prof. S.S.Khasbage surajkhasbage@ymail.com

Counter Shaft Counter shaft is a secondary shaft which is not directly connected to power source but driven by it through belt, chain or gear drive. Prof. S.S.Khasbage surajkhasbage@ymail.com

Crankshaft The shaft which used in multi cylinder IC engine to which cranks are embedded is called crankshaft. Prof. S.S.Khasbage surajkhasbage@ymail.com www.Wikipedia.org 

Spindle Spindle is peculiar terminology associated with shafts of machine tools which provide rotary motion either to a cutting tool or to a work piece. . Prof. S.S.Khasbage surajkhasbage@ymail.com

Jackshaft A short intermediate shaft on which two pulleys or gears or sprockets are mounted to change the speed within the transmission system. Prof. S.S.Khasbage surajkhasbage@ymail.com www.joewiseguy.com www.diygokarts.com

AXLE The axle is a non rotating bar which doesn’t transmit any torque but only used to supports rotating machine elements like wheels, pulleys etc. Wikipedia.com  BFF Design Ltd Prof. S.S.Khasbage surajkhasbage@ymail.com

Difference between Axle and Shaft Axle is a non rotating member Shaft is rotating member Primary function is to provide support to elements like wheel, pulley etc. Primary function is to transmit torque. Axle is primarily subjected to bending (axial force) Shaft is subjected to bending, torque, as well as vibrations Design of axle is relatively simple compared to shaft Design of shaft is complex as compared axle because shaft is simultaneously subjected to torque, bending, and vibrations Depending upon loading condition, cross sectional area of axle can be different e. g. Rectangular, Circular, I-section, T-section etc. Cross sectional area of shaft is generally circular because it causes minimum vibrations and stress as compared to other shapes of same cross sectional area. e.g. Axles of automobiles, railway buggies. e.g. Shaft of electric motor, shaft of IC engine Prof. S.S.Khasbage surajkhasbage@ymail.com

Mechanical Keys The key is machine element which is used on shaft to position/secure the rotating elements like gears, pulleys or sprockets and prevent free relative rotation between shaft and the element which is mounted on the shaft Key transmits the torque from the shaft to the rotating element or vice-versa. Prevent the relative motion between shaft & hub Prof. S.S.Khasbage surajkhasbage@ymail.com

Classification of Keys: Saddle Sunk Keys Splines Tangent keys Kennedy Keys Round keys and taper Pins Prof. S.S.Khasbage surajkhasbage@ymail.com

Sunk Keys Rectangular Square Parallel Gibb Headed woodruff Feather Key W=D/4 H=2/3 W W=H=D/4 Prof. S.S.Khasbage surajkhasbage@ymail.com

Tangent Keys The tangent key transmits the torque only in one direction by means of compressive force alone Tangent key is subjected to compressive stress Two tangent keys separated by 900 angle force hub and shaft to concentric position Example: Kennedy Key Prof. S.S.Khasbage surajkhasbage@ymail.com

Saddle Key The saddle key is a key which fits in key way of hub only and transmits torque between hub and shaft by means of friction Saddle key doesn’t sink inside the shaft hence it is NOT a sunk key Saddle keys have low torque transmitting capacity As key way on shaft is avoided saddle keys don’t weaken the shaft Prof. S.S.Khasbage surajkhasbage@ymail.com

Sunk Key The sunk key is a key in which some portion of its thickness fits in keyway on shaft and remaining portion of the thickness sits in key way of hub. The torque is transmitted by means of shear force within the key. As key way on shaft is required sunk keys weaken the shaft Prof. S.S.Khasbage surajkhasbage@ymail.com

Why Tapered Keys ? The thickness of the tapered key changes along the length As compared to parallel keys, the tapered keys are more tight because of wedge action Tapered keys are easy to remove as compared parallel keys Prof. S.S.Khasbage surajkhasbage@ymail.com

Parallel Key The parallel keys have uniform thickness along their length Prof. S.S.Khasbage surajkhasbage@ymail.com Technifast.com

Gib Headed Keys The key which is provided with head for easy removal is called Gib headed key Prof. S.S.Khasbage surajkhasbage@ymail.com

Woodruff Key The Woodruff key is sunk key, almost in the form of semicircular disc of uniform thickness The curved portion of key sits inside slot made on shaft whereas flat portion sits inside slot made on hub The extra depth of Woodruff key prevents its tendency of slip over during heavy load condition. The Woodruff key is extensively used in tapered shafts because it can align easily with the hub slot by slight rotations Woodruff keys weaken the shaft because of their extra depth th Prof. S.S.Khasbage surajkhasbage@ymail.com

Feather Key The feather key is a key which allows relative axial motion between hub and shaft but prevents relative rotational motion between them The key is permanently fixed to the shaft generally. Clearance is provided between hub and key so that hub slides freely over the key Sometimes double Gib headed key is provided so that hub will not come out completely Prof. S.S.Khasbage surajkhasbage@ymail.com

Couplings Coupling is the mechanical element used to connect two shafts permanently of a transmission system and transmit the torque from one shaft to another. Functions of Coupling : Connects two shafts Introduces mechanical flexibility and tolerates small misalignment (Valid for Flexible Couplings) Adds stiffness to the system hence reduces bending Reduces the transmission of vibrations and shocks (Valid for some of Flexible Couplings) Prof. S.S.Khasbage surajkhasbage@ymail.com

Universal/ Hooke’s Joint Couplings Rigid Sleeve or Muff Split Muff Flange Un-Protected type Protected type Flexible Bush pin type Universal/ Hooke’s Joint Oldham Beam coupling Prof. S.S.Khasbage surajkhasbage@ymail.com

Rigid Couplings These couplings are not capable of tolerating any misalignment between two shafts. These couplings are not capable of absorbing shocks and vibrations. These are simple and inexpensive. Prof. S.S.Khasbage surajkhasbage@ymail.com

Muff Coupling Prof. S.S.Khasbage surajkhasbage@ymail.com youtube.com

Split Muff Coupling youtube.com Prof. S.S.Khasbage surajkhasbage@ymail.com youtube.com

Unprotected Rigid Flange Coupling Prof. S.S.Khasbage surajkhasbage@ymail.com youtube.com

Un – protected Flange Coupling grabcad.com Prof. S.S.Khasbage surajkhasbage@ymail.com

Protected Rigid Flange Coupling Prof. S.S.Khasbage surajkhasbage@ymail.com youtube.com

engineeringdesigns.blogspot.in Prof. S.S.Khasbage surajkhasbage@ymail.com

Flexible Couplings Flexible couplings allow axial and/or angular misalignment between two shafts Universal Coupling Beam Coupling wikipedia.org www.mech.uq.edu Oldham Coupling cornell.edu Prof. S.S.Khasbage surajkhasbage@ymail.com

Bush Pin Coupling Brass or Brass Coated with Rubber Bush is used . Application- Very small axial misalignments e.g. Coupling between electric motor and pump Prof. S.S.Khasbage surajkhasbage@ymail.com

Oldham’s Coupling Allows small axial misalignment between the two shafts Prof. S.S.Khasbage surajkhasbage@ymail.com

Beam/Helical Coupling Allows angular misalignment between the two shafts Prof. S.S.Khasbage surajkhasbage@ymail.com youtube.com

Hooke’s Joint /Universal Coupling Prof. S.S.Khasbage surajkhasbage@ymail.com

Bearings Bearing is a device that allows relative motion between two parts, such as shaft and housing with low friction as well as it restricts the motion of shaft in one desired direction only. Functions: It ensures free rotation of the shaft or the axle with minimum friction. It supports shaft or axle and holds it in the correct position. It takes the forces acting on the shaft or the axle in both working as well rest condition and transfers them to frame on which it is mounted. Prof. S.S.Khasbage surajkhasbage@ymail.com

Prof. S.S.Khasbage surajkhasbage@ymail.com

Bearings Rolling Contact Ball Bearing Roller Bearing Sliding Contact Hydrostatic Bearing Hydrodynamic Bearing 1.Cylindrical Roller Bearing. 2.Needle Roller Bearing. 3. Tapered Roller Bearing 4.Tapered Roller Thrust Bearing eg. Journal Bearing (Bush Bearing) 1.Single row deep groove Ball Bearing. 2.Doublerow deep groove Ball Bearing. 3.Angular Contact Ball Bearing 4.Thrust Ball Bearing Prof. S.S.Khasbage surajkhasbage@ymail.com

Ball Bearings The purpose to support a load while permitting relative motion between two elements of a machine. The components of a typical rolling contact bearing are the inner race, the outer race, cage and the rolling elements. SHAFT Prof. S.S.Khasbage surajkhasbage@ymail.com yourdictionary.com

Angular Contact Ball Bearing Double Row Deep Groove Ball Bearing Single Row Deep Groove Ball Bearing Prof. S.S.Khasbage surajkhasbage@ymail.com Thrust Ball Bearing

Roller Bearings Cylindrical Roller Bearing Tapered Roller Bearing Needle Roller Bearing Prof. S.S.Khasbage surajkhasbage@ymail.com Tapered Roller Thrust Bearing

Journal Bearings Hydrostatic Bearing: Oil is Pressurized Hydrodynamic Bearing: Oil is NOT Pressurized Prof. S.S.Khasbage surajkhasbage@ymail.com

Clutch It connects or disconnects the source of power from the remaining parts of the power transmission system at the will of the operator. Clutches Positive Clutch Claw or Jaw type Friction Clutch Plate or Disc Single Plate Multiple Plate Cone Centrifugal 1.The force requires to disengage should be minimum, 2.operation of engagement & Dis engagement can be done at any speed 3.Heat generation during engagement should be minimum 4.there should not be more stress generation in clutch material Prof. S.S.Khasbage surajkhasbage@ymail.com

Positive Type Clutch hellotrade.com Adv-1. no heat 2. no slip 3. less maintenance Dis-cannot engage at high speed , engagement at any speed is with shock and noice. hellotrade.com Prof. S.S.Khasbage surajkhasbage@ymail.com

Single Plate Clutch codecogs.com Prof. S.S.Khasbage surajkhasbage@ymail.com codecogs.com

Centrifugal Clutch Multi- plate Clutch Cone Clutch Prof. S.S.Khasbage surajkhasbage@ymail.com

Block Brake/Drum B rake Brakes Brake is a mechanical device used to stop or slow down the moving body. Brakes Mechanical Block Brake/Drum B rake External Internal Expanding Band Brake Disc Brake Electrical Eddy Current Brakes Prof. S.S.Khasbage surajkhasbage@ymail.com

Disc Brake Assembly Absorbs more heat than a drum brake assembly When the brake pedal is pushed, brake fluid from the master cylinder compresses the brake pads against the rotors attached to the vehicle's front wheels. The friction between the stationary pads and the revolving rotors causes the rotors and wheel to slow down/ stop. howstuffworks.com Prof. S.S.Khasbage surajkhasbage@ymail.com

Prof. S.S.Khasbage surajkhasbage@ymail.com

Internal Expanding Type www.roymech.co.in Single Block Double block External type Internal Expanding Type www.answers.com Prof. S.S.Khasbage surajkhasbage@ymail.com

Difference Between Clutch and Brake Function: Absorbs Power During Normal Operation of Vehicle: Disengaged Position of mating Surfaces: One surface is always stationary and other may be fixed or rotating Final Condition : Both members are at rest and have no relative motion. Clutch Function: Transmits Power During Normal Operation of Vehicle: Engaged Position of mating Surfaces: One surface is always rotating and other may be fixed or rotating Final Condition : Both members rotate at the same speed and have no relative motion. Prof. S.S.Khasbage surajkhasbage@ymail.com

Drives Drive is a link between Prime mover and Driven machinery. Prime movers, power producing devices. Power Transmitting link Driven Machinery, Power absorbing devices Flour Mill Oil Mill. Vehicle propulsion. Machine Tools. Compressors, pumps. Material handling Equipments. House hold gadgets. I.C. Engines Steam Engines. Gas Turbines. Steam Turbines. Water Turbines. Wind Mills. Electric Motors. Chain drive. Belt Drive. Rope Drive. Gear Drive. Prof. S.S.Khasbage surajkhasbage@ymail.com

Flat Belt Drive Large distance between shafts cheaper compared to ‘V’ belts. The slip is more. Cross belts are used to reverse direction of rotation. Flat belts provide only small speed ratios. Cross section Prof. S.S.Khasbage surajkhasbage@ymail.com wikipedia.com

Quarter Turn Belt Drive chestofbooks.com Open Belt Drive Quarter Turn Belt Drive mikrobot.blogspot.in Prof. S.S.Khasbage surajkhasbage@ymail.com

Cross Belt Drive Cross Belt Drive chestofbooks.com Cross Belt Drive Increased angle of contact results in increased grip However, rubbing of belt causes reduced belt life Prof. S.S.Khasbage surajkhasbage@ymail.com

V Belt Drive Prof. S.S.Khasbage surajkhasbage@ymail.com wikipedia.com

Chain Drive Prof. S.S.Khasbage surajkhasbage@ymail.com wikipedia.com

Chain Elements Inner Link Bushing Pin Outer Link wikipedia.com Roller Prof. S.S.Khasbage surajkhasbage@ymail.com patentpending.blogs.com

Chain Elements Inner Link: It has bigger hole diameter Outer Link: It has smaller hole diameter Bush : It is a hollow cylinder and it press fits inside two inner links Pin: It passes through the bush, two outer links are press fitted on it Roller: It is a hollow cylinder which can rotate freely over bush Bush and pin joint is responsible for flexibility of the chain. Roller is added to reduce the wear of the sprocket Prof. S.S.Khasbage surajkhasbage@ymail.com

Chain Drive Advantages Disadvantages No slip High transmission efficiency (upto 98 percent) High power transmission capacity High speed ratio (8 to 10 in one step) It gives less load on the shafts because pretension is not required It can be operated under adverse temperature and atmospheric conditions. Disadvantages High cost At high speed noise increases Requires lubrication and frequent maintenance Prof. S.S.Khasbage surajkhasbage@ymail.com

Belt Drive Advantages (Over Chain Drive) High Operating Speed Allows angular misalignment between two shaft Need not to have exact centre distance between two shafts Low Cost, Easy installation Disadvantages (Over Chain Drive) Slip causes fluctuation in speed Low power transmission Capacity Low speed Ratio (upto 3) Less Compact Pretension of belts is required which increases load on the shaft Prof. S.S.Khasbage surajkhasbage@ymail.com

V Belt Drive Advantages (over Flate Belt Drive) Less slip Less noise because V belts are endless The high velocity ratio (maximum 10) may be obtained. High power transmitting capacity More Compact Disadvantages (over Flate Belt Drive) The centrifugal force prevents the use of V-belts at high speeds Cost is high Prof. S.S.Khasbage surajkhasbage@ymail.com

Classification of the Gears based upon position of shaft axes Parallel Shaft Spur Helical Rack & Pinion Intersecting Shaft Bevel Non – parallel and non Intersecting Spiral Worm Prof. S.S.Khasbage surajkhasbage@ymail.com

Gears Gear is a toothed wheel which is used in a power transmission system to transmit torque/power from one shaft to other Spur Gears Helical Gears Bevel Gears Worm Gear Rack and Pinion Prof. S.S.Khasbage surajkhasbage@ymail.com

Gear is a tooth profile is either involute or cycloid. Gear Terminology Gear is a tooth profile is either involute or cycloid. Prof. S.S.Khasbage surajkhasbage@ymail.com

Spur Gear Prof. S.S.Khasbage surajkhasbage@ymail.com

Helical Gear Spur Gear wikipedia.com Rack and Pinion Prof. S.S.Khasbage surajkhasbage@ymail.com Rack and Pinion

Bevel Gear Prof. S.S.Khasbage surajkhasbage@ymail.com wikipedia.com

Worm Gear Prof. S.S.Khasbage surajkhasbage@ymail.com wikipedia.com

Spur Gear Train with Idler gear a) Simple Gear Train Spur Gear Train with Idler gear Output 3 Idler Gear Prof. S.S.Khasbage surajkhasbage@ymail.com

b)Coumpound Gear Train Prof. S.S.Khasbage surajkhasbage@ymail.com

Gear Train c) Reverted Gear Train Prof. S.S.Khasbage surajkhasbage@ymail.com

d) Epicyclic Gear Train Prof. S.S.Khasbage surajkhasbage@ymail.com

Features of Gear Drives Positive drive No slip results to constant velocity ratio Compared to chain drives it is smoother in operation. It is suitable when the centre distances are small. for given amount of power transmission, the drive is most compact. Precise ratios are possible. Very long life. Expensive Compared to belt drives gear drives are Noisy. Comparatively Expensive and Maintenance cost is also higher. They require Precise Alignment of the shafts. Prof. S.S.Khasbage surajkhasbage@ymail.com

What is the brake? How does it differ from clutch? [ 2+ 2+4] University Question: YEAR 2010 What is the brake? How does it differ from clutch? [ 2+ 2+4] Explain with neat sketch ( 4 each) Ball Bearing Transmission Shaft YEAR 2011 Q.7) (B) Distinguish between Kinematic Pair and Kinematic Chain with an example for each. [06] (C) What are the advantages and disadvantages of Belt Drives ? [04] OR Q.8) (A) What is a Clutch ? Explain with a neat diagram the working of a Single Plate Clutch. [07] (B) What is a Brake ? How brakes are classified [09] Prof. S.S.Khasbage surajkhasbage@ymail.com

(C) Compare Flat Belt and V-Belt. [06] OR Q.12) YEAR 2009 Q.11) (A) Draw sketch of Single Plate Clutch and explain its working. [06] (C) Compare Flat Belt and V-Belt. [06] OR Q.12) (C) State advantages and disadvantages of Chain Drive over Belt Drive. [06] YEAR 2012 7. A) Difference between ‘Line shaft’ and ‘Counter shaft’ with diagram. (2+2+4=8) B) How the couplings are classified (2+3+3=8) 8. B) Define ‘Gear Ratio’ and explain with neat (2+3+3=8) Prof. S.S.Khasbage surajkhasbage@ymail.com

(B) Explain any one type of Clutch with sketch. [06] OR YEAR 2010 Q.11) (B) Explain any one type of Clutch with sketch. [06] OR Q.12) (A) Compare Belt and Gear Drive. [06] YEAR 2011 8. A) How gears are classified ? What are the functions of gears ? State applications of different types of gears. (3+2+3) Prof. S.S.Khasbage surajkhasbage@ymail.com

Differentiate between Belt drives and Gear drives. Practice Question State the advantages and disadvantages of V belt over Flat bet drive. Differentiate between Belt drives and Gear drives. Compare merits and demerits of Individual drive with group drive. Suggest suitable element for following. Shaft at right angles, Shafts with slight misalignment, Two parallel shafts 3-4 m apart, Two parallel shafts 10 cm apart. Differentiate between flat belt and V belt. Show their cross-sections. Suggest a suitable element for the following, Non parallel non intersecting shafts, Intersecting shafts, Parallel shafts with slight misalignment, Shafts 2-4 m apart. What is a chain drive? How chains are classified? Draw sketches of Helical gears, Bevel gears, Worm and Worm wheel. Differentiate between Belt drive and Chain drive. Prof. S.S.Khasbage surajkhasbage@ymail.com

Appendix Prof. S.S.Khasbage surajkhasbage@ymail.com

Rivets Prof. S.S.Khasbage surajkhasbage@ymail.com

Cotter Joint Prof. S.S.Khasbage surajkhasbage@ymail.com