South Valley University Theory of MachineFaculty of Engineering Code: ENM222 Dept. of Mechanical Engineering 2013/2014 1 Final Report Question One: 1. What is the main purpose of gears? 2. Explain the terms: Module, Pitch circle, Circular pitch, Clearance, Face of a tooth, Flank of a tooth, Backlash, Dedendum and Addendum. 3. What is the main advantage and disadvantage of: spur, helical, double helical, bevel, worm, Rack and pin Gears. 4. What are the main factors considered in gear selection? 5. What do you understand by ‘gear train’? Discuss the various types of gear trains. 6. Explain briefly the differences between simple, compound, and epicyclic gear trains. 7. What are the special advantages of epicyclic gear trains? 8. Explain the procedure adopted for designing the spur wheels. 9. How the velocity ratio of epicyclic gear train is obtained by tabular method? 10. Explain with a neat sketch the ‘sun and planet wheel’. 11. What are the various types of the torques in an epicyclic gear train? 12. Explain the difference between helical gears and spur gears? 13. What are the different types of bevel gears? 14. State the purpose of: bevel gear, helical gears, spur gears, rack and pinion gears and worm gears. 15. Identify the advantages and disadvantages of: bevel gear, helical gears, spur gears Question Two : 1. Explain with a neat sketch the main types of gear trains? 2. State the different methods of Gear Manufacture 3. Figure below, illustrates an automotive sliding-mesh transmission gearbox. The numbers of teeth on the various gear wheels are as follows: South Valley University Theory of Machine Faculty of Engineering Code: ENM222 Dept. of Mechanical Engineering 2013/2014 2 Gear wheel 1 is keyed to the input shaft and cannot slide along it. Gear wheels 2, 3, and 4 form a compound cluster that is keyed to the output shaft but can be slid along it. Gear wheel 10 is a reverse idler. Determine the gear ratios for each speed selection, starting from the lowest forward selection to the highest and then to the reverse selection. Tabulate your results. 4. A compound train consists of six gears. The number of teeth on the gears are as follows : A B C D E F 60 40 50 25 30 24 The gears B and C are on one shaft while the gears D and E are on another shaft. The gear A drives gear B, gear C drives gear D and gear E drives gear F. If the gear A transmits 1.5 kW at 100 r.p.m. and the gear train has an efficiency of 80 per cent, find the torque on gear F. Question Three: 1. In a compound epicyclic gear train as shown in the figure, has gears A and an annular gears D & E free to rotate on the axis P. B and C is a compound gear rotate about axis Q. Gear A rotates at 90 rpm CCW and gear D rotates at 450 rpm CW. Find the speed and direction of rotation of arm F and gear E. Gears A,B and C are having 18, 45 and 21 teeth respectively. All gears having same module and pitch. South Valley University Theory of Machine Faculty of Engineering Code: ENM222 Dept. of Mechanical Engineering 2013/2014 3 2. An internal wheel B with 80 teeth is keyed to a shaft F. A fixed internal wheel C with 82 teeth is concentric with B. A Compound gears DE meshed with the two internal wheels. D has 28 teeth and meshes with internal gear C while E meshes with B. The compound wheels revolve freely on pin which projects from a arm keyed to a shaft A co- axial with F. if the wheels have the same pitch and the shaft A makes 800 rpm, what is the speed of the shaft F? Sketch the arrangement. 3. The fig shows an Epicyclic gear train. Wheel E is fixed and wheels C and D are integrally cast and mounted on the same pin. If arm A makes one revolution per sec (Counter clockwise) determine the speed and direction of rotation of the wheels B and F. Question Four: 1. What is the function of a governor ? How does it differ from that of a flywheel ? 2. State the different types of governors. What is the difference between centrifugal and inertia type governors ? Why is the former preferred to the latter ? 3. Explain the term height of the governor. Derive an expression for the height in the case of a Watt governor. What are the limitations of a Watt governor ? 4. What are the effects of friction and of adding a central weight to the sleeve of a Watt governor ? 5. Discuss the controlling force and stability of a governor and show that the stability of a governor depends on the slope of the curve connecting the controlling force (FC) and radius of rotation (r) and the value (FC /r). South Valley University Theory of Machine Faculty of Engineering Code: ENM222 Dept. of Mechanical Engineering 2013/2014 4 6. The length of the upper arm of a Watt governor is 400 mm and its inclination to the vertical is 30°. Find the percentage increase in speed, if the balls rise by 20 mm. 7. All the arms of a Porter governor are 178 mm long and are hinged at a distance of 38 mm from the axis of rotation. The mass of each ball is 1.15 kg and mass of the sleeve is 20 kg. The governor sleeve begins to rise at 280 r.p.m. when the links are at an angle of 30° to the vertical. Assuming the friction force to be constant, determine the minimum and maximum speed of rotation when the inclination of the arms to the vertical is 45°. 8. A spring controlled governor of the Hartnell type has the following data : Mass of the ball = 1.8 kg ; Mass of the sleeve = 6 kg ; Ball and sleeve arms of the bell crank lever = 150 mm and 120 mm respectively. The equilibrium speed and radius of rotation for the lowest position of the sleeve are 400 r.p.m. and 150 mm respectively. The sleeve lift is 10 mm and the change in speed for full sleeve lift is 5%. During an overhaul, the spring was compressed 2 mm more than the correct compression for the initial setting. Determine the stiffness of the spring and the new equilibrium speed for the lowest position of the sleeve. 9. A Porter governor has all four arms 200 mm long. The upper arms are pivoted on the axis of rotation and the lower arms are attached to a sleeve at a distance of 25 mm from the axis. Each ball has a mass of 2 kg and the mass of the load on the sleeve is 20 kg. If the radius of rotation of the balls at a speed of 250 r.p.m. is 100 mm, find the speed of the governor after the sleeve has lifted 50 mm. Also, determine the effort and power of the governor. 10. A governor of the Proell type has each arm 250 mm long. The pivots of the upper and lower arms are 25 mm from the axis. The central load acting on the sleeve has a mass of 25 kg and the each rotating ball has a mass of 3.2 kg. When the governor sleeve is in mid-position, the extension link of the lower arm is vertical and the radius of the path of rotation of the masses is 175 mm. The vertical height of the governor is 200 mm. If the governor speed is 160 r.p.m. when in mid-position, find : 1. length of the extension link; and 2. tension in the upper arm. Question Five: 1. What do you mean by unbalance and why it is so important? 2. How is unbalanced force due to single rotating mass balanced. 3. How is unbalanced force due to several rotating masses in the same plane determined? 4. Discuss causes of unbalance? 5. Explain the method of balancing of different masses revolving in the same plane. 6. How the different masses rotating in different planes are balanced ? 7. Why is balancing of rotating parts necessary for high speed engines ? 8. Explain clearly the terms ‘static balancing’ and ‘dynamic balancing’. State the necessary conditions to achieve them. 9. Discuss how a single revolving mass is balanced by two masses revolving in different planes. 10. Why all the rotating systems are not balanced? 11. What do you understand by balancing of revolving masses? South Valley University Theory of Machine Faculty of Engineering Code: ENM222 Dept. of Mechanical Engineering 2013/2014 5 12. If not balanced what effects are induced on shaft bearing system due to unbalanced rotating masses. 13. Five masses A, B, C, D and E revolve in the same plane at equal radii. A, B and C are respectively 10, 5 and 8 kg in mass. The angular direction from A are 60 o , 135 o , 210 o and 270 o . Find the masses D and E for complete balance. 14. A shaft carries three pulleys A, B and C at distance apart of 600 mm and 1200 mm. The pulleys are out of balance to the extent of 25, 20 and 30 N at a radius of 25 mm. The angular position of out of balance masses in pulleys B and C with respect to that in pulley A are 90 o and 210 o respectively. It is required that the pulleys be completely balanced by providing balancing masses revolving about axis of the shaft at radius of 125 mm. The two masses are to be placed in two transverse planes midway between the pulleys. 15. The four masses A, B, C and D are 100 kg, 150 kg, 120 kg and 130 kg attached to a shaft and revolve in the same plane. The corresponding radii of rotations are 22.5 cm, 17.5 cm, 25 cm and 30 cm and the angles measured from A are 45 o , 120 o and 255 o . Find the position and magnitude of the balancing mass, if the radius of rotation is 60 cm. With my best wishes Dr. Nouby M. Ghazaly