MECH 1200 Final Review

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1 Class: Date: MECH 1200 Final Review True/False Indicate whether the statement is true or false. 1. The thickness of the generated film depends on the operating conditions such as: velocity, loads, lubicant viscosity, and the pressure/viscosity relationship. 2. As the temperature rises the oil will become less viscous, and will become more viscous as the temperature falls. 3. Additives in lubricating oil reduce the rate at whcih undesirable changes take place in the product during its service life. 4. Lubricants do not help with isolating contamination. 5. Soap is considered a lubricant. 6. Lithium grease is one of the most widespread greases used in industry. 7. Calcium soap greases are capable of absorbing a large percent of their volume with water. 8. A 10W oil is thicker than a 30W oil. Multiple Choice Identify the choice that best completes the statement or answers the question. 9. The time in seconds, required to fill the flask to a prescibed amount. a. Tribology c. Pour Point b. Sabolt Universal Seconds d. Elasto-hydrodynamic Lub film 10. The study of how lubrication affects friction and moving parts. a. Tribology c. Pour Point b. Sabolt Universal Seconds d. Elasto-hydrodynamic Lub film 11. A condition in which surfaces of heavily loaded rolling element bearings are either completely or separated in part, by a very thin lubricant film. Pressure rises at the point of contact causing micro deflection in the metal. The deflected surfaces are momentarily pressed together and flattened. The elastic deformation of the contacting surfaces trap the lubricant, subjecting it to extremely high-pressures which increases its viscosity and it load carrying capacity. When the rolling elements roll on, the surfaces return to their original shape and viscosity returns to its original condition. a. Tribology c. Pour Point b. Sabolt Universal Seconds d. Elasto-hydrodynamic Lub film 1

2 12. The lowest temperature at which oil will flow in a controlled laboratory test. a. Tribology c. Pour Point b. Sabolt Universal Seconds d. Elasto-hydrodynamic Lub film 13. A 5W-30 oil acts like a. a SAE 30 in the cold and SAE 5 when its hot. b. a SAE 5 in the cold and SAE 30 when its hot. c. the same regardless of temperature. d. None of these 14. Calculate the driven shaft speed of the belt drive system given the following information: Driver Sheave: Torque = 200 ft lbs Speed = 3500 RPM Pitch Dia. = 2 in Driven Sheave: Pitch Dia. = 8 in a RPM c. 875 RPM b RPM d. 600 RPM Completion Complete each statement. 15. What is the belt length and span length for a system that has a center distance of 30, a large sheave diameter of 12 and a small diameter sheave of 8? Belt Length = Span Length = Short Answer 16. What are the benefits of having maintenance employees that are multi-craft or super-craft trained? 17. What is the primary goal of preventative maintenance? 2

3 18. A technician performs a vibration analysis on two aircraft wings, this test is called Wing health monitoring. The natural frequencies of the two wings are shown below. Assume that the natural frequency of a healthy wing is in the range 4-6 Hz. (ignore magnitude damping) Answer the following questions (4 points): a) What is the frequency of the vibration signal obtained from wing A? b) What is the frequency of the vibration signal obtained from wing B? c) Which wing, if any, is not healthy? 19. What is the formula that defines linear mechanical work? 20. Name two prime movers and how they differ. 21. What is the definition of mechanical power? 22. If an individual could lift 550lb one foot in one second, how much horsepower would he be generating? 23. What is Newtons first law of motion as it pertains to inertia? 24. What are three cause of friction between two surfaces? 25. Calculate the torque produced from a 24 lever with 180 pound of force applied to it. 26. Three different mechanical power transmission drives are connected in a system. A V-belt drive connected to a gearbox, which is connected to a roller chain drive transfering power and torque to a conveyor system. The efficiencies of the drives are 97%, 96%, and 98% respectively. What is the overall efficiency of this system? 3

4 27. What is the rim velocity, in feet per minute, of a 20 diameter wheel rotating at 1750 RPM. 28. What is the formula for mechanical efficiency? 29. How much force is required to move 100lb object on a surface with a coefficient of friction of.08? 30. How much horsepower is required to lift a 1000lb object 12 feet in 20 seconds? 31. What is the formula for calculatin overhung load? 32. List three ways that overhung load can be minimized. 33. Name two of the six basic machines. 34. What is Tribology? 35. What affect does heat have on the viscosity of a lubricating oil? 36. Define the term Saybolt Universal Seconds. 37. What determines the thickness of a lubricating film? 38. What is the pour point of an oil? 39. What is an Elasto-hydrodynamic Lub Film? 40. What is the purpose of putting additives in lubricating oil? 41. List some of the advantages of synthetic lubricating oil. 42. Why is grease consistency important? 43. Whay is grease compatibility an important issue? 44. What is one of the chief advantages of an automated lubricant system? 45. Why is safety a concern when handling lubricants? 46. What is the term Pitch as it applies to a thread? 47. What is the term lead as it apples to a thread? 48. If a thread has 40 threads per inch, what is its pitch? 49. If a thread has 20 threads per inch what is its lead? 4

5 50. Thoroughly describe a 1/2-12 2A thread. 51. Thoroughly describe a M10 thread. 52. Name three materials that radial lip seals can be made from. 53. What is a gasket? 54. Describe packing materials and where they are found. 55. What is a mechanical seal? 56. What is a rotary seal? 57. Name four advanteges of a mechanical seal. 58. What is a bearing and what is it s purpose? 59. Name five different types of gears. 60. What is the diametral pitch of a gear with 70 teeth that has a pitch diameter of 40? 61. Describe the advantages of a worm gear drive. 5

6 62. Complete the table below: Gear Number Direction Ratio Speed (RPM) 1 NA

7 63. Below is a typical torque curve for an asynchronous induction motor, (1800 rpm synchronous speed) What is the speed at 200 % run full load current? What is the slip? 64. Refer to the figure: a) What type of motor is this? b) What is the full-load speed of the motor? c) What is the starting torqu in percent with respect to the full load torque? 7

8 65. Name the type of motor based on its given schematic. Problem 66. Define Preventative Maintenance, Work Orders, Logbooks, Predictive Maintenance, Vibration Analysis, Resonance, Cycle, Amplitude, Frequency, Phase, Velocity, Acceleration, Transducers, Analyzers, Oil Analysis, Thermography. 67. Know/Understand the following - accident, lockout and tagout. 68. Define - Energy, Force, Inertia, Friction, Angular Speed, Radius of gyration, Work, Mechanical Advantage, Basic Machines, Torque, Power, Horsepower, Efficiency, Load Classifications, Service Factor, Run-out, Overhung Load, 69. Calculate the design horsepower of a 8HP fan that runs continuously with a service factor of Calculate the design horsepower of a 15HP Dough Mixer that runs continuously with a service factor of Calculate the design horsepower of a 35HP Piston Compressor that runs continuously with a service factor of

9 72. Calculate the torque, speeds, horsepower, and ratio at each shaft. Also, determine the velocity of the pulley in feet-per-minute. 9

10 73. Use the chart to determine what size hole should be drilled to tap a 1/4-20 tapped hole? Hole size = 74. Define Low Head Cap Screws, Flat Head Cap Screws, Button Head Cap Screws, Socket Shoulder Screws, Machine Screws, Set Screws. 75. Be able to identify common types of nuts. 76. Define Dowel Pins, Cotter Pins, Retaining Rings, Keys. 10

11 77. Calculate the sheave ratio, speed and torque of the driven sheave: Pulley Ratio = S Driven = T Driven = 11

12 78. Know your belts: 12

13 79. Define: Chain Driver Sprocket Driven Sprocket Chordal action Single Strand Chain Multiple Strand Chain Double Pitch Chain Offset Chain 13

14 80. Calculate the sprocket ratio shown below. 81. Label the parts of the roller chain. 14

15 82. Know your Chain drives. 83. What are the four types of roller chain drives? 84. Calculate the Mid-Span Movement and Chain Sag Range for the chain drive shown below. Mid-Span Movement = Chain Sag Range = 15

16 85. Know your hub Types: 86. Calculate the driven shaft speed and torque of the gear drive system fiven the following information. Driver Gear: Pitch Dia. 1.8 inches Speed 1800 RPM Torque 125 in-lbs Driven Gear: Pitch Dia. 6.5 in Driven Shaft Speed is RPM. Driven Shaft Torque is in-lbs. 16

17 87. Calculate the diametral pitch of each gear. Then calculate the center distance of the two gears. Use the table to find the allowable backlash range. DP of the Pinion = DP of the Gear = Center Distance = Backlach Range = 88. Calculate the overall gear ratio. ratio = 17

18 89. Calculate the ratio at shaft 3 and the total input Torque based on the output Torque at shaft Calculate the driver shaft speed and the driver shaft torque of the system. driver shaft speed = RPM driver shaft torque = in-lbs 18

19 91. Calculate the driver shaft speed and the driver shaft torque of the compound gear drive system. Driver Shaft Speed = RPM Driver Shaft Torque = in-lbs 92. Know the following: Stator Rotor Field Winding, Armature winding, Commutator segments, brushes, interpole windings 93. Know the classifications of motors 94. Know the different types of motors and be able to say if they are AC, DC or Special Purpose. 95. If you need to replace a motor and you found that the motor has a permanent magnet in its rotor, then this motor is a. 96. If you needed to replace a motor, you found that the motor has a permanet magnet in it stator, then it could be a 97. If a motor has two capacitors attached to the stator unit, then this motor is most likely a. 98. What electric machine is best suited to be used to generate electricity? 19

20 99. What motor is potentially dangerious to operate with no load on it? What is added to a DC motor to reduce sparking? What type of motor has the highest output torque ratio? What type of motor has a stationary magnetic field in the stator and an alternating magnetic field in the rotor? 100. What type of motors have a rotating magnetic field in the stator and a stationary magentic field in the rotor? 101. The rotating part of a DC motor is commonly called a 20

21 MECH 1200 Final Review Answer Section TRUE/FALSE 1. ANS: T 2. ANS: T 3. ANS: T 4. ANS: F 5. ANS: T 6. ANS: T 7. ANS: T 8. ANS: F MULTIPLE CHOICE 9. ANS: B 10. ANS: A 11. ANS: D 12. ANS: C 13. ANS: B 14. ANS: C COMPLETION 15. ANS: Belt Length = Span Length = SHORT ANSWER 16. ANS: Multi-skilled maintenance technicians are valuable because they are flexible, cost effective, and reliable source of feedback. A flexible maintenance staff that is capable of handling most machine failures, are an asset to the organization. 17. ANS: Minimize machine failures and optimize the amount of production time. PM serves the purpose of keeping the equipment operating at its peak efficiency beyond its normal service life under safe conditions. 1

22 18. ANS: 2.5 HZ 5 HZ Wing A 19. ANS: W = F x D 20. ANS: Prime movers convert one form of energy to another. See explanation of each one. 21. ANS: Power = Work / Time 22. ANS: 1 HP 23. ANS: Bodies at rest tend to stay at rest, bodies in motion tend to stay in motion unless acted on by another force. 24. ANS: examples may be: Intermeshing of small surface irregulaties called aspirtes. Adhesion and cohesion due to molecular attraction of the two surfaces. Hard surface onto a softer one. The weight of the object or forces holding the surfaces together. 25. ANS: Torque = Force * Lever arm (radius) = 180 * 24 = 4320 lbs 26. ANS:.97 x.96 x.98 = 91% 27. ANS:.262 x 20 x 1750 = 9170 ft/min 2

23 28. ANS: %efficiency = (100) power output / power input 29. ANS:.08 x 100 = 8 lb 30. ANS: (1000 x 12 ) / 20 = 1.09 HP 31. ANS: Overhung load = ( x HP x Fc x Lf) / (PD x RPM) 32. ANS: Some examples: Properly tension the connecting drive Increase the diameter of the connectin component within reasonable limits Locate the load and component as close as possible to the supporting bearing. Install a larger or another bearing 33. ANS: Wedge, Screw, Wheel and Axel, Lever, Pulley, Incline plane 34. ANS: The study of how lubrication affects friction and moving parts. 35. ANS: The best lubricant is the one with the lowest viscosity that maintains a separating film between metal parts at the various operating temperatures of the equipment. Operating temperatures have an affect of the viscosity of a lubricant. As the temperature rises the oil will become less viscous, and will become more viscous as the temperature falls. 36. ANS: It is how lubricants are measured in the United States. The time, inseconds, required to fill the flask to a prescribed amount. 3

24 37. ANS: The thickness of the generated fil depends on the operating conditions such as: velocity, loads, lubicant viscosity, and the pressure/viscosity relationship. 38. ANS: Pour point is the lowest temperature at which oil will flow in a controlled laboratory test. 39. ANS: A condition in which surfaces of heavily loaded rolling element bearings are either completely or separated in part, by a very thin lubricant film. Pressure rises at the point of contact causing micro deflection in the metal. The deflected surfaces are momentarily pressed together and flattened. The elastic deformation of the contacting surfaces trap the lubricant, subjecting it to extremely high-pressures which increases its viscosity and it load carrying capacity. When the rolling elements roll on, the surfaces return to their original shape and viscosity returns to its original condition. 40. ANS: Improve the performance properties. Impart entirely new performance characteristics to the finished oil compound. Reduce the rate at whcih undesirable changes take place in the product during its service life. 41. ANS: Synthetic based fluids are tailored to have a uniform molecular structure and size, free of unwanted substances and impurities. They can cope better with extreme temperatures. They are very efficient at reducing friction. Viscosity changes less with temperature variances. Oxidation rate is more stable. 42. ANS: So that it does not deform under an applied force. 43. ANS: Mixing lubricants that are incompatible can result in inadequate lubrication at the very least, catastrophic at the worst. Intermixing can cause problems with lubricant properties and function. 44. ANS: The lubricant is isolated from contamination and metered out under a controlled pressure to where it is needed. 4

25 45. ANS: Because lubricants are made with many different materials and chemicals they are considered hazardous materials. Special precautions must be taken when apply and handling lubricants to prevent injury and illness. 46. ANS: The distance between thread crests. 47. ANS: How far a thread advances in one revolution. 48. ANS:.025 inches 49. ANS: same as its pitch so ANS: Major diameter is 1/2 inch, 13 threads per inch. 51. ANS: Metric thread with a major diameter of 10 mm 52. ANS: The shell is often made from steel and a variety of compounds such as fluoraelastomers, silicones, Teflon, felt, leather, and many other materials are available for the lop material. 53. ANS: A gasket is a pliabe material that is shaped and place between two mating machined surfaces to form a seal. 54. ANS: Packing is usually found in pump stuffing boxes. The packing is usually made of multiple shaped ings, which seal against the shafte and box housing walls. Packing is constructed in many different types of weaves. Braid over braid, interlocked and plaited. The most common materials for packing is carbon and graphite. 5

26 55. ANS: A sealing mechanism made up of several assembled parts. It seals at 3 locations. 1)statics seal between the housing and stationary part of the seal 2) static seal between the shaft and the rotating mechanical seat. 3) dynamic seal between the roating seal face and the stationary seal face. 56. ANS: Has a stator stationary component and a rotor that is the rotating part. They are designed to exclude moistures and contaminants in severe operating environments. 57. ANS: relatively little leakage, high pressure capability, no shaft or housing wear, no adjustment needed, minimal friction and high efficient. 58. ANS: A bearing machine component that is designed to provide shaft support, positioning and guidance, allow free rotation, and reduce friction between moving parts. 59. ANS: Spur, helical, worm, bevel, planetary, hypoid, spiral bevel, change gears, miter gears, rack and pinion, herringbone. 60. ANS: 70/40 = 1.75 diametral pitch 61. ANS: Compact, high ratios, inexpensive, versaile shaft and mounting configurations. 62. ANS: Gear Number Direction Ratio Speed (RPM) 1 CW CCW 2.57: CW 1: CCW 4.5: CW 1.388:

27 63. ANS: Speed at 200% full load is about 95% of 1800 = 1710 rpm Slip = 5% 64. ANS: a) Indcution Motor b) 1750 rpm c) 200% 65. ANS: DC Shunt motor PROBLEM 66. ANS: See your book (chapter 1) 67. ANS: see your book (chapter 2) 68. ANS: See your book (Chapter 3) 69. ANS: 8*1.2=9.6HP 70. ANS: 15*1.3 = 19.5HP 71. ANS: 35*1.4 = 49HP 7

28 72. ANS: 73. ANS: Hole size = ANS: See Page 114 in your book. 75. ANS: See page 123 in your book 8

29 76. ANS: See Page in your book 77. ANS: Pulley Ratio = 2 S Driven = 875 RPM T Driven = 400 ft-lbs 78. ANS: See Pictures 79. ANS: See Text 80. ANS: 18/36 = 1/2 81. ANS: 82. ANS: Roller Silent Rollerless Leaf 83. ANS: See your text 9

30 84. ANS: Mid-Span must be between 4% to 6% of the center distance. Minimum movement = 0.04 x 30 = 1.2 inches Maximum movement = 0.06 x 30 = 1.8 inches Chain sag is Mid-Span movement divided by /2 = /2 = 0.9 Mid-Span Movement = 1.2 inches to 1.8 inches Chain Sag Range = 0.6 to 0.9 inches 85. ANS: See your notes or text 86. ANS: 498 RPM and 451 in-lbs 87. ANS: DP of the Pinion = 16 DP of the Gear = 16 Center Distance = Backlach Range = inch DP = N/Pitch Dia. C = (Pitch Dia 1 + Pitch Dia 2) / ANS: ratio = 2 10

31 89. ANS: 90. ANS: driver shaft speed = 667 RPM driver shaft torque =750 in-lbs 91. ANS: Driver Shaft Speed = 2000RPM Driver Shaft Torque = 200in-lbs 92. ANS: See your notes 93. ANS: See notes 94. ANS: see notes 95. ANS: Stepper Motor 96. ANS: DC Motor 97. ANS: Single Phase Induction Motor 98. ANS: The Synchronous Machine 11

32 99. ANS: See your notes! 100. ANS: Could be Synchronous, Stepper, Brushless DC 101. ANS: Hint: Another name for a Rotor 12

MECH 1200 Quiz 2 Review

Name: Class: Date: MECH 1200 Quiz 2 Review True/False Indicate whether the statement is true or false. 1. Gears are machined toothed wheels that engage other toothed wheels to transfer power and torque.