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. 2. Backlash is the measurable space at the pitch circle, between two meshing gears, on the non-driving side fo the face. 3. In a gear set the smaller gear is often referred to as the pinion. 4. The diametral pitch (DP) of a gear is the number of teeth in the gear for each inch of outside diameter. 5. American Gear Manufacturers Association defines certain characteristics and terminology for gearing. 6. A Three-stage or tripple reduction gearbox will have four shafts in it. 7. Modular gears have metric specifications and dimensions. 8. Planetary gearing involves the use of an internal gear meshing with sun and planet gears. 9. Generally, the higher the ratio of a gearbox, the less its efficency? 10. The thermal rating of a gearbox is the maximum horsepower or torque that can be transmitted continuously through the drive, based on its ability to dissipate heat generated internally. 11. Backstops are used on gearboxes to prevent reverse rotation and back-driving of the connected load. 12. Helical gear teeth are cut at a particular helix angle to the shaft. 13. The distance between the center of the pinion shaft to the center of the gear shaft is know as the center distance. 14. The root clearance is the distance of gap from the top of one gear tooth to the bottom of the mating gear tooth. 15. Backlash is defined as the clearance between the back of the engaged tooth of the driver gear and the front tooth of the driven gear immediately behind it as measured along the pitch circle. 16. For two gears to mesh properly, their pitch circles should be tangent to each other. 17. Soap is considered a lubricant. 18. Lithium grease is one of the most widespread greases used in industry. 19. Calcium soap greases are capable of absorbing a large percent of their volume with water. 1
Name: Multiple Choice Identify the choice that best completes the statement or answers the question. 20. Calculate the gear ratio given the following information: Driven Gear = 65 Teeth Driver Gear = 20 Teeth a. 3.25 c. 1300 b. 0.308 d. None of these 21. Calculate the Driven shaft speed. a. 5400 RPM c. 7200 RPM b. 3 RPM d. 600 RPM 22. Calculate the Driven shaft Torque. a. 10 in-lbs c. 60 in-lbs b. 90 in-lbs d. 45 in-lbs Short Answer 23. What is Tribology? 24. What affect does heat have on the viscosity of a lubricating oil? 2
Name: 25. Define the term Saybolt Universal Seconds. 26. What determines the thickness of a lubricating film? 27. What is the pour point of an oil? 28. What is an Elasto-hydrodynamic Lub Film? 29. What is the purpose of putting additives in lubricating oil? 30. List some of the advantages of synthetic lubricating oil. 31. Why is grease consistency important? 32. Whay is grease compatibility an important issue? 33. What is one of the chief advantages of an automated lubricant system? 34. Why is safety a concern when handling lubricants? 35. What is the term Pitch as it applies to a thread? 36. What is the term lead as it apples to a thread? 37. If a thread has 40 threads per inch, what is its pitch? 38. If a thread has 20 threads per inch what is its lead? 39. Describe the uniform thread series. 40. Thoroughly describe a 1/4-20 3B thread. 41. Thoroughly describe a 1/2-12 2A thread. 42. Thoroughly describe a M10 thread. 43. Describe the proper method to tap a hole. 44. What size hole should be drilled to tap a 1/4-20 tapped hole? 45. What size hole should be drilled to tap a 1/2-13 tapped hole? 46. What size hole should be drilled to tap a 5/16-24 tapped hole? 47. What size hole should be drilled to tap a 3/8-16 tapped hole? 48. What size hole should be drilled to tap a 3/8-24 tapped hole? 3
Name: 49. Describe at least 2 methods to methods to remove a broken stud from a hole. 50. Name five different types of gears. 51. Use the Compound Gear train below to answer the questions below: Gear A = 10 teeth, B = 10 teeth, C = 40 teeth, D = 15 teeth, E = 50 teeth, F = 15 teeth, G = 30 teeth. Gear A meshes with gear B. Gear C meshes with D, which also meshes with Gear E. Fear F meshes with gear g. Gears B and C are on a common shaft. Gears E and F are on a common shaft. If A is the driving gear and rotating clockwise, which direction is gear G rotating? What is the ratio of this gear train? If gear A is connected to the prime mover and rotated at 1750 RPM, how fast will gear G rotate in revolutions per minute (RPM)? 52. What is the diametral pitch of a gear with 70 teeth that has a pitch diameter of 40? 53. Describe the advantages of a worm gear drive. 4
Name: 54. Complete the table below: Gear Number Direction Ratio Speed (RPM) 1 NA 2 3 4 5 Problem 55. 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. 5
Name: 56. 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 = 57. Calculate the driven shaft speeds of the two output gears of the gear drive and the driven shaft torque. Gear 1 = RPM Gear 2 = RPM Driven Shaft Torque = in-lbs 6
Name: 58. Calculate the driven shaft speed and driven shaft torque of the compound gear drive system. Driven Shaft Speed = RPM Driven Shaft Torque = in-lbs 59. 1. I have a gear system of the following design: Gear 1 48 teeth, Pitch diameter 3.00 inches Gear 2 60 teeth, Pitch diameter 5 inches Gear 3 24 teeth, Pitch diameter 2 inches Gear 4 60 teeth, Pitch diameter 3 inches Which two gears will mesh correctly? Why? (Hint you need to find a parameter of the gears.) 7
Name: 60. A motor is running a mechanical system as shown below. Identify each component in the diagram using the component number given in the table. Fill out the table. Component Speed (RPM) Torque (inch-lb) Reduction Ratio 1. High speed pinion 2. High speed gear 3.Intermediate pinion 4. Intermediate gear 5. Low speed pinion 6. Low speed gear What is the overall reduction ratio of the gearbox? 8
Name: Speed Torque (inch-lb) Drive ratio 7. Driver Sprocket 8. Driven sprocket What is the power delivered to the output sprocket shaft? Show your calculation(s). 61. Use the chart to determine what size hole should be drilled to tap a 1/4-20 tapped hole? Hole size = 62. Define Low Head Cap Screws, Flat Head Cap Screws, Button Head Cap Screws, Socket Shoulder Screws, Machine Screws, Set Screws. 63. Be able to identify common types of nuts. 64. Define Dowel Pins, Cotter Pins, Retaining Rings, Keys. 9
MECH 1200 Quiz 2 Review Answer Section TRUE/FALSE 1. ANS: T 2. ANS: T 3. ANS: T 4. ANS: F should be over pitch diameter, not outside diameter. 5. ANS: T 6. ANS: T 7. ANS: T 8. ANS: T 9. ANS: T 10. ANS: T 11. ANS: T 12. ANS: T 13. ANS: T 14. ANS: T 15. ANS: T 16. ANS: T 17. ANS: T 18. ANS: T 19. ANS: T MULTIPLE CHOICE 20. ANS: A Driven/Driver 21. ANS: D 22. ANS: B SHORT ANSWER 23. ANS: The study of how lubrication affects friction and moving parts. 1
24. 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. 25. ANS: It is how lubricants are measured in the United States. The time, inseconds, required to fill the flask to a prescribed amount. 26. ANS: The thickness of the generated fil depends on the operating conditions such as: velocity, loads, lubicant viscosity, and the pressure/viscosity relationship. 27. ANS: Pour point is the lowest temperature at which oil will flow in a controlled laboratory test. 28. 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. 29. 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. 30. 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. 31. ANS: So that it does not deform under an applied force. 2
32. 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. 33. ANS: The lubricant is isolated from contamination and metered out under a controlled pressure to where it is needed. 34. 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. 35. ANS: The distance between thread crests. 36. ANS: How far a thread advances in one revolution. 37. ANS:.025 inches 38. ANS: same as its pitch so 0.050 39. ANS: In 1948 representatives fromt he US, Canada, and Great Britain agreed upon a common system for threads. It was based upon the best of both country s standards. 40. ANS: Major diameter is 1/4 inch, 20 threads per inch 41. ANS: Major diameter is 1/2 inch, 13 threads per inch. 42. ANS: Metric thread with a major diameter of 10 mm 3
43. ANS: Choose the correct drill to use from a tap chart, choose the correct tab, keep the tap vertical, keep eyes on the tap, don t break the tap, make a few turns and reverse the tap to break the chips, cutting fluid should be used. 44. ANS: #7 45. ANS: 27/64 46. ANS: l 47. ANS: 5/16 48. ANS: Q 49. ANS: Use a Drill-Out tool, stude remover, Chisel, Center punch and drill. 50. ANS: Spur, helical, worm, bevel, planetary, hypoid, spiral bevel, change gears, miter gears, rack and pinion, herringbone. 51. ANS: CW 10 10 * 15 40 * 50 15 * 30 15 5 2 700 RPM 52. ANS: 70/40 = 1.75 diametral pitch 4
53. ANS: Compact, high ratios, inexpensive, versaile shaft and mounting configurations. 54. ANS: Gear Number Direction Ratio Speed (RPM) 1 CW 2000 2 CCW 2.57:1 777.78 3 CW 1:4.5 3500 4 CCW 4.5:1 777.78 5 CW 1.388:1 560 PROBLEM 55. ANS: 498 RPM and 451 in-lbs 56. ANS: DP of the Pinion = 16 DP of the Gear = 16 Center Distance = 1.875 Backlach Range = 0.005-0.015 inch DP = N/Pitch Dia. C = (Pitch Dia 1 + Pitch Dia 2) / 2 57. ANS: Gear 1 = 250RPM Gear 2 = 250RPM Driven Shaft Torque = 175 in-lbs Total torque/ratio (200+150)/ 2 58. ANS: Driven Shaft Speed = 750RPM Driven Shaft Torque = 1500 in-lbs 5
59. ANS: Gear 2 and Gear 3, they have the same diametral pitch 48/3 = 16 60/5 = 12 24/2 = 12 60/3 = 20 6
60. ANS: 61. ANS: Hole size = 7 62. ANS: See Page 114 in your book. 7
63. ANS: See page 123 in your book 64. ANS: See Page 123-124 in your book 8