Shafts, Keys, Hubs and Fits Quiz
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Questions and Answers

What is a primary factor when selecting a coupling for a specific application?

  • The coupling's ability to transmit rated torque at required R.P.M. (correct)
  • The weight of the coupling
  • The aesthetic appeal of the coupling
  • The color of the coupling

    • Why are shear pins used in couplings?

  • To enhance the aesthetic of the coupling
  • To provide overload protection by failing at a predetermined shear strength (correct)
  • To decrease the weight of the assembly
  • To improve thermal conductivity

    • Which type of coupling would be most appropriate for use where shafts are separated by a large space?

  • Fluid coupling
  • Pin & Bushing coupling
  • Spacer coupling
  • Floating shaft coupling (correct)

    • What is the main advantage of a fluid coupling?

    <p>Provides excellent vibration absorption and smooth starts (B)</p> Signup and view all the answers

    Which of the following is NOT a preliminary check for coupling alignment?

    <p>Pipe flanges are color-coded (B)</p> Signup and view all the answers

    What key characteristic does a spacer coupling offer?

    <p>Allows for ease of maintenance without disturbing alignment (D)</p> Signup and view all the answers

    Which step is NOT part of the four basic steps of coupling alignment?

    <p>Measure vibration frequencies (C)</p> Signup and view all the answers

    What is a characteristic of a dry fluid coupling?

    <p>Provides a soft start with centrifugal force packing the dry shot (A)</p> Signup and view all the answers

    What is the purpose of a clutch?

    <p>To enable start and stop of a drive without changing the speed of the prime mover. (B)</p> Signup and view all the answers

    Which of the following methods is NOT typically used to actuate mechanical friction clutches?

    <p>Magneto-static (C)</p> Signup and view all the answers

    What differentiates the movable side from the stationary side in coupling alignment?

    <p>The movable side is typically the driver that needs adjustment. (D)</p> Signup and view all the answers

    When aligning shafts, when should pipe connections be made to a pump?

    <p>Prior to alignment. (C)</p> Signup and view all the answers

    What is the typical maintenance procedure for checking friction clutches?

    <p>Check for oil leaks and cracks in the friction material. (A)</p> Signup and view all the answers

    What is a primary difference between a brake and a clutch?

    <p>A clutch mounts to two shafts, whereas a brake mounts to a shaft and is fixed. (B)</p> Signup and view all the answers

    Which formula is used for calculating the distance between holes in coupling alignment?

    <p>Dist. between holes = Øwiped * TIR / 2 (A)</p> Signup and view all the answers

    What is NOT a classification of clutches?

    <p>Hydraulic (B)</p> Signup and view all the answers

    What is the primary function of a coupling?

    <p>To join shafts for power transmission (C)</p> Signup and view all the answers

    What type of fit exists when the largest allowable shaft diameter is smaller than the smallest allowable bore diameter?

    <p>Clearance fit (D)</p> Signup and view all the answers

    How can a worn shaft be repaired?

    <p>Spray weld (B)</p> Signup and view all the answers

    Which of the following tolerances is correct for shafting up to 4 inches in diameter?

    <p>+.000 - -.004&quot; (B)</p> Signup and view all the answers

    What is the coefficient of expansion (COE) formula used for determining the expansion of a shaft due to temperature rise?

    <p>∆𝑙 = 𝑙 · 𝐶𝑂𝐸 · ∆𝑇 (B)</p> Signup and view all the answers

    What is critical about rigid couplings?

    <p>They require perfect alignment (D)</p> Signup and view all the answers

    Which type of coupling is ideal for absorbing vibration and slight misalignment?

    <p>Rubber insert jaw coupling (A)</p> Signup and view all the answers

    What should be true about the length of screws when tightening over a key?

    <p>They should not extend out of the hole (D)</p> Signup and view all the answers

    What is the purpose of adding flanges on a timing belt pulley?

    <p>To prevent the belt from running off the pulley (C)</p> Signup and view all the answers

    What is the recommended tension for belts when no manufacturer's specifications are available?

    <p>1/32 per inch of center distance (B)</p> Signup and view all the answers

    Why might the bearings in an electric motor overheat when using a V-belt?

    <p>Excessive belt tension (A)</p> Signup and view all the answers

    What is indicated by a shiny bottom of a sheave?

    <p>The belt is worn or damaged (C)</p> Signup and view all the answers

    What component connects two roller links within a roller chain?

    <p>Master link (A)</p> Signup and view all the answers

    Which type of link is used to connect outer and inner roller links in a chain?

    <p>Offset link (C)</p> Signup and view all the answers

    What is a unique advantage of a 3V belt compared to an 'A' belt?

    <p>Ability to transmit more horsepower (B)</p> Signup and view all the answers

    What is one common method for retaining chain links to pins?

    <p>Spring clips (B)</p> Signup and view all the answers

    What is a primary advantage of chain drives over belts and gears?

    <p>They are 98% efficient over long distances. (C)</p> Signup and view all the answers

    When are hardened teeth primarily used on sprockets?

    <p>In heavy loaded drives with 25 teeth or less. (C)</p> Signup and view all the answers

    What characterizes a double pitch chain?

    <p>Links that are twice as long, used in slow speed environments with light loads. (D)</p> Signup and view all the answers

    What is the overall gear ratio of a system where an input gear with 20 teeth drives a 48 tooth gear, which then drives an 18 tooth gear that meshes with a 60 tooth output gear?

    <p>2.0 (A)</p> Signup and view all the answers

    What is the minimum required wrap on a sprocket?

    <p>120 degrees (B)</p> Signup and view all the answers

    What type of bearing is commonly used with helical gears due to its capability to support axial loads?

    <p>Angular contact bearings (D)</p> Signup and view all the answers

    Which of the following is NOT a method for lubricating chains?

    <p>Grease application (C)</p> Signup and view all the answers

    If a gearbox runs too hot, which of the following is NOT a reason for overheating?

    <p>Excessive lubrication (D)</p> Signup and view all the answers

    What is the purpose of an EP additive in gears?

    <p>To reduce friction and prevent wear. (C)</p> Signup and view all the answers

    What is backlash in gears?

    <p>The extra distance between gear teeth on the pitch circle. (B)</p> Signup and view all the answers

    When setting the end float of a shaft in a worm and wheel gearbox, which adjustment is crucial before finalizing the gear mesh?

    <p>Adjusting the worm's axial position (D)</p> Signup and view all the answers

    Which of the following describes a helical gear's unique characteristic?

    <p>Teeth that engage gradually, reducing noise and vibration. (C)</p> Signup and view all the answers

    What would be the speed of a 12ӯ conveyor drum driven by a chain drive from a 20:1 gearbox at an input speed of 1725 RPM?

    <p>86.25 SFPM (D)</p> Signup and view all the answers

    Study Notes

    Shafts, Keys, Hubs, and Fits

    • Two major stresses on shafts are torsion and bending
    • A fillet/radius is machined on a reduced diameter shaft end to reduce stress concentration
    • Keys are used between shafts and hubs for positive power transmission between components
    • Key types and applications include:
      • Straight: rectangular, boxed or open, removable or fixed
      • Flat: reduced hub diameters, taper sleeve bushings, low profile hubs
      • Woodruff: semi-circular, used for light loads
      • Tapered: 1/8 per foot taper, not for cast iron, self-holding
      • Gib Head: tapered key application with head, removed by fox wedges
      • Step: key seat and keyway different sizes, for repair
      • Offset: similar to step, keyways not centered
      • Saddle: rectangular, concave bottom, for shaft radius, no key seat, light loads, unidirectional temporary/emergency
      • P&W: rectangular, radiused ends, boxed/closed key seat
      • Feather: one of the rectangular shapes, held in with screws, clearance fit
    • Woodruff keys are sized by width in 32nds and diameter in 8ths (e.g., #3208 is 1" wide, Ø1")
    • Gib Head keys have a taper of 1/8 per foot (or 1:96)

    Coupling Alignment

    • Interference fit: smallest allowable shaft diameter is larger than largest allowable bore diameter
    • Clearance fit: largest allowable shaft diameter is smaller than smallest allowable bore diameter
    • Transition fit: tolerance can result in either a clearance or interference fit
    • Coupling alignment involves several considerations like torque, RPM, and shaft misalignment
    • Considerations for selecting coupling include availability of spare parts, ease of maintenance, space requirements (radial and axial) and vibration

    Clutches and Brakes

    • Five methods of actuating mechanical friction clutches: pneumatic, hydraulic, electric, manual, magnetic
    • Torque (overload), mechanical, electromagnetic, magnetic, friction, torque limiting are three classifications of clutches
    • Clutch purpose is to enable start and stop of a drive without changing prime mover speed, providing soft starts and overload protection
    • A brake differs from a clutch in how it mounts: clutch mounts to two shafts, while a brake mounts to a shaft and is fixed to a machine
    • Gaps between friction plates and linings are set with feeler gauges until manufacturer's required gap is achieved; maintenance involves checking for oil leaks, cracks, and dust build up

    Belt Drives

    • Steps in installing new V-belts involve reducing center-to-center distance and installing new belt, tension is checked after 12-24 hours
    • Arc of contact is the area of contact between belt and pulley surfaces, determined by diameter, center-to-center distance, and take-up device
    • V-belt classifications include 3V, 5V, and 8V
    • Sheave alignment is performed using a straight edge at four points
    • Ensuring shafts are parallel and belts are matched is crucial in multi-belt drives
    • Methods for checking belt tension include use of a belt tensioning tool

    Gear Drives

    • Gear drives increase speed (overdrive) or decrease speed (reducer) depending on gear ratios
    • Finding the diametral pitch (DP) of a damaged gear involves calculating the number of teeth divided by the pitch diameter
    • Several gear types and applications are detailed (spur, rack and pinion, helical, double helical, bevel, miter, worm, and hypoid)
    • Backlash is the distance between gear teeth on the pitch circle
    • Gearbox lubrication is important, especially for vertical shaft gearboxes
    • Wear patterns in gear teeth are caused by factors including overloading, inadequate lubrication etc; this leads to overheating

    Additional Notes

    • Various elements of different power transmission methods such as shafts, keys, hubs, couplings, clutches, brakes, belt drives, and gear drives are described, along with their functions and applications.
    • Several methods of calculations are provided, including those involving gear ratios, RPM, and belt tension

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    Millwright Level II Power Transmission Review PDF

    Description

    Test your knowledge on shafts, keys, and their applications in mechanical systems. This quiz covers major stresses, key types, and how they function in power transmission. Perfect for engineering students looking to reinforce their understanding of these fundamental concepts.

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