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Topics. Introduction Shaft Design Stresses and Loads on Shafts Shaft Fits Shaft Locking Devices Exercise Questions Note: Refer to Chapter 7 in the text. Introduction. Shafts are used to transmit mechanical power such as the propeller shafts in vehicles. Applications of shafts:

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  1. Topics • Introduction • Shaft Design • Stresses and Loads on Shafts • Shaft Fits • Shaft Locking Devices • Exercise Questions • Note: Refer to Chapter 7 in the text.

  2. Introduction • Shafts are used to transmit mechanical power such as the propeller shafts in vehicles. • Applications of shafts: • - To transmit power • - To extend other shafts • - To provide the rotary motion needed by other components such as in rollers and printing press machines. • Shafts are usually made of steel. • Some materials are used in making shafts: - Cold Rolled Steel: most common due to its low cost - Hardened Steel: heated rolled steel. Stronger than the cold rolled shaft. - Stainless steel Reference: Amatrol Mechanical Drives 1, LAP 3

  3. Shaft Design • Shafts may be designed with ‘turn downs’ • These shafts have smaller diameters at the ends. • When shafts are turned down, a large shaft fillet is used to reduce stresses as possible. • Refer to figures 7-2 and 7-3 in the text (pp. 134-135) Fillet Turn Down

  4. Loads and Stresses on Shafts Shear Forces Tensile Forces Compressive Forces Bending Moments Torsions

  5. Shaft Fits • When two objects are mated, there will be a difference between their actual size and the dimensional tolerance limit – know as the “fit” or amount of tightness

  6. Shaft Fits • Clearance fit: the mating parts have a clearance between them. Also known as slip, slide, or loose fit. • Transition fit: no clearance is present. It is also known as line-to-line fit. In this case pressing is required. • Interference fit: The shaft diameter is larger than the diameter of the hole of the component to be mounted. Some types of it are: press and shrink fits. An Arbor Press is used to mount the components onto the shafts

  7. Shaft Locking Devices used to mount sheaves, and sprockets • Taper-Lock Bushings – Bushing squeezes the shaft as bolts are drawn in. 8 degree taper Quick Detachable (QD) Tapered Bushings – Same as taper- lock with 4 degree taper A Quick Detachable (QD) Tapered Bushing

  8. Shaft Locking Devices • Split-Taper Bushing • Keyless/Compression Bushings have high torque holdings

  9. Exercise Questions • What is the purpose of the propeller shaft in a car? Transmitting mechanical power in the form of torque to the rear axle. • Name five types of loading and moments that shafts can be subjected to: 1) Compressive forces 2) Tensile forces 3) Shear forces 4) Bending moments 5) Torsion

  10. What three types of shaft fits? Clearance, line-to-line, and interference fits • Name three types of bushings that can be used to mount components on shafts? 1. Taper-Lock Bushuings 2. Quick Detachable Tapered Bushings 3. Split-Taper Bushings 4. Keyless/Compression Bushings 5. Describe how to mount a component on a shaft with a shrink fit? The shaft may be freezed in liquid nitrogen to shrink, then the component is mounted on it. 6. What is a disadvantage of shrink fitting? You are limited by time needed to mount the component on the shaft before the shaft retains its regular dimensions.

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