Machine Drawing and Design Notes

Course Details

Overview

  • Course Name: Machine Drawing and Design (MIAE 313)
  • Department: Mechanical, Industrial & Aerospace Engineering (MIAE)
  • Instructor: Dr. Hany Gomaa
  • Contact: hany.gomaa@concordia.ca
  • Office: EV-3.269

Required Texts

  • F.E. Giesecke et al., "Engineering Graphics 8th Ed.", Prentice Hall, 2004
  • G.R. Bertoline et al., "Fundamentals of Graphics Communication 7th Ed.", McGraw-Hill, 2019
  • Jensen, C., Jay D. Helsel, Dennis R. Short, "Engineering Drawing and Design", Glencoe-McGraw-Hill, 7th Edition, SI Metric, 1998
  • Jensen, C et al., "Engineering Drawing and Design 7th Ed.", McGraw-Hill, 2008

Course Outline

  • Theory of Shape Description: Chapters 6, 9
  • Dimensioning and Tolerancing: Chapter 8
  • Geometric Dimensioning and Tolerancing: Chapter 16
  • Machine Elements: Threads, Fasteners (Chapter 10)
  • Miscellaneous Types of Fasteners: (Chapter 11)
  • Welding: Chapter 18
  • Couplings, Bearings, Lubricants, and Seals: Chapter 21
  • Gears, Belts, Chains: Chapter 20
  • Assembly Drawing and Design: Chapter 14
  • Course Review

Mechanical Drives Overview

Types of Mechanical Drives

  1. Chain Drive

    • Components: Larger sprocket, smaller sprocket, chain link.

  2. Belt Drive

    • Components: Driver pulley, slack side, tight side, driven pulley.

  3. Gear Drive

    • Components: Pinion, gear.
Power Transmission
  • Gear Drives transmit motion between machine parts and can modify the speed of rotation (increase/decrease).
  • Types include:
    • Spur Gears: Used for parallel shafts.
    • Bevel Gears: Used for intersecting shafts.
    • Worm Gears: Larger gear reductions possible.
    • Rack and Pinion: Converts rotary motion to linear.

Gear Drives Specifications

Gear Drives Overview

  • Gear Ratio: Ratio of the number of teeth on two meshing gears. Determines speed and torque.
    • Larger gear -> higher speed, lower torque.
    • Smaller gear -> lower speed, higher torque.

Definitions

Torque
  • Rotational force that can be multiplied by gears for tasks requiring higher force.
Speed Control
  • Gears allow control of rotational speed for machinery.

Gear Types

  1. Spur Gears: Straight teeth, used for parallel shafts.

    • No axial thrust, may be noisy at high speeds.

  2. Helical Gears: Teeth are angled.

    • Smoother operation, high load capacity. Produces axial thrust.

  3. Bevel Gears: Transmit motion at angles (common at 90°).

  4. Worm Gears: High reduction ratios, potential for self-locking.

  5. Rack and Pinion: Converts rotary motion to linear.

  6. Spiral Gears: Designed for non-parallel shafts, provide smoother operation with less noise.

Key Characteristics in Gear Design

  • Involute Teeth: Follow specific curves; advantageous for smooth operation, constant velocity ratio, ease of manufacturing, and interchangeability.

Tooth Geometry Definitions

  • Pitch Circle: The imaginary circle where gear teeth engage.
    • Addendum: Height above the pitch circle.
    • Dedendum: Depth below the pitch circle.
    • Whole Depth: Overall height of the tooth.

Working Drawings and Specifications

Spur Gear Drawing Techniques

  • Front View: Shows web or arm details minimally; tooth specifications are placed in a separate table.
  • Sectional View: Displays root and outside diameters as solid lines.
Working Drawing Components
  • Gear details include tooth size, pitch diameter, and gear ratio specifications.

Power Transmission Considerations

Selecting Gear Drives

  1. Determine Class of Service: Continuous vs intermittent duty, operation period, load type.
  2. Calculate Power Requirement: Adjust for service factor based on machine load and operating conditions.
  3. Select Gear Pinion/Driven Gear: Based on catalog ratings relative to horsepower requirements.
Examples of Gear Calculations

  1. Calculate Gear Ratios: Based on RPM and teeth count.

    • Example: 36-tooth pinion with 90-tooth gear yields a ratio of 2.5.

  2. Select Based on Catalog Ratings: Must meet or exceed calculated requirements for power rating.

Comparison to Other Drives

  • Gears: High capability, more powerful than belts/chains, allow for speed reductions.
  • Chains: Efficient over longer distances, offer better load handling than belts.
  • Belts: Less power-intensive, adaptable, suitable for flexible applications but with potential slip.

Applications

  • Selection involves various factors including center distance restrictions, required gearing ratios, cost considerations, and maintenance requirements.
Conclusion
  • Understanding gear design, drawing techniques, and selection criteria is crucial in the field of mechanical design and engineering, particularly in the context of machine design and power transmission systems.