Machine Drawing and Design Notes

Course Overview

  • Course Title: Machine Drawing and Design (MIAE 313)

  • Instructor: Dr. Hany Gomaa

    • Email: hany.gomaa@concordia.ca

    • Office: EV-3.269

  • References:

    • Main Texts:

    • Jensen, C. et al., Engineering Drawing and Design, 7th Ed.

    • 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

    • Additional References:

    • Jensen, C. et al., Engineering Drawing and Design with Extra Chapter on Welding, 2014

  • Course Outline:

    1. Theory of shape description (Chapters 6, 9)

    2. Dimensioning and tolerancing (Chapter 8)

    • Limits and Fits

    • Surface finish

    1. Geometric dimensioning and tolerancing (Chapter 16)

    2. Machine elements: threads, fasteners (Chapter 10)

    3. Miscellaneous types of fasteners (Chapter 11)

    4. Welding (Chapter 18)

    5. Coupling, Bearings, Lubricants and Seals (Chapter 21)

    6. Belts, Chains and Gears (Chapter 20)

    7. Assembly Drawing and Design (Chapter 14)

    8. Course Review

Shaft Couplings

  • Definition: Essential mechanical components that connect two shafts to transmit power.

  • Functions of Shaft Couplings:

    • Power Transmission: Mainly used to transmit torque from one shaft to another.

    • Misalignment Compensation:

    • Types:

      • Parallel Misalignment: Centerlines are parallel but offset, causing stress on coupling and bearings.

      • Angular Misalignment: Centerlines intersect at an angle, leading to vibrations.

      • Axial Misalignment: Shafts shift longitudinally due to thermal expansion.

    • Vibration and Shock Absorption: Couplings can dampen vibrations and absorb shock loads, protecting machinery.

Types of Shaft Couplings

  1. Rigid Couplings:

    • Designed for perfect alignment; high torque transmission.

    • No misalignment compensation.

    • Applications: Heavy-duty machinery where precise alignment is crucial.

  2. Flexible Couplings:

    • Designed to accommodate misalignment (e.g., jaw couplings, disc couplings).

    • Applications: Scenarios with expected shaft misalignment.

  3. Fluid Couplings: Using hydraulic fluid to provide smooth transmission.

  4. Magnetic Couplings: Non-contact torque transmission using magnetic forces.

Key Considerations for Coupling Selection

  • Rating for Power Transmission: Typically rated in horsepower or kilowatts per 100 RPM.

  • Service Factor: Depends on the load and type of duty (e.g., smooth vs. cyclic torque variations).

Universal Joints

  • Description: Classic joints used to connect two shafts; transmits torque at angles.

  • Types of Universal Joints:

    • Cardan Joints: Simple design; not suitable for constant velocity.

    • Constant Velocity Joints: Designed to maintain constant output shaft speed; smoother transmission.

Bearings

  • Function of Bearings:

    • Reduce friction during movement between machine elements (rotary or linear).

    • Support and guide moving parts, ensuring they stay in their intended positions.

  • Types of Bearings:

    • Plain Bearings: Rely on sliding surfaces; examples include bushings.

    • Rolling Element Bearings: Include ball bearings and roller bearings.

Classification of Bearings

  1. Plain Bearings: Use sliding action; often require lubrication.

    • Materials: Metal, polymers, composites.

    • Applications: Used widely in rotating shafts, machinery, automotive engineering.

  2. Rolling-Element Bearings: Utilize rolling balls or rollers to minimize friction.

    • Common Types: Ball bearings (lower load capacity, higher speed), cylindrical roller bearings (higher load capacity).

    • Applications: Used in equipment where reducing friction is critical.

Key Design Parameters for Bearings

  • Load Carrying Capacity: Bearing type and design must support the intended load.

  • Friction Levels: Reducing friction increases efficiency and longevity.

  • Lubrication: Crucial for operational efficiency; methods vary (hydrodynamic, hydrostatic, etc.).

Conclusion

Understanding the various coupling types, universal joints, and bearings, including their classifications, applications, and operational principles, is essential for effective mechanical design and engineering.