Lesson Notes By Weeks and Term v5 - Grade 12
Exam-style integrated EGD tasks (civil and mechanical) – Week 3 focus
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Exam-style integrated EGD tasks (civil and mechanical) – Week 3 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Engineering Graphics and Design
Class: Grade 12
Term: 3rd Term
Week: 3
Theme: General lesson support
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This week, we delve into tackling exam-style questions that integrate both civil and mechanical engineering drawing principles. These integrated tasks are crucial for your final Grade 12 EGD exam, as they assess your ability to apply knowledge from different areas of the syllabus to solve a single complex problem. The skills learned here are directly applicable to various industries in South Africa, from construction and manufacturing to infrastructure development.
Imagine designing a bridge: you need both the civil engineering understanding of structural loads and the mechanical engineering knowledge of moving parts (like drawbridges or maintenance access equipment).
Integrated EGD tasks typically involve a combination of civil and mechanical engineering elements.
These could include: Civil Engineering Elements: Foundations, walls, roofs, roads, bridges, dams, pipelines, and other infrastructure components. You will need to understand structural principles, site plans, elevations, and sections relating to these elements.
Mechanical Engineering Elements: Machines, engines, gears, pulleys, levers, linkages, fasteners, and other mechanical components. You will need to be familiar with orthographic projection, sectioning, assembly drawings, and detail drawings relating to these elements.
Key Concepts: Orthographic Projection: The foundation of all EGD drawings. Remember the principles of first-angle projection (used in South Africa). Front View, Top View, and Right/Left Side Views are derived from projecting the object onto mutually perpendicular planes.
Sectioning: Used to reveal internal details that would otherwise be hidden. Understand the different types of sections (full, half, offset, removed) and the correct use of section lining (hatching). Always indicate the cutting plane with a cutting plane line and viewing arrows.
Assembly Drawings: Show how multiple components fit together to form a complete system. Assembly drawings usually include a parts list or bill of materials. Understand exploded views and their purpose.
Detail Drawings: Provide complete and accurate information for the manufacture of a single component. Detail drawings include all dimensions, tolerances, surface finishes, and materials required.
Geometric Construction: Many integrated tasks require the application of geometric principles to solve problems related to intersections, tangencies, and transitions between civil and mechanical elements. Brush up on constructing tangents to circles, bisecting angles, and dividing lines into equal parts.
SANS Standards: Adherence to South African National Standards (SANS) is essential for all EGD drawings. Pay attention to line types, lettering, dimensioning, and symbols as defined by SANS.
Example 1: Integrated Water Tank Support Structure
Imagine a rural community in South Africa relying on a raised water tank for its water supply. The task is to draw the front view and top view of the integrated structure. The civil element is the concrete foundation and supporting pillars. The mechanical element is the water tank itself, including the inlet/outlet pipes and access ladder.
Step 1: Sketch the Basic Layout: Begin by sketching a rough layout of the foundation, pillars, and water tank. This helps visualize the overall design and spatial relationships.
Step 2: Draw the Front View: Start with the foundation at ground level. Accurately represent the pillars, ensuring they are correctly positioned and dimensioned. Show the water tank resting on the pillars. Include the access ladder on the side of the tank.
Step 3: Draw the Top View: Project the important features from the front view to the top view. Show the circular shape of the water tank. Indicate the position of the pillars and the access ladder. Show the outline of the foundation.
Step 4: Add Dimensions and Annotations: Dimension the overall height and width of the structure. Dimension the diameter of the water tank and the spacing between the pillars. Add notes to indicate materials and other relevant information.
Key Considerations: Ensure accurate alignment between the front view and top view. Use appropriate line types to differentiate between visible edges, hidden edges, and center lines. Adhere to SANS dimensioning standards.
Example 2: Sectional View of a Bridge Support
A bridge pier (civil element) contains a mechanical dampening system to absorb vibrations from traffic. The task is to draw a sectional front view to show the internal components of the dampening system.
Step 1: Determine the Cutting Plane: Decide on the location of the cutting plane to reveal the most important details of the dampening system. Indicate the cutting plane with a cutting plane line and viewing arrows.
Step 2: Draw the Sectioned Front View: Draw the exterior of the bridge pier. Then, draw the internal components of the dampening system, such as springs, pistons, and hydraulic cylinders. Section the areas that are cut by the cutting plane, using appropriate section lining.
Step 3: Add Dimensions and Annotations: Dimension the key features of the dampening system, such as the diameter of the pistons and the length of the springs. Add notes to indicate materials and operating principles.
Key Considerations: Ensure the correct section lining is used to represent different materials. Avoid sectioning thin components such as washers or gaskets. Show hidden details behind the cutting plane as dashed lines.