Unit 1 2 3
Topic 2: Communication skills
• Purpose of graphics: develop and communicate ideas. • Conventions: outlines (thick/dark); construction lines (thin/feint); hidden detail (dashed); centre lines (chain dash-dot); scaling up and scaling down; dimensioning (in mm).
• Working drawing techniques for planning: – Single view flat 2-D drawing with dimensions, line types and scale. – Isometric – using underlying isometric grid (Term 1) and simple instruments (Term 3)
• Artistic drawing: Double vanishing point perspective with colour, texture and shading. – Sketching – using pencil, ruler and blank paper. – Enhancing drawing to promote realism using colour, texture, shading and shadows.
Unit
1 2
3 4
Topic 3: Mechanical systems and control • Revision: mechanical advantage. Well-designed machines give “mechanical advantage”
• All complex machinery consists of combinations of simple mechanisms. – The wedge: e.g. inclined plane or ramp, door wedge, knife blade, etc. – The wheel and axle: e.g. from bicycle to shopping trolley.
• Gears (wheels with wedges for teeth): – Show how meshing of two spur gears causes counter-rotation. – Show how introducing an idler gear between two spur gears synchronises rotation of the driver and driven gears.
– Gear ratios: Show how different sized gears result in a change in the velocity ratio as well as an ‘opposite’ change in the force ratio – if force increases, speed decreases, and vice versa.
5
• Mechanisms that change the direction of movement: – The cam: show how a cam converts rotary motion into reciprocating motion. Compare an eccentric wheel and a snail cam.
– The crank: an adaptation of a second-class lever. Show how a crank converts rotary motion into reciprocating motion.
• Graphic skills: learners draw an artist’s impression of one of each of the above mechanisms in their books using colour, shading and texture.
16 73–76 2
Learner’s Book page
38–43 44–48 49–53
Learner’s Book page
56–58 59–62
63–66 67–72
Time
allocation (2 hours)
2
Time
allocation (2 hours)
4
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