TERM – 1ST TERM
WEEK FIVE
Class: Senior Secondary School 2
Age: 16 years
Duration: 40 minutes of 5 periods each
Date:
Subject: Technical Drawing
Topic: SURFACE DEVELOPMENT OF OBLIQUE PYRAMIDS AND CONES
SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to
I.) Develop an oblique pyramid
II.) Develop an oblique cone.
INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source
INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,
INSTRUCTIONAL PROCEDURES
PERIOD 1-2
PRESENTATION
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TEACHER’S ACTIVITY
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STUDENT’S
ACTIVITY
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STEP 1
INTRODUCTION
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The teacher guide students to develop oblique pyramid as well as oblique cone.
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Students listens attentively to the teacher and participate actively.
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STEP 2
NOTE TAKING
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The teacher writes a summarized
note on the board
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The students
copy the note in
their books
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NOTE
SURFACE DEVELOPMENT OF OBLIQUE PYRAMIDS AND CONES
Development of oblique cone
An oblique cone is one whose vertex does not align with the centre of the base
Procedure
- Draw the plan of the base and divide it into 12 equal parts
- Locate point A¹ and join each division on the plan to it.
- Project this points upward to the reference line X-Y to obtain the base of the elevation BC
- Join each point on BC to the vertex A to obtain the elevation.
- Construct the true length to be used in the development by drawing a reference line X¹Y¹ and transfer the lengths A¹1, A¹2, A¹3 etc from the plan to it.
- Join each point on the vertex A to obtain the true length.
- At any convenient position, draw a line equal to the true length A1. I e line A1 on the development.
- With A as the centre on the development and a radius of A2 on the development, swing an arc.
- With 1 on the development as the centre, radius equal to the distance 1-2 on the plan, cut previous arc to obtain 2 on the development.
- With A on the development as the centre and radius A3 measured from the true length, swing an arc.
- With 2 on the development as the centre and radius equal to the distance 2-3 on the plan, cut the previous arc to obtain point 3 on the development.
- Repeat the same procedure to obtain 4, 5, 6 and 7 to finish one half of the development. Complete the other half and connect the points using a french curve to complete the development.
![](https://lessonotesimages.fra1.cdn.digitaloceanspaces.com/SS2_TD1_WK5_1.jpg)
Development of oblique hexagonal pyramid
Procedure:
- Draw the given elevation and plan
- From the elevation, side AB and AE are represented in the true length but AC and AD are not.
- To get the true lengths of AC and AD, draw a line equal to the vertical height at right angle to point Ai i.e AA1. Join A1 to C and D to obtain the true lengths A1C and A1D respectively.
- Draw a line equal to the true length AE. With A on the development as the centre and radius A1D (true length of AD) swing an arc each side of AE.
- Now, with E on the development as the centre and radius ED on the plan (length of one side), swing an arc to cut each of the previous arcs at point D.
- Again, with A on the development as the centre, and radius A1C (true length of AC), swing an arc to the side of AD.
- Then, with D as the centre and radius DC on the plan, swing an arc to cut the previous one at C.
- Finally, with A as the centre and radius A1B(true length of AB), swing an arc to the side of AC. With C as the centre and radius CB, swing an arc to cut the previous one at B.
- Join the points to complete the development. If the base cover is required, then draw a regular hexagon on one of the base edges of the development.
![](https://lessonotesimages.fra1.cdn.digitaloceanspaces.com/SS2_TD1_WK5_2.jpg)
EVALUATION: 1. The figure below shows, in first angle projection, the elevation and an incomplete plan of a regular hexagonal oblique pyramid, truncated by a plane XX.
(a) the given elevation;
(b) a complete plan;
(c) the surface development making p-p the seam.(WAEC)
![](https://lessonotesimages.fra1.cdn.digitaloceanspaces.com/SS2_TD1_WK5_3.png)
CLASSWORK: As in evaluation
CONCLUSION: The teacher commends the students positively