TERM – 1^ST 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

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher guide students to develop oblique pyramid as well as oblique cone.

Students listens attentively to the teacher and participate actively.

STEP 2

NOTE TAKING

The teacher writes a summarized

note on the board

The students

copy the note in

their books

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.

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.

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;

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively

Lesson Notes By Weeks and Term - Senior Secondary 2