Lesson Notes By Weeks and Term - Senior Secondary 2

TERM – 2^ND TERM

WEEK FOUR - FIVE

Class: Senior Secondary School 2

Age: 16 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Technical Drawing

Topic: CONVERSION OF ORTHOGRAPHIC VIEWS TO ISOMETRIC

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

I.) Convert orthographic views to isometric forms.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers, demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures,

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

NOTE

CONVERSION OF ORTHOGRAPHIC VIEWS TO ISOMETRIC

There are basically three procesess for converting objects in orthographic forms to isometric forms, these includes: The horizontal view, the vertical view, and the grid line methods.

1. Horizontal view method. In this case, the Front view and the End view are the only faces needed to accomplish the task. That means they are placed side by side to each other. To assemble or to convert the given views into an isometric object, isometric axis is first constructed.
2. Vertical view method.

The method used here is the same asthe one used in (1) above. The only difference is that the F(V) and the P(T) are used. The Plan Top is placed above or below the Front View instead of putting them side by side. Then, the Plan Top is used to cover the Front view, as if it roofs it. That done, the object can be completed.

3. Grid line method.

In this method, the position of views does not matter. What matters the most is

the total length, total height and total width of the object to be drawn. With these three measurementsgotten from the given faces, a cube or a cuboid is drawn in isometric form. Then, the face or view having distortions such as curves, circles, projected or extruded parts and twists are constructed to the dimensions given in the question that is in orthographic form. That same face is divided into grid lines of equal distances apart. These divisions could be in the spaces of 5mm, less or more, depending on the size of the selected view or face.The division is then transfer to its position or face on the cube or cuboid drawn in isometric form.

General procedure

Converting from orthographic projection to isometric projection involves transforming a two-dimensional representation of an object into a three-dimensional representation that maintains equal scale along all three axes. Below is a simplified procedure:

1. In orthographic projection, all parallel lines remain parallel and are perpendicular to the projection plane. This results in a two-dimensional representation without any foreshortening or perspective distortion.
2. In isometric projection, three equal axes (typically inclined at 120 degrees to each other) are used to represent the three dimensions of an object. These axes are usually labeled as x, y, and z.
3. Align the axes of the object with the isometric axes. For example, if the object's main axes are aligned with the x, y, and z axes, then no rotation is necessary.
4. Scale the object's dimensions along each axis to achieve the desired isometric perspective. In isometric projection, all axes have equal scale, so each dimension should be scaled by the same factor to maintain proportionality.
5. Based on the scaled dimensions, draw the isometric view of the object using the aligned axes. Ensure that all lines are parallel to the isometric axes and maintain the correct proportions.
6. Isometric projection does not show true depth perception, but objects can still appear three-dimensional by using shading or adding details to indicate depth.

EVALUATION: 1. The orthographic views of a block are shown below.  Draw, full size, the block ` in isometric, making point M the lowest.(WAEC)

2. The orthographic views of a block are shown in the figure below.

 Sketch approximately full size, the isometric view of the block, with point K the lowest.(WAEC)

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively