Question

•Research/investigate existing teaching models, procedures, and methods, etc. that used to demonstrate the concept of third angle projection to students/learners

. •Point out the limitation of the existing models, procedures or methods used. Alternatively critique the existing models and consequently list their shortcomings.

•Finally state how you hope to rectify some of the limitations you identified in the existing models above.

•Draw conclusions from your work

Answer 1

Third angle projection is a projection technieque in engineering drawing in which the vertical plane (VP) is between the object and the observer. Because the object of interest is located in 3rd quadrant and horizontal plane (HP) opens up in the clockwise direction in third angle projection, the top view (plan) is at the top and front view (elevation) is at the bottom. In understanding this, the two key skills required are visualization and imagination power.

Various models that are used to demonstrate 3rd angle projection are -

1. videos or animations of solid models

2. actual physical models showing the VP, HP and an object - These would be generally in the form of a transparent box and a solid oject kept inside it

3. the models could be also in the form of simple illustrations - demonstrated either on board or sheet

Going by the experience, it can be said that the first two are easier to understand as compared to plain illustrations. Important to note here is that the larger the extent of visualization of a particular model or method, the easier it is to understand the concept (in this case that of third angle projection) using that model or method.

1. Videos/animations - The best way to demonstrate the positions of reference planes and the object, how the projections of the object are actually projected onto HP and VP and how these reference planes are 'opened'. This makes it easy to understand why the plan is at the top and elevation at bottom when using third angle projection. Another big advantage of using videos and animations is that any object of complex size, shape and features can be used. As it is in virtual form, so solid 3-D model of any object can be made using CAD tools and used in the animation to show how various projections are taken.

A potential disadvantage of using this method is that it kind of oversimplifies the visualization. While this itself may not be such a bad thing, it may increase one's dependence on visual aides, and does not encourage learners to use their imagination power. It is to be expected that the models will not be readily available in many situations and one has to use only imagination and visualization skill to draw the various views given only the isometric view.

It is time consuming to create the animation.

2. Physical models - Most of the advantages are same as those of animations. An additional advantage is that it is physically possible for the learner to visualize how the various projection details get projected on various views and how their relative positions get fixed.

Main disadvantages are - 1. The physical model is bulky 2. Creating model for a complex object is difficult and time consuming. Like for animations, the oversimplification and over-dependence on external aides are also prominent demerits of physical models.

3. Board (or sheet) illustrations - Are easy to make but diffiult to understand. They require maximum use of one's imagination and visualization skills. They are not required to be stored and can be quickly reproduced when needed.

Rectification of limitations -

1. Use animations and virtual models only in case of complex shapes. For simpler shapes encourage students and learners to rely on their own imagination power to draw the drawings.

2. Use the physical and virtual models for simple shapes only for the weak learners.

Main conclusions from above review of methods, models, procedures to demonstrate third angle projection concept are as below:

1. Models whether solid or virtual make it easier for the learners to visualize and understand the various projections. So they should be judiciously used.

2. For average learners, for simple objects, it is preferred to encourage using their imagination and visualization skills. Use of virtual models should be limited for complex objects.

3. Use the models even for simple objects only for the benefit of learners who are weak in their imagination powerr.

4. In the end an engineer is expected to make drawings (whether on paper, the old fashioned way or using CAD tool). So it is required that s/he improves her/his visualization skill and imagination power to such a level that s/he is able to create the drawings without the help of other physical or virtual models. Thus dependency on models should be discouraged as it prevents or hinders growth of one's imagination skills and visualization power.