Isometric Projections

Isometric Drawing

Isometric Drawing is a type of pictorial projection in which all three dimensions of an object are shown in one view and if required, Their actual sizes can be measured directly from it.

3D drawing can be drawn in numerous ways as shown below, All these drawings may be called 3 Dimensional drawings, photographic or pictorial drawings. Here no specific relation among H, L & D axes is maintained.

Typical Condition

In this 3D drawing of an object, In which all three dimensions axes are maintained at equal inclinations with each other. ( 120º )

Now observe below-given drawings. One can note specific inclination among H, L & D axes. Iso means the same, similar or equal.

Here one can find dual inclination among H, L & D axes. Each is 120 inclined with the other two. Hence it is called isometric drawing.

Some important terms

Isometric axes, lines, and planes

The three lines AL, AD, and AH, meeting at point A and making 120^º angle with each other termed Isometric axes.

The lines parallel to these axes are called isometric lines.

The planes representing the faces of the cue as well as other planes parallel to these planes are called isometric planes.

Isometric scale

When one holds the object in such a way that all three dimensions are visible then in the process all dimensions become proportionally inclined to observe's eyesight and hence appear apparent in lengths.

This reduction is 0.815 or 9/11 (approx.) it forms a reducing scale which is used to draw isometric drawing and is called isometric scale.

In practice, while drawing isometric projection, it is necessary to convert true lengths into isometric lengths for measuring and marking the sizes. this is conveniently done by constructing an isometric scale.

Types of isometric drawings

Construction of Isom.scale

From point A, with line AB draw 30 and 45 inclined lines AC & AD resp on AD. mark divisions of true length and from each division of true length and from each division-point draw vertical lines up to AC line.

The divisions thus obtained on AC give length on isometric scale.

Isometric of plane figures

As these all are 2-d figures we require only two isometric axes.

If the figure is a front view, h & l axes are required.

If the figure is a top view, D & L axes are required.

Shapes containing inclined lines should be enclosed in a rectangle as shown.then first draw Isom. of that rectangle and then inscribe that shape as it is.



 

Isometric of plane figures

As these all are 2-D figures we require only two isometric axes.

If the figure is a front view, H&L axes are required.

If the figure is a top view, D&L axes are required.

For isometric of circle/semicircle use rhombus method. construct it of side equal to the diameter of a circle always. ( ref. previous two pages.)

Study illustrations

1 ] Draw the isometric view of a circle if it a Tv or Fv.

1. First, enclose it in a square it's isometric is a rhombus with D&L axes for top view.


2. Then use H&L axes for isometric when it is front view.


3. For construction use the rhombus method shown here, study it.

2 ] Draw the isometric view of the figure shown with dimensions, considering it first as F.V. and then T.V.



answer



3 ] Isomeric view of pentagonal prism lying on hp and hexagonal prism standing on hp

 



 

4 ] Cylinder standing on HP and Lying on HP



 

5 ] Half cylinder standing on HP and Lying on HP



 

6 ] Isometric view of the pentagonal pyramid

 



7 ] Isometric view of a frustum of a square pyramid standing on HP, On it's larger base.

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