Isometric sketching

If relief is via a bursting disc, the flow capacity of the relief system will normally depend on friction and choke points in the relief system. The only exception is where friction is not important (LE/D less than about 40), where equation (A6.4) can be used.) Where friction is significant, an isometric sketch of the route of the relief system will be required to determine the capacity. If the system is to be of constant diameter, then using the sketch, the total equivalent length, LE, of the route, including the frictional resistance of bends and fittings can be determined111. This can also be expressed in terms of total frictional velocity head loss, K ... 

When it is difficult to visualize an object using only its orthognqihic views, an isometric sketch is also drawn. The isometric drawk tissws the three dimensions of an object in a singie view. The isometric drawii are sometimes referred to as technical illustiadons and are used to show... 

Pictorial representation is divided into three groups. Two of these groups are demonstrated in this chapter. The three types of pictorial sketches are axonometric (meaning to measure along the axis), oblique, and perspective. Of the axonometric family of drawings, isometric sketching is the one used here (see Figure 5-6). 

Isometric sketching is a method of representing three-dimensional objects with three axes—X, y, and z. The X- and y-axes are always drawn 120 apart. 

FIGURE 5-22 An engineering sketch in perspective. Compare this sketch with the isometric sketch in Figure 4-11. 

Fig. 14. Plan anange-ment and isometric sketches of a loading bay to resist wind on the comer of a building at the 400 ft level...

FIGURE 10.3 Spray drying setup (a) sketch of the dryer (dimensions are in mm) and (b) isometric view of the dryer. 

A presentation sketch is very detailed and made to look realistic, usually as a three-dimensional pictorial view such as an isometric or perspective drawing. 

Sketching an Isometric Cube An easy way to learn to sketch in isometric is to learn to sketch a cube in isometric. Remember, a cube is a three-dimensional shape that has squares on all its faces. Figure 5-8 illustrates the steps you should take to sketch the three-unit cube (3 X 3 X 3). In Chapter 4, you learned about the geometric term parallel. Now is the time to put this term to work. When you sketch, make sure all opposite edges are parallel. 

The sketched isometric cube is formed by three isometric square planes. 

FIGURE 5-7 All isometric shapes begin with three axis lines, which are often referred to as the x, y, and z axes separated by 120°. Notice the base of the object is sketched at 30 to the left and to the right along the horizontal. 

Sketching an Isometric Rectangular Solid Sketching a rectangular solid... 

Step Two Sketch the three axis of an isometric at the angles shown above... 

Step Six Complete the isometric cube by sketching the top, back edges parallel to edges you sketched in step five... 

Step One Sketch the isometric base as shown above and mark off the width along the X-axis, the depth along the Y-axis, and the height along the Z-axis... 

Sketching Isometric Circles, Arcs, and Cylinder Circles and arcs look like ellipses when they are sketched in isometric. Simply put, an ellipse is a flattened circle that is developed with two equal large arcs and two equal smaller arcs. The easiest way to begin an isometric circle or arc is to begin with an isometric square. The circle or arc will appear shghtly different in each view (front, top, and side) of the isometric shape. Figure 5-13 illustrates the steps to sketch each isometric circle. An arc, as you may recall from Chapter 4, is a segment or part of a circle. So, if you learn to sketch isometric circles, you also learn to sketch isometric arcs. 

Sketching isometric cylinders is the natural next step once you have learned to sketch isometric circles. Cylinders are sohds with the ends shaped like circles. When you sketch the two opposite isometric circles, all you wiU need to do is connect the circles with two lines (edges of the cylinder) tangent to the circles (remember, tangent line was defined in Chapter 4). Examine Figure 5-14 to see the steps you need to take to sketch isometric cylinders from the front, side, and top views. 

Sketching Isometric Holes Isometric holes can be thought of as negative cylinders. You can sketch an isometric hole in the same way you sketch an isometric cylinder. Instead of the cylinder being of solid material, it forms empty space. Figure 5-15 demonstrates how to sketch an isometric hole. If the length (also called depth) of the hole is less than the diameter of the circle, then you will be able to see part of the other end of the hole. However, if the depth is longer (deeper) than the diameter, you wUl not be able to see the end of the hole. 

Sketching Complex Objects in Isometric So far you have learned to sketch simple isometric shapes such as rectangular solids, circles, arcs, and cylinders. You also learned to sketch inclined planes, or planes that are not perpendicular to the six normal planes (front, right side, top, left side, back, and bottom). Now you will take what you have learned and combine shapes to create recognizable objects. 

Sketching one-point perspective circles, arcs, and holes is similar to sketching in isometric. Begin by developing a perspective square. Unlike isometric squares, for which all sides are equal, the height of the square is... 

Using correct freehand technical sketching techniques, practice sketching isometric cubes. See Figure 5-29 for a practice example. 

Directions 1. Using a practice sheet from your teacher, sketch isometric cubes by re-drawing the cube shown in this example at the pre-marked locations. 

FIGURE 5-30 Sketching practice Isometric rectangular solid. 

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