The truncated cylinder is a prism with an infinite

number of sides. The number of sides must be limited

when developing a cylinder. However, the greater the

number of sides, the more accurate the development.

The following steps for the development of a truncated

cylinder are shown in figure 14-43.

1. To develop one-half of a two-piece elbow, first

draw a front and bottom view of that piece in

orthographic projection (view A). Since the

elbow does not require an end piece, you do not

need to draw an auxiliary view showing the true

shape of the ellipse formed by the cutting plane

at the top of the cylinder.

2. Divide half the circumference of the circle into

several equal parts. The parts should be small

enough so a straight line drawn between

division points will approximate the length of

the arc. Project lines from these points to the

front view (view B). The resulting parallel lines

on the front view are called elements.

1. Draw a front view and a bottom view of the

prism in orthographic projection (view A).

2. Draw an auxiliary view (view B) since the true

shape of the slanting plane and the length of the

lines of its edges are not shown in these views.

Note that drawing the entire prism in the

auxiliary view is not necessary. Only the

dimensions of the plane surface are required.

3. Project the lines of the front view horizontally

as the first step in constructing the development

(view C).

4. Number the points of intersection of planes on

the bottom view. Mark off line segments of the

same length on the base line of the development.

5. Erect vertical lines from these numbered points

to intersect the lines projected from the front

view of the prism (view D). These intersections

mark the comers of the prism.

6. Connect the intersection points with straight

lines.

7. Draw the bottom of the prism attached to one of

the sides at the base line. Draw the slanting

plane at the top of the prism (view E).

8. Check all edge measurements to be joined, as

shown in the pictorial drawing (view F), to be

sure they will coincide exactly.

14-27