A Textbook on Mechanical Engineering Volume 4

A Textbook on Mechanical Engineering Volume 4

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1897 edition. Excerpt: ...article (representing the practical feature) would be all that is necessary for the student to understand before proceeding with the work on the drawing board. Since it has been shown that several views are required, another important practical feature must necessarily be explained. This relates to the connection usually established between the different views of a drawing and the lines that are drawn in a certain manner between corresponding points in each view. These lines are usually not represented in a finished drawing, since they are in the nature of construction lines. They are essential, however, to the work of making the drawing, and it is very important that the student should thoroughly understand the principles by which they are employed. These lines are called projectors and may be defined as the trace of a line of sight, or the representation of the foot of a line of sight moving in a certain direction. Projectors are used in two ways, which are distinguished from each other for the present by the terms primary and secondary. 29. Primary Projectors.--This use of projectors is illustrated in Fig. 4, which shows the drawing bent up at a right angle along the base line m-n. The point A is projected to H P by the vertical line of sight C B; it is also projected to V P by the horizontal line of sight D E; B and E are dots at the foot of each line of sight. It is assumed that the first position of the observer is at C; he then moves, in the direction of the arrow, along the dotted line to D. If, in so doing, he continues to sight through the point A, it is apparent that a line will be traced from B to fon H P and from F to E on V P. The upright portion of the drawing V P is now imagined to be bent backwards until laid flat on the drawing...
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Product details

  • Paperback | 110 pages
  • 189 x 246 x 6mm | 213g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236627156
  • 9781236627155