Sinossi
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. 1908 Excerpt: ...(b) Draw a part sectional plan, the part above the horizontal centre lino is to be a horizontal section of the valve and seating through EF, and the part below a plan of the cover. The outer casing is again to be omitted. Scale J full size. Neither dotted lines nor dimensions need be shown. N.B.--1'ake the vertical centre line in the direction of the longer dimension of your drawing paper. Stage 1, 1907. It is arranged for hemp or Fig. 355a. 1 This drawing example was given in the B. of E. Exam. asbestos packing.-Iu the 1907 C. G. Exam, in Mechanical Engineering pattern-makers were asked to make a pattern of this valve. 153. Thick Cylinder Castings.--When a casting is cooling from its molten condition the heat passes out in the most direct way, that is, in a direction normal to the surface, as shown in the sections of solid and hollow columns, A and B, Fig. 357, and the crystals of the metal (a group of which is shown in Fig. 356) arrange themselves in that direction,1 so that when two cooling surfaces are at right angles to each other, as at C, Fig. 357, and the passage of heat is equally rapid in both directions, solidification occurs in such a way that confused crystallization results, and a line XY of weakness2 is produced bisecting the angle, whilst in A and B the lines of crystallization all radiate from the centre, and no interference occurs. The section A (Fig. 358) is a variation of C (Fig. 357), and B is a representative case where sharp angles give lines of weakness, C showing how the use of fillets and rounding the corners results in a satisfactory casting. The first very large hydraulic presses were made to raise the gigantic tubes of the THICK CYLINDER CASTINGS. Britannia and Conway tubular bridges, the form of the bottom ends of the presses b...
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