{"id":3217,"date":"2023-10-04T13:05:06","date_gmt":"2023-10-04T13:05:06","guid":{"rendered":"http:\/\/localhost\/ecole9ja\/?p=3217"},"modified":"2023-10-04T13:06:38","modified_gmt":"2023-10-04T13:06:38","slug":"week-10-ss2-second-term-technical-drawing-td-notes","status":"publish","type":"post","link":"https:\/\/ecolebooks.com\/nigeria\/posts\/week-10-ss2-second-term-technical-drawing-td-notes\/","title":{"rendered":"Week 10 – SS2 Second Term Technical Drawing TD Notes"},"content":{"rendered":"

\u00a0WEEK TEN:
\n<\/strong>Topic: <\/strong> Lines in space
\n\t\t\t<\/strong>\"\"\/Content:
\n\t\t\t<\/strong>(i) Meaning of traces and the true length of a line.
\n(ii) Methods of determining the true length and inclination of lines in space.
\n.Meaning of traces and the true length of a line.
\n<\/strong>\"\"\/
\n\t\t\tTrace:<\/em><\/strong> A line inclined to a normal principal plane of projection would if produced penetrates this plane. The point where this happens is called a trace.<\/em><\/strong> The true or actual<\/em><\/strong>
\n\t\t\tlength<\/em><\/strong> is the length of this inclined line obtained when it is projected on an auxiliary plane parallel to it. <\/p>\n

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\n\t\t\tMethods of determining the true length and inclination of a line in space.<\/strong><\/p>\n

\u00a01. Auxiliary method:<\/strong> This method is the same as that used in auxiliary projection of inclined surfaces of objects treated earlier on.
\n\"\"\/Example 1:<\/strong> Determine the true length and angle of inclination of a line AB<\/strong> inclined in space as shown in figure below.<\/p>\n

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\n\u00a0Method:
\n<\/strong>(i) Draw the X-Y line.
\n(ii) Draw the plan AB and the elevation A1<\/sup>B1<\/sup> of the line.
\n(iii) Draw the projection lines AA1<\/sup> and BB1<\/sup>.
\n(iv) To obtain the true length of the normal plan AB, project lines at right angle from the ends A1<\/sup> and B1<\/sup> of the normal elevation and using line X-Y as the reference line, transfer the distances aA and bB of the normal plan and mark them off respectively to locate points V on the perpendicular line from A1<\/sup> and W on the perpendicular line from B1<\/sup>. Line VW is the true length of the plan and it is inclined to the vertical plane VP at an angle \u0444<\/strong>
\n\t\t(v) To obtain the true length of the normal elevation A1<\/sup>B1<\/sup>, project lines at right angle from the ends A and B of the normal plan and using line X-Y as the reference line, transfer the distances aA1<\/sup> and bB1<\/sup> of the normal elevation and mark them off respectively to locate points S on the perpendicular line from A and T on the perpendicular line from B. Line ST is the true length of the elevation and it is inclined to the horizontal plane HP at an angle \u04e8<\/strong>.<\/p>\n

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\n\u00a02. Rebatment or revolution method:<\/strong>
\n\t\t\t\"\"\/Example 1:<\/strong> Consider an oblique line AB<\/strong> which is inclined at an angle of 300<\/sup> to the vertical plane and 450<\/sup> to the horizontal plane.<\/p>\n

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\n\u00a0Method:
\n<\/strong>(i) Draw the usual X-Y line.
\n(ii) Draw the plan and elevation of line AB.
\n(iii) Draw a line to connect the elevation and plan i.e. line bB.<\/p>\n

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\n\t\t\t\tTo draw the true length TL of the elevation Aa and its true angle of inclination to the horizontal plane HP.
\n<\/strong><\/em>(iv) With a pair of compasses pin at point A and radius AB, swing an arc to meet the X-Y line at point <\/p>\n

\t\t\tm<\/strong> and then project a vertical line upwards from this point.
\n(v) Take the distance ab and mark it off on this line to get point b1<\/sup>.
\n(vi) Draw a horizontal line to connect b to b1<\/sup>. Line Ab1<\/sup> is the true length TL of the elevation and its
\n angle of inclination to the horizontal plane HP is measured.<\/p>\n

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\n\t\t\t\tTo draw the true length TL of the plan AB and its true angle of inclination to the vertical plane VP.
\n<\/strong><\/em>(vii) With A as centre and radius Ab, swing an arc to meet the X-Y line at point n<\/strong> and then project a
\n vertical line downwards from this point.
\n\t\t\t<\/em>(viii)Take the distance aB and mark it off on this line from point m to get point B1<\/sup>.
\n(ix) Draw a horizontal line to connect B to B1<\/sup>. Line AB1<\/sup> is the true length of the plan and its true angle
\n of inclination to the vertical plane VP is measured. <\/p>\n

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\n\u00a0Determination of the true shape of a triangular lamina<\/strong>
\n\t\t\"\"\/
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\n\u00a0Method
\n<\/strong><\/p>\n

    \n
  1. Draw the given elevation and plan of the lamina with the ground line X-Y drawn between them.\n<\/li>\n
  2. Determine point D on the plan by drawing a horizontal line parallel to the ground line X-Y from point A1 to D1<\/sup> then draw a line vertically down to point D.\n<\/li>\n
  3. Project a line from point A through D to a convenient point. Similarly, project lines from points B and C parallel to AD produced.\n<\/li>\n
  4. Draw a ground line X1-Y1 perpendicular to the projected lines from the plan.\n<\/li>\n
  5. Obtain distances from X-Y line to points A1,B1 and C1 on the elevation and transfer them, now from X1-Y1 respectively to obtain the auxiliary elevation line B2, A2D2 and C2.\n<\/li>\n
  6. Similarly, obtain distances from the X1-Y1 to points A,B,C and D on the plan and transfer them to obtain the auxiliary plan A3, B3, C3 now using X2-Y2 as the ground line..\n<\/li>\n<\/ol>\n

    \u00a0Evaluation question
    \n<\/strong>The figure shown below is the elevation and plan of a triangular lamina in first angle projection.<\/p>\n

      \n
    1. Draw the true<\/strong> shape of the lamina\n<\/li>\n
    2. \n
      Measure and state the\n<\/div>\n
        \n
      1. Angle of inclination to the horizontal plane\n<\/li>\n
      2. True length of AC.\n<\/li>\n<\/ol>\n<\/li>\n
      3. \n
        Indicate on the drawing, the;\n<\/div>\n
          \n
        1. auxiliary elevation;\n<\/li>\n
        2. auxiliary plan.\n<\/li>\n<\/ol>\n<\/li>\n<\/ol>\n

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          \n\u00a0\"\"\/Determination of the true shape of a triangular lamina having one of its faces resting on the horizontal line.<\/strong><\/p>\n

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          \n\u00a0Method
          \n<\/strong><\/p>\n

            \n
          1. Draw the elevation and plan of the lamina with the face AB lying on the horizontal plane.\n<\/li>\n
          2. Draw B1A1 produced to a convenient point D.\n<\/li>\n
          3. Erect a perpendicular DE at point D.\n<\/li>\n
          4. Draw a line from C1T parallel to B1D and mark off the vertical height HT on this line.\n<\/li>\n
          5. With a compass pin at point H and radius HT, swing an arc to meet DE at G.\n<\/li>\n
          6. Draw a line from G parallel to HC1 and this intersect the altitude PC1 produced at point K.\n<\/li>\n
          7. Join KA1 and KB1\n<\/li>\n<\/ol>\n

            \u00a0Evaluation Questions
            \n<\/strong>1. Determine the true length and angle of inclination of the elevation a1<\/sup>b1<\/sup> and plan a2<\/sup>b2 <\/sup>inclined in space as shown in figure below using the auxiliary method.
            \n\"\"\/<\/p>\n

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            \n\u00a0\"\"\/2. The figure below shows the diagonal of a cube inclined at 450<\/sup> to both the horizontal and vertical planes. Use rebatment method to obtain the true length and inclination of the diagonal.<\/p>\n

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            \n\u00a0Reading assignment<\/strong>
            \n\t\t\t
            \n\t\t\t\t<\/strong>Technical drawing for school certificate and GCE by J.N. Green pages 123-130.
            \n\t\t\t\t<\/strong>Engineering drawing 1 by M.A.Parker and F.Pickup pages 138 \u2013 148.
            \nEngineering drawing 2 by M.A.Parker and F.Pickup pages 204 \u2013 230.<\/p>\n

            \u00a0Weekend Assignment
            \n<\/strong>Objective
            \n<\/strong>1. Which of the following is not a method used to determine the true length of a straight line?
            \n A. 4-center method. B. auxiliary method. C. revolution method. D. rebatment method.
            \n\"\"\/2. The point at which a line in space, if produced, penetrates a plane is called? A. seam. B. joint line.
            \n C. trace. D. datum.<\/p>\n

            \t\t\tUse the figure below to answer questions <\/em>3-5<\/strong><\/p>\n

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            \n\u00a03. The point N<\/strong> on the diagram above is called? A. seam. B. vanishing point. C. focal point.
            \n D. horizontal trace.
            \n4. The point M<\/strong> on the diagram above is called? A. vanishing point. B. seam. C. horizontal trace.
            \n D. vertical trace.
            \n\"\"\/5. The true length of the oblique line ST <\/strong>in the diagram below is A. SS4<\/sub> B. S2<\/sub>T C. S1<\/sub>T. D. SS3 <\/sub><\/p>\n

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            \n\u00a0Theory
            \n<\/strong>1. The elevation of a line AB is of length 60mm and its plan is 45mm. If the elevation is inclined at an<\/p>\n

            \u00a0\"\"\/<\/p>\n

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            \n\u00a0 angle of 450<\/sup> to the X-Y line. Draw the true length of the plan and elevation and their true inclinations.
            \n2. The figure above shows the plan and elevation of a straight line. The line is inclined to both the
            \n horizontal and vertical planes.
            \n Determine:
            \n (a) the true length of the line.
            \n (b) the true angle of inclination to both planes <\/p>\n

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            \n\t\t<\/strong>\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":"

            \u00a0WEEK TEN: Topic: Lines in space Content: (i) Meaning of traces and the true length…<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1,256],"tags":[],"class_list":["post-3217","post","type-post","status-publish","format-standard","hentry","category-posts","category-second-term-ss2-technical-drawing"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/3217","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/comments?post=3217"}],"version-history":[{"count":1,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/3217\/revisions"}],"predecessor-version":[{"id":3218,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/posts\/3217\/revisions\/3218"}],"wp:attachment":[{"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/media?parent=3217"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/categories?post=3217"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ecolebooks.com\/nigeria\/wp-json\/wp\/v2\/tags?post=3217"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}