Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . surement. Oneaxis is at 30° and another at 40° to the projectionplane. 4. Find in isometric projection the two parts,separated as in the illustration herewith, of amortise and tenon joint. Use dotted lines torepresent those lines not in view. AXOMETRIC PROJECTION, CONTINUED 73 AXOMETRIC PROJECTION, Continued Section 21. Since scale, with respect to drawings, is the ratio of projectionlength to real length, it will be seen that the axes in axometric projection may bearranged in
Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . surement. Oneaxis is at 30° and another at 40° to the projectionplane. 4. Find in isometric projection the two parts,separated as in the illustration herewith, of amortise and tenon joint. Use dotted lines torepresent those lines not in view. AXOMETRIC PROJECTION, CONTINUED 73 AXOMETRIC PROJECTION, Continued Section 21. Since scale, with respect to drawings, is the ratio of projectionlength to real length, it will be seen that the axes in axometric projection may bearranged in place when scales for any two of them are given, by setting up twolines at inclinations to the that will give those scales, and, having arrangedtheir plans correctly, placing the third axis in proper relation to these. The scaleof the third may then be obtained also. Thus, suppose the scales for A and B are to be f and -^ respectively, the incli-nations of A and B to the may be obtained as in Fig. 74 at (i), where ab,equal to 4 divisions, is represented in plan by ac equal to 3 of the same divisions;. Fig. 74. that is, ac is f full length, and the inclination for this scale of f is the angle , ad, equal to 6 divisions, is represented in plan by ac, equal to 5 divisions,, ae is i full length and the angle for the axis which will have a scale of ,^ willbe the angle dac. Employing the method as shown in Fig. 71, set up at Fig. 74, (ii), the angledae at a and the angle bac at /3, and proceed to find axes A and B with their HH. The third axes, C, will be found and its obtained as in Fig. 71. Byswinging the plan of that portion of it above the into AT, the plan lengthRS and the real length TS are obtained, which will give the scale for the third axis RS C as TS From what was seen previously (see Note in Section 18), the contained anglebetween the axes of projection being 90°, the inclinations of them to the projectionplane must be small, so
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