Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . t 40° to the same plane. First find the three axes of projection. As the axis of the sohd has to be in the40° direction, the base must be placed in the plane of the two others. The base,not being right angular, must be placed in a rectangle as at (ii). As AB at (ii) AXOMETRIC PROJFXTIOX, CONTIXUED 75 contains an edge of the base, the Hne AB must be fitted on to the 25 axis of pro-jection. Therefore, place it in rabattement at /l2i^2and draw the complete figurecontained in the r
Descriptive geometry for students in engineering science and architecture; a carefully graded course of instruction . t 40° to the same plane. First find the three axes of projection. As the axis of the sohd has to be in the40° direction, the base must be placed in the plane of the two others. The base,not being right angular, must be placed in a rectangle as at (ii). As AB at (ii) AXOMETRIC PROJFXTIOX, CONTIXUED 75 contains an edge of the base, the Hne AB must be fitted on to the 25 axis of pro-jection. Therefore, place it in rabattement at /l2i^2and draw the complete figurecontained in the rectangle BoAoCo, and proceed to carry it over to its positionin plan. Having completed the base in plan, find its centre C, and from thatcentre draw a line in the direction of the 40° axis. Find, by the proper method,the projection length of the axis at coa^ or c-zb-y, according to its length, and thenmark this off on the axis line of the pyramid starting from c, thus giving the apexat (/ or h. Join the apex to the corners of the base and fmish as usual with dottedlines for some edges as the case may Fig. 76. If a circular hole has to be represented, in a block, for instance, in axomctricprojection, points should be obtained in the circumference by using diagonals andparallels to the sides of a square made to contain the circle, the sides of the squarebeing made to follow axis directions in the projection. EXERCISK XXXI 1. The plans of the three axes of projection enclose angles of iio^. 120° and i.^o. Findthe inclinations of the three axes to the projection plane. 2. The scales of two of the axes for a projection are J^ and j^. Find the projection of the axesand represent the scale of the third axis. 3. Pind by axomctric projection the plan of a regular hexagonal pyramid, when the axisof the pyramid, 3 long, is at 30° to the projection plane, and one of the edges of the base, ilong, is at 45° to the projection plane. CHAPTER XI SECTIONS OF SIMPLE SOLIDS Section
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