The essentials of descriptive geometry . ndicular to this line; and the inlet is acircle whose diameter is 48 and whose plane inclines 30 degrees to thisline. Draw a plan and elevation of this hood and make a pattern for it. 273. Make a pattern for a convolute conveyor flight whose diameter is12, pitch 8, diameter of shaft 3. 274. Two shafts, one vertical and one inclined 45 degrees in a verticalplane, are 2 in diameter, and their center lines are 7 apart. Draw the plan,elevation, and end view of two hyperboloids of revolution which will operateon these shafts in the ratio of 4 to 3. CHAPTER X
The essentials of descriptive geometry . ndicular to this line; and the inlet is acircle whose diameter is 48 and whose plane inclines 30 degrees to thisline. Draw a plan and elevation of this hood and make a pattern for it. 273. Make a pattern for a convolute conveyor flight whose diameter is12, pitch 8, diameter of shaft 3. 274. Two shafts, one vertical and one inclined 45 degrees in a verticalplane, are 2 in diameter, and their center lines are 7 apart. Draw the plan,elevation, and end view of two hyperboloids of revolution which will operateon these shafts in the ratio of 4 to 3. CHAPTER XVIII MODEL MAKING 143. One of the most interesting and practical means ofstud3dng the development of surfaces and the laying out ofpatterns for them consists in the construction of actual scalemodels. This not only affords practice in the use of drawingsand gives experience in constructing the object represented inthe drawing, but it is also an excellent means of showing howcurves of intersection appear when laid on a pattern as well as. Fig. 143. — A paper model of a blast furnace piping problem constructed to scalefrom ordinary detail paper and mounted on a wooden base. when they are an actual part of the object on which they such model making must of course be done to scale yetthe experience acquired serves to illustrate many of the practicalconsiderations which must be kept in mind when laying outsheet metal work. 144. Practical Hints. In making paper models such as theone shown in Fig. 143 a good grade of detail paper will give satis-factory results. After the developments of the several surfaceshave been accurately made they may be cut out — leaving anallowance along the proper edges of the pattern for lap — andglued together, thus forming the actual surface. 179 i8o ESSENTIALS OF DESCRIPTIVE GEOMETRY
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