Page:Popular Science Monthly Volume 92.djvu/312

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��Popular Science Monthly

��section C so that we can get the correct widths down to the front view. The arcs D and E are swung up to the line F and then dropped down (see dotted lines) until they strike the edge of the sphere on the front view, as indicated by the crosses. Next, run the lines D and E across the front view. Then drop the dotted lines from D and E on the top view down until they cross the lines D and E on the front view. Connect these crosses with a curved line and you have the true front view of the section C.

Developing the Pattern

The development of the pattern for the section is as follows: First, draw the cylinder G, Fig. 2, with its bottom view H. Draw the section C on the cylinder the same size as sec- tion C on the top

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��i Pattern

��Another interesting method of developing the same pattern

��view of Fig. 1. Now, if the rectangle K-L-M-N, Fig. 2, is thought of as repre- senting the front view of a cylinder, or round pipe, it will be seen that the section C is simply a slice of that cylin- der. After this is seen, the problem becomes a very simple one in which we use exactly the same methods of develop- ment as we used in the elbow pat- terns. Second, draw the bottom view //. Divide one-half into eight equal parts. We only use one half because the section only runs half way round the cylinder. Third, draw the base line 0-P, obtaining the correct length by stepping off the eight spaces from the bottom view //. Run the lines from the points on the bottom view upward until they strike the section C. Then run them over until

��they intersect the same numbered line coming up from the base line 0-P. Make a cross at the point of intersection and connect with a curve. Then you have the complete pattern for the section C. Cut out sixteen of these. Bend them to the form of a half circle and solder them to- gether. No allowance is necessary for laps or seams.

A "short cut" method is shown in Fig. 3, in which the top view corresponds to G in Fig. 1. No bottom view is needed because the lower half is used as the bottom view, and the section division lines designate the bottom view points. Lay off the base line S-T by stepping off the distance as numbered. Run the lines upward until they strike section C; then over to the right until they cross the same numbered lines coming up from the base line. Mark the intersection with a cross. Connect these crosses with a curve, and you will have one-half of the pattern. By repeating this operation farther along, the entire pattern may be developed.

A Simple Method of Developing the Pattern

Another interesting method of develop- ing this pattern is shown in Fig. 4. It will be seen that the drawing of the top view and the front view is the same as in Fig. 1. The steps taken are: First, draw the top view U. Second, divide section C into any number of parts, as numbered from 1 to 6. These are swung around to line W; then dropped down to the front view circle; then across to sec- tion C. Third, drop the lines down from section C, top view until they cross the same numbered lines running across sec- tion C, in the bottom view. Mark with crosses and connect with a curved line. This will give the correct front view of section C. Now draw the line X- Y. Get the correct length by stepping off the distances, as indicated by the same num- bers on the circle. Then with the compasses, measure the width of section C, front view, line one, and set off the same width on line one of the pattern. Do the same with the other lines and you will have the pattern for one-half of section C'. After the pattern is developed it is an easy matter to build up the ball, making an almost perfect sphere in the completed ornament.

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