. The railroad and engineering journal . piece touches the cam at that point, then,with such a cam, the purpose is that the reciprocating pieceshall be moved one-sixth of the stroke C D, while the cam turnsone-twelfth of a revolution. Therefore, from the center Ewith a radius E I draw an arc of a circle through i and cuttingthe radial line l. The point of intersection i will then be apoint in the curve. In a similar way draw arcs of circlesthrough 2, 3, 4, and 5. intersecting the radial lines 2, 3, 4 ,and 5. The outline of the cam may then be drawn throughthese points. THE CARDIOID. This curve
. The railroad and engineering journal . piece touches the cam at that point, then,with such a cam, the purpose is that the reciprocating pieceshall be moved one-sixth of the stroke C D, while the cam turnsone-twelfth of a revolution. Therefore, from the center Ewith a radius E I draw an arc of a circle through i and cuttingthe radial line l. The point of intersection i will then be apoint in the curve. In a similar way draw arcs of circlesthrough 2, 3, 4, and 5. intersecting the radial lines 2, 3, 4 ,and 5. The outline of the cam may then be drawn throughthese points. THE CARDIOID. This curve may also be used for the outline of a cam. 324 THE RAILROAD AND [July, 1891. Problem 99. To lay out a cardioid curve. Lei A B, fig. 276, be the generating circle. Subdivide this into,say, 12 parts, and through one end o of a diameter o 6 draw lineso I i, o 2 2, o 3 3, etc., intersecting the points of division ofthe generating circle, and extend the lines beyond the take with a pair of dividers a distance tqual to the diam-. Fig. 276. eter o 6, and from the point of division i in the generatingcircle lay o£f this distance, i i and i i, on each side of points thus laid off will be in the curve. Proceed in asimilar way and lay off from 2, 3, 4, etc., distances 2 2, 2 2,3 3. 3 3. etc., which will give points in the curve through whichit may be drawn. THE CISSOID. Problem 100. To lay out a cissoid any line A B, fig. 277, and CD perpendicular to CD describe a circle and divide it into a number of parts, CONCHOID CURVE. The conchoid is a curve which always approaches a straightline, but never reaches it, however far the curve and straightline may be produced. This curve has been used in drawingthe slightly curved line which forms the outline of columns. The straight line A B, fig. 278, is called \\xe asymptote, CDthe diameter, and P the pole. Problem ioi. To lay out a conchoid curve. The asymptote, A B, pole P and diameter C D, being
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