Tham khảo tài liệu 'mechanical movement episode 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 98 Mechanical Movements. 1 Mechanical Movements 403. Cyclograph for describing circular arcs in drawings where the center is inaccessible. This is composed of three straight rules. The chord and versed sine being laid down draw straight sloping lines from ends of former to top of latter and to these lines lay two of the rules crossing at the apex. Fasten these rules together and another rule across them to serve as a brace and insert a pin or point at each end at chord to guide the apparatus which on being moved against these points will describe the arc by means of pencil in the angle of the cressing edges of the sloping rules. 404. Another cyclograph. The elastic arched bar is made half the depth at the ends that it is at the middle and is formed so that its outer edge coincides with a true circular arc when bent to its greatest extent. Three points in the required arc being given the bar is bent to them by means of the screw each end being confined to the straight bar by means of a small roller. 405. Mechanical means of describing hyperbolas their feci and vertices being given. Suppose the curves two opposite hyperbolas the points in vertical dotted center line their foci. One end oi rule turns on one focus as a center through which one edge ranges. One end of thread being looped on pin inserted at the other focus and other cross-bar one is fixed and the other adjustable and held by end held to other end of rule with just enough slack between to permit height to reach vortex when coincides with center line. A pencil held in bight and kept close to rule while latter is moved from center line describes one-half of parabola the rule is then reversed for the other half. 406. Mechanical means of describing parabolas the base altitude focus and directrix being given. Lay straight edge with near side coinciding with directrix and square with stock against the same so that the blade is parallel with the axis and proceed with pencil in bight of thread as in the
