EPICYCLOID

in geometry, a curve generated by a point on the circumference of a circle which rolls on the convex side of another fixed curve. The curve generated by rolling on the concave side is called a ‘hypocycloid.’ If the point is not on the circumference, the generated curves are called ‘trochoids. ’” EPICYCLOI’DAL WHEEL, a wheel or ring fixed to a framework, toothed on its inner side, and having in gear with it another toothed wheel of half 201 EPIDAURUS the diameter of the first, fitted so as to revolve about the centre of the latter. It is used for converting circular into alternate motion, or alternate into circular. While the revolution of the smaller wheel is taking place, any point whatever on its circumference will describe a straight line, or will pa and repa through a diameter of the circle, once during each revolution. In practice, a piston-rod or other reciprocating part may be attached to any point on the circumference of the smaller wheel.