“…This paper focuses on the synthesis of spatial cycloidal gears based on Disteli's work, which was published at the turn of the 20th century [5][6]. In particular, the properties of the cylindroid or Plücker's conoid for the relative motion between a pair of skew gears are analyzed in order to extend Reuleaux's principle from the planar and spherical cases, as reported in [7][8][9], to the spatial case with the aim of synthesizing a pair of conjugate cycloidal teeth.…”