The Wankel engine consists of a gerotor with three
generating lobes on the larger pitch circle. The gerotor
consists of a pair of planer circles in which one of them
encloses the other one. The lobe generating pins create
an inner and outer envelope. The inner envelope is
created by point of contact between the pin and the
generated shape. The external point of contact
develops the outer envelope. The dimensions and
locations of these pins severely effect the volumetric
displacement of the rotary mechanism