A further Wankel design by Burtis in 1993 and 1994
shows a stator with a concentrically located outer rotor
mechanism and an eccentrically located inner rotor. The
inner rotor acts similar to the rotor of a conventional
Wankel rotor and the outer rotor is similar to the outer
housing of the Wankel engine [54]. Another variation of
the Wankel, with a dual apex seal design, was later
developed