A variation of the previous design incorporated round
rotors and stators but the rotor was eccentrically located
with respect to the stator [9,10,11]. Vanes protrude in
the radial direction. The eccentric location of the rotor in
the stator results in a varying volume between adjacent
vanes. The only difference in these three embodiments
is in the vane design. One of the designs by Goyette in
1909 incorporates two individual spring-loaded vanes.