You have to let alpha vary from -60 to 60 degrees. R is in inches from the center of the rotor. You have to plot it on polar coordinates.

I should send you an excel file outlining how it must be plotted.

Unfortunately, the shape does not match the curve that would fit the housing. I once thought as you do until I measured.

I will get you an equation for the dish too.

So...I've been looking over all the things I never had time to finish when I was in school. Looks like I have a lot to get back to work on. Among which I have a parametric equation I think everyone would be glad to have:

x=e*cos*al+R*cos(al/3)+a*cos(al/3+d)
y=e*cos*al+R*sin(al/3)+a*sin(al/3+d)
R=105 mm
e=15 mm
a=3 mm (I'm not 100% on this one)
d=26.2

Change al = t in inventor and plot from 0-1080 (degrees). That will give you the rotor housing; from which you can develop a rotor.

Now to scour for the internal dimensions of the rotor...