...
Pertinent measurements are the turntable pivot relative to the mechanism as it will determine the translation and rotation transforms necessary on the fundamental linkage locus. For the purposes of this analysis we are not going to move the rocker pivot though it is technically also a variable. The same goes for the crank arm as well as the gearing, these are all variable but not without cumbersome modification, so we are limiting our dependent variables to just coupler length, rocker length, and pen holder length and angle. The pen holder is what defines the coupler curve in this device and the trace of point P is the roulette of interest for this analysis.
Figure 5. Annotated Machine with Link Labels and Dimensions
Four-Bar
This simple mechanism has the following attributes, some of which are functionally fixed while others take on a range. This allows different designs to be traced by the machine. The dimensions shown are approximate to within 1/8".
...