Here is another iteration of an ellipsograph, this one has a larger range of major/minor axes ratios, compared to the first. ( ~ 1.41 - 1.77 )

To facilitate the larger ratios, smaller screws were needed (6-32 instead of 10-32). This in turn wouldn't allow the nuts to be hand-tightened, so I added a piece and changed the arm to allow for step-wise changes of the ratios. Different sides of the arm have different cutouts to allow for the entire range to (feasibly) be used. The pen holder still requires 10-32 screws and 2 nuts.

You will need a 6-32 tap, a 10-32 tap, two 6-32 x 1" screws (1" or so), one 6-32 x 0.5" screw, two 10-32 nuts, and 2 10-32 screws, if you want to assemble this the way I did. The washer (bushing) is difficult to get to snap over the saw-toothed region, but once it's in there, it moves much easier. The 0.5" screw is used to collapse the arms on the bushing to get it to not move while drawing.