Finally got my rotatory working this weekend.
The cup is an insulated cup from Starbucks. My daughter is into dragonflys and her nickname is JAX.
I was able to make a stabilizer end out of some firm foam I get from work. It is interesting that math trumps common sense! The first one has an outer diameter of the larger end. You would think that this would make the angle of the cup straight but no! You have to add enough extra so that the cup is actually straight. Geometry finally paying off!
You are the only other person I have seen to use Adapter rings besides me. Due to inconsistencies with some cup/bottle suppliers, I have around 20 Adapters.
btw… The problem with making the ring larger is that is then has different rotation geometry/Math and it can cause slipping or the cup to get crooked. I make adapter rings the same size as the largest diamager of the cup and then elevate one end of the rotatry to try and make the printing area as level as possible.
@Kelly_Burns Thanks for the info. I am thinking about making an adjustable stand for the ring side and make it an idler.