Counter-driven cycloid drawing machine jumps at multiples of Pi

I’m building a 3D cycloid drawing machine using a Kangaroo counter to drive the rotations. I saw I was getting periodic jumps in the resulting curve, and after investigating have realised it happens every time the counter (with scaling factor) reaches a multiple of Pi (3.14).

As I am performing further functions on the counter before inputting to the evaluate curve parameter I can’t see any mathematical reason why this reset to the “0” parameter position would happen.

Any pointers appreciated, I’ve probably missed something obvious…

3D Cyloid TEST.gh (20.1 KB)

Hi Tony,
That’s an absolutely beautiful shape, and I am super impressed with your definition. I 've not fully understood what the issue is, but I have identified where it is and a way to solve it.

Diagnostics:
To be precise about the problem, the jumps are not quite at multiples of pi, the jumps are between 3.12499 and 3.12500.

The problem is in the middle of your definition, where there are the 2 circles and 2 evaluate curves (highlighted in the image), the points jump by 180 degrees at 3.125. One way to fix the jump you can replace that part of the definition with a couple of Sin and Cos Expression which sill find the location of the coupler points.
Alternatively I think that a compound transformation could probably do it too.

I get the impression that you have worked hard to get this far and that you want to solve the rest of it yourself. If you want a bit more help, please ask… or I can upload a working definition just ask.

Kind regards
Drew