Helical Rectangular Coil with taper and constant pitch.
I thought this was kind of an interesting topic since it had been revived lately, having originally done the "spiral" intersection (curve trajectory) with a rectangular section for a toroidial winding back in 2000 I think it was. Actually, I had to think on it a bit, but I believe as the model shows it's 100% able to be made using pure geometry with no graphs or datum curves via equations. In fact, I was surprised at how few features are needed. 5 features total and 2 of those are "Evaluate Features" used to drive the # of coils and the overlap on that long edge. I can easily modify the number of coils by changing a parameter and the overlap will remain the same. I could easily change that as well to give me whatever overlap I wanted. The sides are all flat and parallel to each other, no "S" bend anywhere. The rounded corners ARE helical as you'd expect, but the pitch is equal all throughout the model. Spent maybe a day on it.