I'm in the works of writing my own gear program, but I've stumbled on something that textbooks and the internet don't seem to answer. A lot of the time, the dedendum of a gear cuts into the base circle. When this happens, the curve below the base circle cannot be involute. Here is an example:
I'm using a simple line at the moment, but the actual curve looks closer to a fillet/spline curve. Here is an example of what it should look like:
This image comes from Shigley's Machine Design. This phenomena is known as undercutting and I try to avoid it, but sometimes I am limited by size and have to design a gear with a little undercutting.
I was wondering if anyone had any knowledge of this before I just make up some spline relationship.
