I've often heard of folks removing windings or wire loops from solenoids in their EM games to get a little more oomph and wondered how that works. I don't disagree that it does work but I wanted to understand it better than I did. I haven't read an explanation that really convinced me. I had my own theories but they involved a lot of hand waving and assumptions.
After taking a few runs at looking for an answer I finally took a stab at doing an experiment and studying the results myself. Here's the jig I put together for the experiment:
CoilStrengthJig (resized).jpg
It turns out that there's a lot going on and it can turn into a real rabbit hole. That may explain why I couldn't find a simple satisfying answer.
I also learned a few unexpected things along the way. Ever wonder why a flip seems stronger or weaker every now and then? I gathered up the highlights and tried explain the important bits in an intuitive way without getting bogged down in the math. It's probably still way more than most want to know.
But if you're still curious the whole saga is at:
https://www.funwithpinball.com/learn/solenoid-strength-test
/Mark