I've got a couple of crank-open casement windows that are rather annoying to get to. I would like to motorize them. I searched for existing solutions and found them all to be ludicrously expensive. So I want to make my own. I would like some general advice on how to go about this, but I also have a specific question.
Using a luggage scale, I measured the torque necessary to turn the crank and found that it's about 18 kg cm with the window half open, and about 36 to open the window when it's been tightly shut. Shopping around on Amazon shows plenty of motors that can do that with ease. But how do I attach a motor to the crank stud? That's where I need advice.
Removing the crank shows that the crank stud is splined with 12 teeth. What sort of coupling do I use to attach to that?