Use this thing to test te maximum torque of your motor. It's designed for a motor with a shaft with a min. diameter of 4.5mm and a max. diameter of 5.0mm. This is the right size for a Nema 17 motor. The radius of the wheel is about 3cm. I made holes in the object to make it easy to connect a piece of string. If you don't like the size of the hole or the size of the wheel, you can edit it by using the scad file, but i didn't put any vars or comments in it, but that won't be a problem if you understand the open scad language.