Currently 3d printing a jig to help me measure the force generated by a solenoid at various plunger distances. I'll put a 4kg weight atop a set of digital kitchen scales on the floor, with a bracket atop the weight that holds some kevlar fishing line/thread directly above the middle of the weight. Then I'll have a pulley that converts that upwards force into a sideways force, where the thread is tied to the end of the solenoid's plunger. So if the plunger is being pulled by 300g of force, the scales will read 3700g. Then I'll have a really small pulley with a long handle with which to slowly pull the solenoid housing itself further away from the plunger. I may connect this to a stepper motor to gradually reel the solenoid apart while I film, otherwise I'll just measure discrete steps with increasingly magnetized calipers.

The pulleys will both be fastened to a length of dressed timber, pic related is the main horizontal-to-vertical pulley. Chances are I'll have to clamp this length of timber to a table.