I wanted to make this one from a cool problem in my Dynamics class in college (a question that I got wrong by the way….). The beauty of this mechanism is you can crank either direction and the pulley piece in the middle will either extend or retract. The mechanical advantage is compounded as well with having long use length unlike a block and tackle system. You see these on sailboats to control the sails typically but they have uses anywhere you need to pull something up or down with some mechanical advantage.
Two 1/2″ #6 screws, one 3/4″ #8 machine screw and nut, a length of string (I think what I used was some twisted small diameter (1/16″) nylon string), and some 3/8″ dowel. For the weight the slots fit 3 quarters to help pull the mechanism better. It is also beneficial to wax the line that you have to keep the line from untwisting in the middle.
The thingiverse number is here.
Here’s a video: