A few things the photos don’t show clearly:

1.  The pulley 1 1/2” bolt shaft is free to move up and down in a slot in the vertical wood frame.

2.  A 1/4”  rod is tapped into the 1/2” bolt shaft and extends out the bottom, from which weights are suspended.

3.  I use “saltwater” size sinkers for weight.  I have an assortment of 4, 6 & 8 oz. sinkers.