Okay, so I doodled up a drawing on how it would be done using excel.
The green parts are just the tower/tripod. The taller the longer the "windup".
The green is the train of pulleys. The lower one movable, and the upper one fixed to the tower. As the weigh drops, the pulleys spins
The upper pulley, being fixed, is connected by belting to the generator pulley. That is represented by black
The red is a seperate rope that the oxen pulls to raise the weight.
This is all simple in concept, but sizing the pulleys and the amount of weight will take calculations/ and or trial and error.
The taller the tower, the longer the fall, and thus the longer the wait time in relifting the weight.
This system would work well for powering a battery bank as it is intermitten power, but if two tower systems were set up, and the drop taken enough
time, a set of oxen could alternate lifting the weights on each tower,yet have enough time to rest between lifts.