Why were early rescue pulleys inaccurately sized?

The sizing of early rescue pulleys was primarily based on the measurement of the outer diameter of the sheave. This approach led to inaccuracies because it did not take into account the inner working dynamics and the actual performance in relation to different rope types and diameters. The outer diameter alone is not a sufficient indicator of how well a pulley will function with a given rope; a pulley must accommodate the rope in a way that ensures optimal friction management, alignment, and load capacity.

By focusing solely on the outer diameter, manufacturers overlooked essential factors like the groove's shape, depth, and the internal mechanism, which can significantly affect how the pulley interacts with various ropes and their specific diameters. This caused an inconsistency in the fitting and performance of the pulleys in real-world rescue scenarios, leading to suboptimal results and safety concerns. Ultimately, a proper understanding of the relationship between the pulley dimensions and the ropes being used is crucial for effective rescue operations.