What Are Those Slots Used For?

This photo shows the inside the Estate Bodkin sugar windmill, focusing on the arrangement of vertical slots around the top and the operation of the mill cap. A tour guide’s explanation during a Tan-Tan tour, suggested that the cap was mounted in these slots, and raised, rotated and lowered, for trimming the sails, a notion that the author, an engineer, found to be inaccurate after conducting research.

In the 1700s, engineers were highly skilled, and the mills were meticulously engineered. The author highlights the importance of studying historical paintings to learn from these engineering marvels. The process of rotating the cap to trim the sails involves using a long pole and a track system for support. The schematic of Estate Solberg in Charlotte Amalie, St. Thomas, provides a clear illustration of this mechanism.

In this diagram we clearly see the slots, and although the text is hard to read, it says:

“Recesses in masonry which held posts to support the track on which the hood rotated – recesses edged with yellow brick”

So the beams inserted into the slots served two purposes: they provided the top bearing support for the drive shaft (like a wagon wheel’s spokes); and they provided support for the cast iron track which the wheels of the cap would run on.

Mystery solved 🙂

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