Today, sectional windmills. The University of Houston's College
of Engineering presents this series about the machines that make
our civilization run, and the people whose ingenuity created
them. The problem of pointing windmills into the wind is a
century old. Medieval mills had a long strut that let millers
turn the whole fan structure on a central post as the wind
shifted. Mid-18th-century British engineers invented a secondary
fan blade, rather like the control propeller on a helicopter
tail. It was set perpendicular to the main fan. When it turned
it drove a mechanism that turned the mill until it faced
straight into the wind. But new windmill uses arose in 19th-
century America as we settled the Great Plains. There, we didn't
need to power large grain and textile mills. We needed small
reliable windmills to pump water for cattle troughs and steam
locomotive boilers -- windmills to function with minimal
maintenance and management. They had to stay pointed into light
winds, and had to shut down in strong w