What mechanism allowed Halladay's windmill to automatically slow down when the wind became too strong?

Answer

The tail vane swung the fan head out of the wind

A critical self-regulating feature involved the tail vane automatically pivoting the fan head sideways, moving it out of the direct path of strong winds to slow the rotor down and prevent mechanical damage.

What mechanism allowed Halladay's windmill to automatically slow down when the wind became too strong?
inventorAmericawindmill