It was common knowledge on California wind farms in the 1980s that one way to stop the rotor from spinning out of control was to somehow get a rope tangled in the rotor. The rotor would then wind up the rope, wrapping it tightly around the main shaft, slowing the rotor if not stopping it. To get the rope into the rotor, it was necessary to shoot an arrow towards the rotor with a line attached. If successful, the spinning rotor would do the rest. Whether this technique was discovered by California’s homegrown wind smiths, or learned by them from their Danish colleagues we’ll never know now. I remember it being used when I started with Zond in April 1984 to corral a runaway Danish machine in high winds. It was a Bulwer-Lytton moment, literally a “dark and stormy night” when Zond’s technicians were grabbing their hard hats and “heading up the hill” to rescue the turbine from destruction.
The technique is part of the historical record. Danes had used this method on Lykkegaard machines at the turn of the 19th century and with the rise of modern wind energy they had to learn how to use it again.
Here’s Preben Maegaard’s passage about it.
“The Borre windmill was erected and tested at the Risø test station. During testing things went wrong. When the wind was strong, the windmill speeded up; an attempt was made to stop it with a lasso to throw ropes up into the rotor when the windmill started racing, a method which had been practised at runaways of the thousands of la Cour windmills on Danish farms in the period 1905 till 1950. The local blacksmith was called in; it was his task to stop the windmill, employing the lasso and ropes that were to get entangled in the blades. However, the run-away drama did not always have a happy ending—the windmill disintegrated.”[1]
[1] Preben Maegaard, “16. Consigned to Oblivion,” in Wind Power for the World: The Rise of Modern Wind Energy, vol. 1 (Singapore: Stanford Publishing, 2013), 355–87, p. 378.
