"Balls to the Wall"

Posted by B.Barclay on December 06, 2004

The phrase is much older than Airplanes. It goes back at least 100 years to the days of the stationary steam engines and refers to the speed regulator that kept the output speed constant. The "balls" were attached to the outer horizontal corners of diamond shaped 4-link mechanism mounted vertically on a shaft that spun in proportion to the output speed of the main drive pulley or gear. The upper corner of the diamond was fastened to the shaft and the bottom corner was fastened to throttle that applied more or less steam to the engine. The faster the shaft turned the further the balls extended horisontally due to centrifugal force, and higher the bottom of diamond rose and the more steam was applied and the faster the engine ran. The engine's fastest speed was when it ran with the "balls to the walls."
There is some advantage to being older than dirt!