Miller, John, in full JOHN AUGUST MILLER, original name AUGUST JOHN MUELLER (b. 1872, Homewood, Ill., U.S.--d. June 24, 1941, Houston, Texas), American designer of roller coasters, whose more than 100 patents include many safety innovations that remain key components of present-day roller coasters.

When he was 19 years old, Miller began working with roller coaster pioneer La Marcus Thompson, soon becoming his chief engineer. He also worked with noted designers Frederick Ingersoll and Fred and Josiah Pearce, eventually forming a partnership in 1920-23 with Harry C. Baker, who later built the famous Coney Island Cyclone (1927).

Miller in 1910 designed a device that prevented cars from rolling backward down the lift hill in the event the pull chain would break. It attached to the track and clicked onto the rungs of the chain. Known as the safety chain dog, or safety ratchet, it evolved into the device on the underside of cars that makes that distinctive clinkety-clank sound of wooden coasters.

Miller's most important contribution to coaster technology, though, was his 1919 patent of the underfriction wheels that keep coaster cars locked on their tracks, enabling them to safely reach high speeds, bank suddenly, and turn upside down. Underfriction wheels, also called upstop wheels, are still found on every roller coaster in operation.

Besides patenting ingenious inventions for coasters--including several types of brakes and car bar locks--Miller built his share of unusual "scream machines." The Dip-Lo-Docus (c. 1923), billed as "The Jazz Ride," featured revolving three-seater cars, whereas the Flying Turns (1929) consisted of cars with swiveling rubber wheels tearing through a half-cylindrical chute like a toboggan.

His Cyclone at Puritas Springs in Cleveland, Ohio, honored with a place on the Smithsonian Institution's list of Great Lost Roller Coasters, was hidden so much by foliage that only the boarding platform was visible to riders before they began to race through the ravine.

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