Roller skating tends to go in and out of style with each decade. Roller discos died out in the 1980s before roller-blades made a comeback in the 1990s. Even bacon skates were only hip in the 1930s.
Pedal skates, however, will forever be the coolest means of transportation for modern man. This variation on the classic roller skate was patented by Charles A. Nordling of Suisun, California in August 1913. The primary object of Nordling's contraption was "the provision of a roller skate in which the wheels thereof will be rotated on pedal action by the feet of the user, thereby avoiding the necessity of excessive exertion on the part of the skater." Since the skates required significantly less force, the skater would be less likely to drag his feet or lift the skate from the ground, thus enabling, as Nordling writes in his application, "the production of high speed."
Nordling's initial patent would later provide the basis for future mechanical roller skates, including Hyman Suroff's 1983 self-propelled roller skate and Zygmunt Piotrowski's 1991 step action wheel skate.
Old, Weird Tech archive.
Images: 1. Charles E. Nordling with his pedal skates, circa 1910; 2. The patent drawing for Nordling's pedal skates/U.S. Patent Office