Samuel Leeds Allen filed his patent for a steerable sled on June 4, 1889. The patent described a modification to the standard fixed-runner sled that made it possible to steer by applying pressure to a front crossbar connected to pivoting front runners. The design produced a sled that could be directed around obstacles on a hill rather than simply pointed downhill and hoped for the best.
Allen was a successful farm implement manufacturer in Burlington, New Jersey who had made his money selling a seed drill called the Buckeye. He apparently built the first flexible-runner sled for his children and recognized immediately that it was the most useful sled anyone had made. He applied for and received his patent, named the sled the Flexible Flyer for its combination of steerable flexibility and speed, and entered the toy business.
The design is mechanically simple. The front of the sled has two short runners connected by a crossbar. This crossbar is attached to the main sled frame by a pivot, which allows the front runners to rotate relative to the back runners when the rider shifts weight or grabs the crossbar with both hands and applies torque. The back runners are fixed to the frame; the front runners pivot. The geometry converts lateral weight shift or hand pressure into directional change.
The wood slats on the deck serve a structural purpose: they distribute the rider's weight across the full width of the frame, reducing stress concentration at the mounting points. Ash was the preferred wood because ash is strong in bending, flexible rather than brittle, and takes paint and finish well. The steel runners reduce friction against snow; steel on packed snow has a lower friction coefficient than wood, which is why all serious sleds have steel runners and why antique wooden-runner sleds are either decorative or designed for loose powder snow.
The sled was named the Flexible Flyer because the company name was changed to the Flexible Flyer Company. The wing logo -- a stylized bird in flight -- has appeared on the packaging since the 1890s and is as recognizable a piece of American visual design as any product of its era. The red paint was standard from the earliest production runs.
Allen sold the business and the patent in the 1920s. The sled changed hands several times over the following decades and production moved to different facilities. The current owner continues production in the original design. The engineering changes since 1889 are primarily in materials: modern steel alloys in the runners, modern paints, modern screw and bolt specifications. The fundamental geometry of the steerable runner design is unchanged. It was correct in 1889. It remains correct today.