Onward Locomotive

Onward was an experimental steam locomotive built in 1887 by the Hinkley Locomotive Works of Boston on commission from the Swinerton Locomotive Driving Wheel Company to test a driving wheel design intended to improve a locomotives grip on the rails. Rather than conventional round driving wheels, Onward used a single driving axle carrying wheels shaped as one hundred eighteen sided polygons, with each flat facet of the wheel only about two inches long, on a locomotive built with a four two two wheel arrangement, the idea being that the flat facets would give the wheel a short line of contact with the rail instead of the single point of contact a round wheel provides, in theory improving adhesion. The design did not deliver the hoped for benefit in practice, and railway operators did not adopt it, most likely because the varying radius of the polygonal wheel introduced vibration into the ride; the locomotive was later fitted with conventional round wheels, sold to the Portland and Rochester Railroad, rebuilt as a standard eight wheeler, and finally scrapped in 1905.