pedrail

Pedrail \Ped"rail`\, n. [See {Pedi-}; {Rail}.] (Mach.)
   (a) A device intended to replace the wheel of a
       self-propelled vehicle for use on rough roads and to
       approximate to the smoothness in running of a wheel on a
       metal track. The tread consists of a number of rubber
       shod feet which are connected by ball-and-socket joints
       to the ends of sliding spokes. Each spoke has attached to
       it a small roller which in its turn runs under a short
       pivoted rail controlled by a powerful set of springs.
       This arrangement permits the feet to accomodate
       themselves to obstacles even such as steps or stairs. The
       pedrail was invented by one B. J. Diplock of London, Eng.
   (b) A vehicle, as a traction engine, having such pedrails.
       [Webster 1913 Suppl.]