driving wheel

noun3

1. •
   On a steam locomotive, a powered wheel driven by the locomotive's pistons or turbine.

   • Just after leaving Milford the axle of the driving wheel of the locomotive broke, and before the train could be checked the trucks of the tender were thrown from the track; […] — 1860
2. •
   A wheel that transmits motion to other wheels or machinery.

   • [W]hilst this driving Wheel revolves once, the upright Wheel, or that which hath 8 Pinions, will revolve 5.625 Times; […] — 1752
3. •
   Synonym of steering wheel.

   • My mother would be smoking, ashes falling in her lap, she would be sitting on a cushion so she could see over the driving wheel. […] She would drive slowly so she could look at the houses carefully. — 1999