Early trolley power units

 Ok, we have electricity, electric motors and tracks, in the mid 1880s, Frank Sprague worked hard at combining the three. The 40th trolley pole and shoe design worked well enough to transfer the current while not jumping off or overheating.  Several iterations of motor and gearboxes were required to come up the right combination to have enough power to climb the grades of streets and roads and to survive the environment under the vehicles in which they worked. By 1888, he had the first trolley system working in Richmond, Virginia.