On a horse car, the wheels had to do no more than to carry the car at low speeds with reasonable comfort to passengers, and so the method of attaching them could be simple. All that was needed was a set of four journal boxes, able to move vertically in cast iron wheel guides – “pedestals” – that were attached directly to the wooden frame of the car. The journal boxes held the ends of the two axles and supported the car through springs, providing a smooth ride.
Although the earliest electric trolleys followed closely the designs commonly used for horse cars, there was more to building a reliable electric car than just adding electrical equipment. Ways had to be found to carry a motor and to transmit power from that motor to the wheels. Because of Newton’s Third Law of Motion – for every action there is an equal and opposite reaction – because the amount of power that had to be transmitted was considerable, and because the motors were heavy, a much sturdier arrangement was necessary than required on a horse car.
Frank Sprague, in developing the first really reliable electric streetcar, realized that the most effective arrangement was to transmit that power to the wheels as directly as possible. He also realized that he needed a structure that could both carry the considerable weight of those motors and resist the reactive thrust produced by the motors working against friction and the car’s inertia. Finally, he needed to protect the motors from jarring caused by imperfect track.
To do so, he developed a truck on which the body of the car rested. This truck consisted of a sturdy iron frame that carried both the journal pedestals and the motors. One end of each motor was supported by, and free to rotate around the axle and the other, through a spring, by the frame. With this “wheel barrow” mounting, the motors could be geared directly to the wheels. The journals supported the truck frame through springs. Thus, Sprague created an arrangement that could provide direct contact between the motors and the wheels, could withstand all of that thrust, and could carry the weight of both the motors and the car through springs that minimized jarring to both.
Author: G.T. Atwood
While Frank Sprague’s ingenious “wheelbarrow” motor mounting and heavy-duty truck designs revolutionized how power was delivered to the rails, bringing those mechanical innovations back to life is an ongoing, hands-on labor of love right here at the Northern Ohio Railway Museum. If you appreciate the engineering marvels behind early electric transit, we invite you to share this story with a fellow history enthusiast, check our operating schedule to plan an upcoming weekend trip to Seville, or support our non-profit preservation mission through a membership or donation to keep Northeast Ohio’s railway history moving forward.