Useful as it might have been, an indication to drivers of how fast their automobiles were actually moving was not an option for pioneer motorists. The first production cars sported no such frivolous extras, but the race to develop suitable technology had begun. Extrapolating speed from the time taken to travel a given distance had been used for centuries, but it was a system for indicating an automobile's speed in real time—the speedometer proper—that was needed.
The electric speedometer, in a form that would be recognized today, appeared between the late nineteenth and early twentieth centuries. Josip Belusic, a Croatian professor from the (then) Aystro- Hungarian region of Labin, was granted a patent for his electric "velocimeter" as early as 188-8. Other inventors were to produce various speedometers over the years that followed, and although most would achieve the required objective—to measure the rotational speed of the wheels or some rotating drive component, and relay that information to a calibrated gauge—it was the electric (electromagnetic) speedometer that claimed pole position. Otto Schulze's patent for such a device was issued on October 7, 1902, in Berlin.
In a typical assembly, one end of a flexible, rotating shaft is coupled to a set of gears driven by the vehicle's transmission. The other end connects to a permanent magnet housed in a small metal "speedcup." The speedometer needle is fixed to the other side of this cup. As the cable rotates, so the magnet rotates proportionately, generating eddy currents and thereby dragging the cup and its attached needle with it. A spring counteracts the turning force and the needle remains steady as speed varies.
