Movement No. 58 presents a highly ingenious multi-speed transmission system that delivers three distinct output speeds to a lower shaft using a clever arrangement of concentric hollow shafts, multiple pulleys, and spur gears of different sizes — all selectable by shifting a single drive belt. The input side consists of four pulleys mounted side by side. The first is a loose idler pulley — when the belt rides here, no motion is transmitted at all, giving a neutral state. The second pulley is fixed directly to the solid main shaft, which carries a small spur gear on its opposite end. The third pulley is fixed to a hollow shaft that runs concentrically over the main shaft — independent of it — and carries a second, larger spur gear on its other end. The fourth pulley is fixed to yet another hollow shaft that runs concentrically over the previous hollow shaft, also independent, carrying an even larger spur gear at its other end. All three spur gears of different sizes mesh with a common gear on the lower output shaft. When the belt is placed on pulley two, the main shaft and its small spur gear are driven — producing the highest output speed on the lower shaft due to the small gear ratio. When shifted to pulley three, the first hollow shaft and its medium spur gear are driven — producing an intermediate output speed. When shifted to pulley four, the outer hollow shaft and its large spur gear are driven — producing the lowest output speed with the highest torque. This elegant system of nested concentric shafts allows three completely independent speed ratios to be selected by a single belt shift, without requiring any gear-shifting mechanism — a remarkable feat of compact mechanical design used in machine tools and early industrial equipment.
58. For transmitting three different speeds by gearing. The lower part of the band is shown on a loose pulley. The next pulley is fixed on the main shaft, on the other end of which is fixed a small spur-gear. The next pulley is fixed on a hollow shaft running on the main shaft, and there is secured to it a second spur-gear, larger than the first. The fourth and last pulley to the left is fixed on another hollow shaft running loosely on the last-named, on the other end of which is fixed the still larger spur-gear nearest to the pulley. As the band is made to traverse from one pulley to another, it transmits three different velocities to the shaft below.