THE ABT RAILWAY.

The locomotives used a unique rack system invented by a Swiss engineer named Roman Abt. This enabled the locos to negotiate the steep gradients through the mountainous terrain. The "rack rail" was laid midway between the standard gauge rails and raised 130mm above their level. The rail was fixed to the sleepers and comprised two parallel rows of overlapping teeth. When the rack system was engaged the rack cylinder of the loco turned a toothed pinion wheel, which fitted into the toothed rail and allowed the engine to haul itself up the line. While the rack cylinders provided power over the rack rail, the ordinary cylinders drove the wheels on the outside rails, providing dual means of locomotion. Once the rack system was disengaged the steam supply to the rack was cut off and the loco got it's power from the conventional cylinders only. The Abt system not only assisted the locos up the hills it also acted as a brake on downhill slopes thus enabling heavier loads to be carried safely.