A prototype locomotive, SBB-CFF-FFS Ce 6/8 I number 14201, was ordered in June 1917. The production "Crocodiles" were the series SBB Ce 6/8 II and SBB Ce 6/8 III locomotives of the SBB, Swiss Federal Railways, built between 1919 and 1927. There were 33 class Ce 6/8 II and 18 class Ce 6/8 III, making a total (excluding the prototype) of 51 locomotives. These locomotives were developed for pulling heavy goods trains on the steep tracks of the Gotthardbahn from Lucerne to Chiasso, including the Gotthard Tunnel.
The electric motors available at the time were large and had to be body-mounted above the plane of the axles, but flexibility was required to negotiate the tight curves on the Alpine routes and tunnels. An articulated design, with two powered nose units bridged with a pivoting center section containing cabs and the heavy transformer, met both requirements and gave excellent visibility from driving cabs mounted safely away from any collision. The two motors in each nose unit were geared to a jackshaft between the drive axles farthest from the cab, with side rods carrying the power to the drivers. These locomotives, sometimes called the "Swiss Crocodile" or "SBB Crocodile", were highly successful and served until the 1980s. Märklin published a book about their history in 1984.[3] Several are still in operation as preserved historical locomotives.
Between 1942 and 1947, thirteen members of class Ce 6/8 II were upgraded with more powerful motors, to allow a higher top speed, and these became class Be 6/8 II. This required raising the jackshaft above the plane of the axles, necessitating a more complex system of side rods. In 1956, all eighteen members of class Ce 6/8 III were upgraded and became class Be 6/8 III.[4]
As well as standard gauge Crocodiles, there are also narrow gauge versions. The best known are the Rhaetian Railway (RhB)'s metre gauge locomotives of class Ge 6/6 I, the Rhaetian Crocodile. Several of these still run on passenger trains on special occasions. They are also used on freight trains in busy periods. The Bernina Railway (later merged with the RhB) also built a single Crocodile type, the Ge 4/4, nicknamed the 'Bernina Crocodile'. This locomotive survives and is being restored to operating condition.
Two other Swiss narrow-gauge railways also have locomotives nicknamed Crocodiles; the BVZ Zermatt-Bahn (BVZ) (which merged with the Furka Oberalp Bahn (FO) in 2003 to form the Matterhorn-Gotthard-Bahn) uses series HGe 4/4 I, known as the Zermatt crocodile, while the Chemin de Fer Yverdon-Ste. Croix owns a solitary class Ge 4/4 #21. Neither of these locomotive types have an articulated body, which leads some railfans to nickname them "false crocodiles".
