Swiss Federal Railways Be 4/7

The Be 4/7 was a small series of six passenger locomotives which were built in 1921 and 1922 by the SLM with the electric part from Sécheron (SAAS). Analogous to the smaller Ae 3/5, they were called “Large Sécheron”. They originated in a catalog of requirements that included, among others, a top speed of 75 km/h and a dynamic brake. Additionally, a 300-tonne train had to be safely started and accelerated to 50 km/h on an incline of 2.6 percent.

Each locomotive stood on two bogies with two powered and one leading axle each. One of the bogies had an additional carrying axle in the middle to reduce the maximum axle load to 18.5 tonnes. Each axle was driven by a double motor via a Westinghouse quill drive that had been license-built by Sécheron.

After tests between Bern and Thun, they were used on the Gotthard from 1923. Despite good results in service, no more locomotives of this type were built. It took only until 1928 for the Ae 4/7 to replace the Be 4/7 in their role. Now they were used on flatter lines and in the late thirties, the top speed was increased to 80 km/h. The first three were withdrawn in 1966 and 1968 after they had suffered damage, the rest followed in 1976. Today, 12504 is preserved and operational.