When the almost 20 km long Simplon Tunnel opened in 1906, it was operated with 3,000 V three-phase current. The five locomotives initially used included the numbers 361 to 363, rented from the Rete Adriatica, as well as the numbers 364 and 365, built by the SLM and BBC, which were externally very similar. These were all designated Fb 3/5.

Also on the newly built locomotives, the two traction motors were mounted in the frame and drove three axles via triangular rods. However, the control here was not via a cascade connection, but rather via pole switching, which resulted in continuous speeds of 37 and 74 km/h. They were designated Be 3/5 from 1921 and remained in use until 1930, when the line was converted to single-phase alternating current.

After the first type Fb 3/5 three-phase locomotives, two more were delivered that did not have carrying axles. The aim was to use the entire weight of the locomotive as adhesive weight, and the locomotives were still capable of a top speed of 75 km/h. This was possible because the outer axles were designed as Klien-Lindner hollow axles. The power was provided by two traction motors arranged low in the frame via jackshafts and coupling rods. 

Thanks to new traction motors, an hourly output of 850 hp could now be accessed per motor. In addition, the pole-changing now allowed four continuous driving speeds of 28, 37, 56 and 74 km/h. Since the traction motors were independent of each other, if one motor failed, the second could still to be used. Since the technology proved so successful, two more locomotives were built in 1919. They were used until 1930, when three-phase operation was ended.

As one of three types of flatland universal locomotives, the SBB introduced the Ae 3/5 built by the SLM from 1922 onwards. Since the electrical part came from SAAS, it was nicknamed “little Sécheron”. The power came from a twin motor per axle. With only five axles in total, it had a better power-to-weight ratio than its six-axle competitors, but poorer running characteristics at higher speeds.

Since the express trains tended to be pulled by six-axle machines, the Ae 3/5 was primarily used in regional traffic. In the 1960s, nine locomotives were converted for use with car trains. The first retirements due to wear and tear took place in the late 1960s. However, the majority of the locomotives were retired between 1979 and 1983.

With progressive electrification at the SBB, on the basis of tests with the Fb 2/5 the Buchli drive was selected as the preferred drive for express locomotives in the lowlands. The Ae 3/6^I now had the asymmetrical wheel arrangement 2-C-1, since the bogie had to carry the transformer. It could initially be approved for 90 km/h and later for 100 km/h. The last 78 locomotives built after 1925 were designed for use with lightweight express trains at speeds of 110 km/h. With the delivery of the Re 4/4^I, they were increasingly used with passenger and freight trains. In the end, they were mainly used with regional trains until the last ones were finally retired in 1994.

As part of the planned electrification of the entire network after the First World War, the SBB needed a universal locomotive for lines in the flat country. An engine with three driven axles, an output of 2,000 hp, a top speed of 90 km/h and a maximum axle load of 20 tonnes was specified. In addition, special scenarios were specified that had to be completed within a certain time. For example, this involved three round trips on the 117 km route between Villeneuve and Brig with a 480-tonne passenger train. These should be able to be completed in a total of 11.5 hours, including a 15-minute stop at the end stations. In response to these requirements, BBC developed the Ae 3/6^I, Oerlikon the Ae 3/6^II and SAAS the Ae 3/5.

Since Oerlikon did not have a tried-and-tested single-axle drive to offer at the time, Switzerland's last faster rod-driven electric locomotive was developed. It was based on the Fb 3/5 No. 11201 developed for the Gotthard Railway and, like these, had two motors that drove three axles via crankshafts, triangular connecting rods and coupling rods. The traction motors each weighed ten tonnes and, with a diameter of 1,800 mm, were the largest ever used in an SBB locomotive.

Since only one transformer was now required and this could not be arranged in the middle for reasons of space, an asymmetrical axis arrangement was used. At the end of the locomotive where the transformer was located, there was a bogie with lateral play of 80 mm. At the other end there was only a bissel axle, which had a play of at first 83 and later 70 mm. The middle drive axle could also slide by 15 mm. Despite the rod drive, this chassis was enough for the specified maximum speed of 90 km/h, which was even increased to 100 km/h in 1929.

After the first 20 vehicles, some weak points became visible, which were remedied in the next 40 vehicles. In the first series, the transformer proved to be too small compared to the traction motors, so later a stronger but lighter one was used. The steps of the tap changer in the lower portion were also distributed too roughly, which led to rough starting behavior and led to a different distribution in the later engines.

Initially, the production of the locomotives was faster as the area of application grew with progressive electrification. As a result, some locomotives were temporarily classified as surplus, although all express, passenger and freight train traffic between Basel and Lucerne was handled with the Ae 3/6^II. The 60 engines were soon spread over a large area in the flatter parts of northern Switzerland, but were increasingly pushed east with the advent of the Ae 4/7. Later they were increasingly used in tasks such as the pilot service and were discarded between 1965 and 1977. Today only the number 10452 is preserved, which is used every now and then and carries the number 10439.

As the Ae 3/5 designed for the newly electrified flat lines of the SBB had insufficient running characteristics in curves, a locomotive called Ae 3/6^III was built in 1925 that was intended to solve this problem. By changing the Bissel axle on one end of the locomotive against a two-axle bogie, both the wheelbase and the guidance in curves were to be improved. Since the Ae 3/5 was called “small Sécheron”, the Ae 3/6^III got the nickname “medium Sécheron”.

The electric part made by Sécheron was virtually identical to that of its predecessor. This means that they had the same 1,365 kW hourly output and the same Westinghouse quill drive. Apart from this, the changes in the chassis didn't bring the desired effect and the top speed was still limited to 90 km/h. Nevertheless, ten more have been built in 1925 and 1926. They were retired between 1968 and 1980 and today, 10264 is being preserved in an operational state by SBB historic.

To avoid the use of helper locomotives or double heading altogether on the Gotthard, the SBB ordered two prototypes of heavy electric locomotives from the SLM. In order to use them on the whole route without changing the locomotives, they had to have a top speed that was fast enough for passenger trains on the flat sections. Each half of the double locomotives was built with four driving and three carrying axles. They had a device that could increase the adhesive weight by removing weight from the carrying axles. 

The first prototype delivered in 1931 was No. 11801. It had Buchli drive units on one side and technically resembled a double Ae 4/7. 11851 delivered in 1932 had SLM universal drives and somewhat more power. In 1938, a third streamlined locomotive with a powertrain similar to 11851 was built. It got the number 11852 and was called “Landi-Lok” since it had been built to be exhibited at the Swiss National Exhibition. With an hourly output of 5,514, 6,470 and 8,162 kW (7,500, 8,800 and 11,100 hp) they were the most powerful locomotives in the world at this time.

The “Landi-Lok” No. 11852 with aerodynamic fairing

SBB Historic

After these three locomotives, no more Ae 8/14 have been built. With the advancements in multiple controls, it was more feasible to use a smaller locomotive on the flat sections and add another one at the beginning of the ramp. After only the first two had been built for the SBB, also the third was bought up by them since there was demand for heavy freight locomotives at that time. After the third was retired due to a fire in 1971, the others remained in service until 1975 and 1976. Today the first one is operational and the third one came to the SBB Historic team at Erstfeld in June 2024 after being on static display in Lucerne.