After the tests with the two electric locomotives on the Spiez-Frutigen route, conclusions were drawn from the experience as to what a new, series-built locomotive should look like. The F 2x3/3 impressed with its power train, while the Fb 2x2/3 with its carrying axles improved running smoothness and the ability to negotiate curves. That is why the decision was made to order a similar power train from the manufacturers of the F 2x3/3 locomotives, but instead of bogies they were equipped with coupled axles fixed in the frame and a carrying axle at each end. Additional electrical assemblies were supplied by BBC to shorten delivery times. A total of 13 locomotives were delivered in 1913, which were to pull both freight and passenger trains on the newly built mountain route, including the 14.6 km long Lötschberg tunnel.

In order to achieve good running characteristics, three of the five driven axles could be moved sideways. While the middle one could be moved by 25 mm, the first and fifth were each mounted with the adjacent carrying axle in a Krauss-Helmholtz bogie. With the lateral deflection of the carrying axles by a maximum of 78 mm, they were moved by up to 40 mm. Despite the five driven axles, this made a fixed wheelbase of just 4,500 mm possible.

Between the second and third, as well as between the third and fourth coupled axles, there was a 14-tonne series motor on the frame, which drove a jackshaft via a Citroën gearbox underneath. By means of a rod triangle on each side, both engines acted on the middle axle. Since the rod triangles often broke under the high load during operation, they were later replaced with cast pieces. In order to achieve a large number of speed steps with a relatively small number of taps on the transformers, the next of the twelve steps of only one of the motors was switched alternately to obtain a total of 24 steps.

Schematic drawing

Die Lokomotive, June 1914

With an hourly output of 2,500 hp, the Fb 5/7, which was soon renamed the Be 5/7, was the most powerful electric locomotive in the world. On the ramp with a gradient of 2.7 percent, it was able to pull trains weighing 330 tonnes at 50 km/h. After the predecessor locomotive had been moved to flatter routes, the Be 5/7 was the only locomotive used on this route. Thanks to the good running characteristics, the locomotives were later approved for 80 instead of 75 km/h, one locomotive was even equipped with four smaller motors and could run 90 km/h. From the second half of the 1940s, they were increasingly pushed into freight train service b the Ae 4/4 and when the Re 4/4 were delivered in 1964, they were quickly scrapped.

At the time of the First World War, the government of the Canton of Bern decided that the branch lines of the BLS Group should be electrified and operated with the abundant water power available in order to do something about the acute shortage of coal. An electric locomotive had to be developed for these railways, which would achieve a low axle load and could replace the existing steam locomotives in all train types. This meant exactly that at 1.5 percent 310 tonnes should be pulled at 35 km/h, as well as 180 tonnes at 2.5 percent at the same speed. In addition, these speeds should not only be maintained, but it should also be possible to accelerate these weights from a standing start to the specified 35 km/h within four minutes.

To speed up development, a scaled-down version of the Be 4/6 introduced at the SBB at the same time was created. 14 units were initially built in 1920 and three more in 1924, which were slightly more powerful and 10 km/h faster. They were spread among the BLS subsidiaries and, if necessary, exchanged with one another. Since they were created by order of the government, they quickly earned the nickname “decree mills”.

In their original design, the locomotives had two bogies, each with two coupled axles and one carrying axle. The buffers and couplings, as well as small hoods were attached to the bogies. This meant that the locomotives could actually be assigned to the design of the crocodiles, which, however, was rarely actually stated due to the very small front end. The power came from a traction motor that stood on the bogies and drove a jackshaft.

Schematic drawing with dimensions

Locomotive Magazine, May 1921

Between 1954 and 1956, the carrying axles and front hoods were removed from the ten most recently built locomotives, since the branch lines could now cope with the higher axle loads. They could now come up with a higher adhesion mass and were given the designation Ce 4/4. The engines that were not converted were retired by 1973 at the latest, the converted ones between 1975 and 1988. Two units with only one traction motor were in service for a long time as shunting locomotives in the Böningen workshop. A Ce 4/6 and a Ce 4/4 are still preserved today.

In order to improve the running characteristics of the E 77, the E 75 was developed with a one-piece frame. The powered axles were further divided into two groups, but here they were mounted within the frame. Contrary to expectations, the running smoothness hardly improved, so that the speed could only be increased from 65 to 70 km/h. Of the 79 E 75s ordered, only 31 were ultimately delivered. They were used in front of passenger and freight trains and after the Second World War were mostly used by the Bundesbahn. Three were modernized in the early 1960s and the last commercial operations took place in 1972.

When the Mariazell Railway was electrified between 1908 and 1911, both the trackside equipment and the locomotives were to be supplied by the Austrian Siemens Schuckert Works (ÖSSW). For the first time in history, a longer stretch of track was electrified with one-phase AC. Here, the system of choice was a unique combination of 6,500 Volts at a frequency of 25 Hertz. 16 locomotives were built which were designated class E by the NÖLB.

While the electrical part of all locomotives came from ÖSSW, the mechanical part of only 13 was built by Krauss at Linz. Two came from Floridsdorf and one from Weitzer at Graz. The locomotives stood on two bogies each which had three axles and one unsprung traction motor that transmitted its power via a crank axle and coupling rods. Each locomotive had one of two different gear ratios either for the flatter or steeper sections of the line.

In 1923, the line came under the control of the BBÖ and the class was still named E. In 1923, the gear ratios of all locomotives was equalized. In 1938 the Reichsbahn designated them E 99 and likewise, the ÖBB called them class 1099 after the war. Between 1959 and 1962, they were rebuilt thoroughly where most of their electric equipment and their outer appearance changed.

Only in the year 2000, the first locomotives were stored. In 2010, the ownership of the Mariazell Railway changed from the ÖBB to the NOVÖG. Soon more were retired after new Stadler EMUs had been introduced. In 2013, more than 102 years after their introduction, the last one was retired from regular service. But some continued to be used for tourist trains, for snow clearing or in construction trains.