SBB-CFF-FFS Re 620

SBB-CFF-FFS Re 620
Re 620 and Re 4/4II or III leading a freight train on the northern Bözberg incline
Type and origin Power type Electric Builder SLM Winterthur BBC Baden SAAS Geneva Build date 1972, 1975–1980 Total produced 89
Specifications Configuration: ​  • UIC Bo'Bo'Bo' Gauge 1,435 mm (4 ft 8 1⁄2 in) Length 19,310 mm (63 ft 4.2 in) Width 2,950 mm (9 ft 8.14 in) Height 3,932 mm (12 ft 10.80 in) Loco weight 120 t (118.1 long tons; 132.3 short tons) Electric system(s) 15 kV  16 2⁄3 Hz AC Catenary Current source Pantograph
Performance figures Maximum speed 140 km/h (87 mph) Power output 10,700 hp (8,000 kW) Tractive effort: ​  • Starting 395 kN (89,000 lbf)  • 1 hour 270 kN (61,000 lbf)  • Continuous 235 kN (53,000 lbf)
Career Numbers 11601 – 11689

The Re 620, Re 6/6 in the old numbering scheme, are six-axle, electric locomotives of the SBB-CFF-FFS, which were acquired as a replacement for the Ae 6/6 for heavy services on the Gotthardbahn. They are the most modern of the so-called "Gotthard locomotives".

To reach the necessary tractive effort, a construction comprising six driven axles was necessary. In order to still get good running characteristics in curves, they were built into three two-axle bogies instead of two three-axle bogies as on the Ae 6/6. The middle bogie can move sideways, and the three bogies are connected by elastic cross couplings. Two of the four prototypes were built with a split locomotive body, whereby the joint may only move on an horizontal transverse axis, not on a vertical axis, to accommodate to gradient changes.

The other two prototypes got a softer secondary suspension instead of the joint, which proved to be so reliable in everyday use that all series locomotives were built this way.

Nevertheless, the two prototypes with a split body are still in regular operation.

At time of construction, and nowadays still one of the world's most powerful locomotives, see List_of_largest_locomotives.

The exterior design is similar to the Re 4/4^II, as are the driver's controls and the conventional transformer technology with fixed running notches, which was applied for the last time for this locomotive. In contrast to the Re 4/4^II, the Re 6/6 has two transformers (one power and one control transformer), which are mounted on the frame between the bogies. Due to the higher roof, the Re 6/6 looks more brawny than the Re 4/4^II, especially when seen from the front side.

The Re 6/6 is equipped with multiple unit train control together with Re 4/4^II, Re 4/4^III, Re 4/4^IV and RBe 540. In passenger traffic they pull heavy passenger trains over the Gotthard route (as an alternative to a double heading of Re 4/4). In freight traffic they are used all over Switzerland for heavy trains, on the Gotthard route very often together with an Re 4/4^II or Re 4/4^III. Such a couple, often referred to as "Re 10/10" (both locomotives are Re class, so the couple is Re class; 10/10 means that they overall have 10 driven axles out of 10), is capable of pulling the maximum train weight of 1,300 tonnes (1,300 long tons; 1,400 short tons) on 2.6% gradients of the Gotthard line. For heavier trains, up to 1600 tons are operationally feasible; an additional bank engine has to help push the train in order not to overload the couplers.