The Re 4/4I is a light electric express train locomotive of the Swiss Federal Railways (SBB for short) introduced 1946, which was built in two different series. These locomotives are the first bogie locomotives of the SBB. The SBB deliberately opted for a light fast train locomotive with only about 14 tons of axle load in order to be able to operate at even higher cornering speeds.
Their main remit was to run express trains on the east–west rail axis of Switzerland. The locomotives originally designated as Re 4/4 were displaced in the 1960s by the RBe 4/4 engines with a high performance and a little later the much more powerful Re 4/4II in other services. Due to the Re 4/4II's introduction, the Re 4/4 was renamed to Re 4/4I.
Background From 1935, the SBB used the light railcars of the type , the so-called Red Arrows. These could run at a top speed of 125 km/h. The vehicles were very popular from the beginning. For these short trainsets, however, their use was constrained. In particular, the limited seating in a fixed trainset was problematic.
For urban traffic between Zurich and Geneva, so-called light express trains with Ae 3/6Is were therefore operated from spring 1936, whose maximum speed was increased to 110 km/h (numbers 10637–10714). The trailer load was limited to 150 t, which resulted in a three wagon limit for the existing rolling stock. With the introduction of light steel wagons from 1937, more passenger train cars could be attached, but the maximum speed remained 110 km/h. In 1937, the SBB procured two three-part railcar trains 501 and 502 that were able to reach 125 km/h -- even having reserve power for a maximum speed of 150 km/h. But they were also trainsets with the corresponding seating capacity problems, and, due to prewar fuel shortages affecting road use, passenger traffic demands on the SBB increased.
In 1940, the three baggage-compartment railcars were put into service. These met the requirement of maximum speed of 125 km/h. In terms of performance, however, these locomotives were too weak with only . The express trains would have needed to be run with uneconomic double or triple engines. In addition, one to two unused baggage compartments would also have been carried per train.
At the same time, the Berner Alpenbahn-Gesellschaft Bern-Lötschberg-Simplon (BLS for short) railway was looking for a replacement for its old locomotives. A speedy bogie locomotive with an output of 4000 hp was required. The industry met these requirements in 1944 impressively with the Ae 4/4 weighing 80 t and that ran at 125 km/h. However, it had a 20 t axle load, too heavy for the 14 t the SBB needed.
Specification
The SBB needed a light, high-speed locomotive that had to meet the following criteria: The locomotive should be able to drive at the same cornering speed as a light railcar, which meant 10 km/h faster than other locomotives. The static axle load could therefore not exceed 14 t. The locomotive had to carry trains up to 300 t on inclines of up to 12 ‰ with the same speeds and running times as the light railcars. On inclines up to 10 ‰, a train with 480 t, corresponding to 15 light steel wagons, should be able to run at 75 km/h and on a flat track at 125 km/h. A regenerative brake had to be available, with which the locomotive weight could be braked at 38 ‰ slopes and part of the trailer load at smaller slopes. An electropneumatic hopper control with 24 driving and at least 8 braking levels should be installed. The locomotive had to be able to be controlled remotely by a control car or a second locomotive. The appearance of the locomotive should match the light steel cars.
In fact, only the Re 4/4 of the first series met these criteria. The second series had no electric brake and therefore no regenerative brake and brake levels. The second series could not be controlled remotely from a control car or a second locomotive.
Contract award
Project planning started in May 1943. In January 1944, the Board of Directors granted SBB a loan of CHF 4,200,200 for the procurement of six electric locomotives of the type Re 4/4.
The order to the Swiss locomotive industry was divided as follows: Swiss locomotive and machinery factory (SLM): Mechanical part and assembly of the BBC spring drive. Maschinenfabrik Oerlikon (MFO): assembly drawings and circuit diagrams for the electrical equipment, one third of the traction motors, all equipment of the utility power brake, auxiliary machines and instruments for engine, train heating, auxiliary power and lighting circuits. Brown, Boveri & Cie. (BBC): two thirds of traction motors, transformers, air main switches, pantographs and other high-voltage apparatus. Société Anonyme des Ateliers de Sécheron (SAAS): electro-pneumatic jumper control.
The contractors provided a significant advance in the locomotive power-to-weight ratio. For the Re 4/4 it was 44 hp/t, whereas for the earlier SBB Ae 3/6 locomotive it was 22 hp/t.
Commissioning
Series Road number* Trial dates Remarks before 1965 after 1965 from until 1st 401–406 10001–10006 22 Jan 1946 26 June 1946 with multiple-unit controls 407–416 10007–10016 17 Sep 1946 17 Apr 1947 without multiple-unit controls 417–426 10017–10026 31 May 1948 18 Nov 1948 driver's desk forstanding and seated operation 2nd 427–450 10027–10050 25 Apr 1950 2 Nov 1951 without electric brakes and front doors *The pre-1965 numbers were anomalous. At this time it was customary to use three-digit numbers for railcars and express train steam locomotives. Four-digit numbers were provided for steam locomotives and diesel locomotives, and five-digit numbers for electric locomotives. Nevertheless, the locomotives received three-digit numbers.
On delivery, the SBB was not happy that the locomotive was 1 ton heavier than the contract specified. The excess weight did not impair its performance, however, and the unit was immediately drafted into scheduled service. The multiple-control features were tested and proved to be reliable after delivery of the remaining prototype units. Weight reduction was probably among the reasons for the lack of multiple-control on further units in the 1st series, as well as being expensive by the SBB's reckoning.
Technology
Chassis, motors, equipment
The arrangement of the machinery and electrical equipment is almost the same for both series. However, there were differences in body layout. A high-gloss forest green body color matched the color of the light steel passenger wagons the locomotive was built to carry.
1st series (401–426)
The right side corridor served for direct access to the machinery and equipment. The left side aisle was completely separated from the installations with a partition wall to allow passage for train personnel and passengers, for example, if the locomotive was remotely controlled by a control car and additional passenger cars were attached behind an intermediate locomotive. For the same reason, the 1st series had front doors, junction plates and bellows. The cooling air was sucked in on one side by low-lying blinds, which were on the side facing away from the passageway. This feature later caused considerable problems. Above it, as on the other side, were four windows.
2nd series (427–450)
Due to the lack of the remote control, the second series was not able to run as a pusher/intermediate engine. Therefore, both side corridors were open for access to the machinery and equipment. The locomotives also did not have front doors. The machinery was ventilated by two high blinds on each side. In between were two windows, also on each side.
The mechanical part
Bogies
The bogie frames consist of welded hollow beams. The solid track sweepers are attached to the outer crossbeam. The support for the train signal sensing magnets is located on the inner crossbeam of bogie I. The bogies are also connected to the inner crossbeams with an elastic cross coupling, which facilitates curve entry, smooth running and low track wear. The wheelsets are supported on the bogie by springs with internal silent blocks that dampen horizontal shocks. The wheels are spoked and small diameter to reduce weight.
Propulsion
The torque is transmitted to the drive axles by the motors fixed in the bogie via BBC spring drives, proven on the 1939 built Am 4/4 (later renamed Bm 4/4II) diesel locomotive.
Tensile force transmission
The transmission of the traction and impact forces takes place via pivot pins and swivel sockets from the bogie to the locomotive body.
Locomotive box
The construction and design of the locomotive box were also derived from the Am 4/4. The box is tubular, more rigid and consists of the floor frame, the side walls and parts of the roof. These parts and those for the transmission of tensile and impact forces are made of steel. The rest of the roof and the end walls are made of light metal.
Compressed air system
A two-stage MFO piston compressor supplies the compressed air for the brakes and pneumatic apparatus via the main air tanks and an apparatus air tank. The pantographs are air-operated, along with the high-voltage main switch.
Brakes
The locomotives of the 1st series have an electric, referred to as a regenerative brake, service brake that also allowed the use, for example, on the Gotthard railway, plus an automatic Westinghouse type air brake with a wagon control valve.
The locomotives of the 2nd series do not have electric brakes, which restricted use on some lines. However, like the first series, they had a Westinghouse automatic brake with a car control valve.
The automatic brake is designed in both series as a two-stage, speed-dependent R-brake ("rapid brake"). In addition, the locomotives have a direct brake for braking the locomotive and a mechanical parking brake in both cabs. This acts in each case on the underlying bogie. The locomotives were the first to be equipped with Stopex brake rod adjusters. As a special feature, the brake linkage had to be mechanically "re-attached" when changing the brake blocks.
The electrical part
Main circuit
The lightweight pantographs of type "BBC 350/I", later "BBC 350/II" with spring-loaded rocker, the separator blades, the earthing switch and the high-voltage inlet are the same as in the Ae 4/6 locomotives. However, the transformer and control system were new. Therefore, a departure from the high-voltage control previously used for the Ae 8/14, Ae 4/6 and Ae 4/4 of the BLS was made.
The transformer converts the catenary voltage in separate windings to the traction motor, heating and auxiliary power voltage.
The SAAS jumper control had already proven itself with the Ae 3/5, Ae 3/6III and the Be 4/7. It was now used again in the Re 4/4I in a further improved form.
The two reversing switches establish the connections to the traction motors necessary for driving and braking. The first series locomotives had two positions for driving and braking, while the second series had only two driving positions.
The electric brake of the first series is designed as an excitation motor circuit. The traction motor 1 is fed by an exciter transformer and excites the motors 2–4, which operate as externally excited alternating current generators. These feed the current via the brake choke coil to the low-voltage side of the transformer. From the high-voltage side, the current flows back into the catenary. For the first time, this could be done by turning back the throttle handwheel without using any reversing switches.
The locomotives of the second series had no electric brake.
Motors
The traction motors of the first series are 8-pole and develop an hourly output of 471 kW at 456 V, 1150 A and 1240 revolutions per minute.
The engines of the second series are 10-pole and have an hourly output of 480 kW at 374 V, 1470 A and 1000 revolutions per minute.
Auxiliary power