SBB on 4/6

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SBB Am 4/6 / Ae 4/6 III
Type designation: On the 4/6 Ae 4/6 III
SBB Am 4-6.JPG
Gas turbine locomotive on 4/6
Numbering: 1101 10851
Number: 1
Manufacturer: BBC / SLM BBC / SLM / SBB
Construction year: 1938 (1961)
Retirement: (1954) 1978
Axis formula : (1A) Bo (A1)
Length over buffers: 16,340 mm
Service mass: 92.4 t 80 t
Friction mass: 59 t 57 t
Top speed: 110 km / h
Installed capacity: 1618 kW (2200 hp ) -
Hourly output : 1030 kW (1400 hp ) 1692 kW (2300 hp )
Starting tractive effort: 127 kN 145 kN
Hourly traction: 75 kN at 50 km / h 77 kN at 79 km / h
Drive wheel diameter: 1230 mm
Impeller diameter: 950 mm
Power system : - 15 kV 16.7 Hz AC
25 kV 50 Hz AC
1.5 kV DC
Rated speed: 5200 min -1 -
Power transmission: electric -
Number of traction motors: 4th
Drive: Gas turbine electric
Transmission ratio: 1: 4.53

The Am 4/6 1101 was a gas turbine locomotive of the SBB . It was built by BBC in 1938 and handed over to SBB for trial operation on the non-electrified routes. It was later converted into an electric three-system locomotive and used in the Geneva area from 1961 as the Ae 4/6 III 10851 .

prehistory

In 1938 the BBC built a gas turbine system for a 4000 kW emergency power group for the city of Neuchâtel . To test whether the gas turbine could be used for locomotives , the BBC suggested building a gas turbine locomotive with an output of 2200 hp (1618 kW) and electrical power transmission.

The SBB gave the BBC the opportunity to test the gas turbine in railway operations. The maximum speed was set at 110 km / h. For a six-axle locomotive, it was not possible to install a system with an output of more than 2200 HP (1618 kW), since otherwise the maximum service weight of 92 t with a full fuel tank (5.5 t) would have been exceeded. In this case, the SBB would not only have refused to test, but also to take over the locomotive. On the other hand, the SBB undertook to take over the locomotive in working order. Under the direction of the BBC, the locomotive was built with the help of the SLM for the mechanical part on their own account.

technology

construction

As far as possible, the locomotive was based on tried and tested technology in order not to endanger the project with faults in components that had nothing to do with the gas turbine. Electric power transmission was chosen because the technology had proven itself in interaction with diesel engines . It made it possible to drive any number of axles , which was an important factor due to the high output per weight (compared to steam and diesel locomotives of the time). In addition, comparable hydraulic drives have not been tested in these performance categories (over 400 hp).

The gas turbine consisted of a compressor , a combustion chamber and the turbine itself. The compressor required about 6000 HP to compress the air and then to convey it into the combustion chamber (air pressures between 700 kPa to 2.1 MPa, depending on the speed of the turbine), in which the fuel ( heating oil ) was burned, which led to an expansion of the gases, which in turn hit the turbine at a temperature of 500-600 ° C and developed about 8000 hp there. The exhaust gases then flowed through a heat exchanger that preheated the fresh air before it was expelled through the roof. The remaining approx. 2000 hp could be used to drive the locomotive. The turbine reached a maximum speed of 5200 min −1 , the idling speed was 2800 min −1 . The speed of the generator was reduced to 812 min −1 at full load by a gearbox .

Efficiency

Measurements showed that the efficiency from idling to medium load (1000 hp) increased continuously from 0% to 15%, reached its maximum of 18% at 1700 hp and then fell again to 16% at 2200 hp (all figures without electrical losses ). The efficiency was low compared to diesel technology at the time, which was an important factor in preventing the technology from catching on.

Start of the locomotive

First, an auxiliary diesel engine was started with electricity from a battery . This was connected to an auxiliary generator that generated electricity to start the turbine. This brought the main generator attached to the turbine , which now ran as an electric motor , up to speed. This process lasted about 4 minutes, after which the combustion could be ignited and the turbine drove itself from now on. As the speed continued to increase, the power of the auxiliary diesel engine could be used to move the locomotive at low speed (10 km / h) in front of the train to rank. After a further four minutes, idling speed (430 min −1 on the generator) was reached and the locomotive was ready for operation.

Increase performance

In order to increase the power output of the locomotive, the driver could turn his power controller, which triggered the following process:

  • More fuel was injected
  • The speed controller was set to a higher set speed
  • The overload protection noticed an overload situation (speed below the set speed) and electrically switched off the load from the turbine (!)

Since the load was now lower and more fuel was injected, the speed increased quickly (up to 812 rpm on the generator under full load), and as soon as the target speed was reached, the load was increased again until a new balance between the power output of the turbine and Power consumption of the traction motors was reached.

To lower the load, the same process was done in reverse.

Brakes

In order not to have to use the compressed air brake for braking (wear and tear and risk of overheating), alternative braking systems are advantageous. Since the compressor required up to 6000 hp, it was considered to let the traction motors generate electricity, which in turn was used to drive the turbine, in which the power was converted into heat by the compressor. The fuel supply could be turned off. It is unclear whether the necessary installations were ever made.

Safety measures

If the engine driver increased the power too late (e.g. on an incline instead of before), the engine speed may not increase quickly enough, which resulted in too much fuel being burned and at the same time too little air available to cool the turbine was standing. In such a situation, the overheating of the turbine was indicated to the engine driver with a warning lamp. If he did not respond, the fuel supply was cut off after the temperature rose by 30 ° C.

In the event that the load on the turbine suddenly dropped (e.g. due to blown fuses), a safety device was in place to reduce the air supply. This in turn led to the turbine overheating, which in turn cut off the fuel supply.

If the temperature in the combustion chamber was too low, the controller tried to reignite the turbine; if this did not succeed within 5 seconds, the fuel supply was cut off.

Control logic

The complex control logic was built up entirely in oil circuits. All control inputs such as tachometers, power controllers and others were arranged as valves or pumps in such a way that they appropriately influenced the oil flow and actuators (pistons) performed the necessary control processes.

business

The locomotive was able to take its maiden voyage on September 5, 1941, and has subsequently undertaken test drives and test drives. The trial run had to be interrupted again and again due to the lack of fuel caused by the war. The results of the trial run convinced those responsible, so that the SBB officially took over the locomotive on October 1, 1944.

Because there was no suitable application in Switzerland, the locomotive was loaned to the SNCF from 1945 to 1946 . Before the express trains on the routes from Basel to Strasbourg and to Chaumont, the locomotive provided proof of serviceability. The locomotive was then used again in Switzerland.

From June 20 to November 2, 1950, the Am 4/6 was leased to the DB . She went from Bw Treuchtlingen in rosters of class 01 , who was said to be superior, especially in slopes.

Decommissioning

In 1954 the locomotive was shut down with serious damage. An expensive repair of the turbine was dispensed with. The reasons were the poor efficiency and the lack of non-electrified routes in the SBB rail network .

By this time the gas turbine locomotive had covered 410,000 kilometers. Although the operation was successful, the BBC's hopes of export orders were not fulfilled, apart from the test locomotive 18000 ordered by the GWR and then delivered to the BR . A general introduction of gas turbine locomotives at SBB was never planned.

Conversion to Ae 4/6 III

The gas turbine locomotive was converted from 1958 to 1961 into the electric three-system locomotive Ae 4/6 III 10851. The conversion should bring experience for the construction of the then planned four-stream TEE trains SBB RAe TEE II and strengthen the DC park on the Geneva – La Plaine line, which only consists of the two SBB BDe 4/4 II .

construction

The locomotive received a new box with the same driver's cabs as the SBB Ae 6/6 . The locomotive frame and the bogies together with the DC motors and the gearboxes were taken over from the gas turbine locomotive .

The electrical equipment was mounted on a common carrier similar to the previous gas turbine group, which could be installed and removed through the open roof.

There were two pantographs on the roof . One was used on the SNCF direct current lines (1500 V), the other on the SBB lines (15 kV, 16 2/3 Hz) and the SNCF alternating current lines (25 kV, 50 Hz).

On the SBB network and the SNCF AC network, the current flowed into the transformer , where the voltage was reduced. The alternating current was then converted in a silicon rectifier and fed to the four direct current motors. On the SNCF direct current network, the traction motors were fed directly from the contact wire to the traction motors via four starting resistors .

business

The project planning and the modification took more time than planned. The three-current locomotive could not be delivered until 1961. The four-stream TEE trains were also delivered at the same time, so that the Ae 4/6  III could no longer play its pioneering role. After test drives on French direct and alternating current lines, the locomotive was put into operation.

The three-current locomotive was assigned to the Genève depot and was called "La Tricougny" by the locomotive drivers. She arranged for transfer trains in the Geneva area. At the same time, it served as a reserve vehicle for the Geneva - La Plaine route.

The transformer was replaced by ballast after severe damage in 1976, so that the locomotive could only be used under 1500 V direct current. In the course of time, the Ae 4/6  III was increasingly required as a replacement for defective BDe 4/4 II commuter trains. She carried two light steel cars and a baggage car. In 1978 the failure-prone locomotive was scrapped and broken off.

See also

Individual evidence

  1. ↑ Brown Boveri Werkbild 113762. In: Flickr. ABB, 1961, accessed August 28, 2016 .

Source

  • Hans Schneeberger: The electric and diesel traction vehicles of the SBB, Volume I: years of construction 1904-1955 . Minirex AG, Lucerne; 1995; ISBN 3-907014-07-3
  • Franz Eberhard: SBB gas turbine locomotive Am 4/6 1101 . Loki special No. 13, ISBN 3-85738-059-4
  • Peter Willen: Locomotives in Switzerland, standard gauge traction units . Orell Füssli Verlag, Zurich 1972
  • Keseljevic Christophe: Farewell to the 1500 V direct current system in Geneva . In: Swiss Railway Review . No. 12 . Minirex, 2013, ISSN  1022-7113 , p. 649-650 .

Further literature