PRR FF1

The PRR FF1 was an electric locomotive of the American Railway Company Pennsylvania Railroad. Firstly, as an experimental design and with its compact size, the high electrical power rating, that the enormous attraction and the characteristics of the chassis drive compared to the other railways electric locomotives of their time they took a special position.

Structural features and application

The FF1 was an experimental single design for the planned electrification and freight train operating on the railway line over the Allegheny Mountains between Altoona ( Pennsylvania) and 60 km from Johnstown ( Pennsylvania) procured in 1917 with gradients between 10 ‰ and 20 ‰. With their power levels, it was the strongest in their time electric locomotive.

Landing gear assembly

The machine had two bogies coupled together, each with three driven axles and a drive axle in a common framework. In an overarching common locomotive body was constructed with the electrical machinery, with its construction was taken over with minor changes of the PRR passenger coaches. With reference to the fact that there were two movable carriages under a common main frame, the locomotive was awarded the wheel arrangement ( 1'C ) (C1 ' ). From a U.S. perspective, however, was relevant that the chassis is not each independently rotatably mounted in the main frame for themselves, but were connected to a common central pivot coupling, in which the relative motion of the two drives oriented. With this view, the classification yielded by the U.S. AAR classification in the wheel arrangement 1-C C -1, which, however, would signal a double locomotive of the UIC terminology.

Propulsion

Each suspension had at the outboard end ( Laufachs page ) is a double -engine layout, their rotation was transferred to a jackshaft. This was done with a sort of spring cup drive, ie with attenuation by several spiral steel springs around the circumference of the flanged jackshafts disc. From this in turn a pinion drive was carried out on the three coupled drive axles.

Electric motor operation

The dual-motor pairs were designed as three-phase motors, had to be produced on the locomotive via a converter because of the traction power supply of single phase of 11,000 volts and 25 Hz, the required three- phase alternating current. The engines were designed for a total capacity of 5,618 kilowatts ( 7640 hp ), but the generator was only 2,940 kilowatts ( 4,000 hp ) continuous running or 3,380 kilowatts ( 4,600 hp ) provide as output per hour. All the electric power devices ( transformers, traction motors, electrolyte resistance (see below) and the liquid pumps) were air- cooled by means of separate fans.

Electrical control

By switching the motor groups in two speeds with either 33 km / h ( 20.6 mph ) or 16.5 km / h ( 10.3 mph ) were selected. This was considered sufficient to carry the heavy freight trains on the proposed steep grades of the railway company. In addition to the speed level switching regulation of the Approach to electrolyte resistors for high electrical currents could be made. These consisted of a tank with conductive water, the adjustable fluid level was used for modulation of the motor power and maintaining the tension during the switching phases.

Operation

In the test mode on the already electrified route between Philadelphia and Paoli (Pennsylvania) the "Big Liz " said machine was found, although as in working order, but with their hourly output of 3,680 kilowatts and the starting tractive effort of 620 kN for that time far more than the car of the Company allowed. When pulling locomotive could blow up the clutches and on the other hand suppress individual cars in the middle of the train off the rails in the shift operation.

Comparatively provided the 25 years later built legendary steam locomotive "Big Boy" just 602 kN tensile force and the built in 2000 modern electric freight locomotive DSB EC with a continuous output of 6,500 kW "only" a starting tractive effort of 400 kN, the latter, however, reduced by a weight was due. A similar experience with a high tensile force was also in Switzerland around 1933 with the double locomotive Ae 8/14 - 11852 made ​​in their Zugkraftaussteuerung maximum of 588 kN, the hitches of cars pulled. "Big Liz " was shut down after the test operation and 1940 scrapped.