MILW class EP-2
| MILW class EP-2 | |
|---|---|
 |
|
| Numbering: | 10250-10254 E-1-E-5 |
| Number: | 5 |
| Manufacturer: | ALCO , General Electric |
| Year of construction (s): | 1919-1920 |
| Retirement: | 1961 |
| Axis formula : | ((1Bo) Do ') (Do' (Bo1)) |
| Gauge : | 1435 mm ( standard gauge ) |
| Length over coupling: | 23,165 mm |
| Service mass: | 236 t |
| Friction mass: | 208 t |
| Wheel set mass : | 17.3 t |
| Top speed: | 113 km / h |
| Continuous output : | 2300 kW |
| Starting tractive effort: | 549 kN |
| Hourly traction: | 516 kN |
| Driving wheel diameter: | 1117 mm |
| Impeller diameter: | 914 mm |
| Power system : | 3000 V DC |
| Power transmission: | Overhead line |
| Number of traction motors: | 12 |
| Drive: | Direct drive |
| Train brake: | Air brake |
| Train heating: | Steam generator |
The EP-2 "Bi-Polar" class of the Chicago, Milwaukee, St. Paul and Pacific Railroad ( Milwaukee Road ) is an electric locomotive developed by ALCO and General Electric for passenger traffic in the Cascade Mountains . Five vehicles were built in 1919 and 1920. They were initially given the track numbers 10250 to 10254 and were later redrawn as E-1 to E-5. In the 40 years of their service they have been a trademark for Milwaukee Road and set a milestone in the history of electric drive systems for rail vehicles .
construction
The locomotives with 12 drive axles and two running axles are unique in their design. The axle order is given in American notation with 1B + D + D + B1, in European notation 1'Bo '+ Do' + Do '+ Bo'1'. This means that the locomotive has a running gear made up of four articulated frames that also transmit the tensile and impact forces. At the ends of the locomotive there is a frame with one running axle and two driving axles , which is also provided with the coupling , inside are the two frames with four driving axles each.
The locomotive body, which does not transmit any longitudinal forces, consists of three parts. The two end parts with the characteristic barrel-shaped structure are firmly connected to the respective four-axis frame below and are supported on the end frame via sliding parts. The short middle section, reminiscent of the European crocodile locomotives , is carried by the two end sections and is therefore not directly connected to chassis parts. In the middle part is the steam boiler for the train heating; the electrical equipment of the locomotives operated with 3000 V direct current is housed under the round hoods. This marked the departure from the box-shaped boxcab design that characterized the predecessor series EP-1 , which was only two to four years older . Milwaukee Road was the only North American railroad company to which General Electric delivered this type of articulated locomotive .
The real specialty of the EP-2 is the simple design of the motors. On the axis of each of the sprung driving wheelsets which is the rotor of a DC motor mounted, while the windings of the respective stator fixedly mounted on the locomotive frame in front of and behind the respective axis, and could be executed thus only two poles, of which also the naming Bi-Polar derived.
In contrast to the other drives common at the time, this variant used neither reduction gears nor rods to transmit the drive forces, which is why the locomotives were barely audible up to a speed of approx. 15 km / h compared with other designs of the time. Only then did the motors start to hum. The top speed was officially around 113 km / h (70 mph) - but it could go up to 130 km / h.
The disadvantage was the poor efficiency due to the large air gap required due to the wheelset suspension , as well as the unfavorable two-pole motor design with low speed, which is why 12 driven axles were necessary for the power, which had the low axle load of 17.3 tons by American standards. Except for the EP-2 of the Milwaukee, this type of drive was only used in the S-class locomotives of the New York Central Railroad .
commitment
When the locomotives, each costing $ 200,000, were used on the Coast Division, they were quickly adopted for marketing purposes, especially for the Olympian parade train, thanks to their modern and unique design . In a publicly effective “ tug of war ”, an EP-2 was allowed to display its power on a truss bridge opposite two steam locomotives - a mallet ((1'C) C1 ') and a consolidation (1'D). In a brief trial run on the Mountain Division further to the east, it was found that the locomotives were cheaper to run than the EP-1 and EP-3 series locomotives used in parallel at the time . In the regular passenger train service between Tacoma and Othello , compared to the use of steam locomotives, operational stops on the way could be dispensed with and the journey could take place on incline sections without double covering.
From 1952 the locomotives were modernized for $ 40,000 each. Among other things, they received multiple controls . The ends of the stems were also rounded off, which made the locomotives look more modern. The renovation by the workshops on Milwaukee Road, which were inexperienced with electric locomotives, led to more electrical fires and operational disruptions. From mid-1957, the locomotives were relocated from the Coast Division to the Mountain Division and gradually decommissioned from 1958. In 1960 they were all shut down. One locomotive (the E-2, former 10251) is on display in the National Museum of Transportation in St. Louis , the others have been scrapped.
literature
- Noel T. Holley: The Milwaukee Electrics . Hundman Publishing, Edmonds WA 1999.
- Brian Hollingworth, Arthur Cook: Handbook of Locomotives . Slamander / Birkhäuser / Manfred Pawlak Verlag, 1990, ISBN 3-88199-688-5 .
- William D. Middleton: When the Steam Railroads Electrified . Kalmbach Publishing Company, Milwaukee (Wisconsin) 1974.
- Paul T. Warner: Locomotives of the Milwaukee Road . In: Southern California Chapter, Railway and Locomotive Historical Society (Eds.): Pacific Railway Journal . 2, No. 6, June 1958, pp. 3-55.
Web links
- Picture of the received E-2 with description
- Milwaukee Road electric locomotives. ( Memento of February 6, 2009 in the Internet Archive )
