It Started with a Dream
In America, on 26 July 1897, for one 10 year-old boy a dream came true. He got a brand new train set to play with. This was unusual in those days, since toy trains were rare and expensive but this was no toy. This was a full size train. He was given the controls of the first 6-car multiple-unit electric train to be put together at the General Electric Company’s works in Schenectady, New York and he was allowed to drive the train along the test track in front of the assembled officers and engineers of the Chicago South Side Elevated Railway.
The boy’s name was Desmond Sprague and he was the son of Frank Sprague, who we saw in Part 3 introduced the first successful electric streetcar system in Richmond, Virginia in 1888. Desmond was showing off his electrical engineer father’s new system of multiple unit control, which Dad was trying to sell to the Chicago South Side Elevated. Well, sell it he did. The demonstration was a resounding success (“Hey, it’s so simple, even a kid can drive the train”) and, within twelve months of this demonstration, the whole of the Chicago South Side Elevated system had been converted from steam to electric traction with 120 multiple unit cars (Figure 6). Oh that we could do things like this in such a short time today.
Figure 6: one of the Chicago South Side Elevated Railroad electric cars on test in 1898. This was a multiple unit car operating singly. Other cars were attached as required to make up trains. Sprague himself can be seen second from the left standing behind the motorman. As was standard for many years, American driving positions were in a little cubicle in one corner of the end platform. The rest of the riders were company officials and other assorted hangers on.
Multiple Units
The principle of the multiple unit train was simple. A train could be made up of any number of cars. Each car was equipped with two or more motors mounted on the axles and, like a street car, a controller was provided on each vehicle for the 'motorman'. Additionally, a multi-core cable was was strung along the train and connected to these controllers so that they would all operate under the control of the motorman on the front of the leading vehicle. With this arrangement the train was operating "in multiple".
The arrangement allowed trains of varying lengths to have equal power and turnrounds at terminals were simple. The crew just had to change ends. Trains could be lengthened or shortened during the day by cutting or adding cars as necessary. The idea was an immediate success and quickly spread to other systems, first arriving in London in 1901 on the Central London Railway, now the Central Line of the Underground system.
In later versions of this system, not all trains were made up of motor cars (Figure 7). Some unpowered trailers were sandwiched between motor cars and various combinations were made up but the principal of the remote control of cars from one position remained the same.
Figure 7: A diagram of a terminal on an urban metro syste (Central London Railway) showing the arrangement of multiple unit traction. It shows a six car train with a motor car at each end containing the traction equipment and driving cab. Because of the small size of the London tube blinds, the early trains built for the system had some of their equipment above the floor. Normally, multiple unit trains built to the original Sprague concept had all the equipment below the floor or under the seats.
Sprague’s conversion of the Chicago South Side Elevated Railroad to electric traction was not without its troubles. During the early months of 1898, while the newly converted trains were being delivered and tested, one of the cars caught fire. It was quickly found that the cause was electrical and that a large batch of the resistor grids were defective. Seventeen of the 20 cars by then delivered had to be taken out of service that day. Suffice to say, teething troubles with new rolling stock are not unique to modern times.
Main Line Reaction
Although urban railway systems quickly adopted multiple unit electric trains, mainline railways were slow to react. This was understandable. Electrification was (and still is) expensive and mainline railways would have to do it over long distances and they would have to convert large fleets of trains. They were already invested deeply in steam locomotive technology and conversion didn't make commercial sense unless the railway was very densely used. Even the improved terminal operations of electric railways weren't enough to convince most mainline railways to get into wholesale electrification.
In Part 5, we look at how it took until the late 20th century for main line railways to fully realise the benefits of metro operational techniques.
No comments:
Post a Comment