ELECTRIC LOCOMOTIVES. 735 the Subject of Electric Locomotives Is
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JUXF 1922. 735 ELECTRIC LOCOMOTIVES. - BY SIR VINCENT L. RAVEN, K.B.E., Vice-President. _I_ The subject of electric locomotives is attracting a good deal of attention at present in railway circles and a number of Papers have been written, mainly in the United States and on the Continent, describing various designs which have been worked out for different purposes. Little has been published, however, in England during the last few years, in spite of the fact that a good many new locomotives have been built and put into service for various countries. This is the more to be regretted as England about 100 years ago was the birthplace of the steam locomotive. It is only fitting, theref ore, that English railway engineers should take an active interest in the design of locomotives which, while not superseding the older machine, may now, at all events, be regarded as a definite factor in the future development of British as well as foreign railways. The complete design of an electric locomotive is a combination of mechanical and electrical engineering. The mechanical portions of the locomotive definitely affect the design of the electrical portions and vice versa, and each portion has to be worked out in detail, quite apart from the determination of the general scheme. It is not proposed in this Paper to go into the many detail points of mechanical and electrical design which are, of course, of great interest to many [THET.MEcH.E.] Downloaded from pme.sagepub.com at RMIT University Library on February 27, 2016 736 ELECTRIC LOCOMOTIVES. JUNE 1921. engineers, but rabher to deal with the more general questions of (1) the requirements which any locomotive iiiust be designed for ; (2) the various designs which have been worked out to meet these requirements ; (3) the advantages and disadvantages of the various designs which have been completed. There are broadly three classes into which loconiotives on most railways may be divided according to the nature of the work to be performed or the class of train to be hauled, namely :- 1. Shunting. 2. Freight or goods. 3. Passenger. It is not, of course, practicable to confine any class of locomotive strictly to the duties for which it is primarily designed. For instance, it is very desirable that a passenger locomotive should be able on occasion to haul goods trains, and freight locomotives frequently have to carry out a certain amount of shunting at intermediate stations. In fact one of the most important points to be attended to in considering any design is the question whether the locomotive is well adapted to deal economically and conveniently with two or more different classes of traffic. Naturally, beyond a certain point, such adaptability may cost more than it is worth. How far it is advisable to go in this direction is a matter for individual judgment. This is referred to later. Shunting Locomotives.-Locomotives of this class are required principally for marshalling trains in goods-yards. There is no need for them to be capable of running at high speed. A maximum of 25 miles per hour will be ample. They should, however, be suitable for moving the heaviest trains in use. The tractive power must, of course, be limited by the strength of the standard drawgear, and on the British railways, at all events, this consideration will determine the weight on the drivers. On British railways it is not possible to go much higher than 30,000 Ib. drawbar pull and an adhesive weight of 60 to 65 tons should be sufficient. Compared with steam locomotives usually employed in goods-yards this is a substantial increase. It is, however, a great advantage to have ample weight on the drivers in order to start trains rapidly and thus speed up shunting operations. On other railways, such as those in the United States, where the drawbars can stand much greater pulls, rather more weight on the drivers can be usefully employed. For example, the New York, New Haven and Hartford Railroad uses a number of electric shunting locomotives in their Oak Point, Westchester, Stamford and Harlem River yards. Downloaded from pme.sagepub.com at RMIT University Library on February 27, 2016 JUXE1923. ELECTRIC LoconIorIvEs. 737 These 1ocomot.iveshave a weight. of 714 t,ons all on the drivers. On tho other hand, the Cllioago, Milwaukee and Mt. Paul Railroad has four electric shunting locomotives, weighing 64 tons. For this class of locomotive there is no question of complicating the design by considerations of steady running, adaptability to other classes of traffic, etc. The design should be as simple as possible and, if practicable, the whole weight of the locomotive should be on the driving-wheels. For anything in the neighbourhood of 60 tons it is necessary to divide the weight between four axles, in order not to exceed the permissible axle loading. The simplest arrangement is undoubtedly the doubIe bogie design, each bogie carrying a pair of geared motors. This is from several points of view the most satisfactory ; the construction is cheap, and the maintenance easy, due to the facility with which a bogie can be removed for overhaul or repair of the motors and a spare bogie substituted. The Author sees no reason why this general design should not be regarded as standard for this class of locomotive. The buffers and drawgear may be mounted on the body, and the tractive effort transmitted from the driving-wheels through the bogie centres ; or the drawgear may be fixed to the outer end- frames of the bogies and the inner end-frames connected together by an articulating joint, thus removing all buffing stresses from the body. The North Eastern Railway have had in use on their Quayside line at Newcastle for seventeen years, two shunting locomotives which have given extraordinarily good results. They are of the double bogie type with buffers and drawgear mounted on the body. The following are a few particulars :- Total weight ......55 tons. Length .......38ft. Wheel diameter .....36in. Bogie wheel base .....G ft. 6 in. Distance between bogie centres . 20 ft. 6 in. Number of motors .....4. H.P. per motor .....160. Duty.-The locomotive is capable of hauling a load of 335 tons on the level at 14 m.p.h., and of starting up a gradient of 1in 25 with a trailing load of 166 tons, and of hauling this load up the same gradient at 9.5 m.p.h. These locomotives, of which an outline drawing is shown in Fig. 1, have been in service since 1905, and they have only been in the shops three times for thorough overhaul, Downloaded from pme.sagepub.com at RMIT University Library on February 27, 2016 738 ELECTRIC LOCOMOTIVES. Jcm 1922. FIG.1.-North Eastern Railway. Electric Freight Locomotive. Newcastle Quayside Branch. 0-4 + 4--0 Typc. - N.Y., N.H., and H. R.R. C., M. and St. P. Articulated Double bogie rype of locomotive . bogie not articulated Single phase D.C. System of electrification . .{ 25 cycles Voltage . 11,ooo 3,CjQcJ Drive . Geared quill Straight gear One hour rating :- Tractive effort . lb. 23,200 21,400 Speed . m.p.h. 12.2 11.5 Maximum safe speed - m.p.h. 25 35 Diameter of driving wbeels . G3 in. 40 in. Total weight . tons 714 64 Bogie wheel base . 7 ft. 0 in. 8 ft. 0 in. Distance between bogie centres . 16 ft. 6 in. 21 ft. 4 in. Number of motors . 4 4 H.P. per motor, one hour rating . 150 165 Downloaded from pme.sagepub.com at RMIT University Library on February 27, 2016 JUVR 1922. ELECTRIC LOCOMOTIVES. 739 Their daily duty consists of about fourteen and a half hours shunting work and two hours running wit,h t-rains. Including thc time for preparing, stabling, running to uiid from the shed, their daily service occupies about eighteen hours, and, if required, they could do more. For the whole of the year 1921 the average cost per engine for repairs, inspection, preparing, cleaning, etc., was E103. This figure is rather high, as it included some special repairs to one of the locomotives which would not be required in an ordinary year. It may be compared with the corresponding figure for the steam locomotives doing the same class of work, which, for the year 1921, would be about €610. The particulars of the shunting locomotives on the N.Y., N.H. and H. Railroad and the C., M. and St. P. Railroad mentioned above, are as given at the bottom of page 738. Some particulars of the duty performed by the N.Y., N.H. and H. RR. shunting locomotives have been published recently, from which it would appear that the average daily tonnage dealt with per locomotive at the Oak Point Yard is about 16,000 and the monthly miIeage about 4,500. The locomotives are kept in service twenty-four hours a day and are normally given a light inspection, requiring half a day, after 2,500 miles. A number of these locomotives have worked twenty-four hours a day for t,hirty days without interruption. 3’rere.ight or Goods Locomotit~es.--The conditions which govern the design of freight locomotives vary in different countries, mainIy in respect of the strength of the standard drawgear and the use of power brakes on the goods wagons. On British railways, as already mentioned, it is useless to design a locomotive for more than about 30,000 Ib. tractive effort, whereas in the United States there is no objection to 120,000 Ib. pull.