Electrical Transmission Motor Vehicles.
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Discussion at the Engineering Conference.
On Wednesday morning last, at the first sitting of Section VII (applications of electricity) of the Engineering Con ference, held at the Institution of Civil Engineers, an in teresting discussion followed the reading of Mr. A. A. Campbell Swinton's short introduction to the above subject. The text of this was given in our issue of East week (see page 384) and it was commented upon on page 399 of the same issue. The chair was occupied by Cu]. Crompton, who, apart from his being a recognised authority on heavy motor vehicles, is an electrical engineer and expert of note.
Mr. E. W. Hart, of the Hart-Durtnall Syndicate, who led A. the discussion, stated that he had given attention to this s.ubjeet for some years, rilOre especially to that part which related to large passenger vehicles of the motorbus type. He had experimented with most of the continuous-current ystems, and had come to the conclusion that they were not commercially possible, because of the cost of upkeep of coin-nutators and brushes. He, therefore, combined with Mr. Durtnall, and the results of their labour had been the evolu:ion of a system employing three-phase, alternating-current ;
small exciter was, of course, necessary, but the comnutator for this was such a small unit in the system, that it ;aye no trouble whatever. The electrical transmission was mly used for starting from rest, or when the vehicle was tscending long or steep slopes ; once the machine attained ts normal speed, the drive was a mechanical one, direct, and vithout the employment of any gearing. Mr. Hart made our iinportant claims for the system which he had outlined; hese were :— (1) Power for power, the equipment is lighter. (2) The system is more robust.
(3) It is cheaper.
() It is economical in running. The average result of many trials and demonstrations had hovvn the petrol consumption to be at the rate of one gallon or each 4miles on heavy country roads. Mr. W. T. Steeveris championed the continuous-current ystem, as adopted by him in a bus which is shortly to be ried in actual service, by Thos. Tilling, Ltd. In this system, n inter-polar type of dynamo is driven by a petrol engine, ,d the current is utilised to drive two motors, which are .xed to the side members of the frame, in a position which ermits of their examination, or replacement, without disurbing other parts. The armatures are directly connected
p worm shafts driving worm wheels, which are bolted to he rear road wheels, in place of the usual chain ring. Seriesarallel, or from parallel to series, without first breaking the throttle-valve, operated by a solenoid which is in series Tith the shunt-windings of the dynamo. The controller is
o arranged that it is impossible to change from series to arallel or from parallel to series, without first breaking the lain circuit; freedom from burnt contacts is claimed for his arrangement. A safety device which Mr. Steevens escribed, created some amusement. By means of an inenious switch, which only closes the shunt circuit when the river takes his place on the front seat, the possibility of le vehicle's running away, when the engine is started up, nd the controller is not in the neutral position, is eliminated. The interesting fact that an English four-cylinder engine Wolselev-Siddeley) had given complete satisfaction where merican engines had failed, was elicited from Mr. R. B. lathews, who stated that the General Electric Company of America had been experimenting with the continuous-current system, on buses in New York and in the railway-truck sorting yards at Cleveland and Delaware, with some measure of success.
Mr. Mayor advocated the alternating-current system, and outlined a system which he had recently patented for boat propulsion.
Although English engineers scoffed at the work of Jenkins and others, in Switzerland, twenty years ago, Mr.
W. M. Mordey was of opinion that we owe all we know of the subject, especially regarding single-phase locomotives, to these early experimenters, and referred to a paper on the subject, read by him before the Institution of Civil Engineers, in 1902.
The continuous-current system, as applied by The British Thomson Houston Co., Ltd., of Rugby, was outlined by Mr. Bernard Hopps, who made a strong point of the selfregulating, constant-output dynamo, and the simplicity of control, which, he claimed, was one of the features of the B.T.H. system. Mr. Hopps added that no provision had been made for a direct drive in that system, because of the rare occasions on which, he argued, such a drive could be used with advantage. Records of a run of 260 miles made by this vehicle were submitted to the conference. Our issue of the 13th of this month gave the figures in question, together with the notes of a member of the staff of this journal, who accompanied the bus on the run, and records of a previous long run with the Thomson-Houston bus together with figures, checked by a representative of this journal who accompanied it, will be found on page 249 of our issue of the 9th of May last.
In replying, Mr. Swinton said he did not think that the figures for petrol consumption, given by the various speakers, were of any value, as they were the results of tests on the open thuntry roads, which did not approach the fraffte conditions prevailing in large towns and cities. Weight, another important point, at any rate from the tire point of view, as a question on which this conference had failed to shed much light. Beyond these two items, he did not think there was any real call for a reply from him.
The closing remarks of Col. Crompton were listened to with considerable interest by his audience. The enormous advantages of electrical transmission of power over any mechanical system has been fully demonstrated in many of the large engineering works in this country and in America. It is much more economical ; it is cleaner; it prolongs the life of the machine for which it is used ; and the cost of up-keep is very much less. Col. Crompton asserted that the business of the future depended upon locomotion ; on the railway and the highway. The systems outlined by the speakers gave great promise for the future, but he urged that the electrical engineer must not ask the road engineer to learn electricity ; therefore, any system of electrical transmission on motor vehicles, to be successful, must be as simple as possible. Accumulators may be set aside as of little value; in fact, they are out of the question. He emphatically gave it as his opinion that the system outlined in No. 2 of Mr. Swinton's paper was undoubtedly the best. In that system, the electrical machinery is only used for starting, and at other times when the power of the engine is insufficient to propel the bus on the direct drive, as in the Hart-Durtnall system.