Accumulator Propulsion.
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It is not inappropriate, in view of the approaching introduction of accumulator-driven omnibuses upon the streets of London, that we should examine the grounds upon which this type of vehicle is, generally, af least as regards its prospects of financial success, condemned. The majority of hasty critics assert that the cost of energy and of battery maintenance must be prohibitive, and a few of the more zealous have assumed, on the basis of the dissimilar conditions which obtain with electric broughams, that the expenditure under the foregoing heads will reach as much as Is. 6d. per mile. At least two fundamental differences have been overlooked by those who are ready to damn again, because failure has been recorded elsewhere : they ignore, in comparison with cabs or private carriages, the essential point of regulated control, which, though impossible of attainment where the personal caprice of owners or hirers has to be obeyed, is feasible with stage carriages; and they presume that other than comparatively level routes will be served. We hold no brief for the Electrobus Company, whose methods We criticised, freely, on the occasion of its promotion at the end of April last, but we assert, from a knowledge of what has been achieved in New York with heave accumulator-driven freight trucks, that the prospects for this method of applying power are not by any means, so discouraging as many have laboured to demonstrate. Sufficient information, in respect of the intentions and personnel of the company named above, is not in our possession to enable us to say that its operations will be successful we do, however, say that, having regard to the assured popularity of its omnibuses on the score of quietness and smooth running, there is no reason why it should fail I If it can be taken for granted that the directors intend to make a sincere effort to conduct the undertaking on sound business lines, and to obtain the services of a competent electrical engineer, of proved ability and administrative capa city, there is nothing, on the purely electrical or mechanical side, which need spell disaster. One hears and reads of calculations anent the damage that is done to the cells and commutators by reason of a supposed 700 cases of re-starting per day. But, who has known of a motorbus which stopped so often? No system of transmission allows of deliberate " crawling " so well as one which is electrical, and it is a mere idle speculation to make such estimates. Rather, let us turn, on the invitation of our tramway friends to the records of accumulator-driven tramcars at Berlin, Hanover, Carlsruhe and Dresden. Here, so they tell us, and not without every indication of triumph, accumulator propulsion was, :ifter its being given " every chance," decently interred " years ago." We were, recently, in a position to accept the challenge to take these instances as test cases, and the results of our investigations are appended.
An official, who was personally acquainted with the Berlin and Hanover experiences, in answer to a query as to why accumulator propulsion was abandoned, gave the conclusive reply : " because the cells were absolutely worthless." So they proved, we admit, in comparison with the alternative of the overhead trolley and current from a central generating station : but our concern is to review the ascertained costs of energy in relation to those BOW debited against an independent and self-propelled motorbus inLondon. Hanover, between the years 1895 and tool, had over 15o accumulatordriven tramcars on its streets : the complete battery in each ear weighed 45cwt., and there were 208 Hagen cells, each of 25 ampere-hour capacity on a one-hour discharge, in each battery, whilst the cells were charged, from the overhead cable, which was sanctioned in certain parts of the city, as occasion allowed. Each car weighed four tons, exclusive of any stores, and carried 32 passengers. The total weight, therefore, when fully loaded, inclusive of driver and conductor, was about nine tons. Taking a mean of the results obtained in Hanover, Berlin (102 cars), Dresden (116 cars) and Carlsruhe (27 cars), we find that, over a term of years, the cost per car mile of accumulator-driven cars, inclusive of maintenance of the complete cells and their casings, was less than 1.2d. If we add the cost of current, a total charge of 3.5d. per car mile for energy was obtained, and this had to be compared with only 1,6d. for corresponding supplies, from a central generating station, by means of the overhead trolley. Careful enquiry into the conditions under which accumulators were used in Germany for tramcar propulsion satisfies us that it should be possible to opersite the lighter London motorbus at but little greater cost. The German results proved that battery maintenance could, with care, be kept as low as 0.5d. per car mile (Hanover), although the Berlin figures, for some years, came out as high as 1.6d. It must not be overlooked that the cells in these German vehicles were charged, while the cars were On sections of the line where overhead equipment existed, and that they were, consequently, undisturbed. They suffered, on the other hand, from excessive discharge rates, and the charging periods were, entirely, in the hands of the drivers, who may, or may not, always have obeyed the instruction " auf ladung " (i.e., with the battery switched to the cable). Further, there was no protection against undue
variation in the voltage carried by the overhead cable, from which the charging current was derived,with disastrous effect upon the capacity and life of the cells. Yet, notwithstanding these defects in the systems, the average cost of energy was, in more than one town, as low as 3d. per car mile, and that with the frequent addition of trailer cars. With proper treatment for the batteries, in the absence of attempts to serve hilly routes, and with every prospect of preferential support from the public, accumulator-driven. moterbuses have a fair prospect of financial sucoess in London.
Petrol-electric Transmission.
It is some six months* since this journal prophesied a contest between hydraulic and electric transmissions, and it was in our issue of July 19th last that an illustrated description of the Hart-Duro-mil system appeared. The interval has witnessed the anticipated development of the controversy between the advocates of several alternative methods for the banishment of ordinary step gears, and all these activities are tending to bring neater the day when a box of sliding toothed wheels will be superfluous. It is useless to suggest that either of these generic competitors for favour will be able to enthral motor engineers to the exclusion of the other, whilst it is obvious that, although relatively few new sets of purely stepgears may be constructed and sold two years hence, several thousand commercial vehicles, for passenger and goods purposes, will continue to beat out their internal economies .unconverted. We must waken up to the fact, none the less, that the exigencies of business will enable the automatic, or semi-automatic, variable-speed device to oust: the earlier types whose manipulation calls for more thee average rare from the driver. It does, therefore, behove each individual motor manufacturer in this country to set aside, as a. duty, whatever time may be necessary to enable him to prepare for changes which promise to assert their desirable character almost immediately.
The paper by Messrs. Hart and Durtnall, which is published at length (in following papes of this issue, appears at a date when-the grounds for our original appreciation of the merits of the authors' system have been perceived in odper quarters. Of the numerous inventions which were described at the Hotel Cecil on Monday evening last, not one possesses the advantages which attach to the application of a polyphase, alternating-current, induction motor, as is now put forward, in combination with a generator having two sets of multi-Pelar windings, with variable excitation. It is quite true that Messrs. Hart and Durtnall have retained a continuous-current dynamo to furnish the variable excitation, and that a failure of this small but important part renders their transmission set, for all practical operating purposes, ineffec
tive, It not inopportune, therefore, having regard to some of the-criticisms which we heard in the lecture room, to examine how far the inventors' own condemnation of continuousecurrent motors can, in fairness to everybody, be held to apply to their own source of excitation.
Sparking and brush troubles appear to have been the bete noir of the; lecturers, and to have suffered their copious anathemas' on. various occasions. Let us ignore, then, the contention of other, electrical engineers, who assert that they are well able. to overcome these admitted difficulties in the way of reliable and economical running with continuouscurrent road vehicles, and let us confine ourselves to the apparent anomaly that the Hart-Durtnall system depends, fundameneally, upon the very continuous current and brushes which are so roundly abused by those who have, for their own purposes, adopted it We find, on examination, that the Hart-Durtnall continuous-current dynamo, which revolves on the main engine and generator shaft, seldom exceeds an output of 1,300 Watts, and that it will stand short-circuiting without damage. 1 here are no large currents ; there is no shunt winding; there is a constant resistance in the generator field, against which the dynamo works; starting efforts and low vehicle speeds have no effect on this, the only, continuous-current dynamo; insufficient brush contact is out of the question ; and all regulatien is done with closed circuits. The criticisms of this small dynamo must, therefore, fall to the ground, whilst, as regards the complete set, we have yet to see a continuous-current dynamotor, even with commutating poles, which could withstand the exacting conditions of public-service work so well as the polyphase, alternating-current combination in question. Now that the Hart-Durtnall transmission has, as part of a standard omnibus chassis, proved its unique qualities of general, and braking, control on the road, we shall look, confidently, for its incorporation in not a few designs, for, we understand, the intention of its proprietors is to issue licenses on most reasonable terms.
Olympia's Attractions.
It is difficult to realise that Olympia, except for the inclusion of motor boats, will be tilled with commercial-motor exhibits six weeks hence. No amount of argument cao serve to send home the growth of the more sedate branch of the industry, so well as the rapid changes which have, during the past three years, marked the attitude of the Society of Motor Manufacturers and Traders. Dismal and coid were the draughty " cellars " in which, at the Society's last Crystal Palace Show, we imperfectly discerned a few vans, lorries and tractors ; these had, partly from want of proper accommodation, and, partly, as the result of inappreciation, been put, to all intents and purposes, out of sight, and out of mind ! How different from to-day's position?
That we are referring to a date precisely three years ago is scarcely conceivable, yet such is the case, and the Society's steady efforts to free itself from the reproach of those days have, after a commendably short interval, been rewarded beyond even the expectations of Mr. H. G. Burford. No longer will utility motors be allotted odd and darksome corners, as in 1904 : they are to occupy the whole floor of the main hall, and to overflow into the northern extension. A real treat is, therefore, in store for all who follow the progress of commercial motoring, because they may, without question, look forward to an unprecedented opportunity for scrutiny and comparison. The display of machines will, too, be enhanced by the exhibition of valuable testimonials from satisfied users in all parts of the world, and the combined evidences of advancement should prove irresistible.
The greatest attraction of the show, to our mind, will be the comparative absence of bustle and mere idle thronging by curious members of the public. Divorced from proximity to any private cars, the vans and lorries will not possess sufficient fascination to attract other than visitors who are upon business intent. There will be no crushing in the passage-ways, no queues outside the restaurants, no hopeless jumble of vacuous sightseers with intending purchasers, and no enervating atmosphere : in fact, the place will not be like a motor show at all! A limited attendance of bona-fide interested men, of whom more than 90 per cent. mean to trade, if they see what they require, will replace the ordinary crowd of people, motley and nondescript in the heavyvehicle maker's view, who have eyed, with aimless mien, the splendid points of the commercial motors on all previous occasions! The eternal feminine will, largely, give place to business, and the 175 exhibitors will have to put the briskness of their enquiries and sales against the spectacular and intellectual dulness caused by this temporary deprivation.