PROGRESS IN BATTERY ELECTRIC "VEHICLES.
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Showing Individuality of Design, the British Production has Open to it a Field of Endeavour which is Well Worthy of Greater Cultivation.
. By Raymond J. Mitchell, M.LE.E, MIMech.E., M.LA.E., Etc.
IN SPITE of the considerable patience and generosity of editors of the technical Press, the accumulator electric vehicle still remains unnecessarily mysterious to a large number of business men and others who ought to be au fait with its exclasive advantages and claims to the attention of transport users. In adopting this state of mind, whether deliberately or subconsciously, the commercial community deprive themselves of the use of a machine possessing unique advantages in its own field, whilst, at the same time, the rate of progress of an industry which has displayed a large amount of pluck and endurance is delayed greatly in its legitimate development. The remarkable activity in the American electric vehicle industry during the post-war period appears likely.to be paralleled by a similar degree of interest on the Continent, and more particularly in France (as recently reviewed in The Commercial Motsr), and it therefore behoves those responsible in the British Isles to neglect no legitimate effort to bring to fruition the far more extensive employment of accumulator road traction, which the writer, amongst other engineers, feels is long overdue. In spite of the smashing blow atthe heavy vehicle industily with which the Government rewarded its enormous war-time exertions, the electric vehicle section has maintained, proportionately to its size, a somewhat remarkable degree of life, and not a single firm has been completely swamped in the slump.
Reviewing the design practice of British electric vehicle makers discloses a surprising degree of originality in a type of vehicle where, off-hand, one would have expected that the scope for such would be little or negligible, either as regards battery location, transmission layout • or the use of single or multiple motor drive. The alternatives seem to have been ex plored thoroughly. , The charge has often been made that commercial electric vehicle design appears to have been in the hands of cart builders turned en gineer; hence the alleged crudeness of some of the designs met with in pre-war times. It must not be forgotten, however, that, although some of the vehicles in question looked crude, they worked with surprising reliability, and in numerous cases are still running on rough -American roads after 15 and up to 18 years' service. British designers have not followed the single motor countershaft-cum-roller chain-driven layout, but have developed the two-motor type of vehicle to . a high degree of efficiency. Electricars, Ltd., use a first reduction by, internal spur gear, final trans mission being effected through cardan shafts univer sally jointed and driving on to separate enclosed bevel gear on the rear wheels. Newton Brothers, of Derby, use two motors with their axes parallel to the rear axle, and driving each wheel independently through straight-cut spur, pinions engaging with internal gear rings. This is a very simple transmjssion. and, although the motors are unsprung, tfiis D30
Mr. Raymond J. Mitchell,
fact is of little signifiazice at the moderate road speeds required.
The Ransome electric also employs two-motor transmission, the first stage of the reduction being i by helical gears running n oil, and the final drive by open roller chains. Several makers use the singlemotor drive, with first reduction lay enclosed countershaft and final chain drive. Clayton Wagons, Ltd., use spur gear first reduction, whilst R. Garrett and Sons, Ltd., and the General Vehicle Co., Ltd., prefer silent chain for this application.
An altogether different transmission is the Walker, in which a motor unit and rear-axle casing are combined, the final drive taking place through two central pinions meshing each with a pair of idler wheels, geared in turn to internal spur rings inside the wheels, and of the largest diameter which can be therein accommodated.
Worm and spiral-bevel transmission have also been tried, both used directly and in combination with a first reduction by either Morse chain or spur gear. From his own experience the writer affirms without hesitation that future design practice in this field will favour the straight worm gear of the D.B.S. type, as this type of gear lends itself to a wide choice of ratios, and thanks to the accuracy of its manufacture and the improved knowledge generally surrounding its applications, has been proved to be a thoroughly trustworthy and efficient form of transmission capable of withstanding heavy overloads, perfectly silent, reasonably cheap in first cost and durable. The writer's opinion is evidently shared by Messrs. Garrett, who have already placed on the market a 30-cwt. worm-driven electric chassis, and have decided on the same type of transmission for their 5-ton model.
The transmission problem is worthy of close attention, as it is possible for the energyabsorbed per gross ton-mile on the same hard level road to vary from 80 watt-hours per gross ton-mile for a normal vehicle up to nearly double this amount where the transmission is not suitably designed. Almost needless to say, ball or roller bearings arc indispensable on hubs and elsewhere. The writer prefers the former, owing to their superior wearing properties, and to the fact that they cannot be adjusted," this latter operation being, in his opinion, unsound practice. Two makers—the Electromobile Co. and General Electra-Motives—employ a type of transmission involving separate motor units to each wheel, the required reduction being obtained by a quasi-epicyclic gear totally enclosed. This system is similar to the American C.T. and can be applied as front-wheel drive, rear-wheeldrive or fourwheel drive, thus affording considerable flexibility from a design standpoint, and very economical speed control in the case of four-wheel drive, due to the fact that the motors may be run on full, half or quarter-battery voltage with minimum losses in each case.
The battery equipment, of the British electric
vehicle is usually carried in two compartments, slung wider the frame members and between the two axles, as, for instance, in the Ransomes, Garrett, Newton, Clayton, G.V., Electromobile and General ElectroMotive vehicles. In the Electricars chassis a short bonnet, and the space under the driver's seat are used for battery housing. Much argument has been wasted on the pros and cons, of the alternative conditions, and, providing accessibility be realized, this does not appear to be a vital matter. Speed control is usually effected by means of a plain drum controller, although much diversity in detail design exists. For example, Garretts have a brake interlock with the controller, Ransomes make provision for breaking the circuit on a subsidiary drum, and numerous refinements of this type have been tried, many of which, however, have proved net sufficiently worth fetaining. In general, the control of the electric vehicle is the last item to give trouble, being exceeded in reliability only by the series-wound motors.
Regarding the batteries themselves, the lapse of time now enables positive comparisons to be made between the alkaline type and the lead-sulphuric acid type. The alkaline type has proved itself, beyond doubt, to be much more durable than its competitor, as should be expected from their relative first costs. The lead-sulphuric-acid type is a considerably more lively battery, but requires rather more careful handling than the alkaline type, particularly under the headings of overcharging, electrolyte temperature and over-discharging in emergency. On the whole, each side ma-keg out an excellent case for its commercial existence, and proves its case by selling batteries.
An analysis of transport in any city area reveals a, preponderance of relatively short-journey. " stopand-start " traffic, and this is where electric ,vehicles should be employed. High speed is not required, although rapid acceleration from rest is very important. This feature the electric,possesses supremely, together with such other operative virtues as freedom from smoke and smell, silence, extremely easy control and a high factor of plan-space efficiency • that is, it carries the largest proportion of load' in relation to area occupied. Although electries have been used and are in use in such diverse jobs as stores delivery, coal haulage, railway goods service, refuse collection, brewery distribution, and in London in the wholesale milk trade, yet their use in such cardinal spheres as food and milk delivery has as yet been hardly touched. The bakery trade in particular should also cordially welcome the electric, as it places aftheir disposal a type of vehicle on which really clean and sanitary bodywork can be used and adequately maintained. The electric taxicab represents another undeveloped field, and no teehnical or commercial bar whatever exists to prevent such -cities as 'London, Glasgow, Manchester Liverpool and Birmingham from using accumulator electric taxicabs extensively. The public would undoubtedly patronize such smooth-running, silent, well-sprung and flexible -vehicles as can be made available whenever such enterprising capitalist cares to give the proposal really serious attention. There is moreover, a reasonable certainty of a useful arid wellmaintained dividend for such an enterprise. Many other current uses of the electric vehicle might be cited, but space precludes more detailed reference.
The greatest obstacles to the full development of the accumulator vehicle concern neither batteries nor low mileage per charge, both being, in fact, adequate to ensure a vastly greater development in this field than has yet taken place. The greatest bugbear is the supine attitude of the power-station officials, who, on the whole, have remained passive and indifferent to the accumulator vehicle, and in most cases are not, even to-day, in a position to give more than the most grudging and indifferent charging service, even if they give any at all! This is both regrettable and surprising, since it has been pointed out reneat edly that the potentialities of the vehicle batterycharging business are sufficiently important to warrant the expenditure of at least normal enterprise to secure this business. Moreover, the price charged for electrical energy is, in many cases, unreasonable, and the difficulty of obtaining a charge sufficient to discourage most people who pride themselves in normal efficiency. This means that the flexibility of electric vehicles is much reduced, for, instead of being able to take in an energy supply at many hundred points on, say; the map of London, the number of stations where such service is freely available is fewer than should obtain in a town of 100,000 inhabitants.
Mr. J. P. Kemp has recently filed a patent— No. 181,432 (1921)—for a type of electric vehicle motor which could be used as a, reducer set, thus enabling any electric vehicle to take its charging energy at 220 volts and " convert " it to a voltage round about 110 volts. For this purpose means are provided for disconnecting the motor from the transmission gear, and suitable switch gear is provided for regulation. The use of such a system would enable any garage on a D.C. 440or 220-volt supply to offer charging service at, say, a specially favourable rate for the energy itself, plus a reasonable service charge. Many thousand garages in the United Kingdom could thus help themselves and, at the same time, the electric vehicle. Such a condition would also cause the garage proprietor to take an interest' in the electric vehicle as a definite part of his business.
. Other steps which would help the electric-vehicle industry would be the giving of lectures on this subject as a regular part ofthe routine instruction in. local technical schools, and also the offering of an annual prize by some responsible journal for the best paper' dealing with a means for improving the electric vehicle. This constructive step might have far-reaching results, as also would be the case if some body of engineers within the motor industry would get together and organize yearly trials of commercial electric vehicles under carefully specified conditions,' scientifically controlled and reported by experts.
It should be remembered, above all things, that the electric vehicle is destined to become an extremely important section of the motor industry, and that its commercial and technical advances do not threaten the interests of other branches. For the moment, in fact, the chief mission of the electric vehicle is to abolish the horse, and no engineer can logically oppose this .ambition. The writer trusts that this slight sketch of the field of the electric may, thanks to the authority of The Commercial Motor and to the nature of the facts presented, serve to arouse an increased ,interest in the Cinderella of the motor ,industry.