The Latest Paper on Motor Omnibuses.*
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With an audience which numbered about too, Mr. E. F. Boult read a paper on " Motor Omnibuses " before the Junior Institution of Engineers, on the evening of the 16th instant. In his preamble, the author stated that the limitations of his subject would not allow full consideration of the three methods of propulsion that had been adopted for the various types of motor omnibus that had been tested in actual service during the past few years, but that he would confine himself to the consideration of a few important features of the petrol-driven machine, which was by far the most popular system for public-service work up to the present time. A quite unusual feature of this paper was the fact that the author had not found it necessary to indulge in a long historical account of the earliest types of road motor vehicles, A few words were devoted to a general statement of the progress that had been made by the various London companies in the adoption of motorbuses, and attention was briefly drawn to some of the types and details which had automatically disappeared as the result of severe testing in public service. The experiment which is being tried by Mr. Frank Searle, chief engineer to the London General Omnibus Company, of combining certain features of the de Dion petrol and Clarkson steam chassis, was, the author calculated, likely to give satisfactory results. The first of a number of headings into which Mr. Boult divided his subject was the driver question, and on this subject he made the following statements : " In places like London, where services are frequent and the distance to the depot never great, men who are merely trained to drive their vehicles are preferred. Such men are more easily obtained, usually more effectively disciplined, and, having no mechanical knowledge, do not attempt to interfere with delicate parts of the machinery, whereby much damao-e might lw done in a very few minutes. In country districts, however, the case is dif ferent. Distances are much greater, and the service very much less frequent, so that it is necessary to employ men who are capable of doing small jobs on the road themselves."
About Big Ends.
On the subject of big-end bearings, Mr. Boult explained that he was by no means in favour of the employment of white-metal linings for these components, and, on this subject, he said : " However suitable white metal may be for other parts, and however hard, it certainly cannot be regarded as a suitable material for these bearings. " It may, however, be regarded as possible to work with white-metal big ends on easy roads, i.e., those where heavy gradients are not encountered, or those where distances are short and rests not long enough to allow the engine completely to cool off, but, on very hilly routes, to use white metal for the big-end bearings is to court disaster. No driver can be found who can be relied on never to let his engine labour,' and more bearings are ' run ' from this cause than from any. other."
On the subject of engine speed, Mr. Book was of opinion that the most.strilcing feature of the motor omnibus engine was its high relative rate of speed, even when compared with the " private motor engine." , " The author considers that the low-speed, long-stroke engine has been insufficiently tried, and that an engine with a normal speed of 700 to 750 revolutions per minute, and a maximum of ',too, with a stroke of six or seven inches, would yield much more satisfactory results, and would prove more Flexible both in starting and in traffic." Mr. Boult also considered that, although the leatherfaced cone clutch had much to recommend it on the score of simplicity, its uncertainty of action under working conditions rendered it unsuitable for employment on motorbuses. On the other hand, although plate clutches were more complicated and costly to run, on the whole he considered their regularity and " springiness " rendered them cheaper and
more satisfactory in the long run. He considered the least efficient part of the modern motorbus to be the arrangements made for cooling the engine, and specially the method of driving the pump and fan.
Final Transmission.
The worm-drive final reduction system for motorbus chassis is evidently favoured by Mr. Boult, and on this subject he ventured the following opinion : " The rack and pinion is doomed, on account of the noise and expense of upkeep, to say nothing of its inefficiency, The worm drive possesses the advantage of silence and smoothness in working; for the propeller shaft general efficiency and reliability may be claimed, and the chain drive is distinguished for simplicity, adaptability, and the fact that chains take up many road shocks which would otherwise find their way through to the gearbox." Although the silent chain had, up to the present, proved by far the most satisfactory system for heavy machines, it
was the author's opinion that many machines will in future be fitted with worm gear or propeller-shaft drives.
Fuel Considerations.
Attention was drawn to the fact that omnibus companies are now using a very much heavier spirit than that with which they commenced operations, and that, although the Paris Omnibus Company, so far back as mo6, was working its Brillie buses on a mixture of benzoic: and alcohol, no practical advance in the adoption of this fuel had been made in England. The author considered that this fuel is likely to be used on a considerable scale in the future, on account of its " greater power," as well as on account of its price. It is to be noted that no justification of the claim thus advanced was offered by Mr. Boult. The aper concluded with a review of the various rates of depredation which users had thought it necessary to adopt during the employment of these heavy machines, and he was of opinion that, for all practical purposes, it would now be found that an annual allowance of te to 16 per cent, would prove sufficient. An attempt was made to predict the type of motorbus which would eventually be evolved, and comparisons were drawn between tramcar transport and services maintained by motor omnibuses.
" The author believes that the traffic of London will, in the course of a few years, be worked on the correspondence system. The two main arteries—East and West --as an example would have double-deck buses of an improved pattern, to seat between 30 and Ise passengers, running between Charing Cross and Aldgale, and Oxford Circus and Liverpool Street, and single-deck compartment vehicles, seating from 14 to 20 passengers, according to the route, working outwards from those points, passengers booking to their destination in the first vehicle entered."
We think it hardly necessary to point out the obvious difficulties which would attend the institution of such a scheme.
The Discussion.
Following the reading of the paper, a number of gentlemen spoke on subjects which had been touched upon previously. Mr. FRANK SEARLE gave eloquent testimony to the assistance that he, as chief engineer of the London General Omnibus Company, had received from the Public-CarriageOffice authorities at Scotland Yard in whatever negotiations he had had to carry through with them. lie drew attention to the fact that costs of operation were rapidly being educed in hig company, and that they were approaching, if rFwy had not already reached, a point at which tlic operation of these machines might be considered a thoroughly sound proposition.
Superintendent A. Bassom discussed the attitude of the police authorities with regard to breakdowns of motorbuses in the streets. Tie also traversed the statements of the reader of the paper with regard to such details as metal-tometal clutches, radiators, silent chains, and final drives. He was firmly of oninion that a lighter machine throughout could be advantageously employed. Mr. B. E. Demme (Kilburn 1 drew attention to the efficiency of the worm-drive type of final-reduction gear, and he hinted at the possibility of considerable opposition to motorbus activity in the shape of the exploitation of redness traction schemes.
Mr. A. H. TYLOR was of opinion that the chief objection
to the motorbus, from the point of view of the public, was the foulness of the exhaust, which was discharged directly beneath the noses of other users of the streets. He was strongly in favour of arrangements being made so that the exhaust might be discharged vertically upwards above the top deck of the vehicle.
Mr. F. J. FIELD asked to be excused from speaking at any length on the paper, as he felt that Mr. Pollard would be able to offer remarks on the same subjects that he had in his mind, from the point of view of one who had had more recent experience of actual running conditions.
Mr. GEORGE POLLARD, M.1.11dechE., expressed himself as not in favour of the steam vehicle, and stated that he had considerable difficulty in deciding exactly which class 01 man formed the best driver. He considered that the driver of to-day, while not possessing highly technical knowledge, should certainly be able to make small and comparatively unimportant adjustments. it was almost impossible to train drivers in the same way that they were trained on railways, although he had at the present time a number of good men coming through his hands as drivers who had received their training as labourers in his workshops. With regard to the high-tension type of magneto for motorbus work, this speaker considered the results attending its employment for commercial motor-vehicle work as disastrous. He did not think it would be easy satisfactorily to supersede the low-tension magneto gear. Gearboxes were not nowadays the source of trouble that they were originally, and he considered that very little attention need be paid at the moment to this unit, when it was possible to point to instances in which gears had been removed after 36,000 miles of running without any undue signs of wear. He thought there was no question but that white metal was the material for the lining of big ends. He considered it would be difficult to better the leather-faced cone clutch as a simple and reliable component, and, although the silent chain had proved its efficiency as a final drive, he thought it probable that a live axle, not necessarily of the worm type, would receive an amount of attention in the near future. With the hundreds of different kinds of carburetter with which he had thought it advisable to experiment, he had come to the conclusion that there was nothing to beat a simple form of float feed.
Mr. DOUGLAS MACKENZIE thought there was very little to beat the geared final drive, provided that means were taken to insure the rigidity of the centres of the gears, and that the rack was kept sufficiently high out of the mud to insure that the gear was working under moderately clean conditions. With regard to the statements which had been made as to the necessary depreciation which should be allowed, he was inclined to suggest the substitution of the term " antiquation," as, with expensive repairs which were now undertaken by operating concerns, the machines were often in a much better state after their overhaul than they had been in their original state. Other speakers were Messrs. J. T. Moon, J. E. Raworth, T. C. Allingham, and S. B. Gook.
The Reply.
Mr. Boult, in his reply, again referred to Mr. Searle's de Dion Clarkson experiment as one which he considered bore promise of excellent results. lie considered that the police authorities had not offered sufficient encouragement to the evolution of a suitable type of single-deck machine, and suggested that a rear platform upon which passengers might stand, and if they so desired might smoke, would increase the popularity and incidentally the carrying capacity of this small machine, He thought the cost of operation might also be reduced by the employment of a machine which only carried a small number of passengers, and conductors of about 16 years of age.
kVith regard to certain comparisons which had been drawn between motorbuses and tramway services, and since it had been stated that, whilst the majority of motorbus under takings were not ur.cluly prosperous, a number of tramcar systems were earning good dividends, he would point to
the fact that the London United Tramways, whose business had been commenced with horsed vehicles, although it had earned good profits at the commencement of operations, did not do so now. He also pointed to the verysuccessful opposition which had been initiated by the London General Omnibus Company, on the Acton and Ealing route, to the tramcars there.