The Motor Omnibus World.
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Society of Motor Omnibus Engineers : Second Meeting of Second Sessions
Discussion on Dr. Heale.-Shaw's Paper.
THE CHAIRMAN, Mr. E. Shrapnell Smith, lion. Vice-President of the Society, said he had much pleasure in introducing to them a gentleman who scarcely needed any introduction, Dr. Hele-Shaw. (Applause.) He had been asked, first of all, to state that Mr. Coventry was unavoidably detained by an ap pointment with the solicitor to the Great Western Railway,
and, as Mr. Bell had a deputation visiting his garage to make certain investiiations, he was unable to come to their meeting,
and had sent an apology for his absence. Dr. Hele-Shaw, apart from his great scientific reputation, had given a great deal of time to the study of public service vehicles. At the dates when the earlier tests of heavy motorcars were carried out in Lancashire, from 1896 to 1901, Dr. Ifele-Shaw was one of the judges, and he was one of the most energetic workers in supporting those important trials, which did so much, at the time, to stimulate the motor industry in this country. (Hear, hear.) At the conclusion of the paper, which was printed, at length, in our last issue — Mr. GEORGE POLLARD (Deputy Chief Engineer of the London Motor Omnibus Company) said there were many gentlemen pre sent who were more familiar with the ordinary step gear than he was, but, probably, very few of them knew much about the Hall gear. Ile had had considerable experience both in the manufacture and the use of the Hall gear; he would, however, like to touch upon the question of efficiency. It was rather unfortunate, both for the inventor and the invention, that Dr. Hele-Shaw should have tested the Hall gear just when he clel [1901.—ED.1, because it had, since then, been thoroughly overnauled, and many alterations had been made in it ; a vehicle to which it had been fitted was, subsequently, tested by a well known expert on Dashwood Hill, and this gentleman had certified an efficiency of over 70 per cent. That proved that they had considerably improved the gear since it was first tested 1.y Dr. Hele-Shaw. The Hall gear had, also, been tested by Vickers, Sons, and Maxim, and the test was made with the very first gear they constructed. It was tested by Mr. Williamson, iri Messrs. Vickers, Sons, and Maxim's works, at Sheffield, and he was their chief electrical expert. In this case, although the gear had been very roughly used, and was fitted to an old Daimler, which had run, probably, from 5,000 to 10,000 miles, it was found, when taken to Messrs. Vickers, Sons, and Maxim's works, to give an average efficiency of 78 per cent. With regard to wear and tear, some of these Hall gears were taken out of a lorry, which had run 30,000 miles, and were examined by a well-known expert, and it was found that they were perfect. This particular gear had passed, originally, through his bands. and was marked by him, and he was prepared to say that not a single part of that gear had been replaced, and the wear was so infinitesimal that the marks left by the grinding machine were still in evidence. With regard to driving, his experience was that it was one of the most difficult things to teach a driver, or a would-be driver, to change gear properly. In the case of the Hall gear, the driver had only to press a lever forward to go faster, or backward to go slower. The driver could not do any harm, because he could not reverse until he had brought the gear down to the lowest speed, and he could not run the speed up until he had put it in the forward position. Mr. F. S. BENNETT (of the Cadillac Company) said he had been asked to explain the Cadillac gear. This question of gearing was one of the most complicated problems which anyone could tackle. The leading points of this epicyclic gear were : (a) All wheels in mesh continually ; (b) no sliding members ; (c) direct drive on top speed, all gears then revolving to add to the flywheel effect ; (di damage to gears impossible ; (e) no neoessity to release main clutch in changing ; (f) ability to travel 'inch by inch " without jar or shock ; (g) silence in all ratios ; (h) ready means of lubrication ; (i) compactness and small space occupied; (k) only two bearings to align ; (1) all gears operated by foot pedals ; (m) a reverse available for use as a brake ; (n) an internal rack, in order to reduce tooth strains; (e) no high-speed parts ; (p) no loss of headway in changing, as engagement is by instant friction of a band on a drum. As Dr. Hele-Shaw had pointed out, the Cadillac people had been able to get the whole of their change gear in one box. Mr. Bennett proceeded to explain, from two models, the working of the Cadillac gear. To get the three speeds they had only got to add another chain of wheels, or to put another step on one of the planets. As a rule, it was inadvisable to give more than three speeds in epicyclic gear. Mr. BERNARD HUMPHREY (Great Western Railway) said that Dr. Hele-Shaw had stated that it was advisable to keep an evee speed upon country work, and that a large engine was desirable. It it was merely a question of the engine, it would be all advantage simply to open the throttle a little wider and to go up, but there the consumption came in so tremendously that the suggestion seemed, at present, hardly practicable. With reference to variable speed gearing, it had been stated that it was most important that the different transmissions should be efficient. Of course, they ought to be, but that would vary accords ing to the type of work. In town work, they had to get up speed rapidly, and most of the actual work was done on the top gear, but, in the country, they might have to go for considerable distances on the second gear, and, therelore, it was important that the all-round efficiency should remain higher for hilly districts than was the Case in towns. The Hall hydraulic gear had been mentioned, and the efficiency had been given as 92 per cent.; he should have thought the trouble would have been in regard to heating of the oil in pumping, because the oil had to circulate round and round, and, as there must be a certain loss of efficiency, the heat must go somewhere. With regard to air transmission, he did not know whether anybody present had interested themselves in this subject : there was a lot of heat going to waste about a petrol engine, and it was possible, if the air was heated after compression, that something might be done with it. The re-heating of compressed air was the most efficient method of utilising heat that had yet been tried. He had had a run in a car fitted with the Ravenshaw gear, and all they had got to do was to touch a small button, or lever, in order to use it. The only thing was, that, if they changed dawn too hurriedly on the level, the engine acted as a brake. With regard to transmission at right angles, Dr. HeleShaw had almost exhausted all the types, but he had not mentioned the Globoid worm-gear, which had been described in "THE COMMERCIAL MoToe," and for which great efficiency was claimed. As for epicyclic gears, it was rather unfortunate, from the point of view of country work, that they could only be conyeniently made in three speeds. From his own experience, he dould Say that it was necessary to have more than three speeds. He was aware that they could get on with three speeds, but the drop was so great, from one to the other, that it could not he claimed as a success. The efficiency of epicyclic gearing had not been referred to ; he could not say whether it was efficient.
TIIE CHAIRMAN said that, as several references had been made to Messrs. Middleton, Townsend and Ravenshaw's gear, he would like someone to explain it later in the evening. The next name on his list was Mr. Hall, and he should like to ask the representative of that invention a question about the efficiency of 92.7 per cent, which was claimed for it. He should like to know whether that result was obtained with the centres of the two shafts co-axial, or, if not, what degree of reduction was going on between the circulating pumps and the working Or variable-stroke pumps. His recollection of the Hele-Shaw test, was, that the gear did give a fairly high efficiency when the pumps were going round solid, but that, when they were doing an 8 to 1 reduction, the efficiency fell even below the figure mentioned by Dr. Hele-Shaw.
Mr. Hem. (Hall's Hydraulic Transmission Gear) said that, with regard to the efficiency of the Hall gear, the 92.7 per cent. was obtained with the axes of both the shafts c0-axial, and when the gear was at full speed. On his first type of machine, the highest efficiency was obtained when the pumps were working. He might point out that the pumps were working at half speed in. the Vickers-Maxim test. The improvements which had been made in his gearing, recently, had brought the efficiency much more level all through, and, from the tests which had been made, they had attained an efficiency of from 80 to 85 per cent. for average continuous working on the road. In the new machine the efficiency had been increased to about 92 per cent, at full speed. When the machine was working at its slowest, giving maximum torque, the efficiency was about 80 per cent. There was, a course, a certain amount of loss, because, in the new machines, the pumps were very much larger. With others of his machines, very exhaustive tests showed an efficiency in favour of the whole scheme of 90 per cent., which ran down to 80 per cent. at the bottom speed. He was not speaking of new machines, but. those figures had been arrived at by testing machines which had been in use two or three years. With regard to the noise, there was a certain amount of drumming, he admitted, in the early cars, but that was caused because the gearing, instead of being supported on open spiders, was in a drum, and the gear took the air round with it, setting up vibration. That was one reason why he had designed this new machine.
Dr. HELE-Stinw: Then the noise we hear made by your vehicles, which run along Victoria street, is not caused ET this gear?
Mr. HALL said this was not caused by the gear, but the noise was due to the way in which the cars were constructed, and to their having iron-shod wheels. With regard to those vehicles, the fuel consumption of the gears had not increased tor two years: they travelled, twice a day, to Croydon and back, which was a distance of 40 to 50 miles. Their moving weight was from 5 tons to 51 tons, and 7 gallons of petrol was the average consumption, and that result, he thought, was conclusive as to the efficiency of the gear. With regard to heating, he had carried out a kit of tests. He agreed that the oil did heat : he had known it reach 150 degrees, but it did not affect the machine in the least.
Mr. '1'. F. CARTER (Associated Omnibus Company) said he had had considerable experience with various gears, but he thought the time was coming for them to do without gearboxes, lie had heard of several new ideas which were coming to the front, and he was very anxious to see how the HartDurtnali system worked. It had been spoken of very favourably, and he had very great hopes in regard to it Mr. A. H. Aoatis (Adams Manufacturing Company) gave a detailed description of the Adams' epicyclic gear from a diagram. With regard to the pedal gear, it was, probably, quite as important as the epicyclic box itself. The object of the pedal gear (a model of which was exhibited) was to get an interlock system, like that in use in the signal boxes on railways, which made it impossible for the operator to get two points on at one time, or make any mistake in changing the gear. By this invention, no two pedals could be on at the same time. The top speed was obtained by locking the whole mechanism together, and the power went directly through to the other end with no gear moving at all. The locking was obtained by a clutch, which was operated by a single cone. With regard to lubrication, although the box was bathed in oil, it was, clearly, very necessary that the oil should be taken into the internal bearings at all points. Mr. Adams concluded his description of his invention by indicating, with the aid of a large diagram, the working of a small lubricating pump, and showed how the oil circulated so as to secure a continual flow all through the gear.
Mr. Itavggesnaw dealt, somewhat guardedly, with his new magnetic clutch. He said it had only been thought of on June 24th, and the foreign patents were not yet quite complete. About six years ago, he had a good deal of experience in regard to magnetism, and he made a ear which he fitted with magnetic clutches. It was a 611.p. car, weighing about 20ewt. He had travelled over 6,000 miles, using those clutches, and nothing had been done to them. They took about half a watt. They had stood very well, and there was no wear and tear. He might say that Mr. Townsend saw his invention, and they had put their heads together and got out a smaller clutch, which was about 7!. inches in diameter, and 5 inches long, and would transmit 100h.p. at 1,000 revolutions a minute ! T-le thought that was what they wanted. It might be thought somewhat unfortunate that there was a likeness between his name and that of Dr. Hele-Shaw, but he hoped it would not he thought that he had adopted a name like his : he had borne the name of Ravenshaw for many years. (Laughter. i His clutch had been running, in oil, and he had three clutches on the gear shaft : they were all running in mesh, and running very nicely. He would like to go into the question of gears. When he first designed his gear people said, " What enormous gears I' The fact that enormous pressures were brought to bear between the teeth of the wheels seemed to him to be somewhat overlooked. If they took a modern car, they would find that there were many tons pressure from tooth to tooth, on the bottom gear, when they were running the engine between 1,000 and 2,000 revolutions a minute. Under those conditions, how could they expect the car to be silent? They were, now, using for their wheels splendid materials, and they could put a wheel together in a way which nobody thought of doing Len years ago. They put these enormous pressures on the wheels and they worked all right, but they could not help making some noise. The thing he wished most to impress upon them was the fact that they ought to have much larger gears. He had not much knowledge of motorbuses, but he hoped that the hint he had given was one which they would consider worth taking.
Mr, W. P. DI.TRTNALL (The Hart-DurtnaIl Petrol-Electric Transmission) said he was very much interested in the statements which had been made in regard to the high tffic.iency obtained by the Hall gear, but he understood that this efficiency was obtained on the direct drive. He was very interested to learn that a cluteh had been invented, which, t‘:ith four watts, would transmit 100h.p. Ho believed that, whether toothed gears were electrically operated or not, they would still have the noise which was so much objected to in regard to the heavier vehicles. .The result of the Hart-DurinalI system had been to reduce the noise very considerably : they had been able to do this, and, at the same time, to maintain a high efficiency. Mr. Boeescet (The Darracq-Serpollet Omnibus Company)
said that one great advantage of a steam car was that they got an average speed on the level and up hill. He did not know that there was anything else he could say, because the mechanism they were discussingwas not used on the Serpollet cars.
Mr. Mwscoith explained, from a diagram, a new starting gear with clutch control. He said he had had. a great deal to do with industrial work. Upon one occasion he had had to connect up a motor drive to heavy machinery, and he was pulled up by the electric supply company for making too heavy a craft on their lines : he had to satisfy the company, and, at the same tune, to carry out his own ends. The invention he was speaking of contained a Hele-Shaw clutch. He had watched a good many motor omnibuses at work, and it seemed to him that the engine required assisting.
Mr. T. _Mtnetto CAIRNS (Edinburgh) said the discussion he had listened to proved to him that it was no good talking about mechanical gears at all: he had seen the great advantage of the Hart-Durtnall system of transmission. With regard to the Ravenshaw magnetic clutch, he thought it was a thing which would be brought prominently forward. Without going into detail, he might say that 'Mr. Townsend, of Messrs. Middleton and Townsend, Edinburgh, who had applied this system for road motors, had used one in a car, which had been driven from Edinburgh, and was going to do the return journey, with four people and a lot of luggage, upon an up hill and down dale journey, and he thought that plain staternent of fact was worth all the theory they could talk about. They bad, certainly, arrived at a time when it would be advisable for them to direct their energies towards the question of electrical transmission.
Mr. flitowann said that, whilst electrical gearing was maturing, his opinion was that there was nothing to approach the Hall gear, because the gradations of change were absolutely perfect, being infinite in number. However good they might make clutches or any form of epicyclic gear, they would always have their limits. In his opinion the Hall gear was ideal. Ile was not interested in this particular gearing, beyond the fact that he had recently met Mr. Hall, and that he had spent a few weeks mastering the details of his invention when it first appeared. As Dr. Hele-Shaw had pointed out, it was necessary to distinguish, carefully, between the average and the mean efficiency.. In the absence of careful experiments, it would be impossible to say what the average efficiency was, unless they too': all the circumstances and conditions into consideration. They ought to bear in mind that, by this invention, they were passing a certain quantity of oil through a certain number of ports, and turning a certain number of corners, and, therefore, a certain amount of heat must he set up. All that lost friction must appear in heat, and, of course, the oil became heated. The reason that was not fatal to the invention was that the periods during which any high heating took place were extremely small. They might run a heavy lorry up a hill for about four miles, and the oil would get hot, but going down the hill, the oil would get cool. The engine might he running at full speed, but not a single bit of gear would be in action going clown bill, and that gave the oil time to cool. Therefore, there was no great amount of heat to be dissipated, and the heat only occurred for short periods.
THE CHAIRMAN proposed a vote of thanks to the lecturer, and this was warmly accorded.
Dr. HP:LE-SHAW said it was a very great pleasure to have Mr. Shrapuell Smith in the Chair, because he had worked with the Chairman in the days when anybody who had anything to do with automobilism was looked upon in the same light as the inventor of a flying machine was at that time. The light car had arrived, and he believed the heavy car was to come. The change which had taken place, owing to the introduction of the light type of car, was nothing to the change that would take place in industrial operations owing to the introduction of the heavy wagon and the public service vehicle. (Hear, hear.) it was only natural that they should commence with the light car, because the problem was so much easier. When the pneu• nTatic tire was invented, they solved the most difficult part of the problem. The problem to be dealt with now, was the problem of the wheel upon which the public service vehicle rode. They were, that evening, only dealing with one section of the problem, namely, the transmission gear. He thought he had justified his remark when he pointed out what was likely to take place in the near future. Changes had taken place, and inventors had produced one gear after another, and he did not know which exhibited the most mechanical ingenuity. As the old lady said, " Comparisons are onerous," and he would riot attempt to compare the merits of the different types of gear. He did not think they could eliminate the wheel factor from the problem, and they could not, properly, test the efficiency of the machinery only upon the road. They could only test it, properly, on the bench and by electrical methods. He might inform Mr. Pollard that, in the figure he had given for the Hall gearing,, he had not put down the lowest figure, because it was too bad. Fie was quite willing to make the test again, by the same methods, and, as far as scientific accuracy could be obtained, he would make the test accurately. Mr. Humphrey had stated that a large engine had a prohibitive consumption, but
he would remind him that they were, now, in the early stages of the development of automobilism. Who did not believe that, eventually, they would be able to graduate and to arrange ths working of the six-cylinder or eight-cylinder engines so as to get exactly the amount of consumption of fuel for the work required of it? Who believed that even the engine had arrived at its final state of perfection? With every admiration for Mr. Hall's invention, he would point out that there were great possibilties in the motor itself, and they should not overlook that fact, when dealing with the invention of any particular form of gearing as the solution of the problem. There were many other ways in which inventors were approaching this problem, and they would all have to be tested by practical working. He felt proud that he had seen Mr. Raven shaw, and had heard him
speak, because he was a gentleman who had waited for six years, working at his invention, before bringing it out. Mr. Ravenshaw did not rush into print directly he had hit upon an idea, but he was content to work upon it, and to perfect it, and for that he deserved unqualified admiration. If more of that sort of thing took place, inventors would be able, in regard to their particular speciality, to command more capital and public confidence. It was because so many immature schemes had been brought forward, that the public had become so chary of assisting the inventor. It had been said that everything comes to the man who waits, but Lord Beaconsfield said that everything came "to the man who knew how to wait," and that was the secret of success. (Hear, hear.) In conclusion, he desired to thank them for their patient attention. (Applause.)