"The Future of Autornobilismi"
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ByGoIonel R. E. Crompton, C.B., RE., Ak.I.Meeh.E., Pres. I. A. E.
On Wednesday of last week, Colonel R. E. Crompton, C.B. R.E., delivered his presidential address before the Members of the Institution of Automobile Engineers, assembled in the theatre of the Institution of Mechanical Engineers, at Storey's Gate, St. James's Park, S.W. The Colonel waived aside all precedent, and, at the close of his address, he invited a full discussion of the points therein raised. " The future of automobilism " sounds a rather comprehensive title, and probably many of the members were somewhat disappointed when they realised that the light commercial vehicles were to be allowed to take care of themselves, and the address dealt only with traction trains, heavy steam wagons, Renard trains, and the formation of the roads over which such vehicles must work. In spite of this limitation, the address and its discussion were received wiLlt interest by all present. We select copious passages :— "I have chosen as my title The Future of Automobilism,' because I feel that the future extension and further success of our great and expanding industry lies chiefly in the development of new fields for the employment of self-propelled vehicles. I allude to the development of the public-service and commercialmotor vehicle, which 1 believe will at no distant date chiefly fill your order sheets. Automobile engineering during its short life has, up to the present, devoted itself chiefly to the development of the rapidly-moving, privately-owned, pleasure carriage, designed to run on the smooth-surfaced roads that already exist in civilised countries. Great lengths of these roads exist in the older countries, notably in England and France, and to a lesser extent in Germany, Italy and America. The smaller extent of good roads in other and less developed countries is a great bar to the extended, use of the pleasure car; as in many countries smooth-metalled roads only exist within the towns or extend a short distance into the surrounding country."
"Is the use of motor vehicles to be confined to the older countries that are already well provided with well-metalled roads, or is it desirable for us to aid in the development of new countries by designing types of vehicles which can run effectively and economically on the weaker and cheaper roads which such countries can afford to construct and maintain? r am one of those who desire to answer this question in the affirmative.
" During the past two or three years, you are aware of the increased attention that has been directed to the making and upkeep of our roads. From the side of automobilism, this question has been viewed from the two standpoints of the maker of the heavy traction engine who demands better foundations, and from that of the maker of the lighter road vehicle who asks for better surface. The road-makers on their side used to tell us that both are costly, and they now state that the idea of improved foundations is too. costly to entertain ; hut they are gradually coming to see that modern methods will enable satisfactory surfaces to be provided at moderate cost to stand the traffic of the light vehicles."
When engineers lay out a railway, they use the technical term " formation " to indicate the work necessary to produce a road-bed on which. the ballast, sleepers and rails are ultimately laid. The lecturer then went on to say We are often told that such and such a road has no foundation, that the metal is laid direct on the 'formation,' and that consequently such a road cannot carry traction engines, motor wagons or similar heavy traffic, although for cars not exceeding two tons in weight such roads offer gOod surface for pleasurable riding, "Can we apply this knowledge to the development of new countries? Is it possible, by following contour lines, to lay out roads with easy gradients, with little cutting and corresponding embankments, and on such contour lines, following the surface of the country, to lay out a road, with little or no foundations, but with a substantial coating of waterproof metalling such as we now know how to construct in all countries where tar and the tar products are available? I believe this question can be answered in the affirmative. it remains to be seen whether we can construct vehicles to run on these roads with weights and stresses so distributed that these cheap roads will stand them, and at a low working cost both of vehicle and road, which will lead to great developments."
After relating some of his early work with heavy traction trains in India, and his later experiences in South Africa, the President gave a typical example of the cost of running a r6-ton traction engine when used for hauling a nett load of 24 tons. He stated that such a train could be worked at a
total cost of id. per nett ton-mile ; this figure was based c an actual experience. Exactly how that figure was evolv( is shown in the table on page 287. Speaking, then, of the effect which such a train migl have on the road, lie said :—
" The vertical and tractive stresses imposed on our road I such a train are not so great as may be supposed, as, by the u of driving wheels 7 feet in diameter by 18 inches wide, tl vertical stresses do not exceed 7501b, per inch of tire width, at the maximum driving stresses can never, even in dry weath under the most favourable conditions, exceed 35 per cent. the vertical stresses, or 2601b. per inch of tire width ; and, wi these stresses, and with reasonable care and intelligent drivin such trains are found in practice to run for long periods ov solidly-constructed roads, causing small wear and tear. But ti average speed must be limited to four miles an hour ; cons quently, the annual mileage cannot exceed 10,000, and f annual nett ton-mileage 120,000; but, as I have said, such trail although their engineering details have been thoroughly wt worked out and the cost of maintenance and depreciation Is been tested by the experience of years, cannot be worked at on cheaply-constructed roads such as we are now contemplatin "The developments in road engineering which have recent taken place, mainly due to the demands of ourselves, the mot engineers, and which have led to a 'better knowledge of ro. construction, of methods by which the material forming the at face of the road can be bound together with waterproof mateth of a tarry or bituminous nature, which prevent the washi. away of the fine materials of the road in wet weather and t same fine material blowing away in the form of dust in the d weather, show us that we can now bind the metalling of the ro together in such a manner that when carrying moderate loax probably not exceeding 5001b. per inch of tire width, and, wi tractive stresses not exceeding half this amount, we can, its t majority of cases, form a cheap and serviceable road by layi such an improved road metalling direct on the natural surface the ground, provided we can make reasonable arrangements 1 cross drainage and for obtaining suitable gradients for ascends or descending hills, or for crossing ravines, watercourses a rivers."
Cheap Roads.
"It seems quite reasonable to suppose that road engine could design such light roads, having a metalled surface, 12 ft wide, of ample strength to carry the above stresses, with 14 bridges to carry axle-weights not exceeding four tons, with ferr: for taking the trains across large rivers, for a cost not exceedi £2,000 a mile. I propose, therefore, voluntarily to impose on the limitations of axle-weight and road stresses which 1 ha above indicated as allowable on these light roads. The or existing vehicles which approach the conditions are the lig six-ton tractors drawing two of more wagons, and the Rena train, which has been recently introduced, and which offers o possible solution of the problem, "'We are indebted to Colonel Renard, and those who ha followed him, for showing es that six-wheeled vehicles design to carry loads equally distributed over their three axles can accurately steered. I have noticed that, with wagons carryi six tons, running at ten miles an hour on steel-tired wheels 3 fi in diameter, the riding is far smoother than with four wheels the same diameter running at six miles an hour, and, as far a: could observe, the damage done to the roads by the six-wheel vehicles is very largely reduced, but at present I have no ace' ate measure of this.
"Next we must consider the horizontal stresses put on t road metal by the action of the driving wheels. We know VE little as to the safe limit of these stresses, but there is little f€ that damage will be done to the roads, provided that the drivi stresses are not in excess of 280Ib. per inch of tire width, a as I shall show, it is quite easy to keep these stresses well willthis limit when six-wheeled vehicles are used, the drivi stresses being imparted through one axle only. "In traction-engine practice, which we have been just now cc sidering, the driving stresses occasionally reach 3201b. per in of lire width, and, although traction engines are often blare for damage to road surface due to these driving stresses, I thi this is often done unjustly. In these cases it is due to oil causes, the road having an exaggerated camber, so that the dr ing wheel cannot bear throughout its full width, and, of cour great damage is done by such wheels, and with such drivi stresses, when the road is in a disintegrated condition riot breaking-up of frost, a condition which we hope will never occ with tar-bound roads.
"If, therefore, we use six-wheeled vehicles we may imagine :hat two men, whose wages amount to ,188 a year, can work a :rain of five of these vehicles, one being the tractor supplying he motive power to its own middle axle loaded to four tons, and to four other middle axles of the. trailer vehicles, all of them nacied to four tons each.
"With driving and supporting wheels 9 inches wide, the ver:ical road stresses would be cut down to 5001b, per inch of tire width ; the tractive pull would be reduced to 1181b. per inch ; he smoothness of running and the absence of vibration, due to :he use of the six wheels, would enable us to increase the speed r.oin the four miles per hour of the heavy traction train to six Mies in this casc, so that, with fixed labour charges per annum, the fuel charges per ton and train-mile would be reduced in pro)ortion to the total reduction in weight of the moving train, and the annual mileage and nett ton mileage would be increased 50 aer cent.
"The heavy traction engines owe much to the boldness of :hose designers who introduced and have for years past suc7.essfully manufactured driving wheels 7 feet in diameter and 18 inches wide. On the other hand, the designers of motor wagons, which have been so largely used for work inside our :owns, have made their designs to afford great facility for easy loading over the side, keeping down their wheel diameters to 3 feet and 3 feet 6 inches as a maximum ; but there is no doubt that these low diameters do greatly increase the shocks, the vibration to surrounding houses, and wear away the road surface far more rapidly than the large diameter wheels of traction mgines, although the latter have axle-weights 50 per cent. greater."
Colonel Crompton here stated that there was a limit, above which any increase in the diameter of the driving wheels would be more than discounted, and that General Morin's world-famous experiments had shown that the gain by increased wheel diameter was somewhat greater than the linear dimension, so far as reducing road and axle friction was concerned, but that the weight of the wheel increased in proportion to the square of its diameter, and, therefore, that the increased weight soon outweighed any advanfag,es gained by the larger diameter. The Colonel then went on to deal with the question of the proportion of useful load to total load and stated :— "I think there is little doubt that, whereas the total moving toad of a fully-loaded traction train containing 24 tons of nett load is, under existing conditions, 52 tons, with the five vehicles I am suggesting this can be reduced to 48 tons, thereby bringing up the percentage of nett average load to total moving load from 16 per cent. to 50 per cent., or when loaded one way only from 23 per cent, up to 25 per cent.
"The providing of tractors for these trains wilt not be a difficult matter for the skilled designer of internal-combustion engines, whether these horn petrol or the heavier oils. The power required is considerable for the 48-ton train working on a road having an average rolling resistance of 751b. per ton and maximum gradients of 1 in 15; if this gradient is to be climbed at four miles an hour the nett horse-power required is 5.bout 125 at the wheels, and, as it is not likely that the efficiency of the gearing and transmission to the wagons can be made greater than 70 per cent., therefore we shall require about 180 horse-power at the engine. This power can be readily given by engines of the present day, by having six-cylinder, 8I-inch engines at 83-inch stroke. It can also be readily given with the SerpolIet form of steam tractor; but in this case extended experience is required as to the form of the generator when we am using solid fuel. Encouraging accounts come to us front Germany of the successful working of steam tractors using instan taneous generators worked by solid fuel ; but, as far as I am aware, none of these as yet have been constructed of higher horse-power than 70, or only about half the size of the engine 1 now propose to use. "We know that the transmission of part of the driving power to the trailer vehicles has been carried out successfully in the Renard train, in the form of direct mechanical connection, but in this work electrical driving of the trailers offers important advantages and offers a very promising field for workers with ideas."
Summary.
"Summarising, it will be seen that I have approached the subject of cheap transportation from the fixed standpoint of cheap roads, which can be worked by lower road stresses, and by using the largest and most powerful trains that can be conveniently and satisfactorily worked by two men, thereby reducing labour and administration charges to the lowest point. "My table is my estimate of the cost per nett ton-mile which I think may be arrived at, my basis of comparison being the ad. per nett ton-mile which, as I have already stated, is a figure which I think will be accepted by traction-engine experts." The subsequent discussion was opened by Mr. Dugald Clerk, who now temporarily occupied the Chair. Mr. Clerk doubted the accuracy of the cylinder dimensions, as given by the author, for an internal-combustion engine, of i8oh.p., and gave it as his opinion that our present knowledge of this type would not warrant the assumption that thesame rules would hold good for a six-cylinder engine whose cylinders are 8.1 inches in diameter as prevail in the design of engines of more modest dimensions. Mr. F. W. Lanchester was of the opinion that a large amount of damage was done to our roads by the severe blows caused by the inertia of those parts of a vehicle which were unsprung, that is to say, parts below the springs. For this statement Mr. Lanchester was given a sly reminder, by the author, that all the Lanchester cars have live axles. This. speaker also thought that there would be some difficulty in finding paying loads for the Renard type of train, and regretted that the small commercial vehicle had been neglected by the author. He asked Colonel Crompton if he knew ofany figures available which would show the maximum stress allowable in our roads.
Mr. Douglas Mackenzie thought that the machine and theroad on which it ran should be considered as one unit, and he outlined the construction of a cheap road for motor traffic. He proposed to dig a fairly deep ditch at each side of the roadway, and then to cover the surface of the alluvial soil with a reasonably-thick coating of waterproof material, in the shape of tar macadam, which would prevent heavy rain from permeating into the soil beneath the crust ; disintegration, caused by frost and the subsequent thaw, could not then. occur, and the bed would settle down into a solid foundation. He also thought that IN, per nett ton-mile was far too. low : he suggested 4d. would be nearer the actual cost. Mr. Henry Lea drew attention to the table, in which, even with paraffin at 3d. per gallon, the cost for fuel cost was double that of coal. Ile would like to know where paraffin could be obtained at 3d. per gallon. Mr. W. G. Gladwell, the road surveyor and engineer of theEton Rural District Council, who had been invited by Colonel Crompton, made an excellent appeal for co-operation between road users and road makers. He asked all those connected with the running of heavy motors to allow a period of 24 hours to elapse before sending their machines on the road after a thaw. This speaker stated that he had experimented with roads somewhat similar to that outlined by Mr. Mackenzie, and was convinced that, with the assistonce and co-operation of road users, waterproof and duStless roads would soon become quite general.
Mr. R. W. A. Brewer spoke very strongly in favour of the need for a more searching investigation of the liquid-fuel question, as most of our Colonies, he said, can produce almost unlimited quantities of such fuel, and can, therefore, use it With great advantage. He was of opinion that the future of automobilism lay with the shopkeeper who would use the motor for general purposes.
Colonel Crompton, in his reply, said that Mr. Lanchester generally managed to hunt up some question which he could not answer. He, himself, would very much like to know
of any figures relating to the stresses allowable in road materials. His reply was short, but pithy, and he reminded his audience that his figures for cost of running traction trains were given to him by an experienced manufacturer. He agreed that liquid fuel was desirable, and was hound to play a prominent part in the future.