The In.fluence of Detail on the Development of the Automobile.
Page 3
Page 4
Page 5
Page 6
If you've noticed an error in this article please click here to report it so we can fix it.
At the opening meeting if the 1911-12 eession of the Estitetien of Automobile Engineers, held at the Institution of Mechanical Engineers, Storey's Gate, S.W., last night, the 11th inst., Mr. L. A. Legros, the new president, gave his inaugural address on "The Influence of Detail on the Development of the Automobile." The real subject of the address was preceded by some comments on the progress of the institution, and an announcement of a new departure in the proceedings of the Institution—the holding of an experimental unreported meeting at which a few technic-al cal subjects could be discussed in less formal manner than that which characterizes the discussions which follow the reading of the usual monthly papers. The following is the text of Mr. Legros's address
" In every class of machinery, no matter how well known it may appear to be, either to those engaged in its manufacture or in its use, there are a large number of details of which mane of the individuals connected with the construction have usually no knowledge, and of which the user frequently has leas, in other words, he believes them to be quite different front what they actually are. From the ignorance of the small boy who thinks the boiler of the locomotive is completely filled with works, to that of the fireman who thinks the discoloration of his gauge cocks is due to the analysis of the metal—having heard that word used and believing it to be one of the ingredients in it.-there are many ether forms of ignorance which have contributed throughout to cause delay in the development and use of every class of machinery, and even at the present time many of these factors are still at work delaying that progress which might. take place more rapidly were greater consideration given to the minotize of machinery.
to examine this subject systematically, we shall find that most detail has its origin in design, but that the design is frequently marred in execution, and that the executed work is subjected to abuse by the user and to wear by the conditions under which it works, and it is from the latter end of the story that the cycle of design must recommence, since it must take account of the possibilities itiyelyed in use and abuse, and of the certainties involved by wear and tear. The subject, of course, is one which does not admit of being dealt with in general terms for all classes of detail, but it is one which it is easy to illustrate by examples. " To take the first example which comes to hand, that of the steering gear, it is well known that the ordinary Ackermania axle affords a fair compromise for obtaining tie intersection of the axis of the front wheels at a point on the axis of the back wheels.
" This gear as usually made is fitted with a number of pin joints, all of which are liable to wear, and as wear proceeds, the two front wheels of the vehicle when it is travelling in an approximately straight line, which, after all, represents by far the greater portion of the distance it runs, will, whether the steering bar be in front of or behind the front axle, take up positions such that the horizontal diameters of the steering wheels would intersect behind the car. After a certain stage of wear has taken place, it is thought necessary to put the wheels in gauge again, and most mechanics, if left to themselves, would set the wheels properly and truly parallel. At this point we should ask ourselves whether this is the right thing to do; whether making things exactly right " is after all the proper course to adopt., and whether the present example is not an illustration of a distinct advantage to be gained by making adjustments incorrectly in the first instance. if the" limit for error in parallelism, determined by experience based on the wear of tyres, is half a degree (or, in the language of the shops, the. wheels should not be more than one-quarter of an inch out of parallel in a length equal to their diameter), and if, when this error has beta readied, it is time to put them right, then why not set them half a degree (or a quarter of an inch) inwards to start with, so that they will start with a negative error no greater than the positive error permissible, and thus double the life will he given to the steering before it becomes necessary to take it up, assuming that want of parallelism is the only reason for the taking up?
" Take another ease: the bearines of an engine are made
atiii fitted ;.io that there is no shake or knock alien the engine is turned round without the ordinary amount of lubricant. Such an engine will run very stiff until its bearings have become sufficiently worn to admit of the proper thicknes.s of
film for supporting the load. Under present conditions, with the limit gauges and more accurate machine tools available, same of these factors are being incorporated in the design, as recorded by the drawing, but there are many factors which still escape and are not recorded, and it is left to the shops to do as their unwritten experience suggests to them may be right. The tendency in the bigger factories is to diminish the amount of responsibility left to the individual worker in respect to the employment of what, for want of a better term, may be termed " shop knowledge," and the reason may be found in the fact that whereas in the earlier days of engineering the same man both constructed and repaired, now, under modern conditions of output, the man who constructs is of a quite different class from the one who repairs, and the two classes are rapidly becoming almost out of touch with each other. Consequently that form of shop knowledge which was of such use to the mechanic of some years ago and which enabled him to put through work on the Imperfect instructions Of not very definite drawings, must to-day be replaced by positive information supplied by the designer and embodied in the detail drawings, figured with limiting dimensions and supplemented by specifications.
"In the broad and general consideration of detail, the first and most important point to be dealt with is that of stanclarriization, and, consequently-, interchangeability. in spite of all the efforts of Whitworth and others in creating standards of size and form for screw threads and for other details, there are still numbers of manufacturers in the country who work almost as though such standards had never existed.
That is to say, there are firms who will make in bolts 1-64th in. large or 1.32nd in. large because the user will get a stronger bolt although he is buying the same size. This will account for the fact that many coach bolts and nuts are not interchangeable. Again, there are numerous makers of screws who claim that their product is within 1-1,000th in. or 1-500th in., as the case may be, but the accuracy of which does not run beyond the written or verbal statement, the actual bolts or screws having an error many times as great_ The fit of screws between proper limits is quite as important as the accuracy of pitch and of shape of thread. A loosely fitting screw in machinery subjected to so much vibrations as is common with automobile vehicles will ultimately cause waste of time and trouble to the user, if not damage to other parts of the machine, whereas the too tightly fitting screw has its obvious disadvantages.
" Standardization is looked after by committees who formulate very excellent rules which should be followed by tho manufacturer, but in many cases there is a want of uniformity in the resulting product which calls for better inspection at the start of operations and for the checking of the gauges to which the work is made. The admirable work now being dune by the National Physical Laboratory in connection with all classes of standardization cannot be overrated; but the importance of the independent checking of commercial standards by such an impartial central authority is not so fully appreciated by matinfacturers as it might be.
" Again, to take an example, the ordinary pneumatie tire is supposed to be interchangeable, that is to say, the same rims will do for any of the tires made by the leading makers. The same pump connection serves for pumping up the inner tube, but it will be found that the Caine uniformity does not apply to the other details which go to make. up the complete tire on its rim. Security bolts, for instance, have various threads, causing the expenditure of much bad language on the road. The diameters of covers are not always in agreement with the rims within the usual limits, with the result that a cover may prove to be tight on the rim and may give considerable trouble in getting it into place. The checking of any of these dimensions is beyond the ordinary purchaser or consumer, besides being outside his province, and the trouble caused by too great deviation from the standard dimensions is only discovered at a time when it gives great inconvenience. The question again is one of the various limiting dimensions tinder normal conditions.
" In the wheels of pleasure vehicles ball bearings have been used for some years with increasing success, but their application was delayed through failures, iii some cases due to overloading, and in many others through imperfect provision being made in the easing of the bearing against the entry of water and mud. In fact, a considerable period of time elapsed before the various causes which contributed to the failure of ball bearings in road wheels were appreciated at their proper values; the several factors of the provision fur taking end thrust, the amount of the permissible radial load, the exclusion of Water and dirt, and of uniformity in the quality of the manufactured ball bearings all tending to complicate the commercial solution of the problem. This matter of wheel bearings is essentially one of design, because the ball bearing, when worn, is, in general, beyond repair, so that the question of prolongation of the life of ball bearings is one which can only be referred back through the repair departments, who effect the renewal, to the designer. The presence of moisture, which has resulted in the failure of ball bearings in the road wheels, has also been found to affect those ball bearings which have beeli fitted to the crank. shafts of sonic engines, and it has been found that a small amount of water in the lubricating oil will cause a sufficient pitting of the surface of the ball races and of the balls to result in premature failure.
" in the engine many improvements in detail have been made, resulting in an enormous advance in respect to silence, speed of revolution, and power for piston area. Apart from such questions as multiplication of the number of cylinders, these improvements, however, have been confined to reduction in the weights of reciprocating parts, alteration of the arrangement and types of valves, modification of the shape of cams and of the size of the cam rollers, care in the selection of the materials and teeth of the gears used for driving the cam shafts, the replacement of low-tension by high-tension magneto ignition, and in general by improvements of detail.
" it is, however, in the carburetter that the main problem of advance in the internal-combustion engine appears at present to lie. Carburetters have been made giving over 50 ton miles per gallon on ordinary touring cars when running at speeds up to 40 miles per hour, and there appears to be no reason why such results should not be easily and regularly obtainable when the carburetter has attained a development as far advanced as that of the high-tension magneto. At present the tuning-up of the carburetter is still frequently .effected by the expensive method of running the car on the road, involving a considerable expenditure of the time of a skilled tester, the wear and tear of the whole machinery of the car, and the wear and tear of the tires, which even if only old tires are used, must be added to the other costs. It is true that on the road the conditions under which the carburetter is working are quite different from those of the testing bench. 'The forward movement of the car may give increased air pressure at the intake of the carburetter ; the vibration of the car may appreciably alter the mean level in the float chamber, and the amount of petrol which flows through the nipple. Usually these matters are adjusted by the tester by varying the size of the orifice in the nipple ; but from an examination of the conditions which lead to the necessity for this adjustment, it would appear that frequently it is the level in the petrol chamber which requires adjusting quite as much as does the size of the orifice, and in but few carburetters is any provision made whereby the tester can set the level of the petrol to the desired height otherwise than by sling down the nipple or adding solder to the float.
" In the clutch there is less complaint than was formerly common ; in fact, the pecul.'arities of leather, cone, and disc clutches have become sufficiently well understood by designers to render this detail one of those which now causes but little difficulty : in the case of metal disci clutches, the difficulties first met with in their use were mainly due to the imperfect knowledge on the part of the user of the proper conditions under which to work them, and, in this case, it is the improvement in the mechanical education of the user that has permitted their continued employment. " In the last few years the question of the reduction of the noise on motor vehicles has been almost entirely dealt with in the engine and gearbox, apart from the change from chain drives to live axles. In the gearbox noise was found to be produced by errors in the shape of the gear teeth, which caused irregularity in the velocity of the driven shaft, accompanied by separation of the driving surfaces at speeds beyond a certain minimum. The improvements in gears have entirely been improvements in detail ; the involute form of tooth has been retained, and the angle of inclination to the tangent of the path of the point of contact has seldom been •
varied ; on the other hand, not only have the cutters been made of greater accuracy than those employed for the construction of other classes of machinery, but methods have been adopted, such as those for developing gears by bobbing, which of themselves produce an approximation to the true form of tooth much more accurate than was obtainable by older methods. Again, the distortion of the gear wheels which may occur in cementing and in case-hardening has been more thoroughly appreciated, and precautione have been taken by manufacturers which have resulted in a much smaller error in the finished product. In the back axle a source of noise has remained in the bevel gears, which, even though made on developing machines, are liable td the introduction of more error than is the case with spur gears. :Niachines have already been devised, and some are obtainable, for correcting the errors in spur and other gears by grinding, and, should it become necessary to run gearing of light weight transmitting large powers at still higher linear speeds, it may be necessary for manufacturers seriously to consider the subject of grinding the bevel gears as well as the spur gears to the final degree of accuracy required. The back-axle difficulty can, of course, be overcome by the use of a properlydesigned worm gear, and here again it is detail of design which fully determines the difference between the unsatisfactory and the satisfactory.
" In the ordinary touring car there is still one detail which looks as though it should be altered before long, and that is the want of alignment between the propeller shafts and the shafts in the gearbox when the car is under its normal load. It would appear that a simple modification should be possible by which the whole length of shaft would be in alignment from the front of the engine to the centre of the back axle When under normal load. At present the chief difficulty appears to lie in the lubrication arrangement for the engine. Now the angle of inclination of the shafting, if it is made lineable, is but small, and is, in fact, much less than that of any of the gradients up which the engine is required to work at full load. If the uniform lubrication of the engine were assured for a larger range of angle, covering the total inclination of the engine to the frame added to that of the maximum gradient to be ascended, this difficulty would disappear. In the case of the transmission on commercial vehicles, the chain has been found far from unsatisfactory, especially since it has been possible to obtain chain cases, which are at the same time simple and sufficiently oil-tight to ensure the chain running continuously in an oil bath. Under such conditions the chain is much more silent, its life is increased to such an extent that the cost of chains as a factor in the running becomes negligible, and chains running in proper oil-tight chain cases can now be guaranteed for a life of over 25,000 miles.
"In the case of public-service vehicles, the improvements made in detail are immediately noticeable on the London streets, where some of the earliest taxicabs are still running side by side with the latest types. In motor-omnibuses the contrast. is still more marked between the old pattern with the chain gear and the new pattern with the bevel drive, and here we have a paradox, for some of the more silent omni. buses, though they have no chains in the transmission from the gearbox to the back axle, yet, have a greater number of chains running at much higher speeds continuously within the gearbox itself. The chain itself, therefore, should not be held to blame for the noise, but the cause should be attributed to the faulty method of application of the chain.
" Provision for wear and tear is now made more ample than it was in the early days of the self-propelled vehicle, when the motor was frequently constructed in the form which may be called the " sandwich " engine. In this a single plane joint divided the upper from the lower half of the casing, with the half bearings contained in each of the respective casing halves, so that when it was required to take up such wear as had taken place, it was necessary, after dismantling the engine, to take a cut over the whole surface of one half of the casing, or else to replace entirely the whole of the brasses in the bearings. This arrangement, which would not have been tolerated for a moment by a constructor with ordinary engineering experience, had, however, une great advantage, and that was that it ensured oil-tightness in the casing. Later, when engine cases were first designed so as to make provision for taking up the wear of the main bearings, difficulties in securing oil-tightness were met with which required to be overcome by various arrangements of detail for preventing the loss of oil, or for ensuring its return to the crank chamber, and, amongst others, in many engines it was found necessary to provide a vent f or the escape of snob gas as leaked into the crank chamber—a provision
eeidom necessary with the. sandwich engine. The provision et this air vent might with advantage he adopted in sonic gearboxee and back axle casings, in which the warming uf the lubricant winch unavoidably takes place when power is heirg transmitted causes sufficient expansiou of the air continued in the casing to force a small quantity or oil continuously along the shafts, and to cause not only wastage, but, in some cases, the unintentional oiling of the brake cur Laces.
"Experience has now determined the amount which should be provided for wear in the brakes; brake surfaces have been increased, and provision has bee made for an ample range of adjustment in the brake gear, lit the earlier designs of automobiles, the designer seluom compared the new or maximum form of the brake shoes or drums with the worn-out or minimum thickness, with the result that frequently it was necessary, when adjusting the brakes, to cut the rods for length and re-thread the ends, or to set the levers in order that the necessary adjustment could be effected.
The Safety of Automobile Traffic.
"The popular denunciation of mechanical traction on account of its alleged danger, usually based on the single factor of its speed, is contradicted very effectively by the figures given in the police statistics for the total number of accidents caused by vehicles which have occurred in the metropolitan area within the last three years for which the returns are available, that is, from 1907 to 1909. During this period the total number of street accidents caused by all classes of vehicles involving injury actually shows a slight decrease, while the population is estimated to have increased by 1.5 per cent. per annum, and the number of automobile vehicles registered has increased by about, 19 per cent, per alumni. Considered on the basis of the population, the accidents per million increased by 50 per cent, in the last six years 0891 to 1897) prior to the advent of the automobile; they attained their maximum in 1907, and have decreased by
i■er Cent in 1908 as compared with 1907, and by nearly 5 per cent. in 1009 as compared with 1907. Accidents, caused by automobile vehicles, excluding those due to the human fallibility of drivers and others, may arise from neglect, from defective material, or from defective design. The elimination of the first of these causes is largely a question of management, and of the responsibility carried thereby ; defective material may be guarded against by proper specification and efficient supervision ; het questions of defective or inadequate design, especially in regard to such vital details as the steering gear and the brakes, call, in certain cases, for examination by an independent body. There are many public vehicles now on the road covering long distances from their base, and though these may have passed the local police inspection and be considered adequately fitted for local conditions, yet outside the area of siperatione of the local authority they may he required to run undet very different conditions of maximum gradient and of road surface. From SOMP of the serious accidents which have eccurred to such vehicles it would appear necessary that the approval of the design and the inspection of these vehicles !neer to their going on the road should be performed by a staff having special technical knowledge. The experience of this staff, as in the case of others appointed to examine into boiler explosions and railway accidents, should be supplemented by an inquiry into the cause of all fatal automobile accidents due to mechanical failure, as in the case of the above-mentioned classes of fatality. These inquiries and inspections should he performed by a department. of the Board iif Trade represented by an expert official.
Accessibility of Parts.
"Accessibility is a question which has had a great influence on the design of the automobile, and, in some instances, may have determined the type which has set the fashion, and fashion in the automobile vehicle plays a more important part than it does in any other class of machinery within my experience. The necessity for frequent access to the, engine, to its ignition gear, to its carburetter, and to its valves has ensured the placing of the engine in the front of the car, where it could be quickly and most easily reached with the minimum of disturbance to the main portions of the vehicle. This fashion in position of the engine is likely to die very hard.
"Accessibility may be divided into two main heads; first, accessibility to those parts which frequently require adjustment requiring no special skill, such as the adjustment of the brakes, of the strength of the clutch spring, of the spark of the ignition devices, and the like, most. ef which have already been dealt with by the designer in arranging them. and second, accessibility to details requiring skilled Mame Lion. In the latter class come the overhauls of engines, gearboxes, axles, etc., and the influence of commercial and publicservice vehicles on this branch of the subject is only now commencing to make itself felt. The importance of being aide to remove parts of a car, unit by unit, that is, engine, gearbox, back axle, etc., has now become recognized by those responsible for the vehicles of public services such as those of the motor-omnibus and cab companies, since the conditileis of working such services are much more closely allied to those of the railway and the tramway than are the core ditions of the private car or the commercial vehicle. The easy removal of these units complete, and their interchangeability with other similar units on the same class of vehicle is a. large factor in economically keeping a fleet of public service vehicles upon the.. road.
"Apart from the two broad questions just mentioned, a third and very important factor is that of accessibility to the various parts by those tools used in making the adjustments. With the necessity for keeping down weight has come the reduction in the size of nuts below those selected by Whitworth for a material the use of which in automobiles only occurs in bodywork—reduction in the size of nuts has been accomputtied by reduction in the width of flanges—the whole of the work has become more cramped and the clearance between the faces of the nut and other adjacent surfaces has been greatly reduced. To put the parts together in the first in mance may require the use of special spanners, owing to the fact that the designer has not laid a scale-tracing of an ordinary spanner on his drawing and ascertained that it can Ire effectively used, that he has riot tried the clearance between the corners of the nut and the adjacent surfaces to ascertain whether a box spanner will overcome the difficulty, or, if so, that he has not allowed for the height of the box spanner. Ignorance of these factors contributes heavily to the repair bill, especially if such inaccessibility is assisted by the super-imposition of small details, and particularly piping, which require removal before the main parts become accessl hie. It these features were considered in design, bolts wonhl often be substituted for studs, long bosses would be cast on parts to enable the nuts or bolt heads to be reached; channels would be milled across faces into which bolt heads could fit to prevent them from turning, and such parts as guardings end covers would be so made that their detachment would he dependent on the very few easily-locked devices.
Factors Which Have Helped Development.
" The existence of the automobile as a practical commercial machine has been shown by others to be largely dependent on materials previously neither readily obtainahle nor extensively used, such as rubber, aluminium and petrol ; the same applies to the steels used in construction, which, though previously known, were not only difficult to obtain in the necessary commercial forms, hut their proper heat treatment was but imperfectly understood owing to lack of research and of experimental aata. 111 the early days of engineering steel was steel, that is to say, there was wrought-iron or cast steel (tool steel), and mild steel is a comparatively recent product. but with the large number of special steels used in the construction of the automobile, it has become difficult to distin• guish by simple tests any one quality from another. Under these circumstances it is necessary that the automobile manufacturer should adopt. a system in his work for marking the different qualities of steel (as by painting them a different colour at one end of each bar, for instance), in order that a store-keeper or other unskilled worker may be able to issue or receive, the proper quality for any detail required.
Fuels.
" Regarding fuel as a storage of energy, we have in petrol nearly 50 per cent, more energy per unit weight than is stored in meal, and, moreover, we have it in a more convenient form, owing to the advantage which a liquid possesses ovel a solid.
" Among so-called improvements may be cited solidified petrol, but it is difficult to imagine what. possible advantage a solid which is troublesome to handle can have over a liquid which can be readily led from its reservoir to its destination through a pipe by gravity, or by pressure if gravity will not suffice.
'Among gaseous fuels, acetylene has been proposed, and though this compound is to some extent endothermic yet it has not a sufficiently high thermal value to render it a competitor of petrol, particularly as it is unsafe when compressed. Ti. gives, however, a wider range of explosive mixture when
mixed with air than the other well-known hydrocarbons, and the mixture of acetylene and air fires at a lower temperature than is the case with other gases. In considering the applications of such gases of high calorific value as acetylene or hydrogen, it is only necessary to make a rough calculation to realize that at present no saving, but, on the other hand, a great increase of weight would Tema were they generated on the vehicle owing to their small weight relatively to that of the compounds used in their production. Moreover, the same applies to the storage of compressed gases, which can only be considered commercially practicable in the ease ef town gas applied to heavy vehicles engaged on runs of but short mileage between fixed charging points.
Lubrication.
In the desire to reduce the weight of the transmission gear, the diameter of shafts in the.early vehicles was reduced to the minimum, and, in order to obtain the requisite area of bearing for carrying the load, the bearings in the gearbox were of necessity made lung. The spring of the shafts under the heavy loads to which they were subjected resulted in bending to such an extent as to reduce the thickness of the oil film locally below that necessary for efficient lubrication, with the result that in many of these earlier cars, difficulties arose in maintaining the bearings in efficient order. This difficulty has been largely overcome by the use of the ball bearing, which, as it takes up less length of the shaft, reduces the effective span between the supports and diminishes the spring. But this is not the only advantage given by the ball bearing; still more important is the fact that it is capable of working saisfactorily with a greater error of alignment than is possible with a plain bearing. The ball bearing working under suitable conditions, and provided it is not overloaded in the first instance, appears capable of running almost indefinitely when immersed in an oil-bath and kept free from small pieces of abraded metal. In fact, in the gearbox, ball bearings generally give less trouble than on other portions of the car. Although the ball bearing has such marked advantages when treated in a suitable manner, yet undcr conditions less favourable, such as those of the read wheels, where a bearing may be called upon to stand excessive and obliquely applied loads, failure is much more easily produced, especially if accelerated by the penetration of water even without dirt, into the bearings as previously mentioned.
Increased Motor Efficiency.
" The improvements in the efficiency of motors have been almost inseparably linked with improvements in carburetters ; nevertheless improvements in the motor itself have to no small degree contributed to the advance in the amount of power obtainable per unit of weight of motor and in the efficiency of the motor itself as a thermodynamic machine. The consumption of fuel per brake-horse-power-hour in the petrol motor has now been reduced to 0.63 lb. Allied to the question of efficiency is the question of obtaining small commercial motors capable of working with a less highly inflammable fuel, such as ordinary paraffin oil. Many attempts have been made to effect this by slight detailed modifications of the engine or of its carburetter, but the problem is one on which mechanical engineers have already spent vast quantities of time and money, the Priestman and the Hornsby-Aeroyd oil engines being examples. The problem has, however been tackled recently in a different manner by a method which combines the carburetter with a gas producer.
" It is well known that if a candle be blown out, the gas which rises from the wick is inflammable, and that a light held some distance above the wick will ignite the mixture of gas and air resulting from the incompleted combustion, and''that the flame will travel down the ascending column of gas, re-igniting the candle. A similar principle underlies the action of the suction gas producer now used on many gas engines.
" A paraffin carburetter has now been produced which resembles a gas producer in so far that aportion of the oil supplied to it is partially burnt, but, unlike the ease of the ordinary producer in which anthracite or other coal is used, a portion of the heat generated in the partial combustion may be utilized to vaporize an excess of the fuel so that a mixture of producer gas enriched with oil vapour can be admitted to the engine. By keeping the percentage of vapour sufficiently low it is possible to avoid the difficulties which occur by the clogging of rings and the deposition of carbon when paraffin oil is used direct in the ordinary petrol engine. " Further hope of using heavier and cruder fuel lies ill the adaptation of the Diesel principle to the ordinary form of
automobile engine. The efficiency of the Diesel engine has now been brought to so high a pitch that engines of 500 h.p. are built with a guaranteed consumption of crude oil as low as 0.42 lb. per brake-horse-power per hour at full load. The Diesel engine, however, as at present constructed, is unduly heavy, and some time must elapse before it has been sufficiently modified to be of suitable weight without having lost the efficiency obtainable in its heavy form. Not only is the Diesel principle in its four-cycle modification a possible rival to the ordinary Otto cycle engine, butthe same may occur with the two-cycle Diesel, to which some considerable amount of attention is being devoted at the present time. Another rival in the field to these engines at some future time will undoubtedly be the internal-combustion turbine. In 1884, in a lecture on turbines given by Professor Unwin before the Institution of Civil Engineers, the difficulty in the way of the construction of a steam turbine was tersely summed up by him in the following words:—
'So soon as we can find a material strong enough and durable enough to stand an excessive speed of that kind (1,000 ft. per second) so soon we may have steam turbines much smaller and cheaper and not less efficient than ordinary steam engines.' " After the successful progress made by the steam turbine, and its development as predicted by Professor T:nwin, it has gone on until it has passed the reciprocating steam engine in economy. A very similar prediction could be made at the present date in regard to the internal-combustion turbine, modified in this respect, however, that temperature as well as velocity are the factors to be considered.
I as orovement s in Transmission.
"Many attempts have been made to obtain transmissions which are either variable in speed or not merely variable in speed, but which also give facilities for storing excess of energy in the motor, and utilizing this stored energy when required. The latter class has been fully dealt with by my predecessor in the Chair, and the former is being developed at the present time by another former president of this Institution on lines which promise immediate fruition.
Improvements in Materials of Construction.
" Not only have steels and aluminium alloys been improved in their ultimate tensile strength and in those other physical qualities necessary for the safe employment of such materials in constructional work, but increased knowledge has been obtained as to the proper treatment which these materials should undergo in order to give the best commercial results. The heat treatment of steels, whether for oil tempering or case-hardening, the proper treatment of aluminium alloys in order that the properties of the original mixture may be retained in the castings, and the diffusion of knowledge of rubber treatment and vulcanizing outside the highly specialized tire factories, are instances in point. There are. however, certain possibilities in the case of steel which ma' yet have to be considered. It. has been found that metallic tantalum has very great hardness and power of resisting wear by abrasion; it is recorded that an attempt to drill a tantalum sheet by means of a diamond drill run at 5,000 revolutions per minute for 72 hours resulted in a penetration of the metal to the extent of millernetre only, and was accompanied by considerable wearing of the diamond tool. Now, if we suppose that the surface of a prepared piece of steel could be treated with tantalum in the same way as it can be treated with carbon in the ordinary case-hardening operation, and that, in fact, it could be superficially coated with a firmly adhesive coating of metallic tantalum, it should he possible to reduce any bearing surface so treated to dimensions hitherto unapproa,ched under the heaviest loading. In other words. whereas the ball bearing may be narrower than the plaint bearing carrying the same load, a bearing dependent for its rubbing surfaces on a material so much harder could be made still narrower, and accompanying the narrowing of the bearings a large reduction in weight could be effected in many instances.
" In concluding this broad and imperfect survey of recent progress and the possibilities of the immediate future, it appears to me that the development of the automobile vehicle for the next decade lies most largely in the hands and heads of the younger members of the profession who are engaged in the design of vehicles and their accessories. Along the lines laid down by their observation and the intelligent conclusions drawn therefrom, the evolution of the vehicle will ir a great measure take place."