1908 Motor Show: A Review (2)
MECHANICAL FEATURES FOR 1909.
An Engineer's Impressions at Olympia. (abbreviated).[1]
So much has been written concerning the adoption of Mr. Knight's sleeve valve-motion by the English Daimler and the Belgian Minerva companies, that further comment in this article seems superfluous. A few points in the present method of making this valve-gear may appear somewhat unmechanical to the engineer of experience, but the idea is undoubtedly good.
The motor of the "Dolphin" car, exhibited by the Two-Stroke Engine Co., presents another novelty at the Show. The action is, of course, by no means new, since the Lepape, the Legros, and several other two-cycle engines of more or less recent conception have had pump-fed cylinders. The "Dolphin" is, in many ways, an attractive vehicle, and that attractiveness would, perhaps, have been enhanced if its engine were a vertical one, as the Lepape. Incidentally, the method of rear live axle construction and four brakes taking effect upon the driving wheels are good points about the new car from the sea coast.
A few of the cars on exhibition remind me of more than one American-made automobile. For instance, the two-speeded Sheffield-Simplex — called by some a gearless car, which it obviously is not — has its balance-gear and speed-gear combined in a single case on the hack axle. And the Dennis gearbox, with its free-wheel device, is also similar to that in the cars of an American motor company, who have made this a feature for several years.
There seems little doubt that the unit system of combining the engine, clutch, and change-speed gear is rather catching on here, and the Motobloc firm from Bordeaux may pride themselves upon having early set the example in this respect since the unit plan has, for a considerable time, been favoured in the United States. On the other hand, credit is due to one of our cycle factories, that of the Rover Co., for having long ago adopted this method of construction - a method which has several advantages.
The S. K. Simplex is one of the few newcomers bearing the stamp of practical engineering, which cannot be said for every car. Frankly, I am not smitten with the suspension, but the engine is an especially neat motor. I note the maker’s claim that by combining the change-speed and compensating gears on the trailing- axle weight is put on the driving wheels. This is a sound argument, but, personally, I would prefer to have as little unsprung dead weight as possible. At any rate, the enclosed valve gear and other characteristics of Messrs. Smeddle and Kennedy's engine appeal to one, and will, no doubt, be considered pretty well as attractive as the Maudslay design. And those possessing pretensions to mechanical knowledge o ill see that standardisation and interchangeability has been well considered in this machine.
Messrs. Coltman, the boiler makers of Loughborough, have their 20 h.p. four-cylindered car, a vehicle of the same sort as that on which I had a run last November. In some respects it is not unlike the Crossley, but it seems altogether lighter than the Manchester machine. The Coltman car is interesting as to several parts, and its clutch is one of them. It consists of five iron segment shoes, which are capable of being pressed out by the action of a cone. This is one of the several modern cars fitted with the thermo-syphon system of water circulation, and in this connection the tendency seems to exist to adopt this style in new models. For we now have, among others, the new Humbers, the 15 h.p. Austin, the 14 h.p. Siddeley, and the 18 h.p. B.S.A. with this system. And most of the makers, such as Renault, who have preferred it in the past, appear to remain steadfast to it to-day.
Touching the methods of frame suspension, many manufacturers continue to hold to the transverse rear spring, and where this is the case one comes across, in a few examples, side springs at the rear, which are quite flat, the Niclausse and Sheffield-Simplex being provided with this style of suspension. The Lyons-made Buire cars have an altogether different pattern — a large specially-devised whole-elliptical spring - the ends of which, however, are linked.
Some cars possess real provision for the movement of the trailing axle, the extremities of which, a little consideration will show, tend to describe an arc of a circle. The rear spring arrangement of the new Phoenix car has sensible means of providing for the movement mentioned, since the front ends of the back springs are carried by universal joints, while a ball joint at the rear end takes the twisting stresses. Generally, springs are longer than hitherto, in spite of the extensive employment of the three-quarter elliptic sort.
As might be expected, frames pressed from sheet steel are found on all sides. The Deasy Co. keeps to armoured wood, as do Maudslay and Charron to wood-filled rectangular tubes, but very few other frames are so built. The depth of the channels in the large Italian Fiat frame is, in my opinion, good practice, for it aids very considerably in stiffening the frame, and is therefore effective against side twists — a point often lost sight of by some motorcar engineers.
The sharp cranking inward of the frame at the dashboard introduced by the German Daimler Co. is altered in their new live-axle car to a more gradual taper in front. Much upward and downward curving of the side members remains a common sight. In this respect, owners of early M.M.C. cars, for example, will realise what a change has been wrought in the 1909 model of the resuscitated company.
Underframes for carrying engines and gears are decidedly going out of fashion. To some extent the increasingly favoured unit system of combined motor and gearbox is responsible for this. On the other hand, where the three main elements — engine, change speed gear, and compensating gear — are separated, the two former components are often bolted direct to the side members by long arms or else to transverse stays. This last method is to be recommended, for several frames are not at all strongly stayed, that is, cross-pieces are few and too light in some machines. In the new Coventry Daimler we find that the engine arms are bolted to the top of the frame members. Three-point suspension of motors and gearing is fashionable, and as to the latter, the 1909 gearbox of the English Daimler car is noticeable.
The piston stroke in small and medium-powered cars is being lengthened for next year's models. Not only is this so, but as to the cylinder diameter there is a tendency to reduction.
Another remarkable fact is that nowadays manufacturers have little hesitation in using ball bearings for crankshafts. The time seems by no means distant when every journal of a motorcar will turn in such a bearing, but it must be of a suitable kind — the cycle pattern will not do for engine shafts and the like.
The casting of four small cylinders in one piece is a practice steadily gaining ground, and even for high-powered engines this style is adopted. The area of valve heads and passages has, generally, been augmented, which, up to a certain point, is commendable, but in one or two instances I should say that this has been carried too far.
One should not forget that the space occupied by very large valve heads reduces the available water-cooled surface, and the plea that easier ingress and egress of the gas is achieved is insufficient to counteract the effects of the heat developed. This appears to be one of the strong points of Knight's sleeve valves, for whereas the mushroom valve head is always in a position to receive the ill-effects of heat, in the American invention the position of the valve ports is moved to and fro, and last, but not least, the sleeves are lubricated, an impossibility with the seatings of mushroom valves.
If I remember aright, the French-made Cornilleau-Ste Bettye engine was one of the first modern motors to have cover plates over its valve rods and springs. Subsequently, Deasy and a marine motor firm, Collis, among others, followed this plan. Now several have adopted it notably Napier — and on this head I can imagine no sound reason against successful means being utilised to provide efficacious oiling of the poppet valve as near to its head possible.
Of lubricating systems, it may be said that a forced oil-feed is the rule. Even in inexpensive automobiles we find drilled engine shafts, oil wells in crank pits, and positively-operated pumps for maintaining efficient lubrication in large cars — such as the Delaunay-Belleville - the lubricating system is so well devised as to convey the impression that it is carried to a fine art. In fine, the practice of the steam engineer for fast-running engines has been imitated with beneficial results.
Of carburetters, there are so many different patterns as to cause bewilderment. Yet, for the most part they are all of a class. One point is evident: greater attention has been directed to a more accurate measuring out of petrol. Hence, here and there we now see carburetters designed to give more or less petrol — as the engine revolutions rise or fall — not by relying merely upon the effect of the air suction, but by enlarging and reducing the one or more orifices of the nozzle. Multi-jet or rose nozzles are to be preferred to a single small jet for two reasons, namely, that it is liable to become choked and that it is not so effective in diffusing a spray. Exhaust pressure feed for petrol is utilised largely, but a vogue is being established in adopting pumps to supply the requisite air pressure.
Except on some of the larger engines, throttle valves, operated manually, by foot, or both, are very common. It is true that centrifugal governors are preferred by many, but the erstwhile "thrumming" seems a thing of the past for petrol motors.
Magnetos on the high-tension principle are to be seen everywhere, even on cars of but low power, yet ordinarily these small engines are of high speed, and consequently, for myself, I do not relish the idea of starting up under certain conditions. On the more powerful machines double-firing equipment is general, and where both magneto and accumulators are inter-connected, troubles from these, sources should be few and far between.
The low-tension magneto is still used on some of the best engines, but it has failed to advance in general popularity, while the dynamo system of ignition is comparatively conspicuous by its absence. Great attention has been devoted to the methods of driving magnetos, many being particularly praiseworthy.
About a twelve month ago one of the earliest English automobile constructors gave it as his opinion to the Press that the motorcar with a live axle had then practically superseded vehicles with the chain drive. He foretold the complete abolishment of the latter sort in a short period. It would appear that this view has in a measure already proved true. The Sunbeam, Albion, and a few other constructors so far stand firm to the chain drive, but it is remarkable that scarcely any other firms which, as manufacturers of chain-driven cars, do not make their principal models with live axles. This will clearly show the non-professional motorist that the shaft-driven car is ultimately bound to be in universal use. And the shaft drive of two is of a different kind to that of some years ago, for considerable skill has been exercised upon its improvement, with the result that its mechanical excellence is not approached by any other type of drive.
The Lyons-made Pilain possesses in its new model what I regard as the most practicable drive, namely, a pair of transverse hook-jointed shafts forming the live axle, the change-speed and balance gear being supported by the frame, and therefore inumme from road shocks. This was a practice originally devised, I believe, by a British car maker, and is not unlike that of a famous French automobile. In the latter, however, the joints are closer together than in the earlier English and the new French machine, for the shafts are short in comparison with these vehicles.
In a fresh model from the De Dion-Bouton factory the differential gear is in its own box—suspended as before on the frame - the change-speed gear being forward behind the clutch.
Except for a few American and English cars, in which epicyclic gearing is used, the sliding gear is predominant. Cars of relatively small power have four ratios of speed, and not to have a through drive would be deemed obsolete. Touching the matter of gearing, the new English Daimler mechanism is noticeably compact. Speaking broadly, the dimensions of wheels and shafts are more correctly proportioned to their work. Again, even in cars of low price, we find selector-rod gate action, although in some cases the components appear to be scarcely strong enough for the work they have to perform.
The subject of change-speed gearing should not be passed over without reference to the third novelty of the Show — the Humphris gear. This is a large disc (taking the place of the bevel ring on a live axle) having four circles of countersunk holes and a ball-driving pinion (in substitution of the bevel pinion on a propeller shaft) to engage with any one circle of holes at will. It is also noteworthy that for the balance gear the same plan is adopted. If it is capable of achieving the advantages claimed for it — it certainly obviates bevel wheels — the inventor deserves success.
Of engines, the four-cylindered type far exceeds single, twin, triple, and six-cylindered motors. Last year an eight-cylindered car was to be seen at Olympia. Among the total number of car manufacturers exhibiting at Olympia (about 120) approximately 40 cater for the six-cylinder market, but, with one or two exceptions, their staple product is the four-cylindered machine.
Concerning clutches, the leather-faced cone sort continues to be regarded with satisfaction both by maker and user. On the other hand, a large number of cars are furnished with multi-disc and plate clutches. It is to be remarked here that the new 15 h.p. Mercedes has a leather cone clutch and that the engine of a new De Dion-Bouton car is so fitted. Hence, as such prominent makers now follow the established fashion, it is not unnatural to suppose that the simplicity and unquestionable reliability of a properly-made conical clutch has attracted them.
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