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Note: This is a sub-section of Motor Shows
Held from the 3rd to the 11th at Olympia
Detailed table 'Buyers guide' of all models.
The exhibition of motor cars for pleasure purposes, which opened to-day at Olympia, and which has been promoted as usual by the Society of Motor Manufacturers and Traders (SMMT), does not provide many new departures from current motor car engineering. In engine designing the two most marked features of next year's cars will probably be the further development of the chain driven cam shaft for operating the valves and magnetos, and the lengthening of the stroke. In transmission systems there will be few developments beyond the further adoption of the worm drive on the back axle. The chief object aimed at in fitting the worm drive is silence in running, but we fear that this object will be sometimes achieved at the expense of efficiency, especially when the worm is placed on top of the wheel and relies for lubrication on the oil which is carried round by the wheel from a chamber below. It is rather significant in this respect that most continental builders are adhering to the bevel drive. One of the difficulties in connection with the production of a silent running bevel driven car is that of obtaining the accurate meshing of the teeth of the pinion and plate wheel, and we note that a prominent firm of English builders is providing a means of adjustment for regulating the depth of engagement of the teeth.
The two chassis for 15 and 20 horse-power cars shown by Crossley Motors, Limited, Manchester, embody the improvements which this firm is introducing into next year's models. The former is practically the same as the 12-14 horse-power chassis now on the market, with one or two important alterations which have been dictated by experience. In the 15 horse-power car Messrs. Crossley are adhering to the unit system of construction as regards the engine mid gear box, but in the ease of the 20 horse-power car the engine is being supported independently in the frame at three points only. The gearbox is independently carried on a pair of tubular cross members, and is connected to the engine by a universal joint. The fan on both sizes is driven by a flat belt with automatic tensioning device. The radiators have increased capacity, and the water is circulated as before on the thermo-syphon principle.
In the design of the engines a modification has been introduced for operating the can shaft and magneto. This consists of chain gearing provided with a means of adjustment for the wear of the chain, and for the magneto and cam shaft timing. Bosch high tension magneto ignition is retained in both cases. In the transmission system the two-shoe expanding clutch hitherto employed is giving way to a leather-faced cone clutch of the internal type. In the 15 horse-power model a clutch spigot forms the extension of the crank shaft on which the clutch revolves, and is fitted with an ingenious form of lubrication. The lubrication of the engine crank shaft is forced under pressure to all bearings, and the clutch spigot shares in the oil so forced, a small valve connected to it opening for oiling when the clutch is depressed. A universal joint connects the clutch and gearbox, the latter being of the four-speed gate-operated type. All gear shafts run in ball bearings of large diameter. The drive to the back axle is through is propeller shaft enclosed in a torque tube, at the upper end of which is a spherical extension in which the universal joint at the back of the gear-box runs.
The back axle is not arched this season, but is straight, and the barrel-driving squares in the differential gear have been eliminated. The axle shafts pass right into the differential gear, but can be slid endwise for the purpose of removing the differential through a lid at the back of the casing. The main drive is by bevel gearing, the crown wheel being provided with a means of adjustment for regulating the depth of engagement of the teeth with those on the bevel pinion. This tends to give quietness of running, which is now so much sought after and frequently obtained with a sacrifice of efficiency by worm gearing. Brakes have undergone a process of revision. Front wheel brakes have not been found wholly satisfactory in the hands of the average driver owing to neglect of adjustment. They will not be fitted as the firm's standard practice on next season's cars. There will be large two-shoe internal expanding brakes on the rear wheels operated by a hand lever, and at the top end of the propeller shaft at the back of the gear-box another powerful foot-operated brake is being provided. Detachable Rudge-Whitworth wire wheels running on Timken roller bearings will be used.
Referring to the accompanying illustrations, Fig. 1 represents a complete back axle of the 20 horsepower Crossley car showing the stiffened stays to the fixed hubs for the detachable wheels and calling attention to the new brake drums of large diameter and width. Fig. 2 is a view of the end of a 15 horse-power engine showing the chain drive to the cam shaft and magneto. Inside the magneto wheel is an adjustable arrangement for accurate timing of the cam shaft. The plate covering the timing wheels carries a bearing in which the end of the magneto wheel runs. There is also a similar bearing at the back next to the magneto. A small plate carrying this bearing is slotted, and the bracket on which the magneto rests is also slotted and consequently the chain drive at the front of this engine is fitted with an adjustment for slackness, in addition to the adjustment for tinting. Fig. 3 is a view of the 20 horse-power Crossley engine, showing the wide case at the front of the engine for accommodating the chain drive, and the new flat belt and automatic adjustment for the fan. It also shows, screwed into the valve cap next to the radiator, the valve worked by the explosion of the motor for maintaining pressure in the petrol tank. Fig. 4 shows the brakes of the 15 horse-power car at the back of the gearbox. These brakes arc of the two-shoe cam-operated type with large surfaces. It will be noticed that the drum is drilled with air-cooling holes, and also fitted with radiating fins. This view also shows the three-arm steel stamping carrying the torque ball. Fig. 5 shows the rear brakes with the brake drum removed, showing the end of the cam which operates the brakes, and illustrating the heavy dimensions of these new brakes. Fig. 6 shows the 15 horse-power complete unit. Figs. 7 and 8 are details of the back and front axles, and on page 468 several detail views of the 20 horse-power car are given.
One of the most attractive features of the show this year is a new sleeve valve engine of the four-stroke type. Although expert opinions differ regarding the merits and demerits of sliding sleeves it is unanimously agreed that the engine shown by Argyll's Limited is an extremely ingenious invention. The essential difference between this motor and that built by the Daimler Company is that the former has only one sleeve to which a compound rotary and reciprocating movement is given, while the Knight engine has two sliding sleeves which move vertically. From the accompanying illustration – Fig. 10 — it will be observed that the crank shaft, connecting-rod, and piston are of the usual types. The sleeve valve operating shaft B is driven from the crank shaft A by means of the popular method — chain gearing — and revolves at the same speed. On this shaft B opposite to each cylinder is a worm wheel C which engages with a disc wheel D and drives the latter at half the speed of the crank shaft. This disc wheel is carried in a phosphor bronze cage bearing, has a ball thrust and oil retaining cap, and may easily be withdrawn. On the face of the disc wheel, and at a fixed distance – 1.5in. — from the centre, a hole is bored, and in this hole a pin E is free to revolve and move inwards and outwards. This pin E has a flattened end which fits between the jaws at the bottom end of the sleeve valve F and is held in position by a bolt which passes through a hole in the pin and corresponding holes in the jaws of the sleeve F. This pin is free to swing sideways only in the jaws of the sleeve. As the disc D revolves with the pin E it carries the sleeve with it, so that the sleeve, besides travelling up and down, also moves round on its axis in one direction when the pin E is making the top half of its revolution, and back again in the opposite direction when the pin is making the lower half of its circular path. The compound movement thus given to the sleeve may be observed by holding a pencil against it. For each revolution of the disc wheel an ellipse will be drawn on the sleeve. In the cylinder there are six ports, three on each side, those on one side being the induction ports and those on the opposite side the exhaust ports. In the sleeve there are five ports, two for admission of the mixture of air and gas, and two for the outlet of the products of combustion, the odd port acting alternately as an inlet and exhaust passage. The cylinder is closed at the top end by means of the cover 0, which is made like a piston and of the same diameter as the working piston. It projects into the cylinder, forming an annular space inside the cylinder wall in which the sleeve works. It is provided with a broad spring ring II. The arrangement of the ports is shown flattened out diagrammatically in A, Fig. 9. In this diagram it is assumed that the piston is just commencing the suction stroke, and the admission ports in the sleeve travel over the inlet ports in the cylinder wall, following the elliptical path until, on reaching the completion of the stroke, the ports have reached the position shown in C, Fig. 9, and the bottom edges of the ports in the sleeve are just about to pass behind the broad ring in the head. As the piston moves upwards on the compression stroke the sleeve also moves upwards, the ports travelling well up behind the ring till at the highest point in the sleeve's travel — D, Fig. 9 — ignition occurs. As the piston moves out on the explosion stroke the sleeve travels with it, and when the piston is almost full out the sleeve ports are in the position shown in E, Fig. 9, with the inlet ports passing between the inlet ports in the cylinder wall.
In E and F, Fig. 9, the piston is almost full out on the power stroke, and the exhaust ports have come down below the broad ring of the head, uncovering the exhaust ports in the cylinder. As the piston rises on the exhaust stroke the sleeve ports travel over the cylinder ports till they reach the position shown in A, Fig. 9, when communication with the exhaust pipe is almost cut off. During the exhaust stroke the admission sleeve ports have moved between the admission cylinder ports from the position shown in E and F, Fig. 9, to that in A, Fig. 9, so that when the exhaust port is just closing — as in A, Fig. 9 — the inlet ports are just opening. The piston now travels out on the induction stroke and the sleeve exhaust ports pass between the cylinder exhaust ports — as in B, Fig. 9 - so that when the piston reaches the bottom centre the ports are just passing behind the ring in the head — as in C, Fig. 9 - and continuing to move up with the piston they reach the point shown in C, Fig. 9, at the moment of ignition. Then travelling downwards with the piston on its explosion stroke they uncover the exhaust cylinder ports at the end of the stroke — as in E, Fig. 9. It will be seen that the sleeve never comes actually to rest while the engine is running, and it is justly claimed that the twisting motion helps lubrication. The cylinders and heads are well cooled by spacious water jackets, the water being forced by the pump up through the jackets into the heads, which are joined together by rubber joints, and from the front head the water flows into the radiator.
The magneto and water pump are driven by a single shaft which runs across the front of the engine and is driven by skew gearing off the sleeve driving shaft. The lubrication system depends upon the oil pump shown in Fig. 10. This is driven by skew wheels at right angles to the sleeve driving shaft, and is situated below this shaft. There is an oil trough beneath each cylinder, into which the big ends dip. The oil, after being used, passes again into the main oil reservoir after being filtered. It is filtered a second time before being returned to the working parts. The oil pump sends the lubricant through a tell-tale on the dash, thence to two oil ducts running along the side of the crank chamber, from which other ducts lead into the main bearings, which are fed with oil under pressure. The troughs, worm gearing, and oil pump are also kept supplied with oil in the same way.
In accordance with custom, the Society of Motor Manufacturers and Traders held their annual show dinner on Tuesday night at the Connaught Rooms, Great Queen-street, London. The company numbered nearly 400, and included the Duke of Teck, who was the principal guest. In responding to the toast of the "Motor Industry," Mr. E. Manville, the President of the Society, laid particular stress on the necessity of abating the noise resulting from the use of motor cars from the abuse of the motor horn. He said that unless steps were taken by the owners and drivers in this direction restrictive legislation would follow. With regard to the progress made in the use of motor vehicles, Mr. Manville mentioned several interesting facts. He said that although it was only since 1908 that the twenty-mile speed limit had been in force, six years after that date 50 per cent. of the traffic in London was carried by motor vehicles. To-day 92 per cent. of the passenger-carrying traffic was by means of motors. For commercial purposes, ten years ago a little more than 8 per cent. of haulage in London was done by motors; now the percentage was 14, which represented; an immense freightage.
LAST week we indicated briefly what would form the predominant features of the exhibition of pleasure cars which is being held at Olympia, and we alluded to the decided tendency to long stroke engines in order to obtain from cylinders of a certain bore an increase of power. A feature which we did not mention is the attempt on the part of American makers to capture the British market as far as this is concerned with the cheaper car. Our readers will remember that our cousins across the Atlantic attempted something of the sort with toy-like and flimsy steam cars, and previously with the safety bicycle. In both cases the attempts if not failures, were scarcely successful, and it remains to be seen whether the present petrol car will prove more successful than the objects referred to. At any rate we are glad to see that several British motor car engineers are endeavouring to place on the market vehicles which, though not quite so low priced, are essentially more substantial and likely to prove a better investment to the purchaser than the American cars.
In the early days of the motor car movement an idea prevailed that the popular car of the future must be sold at about £100, and indeed several makers attempted to supply the want, but found that it could not be done with satisfactory commercial results, nor are we perceptibly nearer to its accomplishment at present. Nevertheless, the pleasure car movement has developed beyond all anticipations, and the people who were in search of £100 cars are now quite prepared to pay more than twice this sum. It seems as though the price of a commodity is of no consequence when the public sets its mind on having it.
In Fig 11. we give, sectional views of the re-designed six-cylinder Sheffield-Simplex engine. It will he observed that the cylinders are cast in groups of three with capacious water jackets. The bore and stroke of the cylinders are 89 mm. and 127 mm. The crank shaft has plain bearings, and is of stiff design, with a bearing between each pair of cylinders. The poppet valves are operated by a special form of mechanism and cam shaft shown in the cross-section b, all of which is enclosed. Lubrication is effected by means of a mechanically driven pump supplying oil to all journal bearings under pressure and to troughs below each connecting-rod end. Silent worm timing gears with an inclined worm, as shown in section, driving the magneto and oil pump, form a feature of the engine. The advantage claimed for this arrangement of gear, in addition to silence, is that the contact breaker and distributor are placed in a very accessible position. The engine is cooled on the thermo-syphonic system, and with this object the pipes and jackets are exceptionally large. The Eisemann dual magneto high-tension ignition with solid multi-core wiring are fitted, dispensing with separate wires and providing hinged switches to the plugs. Another usual feature of the Sheffield-Simplex cars is retained, namely, the mounting of the gears at the rear end of the propeller shaft. All cars have three speeds thus provided. The live axle is arched and the load is taken on the axle tubes and casing, and the bevels and differential gear are very easy of access by removing four nuts. The clutch is of the multiple disc type with flat metal plates lubricated by dry graphite. The car is controlled by two pedals, one of the push type operating both the clutch and foot brake, and the other a sliding pedal with side rocking movement only, controlling the engine throttle. The highest class of material is used in the Sheffield-Simplex care, all transmission shafts and gears being made from steel of 122 tons tensile strength.
The valve question continues to find food for thought and discussion. Last week we alluded to the new sleeve engine exhibited by Argylls, Limited. This ingenious invention, it appears, was invented simultaneously by two persons, one Mr. Peter Burt, in Glasgow, and the other, Mr. J. H. K. McCollum, in Toronto. An inspection of the engine at Olympia confirms our first impression concerning the ingenuity displayed in obtaining the compound motion of the single sleeve, whereby it can perform the dual function of admitting gas to the cylinder and allowing the exhaust, gases to be expelled alternately.
The French firm of Darracq has attacked the problem, in a different way. The Henriod engine which is to be fitted to the 20 horse-power model Darracq car next year is claimed by the makers to be a big step in advance of the sleeve engine, and indeed if the reduction of the working parts of a petrol engine to an absolute minimum be the final goal, it may claim to have found one solution of the question. But we fear there is some virtue in the "if." In the Darracq engine the valves, tappets, springs, and cam shaft are done away with and in their place in provided a cylindrical distributor which is driven from the front end of the crank shaft by worm gearing. The distributor is carried in the same casting as the cylinders in the same relative position as the valves of the poppet engine. It is a working fit, and is carried at either end in ball bearings. In transverse section it varies from the annular shape between the cylinders to a D section opposite the combustion head ports. This D section allows of through connection at the proper time between the inlet gas chamber situated directly above the distributor and the combustion chamber through the ports. The movement of the D sections of the distributor are arranged to synchronise with the movements of the pistons, on the inlet and also on the exhaust strokes, while on the compression and firing strokes the cylindrical side of the distributor covers the port into the cylinder. An important feature of the operation of the engine is that at the moment of explosion the distributor is isolated from the combustion chamber by arranging that the piston shall cover or lap the port by an amount approximately equal to one-sixth of the stroke. In this way the distributor is kept free from the effects of the explosions. A point which will occur to engineers as objectionable in this method of distribution is the possibility of uneven expansion and tendency to binding, but the makers inform its that the distributor is cast from a special mixture of iron by which expansion is reduced to a minimum. The distributor is said to be efficiently lubricated by the oil carried up by the pistons, but it would seem that some better means will be found necessary. The cylinders, 95 mm, bore by 140 mm. stroke, are cast en bloc to shorten the crank case. Another new feature introduced by Darracq is the worm driven back axle, the worm being placed above the worm wheel.
Another engine, which is exhibited, we believe, for the first time at Olympia, is the rotary valve engine made by Itala Automobiles, Limited. This engine is rated at 35 horse-power, and has four vertical cylinders cast in pairs, the bore and stroke being 105 mm. by 150 mm. The four inlet and exhaust valve spaces in the poppet valve type of engine are replaced by two spaces, each containing a rotating valve that acts as a distributor.
This valve is of simple design and is connected by it vertical rod to one shaft that takes the place of the two cam shafts. The function of this shaft is to drive the magneto and water pump and to rotate the valves. The latter is effected by means of an endless screw, the same as used by this firm for driving the firing cams of the low-tension ignition. Each rotating valve exercises the same functions as two inlet and two exhaust valves. The ordinary water and oil circulations for cooling and lubricating are used with the rotary valve, which rotates only once to four rotations of the engine, In order to preclude the chances of "seizing" - a wedge is inserted in the vertical rod, which rotates the valve, and this severs the connection should the resistance to movement become excessive. In order to ensure regular and even functions of the rotary valve there are two compensating chambers in the wall of the valve cylinder, so that all pressure on the valve due to the explosions is obviated. It is claimed by the makers that, as the only reciprocating parts of the engine are the piston and connecting rods, the engine can be run at higher speeds than usual without vibration; that as the rotating valve, which is on the side of the cylinders, rotates almost in contact with the combustion chamber, and there is no valve space on the other side of the cylinders, there is an increased efficiency,
There is another feature worthy of mention in the Itala car, namely the final drive on the back axle. The driving shaft terminates in a helicoidal pinion which engages with the crown wheel on the differential box, giving silence and regularity of turning equal to that of a worm without the tendency to wear which prevails with the latter.
Figs. 14, 15, 17, and 18 are photographic representations of the mechanical features of the 38 horse-power Lanchester car. Unlike most of the English builders, Messrs. Lanchester retain the short-stroke engine, the six cylinder having a bore and stroke of 4in., and give 45 to 48 brake horse-power at 1,400 revolutions per minute. Other features peculiar to the Lanchester engine are the casting of the cylinders in pairs, large inlet and exhaust ports, and water conduits forming part of the cylinder castings, with joints made by means of rubber rings. The engine has steel pistons, horizontal valves, short valve stems, and flat plate springs. All the valves are interchangeable, and the products of combustion from the explosions are passed through the cylinder jacket, thus, it is claimed, cooling the gases and silencing the exhaust. The valve mechanism is shown in Fig. 17, from which it will be observed that the valve tappets are set up by an excentric pin, it being only necessary to move the finger plate one or more notches. The cam shaft is carried outside the engine easing, and is completely enclosed in phosphor bronze bearings, which are dust-proof. It can be readily dismounted when necessary. The crank case is of aluminium, cast in two halves, and the bearings in the top half of the crank case are of ample proportions. The lubrication is by high-pressure force feed. The ignition is by Bosch high-tension magneto, and the magneto terminals are carried by a rubber stock.
The arrangement of the wick carburetter and petrol tank is clearly shown in Fig. 16, the petrol tank forming part of the structure, and absorbing the torsional stresses. The vaporiser chamber is on top of the petrol tank and contains the wicks. Warm air is drawn from the exhaust pipe and can be regulated as desired, while the supply of gas can be graduated by means of a butterfly throttle with a spherical bore. The petrol is lifted from the tank to the carburetter by means of a positive pump driven from the engine, as shown in Fig. 16.
Messrs. Lanchester still retain their favourite epicyclic gear, which gives three forward speeds and a reverse, with the direct drive on the top speed. The speeds are changed by means of a gate. The clutch is of the multiple disc type, and forced lubrication is provided for the gear-box. The worm-driven live axle with roller hearings and ball-thrust bearing are retained, together with the long cantilever springs and the Lanchester form of suspension.
Another engine which differs from the orthodox types in important points is the Spyker. In this motor silence of working is secured by a helicoidal wheel A — Fig. 19 — fixed on the crank shaft B. This drives by a similar wheel C a short cam shaft D, which is square to the crank shaft. On each end of the cam shaft a cam E is fixed. These cams lift two or more valves by means of levers. The valve gear is mounted on a detachable bracket to provide adjustment if there should be any play in the worm wheels, and the whole of the mechanism being enclosed in the crank chamber effective lubrication is secured. The pump and magneto are also driven by helicoidal gear wheels. In the 12 horse-power model shown by the Spyker firm the differential casing and gear-box form one unit, in which the bevel pinion transmits motion to a crown wheel keyed to a short shaft parallel to the back axle. On this same short shaft are two sliding spur pinions which can be engaged with spur wheels of various sizes on the differential casing, so giving different road speeds. In larger models, however, the motor and gear-box are made en bluc.
Several meritorious attempts have been made by inventors to replace the gear-box and clutch of the motor car by a hydraulic transmission system, but these have not been taken up to any serious extent commercially. Mr. Hugo Lentz, Berlin-Grunewald, shows at Olympia a hydraulic gear which consists of one casting containing two cylinders arranged at right angles to each other, in which rotary pump pistons are fitted. The whole is intended to be fixed over the back axle in the direction of the main drive. The pump forming part of this mechanism is driven direct by the engine, and two differential pistons drive the wheels. The whole of the mechanism runs in oil.
If there is anything noteworthy to report with regard to the design of clutches it is the return to favour of the leather-faced cone, bearing out the old adage, "there's nothing like leather." A few years ago nearly every maker of motor cars was busying himself with the production of a new design of clutch, with the result that extra complications of very doubtful improvement were introduced. All drivers of motor cars know only too well what a boon a smoothly working clutch is, and what damage can be inflicted by that fierceness which is frequently observed with metal clutches. Leather possesses a quality which renders it peculiarly adaptable for frictional driving, and with the cone designed to the proper angle and a little attention on the part of the driver to the condition of the leather nothing better can be desired. With the removal of the subsidiary frames for carrying the engines designers are now at liberty to give a larger clutch, which means a longer life and bigger fly-wheel. The process of de-clutching is now much easier than formerly owing to compound leverage devices combined with lighter springs and shorter range of movement.
The Knight engine with its sleeve valves is now in use in cars made by the Daimler Company, the Rover Company, and also by the Deasy firm in this country. On the Continent it has been taken up by the Mercedes, Minerva, and Panhard concerns. The Knight engine may therefore be said to have fairly established itself as a formidable rival to the poppet valve engine.
The Daimler Company's exhibit, which comes in for the usual amount of attention, includes a new four-cylinder 20 h.p. model with cylinders 90 mm. bore by 130 min. stroke. Four speeds are now provided in the gear-box, and thrashing of the crank shaft — a common feature in most petrol engines when a certain speed of rotation is attained — is obviated by an ingenious device called a vibration damper fitted in the pulley on the crank shaft, which drives the fan. It consists of a small multi-disc clutch, half the plates of which are attached to the front end of the crank shaft, the rest being fixed to the pulley. Although always in engagement, the device is not rigid, and when the crank shaft speed arrives at its critical period, when excessive vibration commences, the clutch slips slightly and a drag ensues, which damps down the thrashing tendency.
We regret that we cannot express ourselves in terms of unqualified praise of the new B.S.A. car, although in the words of the makers "it stands in a class by itself." American practice has been followed too closely in the design of the chassis. Ample power is provided. The engine is of the sliding sleeve pattern, with four cylinders 75 min. by 114 mm., and is capable of giving 25 horsepower for extended periods. It is connected to the frame at three points, by a trunnion bearing at the front and by two projecting side arms at the rear. Immediately behind the engine is a strong frame cross member to support the universal joint at the rear of the leather-faced cone clutch to take the driving stress communicated from the torque tube. The three-speed gear and reverse-box is housed in a forward extension of the rear axle, from which it is separated by an oil-tight division, so that the lubricant in each may be kept separate. The rear axle is worm-driven and the differential is of the bevel typo. The springing of the car is distinctly American as regards the back of the vehicle, a long arched and inverted transverse spring being provided.
Quite a number of English firms which originally set out to provide the more expensive and high-powered motor vehicles are now taking up the higher grade ears of moderate and small powers. Amongst these firms the most prominent in this respect is S. F. Edge, Limited. This firm's experience with public hackney carriages has enabled it to improve the design of the 15 horse-power Napier car in several important details. One of these is the adoption of the transverse in conjunction with the longitudinal side plate springs. The back axle casing, too, has undergone some modification. It now consists of four distinct portions, namely, a central casing E, Fig. 20, made in two halves and carrying the differential gearing and worm drive box and a tubular extension on each side. The tubular extensions are spigoted into the casing, as well as being bolted to it by large flanges G. The axle casing has also a tension stay H extending from side to side and the tubular extensions are made from solid bars of steel, being bored out by a special machine. A marked improvement will be noted in the brackets J which carry the springs. These are wide bearings mounted on journals between the flanges of the axle extension and have screw-down greasers to provide lubrication at this point. The unit system enables the whole of the propelling mechanism to be suspended at three points, and so relieves the mechanism from road strains. The gear-box casting is divided into two compartments, the front containing the clutch and the back the gears. The clutch is of the multi-plate pattern and runs in an oil bath. The engine has four cylinders, 3.5in. bore by 5in., and the Government rating is 16.9 horse-power.
Although the worm-driven live axle continues to receive fresh adherents, signs are not wanting of a tendency to revert to the bevel drive. Some of the makers who are fitting the worm-geared axle show ignorance of the lubrication problem with which they are faced, and seem satisfied with a system of oiling which has been successful with the bevel drive. As we have previously pointed out, the only really satisfactory arrangement for a worm-driven axle is that in which the worm is placed below the wheel, so that it is immersed in oil. This arrangement generally necessitates the inclination of the engine at a slight angle, so that the crank shaft and propeller shaft will be in line. The greatest drawback to this plan is the small clearance between the worm and the road - probably 7in. or 8in. — which would be dangerous for colonial purposes. If, on the other hand, the worm be placed on top of the wheel the engine may be horizontal, but a dry surface on the worm wheel will be presented to the teeth of the worm when the torque is greatest, namely, at starting, and wear will ensue. The introduction of the silent worm gear has, however, been beneficial, inasmuch as it has called attention to the necessity of improved methods in the production of satisfactory bevel gearing; such as the prevention of distortion of the plate wheel due to case-hardening. One of the most silent cars on the market — the Rolls-Boyce — has retained the bevel drive.
As regards carriage springs there is little that is really new, and opinion appears to be divided. The Wolseley cars of 16-20 and 20-28 horse-power have under-slung three-quarter elliptic springs, the front bracket being made to swivel to improve the lateral flexibility of the live axle. The fact that the "C" shaped quarter spring is lacking in lateral stability assists this action in much the same way that the cross swivel link attachment does to transverse springs on the larger models. This arrangement of three quarter springs has been found by the makers to give easier riding than semi-elliptic springs, especially on light cars, and is lighter than the transverse arrangement still retained for the larger cars. Much of the rattling and noise that become noticeable when a car has been run for some time are caused by slackness in spring pins. The cause lies frequently in the smallness of the bearing surface and difficulty in lubrication. Hardened hollow pins which cannot turn, and which are properly lubricated, form a feature of the Wolseley cars. The bearings of the springs on the pins are composed of phosphor-bronze bushes, and the end thrust is taken by large flanges, which are faced steel housings of the box type to exclude water and grit. The Wolseley Company has also adopted chain gearing in its engines. Two chains are used, one chain driving from the crank shaft to the cam shaft, and a second chain from the cam shaft to a shaft which is an extension of the pump spindle, the magneto drive being carried right through the pump. After a series of experiments on cam form as affecting the power developed, the same firm has slightly altered the lift and timing of the valves and the cam form, so that the power of the engine has been increased, particularly at high speeds, without adding to the noise caused by the tappets.
It is rather remarkable that while some motor car engineers are going to almost absurd lengths in silencing their engines they also fit that most objectionable feature known as a "cut-out," which allows the exhaust gases a free escape to the atmosphere. On their larger models the Wolseley Company fit dual silencers. These give s very efficient silencer for slow running and in towns in combination with a by-pass for country use. This bypass allows a portion of the exhausted gas to escape direct through the tail pipe to the atmosphere under ordinary touring conditions, and with little perceptible noise. In this way back pressure is prevented and a saving in fuel is effected.
The satisfactory results which have been obtained with chain-driven change-speed gears on motor omnibuses has led to the development of this form of gear for pleasure cars. The Maudslay Company is showing a silent gear-box in which the chain sprocket wheels are clutched to the gear shaft by sliding dogs worked by a gate-change, the drive on all speeds being indirect. There are four chains in the gearbox, but only two chains of different lengths, and two different pitches are necessary, owing to the fact that the first speed ratio is the inverse of the fourth and the second the inverse of the third.
The firm of Dennis, of Guildford, also shows a gear-box with chain gearing.
Amongst the exhibits of the Humber Company, the four-cylinder 11 horse power car has attracted much attention. The cylinders are 68 mm. by 120 min. and are cast en bloc. All the bearings are automatically lubricated, oil being forced through the crank shaft by a rotary pump driven from the engine passing through a tell-tale on the dashboard. This car is rated by the Government formula at 11.3 horse-power, and it comes under the three-guinea tax. The engine has thermo-syphon cooling and high-tension magneto ignition. There is nothing remarkable in the transmission system. A leather-faced cone clutch, three-speed gear-box, and bevel gear transmit the power to a live axle. The frame is of pressed steel, and the engine and gearbox are carried on a sub-frame. The same firm also shows 14, 12-20, 20 and 28 horse-power models all with four-cylinder engines. Probably manufacturing reasons have dictated the use of worm gearing on some of these models and bevel gearing on others. A striking anomaly in the Government system of rating is shown by a comparison of the 12-20 and 20 horse-power engines. The former has a bore of 90 mm. and stroke of 100 mm., while the latter has a similar bore but a stroke of 120 mm., yet they are both rated for taxation purposes at 20.1 horsepower. Both the design and workmanship of this firm's cars show a great improvement over those turned out by the same firm only a few years ago.
Mention should not be omitted of a car which is a newcomer to these shows, namely, the Baguley. Its design shows sound knowledge of motor car engineering rather than originality of conception. The engine has four cylinders 90 mm by 130 mm., and runs at a normal speed of 1,000 revolutions, at which it gives 21 brake horsepower. The cylinders are cast in pairs, and have a high tensile steel crank shaft running in three phosphor bronze bearings of large size, lined with white metal. It is carried by the upper half of the crank chamber allowing the lower portion to be removed easily. The timing wheels are of the spiral form, alternately hardened steel and phosphor bronze, and are continuously lubricated from the oil force pump. The cam shaft is of special case-hardened steel, and the cams are solid with the shaft, the tappets being adjustable and fitted with springs to reduce noise. Oil is forced by a gear pump placed in an accessible position on the engine to all the main bearings, thence through the crank shaft to the big ends. The clutch is of the multiple disc type, with the whole of the sliding and moving parts working in an oil bath, and the universal joint between the gear box and the clutch is of the ring pattern. The gear box provides four speeds, the shafts being of nickel steel, castellated, and as short as possible. The final drive is by means of worm gearing, with the worm on top, the differential being of the bevel type.
Much ingenuity is being brought to bear upon the design of electrical apparatus for lighting purposes. To produce a suitable dynamo to be driven from a motor car engine with wide speed variations is no simple undertaking. It is essential that the output of the machine be constant over a wide range of speed so as to ensure a uniform supply of current for charging batteries and lighting the lamps. With this object the dynamo should cut in and reach its maximum output at a comparatively low speed, so that the battery may be charged even when the car is running slowly. It is also desirable that the output of the dynamo at normal speeds should exceed the lighting load, for if the output is insufficient the battery will have to discharge while the engine is running, and will have no reserve current for use when the engine is at rest.
The firm of Trier and Martin, Limited, Great Portland-street, W., is showing an equipment which appears to conform with these requirements. The dynamo generates current at a comparatively low speed, reaches its maximum output rapidly, and this remains constant as the speed increases. The regulation is effected by the use of two extra brushes which operate in such a manner that at low speeds they intensify the field flux, while at higher speeds part of the main current passes direct from them to the outer circuit. This relieves the current in the main brushes while decreasing the field flux, thus keeping the output constant at all speeds. Working in conjunction with and attached to the dynamo is a cut-out. It consists of a disc mounted on the armature shaft and revolving in a bath of mercury in the outer casing. An insulated contact is situated in a recess, so that normally the mercury is at rest below the pocket. As soon as the armature revolves the mercury is drawn up by the disc until, at a certain speed, it reaches the insulated contact, thus making the electrical connection. When the rotation of the armature falls below the generating speed the mercury falls back and breaks the connection.
Another electrical lighting equipment is shown by S. Smith and Son, Strand, W.C. The dynamo is of the ordinary design with no subsidiary poles or mechanical governors, and works in conjunction with an electrical control, so that a constant output of 8 amperes is supplied to the accumulator, no matter what the speed of the engine may be.