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Note: This is a sub-section of Motor Shows
Held from 4th to 12th November at Olympia
Students of motor car construction will observe few really radical departures from orthodox practice amongst next year's patterns as exhibited at the Olympia Show, which opened to-day. The tendency of late years to adopt the four-unit principle in engine design is even more marked than at previous Exhibitions, and this is resulting in a further displacement of the single-cylinder and twin-cylinder engines, while the triple-cylindered engine is a thing of the past, except in the case of one of the steam cars shown.
Since last year the sleeve valve has advanced in public favour; but the builders of cars with this type of motor are limited to about six firms, and these all confine themselves to the Knight principle. There is still much controversy concerning the comparative merits and demerits of the rival poppet-valve and sleeve-valve engines. Those who are able to offer a disinterested opinion do not admit all the advantages that are claimed for the sleeve valve.
On the question of silent working, which all the large makers are striving after, the Knight engine is certainly a step in the right direction. It seems to be superior to the best modern poppet-valve engines only when running slowly under load. Under ordinary running conditions there is little difference. With regard to the power developed, there does not seem to be evidence of material improvement. While the sleeve-valve engine is as simple as the poppet-valve engine, it must be borne in mind that the valves of the latter are much easier of access than the sleeves of the Knight engine, and less serious trouble is likely to occur with the poppet-valve than with the sleeve-valve engine in case of defective lubrication.
Although improvements have been made in the Knight-Daimler engine as regards lubrication, on the ground of smokelessness the poppet-valve engine seems to hold its own.
The system of taxation of motor cars introduced by the present Government, whereby only the bore of the cylinders is taken into account, has led makers to revise their cylinder dimensions somewhat, with the result that in some instances the power of engines has been maintained — if not increased — while the bore of the cylinders has been reduced. To effect this the stroke has been lengthened. The system of rating adopted by the Treasury officials is that of the Royal Automobile Club, namely the diameter of the cylinder in inches, squared, multiplied by the number of cylinders and divided by 2.5. For double-acting engines the formula is altered by dividing the constant 2.5 by 2.
It would seem that whenever chain driving is displaced for any particular purpose, a new application is found for it. Our remark is suggested by the almost complete replacement of the final chain transmission system by a propeller shaft and either bevel or worm gearing. The chain has, however, now made its appearance in the engine itself. The Knight engine was the first petrol engine to use chains for operating the valve shafts, and the example is now being followed by the Humber Company in its new designs both for the timing gears and the magneto shaft.
With regard to ignition apparatus, the high-tension magneto is now almost universally adopted. So simple and accessible has this appliance now become that the old fears of breakdowns need not be entertained. For starting purposes, however, it is frequently combined with a high-tension accumulator system.
Messrs. Lanchester and Dennis must feel flattered by the number of cars fitted with worm driving gear. About three years ago the makers of cars employing this type of gear were limited to two or three, whereas time of the leading builders, such as the Wolseley Company, Vulcan, Sunbeam, Singer, Rover, New Engine Company, Lanchester, Dennis, Daimler, and Argyll companies, have now taken it up, while in the new 25 horse-power Sheffield-Simplex engine the cam shaft and magneto are both operated by worm gearing in a novel manner.
Generally considered, there is not much alteration in gear-box design, but there is a growing tendency to increase the number of gears from three to four, which is a step in the right direction, as it approaches more closely to the ideal variable speed gear. In this connection the 25 horse-power Sheffield-Simplex car has three speeds arranged in the gear-box on the back axle.
The experiences of a year's running of the Crossley cars have confirmed the makers' belief in their general principles of design. The engine remains practically as last year, with the exception that the lubricating arrangements have undergone a slight modification. The oil is fed into the crank chamber through the filler A — Fig.3 - and the quantity in the chamber is always visible in the gauge glass B. The spur wheel type oil pump C is driven from the end of the crank shaft; it lifts the oil from the sump and delivers it through the pipe D to the ducts E, and thence to the crank shaft. From the big ends of the connecting-rods the oil flows up the tube F to the gudgeon pins. In addition, the oil pump also forces lubricant through the pipe G into the gear wheel casing. A pressure gauge is provided on the dashboard to show whether the required pressure of oil is being maintained. A spring loaded relief valve H is fitted above the gauge glass B, and this returns any excess of lubricant to the sump. To add to the completeness of the lubricating arrangements a cock J is fitted on the pump for priming if necessary. The valves are fitted with a dashpot plunger device, as in last year's pattern, to ensure quietness of operation. It has been found, too, that further quietness of the valve mechanism is gained by grinding the cams to a very fine surface after milling.
The design of the carburetter — Fig. 1 — has been altered by the substitution of a rotary throttle valve for one of the plunger type. This is shown at K. S is the petrol jet supplied with spirit by the float chamber R and passage V, and the quantity which is allowed to pass is regulated by the pull of the engine through the medium of the piston M, rocking lever L, and needle valve T. The dashpot is fitted with a screw V for adjusting the travel of the piston, and a screw R for regulating the vacuum.
One or two important modifications have been effected in the gear-box — Fig. 8. The clutch of last year showed a tendency to fierceness if not carefully adjusted, and this is being remedied by means provided for distributing the pressure on the shoes more equally. A flexible joint A of neat construction is now interposed between the gear-box and clutch shaft and the intermediate gear sleeve B in the box. This sleeve carries an intermediate gear between two sets of roller bearings, and ball bearings are provided throughout. The box provides four speeds, and the gear wheels on the second motion shaft C are carried on two sleeves bolted together, as shown. D is the primary gear shaft, E a socket on the rear end of the gear-box to take the spherical end of the torque tube, and E is the propeller shaft. Between the end of this and the primary shaft is interposed a helical spring to prevent chatter.
Another feature which the builders have found it desirable to re-design is the front wheel brakes. The new arrangement, as will be soon in Fig. 2, brings the brake drum and shoes on an imaginary line drawn between the point of contact of the tire and the centre on which the wheel is supported. The brakes are operated by a pedal causing the rod L to revolve, and in so doing this rod causes the trigger M to raise the plunger N. When this is raised it lifts the lever O and tends to move the circular cam P round to the left. This moves the brake shoes Q out against the inner surface of the brake drum R. When released the cam ring P is returned to its normal position by the tension of the springs and the rollers shown. The hub of the wheel and brake drum are connected by studs shown, and the wheel is easily removed. The brake mechanism is easy of access, as the inner hub and drum R can be removed by taking off the cover plate X and unscrewing the nut Z.
The New Engine (Motor) Company, Limited, is introducing in next season's cars a now arrangement of springing, combined with safety radius rods. The drawing —Fig. 5 — represents the rear spring in side elevation. The inner end of the spring is firmly secured in a box shaped casting, which is bolted to the frame, while the outer end rides freely in a casting which takes a bearing on the axle tube. The axle is connected to the frame of the car by means of a radius rod, which is firmly secured to the box casting holding the inner end of the spring. The particular features claimed for this method of suspension are:— Flexibility with a short spring, as the outer end of the spring barely projects beyond the axle; the point of suspension is high as compared with the centre of gravity of the car, and thus excessive rolling on turning corners is avoided. End stress on the spring is obviated, as the spring is quite free in the bracket on which it rides on the axle, and in the event of a collision or other accident, it is impossible for either the spring or the main car to be damaged, because the stress can only be transmitted through the radius rods. These are specially made of such a section that, while very strong vertically, they will give sideways, and so save the other parts of the car. The radius rod also acts as a safety device in the very rare event of the breakage of a spring. It will be noticed that both the bottom leaves of the spring have to be broken before the spring can entirely give way, but should this happen the spring can only drop down on to the radius rod, leaving the car still in a condition to be driven.
Many purchasers of motor cars who pay a visit to the Exhibition promoted by the Society of Motor Manufacturers and Traders (SMMT) at Olympia will find more than six hundred cars or chassis on view, and will have considerable difficulty in arriving at a final choice, for the all-round quality of the exhibits is indeed a high testimony to the skill of the motor car builders. If it is true that noise in mechanical devices means wear, then next year's petrol engines ought to have a life such as no internal combustion motor hitherto built has enjoyed. We are not sure that too much fuss is not being made at the present time on the part of engine designers to obtain absolute quietness of operation. A modern well-designed four-cylinder engine with poppet valves, making its normal number of revolutions, is audible only by the clicking of the tappets and valve spindles, and such a slight noise is somewhat akin to the ticking of a watch. Next year, however, even this is to be subdued by some makers. Many of the devices whereby this end is obtained are doubtful improvements.
As we pointed out last week, the Finance Act of 1910 has given rise to considerable modifications of cylinder dimensions in order to obtain the highest possible power with the lowest possible piston area, and it would be no exaggeration to state that by increasing both the stroke and the valve areas, and lightening the pistons and connecting-rods, the power of the modern engine, bore for bore, is nearly twice that of the average engine of three or four years ago. In other words, an engine rated at 16 horse-power now is equal to one of over 30 horsepower made, say, in 1908. To some this might suggest over-stressing, but it must be borne in mind that the materials employed and workmanship have been brought up to a very high quality indeed, while lubricating devices are almost perfection. With oil flowing through bearings at a pressure of 20 lb. to 30 lb. per square inch, wear and tear are greatly reduced.
There are nearly three hundred stands, and approximately one third of the cars shown are of British manufacture. Although, the least expensive petrol car of its size is of foreign manufacture, there arc several English cars which run it close in the matter of price. One of these is illustrated on page 516, and is made by Argylls, Limited, Alexandria, N.B. This is a very pretty model of a chassis rated at 12 horse-power, in which the makers have made considerable departure from their standard practice. One of these consists in the adoption of the worm drive, and the other is the angle of the whole of the motor mechanism which is in direct opposition to that adopted by most makers. As will be seen, the worm is arranged on top of the worm wheel in the back axle, and the front end of the engine is at a lower level than the back. Whether the life and efficiency of a worm drive with the worm on top of the wheel are likely to be as long and as high as when the worm is placed below the wheel, are points on which there are differences of opinion, and we need not stop to discuss them here. Certainly it is not so simple to lubricate the worm when on top as when it is submerged. The engine has four cylinders, 72 mm. by 120 mm., cast en bloc, and the valves are all on one side, being enclosed by a cover. Thermo-syphon cooling is adopted in conjunction with a tube radiator, and all pipes are large. This engine is rated according to R.A.C. formula at 12.9 horse-power. It has Simms' high-tension magneto, and is well lubricated. The oil is drawn from a reservoir forming part of the hose chamber by means of a gear pump, and is led direct to the bearings. A constant oil level for the big ends is assured under all conditions, and in order that the driver may see whether the lubrication is effective, a tell-tale device is fitted on the dashboard. The clutch is of the flat plate, multiple disc type, running in oil, and easy of adjustment. From clutch to gear-box the transmission is effected by a universal shaft fitted with special coupling; from the gear-box to the back axle by a propeller shaft carried by universal joints at the front and rear ends, the whole being encased in a steel torque tube supported at the front end by a shock absorbing device, which, in turn, is carried on a cross member of the frame. As is becoming customary, a range of four forward speeds and reverse are provided, with a direct drive on the top gear. All shafts are carried on ball bearings, with a special device to prevent leakage, and all gears are controlled by one lever operating in a gate quadrant of special design. The front axle is a drop forging of H section with the steering link carried behind the axle. The back axle, as mentioned above, has a worm drive with a floating shaft, fitted throughout with ball hearings. The road wheels are carried on ball races, which, in turn, are mounted on axle sleeves.
The Sheffield-Simplex Company is introducing a 25 horse-power car, in which two new departures have been made. It is a six cylinder engine with cylinders 85 mm by 127 mm, cast in pairs, and, as will be observed by reference to the drawings, Figs. and 8, the engine has one distinctive feature — introduced with the object of producing a silent distribution — namely, a worm-driven cam shaft, oil pump, and magneto. The worm mechanism is enclosed in a separate casing at the forward end of the engine. A worm wheel on the end of the crank shaft meshes with a multiple threaded worm on a shaft set at an angle of 45 degrees, and this worm also meshes with a worm wheel on the single cam shaft to operate the valves. The worm shaft runs in plain bearings, and drives at either end the high-tension magneto apparatus and the oil pump, the thrust of the worm being taken on either side by ball bearings. The magneto is supported on an inclined bracket bolted to the front end of the crank chamber, and is very easy of access. To avoid overhanging drives, the worm wheels are not secured to the crank shaft and cam shaft, but revolve on a sleeve on the gear case, and are operated by dogs secured to the shafts. As at present designed the mechanism seems somewhat bulky, and requires a larger space than usual, but this will probably be reduced in later designs. The system of lubrication of this engine is well thought out, the oil being drawn from a filter sump in the bottom of the crank chamber and is forced through the main passage in the wall of the chamber to troughs below each crank. A sufficient supply of oil is retained always in the distribution gear chamber to immerse the worm. A simple means is provided in the engine crank case to prevent excessive lubrication, which is liable to give a smoky exhaust. With this object a device is provided whereby, when the oil is poured in, a syphon outlet is automatically opened, so that the surplus oil overflows. The clutch is of the multiple disc pattern and runs in dry graphite, a system of lubrication which this firm has found highly effective. The propeller shaft is enclosed in a tube, the forward end of which has a spherical head. This tube serves to take both the thrust of the drive and the torque, and has been previously described by us. The gear-box, which is shown in Fig. 7, is attached to the hack axle, as is the usual practice of this firm. Owing to the power of the engine, however, being less than in their earlier cars, the box contains three forward speed gears and a reverse. Both shafts are hollow, and that on which the sliding gears are placed is "castellated". The shafts revolve in ball bearings, and the gears are operated by two long rods running parallel with the propeller shaft and ingenious tripping mechanism. Reference to Fig. 7 will show that the main driving bevel pinion is carried on the rear end of the intermediate gear sleeve, and the whole runs in ball bearings. No alteration has been made in the Sheffield-Simplex carburetter practice or in the general design of the Lack axle.
The Humber Company is exhibiting three new models, namely, 12-20 horse-power, 16-24 horse-power, and 28 horsepower, all with four cylinders cast in pairs, and four speed gear boxes with three-point suspension. The 12-20 horse-power car has cylinders 90 mm bore by 100 mm stroke, silent chain drives for both the magneto and cam shafts, and flat-seated valves and seatings which have taken the place of the conical types in all powers. The Humber Company has also made a departure in constructing a combined new torque stay and casing for the propeller shaft. In all eases the lubrication of the engine is by forced feed, and the cooling by thermo-syphon. A view of the Humber engine is given in Fig. A.
The Maudslay Company, retains the now well-known hinged lay shaft on top of the engine, the design of which has been further improved by the fitting of a hinged aluminium cover to the shaft, giving immediate access to all working parts. The inlet and exhaust valves are interchangeable and open direct into the cylinder over the top of the pistons. Another good feature of the Maudslay engine is the provision of large inspection doors in the crank case through which all the main bearings and big ends can be examined and adjusted and the pistons and connecting-rods can be removed. The designer has had accessibility in view in designing the live axle, the differential and the whole of the driving gear being so fitted that it can be removed for inspection or alteration without jacking up the car.
Up to last year the Sunbeam Company retained the chain for the final drive to the road wheels, but the demand for a live axle caused it to put on the market a car with the now customary propeller shaft and bevel wheel drive. Now it has gone a step further, and is fitting on next year's cars a worm-driven axle. The worm is carried below the wheel, and is mounted on ball bearings with ball thrusts. Before deciding on placing the worm below the axle, Mr. Coatalen informs us that he made very severe tests with the worm above, and found that the course he has adopted was both the more efficient and more durable method. The gearbox has four speeds, and the engine has forced lubrication through the crank axle. The valves of the engine are placed on both sides, and the engine is cooled by means of a centrifugal pump, honeycomb radiator, and fan. An 18-22 horsepower 6-cylinder engine made by this firm has cylinders cast in triple, 80 mm bore and 120 mm stroke. The design and construction of these cars is very clean and straightforward, but the worm casing comes within 7in. of the ground, which is too close for some countries.
John I. Thornycroft and Co., Limited, is another firm which has adopted the worm drive on the live axle. The chassis illustrated in Figs. 10 and 11 is that of the 18 horse-power car, and has four cylinders en bloc, 102 mm by 114 mm., developing by rating 25.6 horse-power. The engine is lubricated by forced feed, is cooled on the thermo-syphon system with disc clutch and fan combined, and the carburetter is designed that as the throttle is opened the air and petrol supply is increased, thus tending to give a constant mixture to the engine. A further advantage possessed by this carburetter is that by loosening a screw the petrol supply may be varied and the mixture altered to suit climatic conditions. The jet is easy of access for cleaning, and warm air is carried to the inlet pipe through a pipe terminating in a hollow collar on the exhaust pipe, with ports through which the air enters.
Messrs. Lanchester are exhibiting, in addition to their 20 horse-power and 28 horse-power cars of last season, a 38 horse-power six-cylinder model, with cylinders 4in. bore and stroke. The engine is designed on their well known principle, arid gives 38.4 horse-power at 1,400 revolutions. The car has the following features in common with the 28 horse-power chassis:— Six-cylinder engine, silent epicyclic change-speed gear frictionally operated, multi-disc clutch and brake lubricated by pressure, unit system of engine, gear box, clutch and brake, worm transmission. Lanchester system of suspension, location of engine, wheel steering and wick carburetter. The chassis follows the firm’s standard construction, being built up of pressed steel members tied by the petrol tank, which is situated under the driver's seat and forms the main torsional member of the frame. In place of four longitudinal members adopted in previous designs only two members are used which resemble the orthodox channel frames, swept inward in front to give sufficient angle of lock to the steering wheels.
The new 12 horse-power Rover car, fitted with a Knight-Daimler two cylinder engine, is an entire departure from the Rover Company’s practice. The engine has a bore 96 mm by 130 mm stroke, and forms one piece with the clutch easing. The gearbox is now a separate casting attached to an under-frame with universal joints between the back of the clutch and the gearbox. The two engine cylinders are cast together, and the magneto is driven across the front of the engine. The carburetter is of the Daimler multiple jet pattern. Lubrication of the sleeves is effected by pumping from a sump to troughs under the connecting-rod ends, which are fitted with scoops. The troughs can be adjusted to give the correct depth of oil. The clutch is composed of phosphor bronze and steel plates, and the gear-box has three speeds and a reverse. The transmission system comprises a cardan shaft enclosed in a central tube, and worm gearing, the worm being placed on top. The engine, clutch, and gears are all arranged in the same horizontal plane, so that there is very little movement of the universal joint at the back of the geer box. Thee engine is capable of developing 19 brake horse-power.
The Rover Company is also showing an eight horse-power ear fitted with a single-cylinder Daimler engine, 101.5 mm bore by 130 mm stroke, which develops nine horse-power. In this ease the chassis follows the general lines of the ordinary 8 horse-power Rover ear.
The 15-20 horse-power B.S.A. car is in all essential features similar to last year's model, with the exception that it is provided with four speeds, and has a somewhat larger wheel base.
The Wolseley Tool and Motor Car Company, Limited, is exhibiting it 12-16 horse-power four-cylinder, a 16-20 horse-power four-cylinder, a 20-28 horsepower four-cylinder, and a 50 horse-power six-cylinder ear. The six-cylinder engine and chassis are illustrated in Figs. 12 and 13respectively. The engine cylinders are 114 mm bore by 146 mm stroke, and are cast in pairs, all the valves being on one side and boxed in. The normal speed of the engine is 1,000 revolutions per minute, and the R.A.C. rating 48.6 horse-power. The valve cam shaft is driven from the crank shaft by spiral gearing. The transmission is effected by a metal-to-metal multiple disc clutch run in oil, and with a ball thrust. From the clutch the motion is transmitted to a universally jointed shaft to the gear-box. The latter is provided with four gear ratios and a reverse, the third speed being a direct drive. A propeller shaft transmits the power to the live axle through two enclosed universal joints and bevel gearing. Forced lubrication by means of a pump is provided for both the engine and the gear-box. In the latter a neat pump driven from the lay shaft keeps up a circulation of lubricant from the bottom of the box to the top of the gears by means of a series of jets. Cooling of the engine is effected by means of a centrifugal pump and honeycomb radiator in conjunction with a fan flywheel. The front axle is of Vickers axle steel, "I" section, dropped type, with inverted jaw ends, and the swivels are carried in ball bearings. The rear axle is of the live type, driven by bevel gearing, and fitted with ball bearings throughout. Two independent brakes are fitted, one a double-acting metal-to-metal hinged strap brake with positive release acting on a drum fitted to the gear-box countershaft and actuated by pedal, and the second internal enclosed metal-to-metal double-acting shoe brakes operating inside drums on the rear road wheels, equalised to both sides of the car, and actuated by a hand lever through rods. The control is by means of a single throttle independently controlled by a pedal and finger lever. There is an additional lever for altering the mixture. The throttle, ignition, and air levers are mounted on the steering wheel.
Sidney Straker and Squire, Limited, are making one type of car only, namely, a medium powered vehicle of moderate price. The engine has four cylinders cast en bloc, 87 mm. bore by 120 mm. stroke and is rated at 18.8 horse-power. The valves are all on one side and interchangeable. The lubrication of the engine is automatic by means of a gear pump situated in the oil sump, which is formed in the bottom half of the crank case. The five main bearings are lubricated by pressure, a separate pipe being led from the pump to the underside of each bearing. This pump also forces the oil to troughs in the crank case into which troughs dippers on the end of the connecting rods splash. Cooling is effected on the thermo-syphon system. Three speeds and a reverse are provided, and the transmission from the gear-box to the back axle is by means of a long cardan shaft and bevel gearing. The live axle is designed with a special view to accessibility. In order to remove the differential gear it is only necessary to take off the hub caps, withdraw the driving shafts and dogs, take off a door at the back of the case, and remove the bevel wheels.
The Valveless Car Company, which has hitherto only made one power of car, namely, 25 horse-power, is showing a new 15.6 horse-power model. With the exception of the size of engine all the earlier features are retained. The engine has two cylinders, 4-7/16ths in. bore by 5in. stroke, which form one casting with the carburetter. The two pistons drive through their connecting-rods on to separate and parallel crank shafts, the cylinders being offset l.3in. The two pistons have a common combustion chamber and a single sparking plug, and they move down under the explosion pressure simultaneously, the two crank shafts being geared together. There is a fly-wheel at the forward end of the right-hand shaft and another at the rear end of the left hand shaft. The two-stroke cycle of operations is employed, air being compressed in the base chamber, and on the opening of the inlet port in the right-hand cylinder — as viewed from the rear of the car - at the end of the downward stroke of the piston, the air passes through the throttle passage past the petrol jet, thus becoming carburetted, and, entering the cylinder, expels before it the remnants of the exhaust gases, which pass out through the exhaust port in the other cylinder. The air is drawn in round a disc, and passing into the crank chamber, does not take with it any petrol vapour. The gases, on entering the cylinders, strike against the division between the two cylinders, which constitutes a water-cooled baffle. The magneto and oil pump are driven off the transverse shaft in front of the engine. The lubrication is forced through a valveless oil-distributing single-plunger pump to all the main bearings. The throttle is operated by hand and foot and the timing of the magneto is fixed. Cooling is by thermo-syphon system without a fan.
A new model is shown by Sir W. G. Armstrong, Whitworth and Co., Limited. The engine is of very pleasing design, has four cylinders 85 mm by 120 mm cast in one piece and with valves placed all on one side. The lubrication of the engine is by forced feed through the hollow crank shaft, an even pressure being maintained by means of a relief valve, which is set at about 5 lb. to 6 lb. pressure per square inch. Cooling is on the thermo-syphon system, and the clutch is of the multiple disc type, self-contained in an oil tight gear case, and can be removed without disturbing the engine or gear-box. Four changes of speed are provided, the direct drive being on the top speed. From the gear-box the transmission system consists of a cardan shaft and bevel gearing.
Owing to the extraordinary success which has attended the Clement Talbot cars, special reference is due to those exhibited. These comprise cars of four powers, namely, 12 horse-power, 15 horse-power, 20 horse-power, and 25 horse power. The first, second and fourth types have four-cylinder engines, and the third has six cylinders. The engines have all long strokes, so that although the rating is low the actual brake horse-power given off is comparatively high in all cases. In the 12 horse-power car the cylinders are cast in pairs and have a bore 80mm. and stroke of 120mm. The valves are all on one side, and the water pump and magneto are placed at the front of the motor and are driven by a cross shaft with skew gearing from the crank shaft. The gear box contains four sets of gears and a reverse, with the direct drive on the top speed, and the transmission system from the gear-box comprises the usual cardan shaft and bevel gearing. A tubular sleeve surrounds the cardan shaft, and serves as a torque rod; radius rods are also provided. The 15 horse-power car has its four cylinders cast in pairs; they measure 90 mm. by 140 mm. The 20 horse-power car has six cylinders cast in pairs, each 80 mm. by 120 mm. The 25 horse-power car has four cylinders cast in pairs, with a bore 101.5 rum. by 140 mm. The transmission system is on similar lines in each case.
The Arrol-Johnston cars of to-day offer a very striking contrast to those of ten years ago. The modern car has front wheel brakes, an engine and gear-box en bloc, four-speed gear-box, and enclosed valves. The 15.9 horsepower car has four cylinders cast in pairs, 80 mm. diameter by 120 mm. stroke. The valves are all on one side of the engine and are operated by a single cam shaft. The cooling is by thermo-syphon and a steel fan attached to the fly-wheel. The clutch consists of three metal plates held in frictional contact by spring pressure and working in an oil bath. The whole can be dismantled without removing any part of the engine or gear-box. The connection between the clutch and gear-box is by means of a detachable coupling. This coupling is rigid, a feature that is rendered practicable by the system of carrying the engine and gear-box upon a machine-faced aluminium bed giving correct alignment. A cardan shaft with one universal joint at the front end transmits the power from the gearbox to the live axle.
The Vauxhall Motor Company shows cars of two powers, namely, 20 horse-power and 30 horse-power, the latter having six cylinders composed of two groups of three cylinders each. The cylinders are 90 mm. bore by 120 mm. stroke, and the valves are all on one side. They and their tappets, springs, &c., are encased by readily detachable doors. The front cross member of the car frame is so dropped that the cam shaft, bearings, and half-time wheels may be withdrawn. The crank shaft is supported in seven white metal bearings, the bolts which hold the bearings in place passing through the top of the crank case, whose material is thus held in compression. The clutch is a simple metal cone. In the lubrication system oil is carried in a sump in the crank-case under-cover. A plunger pump, driven by a ball-bearing excentric on the rear end of the cam shaft, dips into a filter chamber in the sump, and draws up oil which is forced through a main oil pipe and seven branch pipes to the main crank shaft bearings, and thence through the hollow crank shaft to the connecting-rod big-ends. The entire pump and its valves can be readily detached. A pressure gauge on the dashboard indicates the pressure existent in the lubrication circuit, and a little metallic "tell-tale" rises and falls in a slot on the dash with every stroke of the pump. The level of oil in the sump is indicated by a float fitted at the rear end of the crank case, easily seen when the off-side flap of the bonnet is loosened, and the sump may be replenished with oil when necessary by means of a filling plug on the crank case door. For the gear wheels in the Vauxhall cars nickel chrome steel of remarkable qualities is used. It has an ultimate tensile stress of 108 tons per square inch, elastic limit 102 tons per square inch, and an elongation on 2in. of 15 per cent.
On the Napier cars a new gate quadrant has been introduced, for which it is claimed that although when on the top gear no gears are in mesh, yet on changing to the second gear the gear on the lay shaft is brought into mesh without any jar or noise. On the top gear the countershaft of the gear-box is stationary, and the movement of the gear lever from the top to the second gear slot starts up the countershaft to its correct ratio of speed by placing a pinion into mesh, thus making it quite easy for the second speed wheel to engage.
Mention should not be omitted of the "weight" hydraulic brake system shown on the stand of Messrs. Hill and Boll. In this mechanism the brakes are applied to all four wheels of the car. The fluid is contained in a small reservoir to which are attached two small pistons. This part of the apparatus is attached to the chassis under the footboards, and is directly under the foot brake pedal. The two cylinders referred to are in their turn connected by means of steel tubes to four smaller cylinders placed inside the brake drums of the wheels. One of these cylinders supplies motive power to the front brakes and the other to the rear brakes. The two pistons are connected directly to the foot pedal, and as the whole system is full of oil or other liquid a depression of the pedal causes the plungers in the brake cylinders to be forced out equally, and thus apply the brake blocks. The whole device is simple, and has the advantage of giving equal retarding pressures on all wheels.
Another ingenious device shown, and one of which more is likely to be heard, is the Cowey suspension system. This was shown last year, but has since undergone improvement. On a car fitted with this device the springs are entirely removed, their places being taken by four self-regulating pneumatic cylinders and pistons, which are supplied with air at a sufficient pressure to maintain the car in its normal position. The air within the cylinders acts upon the top of the pistons, which, through the intervention of pivotally mounted piston- rods, bear down upon the axles, and so support the car. The axles are kept in proper position by means of radius and tie rods. Each cylinder is open at its upper end to a large chamber which surrounds it, the capacity of this chamber being so large in relation to the area of the piston that time upward or downward movement of the latter makes no material difference to the pressure of air contained in the cylinder. Consequently the supporting force due to the intervention of the compressed air between the piston and the cylinder with its surrounding chamber remains practically unaltered by the movement of the piston.
In our review of the exhibits at the above exhibition last week we alluded to the growing tendency on the part of motor engineers to adopt pitch chains for operating the engine cam shafts. In addition to the English engines mentioned, there are one or two of foreign manufacture in which this innovation has been introduced, notably the La Buire and the Germain. In the latter case the valves are all on top of the engine, and are operated by a cam shaft, which is driven by a silent chain from the magneto shaft, the latter being first driven from the crank shaft in a similar manner. The cam shaft operates the valves through rocking levers, which are easily removable to give access to the valves, and are provided with rollers where they come in contact with the cams. On one end of the cam shaft skew gearing is provided to operate the oil pump for the lubrication system, while it also operates a small air pump to maintain pressure in the petrol tank.
The six-cylinder La Buire engine has the valves all on one side, and the cam shaft is driven by a silent chain from the crank shaft. A centrifugal pump for the circulating water and high-tension magneto are mounted on each end of a transverse shaft driven by skew gearing from the forward end of the cam shaft. The lubrication is effected by means of a gear pump in the base chamber, which supplies oil to lipping troughs for the connecting-rod ends.
The illustration above represents the 15.9 horse-power four-cylinder Arrol-Johnstone engine, clutch and gear-box, to which we alluded last week. Although to all appearances these form a single unit either of the three parts can be readily detached. The four cylinders, 80 mm. and 120 mm., are cast in pairs. The size of the pipes for thermo-syphon cooling is large, the large inlet passages being connected by an india-rubber ring and clip. The magneto high-tension shaft is driven by skew gearing from the crank shaft on the opposite side to the valves. The fly-wheel has on its periphery steel fan plates and the clutch is of the plate pattern. The car is fitted with a dashboard radiator to which an ample air supply is provided through the semi-circular extension of the base-plate shown. The gear-box is provided with four speeds, the wheels of which are in constant mesh, and are of the helical type.
Note: The illustrations referred to in this article are published on the relevant company pages