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Motor Carriages and Chassis - Details in report.
Carriage Bodies and Body Work - Details in report.
The eighth International Exhibition of Motor Cars which opened to-day at Olympia under the auspices of the Society of Motor Manufacturers and Traders (SMMT) bids fair to exceed in importance any of its predecessors. During the past year structural alterations have been made in the building known as Olympia, the large annexe having been thrown into the main hall, with the result that a much more effective display of the vehicles is possible. Over 300 firms are represented in the hall, and there are probably about 600 cars on view, in addition to engines, ignition apparatus, lamps, tires, clothing, &c. The success of these annual shows is the more significant in view of the fact that no exhibition of this sort is this year being held on the Continent, and it would appear that London will be looked upon as the motor mart of Europe at any rate. When it is considered that the first show of motor cars in this country was held only as recently as 1902, the tremendous strides which the industry has made is realised. At that show there were less than 100 exhibitors, and foreign-made cars preponderated.
At the present show British exhibitors are in a large majority. Although the trend of motor car construction presents no startling departure this year, except in the one direction of the elimination of the tappet valve engine, many new objects of interest are on view among the accessories and tires. In wheel construction a decided tendency prevails to discard wooden wheels and take up wire wheels, which when properly designed can be made quite as rigid as the former, while very much lighter, thus enabling motorists to carry among their equipment a complete spare wheel in place of spare tires and rims. Many makers are, indeed, now adopting the wire wheel as their standard. We shall have something to say next week on the principal features of the show, which remains open until Saturday, November 20th.
Although, as we mentioned last week, distinctive departures in motor car design are this year comparatively few, there are noteworthy exceptions. The "Silent Knight" engine, which created a mild sensation at last year's show, seems to have confounded some of its critics, and has set a new fashion in automobile engines. The Daimler Company has reaped the benefit of its enterprise in making such a pronounced departure from the orthodox petrol engine practice. This year, in addition to the sliding sleeve, we have the choice of several distinct types of piston valve engines, all of which have certain merits. There is also an ingenious hydraulic transmission system by means of which the whole of the gear box, with the exception of reversing gear, has been swept away.
Steam propelled cars are confined to the stands of three well-known firms, while electric vehicles are scarcely represented at all.
With regard to the general design of petrol vehicles, there is an obvious increase in the number of car builders who are taking up the worm drive, which has hitherto been chiefly used in the Lanchester and Dennis cars. Although a well designed and efficiently lubricated worm gear provides a drive which is both efficient and silent there may be other reasons for the increasing popularity of this form of transmission, which is certainly as expensive, if not more costly, to produce than the bevel gear. There are rumours of threatened litigation on behalf of owners of master patents which may have something to do with the change of front. Hitherto one of the chief obstacles which the builders of the worm-driven motor car have had to overcome has been the cutting of a worm to the correct form to allow the wheel to drive the worm, as is necessary in running down hill with the clutch out. This has, however, been overcome, and there is no reason why the worm should not continue to grow in popularity.
In the matter of engine design there is a decided lengthening of the strokes this year, and the adoption of light steel pistons in the place of those of cast iron enables the piston speed to be correspondingly increased. Many of the next season's engines will have their valves, stems, springs and tappets boxed in, which is a good feature, as it serves both to quieten the working of the engine and to exclude dust. Forced lubrication by means of geared pumps is very general, the oil being sent through the crank shaft to the big ends and sometimes to the gudgeon pins.
For ignition purposes the accumulator has fallen further into the rear, and the magneto is now considered quite a necessary feature of a modern car. The dual system embracing both the above is in all cases worthy of adoption. In clutch design there is no material change to record, but the pitch chain is falling further into the background for transmission purposes. With regard to the suspension of the chassis, the most popular system of springs seems to be the semi-elliptic on the front axle and three-quarter elliptic on the driving axle. In the case of the new Deasy motor car, however, the Lanchester system of rear springing has been adopted in conjunction with a three-quarter elliptical spring on the front axle.
The Hewitt piston valve engine illustrated in Fig. 1 will appeal to marine engineers. It has four cylinders, and it works on the four-stroke cycle, having exhaust and inlet piston valves, which reciprocate in water-cooled sleeves, being operated from a half-speed auxiliary crank shaft. The valve liners are open on top to the combustion space, and at about the middle of their length have a ring of ports which lead into a surrounding water-jacketed valve chest. These ports are uncovered by the valve piston at about three-fourths of its upward travel, and are opened and closed in exact proportions to the suction and scavenging action of the main piston. It will be understood that the inlet ports are never exposed to the heat of combustion. The exhaust ports are water-cooled ingeniously in order to prevent heating and burning of the edges. A feature to which the makers attach much importance is the arrangement of the valve piston rings, which are concealed during the time of highest compression and firing. At the time of firing the exhaust piston valve shown in section in the figure is already travelling outwards, and continuous to do so at its maximum speed during the whole of the working stroke, so helping the expansion of the spent gases, and producing quietness of operation. The valve crank shaft is driven by means of spur gearing from the main crank shaft, and it is claimed that the exhaust valves receive impulse from the gases, and thus help to drive the engine. The valves travel at about one-third of the speed of the main piston.
The cylinders are solid-headed, with no caps or water joints, and the valve liners are fitted with ground coned joints. The inlet branch is incorporated in the casting, and the carburetter fits on the opposite side to the exhaust outlets. The crank case is constructed with a large side inspection door, which enables the main and valve pistons, with their connecting-rods, to be removed. A system of forced lubrication is provided. The engine is made by Davy Engineering, Limited, Hulme, Manchester, under licence from Hewitt Engines, Limited.
Another piston valve engine is shown by the firm of G. H. Bentall and Co., Limited, Heybridge, Maldon. This engine is built on C. Bingham's patent, and forms quite a now departure, as will be seen from Fig. 2. The distinctive features of this engine are the methods of operating the piston valves by a rotating shaft and rocking levers on top of the engine casing, and the slow speed of reciprocation of the valve pistons. The valve shaft only makes one fourth of the number of revolutions of the crank shaft. The inventor claims that the combination of this slow valvular movement with piston valves and the absence of spur gearing, give to this engine extreme quietness of running, with the minimum of wear and absence of vibration. The whole of the valve-operating mechanism is accessible and runs in a bath of oil, which is maintained at a constant level and runs over into the valve chambers to lubricate the pistons. Another noteworthy, though not entirely new feature of the motor, is the skew gear-driven vertical shaft shown, which drives the magneto, pump, fan, excentric valve shaft and make-and-break mechanism for accumulator ignition when fitted. It will also be observed that the induction and exhaust ports are part of the cylinder casting.
A third novel design of piston valve engine is shown by the Cooper Steam Digger Company, Limited, King's Lynn. This is a four-cylinder vertical motor working on the two-stroke cycle, and its operations resemble very closely those of a locomotive steam engine. The form of construction necessitates the employment of piston-rods crossheads and guides and piston valves, but there is an absence of separate cylinders for air pumps, pressure in the crank chamber, special carburetters, &c. The crank side of each piston and cylinder is employed to provide a charge of mixture for the upper side of the piston at each revolution, and thus, as there is an actual impulse at every revolution, the thrust is always in one direction, while the employment of four cylinders gives a nearly constant torque on the crank shaft. The broad principle on which the Cooper engine operates is as follows: — On the "up" stroke of the piston B — Fig. 8 — carburetted mixture is drawn direct from the carburetter into a chamber formed by the under side of the piston B. On the explosion taking place the piston is forced down and drives the mixture from this chamber into a smaller compression chamber G surrounding the valve F, which is in the form of a small piston working in a cylinder. Here the mixture, owing to the difference in area of the two chambers, is compressed to a pressure of 6-7 lb. per square inch. At the proper moment when the exploded charge is escaping through the exhaust port the inlet valve piston E descends, and allows the mixture under pressure to enter the combustion chamber through a series of ports or grids in the walls of the inlet valve cylinder. On its return stroke the inlet piston closes these ports, and the main piston rising at the same time, the mixture in the combustion chamber is compressed and fired, thus completing the cycle. In order to prevent the mixture drawn from the carburetter into the reservoir chamber under the piston from being forced back by the downward travel of the piston into the carburetter again, and to allow it to reach the compression chamber, the connecting passage between the three points, carburetter, compression chamber and reservoir, is formed by a small cylinder in which a piston driven from the valve crank shaft forms what is practically a "two-way cock," opening a passage first between the carburetter and the reservoir and then between the reservoir and the compression chamber.
In the sectional illustration of the Cooper engine - Fig. 8 — the piston B is shown on the upward stroke, compressing the charge which has been delivered into the cylinder A, and at the same time drawing in on the underside a new charge of mixture from the carburetter through the passage round the mixture valve F, the passage to the compression chamber being closed. The engine shown is rated at 22 horse-power. It has four cylinders 3.75 in. bore by 4.5 in. stroke. It gives 10 horsepower at 400 revolutions, 20 horse-power at 750 revolutions, 30 horse-power at 1,150 revolutions, and 35 horse-power at 1,400 revolutions.
The Cooper car shown at Olympia has two other features worthy of special mention. One is the provision of two distinct series of gear ratios, and the other is a system of springs which is adjustable according to the weight carried. With regard to the former the desired object is attained by providing the main bevel wheel on the live axle with two rings of gears, which can be actuated by two pinions of different sizes, and either of which can be put in connection with the propeller shaft by a hand lever. This does not, of course, replace the ordinary change speed gear-box, but is in addition thereto. The arrangement is seen in Fig. 4. The propeller shaft A carries a sliding clutch, which is actuated by the hand lever. On the end of the shaft to which the clutch D is secured is a bevel pinion C with eleven teeth, E is a bevel pinion with fourteen teeth solid, with the extension sleeve and clutch F, the shaft of C being free to revolve in the sleeve of E. When the clutch B on the propeller is in engagement with the clutch D and pinion C the lower gear ratio is in use, whereas if B is in engagement with F the higher gear is in operation.
The springing is effected by side and transverse springs, which act independently of each other. The transverse spring is made adjustable by a hand nut and screw. The side springs are of the cantilever type, and are proportioned so as to give smooth motion with light or moderate loads, the transverse spring in such case taking little or no weight. With an increase of load the transverse spring comes into action, the proportion being regulated as mentioned.
The two new car models produced at the works of Crossley Brothers, Manchester, are certain to attract much notice on account of the departures that have been made in the motor mechanism. The two new types are rated at 12-14 horse-power and 18-20 horse-power respectively, and as the prominent features are similar in both cases, we propose to describe only the lower powered car, which will probably prove the more popular in view of the extreme elasticity of the engine, ease of management, and lightness of the chassis. We give herewith illustrations of the chassis, Fig. 5; the engine, Fig. 6; the back axle and brake, Fig. 8; the front wheel brake, Fig. 9; and the clutch, Fig. 10. Dealing with the frame first, it will be seen that this is of pressed steel of amply strong sections, inswept at the front and upswept at the back. Tubular cross members are provided to carry the engine and gear box on the three-point suspension system. That is to say, the unit comprising the engine, flywheel, cradle pit, and gear box is carried on a single trunnion at the front and on a double suspension bracket at the back, being trussed by two short steel rods to the side members of the chassis. The long springs are semi-elliptical in front and three-quarter elliptical at the back, all the shackle bolts being lubricated by grease cups. The whole of the frame is made to jigs. The remarkably large insweep at the front enables a very wide steering lock to be provided. In fact, the car can be turned in a 25ft. circle.
The engine is a praiseworthy example of clever design and high-class workmanship. The cylinders are cast en bloc, and have a bore of 3.125 in. and stroke of 4.75in. Ample water space has been allowed, and the cooling is on the thermo-syphon system. In order to reduce the weight of the reciprocating parts to a minimum the pistons are of pressed steel and the connecting-rods light stampings. These are beautifully balanced, each piston and rod together weighing only 41 oz. Here we have one of the secrets of the silent running of the engine at all speeds up to well over 2,000 revolutions per minute. These speeds coupled with the long stroke enable the engine to develop at least 25 horse-power on the R.A.C. formula. The pistons are long, with three rings above the gudgeon pin and one below. The crank shaft is of a very high grade steel and has five hearings. The main bearings are supported independently of the bottom half of the crank casing, which is removable, and so designed that the shaft, complete with connecting rods and pistons, can be removed without disturbing the cylinders. The removable bottom cover forms an oil sump for the lubricating oil, which is circulated under pressure to the bearings by means of a rotary pump cunningly placed in an accessible position in front of the crank case. The timing wheels are lubricated by a jet of oil which is caused to impinge at the actual point of contact of the teeth. The pressure of the lubricating system can be read at all times on a dial fixed to the dashboard. The valves are of large size. They are all on one side, and are enclosed by an air-tight aluminium plate easily attached and detached. The employment of a high grade aluminium alloy, it may be mentioned, forms one of the conspicuous features of the engine and mechanism. The valve tappets are of unusual design, each tappet containing a dashpot containing oil, and a spring to obviate noise. In the matter of ignition there is little room for failure. The cars are fitted with Bosch high-tension magneto ignition, and the Bosch dual system of accumulator ignition for starting.
The carburetter is carried directly on the induction pipe, and is of the variable jet pattern. It is simple in construction, easy to inspect, and gives a correct proportion of air and gas at varying speeds of the engine. The throttle valve is embodied in the carburetter. The clutch shown in Fig. 9 is of the internal expanding metal-to-metal shoe type. It is light, runs on ball bearings, and can be adjusted for wear in a simple manner. Another advantage is that it can be dismounted without dist mantling the engine or gear box.
The gear box has been reduced to the smallest limits, and is of aluminium, combined with a cradle pit, in which the light fly-wheel runs. The cradle pit and gear box casting are in one, and this casting registers with, and is securely bolted to, the engine crank case casting, consequently the engine and gear box can be erected together on the bench. At the same time the engine and the gear box can be lifted completely out of the chassis independently of each other. The shafts in the gear box run entirely on ball bearings, and provide for four forward speeds and a reverse operated through a pivoted gate by a single change speed lever. The drive on the fourth speed is direct from the engine to the propeller shaft. The drive from the gear box is through a universal joint to the propeller shaft, and thence through a bevel and crown wheel to differential and live axle. At the top of the propeller shaft, behind the gear box, is fitted a universal joint running in an oil-tight box. The propeller shaft is enclosed in a steel tube, the bottom end of which is securely bolted to the back axle casing. The top end of the propeller shaft tube terminates in a spherical ball pivoted concentrically with the universal joint, and forming the oil bath above referred to in which the universal joint runs. This propeller shaft tube consequently takes the thrust from the road wheels as well as the torque from the back axle.
The back axle is arranged so that the whole of the differential and propeller shaft can be removed without disturbing the axle. The two side shafts are splayed and enclosed in taper steel tubes bolted to the central casing. The differential is of the bevel type and the whole of the gears in the back axle run in oil, ball bearings being used throughout. Another unusual feature of the Crossley cars is the absence of brakes on the transmission system. They have instead brakes on the front wheels, designed and made under Allen-Liversidge licence, on the Renouf system, operated by a foot pedal, and brakes on the back wheels worked by hand by means of a side lover. These are shown in Figs. 8 and 10. On the front wheels a brake drum is mounted on the hub. The steering pivot is made hollow, and within it is a plunger, held in position by a spiral spring. Upon this cap the end of a bell-crank lever presses, being actuated by the brake pedal through rods. The depression of the plunger by the bell-crank lever takes effect upon the brake shoes by expanding toggles, with the result that the brake shoes are thrust outwards against the inner periphery of the brake drum upon the pivots. The brake shoes are of pressed steel with cast iron liners. The rear wheel brakes are also of the internal expanding type, the opposite ends of the shoes being each pivoted to an arm on the spring bracket. A rocking collar on the axle casing has two projecting arms — Fig. 8 — connected by links to the free ends of the shoes. The collar is caused to move round the tube by the side lever and suitable connections.
The high quality of the materials employed throughout has enabled the designer to reduce the weight of the parts to a minimum, and the makers are to be congratulated on the production of a car which bids fair to achieve a reputation equal to that of the Crossley gas engines. The Crossley firm is also showing the Cowey system of suspension, in which pneumatic buffers take the place of springs. There are four air cylinders in which are pistons, and the latter are connected to the axles by pivoted rods; and by an ingenious arrangement the pistons are made to adapt themselves to the vertical movements of the axles.
Other unorthodox types of engine which have already been dealt with in these pages, namely, the valveless engine designed by Mr. Lucas, the Dolphin two-stroke engine, illustrated in connection with our show article last year, and the Daimler Company's sliding sleeve engine, seem to have given general satisfaction to their producers. In the valveless engine, which is now built by David Brown and Sons, of Huddersfield for the Valveless Car Company, Hanover-square, W., it has only been found desirable to modify the arrangement of the ports. In the Dolphin engine the single notable alteration is the addition of a water jacket to the pocket at the top of the combustion chamber, while we understand that the system of lubrication of the Knight-Daimler engine has undergone some slight modification.
The Daimler Company has also adopted a new system of spring suspension, in which two spiral springs of different strengths are interposed between the rear end of the back semi-elliptical springs and the dumb irons — an arrangement which is said to give easy riding over rough roads.
A hydraulic system of transmission for motor cars is shown by the Motor Mercantile Association, Duke-street, Grosvenor-square, London. The hydraulic apparatus is shown diagrammatically in Fig. 11. Keyed on the projection B1 of the engine shaft B is a box made in three parts numbered 1, 2, and 3. This box carries the four pairs of blades or impellers A, which can revolve in the bosses E of the carrier. The lower end of each blade is provided with a plate G in which is cut a radial slot. In the latter a pin engages, which is fixed in the endwise sliding box 4, the longitudinal movement being given by the shaft 5. The shaft receives the necessary movement through the pin 6 and the outer sliding sleeve 7. Now the blades are nominally held in the position of maximum drive, which obtains when the angle formed by any two adjacent blades is in the neighbourhood of 180 degrees - or in other words, when their surfaces are practically in alignment. The full movement of each blade corresponds to an angle of 90 degrees, after which the two adjacent blades assume the more or less parallel position. In this position practically no liquid in the casing is displaced, owing to the thinness of the blades, and a neutral position is thus provided. The speed of the vehicle is thus controlled up to a certain point by the hydraulic apparatus. When the engine is running the blades impinge upon the liquid with which the drum is full, and the momentum of this liquid is then absorbed by the drum, the pressure on the drum being equal to that on the blades. For the direct drive a cast iron rim 8 is bolted to the drum, and is provided with three grooves at its internal periphery. Two shoes resting on a carrier 9 attached to the projection of the engine shaft can expand and contract by means of two right and left-hand screws symmetrically placed in relation to the axis of the drum. Fixed on each screw spindle is a short lever 10, which, by means of the adjustable rod 2 and sleeve 7, operates the shoes. The movement of the sleeve 7 is controlled by the pedal, the force exerted by the spring tending to bring the blades in line with the longitudinal axis of the vehicle and to lock the device just mentioned. A downward movement of the pedal first releases the lock, then the blades are moved to suitable angles, indicated on the segment 14. It should be mentioned that the drum C, which replaces the usual gear box, is provided with radial ribs, in order more readily to absorb the whole of the kinetic energy stored up in the liquid. To obtain a reverse motion an epicyclic gear is placed behind the hydraulic drum. The introducers of this system claim that, besides obtaining an appreciable increase in torque, it adds greatly to the elasticity of the transmission, and that the fly-wheel effect is increased owing to the kinetic energy of the mass of the revolving liquid. The efficiency of the transmission requires that the whole of the momentum of the liquid be absorbed by the drum, which can only be obtained when the speed of revolution of the latter is one-half that of the engine.
Last week we referred briefly to the Cowey pneumatic suspension system which was shown applied to cars made by Crossley Brothers, of Manchester. The aim of this system is to obviate the employment of springs, and to do this the inventor introduces four vertical cylinders fixed to the chassis frame. These cylinders each contain a piston, which is coupled to the axle, and the cylinders are charged with compressed air from a common reservoir, the latter being in turn charged by a pump driven by the engine. The cylinders contain a combination of piston, spring, and sleeve in order to allow the appliance to differentiate between movements due to road shocks and those due to variations of load. As the pistons and cylinders do not give the necessary lateral rigidity, longitudinal and transverse radius rods in front and at the rear are necessary, and these are loaded with springs to yield to the vertical movements of the piston-rods.
A notable feature in connection with the latest designs of motor cars is the growing tendency to place the radiator behind the engine, as in the case of the well-known Renault cars. This is advantageous for three obvious reasons. First, the radiator is placed in a position of greater security against damage; secondly, it enables a more pleasing contour of bonnet to be provided; and thirdly, the dust laden air induced by the fan has not to pass round the engine. It is drawn in to the radiator from without the bonnet, and after passing round about the tubes is discharged below the framework of the car.
One of the greatest drawbacks to the employment of chain driving for motor cars has always been the difficulty in connection with lubrication. Most firms did not think fit even to protect the chains from dirt and grit. The Sunbeam Motor Car Company has adhered to the chain drive after all other firms have discarded it, and for rough roads the decision has been amply justified. In the Sunbeam car the chain has always received the protection which it requires equally with the other working parts of the mechanism. By enclosing it in a dust-proof oil-tight case, and providing the necessary lubrication, this form of drive has been so satisfactory that the makers of this car until this year saw no reason to place before their customers an alternative drive. This year, however, conforming to fashion, a live axle car has been produced, the keynote of which is simplicity. The illustration, Fig. 12, represents the chassis of the 12-16 horsepower live axle car. The engine is of new design, and has four cylinders, 80 mm. by 120 mm., cast in pairs. The inlet and exhaust valves are on opposite sides, and are enclosed by dust-proof metal covers which are easily detached by hand. The connecting-rods are steel stampings of H section with white metal bearings. The crank shaft also runs in white metal bearings, and the lubrication of those and the big ends is effectively carried out by means of a gear driven pump, thus ensuring a constant supply of oil, which returns to the reservoir in the crank chamber, and, after being filtered, is usable again. The bottom of the crank chamber can be removed without disturbing the crank shaft. The ignition system is the high-tension magneto with fixed or variable timing as desired. The engine is controlled on the throttle valve — which is combined with the carburetter — by means of a foot lever. The carburetter is of the Claudel-Hobson pattern. The clutch is of the leather faced conical pattern, self-contained, and giving no end thrust to the crank or gear shaft. It is easily adjusted. The gear box provides four forward and one reverse speeds, and is suspended at three points. All the shafts run on ball bearings and are short and rigid. The live axle is of simple and straightforward design with bevel gears. Ball bearings are provided throughout, and the wheels are mounted on an outer sleeve, so that the differential shafts do not carry any weight. The brakes are easily adjustable, the front brake being of the external metal-to-metal type, with a large frictional area. The wheel brakes are enclosed in dust proof drums.
Unlike most of the best known petrol car makers, the Sunbeam Motor Car Company believes in forced circulation of the cooling water, and with this object provides a gear-driven pump and honeycomb radiator. A higher powered car built on similar lines and rated at 16-20 horse-power has a four cylinder engine 95 mm. bore by 135 mm. stroke. In both cars the petrol is fed to the carburetter by gravity.
The Rolls-Royce cars exhibited were all of the same power. They had a six-cylinder engine 40-50 horse-power built up of two sets of three cylinders — a feature which this firm claims to have originated. The frame of the chassis has been lowered somewhat, and the gear box is one piece, suspended at three points from the main frame. The gear shafts have been increased in diameter and additional bearings have been introduced. A novel feature is to be seen in connection with the supply of petrol, which is now carried in a tank at the rear of the chassis, where it is suspended from projections on the side members of the frame. The necessary pressure is supplied by means of a small air-pump mounted on and driven from the gear box. The pump is of the piston pattern, and a silent relief valve fitted on the dashboard prevents the pressure from exceeding 2 lb. per square inch. On this relief valve a cock is fitted for releasing the petrol tank pressure at the end of a journey. This system is better than that which employs the exhaust gases to provide the necessary pressure. In connection with the brakes a small differential gear is now used by which the rear wheel brakes are operated, the pressure on the two sets of brakes being thus equalised.
Five distinct models were shown by the Wolseley Tool and Motor Car Company, Limited, Birmingham, namely, 12-16, 16-20, 20-28, 24-30, and 40-50 horsepower respectively. They are all of the live axle type, the drive being transmitted in the three higher powered cars by bevel gearing, and in the lower powers by worm gearing. All have honeycomb radiators and pump circulation, except the 12-16 horse-power car, which works on the thermo-syphon system. The suspension is semi-elliptic on the front axle and semi-elliptic on the rear wheels of the short wheel base cars, but for cars with a long wheel base an additional transverse spring is fitted. All spring shackles are fitted with means for lubrication, and multiple disc clutches are used throughout. A double universal joint is fitted in each case between the clutch and gear box, and there is a universal joint at each end of the propeller shaft. Each joint has provision for lubrication and adjustment as required. The smallest model, rated at 12-16 h.p., has a four-cylinder engine 3.125 in. by 4.5 in. bore. It is constructed with the finish and accuracy which has always characterised this firm's work, the same high-class materials being employed. The engine and gear box are mounted on an under-frame, and the live axle is worm driven, the worm being placed underneath the worm wheel. To reduce to reasonable limits the angle of the universal joint to the propeller shaft, the under-frame is sloped from the front to the rear. On all models the carburetter is of the two-jet pattern, being practically two carburetters controlled by the same throttle. The small one, which has a mixture pipe varying from 0.375 in. to 0.625 in. bore on the different models, is used for starting or very slow running only, when the main carburetter is entirely cut off. The continuation of the movement of the throttle opens the main carburetter.
A point of interest in connection with engine design is the system of lubrication. The troughs under the "big ends" are supplied with an excess of oil which overflows the sides, all that is not taken up by time bearings finding its way back again to the sump, whence it is again pumped through the bearings. Another neat feature on the pressure-fed models is the combined oil and air pump, one for lubricating purposes, and the other for supplying petrol to the carburettor. The 40-50 horse-power six-cylinder engine has all cylinders cast en bloc. These are enclosed in a sheet copper jacket hammered to the desired shape, and fixed on with little screws. The object of casting the cylinders in one is to increase the stillness of the engine and reduce the length, as the valves are all on one side. One train of gearing serves to drive the fan, the water pump and the magneto, jaw coupling being introduced between each to facilitate dismantling.
The Aster Engineering Company showed a 12 brake horse-power Allsop paraffin engine, the design of which has undergone considerable modification since the original engine was described in THE ENGINEER, June 21st, 1907, as will be observed from the accompanying illustration — Fig. 13. This represents a transverse section taken through the pump cylinder. The two working cylinders are 105 mm. bore by 120 mm. stroke, and they have a fuel vapour pump cylinder placed between them. The function of this cylinder is to prepare and supply measured charges of combustible gas into the motor cylinders, and the operations are as follows: — On the down-stroke of the piston paraffin, with the necessary volume of air, is drawn into the cylinder through an atomising valve A, and a vaporising cone B heated by the exhaust gases, and is thereby converted into a gas. On the up-stroke of the piston the vapour is discharged through a superheater at C alternately into the right and left hand cylinders, taking along with it the air necessary for combustion. The gas outlet from the pump cylinder is regulated by a mechanically operated valve of variable lift, which is under control while the engine is running. All the valves are mechanically operated, the inlet and outlet being on either side of the engine. Forced lubrication at slight pressure is provided for the big ends and bearings. The engine gives 12 brake horsepower at 1,200 revolutions per minute and weighs 3 cwt. 9.25 lb. without fly-wheel. It is being built for the Allsop Motor Syndicate, Limited, 59, Queen-street, Cardiff.
Considerable attention is now being given to the production of a satisfactory detachable road wheel. The Riley Cycle Company, Limited, Coventry, exhibited at Olympia a system which is equally applicable to both wood and wire wheels, and which permits a permanent exchange to be made with the spare wheel quickly without disturbing brake fittings, bearings, speedometer rings, &c. Neither the front nor rear axle is changed in any way, but they are provided with inner hubs fixed as usual. Permanently fitted to these hubs are the brake drums, bearings, and other apparatus. The outer or removable hub, which is built up into the road wheel, slides over the inner hub, tapered projecting studs on which engage with corresponding holes in the outer hub, thus transmitting the drive. Each wheel is provided with a special hub cap, which is permanently attached but free to rotate, and is threaded to screw into the inner hub. Enclosed in this cap are automatic locking and withdrawal devices, which provide the means for taking off or putting on the wheel and for automatically locking the hub cap on its thread.
Drummond Brothers, Limited, Guildford, are making a speciality of machine tools suitable for motor car repairers. At Olympia this firm exhibited a really handy universal grinding machine, which is capable of grinding cutters, flat grinding, parallel and taper, outside and internal grinding, and can be driven by power or foot pedal. The bed is carried on heavy standards, and has a long slide, driven by skew and worm reducing gear and hand wheel. The feed motion has stops in both directions and fine adjustment. On the travelling slide is a swivelling table graduated in degrees for taper work, and carrying a headstock with a hollow mandril. This is coned and split at both ends, and has two internal coned sleeves for holding chuck mountings or gripping the work. This head rotates, and the driving gear can be thrown out to leave the spindle free for testing work, &c. The grinding head can be raised or lowered and swung round parallel with or at any angles to the table by weans of a screw and nut. The hand wheel has worm teeth cut on its periphery with which a worm can be caused to gear for fine measurements. The abrasive wheel is driven by a round belt from the treadle motion, the arrangement of the drive being very similar to that on a radial foot-driven drilling machine which this firm introduced recently.
The illustrations referred to in this article are published on the relevant company pages