THE MODERN MOTOR CAR. ITS PRINCIPAL FEATURES BRIEFLY DESCRIBED.

Progress, Volume I, Issue 5, 1 March 1906, Page 110

THE MODERN MOTOR CAR. ITS PRINCIPAL FEATURES BRIEFLY DESCRIBED.

The Transmission. Considerable variety is evident in the method of transmitting the engine power to the road wheels, or, as it is termed, the transmission gear. The majority of cars, however, employ either side chain transmission, generally called the " Panhard " type, or the cardan shaft transmission. In the first system power is conveyed by a longitudinal shaft and bevel gearing to a transverse or cross shaft. At each end of this shaft chain wheels are fitted, the drive then being by chain to another and larger chain wheel bolted to the driving wheel. Each driving wheel is so fitted, the wheels being independent of each other and free to revolve on the stationary axle. Amongst cars using transmission with side chains as in fig. i, are the Albion, Beaufort, Brooke, De Dietrich, Durkopp, Fiat, German, Gladiator, James and Brown, Leon Bollee, Maudslay, Mercedes, M.M.C., Napier, Panhard, Peugeot, Pipe, Daimler, Star, Sunbeam, etc., In the other system what is termed a " live " axle is used, i.e., the axle and two driving wheels all revolve together, the engine motion, as before, being transmitted by a longitudinal shaft and a bevel gear. Cars using cardan shaft or " live " axle drive, as in fig. 2, are the

Argyll, Ariel, Belsize, Clement, Decauville, De Dion, Dennis, Darracq, Elswick, George Richard Brasier, Humber, Renault, Ryknield, Simms-Welbeck, Speedwell, Spyker, Swift, Talbot, Thornycroft, Vulcan, etc. Another system is the chain drive with countershaft, as in fig. 3, which is found in the Siddeley, Wolseley, Belsize Junior, etc. Fig. 4 illustrates the direct drive with central chain from the engine to the back live axle. This system, which is used on the Cadillac, Duryea, Ford, Oldsmobile, Rational, Vauxhall, etc., gives a very high efficiency.

Carburetters. The carburetter, or mixer, sometimes termed the vaporiser, is the arrangement for mixing the gas vapour with the required quantity of air, and delivering the proper quantity of correct explosive mixture to the engine according to the speed and power called for. What is known as a surface carburetter is simply a form of tank in which arrangement is made for drawing m-coming air either over or through the petrol. This type of carburetter is now practically obsolete, the spray carburetter, sometimes called the float feed, being generally employed. The chief advantage of the spray carburetters is that they can be adjusted to use petrol or alcohol of any density, or even paraffin, after preliminary warming by a few minutes on petrol. The worst fault with this carburetter, unless provided with an auxiliary air-inlet, is that it will not generate the mixture in constant proportions at varying

speeds, giving too rich a mixture at high speed, which, if corrected, renders the mixture weak at low speeds.

Ignition Systems. For firing or igniting the explosive mixture of gas and common air in the combustion chamber of a petrol engine, electric methods are now exclusively employed. Of these the most generally adopted is the high tension or battery method, in which a lowtension current generated by a chemical battery, or stored and drawn from an accumulator or storage battery, is transformed by means of an induction coil into a current of extremely high voltage, and consequently possessing the power to overcome high resistances such as that formed by the air-gap at the sparking plug points. The sparking plug is built up m many forms, but all consist of a small central rod or wire ; to one end is fixed a terminal, to which the high tension wire from the coil Is attached. This central core is passed through a tube of porcelain mica asbestos, or other non-conducting material capable of resisting great heat. The core and its insulating tube are fastened into a socket which m turn is screwed into the combustion chamber. The current from the high tension coil flows down the centre conductor, finds itself compelled to jump the small gap between the points of the plug, causing the spark which ignites the gas. In ordinary high tension ignition there is, of course, considerable timelag between the making of the contact in the primary circuit and the rise of the magnetic flux m the coil sufficient to draw the trembler and break the circuit, whereupon the ignition spark occurs, and it is principally this time-lag that makes it necessary to provide a means of varying the time at which the primary circuit is closed, or, m other words, providing a means of compensating for this time-lag. As everyone is aware a careless driver can set up enormous strains on the crank shafts and other parts of the engine by running an engine with the ignition set too early, as many broken crank shafts have testified.

The Timing Gear. An important factor m controlling the efficiency of the petrol motor is the correct working of the timing gear. As only one explosion takes place for every two revolutions of the flywheel which is attached to the mam crank shaft, a second shaft, called the half time shaft, is used for the purpose of opening the inlet and exhaust valves. This is connected by °-ear wheels to the mam crank shaft, the gear being so proportioned that it revolves only once while the mam shaft revolves twice. Both inlet and outlet valves consist of a disc with a bevel surface, fitting into a circular hole, which leads into the ' combustion chamber. Through this disc a stem projects downwards and rests on the tip of a rod placed in such a position that the lower end of it is thrust up by the projecting part of the cam passing under and allowing it to drop again, when it seats itself by means of a powerful spring. With every revolution of the half time shaft this operation is repeated, so that the inlet and exhaust valves are opened and closed once for every two revolutions of the flywheel. The two valves are similar in construction, but the cams which work them are set m opposite positions on the half time shaft, so that the inlet valve is open only during the induction stroke of the engine, and the exhaust valve is open only during the exhaust stroke, so that the back pressure that would otherwise be caused by a cylinder full of gas is averted.

Governing. With regard to system of governing, one method is to vary the amount of lift on the inlet valve itself. This method, however, reduces the compression, and therefore the economy of the motor. Another method is to vary the lift of the exhaust valve, thus retaining more or less of the exhaust gases in the cylinder, which prevents a fresh charge from entering until they are expanded below the atmospheric pressure. In either case the centrifugal governor is used to vary the lift of the valves. A device called the accelerator is fixed m some cars to cut out the governor and render it inactive. The speed of the engine is then increased above normal.

Change Speed Gear. The gear box, after the engine, is a very important part of the car, but has been a weak hnk m a good many. When correctly designed and constructed of the right material it should give no trouble whatever. All kmds of devices have been made to obtain a variable speed ratio between the engine and road wheels, but the Panhard system is one of the most popular. The disadvantage of the Panhard system is the liability, not only of novices but also of skilled drivers, to miss their gear, — i.e., they do not make the desired change when they endeavour to do so, and have to come down to lower gear than that required. This usually happens on an uphill grade. With most forms of sliding gears it is necessary m changing to pick up any intermediate gear that may come before the desired

one. For instance, if when running on the fourth speed it is necessary to stop for any reason, such as the traffic or a restive horse, and it is necessary to get into the first gear to start again, the driver has to get into his second gear, then out of that into his third, then out of that into the fourth, in some cases a most troublesome proceeding. To get over this difficulty good designers are arranging their change gear so that the driver can pass from one speed to any other without passing through intermediate gears. Motor-car owners are quick to see the value of a simple and reliable transmission gear, and, consequently, the Argyll system has a large share of the public favour on that account. No gear wheels-

have to be thrown into mesh, and the necessity of crossing through gear wheels m passing from a low to a high set is quite done away with, besides which a neutral point is given between each of the three forward speeds, and, most important of all, the Argyll has an arrangement of levers by which the novice operator will not spoil any of the wheels by the inevitable mistakes made when learning to operate, or in putting into operation the wrong set of speed wheels Further advantages in these gears are . — no notches to find in quadrant, gears cannot bind, if car stops while changing, it is impossible to put in the reverse by mistake, direct drive on the speed, exceptional accessibility, changes are made without clatter or noise.

Differential Gear. The differential gear appears to mystify most people, and is one of the least generally understood parts of the power-transmitting mechanism of a motor car In a car having side chain drive this gear is situated on the countershaft carrying the sprockets. In a gear driven car it is usually located at the centre of the live back axle. Its object is to vary automatically each driving wheel's relation to the other, according to the requirements of the moment. The car never proceeds far in a straight line, but is either owing to turns in the road or the necessity for avoiding traffic, constantly describing a series of curves. Now, it can be easily seen that the

A Universal Sliding K3 2nd Speed Clutches Coupling L Actuating Fork B Mam Shaft {Mam Shaft) C Counter Shaft Li Actuating Fork D Brake Drum and (Counter Shaft) Sprag Ratchet M Ist Speed Bell Crank E 3yd Speed Pinion and N Sprag Ratchet Shaft O 2nd and ird Speed F Ist Speed Wheel Bell Crank G 2nd Speed Wheel P Clutch Shaft H Counter Shaft Speed Q Bearing Joint Bolts Wheel A 1 Reversing Pimon I Ist Speed Pinion Bi Gear Box Cover ] 2nd Speed Pimon Ci Reversing Spindle X 3rd Speed Clutches Di Gear Box Cover Xi yd Speed Engaging Clamps Clutches Ei Gear Box K2 2nd Speed Engaging Clutches

wheel which for the time being is on the inside of the curve, has a shorter distance to travel in a given time than its fellow on the outside, and consequently requires to run at a slower speed, or, like the man at the inner end of a rank of soldiers when wheeling, to " mark time." Where both wheels are rigidly connected and unable to turn independently, one or both must slip on the road surface, to the destruction of the tyres and the discomfort of the passengers. The tendency has been to make these differential gears too small for the work they are called on to perform, but this defect has been remedied in most cars.

Water Cooling. Some system of cylinder cooling is necessary to the propsr working of the petrol engine. Cooling may be by air or water. Air cooling, which is only used on small-powered engines, may be by simple radiation (as on the motor bicycle), or by a forced draught from a fan or scoop arranged to supply a current of cold air to the outside of the cylinder and combustion chamber. Water cooling is effected by causing a constantly moving or circuating body of water to flow through an outer chamber or jacket surrounding the cylinder and combustion chamber. In gravity, or thermo, feed, a tank is placed above the water jacket ; as it is heated by the engine it rises, and emerging from the top, finds its way through radiators back to the tank. Forced circulation by pump, however, is preferable. Sometimes it is so arranged that if the pump fail, natural circulation will take place. It is possible to keep the water too cold. If the temperature of the water is below that at which the vapour is formed, a large proportion of the heat generated by the combustion goes to heat the cylinder walls. The circulating system should be designed to prevent air locks, and an air cock should be provided at the highest point of the system and a drain cock at the lowest, so that for cleansing purposes and in frosty weather the water can be easily run off. The car should have not less than half a gallon of water per indicated horse power. The temperature of the water leaving the cylinder jacket should be about 170 degrees Fah.

Lubrication. Pure gravity fesd consists of a sight feed cup of toughened glass with a metal cap, in which is a little shuttered air-hole, the closing of which regulates the supply through the tube beneath the cup to the part to be lubricated. This is the simplest form of gravity feed. Splash lubrication is very universal for all bearings inside the motor, such as those for the crank-shaft, cam-shaft, and cams enclosed gears and the lower ends of the connecting rods. It simply consists of a bath of oil inside the crank chamber, the cranks dashing the oil over all the working parts. It is a dirty but thoroughly effective system, and is also used for the differential gear and the change speed gearing. In the physical system, means are employed to utilise the pressure from the exhaust or water system ; under this action special means are employed to force the oil along the branch pipes leading from the lubricator. In pressure feed the reservoir may be placed in any position, and below the level of the parts to be oiled. In this case either the oil is forced through the pipes by an automatic force feed pump worked by the engine, or part of the exhaust gas is diverted through a non-return valve into a reservoir, maintaining a pressure on the •oil of two to four pounds, as may be required.

The Clutch. A satisfactory clutch is one of the most difficult -things to secure. The ordinary type of cone cutch, -which is covered with leather, can rarely be maintained in a normal condition, for the following reasons : — A great command over the car, especially in driving through traffic, is secured by allowing the clutch to slip. When the slipping has been going on for some time the clutch will not grip at all, or it grips violently or harshly. The result is that driving is not only most unpleasant, but is very injurious to the car itself.

Frames. The frames are built up in a number of ways. (a) Lengths of channel steel, shaped section, united at the angles of their ends, and cross pieces with strong angle pieces or braces. (b) As described, but armoured internally with ash, which greatly increases the strength with very little weight. (c) Built of ash and armoured on both sides with steel flitches with channel steel arms or cross pieces. (d) Tubing frames screwed into joints which also make joint with cross pieces and stays. (c) And lastly, the one-piece pressed steel frame, perhaps the strongest and lightest of them all. With regard to the wheelbase, the longer this is, the steadier the car, and the greater security from side slips. Greater care must, however, be paid to securing sufficient strength on account of the extra length.

Silencers. A perfect silencer should muffle all exhaust noises without setting up any back pressure whatever. This is effected, first, by gradual expansion in a closed chamber divided up into a series of freely inter-connecting expansion chambers, and secondly, by turning the stream of gases at a right angle to its last direction, and splitting it up into smaller streams.

Brakes. Double-acting brakes are now fitted with a pair of mstal clips arranged about the brake drum, and hinged together at one end. The motion of the brake pedal causes mechanism independent of the remainder of the braking mechanism to close the two halves inwards and grip the brake drum. This arrangement is equally effective in either direction. Expanding internal brakes are coming largely into use, one advantage being that they can be cased in away from the dirt ; but a disadvantage is the adjustment, which is not so easy as external.

Bearings. The types used for motor cars are plain, roller and ball. There is still a diversity ot opinion amongst makers as to the best. For heavy cars excellent results without risks can be obtained from plain bearings, constructed of phosphor or manganese bronze. Roller bearings are usually fixed on back live axles and give good results. With ball bearings there is always a certain amount of risk of a ball breaking and playing havoc with its cone and journal, especially in the case of a wheel hub.

Steering. It is, above all things, necessary that the steering of an automobile be steady, and, m order that this steadiness may be obtained, some device must be employed which inequality of road surface will not affect. This is obtained in practice by employing a worm gear for operating the steering arms attached to the axles of the front wheels. The irreversibility of the worm gearing provides against shock being carried back to the driver, and at the same time the screw action of the worm provides a powerful control over the direction of the wheels. For light cars it is not always deemed necessary to employ such a complicated arrangement, and tiller or side lever steering is fitted.

Spring?. Springs should be designed to swallow and conceal the inequalities of the road, and should rapidly absorb the work done on it while moving rapidly under the force applied to bend it. They should not oscillate much after each road " bump " has passed, and should be deflected through half their working distance when fully loaded. Springs are being made much longer now, which is a distinct improvement. The frame of the car should be slightly higher at the back from the road than the front end, so that when fully loaded the frame should be parallel with the ground. Cars can be made, and are being made, to run on solid tyres with comfort. It is, however, useless simply buying a standard pattern car and fitting solid tyres to it. Makers of pneumatic-tyred cars have counted too much on the tyres for shock-absorbing power.

While it is considered the proper thing to make bitter war on automobiles m the country, the fact remains that no other single interest is probablydoing so much for farmers, the country and all concerned on behalf of good roads as the automobile. A powerful sentiment is being encouraged by automobile owners who have health, influence and ability to hasten the long-needed improvement. There are also inspiring young engineers to make new discoveries in inventions and machinery. Hiram Maxim says • — " No other form of power producing apparatus m existence is as simple in concrete, and few more complicated in abstract have been invented since James Watt's first steam engine. It marks the greatest epoch in mechanics." Steam automobiles were first used on country roads in England nearly three-quarters of a century ago, but it is only since the new inventions for using gasolene and electricity in producing powers that the recent stupendous progress has been made possible. In Europe kings, princes and millionaires have spent liberally to develop the industry in their various countries.

Twelve months ago " stagnation of design " was the stumbling-block of the British motor maker. The tendency to copy a certain type of popular radiator, body, or engine design seriously interfered with originality and invention. We are getting bravely away from this, and the motor engineer and body-builder alike are daring to think for themselves to the great advantage of motor evolution.