CYCLING AND MOTORING.

Taranaki Daily News, 9 November 1916, Page 7

CYCLING AND MOTORING.

NEWS AND NOTES. America is upcoming a nation of motor car owners, and it is estimated that by the beginning 0 f 1917 there will be one cur in the United States for every 25 inhabitants. This means that in January next there will be something like 3,040,CO4 ears in America, the aggregate value of which will be something like £4OO- - The cost of running the cars already on American roads is simply staggering. There are, according to the Government census, 2,445,004 cars in use. At an average upkeep of only £SO each per year the gigantic sum of over £122,250,000 is arrived at and £SO would be a long way under the actual average running costs. The American car industry is now such a gigantic business that we may fairly wonder where it will end.

A very interesting article recently appeared in one of the English Motoring Journals in connection with the most suitable position for the radiator, and the writer, who is an officer on service, strongly advocates the dashboard radiator, which was first introduced on the Renault car and still remains a feature of that excellent type. Though this type of radiator has never come much into vogue, it is used to some extent in France, and also in England. Appearance is one of the advantages claimed for it, but herein we cannot say we agree with the writer of the article. There is one disadvantage which we have experienced, namely, the undue heat behind the dashboard. On the other hand the advantages arc considerable. It makes the engine much more accessible, ft very important matter where adjustments' have to be made, more especially in the case of light ears, where many of the parts are comparatively inaccessible owing to lack of room. The disposition of the' weight also is much better than in the case of the usual type. The radiator in front of the bonnet means coiu'derably increased weight on the front of the car, and this is not to be recommended from various points of view, requiring, as it does, heavier springs than would otherwise be necessary. Both on the grounds of road adhesion and stability, it is better to have the weight further back. If it is too far forward it affects the steering materially. The radiator in front of the engine is now easily the most popular with car makers the world over, but that does not say that this position is the best. The Renault type of radiator has many points in its favor and it may yet oust the present popular type. From the numerous reports that have been received from the Allied front on the Sommc—the scene of the great drive —it is learned that the French have made extensive use of aeroplanes equipped with wireless for the purpose of gun spotting. One report states that a French battery dropped . four shells in sucession on a bridge 14 miles away, the accuracy of the fire being clue to an aeroplane flying above the mark, fitted with wireless equipmocnt. The observer signalled back the effect of the fire to the battery commander with apparently tilling results. Many motorists suffer a certain amount of discomfort from bad: draughts when driving with the wind screen up. The remedy is to slightly open the. screen so as to prevent the inrush of air from the sides. A very slight opening will suffice.

The use nf aluminum alloy blades in the place of wooden propellers on aeroplanes subjected to the terrific heat conditions in Mexico and along the border is being considered at present by American aviators, says the Scientific American. Army airmen have experienced no end of trouble in Mexico with wooden propellers on the machines of the expeditionary forces. The propeller that is to be tried out soon is made of an alloy whose base is aluminum. Tt is planned to cast the alloy in block form and then tool it to the shape of the propeller blade. The core thus formed will be covered over with light sheet-steel. A propeller made after this fashion will be lighter than the present wooden ones, and will net splinter. Whilst it is one thing to reduce weight in car construction with a view to more economical running it is a false move to start cutting out weight in tyres. The stresses on pneumatic tyres are infinitely greater than on any part of a car. The high quality steels, etc., embodied in a motor car have not to withstand the gruelling action that the rubber and fabric in the tyre has to, yet we find some of imported tyres cutting down weight with a view to reducing costs and increasing profits. Take the average motor tyre tube that is imported into this country. Few motoristi take the trouble to weigh the tubes they buy, yet they must realise that the one essential to 'satisfactory tyre service is the use of full weight! thick, high quality air retaining tubes. Tt will come as a surprise to many motorists to learn that most of the imported tubes are from 25 per cent, and upwards lighter than the Australian made Dun lop tyres, and although lighter, consequently costing less to produce, cost the unsuspecting buyer considerably more to buy. The writer had three Sl'i/IOTi tubes recently weighed, a, 'Dunlop weighed 41bs, and two American tubes respectively 2 Jibs and 2}lbs. The Australian production embodying the highest quality and the most up-to-date methods nf construction, is listed at 34.=, whilst the 2.]lh tube is priced at 30s, and the 231b tube at 4fis each. There is such a diffeienco that motorists in this country who favor imported goods may well pause and consider. It's an unsound principle to send our gold out of the country at any time, hut, on the above terms it is ludicrous, A few facts anent the thermal efficiency of the petrol engine will interest motorists. Of the 100 per cent, of heat supplied to an internal-combustion engine, 20 per cent, is converted into work and SO per cent, lost or rejected in friction, cooling water radiator, and exhaust. To convert more heat into work, one or more losses indicated must be decreased. Only a per cent, is lost as engine friction, 41 per cent, is lost to cooling water, and M 4 per cent, rejected in exhaust, and radiation. The. loss of heat to the water-jacket depends on the difference in temperature between the burning gases and eylindei walls, the time the cylinder walls are exposed to the heat of the flame and the amount of surface exposed. If we could maintain the combustion chamber at the same, temperature as the enelossed gases, there would be no difference in temperature and no transmission of heat, consequently no loss to the walls and waterjacket. Such a temperature, however, would not only destroy all vestige of lubricant, but would also melt the cylinder walls and pistons. The time per working stroke in which the difference of temperature exists is decreased by high speed, wherein lies the advantage of high piston speed in an internal-combustion 'engine. The thermal efficiency of big guns lies in the missile speed—nearly 3000 ft per second —while the maximum piston speed obtained in an engine cvlin-

der probably never exceeds 40. and seldom averages over 20ft per second. The requirement of a minimum value of the ratio of the explosion-chamber volume and surface is the reason for valves in the head, but the advantage of multicylinder engines with their high speed, light reciprocating parts, and minimum angular-velocity variation seem to offset any thermal losses due to increased surface per unit of volume, a characteristic inherent in multi-cylinder engines. The possibilities of increasing the thermal ellicicncy of automobile engines by decreasing the<jacket josses, lie then in a high piston speed, a minimum surface per unit of volume, characteristic of the sleeve-valve, and the valve-in-head engines, and as high a compression as possible without spontaneous ignition. Small gains in efficiency have been made by reducing the mechanical friction and decreasing the losses to the water-jacket, but the loss of heat to the ex'haust has had but Uttle iconsideration,. It 'is necessary to open the exhaust valve 40 to (10 degrees before the end of the working stroke, in order to get rid of the back pressure on, the piston during the exhaust stroke. The release of this exhaust, at 301b to 401b absolute pressure, with its accompanying "bark/' the S'isible flame, and redhot exhaust early, the volume of hot gas released is less than that of the cold mixture at the beginning of compression. If we carry the expansion of the turning charge 50 per cent, further, releasing the gases at a lower pressure, at a lower temperature, and at a point nearer the end of the working stroke, more heat will be turned into work, because less will be rejected in exhaust, less power will be required to open the exhaust valves, and the muffler will become extinct.