MOTORING.

Taranaki Daily News, 10 December 1921, Page 11

MOTORING.

NEWS AND NOTES. TYRES AND THE ROAD. The growing volume of heavy loading that is now carried on the roads makes a solution of the problem of saving our, highways more pressing. The weight of the heaviest motor wagon and the load it can carry has increased to such a degree that it is not practicable, from an economic point of view, to equip the wheels with pneumatic tyres, but a suggestion by a Correspondent in the Autocar (Eng.) bearing on this matter should receive a ,little consideration. “If,” he says, “we cannot limit the combined weight of a vehicle and loading sufficiently so that it can be carried on pneumatic tyres, an effort should be made to introduce vehicles with much larger higher rear (load-carrying) wheels. The pressure of a pneumatic tyre inflated, say, to 601 b per square inch, can never exert a force on the ground exceeding 601 b per square inch, because when the pressure tends to become greater, as when bumping on a stone, tjie tyre yields. Continuing, he points out that with a solid rubber tyre on a heavy motor coach there are, roughly, about 20 square inches of tyre touching the ground, or ’’4o square inches for the double wheel on each side. With a load of 2 tons each square inch would have a pressure on it of lewt; but as the rubber is semi-rigid, the pressure is not equally distributed. At the central point of contact it is probably nearer 2 cwt. per square inch, and where it is nearly leaving the ground only 1 cwt. or less. This heavy pressure on the ground over a small area, causes the wheel to depress the road surface ta a very appreciable extent, especially in soft places, and as it progresses, to actually push the road in a wave before it. Were, the wheel much higher the tendency would be to roll the surface. It is for the above reason that the wheels of steam rollers are built so high. Where the wheel sinks into the ground, and produces a wave, disintegration follows; a string of holes appears, and the road is ruined. It is rightly pointed out that the chief drawback to the high wheels is that they encroach upon car space. All other difficulties can easily be overcome, the height of the wheel being without influence on the engine in the case of a chain-driven car, where the chain drum can easily be increased in proportion to the wheel increase. It is argued that the problem of heavy loads can best be solved by use of wheels of a •large diameter; that is to say, wheels should press on to the ground and not into it. The advantage of pneumatic tyres is that they flatten, and so present a flat surface to the flat ground. Solid rubber tyres give but little and very inadequately. A high wheel helps, as its circumference is much larger than that of a low one, and not only presents a much flatter tread to the ground, but also a much longer one, thus distributing the weight. It is thus made very plain that on a low wheel a heavy load simply wedges the wheel into the ground until it reaches a depth which can support it. OLD BULB IS COSTLY. If the electric lamp in the head, dash, or tail light burns with reddish color instead of the pure white that it did when you first put it in, it is played out, and it is time to replace it -with a new bulb. This should be done, not only to give a better light, but to save money, as the lamp is consuming more electric current and giving less light. Unless the lamp is one of the Tungsten or Tantalum types, you must not expect more than 600 hours’ service out of it. Many people think an electric light bulb is good for a lifetime. The filaments of the electric lamp are like the wick of a kerosene lamp, they become charred and finally burn away, and must be replaced, but, of course, after a much longer use. So if you want good lights with a moderate amount of current consumed, wfttch your lamps carefully and replace when the red color appears.