MOTORING NOTES

Waipa Post, Volume 43, Issue 3392, 24 December 1931, Page 6

MOTORING NOTES

TYRES FOR VEHICLES CARRYING HEAVY LOADS.

Automobile tyres are slowly taking the burden of passenger and freight loads away from waggons and carts throughout the world, but just what goes into a tyre to give it strength and durability to carry such loads swiftly and safely is not commonly known. The belief that a tyre is made entirely of rubber may be held by a few. In fact, there was a time when it was believed that tyres were cut out of rubber.

It was the discovery of the vulcanising process that made it possible to manufacture a rubber tyre with resilient strength and paved the way for the commercial era of the rubber industry. Charles Goodyear, after whom the Goodyear Tyre and Rubber Company of Akron, Ohio, U.S.A., was named, was the discoverer of the vulcanising process.

Cotton constitutes a vital part in the building of tyres. At the cotton mill the cotton is woven into cord. The Goodyear Company maintains its own mills in various parts of the United States so as to be able to manufacture the best grade of cord possible, which is known as Supertwist and is used exclusively in Goodyear Tyres. Each bale of cotton entering the Goodyear mills is sampled and every roll of Supertwist is tested before utee to see if it has the high tensile strength demanded and the degree of elasticity rquired. Crude rubber in different lots, are received from the plantations, varies greatly in the manner in which it will cure after compounding. A bale of crude rubber is taken from each of four or five different lots, and mixed together for blending. Chemicals used in compounding are tested for their degree of purity and strength. From every batch of compounded rubber a sample is taken for curing in a small mold and tested for toughness and wearing ability. The load carrying ability of any pneumatic tyre depends entirely on the capacity of the tyre to hold the air within it. Therefore, it is the tyre's primary function to hold the pressure of the inflated tube on the inside. It must also resist the pressure on the outside from road contact.