How Much More Tyre Mileage
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\AMR readers may be in danger of assuming that the regrooving of .covers will, in itself, provide an automatically increased tyre life of 331 per cent. on any cover.
That regrooving can provide extra mileage, if applied to certain kinds of cover at a suitable stage of wear, is indisputable. What must be understood, however, is that regrooving any and every kind of cover as soon as the original tread is worn is neither practical nor useful. It is not a certain economy, bearing in mind that the fabric casing is the more valuable part of a cover, and the tread the lesser.
Clearly, the tread has the simple function of providing some road adhesion and keeping the casing away from the road. The casing, however, is of necessity constructed fundamentally to possess a potential margin of life many times that of the tread. Tread life is determined by the ability to oppose abrasion. The casing has to be designed to withstand severe degrees of overand under-inflation, overloading, concussion, etc., and is considerably the more expensive part of a cover to manufacture. Steered clear Df abuse, the casing has by necessity, been designed for, and has Many times the life of, the tread. If regrooving should prolong the tread life by 331 per cent., but shorten the life of the much more valuable casing, then it should be avoided at all costs. Providing a fresh tread to a worn, sound casing is a simple matter, but providing a new casing for a tread is quite another kettle of fish!
The covers supplied under tyremileage contracts are of a special type with very heavy plain under-tread between the casing and the bottom of the tread channels. When nearly smooth at the centre line, it is an economy to deepen the tread pattern or cut a slight new one, by regrooving. The tyre manufacturer's fitter knows just how deep to go. Too deep and too near the casing, and he risks loss, soon after, of the valuable casing, from flints or other bodies penetrating into the fabric of the casing through the too-thin wall of rubber now at the bottom of the grooving he has introduced. He will therefore do nothing to prejudice the prime consideration of preserving the casing for a full new tread renewal.
Commercial covers do not possess this heavy undertread, and regrooving of such covers is a very temporary economy likely to damage or bring about damage to the valuable casing, resulting in loss of the chance of a whole tread renewal later on and the need to purchase a complete new cover. In commercial covers, the bottoms of the tread channels are so much nearer the casing as to make regrooving, without inducing damage to the casing in the process, or later on from loose road metal, a risky matter.
On the other hand, if the nearly smooth cover shows, upon careful examination, weaknesses or damage making a whole new tread renewal impossible, then certainly, with or without repair as the necessity may be, let the user boldly regroove and run the cover to death with economy.
The case is that regrooving under tyre-mileage contracts has proved worth while in the hands of the manufacturer's skilled fitter, but to the private user it is almost certainly uneconomic, being likely to reduce the chance of tread renewal afterwards and thus increase his tyre costs.
The truest tyre economy and longest tread life lie in the user doing everything he can to preserve that most costly part of his cover—the casing, and thus ensure the largest number of less costly tread renewals. If he pin his policy to that, he can find a tread-renewal system, applying no heat to the casing, which can, and consistently does, give up to six tread lives to that valuable casing, thus effecting the truest • and safest economy.
Ipswich. VICTOR B. CONNELL, Manager.
(For Bussey Bros., Ltd.) ANOTHER DRIVER ON DENATIONALIZATION THE letter from W. •F. Yorath dealing with his views
on denationalization and published in your issue dated November 30, cannot go without comment. Given a fair chance, I believe that most previous hauliers would go back into road transport, and if a driver did not like the new purchaser, he could try someone else. This would bring about a competitive labour market, and those who do. not wish to do a day's work would soon make room for others. What if one man said that there were 60,000 drivers in British Road Services and asked why they had not been consulted? Were they consulted when nationalization arrived?
Your correspondent also says " We should not monkey about with something which, I believe, may cause trouble in the ranks. . . ." I take it "we' alludes to the drivers. Welt, then, let us not monkey about, but bring competition back. This country was built up on it. At least, we .could approach the boss, which is more than we can do now, even if we know who he is, and if there were any complaints there is always the Transport and General Workers' Union, The good workers in transport need not worry. Fair play and hard work are what are required, and these
can be obtained with private enterprise. J.E.E. Manchester,
:tstpf WE ARE TOO SI M P LE
IN a paragraph under "One Hears in "The I Commercial Motor" for November 16, we are told "That aluminium is produced by dissolving the ore ' bauxite ' in molten cryolite (a mineral from Greenland) and passing an electric current through the solution."
This is a simplification of the facts, and such a simple expedient has been sought by aluminium manufacturers since the earliest days. Unlike' iron ore, bauxite cannot be smelted unless temperatures in excess of 2,000 degrees C. be used, and the ore is too impure for direct electrolysis.
There is, therefore, an intermediate stage in the pro duction of aluminium, during which the ore is refined to the white powder alumina. It is this material which is heated in a 3-5 per cent, solution with cryolite and then reduced to the metallic state by electrolysis. Greenland, incidentally, is the only known natural source of cryolite.
London, E.C.2. D. A. WILKINS.'
(For the British Aluminium Co., Ltd.)