LEAVES FROM THE INSPECTOR'S NOTEBOOK.
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The Worm Turns Again. Tyre Guarantees.,
ISUPPOSE the commercial-vehicle industry is littre if any different from other topics in that there are certain controversies inherent to it, the discussion of which appears to be of neverending interest. "Chain or Live Axle?" -",Steam or Petrol?" "Front or Rear Drive?"i "Worm or Bevel? " "Four or Six Cylinders? " "Vertical or Loco. Boiler ?" and so on—there is never any lack of subjects for those who desire to talk or write " shop." In most of these cases, voluminous discussion appears to have resulted in no conclusive decision. For instance, we are once again being confronted with the much-debated question as to the all-round superiority of the worm drive -for backaxle gearing. And the reagon for this fresh outcrop appears to be the well-founded rumour that the London General Omnibus Co., whose fleet of many thousands of motorbuses has hitherto standardized. the worm, is, in conjunction with its sister concern, the Associated Equipment Co., Ltd., seriously engaged in the search for a practicable alternative.
The L.G.O.C. was practically forced, at the time of their decision to maunfacture their own machines in an associated factory, to adopt the worm as being the only method of final drive that would .yield the requisite silent running, as stipulated by the London licensing authorities, at Scotland Yard. It was at about the same time that that clever comproncise the chain drive gearbox was evolved -with the same purpose in view. So far as the company's back axle was concerned, the worm drive also offered the lightest form of construction, and that has necessarily been a potent factor_ in London bus design throughout. It is stated, however, on what appears to be good authority, that those who are now busy perfecting the new design for the L.G.O. motorbus-in which scheme a very considerable reduction of weight has to be effected—are experimenting exhaustively with double-helical bevel and spur drives 7-and, moreover, that not only is silence already assured, but that the increase in efficiency over the worm drive is likely to be remarkable.
• Great as is the demand for the worm drive—practically all the principal makes are offered with this alternative for char-a-bancs and motorbus work particularly—in many cases it is a matter of fashion. The -worm drive is not universally satisfactory as a back-axle medium, as I imagine even its most devoted protagonists would admit. It is not the easiest thing so to design, particularly in large sizes, as to be convenient for line of drive or for clearance below. It is not a lively drive if compared with a welldesigned, double-reduction, than which, however, it is, of course, much simpler, and it should be cheaper. There are many who claim that it is sluggish when coasting, although, in my own. opinion, a well-designed worm and wheel reveals little of this characteristic.
The vogue of the worm is very largely a question of silence, with the added advantage of facility in altering the ratio of reduction without altering the housings. But on the first count, it is surely, nowa days, arguable as to whether the worm is, on the whole, quieter to any degree than, say, any of the Government-owned subsidy. type models with their original double-reduction gear drive. The adoption of the worm drive makes it easier and cheaper to attain silence, but that is subject matter for a technical article addressed to the manufacturer and assembler. The point I am considering is the retention of silence after the axle has passed the assemblers and the testers. It will be recalled that the subsidy specification did not originally permit the use of a worm in the back axle. The news of the L.G.O.C.'s casting about for a practicable alternative at any rate emphasizes the desirability of our not taking the worm too much for granted as being the last word for silent-drive back axles for commercial-passenger machinery. In fact, it is bad policy and unprogressive to take any design for granted— improvement is always possible—and in commercialvehicle design no less than in any other form of mechanical construction. The American adoption of the worm is surely dictated by question of simplicity and mass production—and the Yankee policy that it is "good enough."
The Guarantees Coming Back.
There is quite a lot of talk going on as the result of the effect of removing the solid-tyre 'guarantee. Evidence is not wanting that many users are very strongly of opinion that, a far more re-assuring policy on the part of the tyre manufacturers towards their customers wpuld have been to have increased the mileage guarantee rather than to have removed it altogether. The advantages of the cash rebate system are again being vigorously debated. The method by which users of solid tyres were tied by the impossibility of lacing a considerable loss if they wanted to" quit" was most undesirable. Generally speaking, from users' opinions in considerable numbers that I have heard expressed during the past few weeks, there appears to be a very considerable prospect of circumstances necessitating the revival of the guarantee in some new form.
The solicitude of the tyre makers for the agent's -time wasted in compiling voluminous mileage statistics is ingenuous but not impressive. There does not appear to be any real reason why a guarantee should not be given—and on a higher scale for all ordinary employment than has hitherto ruled. The firms who have retained it must be chuckling, not only for increased business but, most certainly, for the advertisement, which has been' wonderful. Their names are household words at the moment. A guarantee, with exceptions for bad service on a sliding scale, and with a much extended time limit, may yet be re-established. We shall see ! Meantime, I wish I were one of the wise men who have stuck to their original bond. It should be easy for those clever people who inspired the change to construct a thoroughly plausible reason for a further one. Perhaps the users feel the loss of their statistical duties and it would, therefore, be unkind any longer to deprive them of those duties! Anyway, as one man put it to me recently—" Better the guarantee you know, than the adjustment you don't know 1"