Overloading, Once Persistent, but • now Habitual.
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WE were greatly impressed by an observation mad 6 to us recently by a leading haulage contractor. He bad been criticising some of our adverse comments on current rates for six-ton and seven-ton loads. He said, " There is no haulage contractor in business to-day who does not habitually put six and seven tons on chassis bought as four or five-tonners." We were impressed, not because it presented a new aspect of heavy vehicle use, but because it epitomized our own experience. By a curious coincidence, on the very same day we were In conversation with a manufacturer discussing a new model, which he preferred to call a 6-7tonner, for the reason that he thought it might be less likely to be as grossly overloaded when so named than if it were designated a seventonner—a name which more precisely indicated its real load capacity. Buyers of commercial motors to-day seem to be in general agreement in this matter. They regard the makers' rating of load capacity as nominal, as being, perhaps, on a par with the R.A.C. horse-power rating. A four-ton lorry is good for six tons, a five-tonner for seven, and so on, both up and down the scale, throughout the whole range of sizes.
Manufacturers competing with one another for custom have not merely let this practice go unchecked but tacitly encourage it by making their chassis strong enough to carry these Overloads. The -upshot is that current load designations are now only nominal, and practically every British chassis is strong enough to carry from 30 to 50 per cent, more than its rated capacity. That is all very well for those who are pre-determined to overload, but it is hard on the man who buys a vehicle as such. He Is paying for something which he does not require. The initial cost of his machine is higher than it should be and the running cost is excessive. Bluntly, his transport costs him more than it should, and the popularity of the commercial vehicle suffers accordingly.
The tyre manufacturers, too, have serious cause for complaint. The tyres fitted to these vehicles are supplied by them in good faith to carry the rated loads, and those loads are habitually exceeded. Everyone knows that overloading is a potent cause of excessive tyre wear and, although the tyres do stand up well under these unfavourable conditions, the fact remains that they do not last so long as they should, and the tyre makers have to bear the brunt of complaints when the blame should really fall on those who overload and those who encourage overloading.
It is very difficult to see how this state of affairs can be remedied. The problem seems to be one which might usefully have consideration at the hands of the Standards Committee of the Society of Motor Manufacturers and Traders, although to define frame scantlings, spring dimensions and axle sizes, in accordance with loads to be carried, is, we fully recognize, far from easy.
Air Cleaners and the Effect of Dust on Engines..
THE evil effect of dust and particles of hard grit, when they become mixed with the lubricant which separates any working surfaces, is too well known to require any description. Even when both surfaces are of hardened metal abrasion will take place, but when one surface is of soft metal, such as aluminium or Babbett metal, it is well known that any sharp particles will embed themselves in the softer metal and wear away the harder one. Aluminium and Metals similar to Babbett are used for the process known as "lapping." which is employed in cases where hard metal, and even diamonds, have to be cut or ground to certain forms ; sharp grit is impressed into a soft metal lap which will then act to grind away any hard surface brought to bear on it.
In the history of the bicycle and, still later, of the motorcar and lorry, we can trace a gradual process of guarding against the entrance of dust to all working parts. In the earlier motorcars the gears in the gearbox were exposed to dust, cylinders had open ends, bigend and main bearings, timing gears and valves were all open to the dust of the road. One by one all these parts have been covered so that no grit can enter, with, as one would naturally expect, satisfactory results. Only in one case can we remember a backward step, where for some reason the camshaft of one make was removed to the outside of the engine case. This model was, however, not retained for long.
Makers of steam lorries, who in earlier days appeared to ignore the effect of dust on exposed working parts, have been compelled to fall into line with their competitors and are gradually guarding all parts against the ingress of dust.
Everything points to the fact that dust is harmful and should be kept out, so a process of guarding against itS intrusion has gone on step by step, first the gears, then the engine bearings, then the timing gears and valves, but last of all the parts to receive attention as a matter of standard practice is the cylinder. For some curious reason the effect of wear due to no effort being made to arrest dust from entering the cylinder is not so marked as one might expect, considering that a large surface of oily metal is exposed to any dust that may be drawn In with the air, hut, although the evil may not be one that is crying loudly for a remedy, an evil is undoubtedly present, and when one considers how simple a device is needed to minimize this evil, if not to cure it entirely, it is curious that some form of air cleaner has not been fitted as a Standard on every British commercial vehicle.
In all probability the comparatively dustless state of the roads in recent years may account for this to an extent, but as a considerable saving in upkeep can he effected, especially, in commercial vehicles, it may be well to consider the merits of the various systems of air cleaners now pa the market.
Broadly, there are three systems, viz. : (1) straining of the air by drawing it through a large surface of felt, (2) drawing of the air through a mass of fine strips of metal which has been soaked in a viscous material such as oil, and (3) stripping dust from the air by the centrifugal system, a circular movement being imparted to the air before it enters the carburetter, so that all particles which are heavier than air shall be diverted into a receptacle instead of entering the cylinder. All the systems have their good points, the two first mentioned being more suitable for the removal of fine dust, whilst the last mentioned is more efficient for the arresting of heavier particles such as sand.