Solving the
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PROBLEMS OF THE CARRIER
IHAD thought that, in the course of time, the problem of the man who habitually overloads his vehicle would, if it did not vanish altogether, so diminish as to make it unnecessary for me to deal with it. Generally, I have, so far as possible, evaded direct answers to questions dealing with the cost of vehicles which were admitted to be subjected to heavy overloads, especially if the inquirer proposed to make that overloading a means for cutting rates.
I have usually replied, as is still the truth, that it is practically impossible to give accurate figures regarding the cost of operating a vehicle under the conditions named. I really hoped that an outcome of the 1933 Act would be so to discourage overloading as to make it obviously unprofitable. When I learned that manufacturers were revising their schedules of models and loading in an upward direction, labelling as 4-tonners chassis that previously had been held to carry 3 tons, and so on throughout the range, I felt that the days of the overloader were numbered. .
It seemed that the manufacturers themselves were taking the step which I have for so long suggested, that B40 is to say, building their vehicles for stated loads, and refusing to guarantee their products if used to carry weights in excess of the rated capacity. That has always seemed to me to be a better policy than that which has been pursued for some time, of building vehicles capable of carrying excess loads of 50-100 per cent.
Now I have had rather a bad blow. A new method of teasing the man Who buys a 3-tonner for 3-ton load6 is being adopted. It is that of rating a vehicle, but guaranteeing it for upwards of 25-per-cent. Overloads: Why not add the 25 per cent, and make that the rated capacity, and discourage overloading in any shape or form? •
I find myself faced with the necessity of meeting these new conditions, under which overloading, is now" definitely encouraged by manufacturers. I have, at this moment, a query before me as to the probable operating costs of a machine so worked. mother words, the problem I have for so long evaded has now to be
faced and solved. .
In stating that actual costs were practically impossible to.obtain, I have done no more than set out the facts. Users who overload consistently will not admit the high cost of such procedure. To a certain extent I am, therefore, compelled to fall back upon conjecture.
It will be useful if, before dealing with the specific inquiry which has brought me to the point of writing this article, I deal with the subject in a general way, pointing out the effects that overloading within the limits of a manufacturer's guarantee are likely to have on operating costs. I will take the items in the order in which they appear in l'Ite Commercial Motor Tables of Operating Costs.
The first of these items is fuel, on which some increase in expenditure is surely inevitable. It may be assumed that the rise in cost will be approximately in proportion to the total increase in gross laden weight of the vehicle. If the gross weight, rated to capacity. be 5 tons, and a ton overload be carried, the increase in fuel cost will be approximately 20 per cent,, but the degree of accuracy of this assumption depends, to a large extent, upon the class of country in which the vehicle is used.
One difficulty about overloading, which every experienced user will confirm, is that in a hilly district or in difficUlt, country it may increase considerably the percentage of low-gear running. In that case, the fuel consumption may rise more •rapidly than the increase in total load.
This increase in the use of low gear and the corresponding proportion of inflation of petrol. consumption will be the more noticeable, of course, if the engine be comparatively small. On the other hand, a large engine generally .consumes more petrol all round, so that, in the long run, there is not much to choose • between one make of chassis and another in-this respect.
The, oil consumption will not be affected unless the country it hilly and more resort has to be made to.
low gears. It will be noted, as I proceed, that the nature of the country in which the vehicle is used has a big effect in determining the cost of overloading.
So far as the expenditure on tyres is concerned, a good deal turns on the size of tyres fitted in the first place. If these be fairly accurately proportioned to the rated load of the chassis, overloading will probaoly increase the tyre cost considerably. Indeed, the first point I would make in discussing the wisdom of overloading would be in respect of tyres. I should recommend the owner to communicate with the tyre manufacturers, stating his intentions.
If the conditions be as above stated, the tyre maker would probably •recommend the use of larger equipment. Ii the tyres be of ample dimensions in the first
case, all that would be necessary would be an adjustment of the pressure, so as to enable the extra load to be carried. Do not on any account, however, make the mistake of imagining that increasing the preskire in tyres which are under size will enable them to carry exoessive loads. It will not.
Roughly, it would be reasonable to expect the tyre cost to be greater, but not, perhaps, quite in proportion to the increased loading. The item of cost about which most discussion can develop is, as usual, maintenance.
Some of the expenses involved in maintenance will, quite naturally, not be affected at all, but these comprise in sum only about 30 per cent, of the cost of maintenance per mile. Indeed,. in a good many cases, where the driver carries out washing, polishing, greasing and routine operation in his own time and at no extra charge, the proportion of these unaffected items is practically negligible.
The remainder of the items are definitely increased as regards their effective cost per mile. These items are the refacing of the clutch and .brake shoes, and the overhaul of the engine, chassis and body. ObvionSly, other things being equal, an overloaded vehicle will consume its brake-shoe facings more rapidly than will one that is not. An engine that is driven " all out" for a much greater proportion of its time, as is inevitable with an overloaded vehicle, will need overhauling and reboring sooner than will one which is not called upon to work so hard.
The same argument applies in the case of chassis and body overhauls. The springs, and the connections between springs and chassis and springs and axles, will deteriorate more rapidly. The gears, and especially the clutch, will, require repairing earlier.
It is certain that overloaded bodywork will need attention sooner. I should be inclined to add 20 per cent. to the maintenance costs enumerated above, and that will mean from 12 per cent. to 15 per cent: increase on the total maintenance cost. If, however, the owner who is considering this matter has the minor and routine maintenance operations carried out by, the driver, he may expect his total maintenance cost to be increased by about 20 per cent. Depreciation can, 'I think, be left alone.
Clearly therefore, taking only the running costs, a definite increase is to be anticipated in respect of four of the five items. Standing charges will remain un
affected. S.T.R.