Does Overloading Pay?
Page 48
Page 51
If you've noticed an error in this article please click here to report it so we can fix it.
An Examination of the Question Whether Increased Revenue Gained by Exceeding the Rated Capacity of a Lorry is Offset by Higher Running and Maintenance Costs IDISLIKE overloading. It may be that I have an orderly mind and do not like a vehicle to be overloaded because it upsets all my calculations. Most pieces of machinery, and I include commercial vehicles in that category, are sold on the understanding that they will do a certain amount of work in a specified time. In many cases the load is specified with the concession that overloading is permissible if it is occasional only.
Overloading a vehicle, if it is proved, may involve loss of any rights the owner may have under the manufacturer's guarantee. As, however, the guarantee is for six months only—guarantees are worded to protect the manufacturer not the buyer—there is little substance in the threat of its forfeiture.
I have always thought that the tendency to overload a vehicle would, in the course of time, die out, and for that reason I have for a long time refrained from discussing it in these articles. I have been chary of giving advice when it has seemed to me that the inquirer is deliberately going to overload his vehicle. My principal reason for that avoidance has always been that I cannot deal with the cost of overloaded vehicles in a rational way: I feel that I have nothing to protect me if my calculations go astray. I. am treading on shifting sands.
Got to the Top
It does not make it any easier for me that, to my certain knowledge, many of my successful haulier friends have made their way to the top layer of successful operators ,simply and solely by overloading and rate-cutting.
Generally, I have evaded direct answers to questions dealing with the operating costs of vehicles which were admitted to be subject to heavy overloads, especially if the inquirer proposed to make that overloading a means for cutting rates.
I have usually replied that it is practically impossible to give accurate figures regarding the cost of operating the vehicle under these conditions. In making that statement 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 compelled, therefore, when I have a problem of this kind to solve, 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 B22 deal with the subject in.a general way. I shall point out the effects that overloading are likely to have on operating costs. I will take the items in the order in which they appear in The Commercial Motor Tables of Operating Costs.
The first is fuel. On this some increase in expenditure is surely inevitable. It may be assumed that the risc in costs will be approximately in proportion to the total increase in the gross laden weight of the vehicle. If the gross weight, rated to capacity, is 8 tons, And a ton overload is carried, the increase in fuel cost will be approximately 121 per cent., but the degree of accuracy of this assumption depends, to a large extent, upon the kind of country in which the vehicle is used.
More Low-gear Work
One difficulty about overloading, which every experienced user will confirm, is that in a hilly district or over difficult country it may greatly increase the percentage of low-gear running. In such cases the fuel consumption may increase more rapidly in proportion to the degtee of overloading.
This increase in the use of the lower gears and the corresponding proportion of inflation of petrol consumption will be the more noticeable, of course, if the engine is comparatively small. On the other hand, a large engine generally consumes more petrol all the time so that, in the long run, there is not much to choose between one make of chassis and another in this respect.
I am aware that, given careful driving, a larger engine may be found to be no more expensive in its consumption of fuel than is to be expected in the case of the smaller engine. In my view the advantage of having a larger engine is lost if the driver does not at all time endeavour to get the most out of his vehicle regardless of the effect on petrol consumption. • The oil consumption will not be affected unless the country is hilly and more resort has to be made to the gearbox. It will be noted, as I proceed, that the nature of the country in which the vehicle is being used has a big effect in determining the cost of overloading.
In this connection I should like to refer to the experience of one engine manufacturer whose product was normally used, in this country, as a power unit of articulated vehicles carrying payloads of 8-10 tons. On the Continent, in the Low Countries, articulated vehicles powered by the same engine were normally used to carry loads of 16 tons. Being
somewhat concerned at the potential long-term results of such use, the engine maker produced a larger unit and offered it to this Continental user as being preferable to the smaller power unit and better able to carry that load. The overseas buyer welcomed the new engine with open arms and promptly put it to work as the power unit of an articulated vehicle of 18 tons capacity.
So far as the expenditure on tyres is concerned, a good deal turns on the size of the tyres fitted to the vehicle. If they are fairly accurately proportioned to the rated load of the chassis, overloading will probably greatly increase the tyre cost. It is not exaggerating to state that the expenditure on tyres will be doubled. Indeed, the first point I would make in discussing the wisdom of overloading would be in respect of tyres.
The tyre maker would probably recommend the use of larger equipment. If, however, the tyres happen to be of ample dimensions in the first case, all that would be
necessary would be an adjustment of the pressure to enable the extra load to be carried.
It is important that I should give a warning here. The owner should not, on any account, make the mistake of increasing the inflation pressure in tyres which are undersized to begin with. Here again I should recommend the inquirer to get in touch with the tyre maker or his agent.
The item of cost about which most discussion is likely to develop is, as usual, maintenance, Some of the expenses involved in maintenance will, quite naturally, not be affected at all. These, however, 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 operations in his own time and at no extra charge, the proportion of increase resulting from overloading will be practically negligible.
Brake-facing Wear
The other items are definitely increased as regards their effective cost per mile. These items include refacing of clutch and brake shoes and the overhaul of the engine chassis and bodywork. Obviously, other things being equal, an overloaded vehicle will consume its brake-shoe facings much more rapidly than will one which is not. An engine that is driven all out for a much greater proportipn 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, shackles and U-bolts will depreciate 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 would mean from 12-15 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—and by that I mean certain maintenance operations of a minor character, additional to washing and greasing already mentioned—he may expect his total maintenance cost to be increased by 20 per cent.
I assume that the item depreciation is unaffected: the thoroughness of the maintenance operations will be offset by the savings on depreciation.
Costs Will Increase
Clearly, therefore, taking only the running costs; a definite increase in expenditure is to be anticipated in respect of four of the five items of the running costs. The standing charges will remain unaffected. '
I recall a conversation I once had touching this very subject. It was some while back, as may be judged by,the fact that the limiting unladen weight for a 30 m.p.h. vehicle was 2i tons and not three, as it is today.
On the occasion of our meeting, my friend was just about to buy a new vehicle and had decided on a 5-tonner:chiefly because that was the largest vehicle that could be had in those days weighing less than 2 tons unladen. Actually he wanted a 6-tonner and he proposed to get over the difficulty of insufficient capacity to meet his requirements by loading his 5-tonner with 6 tons.
After the usual preliminaries, he told me of his intentions as regards the new vehicle. "What I should like to know from you," he said, "is how far can I apply the figures for a 5-tonner in "The Commercial Motor Tables of Operating Costs" to this 5-tonner if I use it to carry 6-ton loads? Will the 5-ton costs still apply? "
" No," was my reply. "If the figures are right for a 5-tonner operating in this district and on the class of work you are doing. then most certainly they will have to be increased to allow for the difference in loading if you persist in carrying 6 tons. "1 don't suppose they will be the same as those for a 6-tonner—the tax, for one thing, will be less—but, as you know, the unknown factor is maintenance."
"As to that," he replied, "I shall have the guarantee to fall back upon."
"The guarantee is valid for only six months, but maintenance goes on for ever," I replied. "Moreover, the cost of maintenance grows with the years and, in my opinion, rises more rapidly in the case of a vehicle that is overloaded than when it carries only its rated load."
"I appreciate that," he said, "but will you give me an idea as to what allowance I should make, mile by mile, for these increases in cost on the understanding that I am going to use this 5-tonner in the same way as I am operating my present vehicles, but that I am going to carry 6-ton loads for a proportion of the time." It is now necessary to explain that I had gathered, in the course of our conversation, that my friend himself drives one of his two vehicles, employing a man for the other, and that one half-day per week at least was set aside for maintenance. Each man looked after his own vehicle, lubricating and adjusting it; the machines were washed and polished on the premises, and only major operations of repair were entrusted to the local agent. In other words, he was maintaining his vehicles on what I would call the minimum reasonable scale. If readers will refer to the earlier part of this article, it is stated that in those circumstances the percentage increase in maintenance costs is at a maximum. The actual increase in maintenance cost is, nevertheless, less than when the whole of the maintenance is carried out independently and charged as a separate item. S.T.R.