CONCERNING READERS' LOG SHEETS.
Page 28
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The Value of Log Sheets and the Check Which They Give on Running Costs. The Use of Trailers.
HAVING prepared log sheets, most readers willlike to have a little information as to what use they are going to make of them, and, asa, prelude to the affording of this information, I will commence this week by discussing briefly the figures which were given in the sample log sheet which I published in the last of this series of articles. Obviously, these log sheets are going to be most useful as a check upon the running costs of vehicles, while they will be almost equally valuable as an aid to estimating the prices which the haulier must charge for his services if he is going to make a reasonable profit out of his business.
We will, first of all, examine the sample log sheet in the light of the first of these requirements; that is to say, we will see what sort of figures we can obtain from it for the running costa of the two lorries with which these particulars are concerned.
As regards wagon No. 1, its total mileage during the week was 245, the petrol booked against for the , same period being 63 gallons. Of this amount, hoesever, there is still some remaining in the tank, and on examination we discover this to be 4 gallons ; 59 gallons of petrol, therefore, having been consumed in running 245 miles. The consumption is 4.15 miles per gallon, and, with petrol at 2s. per gallon, the cost is approximately 5.8d. per mile. A pint of oil has been used, costing Is. 3d. and 1 lb. of grease costing Is. 2d. ; total, 2s. 5d., which works out approximately at .11d. per mile for lubricants. The amount for maintenance for this particular lorry is rather heavy—,E4 us. 3ich, spread over 245 miles, amounts to nearly 4-ici. per mile.
As regards wagon No. 2, this presents quite a different result. 87 gallons of petrol are booked against this vehicle, and on the assumption thatthere are still seven gallons in the tank, this means to say that 80 gallons only have been consumed for 630 miles, the total distance run during the week. The mileage per gallon, therefore, amounts to 7.89, which is remarkably good for a four-tonner, the cost being 3.05d. per mile. The oil and grease, calculated in the same way as 'wagon ,No. 1, amounts to 0.19d. per mile and maintenance .to only 0.34d.
These results, as obtained from one log sheet, are not conclusive, principally because they only cover such a short period of running. Not only do the various items as obtained for the two machines differ one from another, but it will be observed, on reference to our previous figures of running costs, that they differ considerably from what we know to be c32 fair averages. Results of any value could only be obtained from records covering a fairly long period. ,
Some of these I will discuss in a subsequent article, when I will also indicate more.fully uses to which these log sheets may be put.
The Use of Trailers.
I have a letter from a well-known maker of trailers referring to my notes on the use of this class of vehicle in an article which appeared in the issue of November 1st. The writer of the letter refers to what he is pleased to call an "obvious error." I am afraid •that, if it is olsvious, it is so obvious that I cannot see it. There is no error whatever in the statement to which he refers, which was that "every ounce of the trailer counts to the full as load on the van." That statement is perfectly true.
The writer of the letter begs me to consider the horse, and states that the horse that pulls five tons, in some cases with ease, would be far from equal to carrying ote-eighth of that amount on its back. The comparison is, of course, ridiculous ; the horse is perfectly incapable of sustaining on its back a load of five tons ; equally so, however, would be a lorry of the same weight as a horse, but a lorry of the same weight as a horse would never pull five
• tons except in the most favourable possible conditions. It would not have sufficient adhesion for the purpose. Incidentally, there is no horse that could pull five tons for any reaionable distance unless the road on which it was operating was perfectly flat and presented a good surface.
My correspondent then goes on to state: "It has been established in very careful tests recently made that the amount of draw-bar pull nece'ssary for a trailer behind a lorry is only 40 lb. per ton. This is most certainly, likely to be correct, but it is equally certainthat the resistance to motion of the lorry which pulled it was not more than 40 lb. per ton, so that if the lorry with load weighed eight tons, and if the trailer with load weighed six tons, the total resistance would be 40 times 14, or 560 lb., and it 'would be the same whether the trailer was at the back of the lorry or stuck on top of it. That is what I mein when I say that "every ounce of the trailer counts to the full as load on the van."
• The writer of the letter goes on to say that, according to the deductions set forth by me, a lorry can only pull an a level road the same amount as he can lift. I do not understand what he means, by this, and how, by any possibility, he could imagine I
meant it by anyshing I said. TEE SKOTC11.