Opinions and Queries
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Reducing Fuel Consumption
VOUR readers should be indebted to C. D. H. Stead I for his data on fuel consumption, published in your issue dated March 14, and will, one hopes, accept his invitation to exchange information. Perhaps even the manufacturers of the vehicles and carburetters will show a little imagination and lend a hand.
I do not run a fleet of Morris .1 and P.V. vans, but believe that the major enemy is cold cylinder bores, and the remedy (short of modifying the water flow) is the use of an all-metal (preferably aluminium) cylinder-head gasket. Plexeal gaskets are now well known and pay for careful fitting. The driver can get ." off the choke" much sooner with Plexeal.
An air-correction jet of 170 enables a smaller main jet to be tised and, should the .main jet disclose a "flat spot " at small throttle openings, a much larger air-bleed plug to the pilot jet will cure this. I use a 71-6--in. drill for opening the hole in the plug. With an all-metal gasket, the ignition may be advanced.
In another make of carburetter, which may be the one used by Mr. Stead on his 2-tonner, opening-up the lower drilling of the capacity well to Tle in. worked wonders and gave a 50 per cent. increase of mileage on a 5-tonner without altering the jets. I do not recommend wide plug gaps.
There is a tendency to use too-small choke tubes, and the " blow-back " trouble worsened by these can be eliminated by the insertion of a central baffle or choke in the induction pipe. One can afford to lose half the effective area of the cross-section of the induction pipe. With an all-metal gasket, and the consequent better heat distribution, it might be reasonable to take the belt off the water-pump pulley. It is imagination and care that obtain the best results.
Gravesend. H. C. BARTY.
EXPERIENCE WITH RETREADS SEVER AL correspondents whose letters have appeared in "The Commercial Motor" have been anxious to learn of the results obtained from retreaded tyres. My experience in that direction may prove of interest to
them.
The vehicle concerned, is a 1937 Dodge 25-seat coach on the R.B.F. chassis.. The tyres fitted are 700 by 20 low-pressure. All have been remoulded by U.T.S. and two sets have been used during the past three years. The first completed 11,000 miles and, apart from a puncture in a rear tyre, no trouble of any description occurred. The second set has completed 12,000 miles, and the rear twins are still on the vehicle. They appear to be good for a further 3,000-4,000 miles' Again no trouble of any description has been experienced.
Tyre pressures have been meticulously maintained and the cost of retreading, which was £7 10s. per tyre, works out at less than id. per mile.
I would be pleased to learn how these figures compare with new tyres, as regards both mileage and cost.
Rochdale. J. MATTHEWS.
I WAS interested in the query raised by F. R. Cope, in I your issue for March 14, concerning the economy of• retreaded tyres. My company keeps a strict record of all tyres used on the fleet, and the following facts in
respect of retreads (not remoulds) may be of interest. During a period of three years, 45 retreads have given an average mileage of 16,189; their size, incidentally, is 34 by 7.
As regards the 36 by 8 size, 29 covers have been treated in this way over the same period and the average mileage has proved to be 18,422, whilst the 40 by 8, of which 16 have been retreaded, show an average of 20,672 miles. It will be appreciated that the cost of the treatment is slightly less than half that of a new cover.
I would point out that the loads which we carry are varied and consist mainly of sand and gravel, whilst most of the journeys are in the Metropolitan area.
Bexteyheath. C. D. COPPOCK, A.I.R.T.E.
REAR LIGHTING CAN BE OVERDONE ARE we now to have a " fairyland " of rear lighting? One can see on the roads to-day how hauliers have improved their vehicles for safety reasons, but the matter can be overdone
Compulsory stop lights are to be recommended, but instead of having two rear lights indicating the width of the vehicle, let theie be a single rear light of reasonable power, wired for two bulbs plus a stop lamp There could be white markings to show the height and width of the vehicle, augmented by reflectors. In addition, of course, the rear number plate should be lit. I do advocate that all trailers should carry side Among other safety measures drivers can adopt is not to park on the off side of the road After dark. Special care should be taken in the twilight to watch out for cyclists and pedestrians Great Yarmouth. ROBERT NORMAN.
THE national safety campaign for improved rear lighting on commercial vehicles would achieve far greater success if fleet operators were given some official guidance on the probable requirements of any new lighting regulations which will, undoubtedly, be introduced at some later date.
Whereas many operators would be willing to make reasonable improvements immediately in order to earn the goodwill of the public, they are not prepared to incur the double expense of modifying their vehicles now, and then again, say, in nine months' time, to satisfy new regulations, nor may they be prepared to carry out expensive alterations to cover every possible demand that future regulations might Make.
In the hope that this letter may provoke some discussion on this subject and thereby bring to light some authoritative views, the following opinions are 'given, also the action that is being taken in connection with a fleet of vehicles—
It is suggested that the main dissatisfaction with the existing single-bulb rear' lighting is that danger may be caused through failure of the bulb, or that the light emitted by one bulb may not in itself be sufficient warning to other drivers. It would seem that such points as the indication of the width and size of the vehicle by lights are unimportant, as no driver would overtale on the near side of any rear light. The action being taken: by the writer to improve the lighting Of vehicles under his charge is to wire in parallel both bulbs in a standard stop and tail lamp, and then fit an additional small single-bulb stop lamp. Thus, double safety is ensured by the continuous burning of two bulbs and the area of illuminated red glass is doubled, in this case to 31 ins. diameter. C.A.V. has just introduced a rear lamp with two bulbs wired in parallel.
A commercial-type Radyot reflector is fitted to each extremity of the rear width of the vehicle.
Such schemes as fitting a single-bulb rear lamp at each extremity of the vehicle width would seem to increase the danger should the usual off-side lamp fail.
London, E.3. W. A. BRAY, A.I.R.T.E.
(For Perinanite, Ltd.) A MATTER OF ARITHMETIC yOUR issue of March 14 contains a heading which reads "R.H.E. Efficiency 9 Per Cent. Down," and you proceed to justify this by stating that there was a 9 per cent. drop in payload per mile in 1951 as compared with 1950.
This conclusion is reached only by way of an elemen
tary statistical fallacy. To take a simple example, compare two vehicles. The first makes 250 loaded journeys of 5 tons each over a distance of 20,000 miles, with an additional 4,000 empty miles, whilst the second vehiclein the same period performs 225 loaded journeys with an average load of 5.33 tons over a distance of 20,250 miles, with 4,250 empty miles. In the first easel the ton-mileage-in the period is 100,000 and .in the . second Case it is -108,060—an improvement of 8 per cent.
By your arithmetic, on the other hand, you would say that the first vehicle carried 1,250 tons in all and travelled 24,000 miles, giving a co-efficient of 0.5208 "tons per vehicle mile ". (whatever that may mean),
whereas the second vehicle carried only 1,200 tons and travelled 24,500 miles, your co-efficient being then 0.4898. From this you would then deduce a "drop in payload" Of 6 per cent. in place of tie actual improvement. Vehicle miles must be related to ton-miles.
A second statistical error made in your paragraph is to divide the total tons and miles run during the year by the fleet strength as it happened to be at the end of the year. Where fleets are changing in size and composition at an uneven pace, this can obviously give absurd results.
A third fallacy is your assumption that an increasein the dead-mileage ratio is automatically a sign of decreased efficiency. In the example the empty miles in one case are 16.67 per cent. of the total, and 17.35 per cent. in the other. Yet the ton-miles per total vehicle mile—which is the better test—are 4.41 in the second case and only 4.17 in the first.
Perhaps 1 should point out also that your summation of the miles run by the fleet of the Road Haulage Executive during the year 1951 is wrong by 10,000,000 miles. J. H. BRENNER,
Chief Public Relations and Publicity Officer (For British Transport Commission). London, S.W.I.
KEEPING HAULAGE RECORDS I HAVE a friend who is running a small haulage 'business, 4-6.-ton lorries; unfortunately his records andbobltkeeping are fairly hopeless. He is a fine engineer but no clerical man.
To run the business on sound lines; what are the essential books to keep, and what items are applicable?
Birmingham. "INTERESTED." [All that "Interested" requires for his friend is a copy of "Cost Recording Made Easy," published from the office of this journal, price 2s. 2d. including postage.—En.]