OPINIONS FROM OTHERS.
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The Editor incites correspondence on all subjects conneeed with the use of commercial motors. Letters should be on one side of the paper only and, preferabty, typewritten. The right of ebbrevietiOn is reSer Pad, and no responsibility for views expressed is accepted.
Diesel-engined Lorries in Actual Service.
The Editor, THE COMMERCIAL MOTOR.
[2737] Sir,—In reply to elle letter from the Saurer Commercial Vehicle Co., Ltd., published in your issue of February 12th last I would ask you kindly to publish the following :—When I advised you of Messrs. Majors's lorry being put into regular commission I intended to convey that this lorry was one of the regular products of the Daimler-Benz Co., and not an experimental machine being tried out.'
As a matter of actual fact, the Merc6des-Benz Diesel lorry has been running regularly on demonstrations since early in May last, ancl.was undoubtedly the first ever to be ran in this country; that is, in the case of a machine taken from regular production.
I may add that the Saurer-Co. has stated in a letter that the machine it had running was a special vehicle and was not being offered on the market, so that it is evident that, although it has one running in the service of a customer since October last, this is evidently an experimental machine on test. The Daimler-Benz Co. has had these machines in regular production for some time, and has sent many to different parts a the world, and there is no doubt that this company was the first in the field. I feel sure that it is even now the only concern in the world which can, and does, produce regularly standard-type
Diesel-engined chassis. .
Credit must be given where credit is clue. For some eight or nine years the .Daimler-Benz Co. has been working hard and steadily on 'this proposition, an extremely difficult one, and has expended a great deal of money on it, thus fully deserving the success Which it has achieved. It is undoubtedly, the, most reliable and economical transport maehine ever produced, and deserves more recognition than it. has hadefrom the engineering world in general.--Yours faithfully. W. H. GODDARD, A.M.I.Mech.E. Beeston, Leeds.
Technical Aspects of Multi-cylindered Engines.
The Editor, THE COMMERCIAL MOTOR.
[2738] Sir,—I would like to call attention to a slight technical inaccuracy which occurred in your issue dated January 22nd in an article entitled, "The Technical Aspects of the Multi-cylindered Engine."
I think I am right in saying that the remarks. tinder the drawing of a connecting rod in the position of maximum velocity seem hardly in accordance with modern ideas. True, as you have drawn it, it is the position of maximum velocity of the piston, and therefore the point of minimum acceleration. Surely, it Is the extreme change of velocity, and, consequently, the changes of force that take place approximately at the bottom and top dead centres, which are important.
The acceleration or deceleration is very small within 30 per cent. of the position A which you indicate, and would have very little effect on the vibration of an engine suitably designed—i.e., with a reasonably long connecting rod and square dimensions, as regards bore
and stroke.—Yours faithfully, E. V. TRYE. London, W.
[We believe that the writer of the letter is suffering from the old delusion that the forces required to stop and start the pistons when they are moving rapidly—i.e., at the top of the stroke—are very considerable, forgetting that these forces are exactly balanced, and whatever is given in energy to a flywheel in stopping is received back again when the pistons are started on their return stroke. The point he raises is incorrect. He is perfectly true in saying that the point of maximum Velocity is also that of minimum acceleration, but it also marks the change-over of force direction; in other words, the stress on the connecting rods becomes compressive instead of tensional, with the consequence that the resultant force of the whole moving unit upon the crankpin (and, in consequence, upon the crankshaft and the engine body) is downward, and, as explained in the text, the upward moving piston also produces a downward-acting load upon the crankshaft at about the mid-position for the crankcase.—En.]
Pits versus Ramps.
The Editor, THE COMMERCIAL MOTOR.
[2739] Sir,—It would be interesting, to hear the views of your readers on the relative, merits of pits and ramps for carrying out repairs to low-loading motorbuses.
My own experience leads me to think that pits are better for running depots where inspection and small repairs have to be done quickly, but for a general overhaul in the works I think a ramp or some other method of raising the car about a foot from the floor is preferable to-a pit. Ramps admitmore light and leave a level
floor for handling the units.—YOurs faithfully, , .W.S.
Maidstone.
Running Costs for Large Buses.
The Editor, THE COMMERCIAL MOTOR.
[2740] Sir,—I am rather interested in the costs of operating double-deck buses in city service on a large scale, and thought that the following comments on your Tables of Operating 'Costs might be of interest. I have gone to some tronble to obtain data from operators on costs of running covered-top city buses Cu pneumatic tyres and seating 52 and 72 persons. These vehiclee run about 9.5 m.p.h. for 10 hrs. per day =665 miles per week, or 34,675 per annum, which I think you will agree is typical. •
Petrol and Oil.—Your Table IX gives 1.95d. and 2.1d. per mile for 48 and 56-seaters respectively. Figures from an important corporation and the London General Omnibus Co., Ltd., give 2.1d. to p.2d. —nothing to argue about here. Now for the 72-seaters. Table XI gives 2.34d. I was given 2.5d. by u corporation running 60-seaters. Little to dispute here, but your figure seems a bit low.
Tyree.—Your figures are high. Table IX gives 1.35d. to 1.45d. for 48 and 56-seaters and Table XI 1.8d. for 72-seaters. The costs of a large municipality are .85d. for four-wheelers and those of another .975d. for six-wheelers—mutually agreeable figures, which think are typical, Maintenance.—Table IX gives 1.89d. to 1.08d. and Table XI 2.5d. I think these figures are low, especially for the six-wheeler if for town service. The L.G.O.C. report 2.6d. as their maintenance cost for four-wheeled buses, and, whilst these are on solids and have a long life, 1 think their exceptionally favourable conditions do not allow us to put the maintenance of a four-wheeled city bus at less than 2id. per mile and a six-wheeler, in proportion, at 31d. to 3id. per mile. This is confirmed by Birmingham and other municipal figures as regards four-wheelers. Country work may be much easier, but I am assuming city operation. No actual figures can be obtained yet for six-wheeler costs.
Depreciation.—Table IX gives 1.93d. to 2.13d.—say, 2d. per mile. If the capital cost is about £1,500 this is a life of 180,000 miles, or five years. Do you not think that the life of a bus may be put at a little higher than this nowadays—say, seven years?
interest—Table IX says 370d. to 400d. per week, B43 which gives, say, 3A5c1., or about £1,530, as the cost of the bus (using 5i per cent.) which I have used above. I agree this cost as reasonable.
Now I cannot understand your figures for sixwheelers in Table XI-1.e., 4.8d. per mile for depreciation and 800d. per week for interest. These are terribly high to point to a figure of £3,100 as the cost of the bus, which is, of course, in the neighbourhood of £2,000. There must be something wrong here.
Waves.—You make wages a fixed weekly charge. This, whilst O.K. for a man with a few lorries, seems quite wrong for a bus operator who can keep his men fully employed. Looking at the figures for 700 miles per week they are given as 11.13d. to 11.78d. per mile (Table IX), but wages in these figures are only 1,680 -i700 = 2.4d., which assumes men working 70 hrs. per week. Actually, another half-shift would be reqpired and wages would approach 31d. per mile at least. The " one-man-one-lorry " principle cannot apply to buses.
Summarizing :—Petrol and oil: Rather low for sixwheelers. Tyres: High (by 60 per cent. to 70 per cent.). Depreciation: High (five-year life only and very high cost for six-wheeler). Interest: High for six-wheeler. Wages: Too low—on unsuitable basis.
I do not quite appreciate what type of service Tables XIII and XII refer to, unless it is country service.
I offer these remarks purely in a constructive spirit. I am well aware of the thanklessness of preparing estimates of operating costs, but think you might be interested in my comments.—Yours faithfully, HENRY WATSON". Ilford, Essex.
[We welcome Mr. Watson's letter as giving us an opportunity to demonstrate, in reply to a practical criticism, the utility of our tables, and wee-will take the points raised in the order in which they appear.
The figures for petrol anti oil are close enough for practical purposes in all eases. The figures which are quoted in the letter all relate to buses in city use and subject therefore to frequent stops and restarts. They, naturally, give figures above our averages, which include many from concerns which are doing a fairly high proportion of long runs, with stops not so many or so frequent.
On tyres, the same conditions produce contrary results. Costs for tyres on city work are less than those experienced when country runs are included. Moreover, the cities to which this correspondent refers are situated where the roads in the surrounding districts, just outside the city, are also good. Different results are experienced in the majority of towns in industrial areas, where the surfaces of the streets, even in the town itself, are not conducive to leng life of tyres. Our tyre figures are increased by the presence of many such cases as these.
The widest variation in running-cost figures occurs in connection with the item thaintenance. We met with a case the other day where the figures for mechanical maintenance worked out at no more than 0.066d. per mile' a phenomenally low figure and one which we should not be prepared to inelude in any schedule compiled as a basis for the averages which are presented in our tables. The figure is, however, worth quoting as demonstrating how wide the divergence may be.
The direct relation between maintenance and depreciation is exemplified in Mr. Watson's reference to the latter. Increasing the life of the vehicle is only done at the expense of maintenance. Old machines cost more to maintain, and put up the average figures for maintenance. We are aware that many bus companies write off their vehicles in five years, and usually dispose of them at the end of that period, because they find it more economical to do so.
As regards interest on first cost. A well-found 72-seater six-wheeled bus with a six-cylindered engine, fitted with upto-date bodywork and embodying the latest improvements and fittings for passenger comfort, will cost nearer £3,000 than £2,000 retail. It may be that our figures for this item on a 72-seater are slightly on the high side, but not so much so as seriously to affect the accuracy of the figures as a whole.
In raising the point he does in connection with wages, Mr. Watson touches on a difficulty which has all along confronted us in connection with these tables, and one to B44
which we have referred from time to time editorially. It is practically impossible, in tabular matter of this kind, to take account of all the possible variations in usage in respect of time of employment of drivers, conductors, and so on. We have therefore from time to time, in referring to this matter, counselled our readers to modify these figures for standing charges in accordance with their own personal experience. We reiterate that advice now.
Tables XII and XIII refer to motor coaches, as distinct from motorbuses, that distinction, for this purpose, turning on the fact that whereas conductors are generally regarded as essential on motorbuses, they are not so regarded on coaches. These two tables refer to machines which are chiefly employed in more or less long-distance pleasure
Someone Ought to Tell Them Of It.
The Editor, THE COMMERCIAL MOTOR.
[2741] Sir,—I quite agree with your correspondents who have expressed their views on the design and construction of the present-day motor vehicle.
The methods that are being adopted on the majority of these seem to me to make it more difficult to have any repair carried out quickly. My experience—and that of a good many other mechanics—is that to take down almost any important part units which have nothing to do with the job in question have to be moved. I would even say that if the designers cannot improve on present-day methods I am afraid that in a few years' time there will be no mechanics to be found in any garages or workshops—they will all be in the lunatic asylums—whilst the owners of motor vehicles will be in bankruptcy as a result of their repair bills.
I could fill a book—and a large one at that—with notes regarding the inaccessible points on a good many well-known makes of chassis, especially those from. the Continent. I only hope that the day is not far off when a Society of Motor Mechanics will be formed to co-operate with the makers.—Yours faithfully,
J. LAMBELL, Works Foreman. London, S.W.
Problems of the Haulier and .Carrier.
The Editor, THE COMMERCIAL MOTOR.
[2742] Sir,—In connection with the "Haulier's" article appearing in your issue for February, 5th, it would seem that a charge of £15 per week for a 1-ton vehicle is excessive, and business is unlikely to accrue after quoting this figure. As a matter of fact, a recent quotation from a well-known haulage concern for a 2-ton vehicle was £465 per annum for a mileage of 12,000. Furthermore, I have received recent quotations on a weekly hire basis for 2-ton vehicles with a mileage stipulation of from 200 to 300 per week, at a charge of over 33f per cent. less than the 115 indicated in your article.
With regard to the suggestion that extra mileage within the working day should be charged at Is. per mile, I would state that very few transport users would agree to pay for excess mileage on a 1-ton vehicle at this rate, and I do not think that any haulier would have the temerity to suggest a charge of is. per mile for excess mileage.
I think you will agree that, aLhough it is very bad business for a haulier to under-quote, it is equally futile for him to over-estimate his quotation, and, indeed, if he obtains his vehicle on a hire-purchase system he would probably be out of business earlier through over-quoting than if he had under-estimated his quotation.—Yours faithfully, For the VACUUM OH, CO., LTD., London. W. Bull.
[Mr. Bish's letter indicates very dearly the parlous state of the haulage industry to-day; £465 per annum as the hire of a 2-ton vehicle covering 12,000 miles a year is insufficient; it will barely pay the cost of operation. The other qr-tations indicated by Mr. Bish are in line with this one. Better be out of a business than in it and working for next to nothing.—En.]