OPINIONS FROM OTHERS.
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Editor invites correspondence an all subjects connected with the use of commercia.l.motors. Letters should be on, one of the paper only and typewritten by preference. The right of abbreviation is reserved, and no respon,sibility.for views expressed is accepted.
The side
Steel versus Rubber Tyres.
The Editor, THE COMMERCIAL MOTOR.
[1623] Sir,—I thank you for publishing my letter on " Steel v. Rubber Tyres," but should like to, point. out to you that your Editorial note at the end of same is hardly in order. I was quite aware when I wrote of the special wagon Sentinel made to run at 12 miles per hour, but you evidently have 'forgotten this is only registered to carry four tons. YOU. will note I said in my letter that if the load on either axle ex-, ceeds six tons then the wagon may go at 12 Miles pee hour legally. There is, however, no wagon built, and.
I can almost safely include the five-ton petrol.lorry in this, which can legally carry a five-ton load and have the back axle remaining under six tons. At any rate no five-ton steam wagon can do this. The Sentinel wagon you refer to is this company's special four-tonner.—Yours faithfully. "UNPREJUDICED."
Liverpool.
Relative Power from Gas and Petrol.
The Editor, THE COMMERCIAL MOTOR.
[1624] Sir,—In the article on the L.G.O.C.'s gas equipment appearing on page 492 in the' issue of THE COMMERCIAL MOTOR for 1st August, an interesting fact is commented upon, that is, that the power developed. in Using gas is equal to that obtained. from petrol. In this connection, I am forwarding a table, given below, which shows the result of experiments carried out on vertical stationary engines, one, two, three, four and six-cylinder, which closely follow the 'automobile engine design. These engines were tested without any alteration, except the addition of mixing valves or carburetters to suit the various fuels.
The speeds, it will be noted, are low for automobile work, but this would not materially affect the result. These tests confirm the statement that coal-gas can be used without loss, and, in some cases, a slight increase in the power developed as compared with petrol. The gas used in the case of these tests is of higher calorific value than that supplied in the London district, but this does not materially affect the case, as, naturally, the mixture in the petrol engine also varies considerably. The figures given for producer gas are interesting. It will be seen that as the size and power of the engine goes up, the loss on producer gas falls. As a matter of fact, from tests carried out on automobile engines, this loss is considerably reduced, as in the case of the engines on which the above tests were taken, the. valve areas, which were designed to suit the speeds at • which the engines were to run, were small, the loss on the automobile engines being 15 per cent. to 11 per cent., as against 20 per cent. to 25 per cent, in the above tests.
The fact,that the mixture of coal-gas and air is of lower calorific value than petrol and air, and gives better results, may at first seem remarkable, but it must be remembered that, when running on gas, the fuel is delivered to the engine with little or no "back pull." Therefore, a greater weight of working fluid per stroke is admitted to the cylinder with coal-gas, as against petrol, and this increased quantity of luol compensates—or more than. cOmpensates—for the lower calorific value of the fuel. It is quite possible, by delivering producer gas to the engine under a slight pressure, to reduce the loss on this fuel to a negligible quantity, although, with the many advantages resulting from the use of suction gas, even the losses as shown in the above table will not prove any serious drawback in use on commercial vehicles, where the full power is seldom required.—Yours faithfully,
DAVID SMITH, Major,
0.B.E., M.Inst.A.E.
False Economy in the Services.
The Editor, THE COMMERCIAL MOTOR.
[1625] Sir,—A case of what I consider to be false economy has come to my notice out here, and I think it may interest some of your readers ; if so, I should like their opinion upon rt.
I had a " lift " on a lorry which had another in tow, and, to my surprise, was informed that the rear lorry was in working order, but, being empty, was towed to save petrol. It is a standing order, in this A.S. C. company at least, that all pairs of unladen vehicles shall work in this way. It was observed that the second speed was necessary for very slight gradients, and in many cases the third was used for considerable periods, with consequent racing and heating of engine. No drawbar or similar arrangement was used, only a tow rope attached to the hooks of main frame members. It is doubtful if much—indeed, any—petrol is economized in this manner, and, in any case, the extra wear and tear of the towing vehicle would outweigh any gain of petyol. Both vehicles were of three-ton capacity.
There are other points to be considered, but it is not necessary to enlarge further.—Yours faithfully, ' B.E.F.
Reconstruction and Maintenance of Roads After the War.
The Editor, THE COMMERCIAL MOTOR.
[1626] Sir,—During the past year there has been a considerable amount of correspondence in the Press on the above question, and various criticisms and suggestions have been made, but with all respect I venture to suggest that the persons who have taken the matter uv are either interested commercially or are laymen without practical experience. The question is a national one, and will have an important bearing in the success of many trades in the future, and in the consideration of any schemes due regard will have to be paid. to the commercial requirements. It would appear from the views expressed by some critics that the authorities now in existence have failed to meet the requirements, and are not competent to deal with the question successfiffly at the termination of the war. I would like to put up a few questions :— (1) What is the cause of the present condition of the principal roads in this country? (2) Is it,a fact that the roads have collapsed? (3) Subject to the necessary ways and means being provided, are the present authorities competent to carry out the important work that will be necessary at the termination of the war ? The answer to No. 1 is simple to anyone who has been connected with the maintenance of roads. During the period of the war a gradual starvation has been proceeding in consequence of the inability to obtain the necessary material and labour, therefore it has only been possible tmconcentrate the strength on those roads taking the heaviest traffic. With regard to No. 2, I submit that the roads have not collapsed except in a few cases where the traffic has been of an extraordinary nature, either naval, military, timber, or munitions. Generally, the roads have stood the strain in a remarkable manner, which speaks volumes for the sound work carried out in the past. As to No. 3, I respectfully suggest that, subject to the necessary funds being forthcoming, and the return of the various members of our staffs who are now engaged overseas, the existing authorities are quite capable of dealing with the situation. At the time of the outbreak of war a number of county councils had extensive reconstruction schemes in progress in conjunction with the Road Board. The value of this work is quite apparent to-day where the roads are taking very heavy traffic, and the surfaces are still in excellent condition.
It must not be forgotten that the authorities have released the younger, members of the staffs to join the forces, and in particular the Road Construction Army under the direction of Brigadier-General H. P. Maybury. On the cessation of hostilities the maiority of these men look forward to returning to their old positions which are being kept open for them, and although it has recently been suggested that the necessary. reconstruction work in this country should be taken' over by General Maybury and his present staff, as an old county surveyor I do not think for one moment that he would wish to supersede the positions of Ms.-former colleagues who have been "carrying on" in this country under exceedingly di1lics41t conditions. Every surveyor appreciates the excellent work that General Maybury has done, and there is no reason why the good feeling that existed prior to the war between the Rued Board and Highway Authorities should not continue in the future.
• It is true that in the past there has been a .multiplication of highway authorities which might be improved upon by reducing them to one combined authority in suitable areas. This is a question of principle, which as a county surveyor it may be said I am not an uninterested party, and for that reason perhaps it is not wise for me to put forward any definite proposals. I do hope, however, that some credit will be given to those authorities and members of the protession who have been carrying on in this country during the period of the war under most trying conditions, and that when, the time comes to deal with important schemes they will have an opportunity,of showing what they are capable of doing.-Yours faithfully,
0. F. GETTINGS, County Surveyor, Worcester County Council.