Opinions from Others.
Page 18
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The Daimler Tram,
The Editor, TEE CoMMERCIAL MOTOR.
[I,42.1] have 'read Aveimg's letter about, a l'annler train at strike time. I do not know under wie.ch of the Locomotives Acts it is claimed that these tr,Lins can be worked in the Ln 'bat tungdom, but am under the impression that they use the road On sufferance " at present. Of course, when a big strike is in progress, the police are too busy to bother with an odd road train or two, but the running of any frequent service would, I think, need to be regularized as regards licences, etc. :Has this matter yet been considered I Again, is it likely that very many buyers of road motors will be able to provide 15-ten or 20-tun loads for point-to-point delivery ? If not, the ordinary five-ton motor lorry should pay much better, and fail to see how the Daimler train can score. It is very costly to buy, and it needs at least 15 tons of paying load to bring it within the range of commercial employment.
I may say that I am basing my views on your various articles upon haulage data, and upon an article which Mr. Joynson-Hicks, M.P., wrote in your columns on the legal situation./ours faithfully,
H. J. WILLIAMS.
;The Daimler Co. has good ground$, our JuidgmenL, for anticipatinl; es.,1 change in the Law.Eu,I Standardization of Tires and Wheels.
The Editor, THE COMMERCIAL MOTOR.
L1,424 Sir,—We think it would be interesting and not a little instructive, to have the views of your many readers on the quesvion of the standardization of band-type solid-rubber tires, and the diameters of the wheels for same.
As manufacturers, we find not a little difficulty in offering alternative makes of tires to our clients. owing to the tire manufacturers' quoting different diameters of steel wheels as being most suitable for their tires—the latter being all of the same nominal size. Particularly do we find this the case, now that the use of cast steel wheels is becoming general. It is almost essential to stock such wheels, owing to the delivery difficulties experienced in this class of foundry work, and for manufacturing reasons it is necessary that these wheels should be turned to exactly the same outside diameter.
Taking a range of manufacturers, the variation in the diameters of steel wheels required for the same usual sizes of tires amounts to over a millimetre. In the more-unusual sizes, the variation is much greater. It seems to us that this variation, though small, is very undesirable and wholly unnecessary, both from the point of view of the motor-vehicle manufacturer and from the point of view of the user. In the latter ease, it may quite well be that tlie diameter of the wheel is such that no other make of tire than that originally fitted can be used, and it is expensive for the user to change from one tire to another if he is dissatisfied with the service he is getting. It is a fact, that, in the sizes of tires where competition is keenest, the various tire manufacturers are nearly agreed as to the diameters of suitable steel wheels. It is. therefore, reasonable to suppose that the tire manufacturers would find complete agreement. as to standard sizes to be to their advantage. We see no reason why the same dimensions should not be used by all the tire manufacturers for the same size of tire, and not only for the same diameter of tire, but also for a range of tire widths. For instance, a steel wheel of, say. 720 mm. diameter ought to be uurreet to take tires 850 by b5, 86J by 90, 870 by 100,
1375 by 115 and 880 by 120 mm. turtier than this, it seems to us that the number of different diameters of
tires listed for any section is, in general, unnecessarily large, and it might be expected that, if the tire manu facturers were to reduce this number, there would he a decrease in the price of the usual size of tire, simply owing to the larger quantity of the same size of tire which the manufacturers would naturally be turning out. For all practical purposes, we think tires of approximate diameters of 34, 36, and 40 in. would be all that is required. To induce purchasers to adopt
standard tires, it would be to the advantage of the Lire-makers to offer these at specially low rates.—
Yours faithfully,
ALBION MOTOR CAR Co., LTD_., T. TILAexwoon MURRAY, Managing Director.
Seotstoun.
(We titian Si, happy to -give spare to the views of both makers and I Alvers. En .
The Use of the Governor with Commercial-motor Vehicles.
The Editor, TEE COMEERcIAL MOTOR.
11,423] Sir,---The theory of controlling the speed of various kinds of road engines by means of a gover nor is a very old one, and I have even seen a steam road roller, rolling in metal on the level, controlled by these means, but not for long. The advocates of this method of controlling commercial-motor vehicles hold that a driver who is late will always press his vehicle to the utmost and thus do a considerable amount of harm to the vehicle he is driving. They therefore recommend a governor which will only allow the vehicle to run up to a certain speed.
Let me now discuss the working of a governor as applied to a commercial vehicle driven by an internal-combustion engine. The number of revolutions per minute is a vital condition controlling the horse power of such an engine. If the regulator valve is controlled by a governor, the opening and shutting of the same will be dependent on the number of revolutions made by the engine, i.e., if engine revolutions are nil then valve is full open. If the governor is set to shut the valve when the engine reaches a speed of 750 r.p.rn., then, when engine has attained a speed of, say, 190 revolutions, the regulator valve will be only open, say,25 per cent., and so on in proportion.
Now we all know that an internal-combustion engine of small power requires speeding up to obtain maximum efficiency, and that an appreciable number of revolutions has to be made by the engine before obtaining the immediate result of a fullyopened throttle. If, now, the regular valve is dependent on the revolutions of the engine, so soon as the necessary speed is obtained by the engine the governor begins cutting out before the engine has taken up its load, and, remembering the fact that a small engine is being used, we must, to obtain its full efficiency, drive it at its maximum speed. With governed engines on commercial-motor vehicles,
occasions will arise when the governor must be ac celerated, and it follows that, to get the full efficiency from a governed engine, an accelerator must he fitted. If an accelerator is fitted, of what use is the governor ? If a driver is late he will fix down his accelerator and there will be the unnecessary wear and tear and worry of a useless governor, flow much more simple to let the driver control the eniine.—Yours faith
fully, " !NOT CONVINCED."