My Views About Solid Rubber Tires.
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In Continuation of Those Expressed in Another Article dated 12th September.
By T. C. AVELING, Assoc. M.Inst.C.E.
I concluded my last article by summarizing the means to be taken, in order to obtain the best results from solid rubber tires. I now propose to consider the items of that summary in further 'detail. In the first place it is advisable, I wrote, to have all wheels of the same diameter, and all the tires of the same section. The tires can thus be changed from the front wheels to the back with facility. All the best results obtained from pneumatic tires have been obtained from changing the front wheel tires to the back wheels, and not as one would at first think, by changing the back tyres to the front wheels.
Normally if the front wheels be kept in proper alignment, and all users should give more care to front and hind-wheel alignment than is the general practice, the first tire to go on macadam roads is generally the inside twin hind tire on the right-hand wheel. The user's general method is to instruct the tire maker to replace this tire with a new one, so necessitating a pair of twin tires on the hind wheel ; the user then has one spare half-worn tire for stock.
A better method is to take off a front-wheel tire that has worn down to the same periphery diameter as the sound band tire of the back twins, to have the new tire fitted to the front wheel, and to have the half-worn tire from the front wheel fitted in place of the worn-out half twin tire that has failed. This pi:events holding a depreciating stock and more average mileage will be obtained. Tire guarantee is generally given for 10,000 miles over 12 months from date of supply. Therefore, if you have to stock a tire say three months, there is only a nine months guarantee left in which to run out the 10,000 miles, or a proportion of these figures. Many vehicles will do this, but a higher average than 50 miles a day, for five days a week, will be necessary to obtain full guarantee benefit. over the period.
Next, with regard to size of sections and to the advisability of employing as large a section tire as possible. The extra cost of a larger section of tire is a matter of a few pounds per set, but the increased life of the tire reduces the total cost per mile, gives a greater resiliency to the vehicle, and ensures fewer delays for time occupied in changing the tires, since the need for renewals does not occur so frequently. Of course, the section could be sufficiently enlarged, so that it would be impossible to run out the tires in the guaranteed period, but it will be found that the increased mileage obtained from the larger tire more than compensates for the extra outlay.
With regard to the desirability of all tire makers having numerous re-tiring depots, the need is obvious, dispatch in placing a worn tire being highly valued by the user. But to the tire maker it is most important, since it gives his representative an opportunity of examining the alignment of the wheels and keeping in touch with the actual users of such tires.
Although speedometers and mileometers are usually supplied by the maker of the vehicle, the actual measurement of mileage is a most important point to the maker of the tire. A high percentage of mile age is lost where the tire makers take on a guaran tee under an estimated mileage. In some instances old carrying firms such as railways, etc., have brought forward as evidence of their mileage, the map measured routes of their horse vehicles. This may approximately corer the mileage, but work out your
mileage from a map and estimate what you consider the mileage, and you will be surprised to find the number of miles lost, when compared with the reading of an accurate mileometer.
The fitting of a speedometer on the front wheels is a constant source of trouble with a commercial vehicle. All speedometers. if possible, should be driven from the propeller shaft or from its equivalent. Most speedometers require to be driven at a high speed, but a mileometer can be driven by means ef a scroll and pinion giving a much longer life to the drive on an instrument of this kind. A revolution counter on the engine, with the speed of the road wheels, when driving on different gears, marked on the face, would seem to be a better method than the combination of mileometer and speedometer ; moreover, when the speedometer broke down the separate mileometer would still continue to record the mileage.
I consider that the efficiency of a mileometer often fails, due to the drive required by the speedometer. Whereas the speedometer reading is only of a transitory nature, the mileometer is of a serious constant financial importance. I therefore maintain that the drives of the speedometer and of the mileometer should be separate, and self contained. The speedometer is an instrument introduced for use on passenger vehicles running on pneumatic tires, and, although the mileage is important. with passenger vehicles, it has not the financial-contract importance that the mileometer has on a commercial vehicle. Moreover, there is no need for the mileometer reading to be within the driver's vision, which condition is a necessity for the speedometer.
The constant supervision by the tire maker of the loads carried by the vehicle having guaranteed tires, is naturally of the utmost importance to the tire maker. It is also of importance to the user, since overloading will tell on the vehicle and will show its results in high running costs. Overloading of vehicles is also of vital importance to the road authorities, since, if there be no limit to the load, then there never will be any limit to road upkeep expenditure. The road authorities have powers to weigh vehicles, and it is in the interest of the tire makers, the vehicle makers and the ratepayers to stop overloading. No properly organized business sends out a load without knowing the weight of same. Guarantors of rubber tires should make it part of the contract that the weigh sheet or the consignment book should be open to their inspection at all times. With goods in bulk the checking of weights is an easier matter. When tires are guaranteedfor a certain vehicle, the tire makers should have the cubical area of the body fitted to the vehicle submitted to them.