MAINTENANCE OF GIANT PNEUMATIC TYRES.
Page 60
Page 61
If you've noticed an error in this article please click here to report it so we can fix it.
Some Useful Suggestions for Users for Ensuring Ease of Handling Heavy Tyres and for Securing Economy in Upkeep.
THE supersession of solid tyres by pneumatics, which has been one of the most striking of recent developments, has been largely due to the great improvement which tyre manufacturers have made in their products during the past year or two. Combined with this is the important fact that, as a result of discarding the old beaded-edge form of cover in favour of a straight-sided tyre, held in position by a detachable flange, tyre punishment during the fitting and removal operations has been entirely obviated, the result being that, even with axle loads up to 4 tons 15 cwt., giant pneumatics are now being used to an ever-increasing extent and with great success.
With the object of gleaning some information regarding the maintenance of the modern tyre, we recently visited the special depot which the Dunlop Rubber Co., Ltd., has lately opened at 120, Wicklow Street, King's Cross, London, W.C.1, whence the whole of the trade in Dunlop giant pneumatic and solid tyres, as well as all the business relative to maintenance contracts in respect
of tyres of any size or character, in the-London and Home Counties district, is dealt with. The premises are admirably suited for their purpose, and, in addition to offices and several small departments, comprise , a solid-tyre fitting shop with two Hollings and Guest presses, a large ground-floor store for solid tyres and an equally spacious warehouse for giant tyres on the first floor, in both of which departments a big stock of all the different sizes of solid and pneumatic tyre is maintained, so that any demand from the areas above mentioned can be promptly met. So far as the Dunlop giant cord straight-sided tyres are concerned, these are now being made in seven sizes, from 32 ins. by 6 ins, up to 42 ins, by 9 ins., the 6-in, size being suitable for axle loads from 30 to 45 cwt., the 7-in, for axle loads from 35 to 60 cwt., the 8-in, for axle loads from 50 to 80 cwt., and the 9-in, for axle loads from 65 to 95 cwt.
Whilst the fundamental principles of giant pneumatic tyres are the same as those applicable to ear tyres, for their successful use from the points of view of economy and cost of operation, commercial and public-service vehicle owners adopting them will do well to realize at the outset that attention must be given to the tyres a little more frequently and regularly than is the case with car tyres. As the Dunlop Co. points out, the tyre makers in supplying a tube and a cover do not furnish a complete pneumatic tyre, a third and important
constituent being the air within the tube, the responsibility of supplying and maintaining which at the required pressure being a matter entirely for the user. The tyre makers do their, share of the work by providing information as to the amount or pressure of air that should be.provided in a tyre of a particular size and for a certain load.
Even as regards the pressure to be adopted, there are three matters to be taken into consideration, first and foremost, of course, being, in the case of passenger vehicles, that of providing comfortable riding. ' The second point is that the pressure must be such that the tyre cover shall not bend excessively under the load and so cause rapid fatigue ; whilst, thirdly, the pressure must not be such as to impose so great a tension on the material of the tyre cover as to render it susceptible to damage by concussion.'
In this connection, it may be mentioned that the most suitable size of tyre for any particular vehicle is determined by the front and rear-axle weights with
maximum, axle load. One of the tyre-pressure gauge makers has recently been carrying through a "Test Your Tyre Pressure Every Priday " campaign. This is, however, only intended for private car owners. In the case of public-service and goods-carrying vehicles, the Dunlop Co. strongly urges that users should, in their own interest, test their tyres for pressure and restore any that has been lost every day a vehicle goes out on a journey.
Moreover, they recommend that, if between one day and another there has been a loss of pressure of even only 5 lb., the tyre should be regarded as suspect and the cause of the leakage ascertained. Again, in order to secure the best results from giant pneumatics, users are advised to make it a rule to change one wheel every week, and to have the tyre detached from the removed wheel and both the cover and tube carefully examined and any cuts or other defects made good. At the same time, the rim should be cleaned, freed from rust, and, if necessary, repainted. By dealing with a different wheel from the vehicle each week in turn, the whole tyre equipment of a bus, coach or truck_ will thus be examined every four weeks.
Now that straight-sided tyres with detachable flange rims are the order of the day, no special equipment is necessary for the removal or fitting of even giant pneumatic tyres. Indeed, the hand levers used in CO/MCC
tion with the work are lighter than those supplied to manipulate car tyres in the early days of the motor movement, and, judging from what we saw in the tyrechanging room at the Dunlop depot, the task of tyre changing is one rather of knowing how to do it than one requiring any undue exertion on the part of the operator. The work is apparently most easily done with the wheel removed and lying on the ground, and, with the company's clearly illustrated instruction book, it should be possible even for a novice to experience no difficulty in changing a big 42-in. by 9-in. tyre.
Other Dunlop recommendations to giant tyre users, all intending to assist in securing satisfactory operation and long life, may be briefly summarized, some of them being advice of long standing, but frequently not followed. First, avoid overloading, the cost of which in tyre destruction is probably more than the square of the overload. Indeed, the Dunlop Co. considers that overloading actually means a loss rather• than a profit to the vehicle owner, and that it would usually be more economical to pay overload passengers to stay away! Secondly, keep garage floors free from oil and grease, so that tyres shall not be ruined by being allowed to stand on either. Fierce brakes and clutches, like any misalignment of the road wheels, can also be the cause of much unnecessary tyre wear.
One useful tip that should be borne In mind, especially as it is somewhat contradictory of an unfounded belief, is that the effect of air temperature on pressure should be ignored ; that is to say, the degree of inflation should not be reduced in hot weather. In the ()Pinion of the Dunlop experts if one tyre runs notably hotter than another it is evidence of too little air rather than too much.
Mr. P. W. Pope, the manager of the depot, also initiated us inTo the tyre inspection and report system which the Dunlop Co. has inaugurated in order to assist users of giant pneumatics in getting the best results from their tyres. A record is kept of all users, who are called upon at regular intervals by a staff of inspectors. The latter, after viewing the tyres on the customers' vehicles, send in their report to headquarters, where they are filed and a copy sent to the proprietor of the vehicle, or, in the case of a company, to the managing director. Only in cases where urgent repairs or other attention are deemed necessary do inspectors make direct suggestions to the users.
Although the maximum pressure in the biggest giant pneumatic tyre is only 110 lb. per sq. in., it is obvious that inflation by manually operated pump is both a long and somewhat laborious task, so that in the case of fleets of pneumatic-tyred vehicles some form of electrically or mechanically operated inflating arrangement becomes necessary. At the Dunlop depot in Wicklow Street, where, of course, a mains supply of electricity is available, this consists of an electric motor coupled direct to a Lacy-I-Tolbert water-cooled compressor, the whole installation, complete with air-pressure tank, occupying a recess measuring about 5 ft. by 2f ft,
The plant, which is on the ground floor, is connected up to a system of air pipes which have been installed along the walls of the building, so that tyres can be . inflated at four different places, three on the ground floor and one in the tyre-fitting section on the first door. Moreover, the plant is entirely automatic in action, a special device being provided whereby the electric motor and compressor are started, up whenever the pressure in the air storage tank drops below 85 lb. per sq. in., and are automatically stopped when the pressure reaches 120 lb. •
With regard to the repair of giant pneumatics, if has already been pointed out: that the life. of both covers
and tubes can be prblonged by careful attention. The Dunlop Co. regards the repair of cuts and small gashes in the tread rubber of covers as quite within the capacity of even small fleet owners, and for this purpose supply a handy electrically heated vulcanizing outfit.
On the other hand, except in the case of concerns having a fleet of vehicles sufficiently large as to warrant the establishment of a specially equipped tyre-repairing department, the company recommends, with regard to tyres with broken casings or fabrics or other damage which necessitates extensive repairs, that the work can best be undertaken by the tyre manufacturers, a special department at the Birmingham factory being set apart for that class of work. Although tyres needing repair are received and reported upon at the depot at Wicklow Street, no repairs are at present done there, all being sent to Ford Dunlop for attention.
The Dunlop Co. has during the past winter been busily engaged in assisting public service and commercial owners to change over from solid to pneumatics. Although we hope to refer to this subject more fully in a subsequent article, it may be mentioned that the company has obtained and collated much useful information on this matter and has established a special department at Ford Dunlop, Birmingham, for the production of such new parts as may be necessary.