RUBBER SURFACING FOR MAIN ROADS.
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Some Early Experiments and Others of a More Recent Character in Rubber Paving and the Conclusions so far Reached.
PrHE USE of rubber block .s as a
paving for main roads in districts where the traffic is of the heaviest is certainly a bold step. In this, the. Borough of Southwark was a pioneer. The trials a different forms of blacks for this purpose can hardly be said to be entirely satisfactory, except that they were instructive. earlier forms, as may be expected in such a wide departure from usual practice as this, diet not
prove auccessful. The difficulty, as might be expected by those who have had experience in rubber work, arose in attaching and securing the upper layer of •rublaer to the base. We have followed the experiments with great interest from the. first, and are able to give here a complete history of all that has been done, showing where the various devices failed and what steps haye been taken towards success.
The first attempt was a block of wood dovetailed as shown in Fig. 1 in "Methods of Mounting." Into these dovetails was fixed the rubber block, which was formed with a soft upper 'surface and a hard base, the latter carrying the dovetails which engaged those in the wood block. A section of this form of pavement was laid. in 1913 in the Old and New Kent Roads, where the traffic is bath fast and heavy. This patch of rubber pavement had been under trial for on year and nine months, carrying a traffic averaging over 190 tons per yard of street width per hour, when it was decided to take it up for examination. It was found that considerable wear had taken plate. in the dovetails between thp wood and the rubber. The upper surfaee of the rubber showed practically no signs of wear, a few scratches being all that could be noticed. The worn blocks were placed side by side with new ones, and no perceptible Wearing away of the surface could he seen.
As might have been expected, and, of course, was, the trouble had been in the junction of a .flexible material with an inflexible one.
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• The next attempt was with a rubber black with a soft upper face and a hard back, the latter being formed of hard rubber vulcanized into a plate of steel having holes bered through it to form a tooth for the vulcanite (Fig. 2 in " Methods of Mounting"). These steel plates were provided with prongs, which may be seen in the photo. These prongs were forced into a block of concrete. Here again the junction of the cement Rubbep
flexible and inflexible seemed to be the seat of trouble.
A third pattern shown at Fig. 3 in "Methods of Mounifng" was tried. In this form a plate of expanded metal was used as a backing for the vulcanite. This plate was like the other steel plate, mounted on a block of concrete. Difficulties arose through the vulcanite forcing its way through the expanded metal, breaking up and generally showing that flexible and inflexible materials do not agree well together.
It was then decided to try and elimiu
ate all steel and similar materials from the blocks. The latest form of block is shown in our illustration, entitled." The Latest Type of Block." This block is farmed. entirely of rubber. The lower portion is of waste rubber of a very hard nature capped with softer rubber as shown in Fig. 5, in which the sections of the blocks show the grading of the rubber. It will be noticed that the sides of these blocks are tongued so as to en
gage each other, and so to minimize any possibility of independent movement of the blocks. These lalocka are on trial in High. Street, Borough, and a section is to he seen in Little St. Andrew's Street, Holborn.. The position chosen for experiments in High Street, Borough, was a wise one, as the trial patch is exactly, opposite a police station. In our illustration of the laying of these blocks in Little St. Andrew's Street the tongued sides can be plainly seen. A flux of pitch is being used in the setting of the blocks.
It was anticipated by some that, a rubber road surface would be dangerous when wet, and that for horses and wheels the surface would not offer sufficient adhesion. The experiments, however, entirely disproved this theory. It was found that, in this part of the roadway, true imprints of horse shoes could always he found, whereas, in other parts, a slight slip was usually noticeable.
As a proof of the wearing qualities of rubber, can one imagine any other substance in the world which would. form a tyre for a commercial vehicle which would endure for the mileage to which rubber tyres are subjected? The question then arises—if rubber is best for tyres, why not for roads? As a proof of the wear-resisting properties of rubber, a certain underground conveni021100 near the "Elephant and Castle," where a narrow stairway receives perhaps the most severe traffic of any place in London, every kind of patent tread has been tried during the last 25 years, without success. Rubber was at last tried, and up to now has proved by far the most satisfactory tread in all ways. Although the number of horses is fast diminishing, there are still many left. The noise of horses' hoofs still adds to the general din of the London streets. This would. 'entirely disappear Were rubber used.
The item of cost is, of course, the greatest objection to the use of rubber for roadways. It is, however, a matter of its lasting qualities which should be considered, and it is not impossible that rubber may prove itself to be the cheapest pavement in time.