A Promising Rubber Tyre for Heavy Vehicles.
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The several references to the running behaviour of the rubber tyres composed of separate pads or blocks, which are to be found in our several accounts of the recent French trials, held over the course Paris-Dieppe-Le Havre-Paris, have resulted in not a few enquiries for more information as to their manufacture and construction. The tyres fitted to three of the vehicles in these trials were supplied by the Societe Anonyme de Fabrication de bandages demontables (systeme Ducasble), 23, Boulevard Gouvion St. Cyr, Paris, but home enquiries should be addressed to the North British Rubber Co., Ltd., Castle Mills; Edinburgh. It is claimed—and not without good reason—that these tyres possess advantages peculiar to themselves and distinct from any that can be legitimately credited to any other design. In the A.C.F. trials, which took place little more than a month ago, five driving wheels had been equipped according to the "Le Francais" system. The heaviest vehicle upon which they were employed was the four-cylinder 24h.p. De Dion-Bouton lorry (No. 8). This machine carried a useful load of 3,100 kilos. and had a gross weight of 6,118 kilos.; these weights, it will be noted, corresponded fairly closely The Le Francais Tyre. with what we to-day find in motor omnibus practice, the back axle-weight being in the neighbourhood of 41 tons. For this reason alone, if for no other, the device calls for illustration and description.
It will be seen that the pads or blocks of rubber are disposed round the tread of the wheel in two parallel rows, and`that the spaces between the ends of any two sections in the same row are opposite the centres of the adjacent section in the other row. Each block is held to the rim by a caststeel frame-piece, which fits closely over the projecting rubber flange formed by its base, the retaining frame-pieces overlapping one another and being secured by nuts and bolts which are particularly accessible. The chief and incontestable advantages of the arrangement are the avoidance of heating and the ease of replacement. The reduction of stresses to a minimum has been gained by the division of the mass of rubber into a series of separate pieces, whilst the small amount of heat generated has every opportunity to get away both by radiation and conduction. So far as repairs go, as each pad is interchangeable, it is possible to pack away a few of them under the driver's seat, and there is complete, independence of the wheelwright or hydraulic press. Sideslip is reported to be unknown, and that claim appears to be well founded. The individual pads, coupled with their arrangement on the twin method, should provide enough, adhesion in all conditions of weather or road surface.
The manufacturers and vendors are offering the " Le Francais" tyres for three axle-weights-3, 4, and 6 tons. For the heaviest of these, each pad is slightly less than loin. long by about tin. wide, and the price per pair of twins varies from £84 for a 3210. wheel to „‘.112 for a 44in. wheel. The inventor is M, Chary, one of the principals of the Ducasble house. He has kept in mind the importance of avoiding breakdown on the road, from whatever, cause, arising out of tyres. A few minutes suffice for the replacement of a pad, and it is a remote contingency that any wheel will ever get into a state which can render the continuance of a journey impossible. Rectangular blocks have proved more satisfactory in practice than others put on diagonally, and recorded wear amounts to only one-fifth of an inch in 3,728 miles of running under full load.