A TUBE WITH POCKETS OF COMPRESSED AIR
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A New Tyre Filling of French Origin, in Which Cells Filled with Compressed Air are Moulded.
ALTHOUGH enormous sums of money have been spent during the last fiveand-twenty years in experiments with unburstable and unpunctnrable inner tubes, and countless "tyre fillings " have been brought out, nothing as yet has even started to oust the standard type of inner tube from its position. A French invention known as the V.P. appears to have real possibilities. It has been on the market now in France for some two years, and is gradually becoming better known.
The construction of the V.P. inner tube is most ingenious. It. is not really a " tube " at all, although it has the outward appearance of one. The arrangement comprises a number of small chambers or ballonets moulded into the outer form of an inflated tube. The ballonets are first all inflated to an equal pressure, this pressure being regulated to the weight of the vehicle in the tyres of which the tubes are to be used. After the inflation of the chambers the -whole mass is viicanized. As may be imagined, the inflation of the ballonets before vulcanization is a somewhat difficult and delicate operation, and the inventor of the V.P. states that he spent over 14 years in experiments before finding a
satisfactory method of making the tubes on a commercial basis.
In appearance the V.P. tube resembles any ordinary one, except for the fact that till) surface before the tube is inserted in the cover shows a series of very light protuberances, each one indicating the position of one of the inflated cells or ballonets adjacent to the wall. Should a puncture of one of the surface cells occur when the tyre is in use, the adjacent ballonets bulge outwards into the space occupied by the punctured one and support the cover. In the case of a bad gash or tear in the cover and "tube " opening up several of the cells, the vehicle can still be driven home and the tube then extracted and sent to the works for repairs. The external cross-sectional area of the tube is slightly larger than the internal area of the cover, so that when the latter is put over the tube it provides a pressure supplementary to that exerted on the air contained in the cells of the tube. Our illustration (No. 1) shows the bulging of the tube which would result from the cover being cut away.
A tyre fitted with the V.P. tube feels exactly like a normal well-pumped-up
pneumatic. There is none of that dead feeling which one associates with some tyre fillings Of the rubber sponge type.
The V.P. tube is naturally somewhat heavier than a standard type of inner tube, but the difference in weight is not nearly so great as one might imagine. The increase in weight should be compensated for by the real advantages which appear to be offered by the tube. There is something very attractive in the idea of buying your inner tubes ready .blown up, with the knowledge that they will temain so indefinitely.
The fact that the pressure in the tyres remains invariably the same is said to have a considerable influence on the life of the covers, and one can well believe that they should last longer in the circumstances.
A number of 43-seater motor coaches have been running in Paris and the district for some twelve months past, fitted with the V.P. tubes, and the proprietors state that the tubes are standing up well. It is possible that V.P. tubes may he seen in London shortly, as the L.G.O.C. are said to be putting them to tests.
The address of the makers is :—Chambres a Air V.P., 3-9, Rue Trezel; Levallois, Paris.