The Simplex Pneumatic Hub.
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A Resilient Wheel of Undoubted Merit, and Probably the Only One Which Has Received the Licence of Scotland Yard.
The interposition of an air cushion between the body of a wheel and the axle on which it rides is by no means a new idea, but early efforts to obtain a resilient wheel by such means were attended by failure. The chief object of their inventors is the production of a. wheel that possesses most of the advantages of the ordinary form of pneumatic tire whilst eliminating its recognized weaknesses. The Simplex Pneumatic Hub Syndicate, Ltd., of 1.16a, Queen Victoria Street, E.C., claims to have produced such a hub, and has tried it on several types of motor vehicles ranging in size from a motorcab to a motorbus.
The accompanying illustrations will serve to show the details of its construction, and from them it may be Neen that the Simplex hub differs radically from other forms of pneumatic hubs: the air cushion is free to alter its shape according to the variation of the load imposed upon it, and the movement is localized to a definite pertion of the air cushion—the part which corresponds to the tread of an ordinary tire. This localization affords a maximum of resilience with the leastpiesible amount of movement between the various layers of fabric and rubber of which the walls of the cushion are made : chafing of the material and the actienItion of heat due to friction are, tit erchy. minimized, and the Bre of the cushion enhanced.
There is nothing unusual about the main portion of the huh, except that a deep flange projects from the inner end (A' the central sleeve, or hub, and bete een the hub and the flat surface of the :flange there is a cup-shaped annular cavity (C). A similarly-shaped flange (Al) is fitted over the central eleeve, and this flange is securely fixed by means of nuts on shouldered studs (Cl) so as to maintain a definite dis
tance between the two flat faces of the side flatfeet.; the body of the wheel is
made a sliding tit between these two flanges, and it " floats " on the air cushion (B) which is housed in the annular cup-shaped cavities of the two flanges. The wooden spokes are wedgeshaped at their inner ends, and before they are assembled the ends are deeply mortised so that they may finally be fitted and glued into a circular ring. A pair of angle-steel flanges (C2), integral with which are a number of stout keys, or feathers, are then fitted to the wheel body; there are also a number of keys (C3) fitted on to the central sleeve, and these two sets of keys engage with transverse slots in the outer and inner circumferences respectively of the air cushion (B). The air cushion, therefore, not only sustains all imposed loads on the wheel, but it absorbs many of the shocks due to inequalities of the road surface, and, further, to a certain extent, it acts as a spring drive. The cushion is built up in the same manner as a single-tube pneumatic tire, and it may be inflated to any desired pressure, the air being forced through the valve B2 by assails of sin ordinary tire pump.
When heavily loaded, an ordinary pneumatic tire obtains a large bearing surface on the road, only by reason of the flexibility of its side-walls; in other words, its sides bulge out and thus permit more of the relatively-stiff tread to be flattened down on the road surface. The increased urea is available to support the imposed weight, although the air pressure inside the tire remn ins virtually the same. With
• a pnerimatie hub, however, there is no reason why the air cushion should be allowed to bulge out sideways, and it is with the object of preventing it that, in the Simplex hub, the flanges C and Al are made to fit up tightly against the side, walls of the air cushion. There is nothing to prevent
the cushion's " tread " being made thinner than is necessary with a pneumatic tire, whilst many advantages are to be derived from making the cushion wider and a leas depth. Such a shape, as the crass-sectional view shows, permits of a considerable amount of motion in the desired direction without imposing undue stress in the walls of the cushion, and thus the supporting area of contact between the cushion and the wheel centre may vary over a wide range without seriously heating the fabric. It should he noticed that the.' tread "(133) is considerably narrower than the air of the cushion. The air cushion play: precisely the same role as a pneumatic tire, since the displaced air " rolls round inside, and the degree to which that displacement takes place depends upon the weight carried by the axle.
The Simplex Bub Syndicate has made extended trials with various sizes of its hubs, and amongst those tested were sets on a motorbus weighing 6 tons 13 cwt., motorvans carrying
up to three tons, and taxicabs. A Unic taxicab. with Sintplex hubs fitted to all its wheels, has been in public service since July, 1909; a second motorcab—the 'lumber illustrated herewith—ha,s also been fitted with Simplex hubs and has received the blessing of Seotland Yard. One of our representatives recently was driven over several miles of stone setts, bad wood pavement, and many tramway points and crossings, in a landaulet whose wheels were fitted with these hubs—the rims being shod with smallsection Shrewsbury and Challiner solid tires, and be was very-favourably impressed with the ease of riding which. while not so comfortable as pneumatic tires, certainly gave sufficient ease and comfort for any commercial vehicle, taxicabs included. The Unic cab abovo mentioned iS now being overhauled fu; the first time since the hubs were fitted, a fact which appears to contra
verb any suggestion that the chassis must suffer if pneumatic tires are not employed.
The tire cost of a commercial vehicle
is a not-inconsiderable item, and any invention which tends ro secure increased economy, without sacrifice of resiliencv, should be considered most carefully by all users of utility motors. The Simplex Syndicate guarantees its device for distances of from 8,000 to 10,000 miles, and, after the completion of that distance, the air cushions may be replaced for a very-small sum. The tires, too, are guaranteed for the same rnileagas by their makers. Mr. Menkern, the general manager of the Simplex Syndicate, informs us that he is prepared to enter into maintenance contracts at. prices as low as 14d. per mile for four wheels, the contract price to include air cushions. wheels, solid-rubber tires and hubs. Although their initial cost is somewhat higher than that for ordinary wheels and pneumatic tires, the increased life of the Simplex hub should weigh greatly in its favour amongst thoughtful users.