A ROLLS-ROYCE SERVO BRAKE.
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A Resume of Recently Published Patents.
WE HAD OCCASION, some little time ago, to refer, in these columns, to the advisability of commercial motor manufacturers studying the Servo brake, with a view to its adoption on the heavier type of vehicle, particularly the motor coach. In furtherance of that view, we have pleasure in being able to describe, this week, a new design of brake of the type named, which has been patented by the foremost makers of touring car chassis in the world—Rolls-Royce, Ltd.-in a specification which is numbered. 191,779. 'This interesting forns of brake gear is applied to a car having four brakes, all operated by the one pedal or hand lever ; the inventor's principal object is to avoid any uneven braking effort, to ensure that the same retaroatory force is applied to each wheel, and to provide against total failure of all the brakes in the event of only one of them being deranged. The gear itself• is an interesting adaptation of the principle of the disc clutch. It is mounted within a bell-shaped casting, which is an extension of the gearbox, and is carried on the boss of the universal joint, which is immediately behind the gearbox, the said boss being splined so as to be the means for driving the two driving discs of the clutch, which is an important part of the device. There are, as it were, eight discs in all, and of these the fiair driven discs are the most interesting. They are mounted on ball bearings on the boss of the universal joint, and each is grooved to accommodate a brake-operating-cable, which is secured to the disc in each case. One cable Is allotted to each of the four brakes. The brake pedal closes the clutch, which causes the brake to be applied either by engine power, if the gears are engaged, or by the momentum of the car if they are in neutral.
It will be realized that this device operates as a brake cornperiaating gear, since, in the event of one brake being applied more forcibly than the other three, the pull on the cable would exceed that on the others by the same amount, but, as the same pressure is transmitted to all four discs, that one with the excessive pull on the cable would tend to slip until the pressure was equalized. It is equally clear that the freaking of one cable would not prevent the remaindea front uperating.
Other Patents of Interest.
An interesting and novel method of grooving solid-band tyres so as to increase their resilience, and at the same time to improve their non-skidding properties, is described in specification No. 185,130 by the Goodyear Tyre ind Rubber Co. The principal feature is 'the varyi»g depths of the grooves, which are deepest at the middle of the tyre, and taper out to a
minimum depth at the edge. • The inventors point out that it has hitherto been customary to make such grooves of uniform depth across the full width of the tyre. This had, as one effect, a less yielding tread surface—considering the tread surface as being mainly the portion of rubber between the grooves —in the middle than at the outside edge of the tyre, mainly on account of the greater confinement and resistance to expansion of the middle portions of the tread. It was necessary in such circumstances to keep the grooves fairly shallow, in order that. the projecting portions of the rubber should not be deB44 stroyed or mutilated by the lateral thrust, on the tread surface. With grooves of varying depth, as devised in 'connection with this invention, this difficulty does not arise, as the lateral shear is effectively resisted by the edges of the tyre, where the grooves are comparatively shallow, and where, therefore, the projecting portions are not fragile. The deeper grooves in the centre, however, allow of greater cushioning effect against the direct blows which are encountered by those portions of the tyre.
An invention of considerable interest to commercial motor users is disclosed in specification No. 191,883, by Herbert Lomas, Ltd. It,is concerned with tipping wagons, which, on account of the nature of the loads they are intended to carry, must be provided with hoods. In the design which is described in this specification, the rear portion of the hood is collapsable, and is so mounted; in conjunction with the tailboard of the lorry, that as the latter is tipped the back part of the hood is clrawn back automatically, returning to its normal position as the wagon body is restored to the horizontal.
Specification No. 191,976, by F. A. Nilsson, refers to that 'typo of vehicle which is supported at the rear, and also driven, by mechanically operated legs instead of by wheels. The invention is mainly concerned with the operating gear for the legs, of which, it. is stated, only two are required at each side of the vehicle or tractor. Ingenious cam gearing, supplemented by an epicyclic change-speed gear automatically controlled, provides that the movement. of the fOot when in con tact with the ground is slow and even, whilst it travels quickly on the idle stroke from rear to front, in order to assume a new working position.
An ingenious form of anti-vibration and shock-absorbing suspension for a battery box, or other accessory of a motor vehicle, is described by the Bristol Tramways and Carriage Co., Lid., in specification No. 191,834. The box is held at each end by a pair of parallel cantilever springs. The result is to limit the movement of the box to the purely vertical, • and at the same time to eliminate entirely any need for lubrication of the suspension.
A simple method of controlling, by thermostatic means, the' now of the cooling water of an internal-combustion engine is described in specification No. 183,423, by W. E. Ernst. Its' principal advantage aPpeara to be that it is designed so that. it may be inserted into the circulation system of most existing cars. There are two circular ported discs, which are rotated, as the temperature varies, by coiled bimetallic plates, one to each disc. Means are also provided for occasional regulation of the device while it is working, and without the need for dismantling any part.
The clutch improvement which is described in specification No. 181,332, by M. J B. Barbarou, refers to a previous patent by the same inventor. It provides means for preventing rubbing of the clutch-operating levers against the clutch-operating collar while the clutch is engaged.
Another clutch invention, by T. Cooper, described in specification No. 191820, consists in the provision of radial grooves in the discs of a multi-disc clutch, which facilitate the circulaticn of oil and air.