• TRANSMISSION SYSTEMS.
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A Resume of Recently Published Patents.
ACCORDING to H. Alarchand the patentee of the invention which is described in specification No.-198,543, an ever-increasing difficulty which arises in connection with the modern tendency to fit high-speed engines to motorcars is that of. devising a transmission gear which, whilst affording adequate reduction between the engine and propeller-shaft speeds, will not involve The use of such large gearwheels in the rear axle as Seriously to reduce the ground clearance. So real and pressing is this difficulty, be states, that certain makers have actually had to sacrifice efficiency . by using engines of lower rotational speed, so that they can bring the dimensiCgiS of-the rear axle case within the regions of practical design.
A solution of thiS difficulty, he continues, has already been proposed-in the use of internally, toothed wheelit as meana of transmission, but there has been the disadvantage, in connection with the construction in question, that two such wheels have been necessary. • His invention obviates that difficulty,as well as others which have been encountered.
The internally toothed wheel in this case is of smooth exterior—it has to serve as a brake drum---and is bolted to the differential -casing. There are two pinions in engagement with it, of different diameters, and each of them is on the same Spindle as a worm wheel.
The worm wheels, too, are different. The propene' shaft carries two worms which engage with the two wheels; the worms are not keyed to the shaft, but are clutched to it, alternatively, by means of a dog clutch.
The arrangement provides a double reduction gear between'the propeller shaft and axle Shafts, as well as a simple form of two-speed gear. The design, as exemplified in the speci fication, embodies an interesting form of servo brake. The axle casing is extended in aforward direction, to enclose a pulley whit+ is keyed to the countershaft operating the internally expanding brakes on the rear wheels. These brakes may be manipulated in the ordinary way, by hand or foot, without interfering with the servo brake. A belt is fastened to the circumference of • this pulley, and passes thence round a part of that circumference, then round the exterior of the internally toothed wheel, through a slot. in the casing, and, forward to the brake lever or pedal to which it is at. tached in such a manner that operation of that lever or pedal will tighten the band upon the circumference of the internally toothed. wheel, causing the belt to force the pulley round and app ly the brakes. The whole arrangement is comparatively simple and extreniely ingenious, and we shall watch for its further development with considerable interest. The transmission which is described in specification No.. 198,271, by C. W. Eaton, is of the infinitely variable type. It embodies a simple epicyclic train, which is hydraulically controlled. The epic:ye:lie gear, as shown on the drawing . which accompanies the specification, is of the bevel type. The propeller shalt is keyed to one sun wheel, and the engine shaft to the other. The differential case carries an eccentric at one side, and a clip, mounted on ball bearings on the eocentric,.drives a couple of pumps which are. in communication with one another by means of a simple pipe, in which is inserted a control valve, the operating of which varies the passage in the pipe from full bore to nil. With the passage fully open, there is no restriction on the movement of the differential case, and
no power is, therefore' transmitted; the engine simply turns the casing round and round. AS the valve is closed, this state of 'things is progressively altered, until, with the passage entirely blocked, the differential case is held and top gear is reached.
Other Patents of Interest.
The object of the inventor of the steer. ing gear which is described end patented in specification No. 198,475, is that of providing a gear which shall give •the greatest sensitiveness of steering when the car is running straight ahead, -this sensitiveness diminishing as hill lock' is approached. The construction is best described in conjunetion with the accompanying illus, tration of the gear. The steering column carries on its end a-short lever, which is coupled to a floating lever. The latter is carried in a trunnion, as shown, the trunnion, for most effective operation of the gear, being located at the same dielance from the centre of the column as the length of the short lever on the end of that column. In the mid-positon, which is that illustrated, antivemerd of the steering column produces a comparatively slight movement of the steering arm, this movement increasingrelatively as the middle position is le..ft.
There are two specifications this week which deal with the construction of six wheelers of the tractor-lorry type. Both emanate from P. O. Flugh.anct C. Scam-swell and Nephew, .Ltd., and •Tootb relate to the some subject—the provision of stops for preventing the overturning of the load-carrying portion of such vehicles. . Specification No. .198,541 describes the method of adapting loops of flexible steel wire to the end in question. In one construction of the several shOwn and described, these loops are six in number ; four of them connect the ends or the four springs—those which support the turntable on the main axle of the
• unit, and those which support the frame of the tractor on the main driving axle. The other two loops connectir the main driving axle with pins on the springs Of the turntable. tinder ordinary working conditions the loops are loose, but when eXcessive movement would occur the loops prevent it, The other specification is numbered 198;542. In•the construction therein de-. scribed the same object is achieved by the use of looped brackets on the frame of the tractor Part of the, vehicle, the loops surrounding pins on the turntable, so that they permit normal movement but prevent, excessive motion