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A CHANGE GEAR INDICATOR.

4th September 1923
Page 28
Page 28, 4th September 1923 — A CHANGE GEAR INDICATOR.
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Which of the following most accurately describes the problem?

A Résumé of Recently Published Patents.

rro MANY of us the sense of touch

is the sorest guide to the operation of changing gear. After a tune, the expert driver almost dispenses with that aid, and changes his gears without a sound, at the right moment, instinctivejy. There are many who. drivecars, however, who never pass the first stage of dexterity in this operation.

As should be known, at the time when one gear is disengaged, the pair which will neat be enmeshed are revolving at different speeds, and, what is more important, their teeth are passing each other at a relative speed, one to the other, which forbids their engagement. The correct method of effecting a change is to wait until those speeds of the

• teeth of the wheels which are to be en , meshed are equal. This may involve • speeding up one wheel by the process of temporarily re-enga,ging the clutch, an operation which is technically known as double-clutching: it is most often required when changing down.

Whatever be the means of attaining that equality of speeds, its existence is only known either instinctively, in the case of the driver of long experience and unusual capacity, or by the sense of touch, snore or less delicately exercised. There have-been devices placed upon the market whereby the right moment for , effecting a change is positively indicated, and there have been gearboxes which, by means of mechanism incorporated with the gears, actually delay the change, subsequent to the driver's operation of the change-speed lever, until that moment has arrived. Specification No. 201,093, for which A. D. MacLean is responsible, is of the former type, and has at least the merit of simplicity.

He fixes a speedometer drive at each end of the gearbox: that at the front registers engine speed, that at the back, being to all intents and purposes, on the propeller shaft, registers speeds in miles per hour. The indicator dial accommo -dates two sets of figures, in addition to the usual total and trip mileage registers. One set indicates miles per hour, as usual, the other shows revolutions per minute. On the end of the flexible shaft from the drive which is located in front of the gearbox, one finger only is secured : it appears as a black one on the accompanying illustration. The other flexible B461 shaft carries four fingers, one for each change of speed which is afforded by the box. Their mounting on the end of the shaft is such that they can be adjusted in accordance with the speed ratios of the box on the vehicle to which the indicator is to be fitted.

One of the four, that which relates to the direct gear in the box, is longer than

the others. It reaches to the figures on the dial which indicate miles per hour, and serves the purpose of a speed indicater. Bars on the fingers indicate, by their number' the speed—first, second, etc.—to which they refer.

Any particular gear is ripe for engagement when the engine indicator finger lies over that finger which relates to the gear in question, so that, for example, if a change from top to third is intended, the procedure is as follows. Before declutching, the revolution counter finger will lie over the top speed finger. On disen gagement of the clutch, assuming the engine speed remains the same, the car will commence to slow down, and the top speed finger will fall away from the revolution counter, or engine finger. The clutch is then engaged, and the layshaft speeded up until the third speed finger lies tinder the engine finger. The gears are then ready for engagement, which should be effected, and can be effected, easily and noiselessly.

Other Patents of Interest.

Specification No. 200,955, by H. O. Clark, relates to a uniirersal coupling for use between the drawbar and axle of a trailer which is fitted with Ackerman steering gear which is operated by the movement of the drawbar. The object of the coupling is to allow of proper action of the steering gear uninfluenced by any movement of the axle relative to the frame. The axle may move nearer to the frame, or farther away, under the influence of the operation of the springs, or it may move longitudinally or transversely relative to the drawbar, and still not interfere with the operation of the steering gear.

An interesting detail of a power-operated brake gear is disclosed in specification No. 196,250, by the Westinghouse Brake and Saxby Signal Co., Ltd. A secondary ring is mounted on a sleeve on the steering column so that it is easily within reach of the fingers of the driver of the car as he holds the steering wheel. Movement of the sleeve up and down the column operates the valve which controls the admission of air to the brake gear.

A simplified control for the front-wheel brakes of a car is described in specification No. 200,875, by G. H. Lanchester and the Lanchester Motor Co., Ltd. A transverse articulated rod, carried in suitable bearings under the front axle, bears at its ends vertical pins which, when the brake gear is in the non-operative position, are in line with the vertical steering pivots of the wheels.. These pins are quite short, and carry at their ends plates which engage the plain ends of the brake shoes. It is claimed that with this arrangement, when the brake is in action and a steering motion is imparted to the wheels, the brake is automatically slackened. When the brake is not. in action and the axis of the brakeoperating element is in alignment with the axis of the steering pivot, movement , of the wheel about its pivot has no effect ' on the brake-operating element. When the latter is in action, it is slightly indined to the axis of the steering pivot, 'which ca-uses the effect desired.

Another detail of front-wheel brake operation is described by Sir Herbert Austin in specification No. 200,908, in which reference is made to a chassis construction wide' embodies a transverse front spring. The axle in such a construction is maintained in proper relation to the chassis by means of a torque or radius rod which, in this particular construction, is attached to the axle near its ends, and to the chassis by a universal joint. or joints. The invention consists in the arrangement of the operating gear for the front-wheel brakes so that the reaction of the braking is taken by the front axle radius. rods.

A modified construction of the venturi. passage of a carburetter is described in specification No. 200,994, by Societe du Carburateur Zenith.

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