AUTOMATIC GEAR CHANGING.
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A Résumé of Recently Published Patents.
Drivers who can effect perfect and silent gear changes under ail conditions of running are still rare. The difficulty is mainly that of correctly estimating the precise moment at which the two gears which are to be engaged are revolving at the same circumferential speed. The operation demands not only a certain amount of skill, but, additioeally, some degree of intuition, and at least a perfect acquaintance with the -motor vehicle which is being driven. 11:J. Andrews has invented a Means of eliminating entirely the need for any of these e'en-lents. His method involves the incorporation, in the construction of the car, of an auxiliary gearbox, and he describes his invention in specification No. 148,029.
Thq construction of the auxiliary gearbox is not specifically defined in the patent; it may be apparently of any form, subject to the condition that it
• must embody a. range of gears the same in number, and practically the same in ratio as those in the main transmission. The ()riving shaft of the auxiliary box corresponds eo the clutch shaft of the car, and the driven snaftof the auxiliary box likewise oceresponds to the driven shaff of the ear. Each is coupleci to each; that is to say, the driving shaft of the auxiliary box is coupleu to that of the car, and the driven-shaft of the auxiliary is likewise coupled to that of the .main transmission, in both CMOs by Means of belt or chain. There are two frietain clutches to the auxiliary box, one on each side of it, and intervening between the gears in the box and the belt pulleys or
sprockets. These friction clutches are controlled by a combination of cam gear and springs, _se that the auxiliary box is only working when either the main clutch is disengaged, or the main change speed lever is in the neutral position.
The method of operation is as follows: Assume that the car is running along and The need f6r a change of gear is anticipated. The change is first effected in the -auxiliary --leog—lay what means is
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not stated. Later, when the actual time to effect the change in the 'main box arrives, the clutch is disengaged. This operation automatically starts ap the auxiliary box, by engaging the driving clutch, through the medium of the cam gear. When the main change speed lever is put into neutral position the-auxiliary box begins to affect the relative speeds of the driving and "driven 8hpits of the main transmission, and rapidly brings them to the state of revolving at the correct speed for the engagement of the main gears. Movement of the main change speed lever into the new peeltion, and engagement of the main clutch, automatically disengages the auxiliary bog, which cea.ees 10 rune and remains
quiescent until the time approaches for a further change of gear. It is pointed out that the arratigareent is also advantageous in other ways, as tfor .example when coasting with the chaage speed gear in neutral position. The.auxiliary box under those conditions keeps the driving and driven shafts of the main box revolving alwaya-at the correct speed for re-engagement, which is therefore effected easily and without clashing of gears.
Other Patents of Interest.
A familiar difficulty in • connection with the design of automobile engines which are equipped with large. valves is the form of the combustion chamber for reasonably high, compression pressures. Owing to the space required by the Large valves there is generally almost sufficient volume round about them to provide for a combustion chainher', and in consequence the space above the piston is necessarily vary shallow. Specification No. 148,046, by H.' IL Ricardo describes a construction of eirEnder head which kurmounts the difficulties, and provides a combustion chamber shich has advantageous features. The combustion chamber is farmed as a sort of pocket extending over the top of the
valves, and also over a pertion of the
cylinder. adjacent to the valves. The cummunication between the chamber and the cylinder is by Means of a passage, the cross sectional area of which is approximately the same as. that of the valve ports. The construction favours increased tuabulenoi in the gases.
Specification No. 148,007, by E. B. Killen, refers to the tyres which have been described both in this page and in the general columns °Ode paper arum. time to time. In the construction outlined in this specification the rim. of the wheel is formed with a eircuinfe.rential channel beneath the tyre, ami apparently it serves as an air chamber, a partion, of the tyre being compressed into it ea the lead comes on, compressing the imprisoned air, and increasing the cushion
ing properties of the tyre. • Most practical motorists Will welcome the invention which is described in specification No. 148,017, by the Dunlop Rubber Co. Instead of threading the inside of the usual protective tyre valve cap, it is plain bored to fit on the outside at the threads of the valve stein, and fitted with a spring catch which will engage with any one of the threads and thin retain the cap in place. Pressure of the finger or thiunib on a spring on the outside of the cap suffices either to release the Gap or to hold back the catch while it is being pushed into positioh.
The cemstruction of the Rebey steam wagon has been very °fully dealt with from time to time, and a, passing ref exence only is therefore needed to specification No. 148,025, by Bell and another, which describes the method of mounting the engine on the boiler. The cylinders are anaudited in the usual manner on a bracket, which is rieeted to the to of the boiler; but the crankshaft and gearing are all mounted on brackets which are pivoted on a bar which passes through the boiler. Expansion and contraction of the boiler as the, result of changes of temperature do not, in this ceustructien, affect the relative positions' 'of the varioue parts of the engine, owing to the pivoting of the crankshaft end of that unit.
Specification No. 148,064, by the Birmingham -Small Aims Co., Ltd., is applicable to -twin-cylinder engines of the type familiar tousers of motorcycle and aidecar 'or three-wheeled parcel carriers. It is concerned with the lubrication of the cylinders of those engines wherein there has,frequently been found to --be difficulty, inasmuch as, when the lubricationof the front cylinder has been sufficient, that of the -back cylinder has been too copious, wheaeas if the back cylinder receives only that Which it requires, the front cylinder is starved. In the construction described, the oil supply pipe is led to a point intermediate between the two cylinders, where a by-pass transfers some of the lubricant to a sump at the Bottom of the front cylinder.
A. G. Dampier-Bentiett fits a nonporous receptacle in. the bottom of the filter which is provided in the filler receptacle of a petrol tank. He claims that it will retain all the water and heavy foreign substances, which may be removed theiefrom occasionally as is necessary. (No. 148,103.)