Motors and Motoring
Simpler Gear-Changing
MANY designers in their efforts to popularize Motoring, and. kai gain a wider field for their markets, are paying heed to simplification of gear-changing. This aim is in the right direction and improvement is clearly long overdue. I have previously dealt fully with the ordinary gear-box, the chief principles of which have remained very similar for the last thirty years, and shown the reasons why gear-changing calls for a certain amount of skill and practice initially. Free- wheeling devices, which greatly assist gear-changing and tend t4 more economical car maintenance, have also been referred to. These devices are additional accessories inasmuch as they Can be used with the orthodOx type of gear-box. There are, too, a few new kinds of box in which the constructors hake aimed at getting better all-round results, and it is proposed here to refer briefly and as untechnically as possible to Rye examples.
One of British design which has been on the market for some little time- now, is the gear-box used on the 9_ h.p. Riley, and which is incorporated in the new 14 h.p. six-cylinder. In this:instance, the change is more a modifica- tion than a radical alteration. The objects are to simplify the third speed change where four forward gears are used and to give a degree of quietness on third similar to that obtained
on to The gear-wheels are of nickel chrome steel- on large diaineter seven-spline shafts, ground and hardened. The shafts run on oversize - bearings. In addition to the usual direct drive top gear the third speed wheels are in constant nirsh,and have helical teeth. The engagement for third is by dbg connexion. Gear-changing is effected in the ordinary way.
An American gear-box, which has somewhat similar intent, is that used on the medium and larger size models of Graham- Paige. It forms one of the very rare cases of a trans-Atlantie machine having four forward gears. The speeds are changed io orthodox fashion by a central flexible lever- which has a catch for first or emergency gear. Reverse is opposite second, and third is opposed to top. Third and top speeds are self- contained and consist of two outer members . which' have internal teeth.- The outer member of the forward gear is connected with the gear-wheel inside the after sleeve, and these are coupled to the -propellor shaft. Engagement of either of these gears, which are top and third, is by sliding a splined sleeve which passes inside the inner gear-wheels. If this splined sleeve is slid forward by the selector rod the after constant mesh gear is brought into play ; while if it is slid backwards the • forward one -is connected with the drive, the back one being free. With a relatively large six-cylinder engine, such as the American always uses, and these ' twin- top gears—as- they are known—it is possible to employ a high ratio for fourth or top gear. For example, on the 23.4 h.p. Graham-Paige top is 3.9, while third is 5.9 to one. The arningenient gives in effect a geared:up top, so that the highest speeds may be run with less noise, vibration, and unpleasant- ness, and at lower cost, since clearly for a given vehicle speed the engine will be doing fewer revolutions. This last advantage must not only result in saving of petrol and oil but also in reduced wear of the bearing surfaces. On the other hand, a really useful third gear for rapid acceleration and climbing can be used, while here again the substantial asset of equal quiet- ness on third in comparison with top is obtained. Especially is this of value in these days of long journeys.
A notable production, which is a revival in modified form, is the half-automatic gear-box which can be had as an extra on the 30 and 20 'h.p. Arnistrong-Siddeley chassis. The idea is to simplify gear-changing and to reduce noise, while by les- sening the time normally taken to effect a change it gives speedier acceleration. A hand and a foot control are used for this gear, but instead of the usual long lever to one side of the driver the selection is made by moving a small lever working in a marked dial on the top of the steering wheel. Selecting gear does not make the change, and hi this way the driver has the advantage that he can choose his ratio in advance and not necessarily have to wait-till the actual time of change. The change itself is effected by the full depression and release of a pedal which replaces the ordinary clutch pedal. When this pedal is partly depressed a customary clutch action la obtain- able.
An example of a designer trying to give increased efficiency by use of special gearing is the French Voisin car. For instance, on the 16/50 h.p. six-cylinder chassis there is -a - compound May which gives.avhigh and 1:;*- rear axIe ratio. Thus, the ratios are duplicated and with the three forward:gears in the gear-box six forward ratios are available. The change of final ratio merely calls for the turning of a small finger-and- thurnb lever on the instrurnent board. Ari ingenious part of the system is that the ordinary vacuum servo motor used for the four-wheel: is employed -to make the change • just referred to. The piston in the vacuum cylinder, which is neatly assembled neat' the- torque tube; provides a rotaity, ' motion by Which the high or low ratio is engaged. The pinions' or wheels are of good width and are chamfered off to give easy engagement, while the cushioned effect of the suction piston lessens the possibility of grate. The high and low back axle
• ratios can be changed while the car is in motion. With the ' arrangement the former five to one back axle ratio has been replaced on this 16/50 chassis by 4.6 and 0:7 to one ratios. The high gear allows the car to travel at speed on the open road ' with the motor turning well below its maximum, which ..is over 4,000 revolutions a minute. For instance, the car ddes 72 miles an hour at 3,500 r.p.m. of the engine. The low ratio is of use for stiff climbing and for rapid acceleration in traffic, while it saves gear changing in the ordinary way. The -range of the six forward ratios is from 4.6 to 21.3 to one. The car is started in low second, and as soon as it is moving the gear lever can be pulled back into low top. When some way has been gained a touch of the control, together with the de- pression of the clutch pedal, immediately brings the -high ratio into use. If the car is brought to a crawl another turn of the lever, in a reverse direction, brings the low top into "action, when the car will accelerate, and thereafter high top can be engaged.- - • --
The last illustration to be given-is the new design employed on the American pridiictions of General Motors, known as the Cadillac and - its' smaller sister the Lii Salle. On both' these 90-degree Vee 8-cylinder engined chassis what is known as the Synchrcialesh silent gear-change is employed; It is claimed that with it -any driver, in -any Circumstances, can change gear easily', quickly, and without jerk. Clutches are used in combination with the gear-wheels; and before engage- ment of the gearg-is made a clutch is connected which speeds up the wheel to be meshed • or decreases the rate as required. When engagement has been made, -the- clutch- is released. • Anyone who has read the two previous articles on the gear- box will appreciate what this means. The Synchro-Mesh gear-change effects all changes up—fiamely, first to second, and second to top=these cars have three-Speed boxes--while it also assists the driver to change froth-top:into second. It is claimed that by the special mechaniiiin- changes are inde- pendent of the viscosity-of the oil. -It is significant and a sign of the times- that this gear:licnr;_upon which I understand experiments extending over two years have been expended, should be incorporated as standard on cars which clearly are mainly one- or top-speed machines. It is right, too, that British designers, who specialize in the high efficiency chassis, with an economically small engine and four-gear ratios, should note this effort on the part of this vast American motor- producing corporation.
YOUR MOTORING CORRESPONDENT.
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