SILENT GEAR CHANGING

Evening Post, Volume CVIII, Issue 83, 4 October 1924, Page 23

SILENT GEAR CHANGING

i Except on old cars where, owing to frame flexure, it is diifficult to bring the pinions into mesh at t.hp proper time, it ought /to- be perfectly easy to change gear without the distressing noise of grinding teeth. The essential point to bear in mind is that, when two pinions are brought into mesh, each haying a different speed of rotation, a silent gear change is almost impossible. The easiest gear, change is that of engaging first speed when.the car is at rest, yet many drivers seem unable to. do even this. The modus operandi of the bad driver is to declutch and, without pausing, to slam in the. gear ieyer, which means that one-gear pinion which is rotating is suddenly brought into mesh witli another that is idle. The proper coufte is to wait a second or two with the clutch out to bring the shaft to a standstill, when both. pinions will be at rest and' will mesh silently. In changing up, nearly every car demands a pause with the gear lever in neutral and the clutch out before moving the lever, over to the next higher position in the gate. It should be pointed out that it is the speed of the peripheries of the pinions (i.e., their teeth) which matters, as the pinions themselves may vary in diameter. On some cars the clutch stops spinning very quickly when disengagedl; therefore, the gear change has either to be effected instantaneously or the clutch shaft speeded up by the process known as double-clutching. To do this properly, one must race up the clutch shaft, which is done by placing the gear lever in the neutral position, taking the foot off the clutch and accelerating the engine by. means of the accelerator pedal. Where so many people go wrong in this process is in keeping the foot on the clutch, which, of course, merely speeds up the engine without affecting the clutch shaft. Just how muoh the engine should be speeded up is a matter of judgment. If the car is travcllling at, say, 25:.m.p.h. on top gear and it is desired to engage second speed just preparatory to taking a sharp cornor or a steep hill, obviously the engine will require very considerable speeding' up. If there is a drop from four to one on top gear to eight to one on second speed, just double the engine speed will be necessary.. If tho car is travelling very slowly—in fact, has been brought almost to a standstill—it will obviously be incorrect to race the engine. Another method of speeding up the layshaft is merely slightly to slip the clutch when accelerating. Perhaps the best summary of the advance in efficiency of the motor-cyclo since the early days of the industry may be found in the records of the first T.T. races in 1907, compared with this year's events. Therf the fastest speed attained was 38.2 m.p.h. In the 1924 races, machines of X_ h.p. exceeded this speed by 13 m.p.h., while the senior division was still another ten miles faster. The total production of crude oil in the United States for the month ending June was 59,439,000 barrels, whilo the consumption exceeded this figure by 1,651,000 barrels. The parson of a country ohuroh in South Ohio mapped out a numbor of roadß passing the homes of present and prospective members of his congregation. At the. same time he compiled a list of members who owned cars. Those carowning members wero requested to call at certain houses while on their way either .to church or Sunday school and pick up members of the congregation. Offers of lifts were made to those not in the habit of attending churoh, a promise being mado to bring them back after tho service: This progressiva clergyman has since had the pleasure of always preaching to a crowded attendnce. When the motor-cycle engine is revolving at high-speed at, say, 3000 revolutions per minute, each piston starts and stops 100 times a second. Each of the valves opens and . closes 1500 times a minute, or more than 20 times a second. The periphery of the flywheels travels at the rate of 125 ft a second; the piston moves -up and down in one-three-thousandth part of a minute, and the exhaust and intake valves' periods are at the same rate. A detailed cable message has been received locally to the effect that Austin 7-h.p. cars took first and Becond place in the 750 c.c. class Junior Car Club 200-mile race at Brooklands on 20th September. Gordon (England) made the first non-stop run for the second year in succession. ' Do not neglect the tire valves; they are small things, and, ordinarily, need little attention. Still, they are important; the rubber portion, ensuring an airtight seal, may be cut or more or less perished, and requires renewing. Always keep the dust caps screwed on. To use a tire with a valve that has developed a minute leak may be its ruin. The tube may be nipped, or the tiro may creep and tear out the valve, and the walls of the cover be irreparably damaged. The world's production of motor and motor-cycle tire covers is estimated to now he 52,520,000. The United States, which has 80 per cent.' of • the world's motorists within its borders, produced about 46,000,000 of the above total. A headache when driving a car is not at all an infrequent experience. Tlie causes are numerous, but an often unsuspected one is a very small leakage from the exhaust pipe, which finds iCa way into the driving compartment. Carbon-monoxide gas, which is given off by hiuompleta combustion, ..is a very insidious poison, for its presence cannot always us detect-

Ed by smell, although in the case of a rich mixture the odour of the unburnt fuel may be noticed. A slightly hissing or spitting sound is generally an indication of a leaky joint, which should be remedied at once. If this causa is suspected, ventilate the driving compartment by opening one door slightly and raising the upper panel of the windscreen, wh6n, if the symptoms of headache rapidly pass off, one can be certain that the reason has been found.

Headaches are frequently produced by eye strain, especially in brilliant sunshine! and by the nervous tension of driving long distances or in traffic. A tightly fitting hat will almost certainly produce a headache, and so also will tight clothing, especially round the neck, owing to the pressure on the bloodvessels leading to and from the brain.

A multitude of different types of power-driven vehicles have been developed in recent years, each type filling its place more or less efficiently according to the requirements which naturally change as. the years pass by. The motorcycle is one of the successful types, and is developing satisfactorily. As a means of combining sport and pleasure the motor-cycle, because-' of' the speed of ■which it is capable, and its low operating costs, is attracting an ever-widening field, and for general utility and as a means of travel the economy of the motor-cycle and sidecar, is . proverbial. The combination machine can transport with ease three adults, covering from 40 to 45 miles to.the gallon of fuel.