MOTORING WORLD

Manawatu Standard, Volume LVI, Issue 313, 5 December 1936, Page 7

MOTORING WORLD

ENSURING GEAR SILENCE. Ten years ago silent gears for inintermediate speeds were practically unknown. Certainly they were not available for popular makes of cars, nor was their universal use at that time generally anticipated. To-day the public accepts them as a matter of course. To ensure silence, every gear wheel fitted in a Morris gearboz undergoes several tests throughout its stages of manufacture. Before the teeth are cut, the gear blanks are tested for running true to within one-thousandth of an inch. When Cutting has taken place, Ihe profile of the teeth is checked, and must be within a tolerance of onethousandth of an inch before being passed to the hardening shop. After hardening, the gear teeth are lapped in special machines with an abrasivu paste, to give a highly finished surface and to remove any small inequalities caused by distortion in the hardening process. Before the gears are assembled into the gearboz, they trie tested in individual pairs for quiet running, and after assembly the complete gearboz is tested to ensure quietness of the unit as a whole.

CAUSE OF TYPE NOISE. Most motorists arc familiar with the objectionable noise which arises from some types of tyre treads, and which spoils; the pleasure of handling an otherwise quiet car. The problem oT eliminating this noise is one which has worried tyre manufacturers for some time, and different tread patterns have been produced with varying degrees of success. The pattern of the tread of a new tyro just produced in America consists of a number of circumferential grooves which are fairly deep. About half-way down each groove, a rib is formed in the rubber, and under compression this has the effect of driving out any grit and mud which otherwise might collect in the annular space. Across the tyro tread are cut a series of very fine knift-edge slits, so fin© indeed that at first sight they look simply like marks across the rubber. These slits are not equally spaced all round, the arrangement being such that different periods are 6et up as the tyre revolves and, consequently, no pitched wdiine can arise from the cover. THE TYRE PROBLEM. In purchasing a new car, many motorists are uncertain whether to Specify four-ply or six-ply tyres. The Six-ply tyres are manifestly the tougher of the two, and if the car is to be used considerably on side tracks involving the risk of rubbing the tyro walls against stumps and sharp stones, the six-ply tyres- should be specified. On the other hand, it is generally agreed that four-ply tyres, because of their greater flexibility, have much better riding qualities, so that if the motorist proposes to keep to the main highways, he will be just ns well off with them, and also will save money. With good care, there is no difference in the mileage obtainable from the two types.

NIGHT PARKING. MOTORISTS’ MISTAKES. “There still seem to be many motorists with the mistaken idea that at night time they can leave their cars anywhere without the necessity of having the vehicle lighted,” says the latest safety-first message of the Canterbury Automobile Association. “At one time it was not lawful to leave a motor vehicle anywhere on a public street without having the lights on, but, through the advocacy of automobile associations, provision was made so that motor vehicles could be left unlighted within 20 feet of a street light. Observation shows that the rule is far from strictly observed, and that some motorists are markedly careless. “The rule compelling motorists to keep their vehicles lighted when parked at night away from street lights is a good one and 'is designed in the interest of road-using safety. The dangers presented by an unlighted vehicle standing in a roadway cannot be too strictly emphasised, particularly in districts where fogs may bo met with from time to time. Almost equal danger is created by the unlighted vehicle if the weather is wet or murky. “It will be obvious that an effective tail-light is an absolute necessity. The lamps of bicycles are not very brilliant and unless the red-tail lamp of a parked car is readily visible the cyclist who observes the law and keeps strictly to the left runs the risk of collision.

“Always obey the lighting regulations,” the message concludes, “not only when the car is in motion, but when it is parked.”