MOTORDOM

Greymouth Evening Star, 16 November 1934, Page 4

MOTORDOM

NEWS OF THE ROAD

(By

“Gearbox”)

EXTRA TOP GEAR INTERESTING NEW DEVICE One of the leading makes of cars in the United States has been fitted with a gear of higher ratio than the usual direct top gear. The additional gear can be ,used in favourable circunv stances to maintain a fast road speed without “revving” the engine too highly Indirect top gears have been used in the past, but the interesting part of this new device is that it is automatic, the details of which are as follow: — Within the gearbox, between the end of the driven shaft and the head of the propeller shaft, is a separate small planetary gear which is normally solid, and, therefore, on top gear transmits the drive unaltered to the back axle. But the planetary gear can be brought into operation by locking what amounts to a brake drum, which is done by heavy internal pawls, the points of which engage with slots inside the drum. Under the action of centrifugal force when the driven shaft reaches a certain speed the pawls will fly out, engage the drum, and by locking it bring the gears of the planetary set into play. This being done, the drive from the gearbox is stepped up, the planetary gears giving the equivalent of a much higher top. The pawls are set to act at about 40 m.p.h., at which speed the indirect top comes into action, to be disengaged only when the accelerator pedal is released, so taking the pressure off the pawls which will then fall out of engagement if the car’s speed is lower than 40 m.p.h. The advantages of this device'with a three-speed gearbox allow a comparatively low-ration normal top gear for town work, together with a high-speed top gear when the car is taken for a tour. HYDRAULIC BRAKES With the increasing average speeds of the modern car it has become essential in the interests of safety that brakes should be maintained at their highest peak of efficiency. Although hydraulic brakes have been used for many years now, they remain a mystery to many owner-drivers. The following information is intended to warn such drivers of the first essentials of maintenance and to indicate reasons for defects which may develop after some years of running. The most important point in the maintenance programme is to keep the reservoir properly “topped up.” This is best left to the expert at the garage or service station, who should also eliminate air from the oil lines and examine them for leaks. The detection of leaks, by the way. is simplified by chassis cleanliness; in fact, the dismantling of mud-caked pipe unions renders the exclusion of dirt from the system almost impossible. Unsuitable fluid should never be used on the grounds of economy. Mineral oil, if purposely or accidentally admitted to the system, may cause serious trouble by swelling the rubber valves and cups to such an extent that they become plastic and non-resistant. If it is known that mineral oil is in the system, the only effective way of removing it is to drain the lines, reservoirs, and cylinders, and wash throughout with methylated spirit. If the rubber parts have not been harmed they can then be refitted, but all parts must be thoroughly dried before assembly, otherwise rust may form on metal work. When reassembling the piston should be primed by dipping rnto brake fluid.

Prolonged use may also result in a gradual deterioration of the rubber parts, and such wear usually results in a gradual loss of efficiency. The piston of the Toaster cylinder may also need replacement after considerable mileage. When installing a new master piston or making adjustments to the plunger rod. care should be taken to ensure correct operation of the piston. The amount of its travel must be accurately set if the piston is to uncover the recuperating hole in the cylinder; failure to do so is often the cause of brakes not releasing properly. Grabbing brakes may, of course, be caused by broken retraction springs, and this possibility should not be overlooked when one hub is affected more than the others. The need of brake shoe adjustment to compensate for lining wear is usually indicated by excessive waste motion of the brake pedal. The means of adjustment, usually an external screw operating an internal cam, controls the amount of clearance between the drum and the linings. As this clearance is small, the movement of the brake shoes on the fulcrum pins is correspondingly small, and seizure at this point should be guarded against by the use of graphite or other suitable lubricant.

Leakage of fluid may cause uneven brake balance. The detection of this fault is comparatively easy, as the need for new fluid-retaining washers is usually fairly obvious. A badly scored drum or stiff brake shoe cams or pins can also cause unequal balance, while different types of brake linings may be a niore obscure cause. When Relining hydraulic brake shoes it is essential that the linings be all of the same material and that the fitting is securely and neatly done. Gaping linings are not conducive to smooth action. While if the linings work loose on the rivets fierce action may easily develop. Loose brake shoe fulcrums and pins can also produce a certain amount of grabbing, and the tendency is for - the trouble to get worse until checked. Occasionally when shoes are relined lining of too 'high a frictional capacity is used, resulting in a very fierce action. The only remedy is to decrease the braking efficiency by tapering off the ends of the lining or to rub a little French chalk or graphite into it. Misalignment of the axles and chassis distortion may be ruled out when diagnosing hydraulic brake faults, as the flexible pipes or fluid lines can be bent in any form without adverse effect on the brakes.

WOMEN DRIVERS “TOO LAW-ABIDING.” Screeching brakes, tooting horns, the traffic comes to a standstill, and every male in the vicinity remarks complacently, “Sure to be a woman driver.” Will we never convince mankind that we can drive just as well as they can? This is the plaint of a woman driver, who is also an authoress of some note.

What of the speed fiends who go rushing along the roads with whining superchargers and noisy exhausts? Invariably a man is at the wheel. Men are admittedly more mechanically minded than women, and usually have their car in more perfect control. But they refuse to realise that if through their risky driving a woman is forced into a difficult position and perhaps does the wrong thing, they alone are to blame.

To women, cars, even the “baby” variety, are rather alarming monsters until their little ways are perfectly mastered. Grinding gears are most humiliating, and one is sorely tempted to reduce “changing” to a minimum. Be firm with yourself and retire to a quiet road and practise until you can change into any gear automatically and at a moment’s notice. Sometimes it is just as necessary to accelerate and rush out of the danger zone as it is to put on your brakes before you get there. If you always change down before you come to a bad turning or crossroads, you will be prepared for all emergencies and can approach them with the confident feeling that you will never get flustered and stop your engine in front of oncoming traffic. The rule of the road is to keep to the left, but we are so law-abiding that we sometimes carry this to extremes. You constantly see a car approaching a corner and hugging the left-hand kerb. It turns to the left, and what happens? To round the corner it has to swing out into the middle of the side road and run the risk of meeting another car, also in the middle of the road. By drawing out slightly before the turning is reached, it is easy to finish close to the left-hand side.

Our law-abiding instincts also assert themselves when turning to the right. The car again hugs the left side, slows down, and then shoots across. You must edge to the middle of the road, so that the traffic behind you can pass to your left without having to slow down and wait until you have crossed. £2O CAR IN EUROPE. New cars never may be as cheap as bicycles, but according to overseas advices prices are getting remarkably low. An English car that will sell in that country at under £lOO will be on the market before the end of the year. Germany is manufacturing cars which are sold for about £5O, and a car is being' manufactured at present in Czecho-Slovakia which will be'sold for about £2O. The Czecho-Slovakiau car, which is fitted with a twin-cylinder two-stroke engine, has been referred to as “a European reply to the £5O cars made in Japan.”

DIAGNOSING BREAKDOWNS. It is always handy for the ownerdriver to be able to diagnose the cause of an engine breakdown, particularly if one should occur many miles from a garage, and it should be necessary to send for a replacement part. Following are some of the major causes of breakdown and their symptoms:— The sudden fracture of a connecting rod is usually indicated by a loud crack, following by misfiring of the cylinder affected, and frequently the rattling of the broken rod can be distinctly heard. This may be caused through running an engine with a loose big-end. Broken pistons usually make a noise resembling acute piston slap, but the noise depends on the position and extent of the fracture. Complete misfiring and absence of compression may indicate the complete severing of the top of the piston from the skirt, and the piston affected can be'located through the spark- plug hole in the cylinder head. Rotate the engine by the crank, and the detached piston top will be found to remain stationary. Broken crankshafts, though fortunately rare, usually occur through a fault in the metal, crystallisation, or undue stresses caused by excessive vibration or labouring of the engine. Such a breakage usually causes a loud, irregular knock, and considerable vibration. A quick test can be made by locking the flywheel and endeavouring to turn the engine by the crank or hold the crank in position and try to turn the flywheel.

SPRINGING ADJUSTMENT. Many motorists do not realise the importance of maintaining the suspension systems of theii’ cars in their most efficient state, and the fact that correct adjustment of road springs and shock aborbers makes for longer life of the car is often overlooked. It is fairly obvious that correct setting of the shock absorbers increases riding, comfort, but that it enhances the possible speed and safety of the car is not so evident. In cornering, if the shock absorbers are too tightly set, the springs do not “give” sufficiently, and the car, therefore tends to overturn when centrifugal force conies into play. If the shock absorbers are set too loosely the car is inclined to “heel over.” With a correct setting of the shock absorbers, there would be no tendency for the- car to overturn, or to sway over to an uncomfortable angle.

It is not only in cornering that right tension of the suspension system is important, for it matters quite as much when following a straight path. If the suspension is too “soft” the car takes on a wavy motion every time a slight bump is negotiated, while anything other than very slow driving on rough roads produces an unpleasant bouncing of the car. On the other hand, if the springs are too hard, driving is distinctly unpleasant at low speeds, since every irregularity in the road surface is transmitted directly to the chassis.