Be Your Own Mechanic

Sun (Auckland), Volume II, Issue 540, 18 December 1928, Page 6

Be Your Own Mechanic

Hints for This Year’s New Drivers

MOTOR-TRADERS report that 'an exceptionally large number of people bought their first car for this summer season. These inexperienced drivers will know little about the accuracy or perfection of their motor’s mechanism, and to assist them in foretelling and locating possible engine trouble,, tire following brief suggestions are published.

A few lessons from the agent or driving school will enable him to drive —in a fashion —but he should not be satisfied with the knowledge that, after pressing the starter button, pushing out the clutch, and engaging gear, the car will move off and can be directed at will.

used to its particular sound when in good repair. After this has been mastered, it becomes a simple matter for anyone to detect undue wear by using a modified stethescope. Cut a piece of wood about a foot long and half an inch in section. Next take an old handkerchief, make a pad about four inches square, and tie it firmly over one end. Now, if you start up the engine, place one end of the rod to any portion of the engine and press the ear firmly on the cotton pad. You will be able to hear, unmistakably, whether any particular unit you select is functioning normally. Bearing knocks, piston slap, sticking valves, and all such troubles can be isolated and identified with the greatest of ease, and with a little practice any departure from normal running can be detected long before any serious results will accrue. When piston rings begin to wear and the motor loses power, the “hiss” of gas may be heard with the stetliescope, but to make doubly sure it is advisable to “listen in” at the crankcase breather or oil-filling apperture. LOST COMPRESSION The best way to carry out this test is to have someone turn the starting handle very slowly while you listen for the “hiss” that spells “lost compression.” It can only be due to one of two reasons—badly seating valv • or worn piston rings. In either ca. e it is a paying proposition to have the work done as soon as possible. It must be evident then, that if the owner-driver chooses to train his ear to act the part of detective instead of waiting until something drastic happens, his motoring life will be happier, and what is more to the point, his maintenance charges must be considerably reduced.

New drivers, who are content to leave their kowledge at this point lose pefhaps one of the greatest charms in driving—being conversant with the various units and the part they play in the cycle of operations.

Further, in the event of any trouble or derangement, they are hopelessly stranded, and must perforce seek outside help—if available. One of the first things a driver should do is to accustom his ear to all the “noises” of his car.

Every individual machine has its own characteristic “hum” when in motion, and a good driver can so train his ear to play the part of detective that the slightest variation from normal running can be detected long before the most sensitive instrument can record it. And locating any trouble a.t its inception means long life, good service, and small repair bills. If it were suggested that your lawnmower received more detailed attention in proportion to its value than did your car, the impeachment would be strenuously denied. But unfortunately, while the exterior receives generous treatment—“out of sight out of mind” seems to be the general idea with regard to the motor and transmission. WHAT THE EAR CAN DO Five-sixths of the troubles a car is heir to can be detected by ear and if the driver would school himself into learning the significance of eve.ry sound a major breakdown would be a remote possibility. Firstly, take the engine proper.

Every motor at any definite speed has its own characteristic “beat,” and once this is learned detection of ; trouble is a simple matter. Popping j back in the carburettor spells sticking valves which, if unattended, will lowei* the efficiency of the motor, increase petrol consumption, and may ; cause fire. Missing plugs can be identified by L the uneven beat of the engine, and the L cost of a new plug can be saved in ; benzine alone during a day or two's running. Old types of cars—especially the : pre-war vintage, were notorious “howlers” in the transmission. Such progress has been made of late years in the science of gearcutting that the modern car—particularly in top gear, - should be practically silent. Consequently, when the driver defects an unusual “hum” in the back axle assembly, he may be sure the c,rown wheel and pinion are not correctly meshed. Should this “hum” persist or increase in intensity, make for the service station without delay, and have tlie adjustment checked up. The job will only cost a few shillings and may in all probability ayoid an expensive repair and a good deal of inconvenience at no distant date. Gear box noises may be similarly detected. A SIGNIFICANT SOUND Normally, top gear should be perfectly quiet, and indirect gea.rs merely* emit a “whine” of meshing teeth. Any increase in noise, especially if coupled with a peculiar harshness —spells worn gearshaft races, allowing the shafts to run out of true. Here, again, renewals will be only, a tithe of the potential cost of repairing a wrecked gearbox. Now, let us see how the ear aids us in detecting trouble in the engine. First of all, we must remember that there is no such thing as a silent engine. Noise is there in every type, but it is merely a matter of degree, depending to a great extent on design and efficiency. * Naturally, a small high-efficiency motor as used in racing cars will be mare noisy l mechanically than the engine of the conventional touring car. This is due to the fact that racing design employs steep cams with high and quick lift for the valves and the springs actuating this mechanism must of necessity be very strong. Consequently it is only to be expected that this valve gear would give off a good deal of mechanical noise. AN AUTOMOTIVE STETHESCOPE j Whatever type of motor may be under review, the driver will soon become