Motor Notes

Wanganui Chronicle, Volume LXXXI, Issue 18900, 22 December 1923, Page 9

Motor Notes

EXAMINATION OF TYRES

INDICATIONS OF FUTURE SERVICE. Not only during the warm months is the average passenger car driven at least twice as far daily as in the winter season, but it usually is driven very much faster. For these reasons tyres are subjected to much more severe service, and troubles with them come very much closer together, in point of time, during this period of heavy driving, which calls for a cartful inspection and revision of the equipment before long-distance trips and vacations tours are to be made. In considering the stock of tyres on hand, the mileage already delivered by each and its age form the best guides as to what future service may be expected of it. Knowing how far a certain tyre has run and subtracting this distance from the average mileage obtained from similar tyres on the same car, gives the most dependable guess as to its “expectancy”—to borrow a term from the life insurance man. A useful check upon any such estimate is obtainable from its appearance and an expert

tyre man, if he has a casing off, so that thorough examination is possible, may make some quite accurate predictions, but much less can be learned from inspecting a casing on the wheel. INSPECTION OF THE THREADS. J If the tfe end has cuts fully through it, which /avc been lung neglected, and have begun to raise sand blisters; if there are any swellings in the surface or my indications of approaching failure along the side walls, no great dependance for future service should be placed in it, but if the tread is practically perfect, bearing normal wear, and no signs of weakness are apparent, the casing can be relied upon fur the additional mileage indicated by service previously rendered and past experience. The- chief reason for estimating the expected mileag' that remains in the casings on tuc wheels is iu order to provide requisite spare tyre equipment, it going without saying that the extra casings carried must be more numerous and of better quality if the tyres in service are old and worn than as if they are all new. OVERHEATED ENGINES USUALLY RESULT OF BAD WATER CIRCULATION. An engine is not overheated unless the water in its jackets reaches practically boiling temperature. On the contrary, it is usually at its highest fuel efficiency just before boiling temperature is attained, but if steam is freely formed and remains in the jacket spaces over-heating occurs, as it prevents contact of the water with the hot metal, thus stopping their cool ing and allowing them to reach abnormally high temperatures. Small areas, especially round the exhaust valves, may even become red hot, causing premature ignition of the fuel charges, severe knocking, and reduction of powers. The oil on pistons and cylinder walls may become so hot and thin as to cause serious friction, and the charges entering the hot cylinders are pre-expanded, with q noticeable diminution in the power developed. When the oil on the outside of the engine smokes, and when it continues to fire charges, after ignition is switched off, one may be sure it is i over-heated. This condition is almost infallibly due to one cause—failure oi thq cooling water to circulate through the jackets, at least at the normal rate. .STAGNANT WATER CAUSES HEATINSULATING STEAM. If there is plenty of water in the system as a whole and the engine thus overheats, while the water in the radiator, especially towards the bottom of it, is not more than warm, or at least is not up to the boiling point, lack of circulation is almost certainly the trouble. In other words, the water in the jackets is practically stagnant, and has time to be converted into heat-in-sulating steam. Under such circumstances the question is: “What is preventing the circulation of water*?” The rubber connections are the most likely cause, as they deteriorate rapidly with use, and it is well to pull them right off and replace them if their inner surfaces are broken so as to form obstructive flaps, or if they are soft and flabby. Jacket passages seldom fill up with rust, but it is well to send a hose stream through them to clean out what deposit has formed. On some engines compressible gaskets are used between water and outfiet flanged connections, and sometimes these squeeze into the passages and obstruct them. An inspection of such connections is well worth while. In forced cooling systems the impeller of the waterpump may be found to have become loose on its shaft, and thus fail to create a circulation. It should be tested to see that it will throw a full, forceful stream. Hose water should also be run into the radiator filler opening, and, if it does not come out the bottom connection with full freedom out is obviously necessary.

MAGNETO TROUBLE

HOW TO PUT IT RIGHT. Why are so many motorists afraid of the magneto? Some drivers will cheerfully commence to readjust tappet clearances, but avoid magneto adjustment like the plague. Yet all the magneto adjustment that can be tackled successfully ui the roadside is well within the compass of the average owner-driver if he or she will only try. An experienced motorist can usually

tell whether his misfiring trouble is due to carburettor or magneto. Refusal to start at all, in otherwise normal circumstances, generally points to the magneto unless the petrol is not turned on. DIAGONISING THE TROUBLE. Assume that we are in trouble with ignition failure then. First, a preliminary external glance at the plugs. Arc all the wires attached? If they are, don’t worry about the plugs for the moment. They won’t fail unanimously at the same time. Has the wire come off the switch lead terminal of the magneto, or is it so loose that the connection may be faulty? Or is it shorting to the frame somewhere, thus switching you off? Assuming that these points are all in order, you can then put on your roost self-assured manner and tell the spectators that “the contact bieaker is stuck.” You are almost sure to be right. This little difficulty crops up every now and then, even in the “ boe-t regulated magnetos,” and it is more likely to happen when you are near the seaside and in other damp atmospheres. THE CONTACT BREAKER. Underneath the terminals on the enu of the magneto to which the plug wires

are attached you will see a circular cap held or by a spring clip. Turn the spring aside, pull the cap off, and you will see the contact breaker. Now get the magneto spanner out of your tool kit. You wil] find that its fits a small nut right in the front and centre of the contact breaker. Undo this nut. After a few turns with the spanner it will come out with finger pressure, and you will see that it is a long pin. II screws into the end of the the armature but you need not worry about that. Put it somewhere it cannot get lost. With your finger and thumb now pull the contact breaker itself out. It generally comes away readily enough, but if it does not, rock it a little whilst pulling, Many motorists

are afraid to remove the contact breaker, thinking that it has to be “timed” when replaced. Have no fear. You cannot replace it wrongly. There is only one position in which it wilt go back properly, and that is the right petition. On the buck of the contact breaker yon will see a small circular piece of carbon attached by a light spring. Be careful not to break the latter.

You will now probably find that the I rocker arm is stiff on its fibre bush, and that the platinum points are either permanently together, or apart, unless I considerable pressure is exerted in the rocker arm. The small flat spring attached to the rocker arm should be sufficient to cause a return movement ; when you move the rocker the j other way with your finger. If this stiffness obtains, remove the rocker

from the bush and gently reamer out the bush. You can do this with the pin which you previously removed from the centre of the contact breaker. The bush is made of fibre, which is the reason why damp atmosphere is more likely to cause trouble. Never oil this fibre bush. Now see that the platinum contact points are clean and flat, and replace the parts, and the trouble will have vanished.