High Road and By-Road

Waikato Times, Volume 106, Issue 17804, 31 August 1929, Page 23 (Supplement)

High Road and By-Road

CHOOSING SPARKING PLUGS. Owing to the general increase in compression pressure in present, day cars, it is more and more important to choose sparking plugs of exactly the right type. That this is so is shown by the action of the majority of the reputable sparking plug makers in issuing charts which give recommendations for all the different cars on the market. The motor owner is counselled to follow these charts religiously, for even (hough . the thread of a plug may be right, it does not necessarily follow that it will function satisfactorily. Many drivers are under the impression that it is only in the matter of thread and reach that plugs differ, but in addition, they vary in regard to their capacity for resisting heat and that is the point which the makers have to consider most seriously in drawing up their charts and consequently that is why it is wise to adhere to the recommendations made in these charts. A sparking plug, to function properly, must operate at a certain heat. If it is cold oil will collect on the points and cause misfiring; if it is too hot the points will become incandescent and cause pre-ignition. An engine that operates at a fairly lowtemperature, and there are still a number of slow' running, low compression power units of this type, will require a “ hot ” plug, that is, one which because of its high resistance of heat, will store it up. On the other hand, a high compression, high speed unit which operates at a fairly high temperature will need a " cold ’’ plugthrough which the heat passes rapidly and is dissipated through the cylinder casing. It can be seen then that a great deal of experimenting and careful thought lies behind the sparking plug charts and the advice which they contain should be adhered to.

A COLUMN FOR MOTORISTS.

ILLUMINATING THE TANK GAUGE. One advantage of the instrument board type of petrol gauge is that it can be read at night. However, in many cases it is possible to make Die type of gauge that is fitted directly to the tank just as visible, but it is essential that the tail lamp is located closely adjacent to it. All that one has to do is to drill a small hole in a suitable position in the shell of the tail lamp so that a fine ray of light is directed on to the gauge. This eliminates the darker which exists when a match is lighted to take a reading.

CARE OF BENDIX DRIVE. Do not forget that the Bendix drive gear of the starting motor must be kept scrupulously clean if it is to operate satisfactorily, bat in modern cars that is often a difficult matter as the Bendix usually is enclosed within the clutch bell housing. The usual method of cleaning a Bendix drive enclosed in this way is to remove the starter motor, but this trouble can be avoided by drilling and tapping a hole in the housing so that the spout of an oil can filled with petrol can be inserted and the petrol squirted over the Bendix shaft. No not use kerosene for this purpose as this is sufficiently gummy to collect a certain amount of dust. The Bendix gear is the one part of the car which should never under any circumstances lie lubricated.

CHECKING BEARING CONDITION. A plumber’s force cup is the only tool that is necessary to find out whether any looseness exists in the

connecting rod big end or gudgeon pin bearing when once the cylinder head is removed. The test about to be described is worth carrying out every time the valves are being ground in Bring the piston attached to the connecting rod to be tested to top dead centre and then press the force cup against its top until it adheres to it. Then attempt to move the piston up and down with force cup. If it is possible to move the piston ir. tills way it is obvious that looseness exists in one of the two connecting rod bearings.

COASTING. Nothing can be more delightful than to coast down a long easy grade, but it is a practice which should never be indulged in by depressing the clutch pedal and holding it there with the gears still engaged. This is a matter that has been dealt with before, but the frequency with which the writer still sees the offence committed warrants another diatribe against it. The clutch withdrawal mechanism only comes into action when the pedal is depressed and it only designed to operate a few min-' utes at a lime at the most. To design it otherwise would involve a very expensive construction indeed. It can be seen, then, that to coast with the clutch disengaged is going to put a big | strain on this mechanism and the reJ suit will be rapid wear eventuating in ! that horrible, loose jingle, which is i so frequently heard coming out from ; the clutch pit. It may be argued that to coast with the clutch out and the gears still engaged is a much safer way than to slip the gear lever into neutral and re-engage the clutch and so it is, but the answer to this is that as coasting is entirely unnecessary one should never do it unless conditions are so safe that the latter method is warranted. While on the subject of clutch withdrawal mechanism it might be mentioned that its frequent lubrication. is extremely necessary. r Phe majority of modern clutch withdrawals are fitted with a grease gun nipple projecting through the clutch cover, and this should receive its share of lubricant at least once a fortnight and preferably once a week.