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Press, Volume LXXI, Issue 21411, 1 March 1935, Page 8

"Roadster" Invites articles and paragraphs of interest to motorists for this page. NOTES A number of trying and hard-to-trace troubles can be brought home to the practice of using mixed sparking plugs. Drivers in emergency obtain unsuitable plugs from garages, and in some engines plugs of various types and sizes will be found in use. These should be. changed at tne earliest opportunity to the plugs recommended by the vehicle manufacturers. It is mistaken economy not to do so One of the trouble plugs of varying length cause is a variation in compression. They may have also a tendency towards pre-ignition. When it is noticed that patches of oil form on the garage floor the motorist should take steps immediately to remove the oil and to ascertain the cause of its appearance. Oil and grease are arch enemies of rubber, and if allowed to come into prolonged contact with the tyre will tend to rot and undermine the tread. If it is not at once apparent from which part of the vehicle the oil is leaking, a good plan is to spread sheets of newspaper on the floor before parking the car for the night, and next day to examine the result and note what part of the mechanism is immediately above the spot on to which lubricant has leaked. Often a little judicious tightening of bolts will effect a cure, but in all circumstances it b desirable to find out what is the cause of the dripping and to bear m mind that the gradual loss of lubricant might become much more serious under running conditions on the road.

Corrosion of battery terminal thimbles and the surrounding exposed copper cable is due to the creeping of the acid solution from the cells, and in a minor degree probably to fumes. The effect is that not only is the metal gradually eaten away, but the products cf corrosion set up a very high electrical resistance between the lug of the battery and the connector. When it is desired to remedy that condition it is necessary to remove all traces of corrosion before protecting the terminal with any acid-resisting compound. An easy method is to plunge the end of the cable and its connector into a boiling solution of water and cloudy ammonia. That will neutralise all the deposits, and the parts can'then be rinsed in hot water, cleaned with a tile or emery paper, and the connector replaced on the terminal lug of the battery, which should also be scraped clean beforehand. Finally, after the connector has been screwed tightly into place the part can be coated with vaseline, or an acid-proof compound such as sealing wax dissolved in • methylated spirit. The introduction of wireless on cars has resulted in a demand for increased output from dynamos. To meet this a new type of internally ventilated dynamo has been introduced in England by one of the best known factories. As is well known, the output from a given size of dynamo, as in | practically all electrical machinery, is limited by the amount of heat which can be dissipated. If, therefore, the dynamo can be internally cooled by a proper ventilating system, greater output may be taken from it. The method of ventilation in this new dynamo is to draw air through it by means of a centrifugal fan incorporated with the driving pulley, the cover band enclosing the commutator and brush gear having louvres formed in it for the admission of air, which issues through holes in the end plate behind the pulley. Air is therefore drawn in at the rear end of the machine and drawn out by the fan at the front end, the air stream from the cooling fan of the engine assisting its action as it passes over the dynamo. As a result, of this system the machine runs cooler, and is said to give an increased output by as much as 25 per cent, over the non-ventilated dynamo of the same size.

The correct procedure when changing a wheel of the bolt-on type Is as follows:— Before jacking up the car remove the spare wheel and just slacken off the nuts of the wheel which is to be changed for a turn or so. Then jack the car up, remove the wheel, and unmediately put on the spare, which should be kept as close at hand as possible. The reasons are as follows:—If the bolts are undone when the car is jacked up an unnecessary strain may be put on the brakes, or if the brakes are not being used the means of preventing the wheel revolving—usually by means of wedging one's leg against it — will spoil one's clothes. The' spare wheel should be removed before jacking up, as in detaching it one might easily shake the car off the jack. By placing the spare on the bolts immediately, the risk of the car falling off the jack on the brake drum is reduced to a minimum. When putting on a wheel, place the nuts inside the wheel brace and tighten up as much as possible with the. jack raised, then lower the jack and tighten the nuts completely.

Dry sump lubrication is an efficient system which is employed extensively in aeroplanes and certain large types of motor vehicles, but is seldom met with in light cars. In some circumstances it has special merits, and is, of course, essential in aeroplane practice, since the very steep angles at which the engine runs would interfere seriously with the usual form of "wet" sump, in which the bottom of the crankcase forms the oil reservoir. | With the dry sump installation the reserve of lubricant is carried in a sepa" rate tank, and on cars the tank is ordinarily mounted well forward at some suitable point where the air stream while the car is in motion will help to cool its contents. The arrangement of the oilways is similar to that adopted for conventional pressure lubrication. But it is necessary to have two lubricating pumps. One draws the oil from the reserve tank and forces it j to the frictional parts of the engine, ! while the other draws off the oil after it has passed through the engine and returns it from the crankcase to the tank. It will be seen, therefore, that the lubricant is constantly circulated, but since it is not carried in the crankcase there is less risk of dilution and contamination. For racing cars such a layout has definite potential advantages, in that the tank can be so de- | signed and placed that a much better cooling effect is procurable.