MOTORS & MOTORING

Dominion, Volume 14, Issue 219, 10 June 1921, Page 9

MOTORS & MOTORING

Alternative Fuels. Motorists have become so used to considering that their care can run only on petrol, thet they have neglected to turn their attention to the possibilities of alcohol, bonzolo, and other fuels. Combination of these fuels has been thoroughly tested by the London General Omnibus Company, who report that, thermally, 70 per cent, alcohol with 30 per cent, benzole was more efficient than petrol. Certain alterations of the engine used In the trials in question were necessary to secure this result, and the. compression was raised: to 1601 b. per square inch. The results obtained indicate that there is an illimitable prospect ahead of power alcohol, which, as a by-product of the eugar-reflning industry, and as a direct product from factories, may, before long, become the fuel of commerce. The External Spark Gap,

With the exception of the question whether cars run hotter at night, none has been more controversial in recent years than that of the expediency or otherwise of placing a small gap in the electrical circuit between the spark generator and the plug. Curiously enough, in the very early days of motoring, when coil ignition prevailed, th* external spark-gap was exceedingly popular. Bometimos it took the form of a short length of chain between the cable and the plug terminal, the idea being that the engine vibration kept the chain in motion, and so caused external sparking, A more usual arrangement was to load the'' cable on to a fibre block located on th 9 terminal and to bridge across with a metal strip which stopped just short of the electrode. Undoubtedly a physical improvement resulted from the use of devices of this character, though the gain was often too small to be noticeable. There was, however, a secondary advantage in that one could see'whether current was reaching each plug—an important matter in the days when Ignition: systems left much to bo desired. With the advent of magneto ignitjon, external gaps were abandoned, largely because the manufacturers discountenanced the practice on the ground that it placed an undue strain on the magneto. Recent investigation, however, has revealed that these fears were groundless, and that better sparking at the plug, and cleaner plugs, result from the incorporation of a gap in the circuit, and so with some modern magnetos the current is made to jump from the distributor arm on to the sectors. The length of this auxiliary gap is in the order of .02in.' Motorist* whose oars are equipped with magnetos, fitted with the usual form of distributor carbon brush, may easily secure the advantage of the more modern type, by devising a gap for each plug-lead. This may consist of an insulating block with two terminals not more than l.BOin. apart. The method of attaching would then be to clamp the lead from the distributor under one terminal, and that to the plug, under the other. The important point to remember is that an excessively large gap would not only result In irregular firing, but would tend to place an electrical etrain on the magneto, which, in the event of the safety gap going out of action through any cause, would almost certainly produce a breakdown of. the armature. Aluminium Pistons.

The use of aluminium pistons for automobile work is only in its infancy, and there is yet a Jot to learn in perfecting the application. Aluminium as a metal for pistons hfts found extensive application owing to the fact that it possesses certain distinctive advantages. With a view to establish the factors which govern the making of a first-rate aluminium piston, a competition is to bo held shortly in Germany. Each competitor will ■he supplied with a complete set of drawings to enable him to prepare a set of pistons for both a 30-h.p. car engine and a 45-h.p. lorry engine. The pistons, of which nine must be completely machined for each type of vehicle, may be supplied if desired, complete with gudgeon pins, and should not have more than four piston Tinge, all of which should bo interchangeable for the same size piston. Complete scale drawings of each piston must be submitted, together with the composition of the mixture and the method of casting. The test will be carried out by an independent testing staff, representatives of competing firms being allowed to be present. In fact, the fitting of the pistons and the preliminary trials are to bo subject, to suggestions and recommendations of the competitors. The main ■ tests include the following important points:— horse-power, fuel consumption, tempera-' tiires of circulating water, of exhaust gases, and of lubricating oil. Smoothness of running under full load conditions at three different speeds is to be compared, and also at light load; finally, a reliability trial over four hours, under full load, with records of lubricating oil consumption. In addition, any other test may bo imposed subject to the competitor’s approval. A rough casting is also to be supplied for determining the chemical analysis, the specific gravity, heat conductivity, hardness, and co-efficient of expansion. A prize of jCIOOO will be awarded the manufacturer whose pistons give the best results.

Tho Safety of Flying. Those critics who have said that flying is dangerous will bo confounded by tho statements recently issued by tho British Air Ministry with regard to tho progress of civil aviation. The figures are .extremely satisfactory as regards the safety of flying, and oven if the number of passengers carried and the amount of goods transported by air are not as high as they might bo, tho figures have no relation to the actual safety of commercial flying. From May, 1919, when civil aviation commenced, until the end of December, 1920, British aircraft flew over one million and a half miles and carried out over 62,000 flights. During the period nearly 107,000 passengers were carried and nearly 170 tons of goods were carried oh tho Continental service. But the most satisfactory feature of the whole, report is the fact that out of a total of forty-six accidents, excluding third party accidents, twenty of these did not involve any injury to personnel. Of the remaining twenty-six, eight were fatal and eighteen non-fatal, tho number of passengers killed being eleven, .and those injured ’.numbering eixteen, whilst eight pilots were killed and fourteen injured. This works out at tho rate of 0.10 passenger killed per thousand carried and 0.15 passengers injured per thousand carried. In other words, during the early days of civil aviation, when one -might reasonably expect a fiairly high percentage of accidents the passenger’s chance of death was only one in ten thousand. This rate will bear comparison with any ot; h® r method of transport, and even if the older forms can show a better casualty rate, it must be borne in mind that they have 'been in existence for many years, whilst commercial aviation has been m existence for nbout eighteen months.

Lighting-up time: .To-day, *.28 p.™Next Friday, 4.28 p.m.