THE PROSPECTS OF MAGNETO IGNITION.

Press, Volume LIX, Issue 17922, 16 November 1923, Page 4

THE PROSPECTS OF MAGNETO IGNITION.

A NEW TYPE OP INSTRUMENT. After a period of many years, during which the high-tension magneto was I universally accepted as the best possible form of ignition for a motor engine, wo have now reverted to a stage at which many people argue that tho magneto is doomed and that battery ignition will be the predominant system of the future. Tho reason is, of course, that now that electric lighting and starting are regarded as essentials, a battery must in any case bo carried on a motor vehicle. Moreover, bat-* teries have been much improved and, under the circumstances, it seems quite reasonable to use them for ignition purposes, and so to eliminate a somewhat delicate and complicated machine. The argument that magneto ignition will presently become obsolete is, bowever, based largely on the assumption! that the magneto, as most people knowit to-day, represents finality. Obviously, if it is possible to improve the high-tension magneto in many directions, eliminating risks of breakdown, reducing the size, weight, and cost, unci increasing efficiency, then the apparent advantages of battery ignition am far less obvious, and it becomes more tljan probable that both systems will remain in existence side by Bide. Stationary or Rotating Armatures. This bvings us to the question 'of whether tho ordinary rotating armature magneto is the best tiling of the kind that can bo produced, arid, in Order to decide this, tho writer has recently made a careful study of the system exemplified by the 8.L.1.0. stationary nrmaturo magneto. It willj be interesting to sec how this comparatively new principle, disposes of the troubles and faults likely to arise in connexion with the older, tvpes. The case may/best be analysed by considering each of the main portions, of the magneto separately. ... ; In the common type wo have a rotating armature subjected to the stresses of centrifiigal force and also to electrical stresses. .. On occasions breakdowns ai'iae owing .to this complication of stresses and electrical leakages occur. Moreover, the condenser connexions may at times fail, and, if the condenser itself becomes punctured, a very difficult repair is necessary. In the 6.L.1.C. system the armature is stationary and is subjected dhly.to electrical stresses. Consequently the Windings can be very efficiently insulated, and the whole structure can be scientifically built up without regard to any necessity for standing mechanical stresses. Similarly, the condenser ife stationary, its connexions are robust and, in the unlikely event of a puncture of the'condenser, the whole component can be easily removed and almost instantaneously replaced by a duplicate. Again, in the common system the contact breaker rotates. For this reason it has to be more or less inaccessible and delicate, and the action of ; the. cams 'mavy be, or become, inaccurate. Moreover, the points cannot be watched when in motion.

Reducing Wear. In the 8.L.1.C. system the contact breaker is stationary, easily detachable, and robust. It i 9 easy to -watch the movement of tho points while tho .magneto..is Working and so to ensure that they face one another squarely, and that there is no sparking. Moreover, the timing depends on ono rotating cam, ensuring perfect accuracy. In the old system it is necessary to incorporate such parts as a slip ring, « high-tension collector and connector carbons, a rotating distributor carbon, .and so on. Consequently, it is very difficult to prevent the high-tension parts from breaking down and burning out, In addition, four carbons are generally used,'and wear occurs and causeo a carbon deposit which has to bo cleaned put periodically. In tho 8.L.1.C. system the hightension parts embody only one stationary connector, with one stationary central carbon bearing on the centre of a rotating pierce. There is practically no wear or diist. In tho old system the magnet is comparatively large and heavy, and, being exposed, is liable to damage. In a stationary arrnature machine tli© magnet replaces the rotating armature, and is even smaller than tho part whose position it occupies. Further, it is inside the machine, and is well protected from damage. Next, as regards tho magnetic circuit in the ordinary system, large masses of solid iron have to be used, not only for themselves but for the* pole shoes and the end pieces of the- armature. In the 8.L.1.C. system only the magnet is solid., the rest of the mag.net'tc. circuit beitig completely laminated. The result is much higher electrical efficiency. 'All theso considerations taken together make it possible with the new system to produce a machine far simpler than its predecessor, far less liable to breakdown, smaller, lighter, and cheaper to construct. Tine new system has become possible by reason of the availability of new ma'terial?, unknown before the war. and. without doubt, the progress that has thus been made possible will be reflected in tho very near future by the widely extended use of this new typo of magneto. Almost'certainly the consequence will be that while battery ignition will rightly co'ntinuo to haye- its adherents, the magneto will not lose .appreciably, if at all, in popularity, and, in its new- form, will continue to be the standard type of ignition on the great majority of cars and motor-cycles.

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