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Aviation History
1912
1912 - 1198.PDF
strut as he jockeyed the machine down at an easy angle —he did not dare to put it to the strain of a sharp descent. ... Suddenly the strut crumbled up, and through the window the clear-cut outlines of the chassis against the whiteness below became a hopeless tangle of wires and woodwork. For a second the left wing spar tore at the socket in the fuselage, and then with a great crash the wing flung itself upwards. He caught a glimpse of the dear white face beside him, and a spurt of blood where one of the top wires from the wing had lashed it. He gripped her hand fiercely. Then the right wing broke loose, and shut up beside him. Desperate, he pressed the engine switch, but, for some reason, unavailingly. With a maddened roar the helpless, broken thing plunged down towards the calm white earth. To right and left of them the fabric tore loose from the framework, and beat the air thunderously around them. Under the awful speed of their fall he found himself sliding helplessly on his seat. The ground below became blurred and indistinct; it was impossible to bring it into focus. And his senses were going— breathing was almost a thing of the past. . . . He turned his head, and looked straight at his wife, and in her eyes, even in those doomed, shrieking ® ® NOTES ON moments, he found his solace. The truth was there- naked, eternal. She had not done that thing. If they could 'live—if he could have the chance to tend her against the hurt he had given—If . . . But, of course, it could not be. Struggling with his own senses he felt her droop against him nearer, nearer, as the end rushed at them .... Then at the limit of consciousness, at the last bare moment of agonised living, there was a great flash of light. * * * * "J™!" • L u- u u He sat up in his chair with leaping heart, his breath coming in gasps. His wife stood before him, and the room was flooded with light. " Jim, I've come to explain," she said gently. He stood up, dazed, and found his voice. " There's nothing to explain dear, I—I've had my proof." He turned to the mantelpiece and taking down the letters from it, silently, tore them into many pieces, and flung them on to the dying embers. Then he turned to meet her wondering, misty eyes. " That's all finished, Molly. Forget it—and forgive." He kissed her gently, reverently. Then " Come, I'm going to walk down to the shed and see if the old machine is all right for to-morrow ! " They went out into the starlight, hand-in-hand. ® ® THE GNOME. By EDWARD THE following notes may seem very elementary to men who know all about keeping engines in order, but there are a great number of others, doubtless, whose practical experience may not have been extended in this direction and to them these little details may perhaps prove of interest. To a few of the mechanics beginning practical work, they may even be of some assistance. In any case, there is this to be said on the subject at large, namely, that men's lives depend on the mechanics' carefulness and carefulness depends very much upon the mechanics' appreciation of the little points of which I have endeavoured to mention a few. A first class man of experience gets to do all these things, and many more, without thinking about them. They become second nature, like the putting on of one's clothes in the morning. It is just for this reason that some of these details that are of distinct importance are seldom talked about. On completing a run, a Gnome engine should be well washed out with paraffin, injected through the cylinder head by means of a syringe. When every cylinder has been so treated, the engine should be turned rapidly for a minute or two, and on coming to rest, care should be taken to see that the exhaust valve of the bottom cylinder is left open. This prevents the lubricating oil from accumulating in the cylinder. If the engine is to be left standing for any length of time owing to bad weather or other causes, it is advisable to give the engine one or two turns daily, and make sure that a different cylinder comes in position at the bottom. Should this be neglected the exhaust valve springs become weak through remaining depressed in one position too long. When running a Gnome engine, care should be taken not to exceed the number of revolutions stipulated by the makers, which is somewhere about 1,100 r.p.m. A higher engine speed can be attained by extreme spark advance and setting of valves to suit, but the extra wear and tear is scriou«. Much labour in overhauling is avoided by careful adjustment of the mixture drawn in from the carburettor. The petrol supply should be so regulated that an even firing mixture is supplied to the engine, and as much air as is consistent with maximum efficiency should be taken in. A longer time can therefore be allowed before it becomes necessary to take the engine down for cleaning. The lubricating oil should be strained before passing into the oil tank and the pump supply so adjusted that the delivery of oil to the moving parts is not excessive but just sufficient to keep the bearings and cylinder walls well lubricated. An excess of oil means trouble through carbonisation rapidly taking place, and misfiring often occurs by reason of the plug points becoming sooted up. The oil enters the crank-case with the mixture, and becomes atomised by the churning action of the connecting rods. Conse quently, the finely atomised oil passes through the inlet valve to the M. LING. top side of the piston, and some of it is burnt and deposited as carbon on the walls of the combustion chamber. The greater the amount of oil supplied to the engine, the heavier and more rapid the deposit of carbon. Particular attention should be paid to the sparking plugs, which must be examined frequently, and the platinum points kept clean, and set to the proper gauge for ensuring the right spark gap. The distributor disc on the engine must be inspected occasionally and kept free from dirt and oil. The brass contact segments should be refaced at intervals by carefully rubbing the distributor, face down, on a sheet of plate glass or other suitable surface, with the finest emery flour and oil. Also make sure that the carbon pencil or brush is held in close contact with the face of the distributor, and makes a perfect contact with the same. There is a peculiarity about the exhaust valves on Gnome engines that should be watched. The bridge piece that carries the guide for the valve stem is thicker in proportion to the surrounding metal of the detachable head and, when heated, has a different rate of expansion. Owing to this, the valve seating becomes warped, when the heated head contracts on cooling, and causes the seating to assume a slightly oval shape. Careful re-grinding is then necessary, and in some cases the valve seat must be trued up in a lathe to restore it to an accurate fit. Excessive wear ako takes place with the bottom spring of the set operating the exhaust valve and needs frequent attention. When renewing these springs, do not fit a complete new set to one cylinder and neglect the others. The best method is to remove all the bottom springs at the same time when they show signs of wear, which ensures all the exhaust springs being more nearly of the same strength in actual use. Sometimes, when an engine gets hot, explosions take place after the magneto has been " cut out " by switching off. This is a sure sign of excessive carbonisation and is due to small particles of carbon becoming incandescent by the heat of the explosions, and remaining so a sufficient time to automatically ignite the fresh charges drawn in from the carburettor. When this takes place the engine should be taken down and thoroughly overhauled. ® ® ® ® An Aluminium Calendar. ONCE again we have to thank Mr. Robert W. Coan for his annual reminder of this season of good will. This year it takes the form of a perpetual calendar, on the front of which is cast an old English scene " The Squire's Xmas Box." Although it is perhaps not quite so utilitarian as the charming fruit dishes with which Mr. Coan used to favour his friends, it is an excellent example of the remarkable casting in aluminium turned out at the works at 219, Goswell Road, E.C. 1198
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