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Aviation History
1917
1917 - 0583.PDF
JUNE 14, 1917. valve, which showed slight pitting in tSe seat was the only part replaced. No other parts required any re-adjustment, and both main and connecting rod bearings showed not the slightest sign of wear. The same was the case with the gudgeon pins, pistons and cylinders. The engine was then reassembled and run for one hour, during which the readings below were taken. During the hour run 32 gallons or 199 lbs. of fuel were used, making a fuel consumption of "5715 lbs. horse-power per hour. The oil consumption was "0435 lbs. horse-power per hour. - Time H.M. o IS 3°45 1 0 Engine R.P.M. 1811 1835 1848 1801 1835 H.P. 308 3-f* 314 313 317 Oil Pressure 68 69 60 57 58 GhTl Water Inlet. 94 99 103 98 102 Outlet. 134 132 135 134 134 Average 1826 312*8 60*4 99* 2-K 134: st. V A VIBRATION TYPE TENSION METER. IN the course of " tuning up " an aeroplane it is not always an easy matter to judge of the tension in each bracing wire. Twanging the wires certainly gives some sort of an indication of the tension, but the accuracy obtainable in this manner is necessarily small. Nor is it possible, without the employment of some standard of comparison, to attain any uniformity, since no two men will tune identical machines alike. We have even heard of an official, probably of a musical turn of mind, who insisted on having a machine so tuned up that twc wires, anchored to the same strut socket but being of different lengths, emitted exactly the same note when twanged. Instruments have, we believe, been employed in which a slight sideways displacement of a short length of the wire served as a measure of the tension in the -wire. The phenome- non of vibratory resonance has already been utilised for certain types of frequency meters, for speed indicators of electric motors, &c, but so far as we are aware, the first to" suggest and actually employ the same principle for measuring the tension in the bracing wires of an aeroplane is Signor C. M. Lerici, engineer to the Societe S.I. A. (F.I.A.T.j, of Turin, Italy. The Lerici vibration type tension meter, illustrated in the accompanying diagram, consists of a series of small leaf springs of steel, secured to a base at one end, and free at the other. The length of each spring is proportioned to its proper period of vibration. When the base of the tension meter is placed lightly on a bracing wire that has previously been caused to vibrate, for instance by twanging the spring whose period approaches most closely to that of the wire will show a very sensible vibratory movement. Signor Lerici points out that for a given wire subjected to a tension T, the frequency of vibration being n, one may write1 the equation T = An2. The vibration type tensionmeter gives directly the value of n, and as k is constant for a given wire, the meter gives in fact a measure of the tension T. The number of leaf springs, or in other words the length of the instrument, will, of course, depend on the number of different lengths of bracing wires to be tested, but Signor Lerici informs us that he has found by experience that for all modern biplanes, including the most recent types of 1917, a series comprising springs of 20 to 60 vibrations per second is sufficient, since it covers the range met with in these machines. During some destruction tests on new types of aeroplanes it has been found possible to follow from the start of the tests the distribution of tension in all the bracing wires, and to detect every irregularity which the calculations had not fore- seen. Signor Lerici has also been able to individuate all the members (struts and bracing wires) which were influenced during flight by the vibrations of the motor, the fundamental Diagrammatic sketch of the Lerici vibration type tensionmeter for aeroplanes. vibration of which has a frequency of 22 to 25 per second (1,300 to 1,500 r.p.m.). With regard to the effect of the presence of wire strainers, it was found that the error due to these was in the neighbourhood of 5 per cent. Standardisation of Copper Tubes for Aircraft. IT is officially announced by the Air Board that difficulties having been experienced by aircraft contractors in obtaining supplies of copper tubing, the causes were investigated, and they were found to be—(1) the great variety of sizes called for ; and (2) the fact that tube makers received orders very irregularly and for small quantities. Arising out of the in- vestigation, the Specification Committee of the Air Board has decided that, in future, copper tube for aircraft contracts will be specified in terms of external diameter and legal standard wire gauge. As far as possible tubes of 20 Gauge (.036-in.) will be used, to the exclusion of all other thick- nesses. Where, for special considerations, it is desirable to use other thicknesses, the choice will, as far as possible, be restricted to Gauges 16, 18 and 22. The last named is diffi- cult to manufacture, and will be avoided as far as possible.' A new Air Board Specification for copper tube will shortly be issued, and will have as an appendix the following list of sizes and gauges which the Air Board regard as standard :— 20 Gauge.—-ft-in., J-in., TVin-. f-in- i?<rin-. hin- i-in-.f-in., f-in., i-in., i^-in., ij-in., i|-in., ij-in., i|-in., If-in., 2-in. 18 Gauge.—i-in., i£~in.^i£-in., if-in., 2-in. i6Gauge-—J-in., f~in., f-in., f-in., i-in., ij-in., ij-in., if-in., 2-in., 2^-in. 22 Gauge.—i-in., i|-in., ij-in., if-in., i$-in., if-in., 2-in. Zeppelin Activity. REPORTS from Copenhagen state that on June 7th two Zeppelins were observed off Klitmoeller, on the west coast of Jutland, going southwards. At 3 o'clock the following morning a heavy cannonade was heard lasting for an hour and a half. After the cannonade was over a Zeppelin was observed very far from land following a north-westerly course. From Ameland, via Amsterdam, it is reported that some patrol vessels, accompanied by two seaplanes, passed the island on the morning of June 11. The Handelsblad learns from Vlieland that a Zeppelin passed by on June 10th, coming from the west, and dis- appeared in a northerly direction. Later, another Zeppelin was observed, while at the same time a squadron of war vessels was sighted steaming eastwards. 583
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