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Aviation History
1911
1911 - 0077.PDF
ERD-AlLARMS FOR FLYERS. RESULTS OF OUR COMPETITION. OF the^ hundred or so designs submitted for our Speed Alarm Competition, forty-two were provisionally approved, and of these we have finally selected five that we are forced to declare equal in merit. Had it been possible, we should have preferred to award the prize for one design only, but the circumstances of the case in our opinion prevent this, and the result is that five com petitors share the award. Fundamentally, the reason why this is so is because no competitor has, so far as we are aware, taken any definite steps to have his ideas put to a practical test, which according to the terms of the competition would have been taken into consideration. We had, therefore, necessarily to judge the merits of different designs purely on their plausibility, and in the light of common knowledge in matters relating to constructive detail. As a result of this necessity, it has been essential to regard certain entirely different sound instruments as potentially equal in merit, on the grounds that either one of them would sufficiently serve the purpose required of it. Such, for example, is the case with the whistle, the bell or gong, and the siren. On the other hand, in the absence of any evidence to show that such simple and well-recognised devices are unsuitable, there is no particular purpose in going out of the way to introduce other principles such as those underlying the action of the musical box or the gramophone, but we do not thereby suggest that such schemes would not work. Then, apart from the sound instrument itself there is its operation to be considered, and again it is necessary to recognise as equally meritorious the employment of air pressure on a plane, and the use of the rotation of a propeller windmill. Both are plausibly suitable for the purpose required. In connection with the propeller wind mill, which is essentially a rotary movement, the introduction of some form of centrifugal governor is more or less a necessity, and may be considered as an incidental part of the system not calling for special recognition on its own account. Thus we have three distinct sound instruments, and two distinct principles of operation that it has seemed to us only fair to recognise as being on a potentially equal footing, and as we have been unable to find any one instru ment in either category that deserves to stand out above others in another category we have decided, as already mentioned, to divide the prize in the following way :— The question of a multiple note alarm, which was suggested initially as being preferable, other things being equal, has not met IN any engine the following factors must be observed to eliminate vibration. I. The centre of gravity of the moving parts should remain stationary. 2. The turning moment must be constant and always positive. The former condition can be arrived at fairly satisfactorily ; but the latter can only be obtained by employing a sufficient number of cylinders or impulses in comparison to the number of revolutions in the crank-shaft in the same interval of time. By so doing we can obtain a fairly constant torque, but the fact must not be lost sight of that the application of the thrust to the crank-shaft must be so arranged that no longitudinal period of vibration is set up. We have in the purely radial engine no difficulties of longitudinal vibration, as the application of load is all in the same plane and we at once overcome what was at one time a source of some trouble, viz., want of longitudinal balance. Secondly, in the radial engine, balance in other directions is not a difficult matter, and though perfect running balance may not be obtained, the centre of gravity of the moving parts moves in a circular path and does not violently oscillate. If one considers the working of the four-cycle motor it will be noticed immediately that production of energy is only obtained during one stroke of the piston in four ; also, all parts which serve to transmit the power—that is, the connect ing-rod and crank-shaft—actually do their full work only during the explosion period for which they are calculated. This is a very small fraction of the working stroke, and still smaller of the complete cycle. We have, therefore, in the radial design several cylinders operating the same crank-pin, and we adopt the disposition * Abstract of a paper read by Mr. R. W. A. Brewer before the Aviation Section of the AA. and M.U. with any really satisfactory solution in the competitive designs, and under the circumstances our awards all go to the simple alarms that best fulfil the primary conditions of making one distinctive sound. The awards are as follow :— Whistle.—No. 31, G. Boocock (published December 17th), for the best design of whistle. The merit in this design lies in its simplrcity and in the introduction of the inclined plane for operating a rotary grid valve, which type of valve is well suited for closing a large orifice with a very small movement. The use of the pressure plane in this manner, although only crudely represented in the com petitor's sketch, lends itself to a suitable arrangement. Siren.—No. 37, \V. Langdon-Davies (published December 24th), for the best siren. The merit in this design lies in its simplicity and in the control of the conditions under which the siren operates. The siren is released by a pressure plate at the required s^eed and the construction of the members of the sound instrument therein form their own propelling mechanism. Gong.—No. 16, E. V. Gratze (published September 24th), for the best mechanical bell or gong. The merit in this design lies in its compact arrangement and in the well-considered disposition of its parts. Systems of Control.—Propeller. No. 41, A. E. Rutherford (published December 31st), for the best design of propeller con trolled apparatus. The merit of this design lies in its compactness, and particularly in the use of a form of governor that has generally proved itself superior in instruments of an allied character, such as speed indicators for motor cars. The apparatus, as shown, controls the ringing of an electric bell. Pressure Plate.—No. 27, W. Read (published November 26th), for the best design of pressure-plate control. The merit in this design lies in the idea of using two plates of opposite inclination opening under the pressure of the wind like swing doors in a passage. This idea is doubtless superior to a system employing a single plate, as it would seem less liable to be affected by extraneous conditions, inasmuch as both plates have to open equally to effect the control, which in this case consists of closing the electric circuit of an electric bell. Accidental movement of the instrument to one side or the other might jerk one plate against the contact, but it would not probably jerk both plates in opposite directions simultaneously. The above-mentioned prize winners are requested to communicate with the Editor. of the said cylinders in star fashion around the crank-shaft of spiral shape. To reduce the variations of the couple to a minimum it is necessary that the explosions in the different cylinders of such an arrangement succeed each other in absolutely equal intervals, and therefore as unequal number of cylinders must be taken with a minimum of five. The ignition as well has to take place in such a manner that those numbered 2 and 4 fire first, and those unequally numbered afterwards, that is, at the second revolution of the cycle. The object of a designer is to obtain the greatest possible ratio of cylinder volume to total volume of engine, and in radial construction we have the nearest approach in this respect to the turbine. The complete engine in star shape gives a symmetrical appearance. However, in actual prac tice this arrangement produces several difficulties, which, although already solved, appear insurmountable. For instance, if we imagine the cylinders separated by a horizontal line passing through the axis of the crank-shaft and we then turn the lower part of the engine about 1800, the cylinders which were below the horizontal line would come above it and fit between the others. Those would be connected to another crank-pin at 180° from the first. This gives exactly the same turning effect as a truly star- shaped engine and renders lubrication by splash a much simpler problem. The semi-star-shaped engine has another advantage, viz., that it facilitates air-cooling by means of radiating ribs. This method of cooling in aero-motors has been fully proved, and presents the great advantages of lightness and simplicity. All water-pipes, the radiator, circulating pump, complicated joints, &c, are done away with in company with their weight and tendency to leakage. ® ® ® ® RADIAL ENGINES. 79
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