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Aviation History
1909
1909 - 0467.PDF
AUGUST 7, 1909. MODEL PROPELLERS—FURTHER "FLIGHT" CHALLENGE RESULTS. WE are now able to give some additional figures that have been forthcoming as the direct result of Mr. Cochrane's challenge to makers of small propellers or fans, since the trial of the Watford Engineering Co.'s propeller, to which we referred in our issue of July 17th, was duly carried out a few days ago under our supervision. Summed up briefly, it may be said at once that Mr. Cochrane was not called upon to hand over his five-pound note on this occasion, since, even with his smaller propeller (that denoted " C. 2 " in our previous table), he was able to obtain a greater thrust dianv under the parti- cular conditions that were im- posed that the Watford firm obtained with their "Beedle" propellers. As we took great care to point out in our issue of July 17th, the terms of the challenge merely relate to maximum thrust from any type or size pro- peller when fitted to a certain electric motor coupled up on a 200-volt circuit. It is only stipulated that the pro- peller must not weigh more than 6 oz. with its boss ; but, on the other hand, it is immaterial how much energy it absorbs or what speed it happens to make. In other words, the question of efficiency does not enter into the question, except in so far as the opportunity of the tests has been seized upon by us to obtain some rough data that has a direct bearing upon it. Our first illustration shows the " Beedle" propeller which was tested on the Cochrane electric motor, while the accompanying table represents the performance of that propeller placed alongside the corresponding per- formance of the smaller " Cochrane." From the figures •contained in that table, it will be observed that the weight of the " Beedle " was more than double that of •" C. 2," and that the overall dimensions were similar, but The Beedle propeller, the principle ofwhich is shown above, is of very sub- stantial design, and is not only suitablefor use as a "fan," but is doing useful work as a marine propeller and forother purposes. that its efficiency was apparently well ahead of the "Cochrane." Also, it will be observed by comparison with the table in our issue of July 17th, that the pro- peller " C. 2 " gave a rather higher thrust than it did previously, and that the current consumption was appa- rently somewhat lower. Concerning this last point, which affects the accuracy of all these tests, it should be placed on record that the ammeter employed was far from being a high-class instrument. On the other hand, the Elliott speed- indicator which we employed by way of checking Mr. Cochrane's ammeter, was absolutely to be relied upon for its readings. A comparison of speeds and of current indicates the existence of d i s crepancy, and hence the warning may be given that the speed in- dicator, not the ammeter, should b e trusted. Had any great value been attached to the tests, we should have made some careful investigations into the characteristics of the motor, but under the circumstances, it is neither worth while to ascertain by laboratory test the current consumption in relationship to the speed nor the mechanical efficiency corresponding to each reading, for, as we explained previously, they are at best tests of small fans, and furthermore, the motor in question cannot be deemed adequate as a plant for conducting conclusive tests of this character. Two views of the Elliott speed-indicatorwhich was used for these tests and which gives a direct reading in revolutions perminute. Propeller Total weight Weight without boss Overall diameter ... Exerted thrust Current absorbed ... Equivalent e.h.p. ... Thrust per e.h.p. ... Speed of motor "C. 2." ... a*... if Hi 29J1 ••• 75-2I2 147 I,6OO Beedle. 6 ozs. — »» 14J, ins. 2T,\ OZS. •5 amps. • "134 176 ozs. 1,700 r.p.m RULE OF THE ROAD IN THE AIR. A SERIES of provisional regulations, constituting the " rule of the road " for aviators and aeronauts, has been drawn up by the Commission Aerienne Mixte. Aero- planes, when meeting, must keep to the right and maintain a distance of at least 50 metres between each other, but this rule does not apply when there is a difference of at least 30 metres between the altitude of the two machines. Also, in competition, the distance to be maintained between the machines may be reduced to 25 metres by the Judges. In the case of dirigibles a distance of at least 500 metres must be maintained between the two vessels, unless the difference in altitude is more than 150 metres. When flying at night all machines must have a red light on the left and a green light on the right which can be seen both from the front and the side, exactly as in the case of the side-lights of a vessel at sea. White lights must also be placed at the farthest point forward and the lowest part of the machine. Ruling the Air. THE Ligue Aerienne du Nord, who are organising the Douai Meeting, have formed a committee having for its object the collection of documents and evidence relating to the law of the air, to encourage discussion among its members on theories relating to flight, to support aviators and aero clubs in matters relating to law, to endeavour to get some definite rules drawn up at a future International Conference, and to investigate as far as may be public opinion on the subject. 469 C 2
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