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Aviation History
1912
1912 - 0090.PDF
fgGHT) JANUARY 27, 1912. Conducted by V. E The Petrol Motor. IT would appear at first sight that in this motor must lie the true solution of the model aeroplane motor. It is a motor of this kind which has solved the problem of aerial locomotion as applied to full- sized machines ; and if in the case of full-sized machines, then why not models ? The size of the smallest worMtig-model steam motor is amazingly small; not so the petrol motor—not one, that is, that will work. The number of petrol-driven model aeroplanes that have actually flown is surprisingly small. Personally we only know of two, viz., Mr. D. Stanger's and one constructed by Messrs. J. Bonn and Co. (see FLIGHT, p. 1146, December 30th, 1911). It is worthy of careful note that in the former case the power developed was l£ h.p. at 1,300 r.p.m., and the total weight of the model 21 lbs. In the latter case the power developed was l£ h.p. at 1,500 r.p.m., and the total weight 36 to 45 lbs., according as to how the model was fitted with planes, &c. In the former model the engine was a four-cylinder one, and in the latter (we believe) a two-cylinder one ; in any case it was not a one-cylinder motor. Another petrol model with which we are personally acquainted has a two-cylinder motor, power developed I h.p. (rather more, in fact), total weight of the model 16 lbs. This model has, however, never been tried in actual flight, but we believe it would fly. So far as we can learri, no success whatever has as yet attended any one-cylinder petrol, motor. Nor should we think any success is likely to attend any such efforts. The vibration is excessive, and it is heavier in proportion than the two-cylinder type, and not so efficient. The question of vibration alone is a very serious one ; even a badly-balanced propeller will seriously interfere with, and curtail the length of, flight, to say nothing of shaking loose on the model everything that can be so affected. Another point to carefully note in the case of the petrol motor is that it is only those of from 1 to i\ h.p. that have met with any success. And from enquiries which the writer has made there does not appear to be any likelihood of one of a lower power giving any success at all. If this be so, then, so far as a motor for model aero planes in anything at all approaching a general use, the petrol motor is ruled out of count. For large models weighing, say, from some 20 Jbs. upwards, this motor can no doubt be successfully applied, and one such model might with great advantage be owned by the larger and more im portant model clubs, and kept by them for experimental and research purposes. There are difficulties to be overcome in such a scheme, no doubt, but they .are certainly not insuperable; and it would, or should, prove a bond of common interest to the club, which indi vidually owned models in the natural order of things can scarcely, perhaps, be said to be. Referring to model aeroplane motors generally, what the aero- modellist wants to know is not some hypothetical h.p. at so many assumed r.p.m., and some unknown pressure which the generating plant may never realise—or if it actually does so, its duration may only be soine 5 seconds, but the following items:—(1) What is the total weight Of the Whole necessary plant (generator, fuel, engine, &C.)? (2) What actual propeller-thrust will such a plant give? (3) The duration of such a thrust, and the time during which such is constant, and the manner in which it falls off. Knowing these, it remains to calculate or estimate the approximate weight of the planes, fuselage, chassis, &c, to carry the plant; and if we find •(to take a concrete case) that the static thrust of the propeller is I lb., the weight of the entire plant 2 lbs., and the total weight of every thing 4 lbs., then such a model should most certainly fly. If the total weight is only 3 lbs., then the model should fly well and high ; if 5 lbs., the model may fly if the aerofoil surfaces are very efficient, but the model will (probably) not be a self-rising one. Mr. Stanger's propeller gave a static thrust of about 7 lbs. Notes. 6 Being compelled through a slight accident to dictate our last week's copy, the writing, we are afraid, must have proved troublesome to the compositor ; or, whatever the cause, we are credited with some extraordinary calculations. For 0^450 read 45°, for 400 33'read 420 33', and for 40°4l' read 4° 41'. We have received from Mr. D. Stanger particulars of an official flight made by his 4-cylinder petrol-driven model. This flight was made under the auspices of the Yorkshire Aero Club in July, 1910". The enclosure sent include the original letter of the club to Mr. JOHNSON, M.A. Stanger notifying him of the award of a silver medal as the result of his model's successful flight, and also a cutting from the Bradford Argus from which we extract the follewing most interesting item :— " On one occasion the model sped along the turf at about 16 miles an hour, rose in the air and charged a balloon which was filling in preparation for an ascent later on." Evidently it recognised its ancient enemy at first sight-and went for him for all it was worth. Perhaps the above will convince our sceptical correspondent. Mr. John Mc. C. Clive sends the following explanation re the necessity of fitting a rudder or vertical fin behind the centre of gravity of a tractor-screw monoplane. "The fin is so placed in all monoplanes of the o-P-1-1 type, not so much to resist the unbalanced torque of the motor as to provide a means of maintaining directional stability in the horizontal plane. If not so fitted, the tail of the machine will tend to swing round, using the tractor as a pivot, and cause a head-first dive owing to the centre of greatest resistance to forward motion, i.e., the main planes, being in front. In a tail first, or Valkyrie-type of aeroplane, the point of greatest resistance is in the rear and thus a vertical fin is unnecessary for flight." Just so ; but Mr. Allport's model, illustrated and described below, flies quite well without a fin—and the greatest resistance to forward motion is still in front. And one would rather conclude that the action to which Mr. Clive refers would be still further accentuated with the propellers behind instead of in front—unless, of course, we consider them (in conjunction with the tail) as counterbalancing this effect. It would be interesting to know the effect of a fin (a small detachable one made of aluminium, say) on the very front of Mr. Allport's machine. We should have expected from the type to have seen such a fin there—this being one of the instances in which we should expect a fin to assist in making a model fly straighter. At present the model's path is a curved one. If Mr. Allport has not hitherto tried this—perhaps he will not mind doing so and for warding results : (i) fin right in front ; (ii) fin in rear above tail. The following are the principal details of Mr. C. C. Allport's model (see illustration). Wood, silver spruce ; main stick, 4' x \" x |"; main plane, No. 19 piano wire, silk covered and varnished ; tail, ditto ; weight, 7 ozs., made up as follows :—rubber, 3 ozs. ; frame ready trussed, 2 ozs. ; propellers, I oz. ; main plane, f oz. ; tail, i oz. ; trussing done with No. 6 wire as sold in piano shops, rubber lubri cant soft soap and French chalk, camber to main plane £ in., main plane adjustable for elevation, tail plane fixed, 9-in. propellers, pitch 33J ins., 1,000 turns. Best flight (measured in a straight line) 1,163 ft. We have received from Messrs. Mann and Grimmer one of their "js. 6d. parcels, containing all the necessary parts, together with full directions and drawings for completing and flying their celebrated " Mann " monoplane. The directions, both for making and flying are perfectly clear and explicit, and anyone taking ordinary care and exercising a little patience (an essential qualification for successful model making) should have no difficulty in correctly completing those Mr. C. C. Allport's long-iisUnce 7-oz. model. 90
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