FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1912
1912 - 1122.PDF
NOVEMBER 30, 1912. Edited by V. E. Aero Exhibition, Olympia. Modtl Section. Class II. Models Driven by any Other 1 o*er. THE wording of this class again appears to be a l.ttle unfortunate, but taken in conjunction with Class I, what it really means is models fitted with a rubber or spring motor. Since weight for weight about six times as much energy can be got from rubber as from any form of steel spring, this class really signifies rubber-driven models. It is divided into two sections— a) rising from the ground or self- launching models ; (/>) hand launched. With regard to the former the minimum weight is 8 ozs., the qualifying duration 30 sees., design and construction receives 50 marks, flight duration 50, stability 50. We repeat the above here because it is absolutely necessary that competitors should keep all these points prominently before them when designing and constructing the model—to which, it should bs noted, there is no maximum weight limit. The difference between the conditions here to be fulfilled and those asked for in the " Wakefield " competition should be carefully noted. In the latter the tests were (I) shortest run before ri-ing, (2) duration of flight, (3) stability; marks : 50 for test 1 ; 100 for test 2 ; 50 for test 3. Here we have a premium tet on duration, and a quite unimportant factor, viz., shortest run before rising given a very prominent place. In the forthcoming competitions the premium is set not on duration, but on a model scientifically designed right through; a model also which will be expected to show a certain amount of JOHNSON, M.A. It is true there is no separate chvs, but that is no reason why they should not compete. It is certainly not an impracticable achievement, the building of a tractorplane with a minimum weight of 8 ozs., which shall make a duration of over 30 sees. It may be difficult, but as a matter of fact we know personally of two mstances- in which it has been done. Let us suppose the machine to be one with a single propeller, the ordinary duration can be considerably increased by the use of a geared motor, using two cogs of the same number of teeth, one on the propeller-shaft the other running in mesh with it, the cogs u-ed should have as small a diameter as possible, owing to the rubber carrying hooks turning in opposite directions, they can turn quite close together, and even if the rubber motors touch they do not interfere with one another, most machines we have seen have been- fitted with gear wheels about three times the size they need be. We saw at Messrs. J. Bonn and Co. a few days ago some cog wheels excellent for the purpose, very strong and very light and with broad and deep teeth, an essential feature. Vaseline should be used as a lubricant for the cogwheels, but see none gets on your rubber. Use oil for the bearings. One great advantage that a geared motor of this description possesses is that, the torque of the two rubber motors being oppofite in direction and equal in amount (the same amount of rubber being employed on each motor), the twisting action on the tail is entirely done away with; and it is this very twisting action which has- brought to grief many experimenters with this type of model. The rubber can be carried the full length of the fuselage, which can be covered in ; in fact, an almost scale-like model can be constructed on these lines, save that the fuselage will be longer than that employed in the case of present day full-sized tractors. The position of the planes will also be somewhat different, being nearer the tail. Those competitors who favour the well-known loaded-elevator type of model will undoubtedly be expected to show something of a practical character in the design of their chassis, i.e., a type of chassis which could (suitably modified) be applied to full-sized Mr. F. W. Jannaway and three of his models. detail, and not be a mere flying stick on wheels. For instance, a model in which the only connexion between the elevator and main plane is the stick carrying the rubber motor or motors is likely to receive but scant attention at the hands ot the judges. The increase of the weight from 4 to 8 ozs. in the Wakefield competition had the effect not so much of increasing the span of the four ouncers as (generally speaking) of turning them from mono planes into biplanes. The chief reason being that aeromodellists were thereby enabled to obtain by this means sufficient lifting surface to enable them to carry the increased weight, without departing from their previous wire framework for the wings, which in models of a certain size and span has been found to give such excellent results. We shall certainly, however, expect to see at Olympia, even in this class, some models with properly built-up wings, double surfaced, &c. The design and construction of the landing chassis is also one to which especial attention should be piid ; everything wherever possible should also be of streamline form. The gliding angle of the model, and the construction and kind of propeller or propellers employed, require special attention. The competitor should also carefully bear in mind that a single- propeller-driven model showing equally good stability, &c, as a twin-propeller machine is distinctly its superior. Several correspondents have written pointing out that there is no separate class for tractors, and that they are therefore out of the running ; we do not agree with them for the following reasons:— I 122 Mr. F. W. Tannaway's R.O-G. model. design. The majority of such models as generally flown most certainly could not. It would, in our opinion, be the greatest mistake to lay too much stre-s on duration—provided you can accomplish 35 to 40 seconds we do not think you need' trouble about much else in this direction. There still remains other types of models to be considered—for instance, the tail type twin propeller model, the propellers being placed behind the tail; and the tail type model in which the pro peller or propellers are in the rear of the main planes The last named type offers great constructional difficulties s<. tar as the motor is concerned, it being almost impossible to design a form of rubber motor which should give the necessary qualifying 30 seconds duration and fit in with the general deign of the machine. With regard to the former this is a model which has been very highly developed so far as duration is concerned by certain experts—the best known probably being the present official record holder, Mr. A. F. Houlberg. Before deciding on such a type of model as this, however, the designer would do well to carefully consider how such a design could be applied in full-sized practice, in which the distribution of weight is so very different, and how far it would require modification to be so applied. The foregoing by no means exhausts all the types that would be con sidered, but we think sufficient has been said to give some indication of the lines along which the competitor should proceed. Above all, avoid building a flying stick on wheels—it will stand no chance. To anyone who is not an expert, we should most strongly advise
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
