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Aviation History
1924
1924 - 0596.PDF
SEPTEMBER 25, 1924 covered and having its corners rounded "off, while the rear portion is the usual longerons and struts type with wire bracing. The cockpit, as already stated, has accommodation for two occupants sitting side by side, and a door on each side gives ready access to the " office." As prescribed for the com petitions, dual controls are fitted, the rudder-operating foot- bar having a parallel movement, while the elevator and ailerons are worked by a single control column centrally placed. This column can be readily adapted to either " branch " control or to plain knob. The deck fairing runs through between the two halves of the cockpit, and there is a small separate windscreen ahead of each coaming. The main planes of the " Bluebird " are of orthodox con struction, with spruce spars and ribs, the latter being of the Warren girder type and very light (5 ozs. each). The drag struts inside the wings are in the form of Duralumin tubes, and the drag bracing is 4 B.A. tie rods. The inter-plane struts are also in the form of Duralumin tubes, fitting into Duralumin sockets and taper pins. As will be seen, from the general arrangement drawings, the wings axe set at a fairly pronounced dihedral angle, and, what is more unusual, they are slightly swept back so as to give the correct trim for the particular placing of the pilots. Inciden tally, it may be pointed out that with the side-by-side seating arrangement no change in trim takes place when the machine is being flown solo, and thus it is never necessary to carry any ballast. The wings are made to fold back, hinged ribs being fitted in the trailing edge adjacent to the hinges. The undercarriage is of simple V-type, and the fact that the fuselage is of considerable width has allowed of keeping the chassis V's vertical, as seen from in front. The shock- absorbing gear is in the form of telescopic tubes, with rubber blocks working in compression, and recoil dampers are incorporated. All control surfaces are of large area, and it is expected that the machine will be very manoeuvrable, even when close to the stalling angle, a very necessary precaution in view of the low-speed tests which have to be flown close to the ground. The three-cylinder Blackburne radial engine is mounted on triangulating tub.es meeting on dead centres, and there is a fireproof bulkhead between the engine and the cockpit. The petrol tank is mounted in the top plane centre section, and for the purpose of the competitions is fairly small and takes the contour of the wing section. For use later on, should a larger petrol capacity be required, a larger tank can easily be fitted. It might be mentioned that the machine has been " stressed " for a more powerful engine, and should, as seems likely, a 1,500 c.c. engine be required later, the only change necessary is the subsitution of larger cylinders and pistons, the Blackburne crank-case and crankshaft having been designed for the larger capacity. <$> <Z> <$> <$> THE BRISTOL "BROWNIE" MONOPLANES (NOS. 1 AND 2) Bristol " Cherub " Engines OF exceptional interest are the two monoplanes entered for the Lympne competitions by the Bristol Aeroplane Co., Ltd., of Filton, Bristol. Not only do they represent the first designs by Captain F. S. Barnwell since his return from Australia, but the -, or rather one of *hem, represent the only example in the competitions of all-metal construction. The Short monoplane has an all-Duralumin fuselage, but the wing is of the usual composite wood and metal construction. The same applies to the other Bristol monoplane, which has a steel tube fuselage but a wooden wing. In the following notes any reference to the fuselage applies equally to both Bristol Brownies," but the sketches showing wing details, and the notes dealing therewith, refer specifically to the all-metal wing. That no detailed reference is made to the wooden wing is not due to any lack of interest, for, as a matter of fact, even the wood wing incorporates many features that might have been illustrated and described, but in an issue like the present we are naturally somewhat limited as regards space, and we have, therefore, thought it well to devote such space as is available to a fairly detailed reference to the all-steel wing as being the more interesting of the two, especially as this is the first time one has had an opportunity of illustrating in detail the Bristol methods of steel construction, upon which, although it has not been generally known, the Bristol Company has been doing a great deal of experimental and research work. As regards aerodynamic design, the Bristol " Brownies " are low-wing, cantilever monoplanes with bi-c.onvex aerofoils tapering in chord and depth from root to tip. The section, although of great maximum depth, is not a high-lift section, but is rather on the lines of some American aerofoils which were described in FLIGHT last vear. As a matter of fact, the particular section employed is not identical with any of the American sections, but is one developed by Captain Barnwell. Wind tunnel tests have been carried out in the Bristol wind tunnel, so that very complete data should be known to the designer, the more so as the first machine was finished and flying some six weeks ago, so that there has been ample opportunity to discover whether or not the actual light 'plane tallies with the wind tunnel model. The fuselage is of fairly large maximum cross-sectional area, and is of the flat-sided, flat-topped variety. The machine is of fairly high aspect ratio, and the body is of rather more than usual length, so that one would expect the machine to be pleasant to fly. The flying tests have, we believe, proved this to be the case, and the " Brownies " are said to handle par ticularly well. Large tapering ailerons are fitted, which should give ample lateral control. With reference to the latter a somewhat novel arrangement has been adopted. Instead of the usual " positive " cables, the ailerons on the " Brownies " are pulled down by rubber cords suitably tensioned, and the " return " cable is connected to the controls and positively operated. The object of this arrangement is to impart to the wing to some extent the principle of auto matically variable camber, since, as the speed increases and the pressure on the ailerons with it, the flaps will auto matically rise, With reference to structural design, steel is, as already mentioned, the material used, exclusively in one machine and in the fuselage of the other. The fuselage is a girder of steel tube longerons and struts, braced by piano wire and turn- buckles. Fig. 8 in our set of sketches shows a typical fuselage joint, from which it will be seen that a short length of sleeving is slipped over the longeron at the strut attachments, the THE BRISTOL BROWNIE," BRISTOL 596 CHERUB " ENGINE : Front view.
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