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Aviation History
1922
1922 - 0255.PDF
- MAY 4, 1922 inserted for enabling two or more men to lift the tail when the machine is being moved about on the ground. A fairing in the form of light formers and stringers is built on outside the main fuselage structure, to bring it up to an elliptical section. The cabin portion of the fuselage is, as already mentioned, built up as a monocoque shell, with formers of rectangular box section, but forming, of course, ellipses conforming to the shape of the fuselage. Into these formers are let the longitudinal stringers, or longerons, and the whole is covered with three-ply wood, screwed on in relatively small panels. When finished, the entire cabin portion is covered with fabric and doped. The Wing Structure It has already been stated that the wings of the " Vulcan " are of thick section, and that therefore the spars are of considerable depth. The spars are of the box type, with top and bottom flanges of spruce, and sides of three-ply wood. As in the case of the fuselage longerons and struts, the wing spars are taped and doped, the fabric further strengthening and protecting the wood underneath. The compression struts between the spars are circular tubes of wood, and constructed similarly to the longerons already described. The ribs are of somewhat unusual construction, as shown in one of our sketches, and consist of lattices of spruce, the lattice bars, some of which are single and some double, according to local loads, being attached to the spruce flanges by Vickers Duralumin rivets. This form of rib has been found to be very strong for its weight, and is now employed in all Vickers machines. ' chord from the leading edge. This tube is carried in bearings mounted on channel section steel brackets bolted to the rear spar. According to whether the aileron is up or down, its leading edge moves below or above the rear spar, and the portion in front of the pivot serves as a balance. This type of aileron has the advantage that the twisting stress imposed by a horn balance is avoided, but, on the other hand, the load on the steel brackets, and the resulting twisting stress on the rear spar, is probably considerable. However, owing to the thickness of the wing, it is a fairly easy matter to take care of these loads. Aerodynamically, this form of aileron is, we believe, very efficient. At any rate, it appears to be so on the Handley Page W.8 and W.8B. There is no direct control to the ailerons of the lower plane, these being operated by aileron struts running from lugs on the top aileron to similar lugs on the lower ones. It should be observed that these struts are attached to the leading edges, and not, as is more usual, to the trailing portion of the ailerons. This is another instance of the amount of thought and attention given to details by Mr. Pierson. By the arrangement adopted, the aileron struts are 'made to work in tension when the greatest loads occur, and only work in compression under relatively small loads. It might be mentioned that the ailerons are standardised so that the same spares will do for both top and bottom planes. The tail is of the biplane type, similar to that of the " Viking," and does not call for any special description. The Engine Mounting One of the accompanying sketches shows the mounting of the Rolls-Royce " Eagle." The whole engine mounting THE VICKERS " VULCAN Some details of the construction of circular and streamline section struts and longerons. As already mentioned, there is only one pair of inter- plane struts on each side. The construction of these struts is illustrated in one of the accompanying drawings. The strut proper is built up of four strips, spindled out to form an elliptical section. To this is added a fairing composed of thin three-ply, supported on triangular formers attached to the back of the strut. Both as regards cost of manu facture and strength for weight, these struts have proved very good, and it might be mentioned that a series of loading tests carried out on specimen struts have given the very high loading figure of 1,000 lbs. per lb. weight of the strut. In other words, a strut weighing 28 lbs. supported an end load of 28,000 lbs. This, of course, is extremely good, and indicates the constructional advantages of this form of strut construction. Add to this that the struts are cheap to build, waste but little wood, and are composed of strips so thin that defects can be easily spotted, and it will be seen that the hollow wood strut is difficult to improve upon. The wing bracing is of straightforward type, with streamline wires attached to wiring lugs of usual type. Owing to the fact that there is only one pair of struts on each side, the bracing has been reduced to a minimum, and probably forms a very good compromise between the usual two-bay braced biplane and the cantilever wing, which works out somewhat heavy. Constructionally, the ailerons are similar to the wings, but the manner of balancing them is somewhat unusual. Instead of being hinged on the rear spar, the ailerons have a tube running through them at a distance of about. 28 of their structure is composed of tinned steel tubes so arranged as to give perfect, or nearly so, triangulation. The whole engine unit can be detached from the fuselage by undoing four bolts and the engine controls and petrol leads. The former are very simple and of short length, owing to the position of the pilot immediately aft of and slightly above the engine. They are all of the pull-and-push rod type, with crank arms where their direction has to be changed. As for the petrol leads, these also are of very simple form, consisting of two pipes, one from each tank, running to a T-piece from which a single pipe runs to the carburettor via a B.S.A. filter. This filter, it might be mentioned, is so arranged that the gauze can be removed and cleaned without interfering with the pipes themselves. The starting gear consists of a transverse shaft running across the sloping tubes of the engine mounting, and driving the engine shaft via chains. The shaft has a handle at each end, so that, if necessary, two men can turn simul taneously. The starting magneto is mounted on the port side, and is driven by a chain from the same transverse shaft. This does away with the old-fashioned way of having the pilot turn the starting magneto while the engineer turns the engine. In order to take up any slack that might develop in the two chains, the transverse shaft is mounted in eccentric bushes held in split collars, so that a slight turn of the proper bushes, according to whether it is the engine chain or that to the starting magneto, tightens up the chains. A nose radiator is fitted, mounted on the tubular engine bearers by lugs provided with rubber washers to reduce 255
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