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Aviation History
1924
1924 - 0175.PDF
MARCH 27, 1924 The Retractable Undercarriage One of the special features of the " Vikings " has always been the retractable undercarriage, whose wheels move forward and up, following quadrants on the sides of the hull, until clear of the water. In the " Vulture" the same principle has been followed, but an oleo undercarriage has been substituted for the rubber shock absorbing gear of the "Vikings." By working at high pressure (about 800 lbs./sq. in.) it has been possible to bring the weight down to the same as that of the rubber chassis. In fact, the oleo undercarriage is actually a little lighter, by something like 3 lbs. per side. The principle of the Vickers oleo gear, which is used on a number of Vickers types, is that a plunger or piston of slightly conical shape works inside a tapered bore cylinder. When the piston, and the oil above it, is at the bottom of its stroke it exactly fits the cylinder. As it moves up it leaves, owing to the taper, a small annular space around the piston, through which some of the oil passes to the space below the piston. The taper is so proportioned as to give a constant pressure. Working at such high pressures, it was found that the ordinary type of pump was scarcely equal to the job, and consequently Mr. Pierson evolved a special two-stage pump, which raises the pressure to the required figure with apparently- little effort. This pump is shown in place on the starboard undercarriage in one of our photographs. It is held on by clips, and is quickly transferred from one side to the other. The oleo undercarriage makes a very " clean " gear, as will be seen from one of our photographs, and as the weight is the same it should be more suitable for this particular flight than the rubber gear with its need for renewal at fairlv frequent intervals. The tail skid of the " Vulture " is slightly different from that of the " Vikings," and does not form a water rudder. For wheeling the machine about on the ground or in a shed a light two-wheeled tail trolley of Vickers Duralumin is fitted. This trolley is shown in place on the skid in one of onr sketches. The framework aft of the skid serves as a fulcrum for a jack. When the tail has been raised sufficient! ' to allow the wheel axle to be pushed through the skid, the two wheels are easily mounted and secured by wing-nuts. Thus the crew should be able to wheel the machine about without outside assistance. This would scarcely be possible without the tail trolley, as there is a very considerable weight on the tail skid when the machine is standing on the ground. Instead of making the tail skid perform the function of a water rudder, as on the " Vikings," two separate water rudders are fitted at the rear step. These rudders are not parallel with one another, but are so placed as to be in line with the sides of the hull just forward of the step when the rudder is central. This arrangement has presumably been chosen in order to reduce the rudder drag. It goes without saying that both the tail skid and the water rudders are connected up to the air rudders so as to enable the machine to be steered on the ground or water, as the case may be. The Wings As already mentioned, the wings of the " Vulture " are in the form of a single-bay biplane. The centre-section struts, it will be seen, are. raked outwards considerably so as to reduce the free length of spar in the top plane. The main wing spars are of box section, with spruce flanges and three- ply sides, the whole wound with doped fabric. The ribs are of lattice type, with double lattice bars of spruce, riveted to the top and bottom members with Duralumin rivets. The construction is simple, light and very strong. The ailerons are carried on brackets in the form of continuations aft of the rear spar of certain wing ribs of specially strong construction. The loads which ailerons of this type may throw on the brackets are very large, but by having the hinge ribs running through, sufficient strength is provided. The strength of this part of the structure is probably very greatly increased by the semi-circular section three-ply which covers the face of the rear spar, as the three-ply fits into the webs of the hinge- brackets. The details are shown in a sketch. This three-ply probably relieves the rib flanges of most of the shear. The aileron cables are carried inside the wings, and by using a bracket and crank, as shown in one of our sketches, it has been possible to use tie-rods throughout and to do away with alJ cables passing over pulleys. The main dimensions of the Vickers " Vulture " are shown on the general arrangement drawings. The airworthiness weight of the machine is 6,000 lbs., giving a wing loading of 7-25 lbs./sq. ft., which is fairly light for a flying boat, especially in view of the fact that 64 is a fairly high-lift section. The landing speed should not be more than about 45 m.p.h. The top speed with full load and at sea level is about 104 m.p.h., and the climb to 5,000 ft. occupies nine minutes. The cruising speed, as already mentioned, is about. 82 m.p.h. The fact that the Vickers "Vulture" is an amphibian should render it particularly suitable for the flight, as there must necessarily be many occasions when the ability to alight on or get off from land or water equally well, means the difference between success and failure. As all Vickers machines, the " Vulture " is beautifully finished, and no effort has been spared to make the construction as sound as is humanly possible. The fact that the flight' is a private venture, in which the machine is supplied by Vickers, Ltd.. the engines (two of which have been sent to Toronto and Tokio respectively) by D. Napier and Son, and the petrol supplies by Shell, as against the American Army official' attempt, makes the effort all the more creditable, and we are sure all our readers will join us in wishing Squadron-Leader MacLaren, Lieut. Plenderleith and Sergeant Andrews every possible success. THE AIR RACE ROUND THE WORLD Two big attempts at a flight round the world are now claiming the attention of all interested in aviation, and of mere " earth worms " in general—one British and privately or ganised, the -other American and a Government affair. The American expedition, which started on March 17, has thus received a week's start over the British attempt. The British expedition consists of three members : Squadron Leader A. S. C. MacLaren, who is acting as navigator ; Flying- Officer J. Plenderleith, the pilot ; and Sergeant Andrews, who will attend to the " Lion " during the flight—in other words, the engineer. The machine used on this flight is a Vickers " Vulture " amphibian flying boat, fitted with a 450 h.p. Napier " Lion " engine. As this machine is fully described elsewhere in this issue it will be unnecessary for us to make any further reference to it here. The American team is made up of four machines, each manned by a pilot and a mechanic. The names of the pilots are, Major F. L. Martin, and Lieuts. L. H. Smith, L. Wade, and E. H. Nelson. Details of the American expedition and of the machines employed appeared in FLIGHT for December 13, 1923, so we need only refer briefly to the main features of the attempt. In the first place the whole flight is organised by the U.S. Army Air Service, to which both men and machines belong. Thorough preparations have been made all along the route, and the flight has been very carefully planned. They are employing Douglas biplanes, each fitted with a 400 h.p. Liberty engine. These machines will be equipped With either wheel landing gear or floats, according to the special requirements at various points on the route. In comparison, the British attempt will be, we think, a much more sporting effort, calling for no small amount of risk, for while the programme has been well planned and organised, everything has had to be done more or less privately and without any highly organised " official " backing—financial and otherwise. However, considerable assistance has been given by Messrs. Vickers, Ltd., who are supplying everything necessary as regards the machine, and Messrs. D. Napier and Son, who are likewise looking after the requirements in con nection with the engine. The Shell-Mex Co. have established petrol and oil " dumps " at all places of call along the route—perhaps the most important item of the whole expedition. While the Americans are flying in a westward direction, Squadron-Leader MacLaren has chosen the eastward route. Both routes, however, follow practically the same course. We will first go over the British route, and then indicate where the American route, which was given in our issue for December 13 last, deviates from the former. Starting from Calshot, Southampton, the first stopping place is Lyons, thence to Rome, Brindisi, Athens, and Cairo. From Cairo the route follows the existing air-mail line to Baghdad, and then on to Karachi, via Bushire and Charbar. This completes the first of the five sections into which the route has been divided The second section extends from Karachi to Tokio, via Nasirabad, Allahabad, Calcutta, Ran goon, Bankok, across French Indo-China, Hong-Kong, Foo- chow, Shanghai, and along the south coast of Japan to Tokio. The third stage is a most difficult one, viz. : from Tokio to Vancouver. This stretch, alternately over land and water, 175
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