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Aviation History
1913
1913 - 0048.PDF
1/ycHf In the Curtlss Engines, a peculiar construction is adopted for the exhaust valve. This has a cast-iron head which is reinforced by a perforated steel disc embedded therein, the whole being electrically welded to the carbon steel stem. In the two smaller models, the connecting rod ends dip into a sheet metal trough, but this form of splash is supplemented by oil which is ejected from radial holes in the hollow cam-shaft on to the rods. Bosch dual ignition is fitted to the two larger engines. The Dorman 80-h.p. Engine is snown in Fig, 8, and the feature which calls for special mention is the method of cooling the crank-case and bearings, and the exhaust from the engine. For the former, a bell-mouthed orifice covered with gauze is formed upon the bottom half of the crank-case, which opens above into the interior. To the upper half a connection is made with the carburettor inlet, so that the air taken by the engine must first pass through the crank-case. It will be clear that such an arrange ment will conduce greatly to the cooling of the oil and the bearings and result in the more efficient lubrication of these parts, while it will be attended with practically no harmful effects, having regard JANUARY II, 1913. to the conditions under which the engine is intended to be employed. Judging from the satisfactory operation of similar systems in other classes of work, no trouble is to be anticipated from the carrying, over of oil in suspension into the cylinders. Respecting the method of expelling the exhaust from the cylinder, the greater volume will naturally be ejected through the auxiliary exhaust formed by a number of small holes opening into an extension, of the water jacket, at the bottom of the cylinder, while the exhaust valve fitted in the head, opening later, will release the remainder. But it would seem to be preferable for the gases emitted through the latter to pass through an aperture in the side of the valve cage rather than over the valve spring as at present, since they may be at a sufficiently high temperature to affect the spring detrimentally. The engine has flat seated valves and a non-stop carburettor. The cylinders are mounted exactly opposite each other so that in order to avoid the use of offset or forked connecting rods, one piston of each pair has two rods attaching it to the crank shaft. (To be continued.) ® ® ® ® NOTES ON PAPER GLIDEjR EXPERIMENTS. By G. H. KILSHAW. [This contribution has been awarded the first FLIGHT Certificate of Merit. See pages 12 and 13.] PART II.—Nose-Diving and Design. CONTINUATION of the previous experiments on stability, and the diving tendency during some of the tests, the following is the result of experiments with paper gliders of well-known types and combinations : There may be said to be only four distinct types of aeroplane at present flown with success, mainly as follows : elevator in front type, tail behind type, elevator in front and tail behind, and the Dunne or back-swept wing type. As a result of the previous stability experiments, and my desire to keep to the dihedral and increased angle of incidence wing tips, it will be seen to be impossible to include this latter in the tests without extensive alterations, whereby changing the real characteristic of this type. The principle has, however, been combined with the three other types, and with results of no little interest. The sketches show the various gliders, a series of six. Gliders 5 and 6 had a wing span of 6 ins., and a fore and aft length of 5§ ins. Glider 7 being as 5, with the addition of an elevator in front, increasing the length to 7£ ins. Gliders 8, g and 10 are of Similar types to the above with the tall and elevators made to sweep back as the Dunne method, with span and length as the gliders 5, 6 and 7 respectively. The following table of tests and results has been made out to enable easier comparison, and the inclusion of the glides should give a clearer idea of their actions. It may be mentioned that the glides given are the best obtained :— Glider .«5. Glider.6. Glider. \&$& Test I. 0 Launched *g at angle of 450 • to left wing. W Test II. Released with wings vertical. Test III. Launched upside down. Bes': glide when launched 4 ft. high. 5 Steady glide to left of 10 ft. 6 Steady glide to left of \o\ ft. 7 Glide to left of II ft. 8 iSteady glide to left of 14 ft. 9 Steady left glide ; of 13 ft. 10 jSteady glide to left of 11 ft. Nose-dive, landed in 4 ft. Quick recovery, and glide of 7 ft. Slight dive, followed by glide of 6 ft. Slight nose-dive, then glide of 8 ft. Slight dive, and glide of 8 ft. Quick recovery, and glide of 7£ ft. Sharp dive landed in 3 ft. Quick recovery, and glide of 9 ft. Slight nose-dive and good glide of 11 Jft. Excellent recovery, and glide of 13J ft. Quick recovery, and glide of 10 ft. Smart recovery, and glide of 9 ft. 12 ft. 13 ft. 12 ft. 16 ft. 154 ft. 14 ft. Prior to a study of the results, I should like to add that, before sufficient satisfaction was obtained to proceed to record their actions, three sets of gliders were tried. The last were given dihedral angles of about 10°, and incidence angles of 5° at their wing tips, while the tails of 8 and 10 were set back to form an angle of 500, and the elevators of 9 and 10 to an angle of 6o°. The elevators of those so fitted were given a slightly larger angle of incidence than the wing tips, tail planes being left flat with the bodies, giving the machines a stable fore and aft vee. Test III, although severe, perhaps, is a position in which a full- size machine may, and has been in, through being overturned, and it is only by instituting such that the reliability of design may be thoroughly tested. All but glider 5 did fairly well in this test, only a very slight dive being discernible in glider 7. The general action being a down and under movement until righted and then a glide in direction reverse to that launched. While showing an improvement when as a tail plane, the back swept plane seemed not as good when fitted as an elevator, com paring gliders 6 and 9, Test II. This may be caused by the action of the air flowing back along these surfaces and under the main plane, and probably increased speed that happens during a nose dive increasing this to such an extent that the resulting lift on the main plane being magnified in excess of that on the elevator, the centre of pressure moving back, causing the front to dive. The ordinary type of elevator in front seems to decrease the nose-dive as the results of gliders 6 and 7 seem to indicate. The gliding angles of the gliders 8, 9, and 10, especially 8, were improved after the addition of the back-set planes, and the marked improvement of the fore and aft stability of glider 8 over 5 gives good illustration of the fine steadying effect of this type of design. The outstanding excellence of the loaded elevator in front over the non-lifting tail behind is interesting, glider 6 giving the best results, followed closely by glider 10. Before closing this article, I should like to state that each glider was tested at least six times in each test to ensure accuracy, which is necessary in a research of this nature. 48
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