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Aviation History
1914
1914 - 1128.PDF
opposite direction and the pointer is turned back until the speed again becomes constant. It will be obvious that such an arrangement as that described will IJC affected by any lilt of the machine. In order to obviate this, a vertical guide is provided carrying a weight equal to that of the sliding weight and mounted on a spring ot suitable strength. This weight is connected by means of small levers (as in the sketch) to another small wheel equal in diameter to the other previously mentioned and also mounted on a squared shaft so as to be able to slide in contact with the lower surface of the time disc. The two squared shafts are connected together through a differential gear. The ins rument will be unaffected by tilt, the sliding of the lower wheel being provided by the excess force of the spring when the inMrument is on a slope. The arrangement here described is that of the original patent specification, and would give a reading of the velocity in the direction in which the machine is travelling. I may perhaps say that a later development which I have designed would give the machine's horizon talspeed relativetto the earth, and this, of course, is the quantity most desired. At present only uncompensated (for slope) models have been constructed for experimental purposes, and these, in spite of mechanical defects, have given quite reasonably accuiate readings on the level railway line bttween here and London. Tne instrument has been placed on the seat of a railway carriage. It has also been used in a taxi with frequent stops in the crowded streets in the City. The difficulties at present encountered are purely mechanical one*, while at the same time the inevitable expense associated with models of this sort makes development a slow process. The other patent specification deals with an instrument designed for the purpose of showing an aviator on a map his exact position over the ground. This instrument depends primarily for its action on two pieces of mechanism (l) that for obtaining the speed of the machine hori zontally; (2) that for obtaining the direction of the machine. The first of ihese is derived from the speedometer just described, and the second from a form of magnetic or gyrostatic compass which, by means of delicate mechanical or electrical relay mechanism, enables a rotation of an arm to take place through an angle equal to that of the change of direction. It will be needless to describe this relay mechanism here, as details of it can be obtained from the patent specification, and I propose here only to outline the principles of the action of the instrument. Two friction discs are driven from the tame shaft by means of mechanism controlled by the speedo meter at a speed always proportional to the* speed of the machine. These are mounted with their faces parallel, and between them are arranged in different planes two square guides at right angles to one another, each of them being capable of rotation about its own axis. Along these guides two small wheels in frictional contact with the discs are arranged to move, and the bearings of these wheels are conn ected by means of rods in a straight line to a point on another disc whose axis coincides with that of the friction disc. This disc is actuated by means of the relay mechanism of the compass previously noted. The total length of arm between the two small friction wheels is equal to twice the distance of their point of attach ment from the centre of this disc. In the figure, R represents the point of attachment, O the centre, P and Q the small wheels. OR = RP = RO. Suppose that 0(J coincides with the magnetic north, and OR is arranged under these conditions to lie along OQ. If the machine is turned through an angle 0, ROtJ becomes = 0, and OP and OQ are proportional to sin 9 and cos 6. Again, since P and Q are turned by a disc whose rate is proportional to the speed, V, of the machine, the actual rates of turning of P and Q are proportional to V sin 6 and V cos fl, and P and Q will turn the shafts on which they slide at these rates. These shafts are in turn connected in one form with the instru ment, one to rollers carrying a map and the other to a device for causing a transparent strip of celluloid ruled with a line along its length. The cover of the map case consists of a sheet of trans parent material ruled with a line across its centre at right angles to the line on the celluloid strip. The map moves in one direction with a velocity proportional to V sin 6, while the strip carrying the line moves in a direction at right angles to this with a velocity pro portional to V cos 0. It is evident that the apparent motion of the point of intersection of the two lines over the map will have a velocity compounded of these two velocities, i.e., Vin the direction 9 with the magnetic north, and thus will trace out the path of the machine over the earth on the map. There are, of course, obvious criticisms. The principal one, I imagine, would be the difficulty due to magnetic variations. I have calculated the difference that this would make under extreme conditions, e.g., flying over England from east to we>t, and I think it will be found that under present conditions of speed of flight, &c, the error would amount to 3 or 4 miles per 100. This would be almost entirely obviated by using a gyrostatic compass, though I am doubtful if in their present state of development these are sufficiently reliable. The latter instrument is at present only par ially constructed. I may add that a German patent (which, I believe, has been sold to the German Government, and is in use on the Zeppelins) on the same subject has been filed in England, but I think I may say that the design of n.y instrument is far simpler, and does not encroach on the other patent at all, proceeding, as it does, on different lines. I Ehould be willing to give any other inlormation on these instruments to interested persons. I think, however, that a periwal of the patent specifications will help to ckar up any points I may not have been sufficiently lucid about. The College, Epsom. CHRISTOPHER W. C. WHEATLEY. The " Lang" Pitchfinder. [1888] The following history of the Pitchfinder, illustrated on page 1103 of last week's FLIGHT, may be of interest. This wai invented by the late E. V. B. Fisher in Tune, 1909, and was used by Mr. A. V. Roe's staff to set the pitch on the adjustable propellers which were used on the 9 h.p. Avro triplane which made several successful flights on the Lea Marshes in July, 1909. In 1910 Mr. Fisher patented the device, and it was exhibited at the Olympia Aero Exhibition on the stand that Mr. J. V. Neale shared with the Motor Accessories Co. At this time the pitch finder was made of black vulcanite, with a pendulum instead of a level. In the following year Mr. Fisher altered it to the form shown in last week's FLIGHT, page 1103, and it was again exhibited, but I do not remember on which stand. It was described and I believe illustrated in some of the Press reports of the exhibitions. L. HOWARD FLANDERS. Bexley Heath, Kent, November 10th, ® ® ® ® Aeronautical Patents Published. Applied tor In IBIS. Published N(n<ember $tk, 1914. 22,239. — TREACHER. Floats for hydro-aeroplanes, seaplanes, &c. Published November \ith, 19H. 2r,2i2. M. P. OTTO. Apparatus for manoeuvring at a distance marine or aerial torpedoes. 27,263. R. A. CHALMERS. Launching aeroplanes and hydro-aeroplanes. Applied for In IU14. Published NoT'ember 12M, 1914. 5865. J. C. HANSEN-ELLBHAMMER. Frames for motors with cylinders dis posed in star formation. 12,043. E. E. PAULEY. Flying machines. FLIGHT. 44, ST. MARTIN'S LANE, LONDON, W.C. Telegraphic address: Truditur, London. Telephone: 1828 Gerrard. SUBSCRIPTION RATES. FLIGHT will be forwarded, post free, at the following rates:— UNITED KINGDOM. ABROAD. s. d. s. d. 3 Months, Post Free._ 3 9 3 Months, Post Free— 5 o 6 „ „ ._ 7 6 i 6 „ „ .- 10 o 12 „ H ••• *5 o | 12 „ 20 o Cheques and Post Office Orders should be made payable to the Proprietors of FLIGHT, 44, St. Martin's Lane, W.C., and crossed London County and Westminster Bank, otherwise no responsibility will be accepted. Should any difficulty be experienced in procuring FLIGHT from local newsvenders, intending readers can obtain each issue direct from the Publishing Office, by forwarding remittance as aiovt. 1128
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