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Aviation History
1912
1912 - 1153.PDF
5oz DECEMBER 7, 1912. added the winding-up gear made out of some old clock works • this is not only easier but quicker, as one turn of the handle gives six to the propeller, and after winding up, the screw is held up by a loop of string, and the bracket with winding- gear attached slipped off the end of the frame. The time it took the elastic motor to run down was taken by a watch held in the hand. The self-registering arrangement was added lat.-r. This consists of a chum driven by a motor; the drum is made 2§ in. diametct, or i\ in. in circumference, and is made to revolve once in a minute, so that \ in. is equal to 1 second of time, the paper on which the diagrams are recorded being ruled as per enclosed sample. The motor is made of clockwork, the spring being removed and a drum fixed in its place to drive by a weight in order to give constant and even motion. A catch for starting and stopping was also arranged as shown. An arm carrying a pencil conveys the thrust of the screw—from the index lever with spring attached— to the paper on the drum. The pencil works in a slot formed by two parallel bars so as to prevent side movement, and a small weight (about J oz.) on the top of the pencil gives the necessary pressure. The machine is made chiefly of wood, with small brass screws working in brass plates attached to the levers for [/yGHTJ see that the drum makes one revolution in a minute; then wind up the propeller the desired number of revolutions, slip the cord over one of the blades, and remove the bracket with winding-up gear attached so as to be out of the wa>. Wind up the motor, see that the loose arm is close up to the one with spring attached, and all is ready. Start the motor driving the drum (by pulling down the weight shown for that purpose, which releases a catch), pull the cord until the propeller is released, note the tune it takes to run down, by a watch, and compare it with the time shown on the diagram, also note where the finger has been pushed to, showing maxi- ... 1 ._,±„ !•-• . 1 1 ' I ,. 1 \ ' 1- -f u-1 1 —— v'' ""\ . T>ri __.-' -I — - II SEC C 14- SCC 10 sec B bearings ; and all is made to work as easily as possible. mum thrust< Each experiment should be numbered and all the particulars put down in a tabulated form with dimensions of the propeller attached. The diagram will show how the thrust decreases as the propeller runs down. DIAGRAM FOR FINDING THE PITCH OF SCRE.W PROPF 1 LEHL) rr<ow 0»MvitTrR «nri ANGU AT TIP Of BLADT DIAMS O The motor can be slipped off the end of the frame and the drum lifted off to fix the paper if necessary. Having fixed a paper on the drum, so that the pencil co incides with the zero line. Before commencing the tests I The accompanying diagram was taken and corresponds with the following particulars :— In order to find the pitch of a propeller, it is necessary to multiply the circumference of the circle described by the IH53
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