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Aviation History
1944
1944 - 1914.PDF
294 FLIGHT SEPTEMBER 14TH, 1944 Floating on Rubber The New Qoodyear Engine Mounting : First Application to Flying Fortresses THERE is, of course, nothing new in the use of .rubber mountings for aircraft engines, but the Goodyear company of Akron, Ohio, has brought out a type of mounting which is claimed to'represent an advance on any previously used. Goodyear research scientists made a very thorough mathematical analysis of the causes of vibration before attempting to devise means for meeting them. There are many unbalanced forces in an engine which cause vibrations, and which cannot be eliminated, but which can be absorbed so that the vibrations are not transferred to the supporting structure. For the first development the mounting ring of a Fortress engine was chosen. The radial engine offers special problems because it is mounted from a ring at the back, and thus the mass has to be supported a considerable distance behind the centre of gravity. A number of the Goodyear rubber mounts are used for attaching the engine to the tubular mounting ring. Each mount consists of two main parts. There is a collar lined with a rubber bush. This collar is attached to lugs welded to the ring. It has a socket which is at right angles to the collar itself. The other half of the mount, a small unit attached to the engine, terminates in a ball which fits into this socket. Vibrations are isolated by the ball-and-socket pint and by the rubber bushing in the collar. The bushing is of special design, and the whole mount gives freedom of motion for every mode of vibration that can occur. It permits limited rotation around the crankshaft and about the axes at right angles to the crankshaft, as well as linear motion at right angles to ;the crankshaft. The Goodyear rubber mounting shown at the top of the page comprises a rubber-bushed collar and a ball-and- socket joint. On the left the engine, complete with a number of these rubber mounts, has been installed in a Fortress. The picture above shows one of the engines of the Goodyear Navy airship M-l to which Lord Ventry referred in his article last week. The airscrew is a Curtiss electric in which the pitch can be reversed so as to use the airscrew as an air brake. This is particularly useful when approaching a mooring mast. Apart from its use for checking speed, the variable-pitch airscrew enables a saving of fuel to be made, since the pitch can be set to give best efficiency at all speeds. $ At take-off the low-pitch setting gives maximum thrust and increases the weight at which the airship can get off by adding dynamic lift to the static lift of the gas.
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